Frequently Asked Questions About Flexo And Digital Printing
What Should I Use To Clean My Anilox Rollers
What should I use to clean my anilox rollers? – This depends a great deal on the ink/coating system you are using such as water, solvent or UV .
Each chemistry to some extent requires a unique solution for optimum results.
Care should also be taken to ensure that the cleaning product will not attack soft metals as
many cylinders can have an aluminum core that can and will be attacked by some products.
What should I use to clean my anilox sleeves?
What should i use to clean my anilox sleeves depends a great deal on the ink/coating system you are using such as water, solvent or UV .
Each chemistry to some extent requires a unique solution for optimum results.
Care should also be taken to ensure that the cleaning product will not attack soft metals as many sleeves have aluminum shell that can and will be attacked by some products.
We offer a wide range of concentrates for mechanical and manual cleaning. Eliminator, Rejvinator, Deep Cleen and Real Cleen.
Anilox solutions- there are many options in todays market place and for this reason we recommend you
give us a call to discuss the best product to suit your needs.
Off the shelf store products and solutions that you might have lying around your facility
are not always the best choice and in some cases can actually be detrimental to the surface
you are trying to clean, the operator and the environment.
What are the Best solutions for cleaning anilox?
Best solutions for cleaning anilox- The best solution to clean your anilox is one of our ultrasonic systems but that is not always an option.
The next best is to manually clean your anilox on a regular or as needed basis using one of our anilox restoration products.
Our two most popular products Eliminator & Rejuvenator are great for removing staining,camouflaging,banding.
Applying the products with one of our Erazor sponges greatly enhances the process.
Is ultrasonic cleaning safe?
Is ultrasonic cleaning safe- The answer is yes and no. Yes if you are using one of our state of the art Caresonic systems and no
if you are using systems with only single or dual frequency. These systems can create harmonics which in turn can create hot spots
in the cleaning tank and if your anilox if exposed to this technology for more than a few minutes can lead to cell wall damage.
This is not the case with our Caresonic technology which uses frequency sweep technology and by rapidly alternating the frequency
eliminates any possible hot spots forming making it safe to clean any line count for extended periods of time.
Is it safe to blast my anilox?
Is it safe to blast my anilox– If you are not concerned about getting to the bottom of engraved cells on your anilox or their longevity
then blasting is an option. Clearly this is said in jest as everyone wants to get to the bottom of the engraved cell and wants to extend
the life of their anilox. Blast systems while still in use if used incorrectly can and will damage your anilox and at higher line counts cannot reach
the bottom of the engraved cells. It is impossible for a blast type system to clean product from within the porosity of the ceramic coating
so should only ever be seen as a superficial and not a deep cleaning process.
How do I remove staining from my anilox?
How do I remove staining from my anilox– The easiest way is by using one of our Caresonic ultrasonic cleaning systems but for everyday manual cleaning we recommend
our Eliminator or Rejuvenator products that are excellent fro restoring your anilox. They are applied using one of our erazor sponges and if used in combination
have been proven over many years to be effective in removing not just staining , reticulation marking , water marks, camouflaging and banding.
What maintenance do I need to carry out with our air mandrels and how can we better look after them?
Air mandrels are a key component in almost every print shop that are using sleeved anilox or sleeved plate cylinders. It is critical to keep the surface of the mandrel as blemish free as possible. It is well worth investing in having your mandrels manufactured with a hardened chrome finish to help resist scratching and cut marks during their life time of use. If you notice any burrs caused by knife cuts great care must be taken to remove the raised material without removing any of the surrounding area. Always use dry , oil free air as any water will cause internal corrosion within the cylinder which in turn can bleed out through the air holes onto the surface of the mandrel and hence under the sleeve. This can lead to difficulty removing the sleeve and in turn can lead to further damage to the surface of the mandrel. Air holes should be checked for plugging and cleaned out periodically. They should always be stored with protective covers and ideally in their original wooden crate that they were supplied in for maximum protection. Remember unless the air is piped with individual pipes to each air hole and is pumped directly into the hollow tube it is in effect a pressure vessel so always buy your mandrels from a reputable manufacturer that can supply you with pressure test certificates for each roll. A light coating of silicone can be applied to the surface from time to time to help the sleeve slide on more readily. Never use more air pressure than is necessary or recommended by the manufacturer. Check the headers of the cylinders from time to time to check that there has been no movement away from the metal core. There have been many documented cases of journal and headers becoming loose and even blowing out of the cylinder body due to poor construction or excessive air pressure being applied from gas bottles which should never be used unless they have gas regulators that are lockable. Always wipe clean and dry the surface of each mandrel after every use and check for nicks and dings before storing or using again. Try not to allow ink or other solutions get inside the sleeve during use as this may cause scratching to the mandrel surface and again make removal of the sleeve very difficult. Only buy mandrels from certified manufacturers and always be careful if considering using existing print cylinders to convert to air mandrels as they may not have an adequate wall thickness, header depth or be welded together as is necessary where pressurized integral rolls are used.
I was very interested in your article concerning the handling and storage of engraved and coated rolls, but what about sleeved anilox technology?
You are very right to bring this subject up as this is a major challenge for every converter and engraver alike and is creating more cause for concern as this product ages.
We need to firstly consider the construction of the anilox sleeve that is available today.
Sleeves generally consist of a fiberglass or carbon fiber inner sleeve, this has a compressible layer applied to it, with a final outer steel or aluminum sleeve that will be ceramic coated prior to being laser engraved. Most anilox sleeves are slid onto an air mandrel that has holes drilled through the steel core on one end and one or two in the middle. Any air that s applied to the mandrel must be kept oil and water free as this may cause internal corrosion of the mandrel which in turn will contaminate its outer surface and the inside of the sleeve as well.
The sandwich construction in itself makes the likelihood of one or more of these inter-layered surfaces failing highly probable, particularly if subjected to any form of impact.
So rule number one do not drop the sleeve, either on its face or any part of the edge of the sleeve. Dropping a sleeve will not only cause failure between the layer construction, but can deform the sleeve that it will cause it to loose its roundness/concentricity. This would prevent the sleeve being slide onto any air mandrel if the inner sleeve is deformed in any way and need only be affected by a few thousandths of an inch.
More often than not it will cause failure of the bond between the metal core and the ceramic engraved coating which will render the sleeve immediately unusable and will require full recoating and engraving of the sleeve.
The outer edge of the sleeve is actually its weakest point and again usually results in fracturing or lose of the outer ceramic coating, it can also cause the inter- layers to separate and may allow ingress of the inks, coatings, solvents or water into and between the layers. This will cause complete failure of the bonding between the different layers and at best will result in eccentric and concentric issues. It is possible to glue any splits on the ends of the sleeve that you may see and although not a permanent fix will slow the complete failure time don some.
Manufacturers have started to add an extra metal end ring on both sides of the sleeve to try to give the sleeve extra strength and protection, but of course the best protection is to protect the sleeve edge by not dropping it in the first place. It is recommended that when removing a sleeve that you place a rubber mat on the floor that you intend to stand it up on during sleeve changeovers or better still use an appropriately designed device that the sleeve can slide onto that also has suitable cushioning to protect the edge of the sleeve.
In terms of cleaning the anilox sleeve great care needs o be taken to ensure that minimal pressure is applied to the ceramic surface coating as excessive pressure may cause the coating to crack or lift or may worsen an already damaged coating caused through normal on press wear and tear.
If liquid mechanical cleaning is carried out great care must be taken to ensure that no water or cleaning solution can get between the layers by migration into them via the ends of the sleeves.
The inside of the sleeve and outside of the air mandrel must be kept free of any dried ink or other coating at all times as this can make removal or installation of the sleeve onto the mandrel difficult to near impossible. In addition great care must be taken not to score either inside of the fiberglass sleeve as this may eventually cause the sleeve to split. Equally any scoring of the air mandrel surface may cause difficulty when trying to slide the sleeve onto it or take it off and may add to the scoring of the inside of the sleeve itself. Any score marks that are noticed must be polished down immediately that they are noticed and should be part of the inspection of the mandrel surface before attempting to slide any sleeve onto it.
All sleeve manufacturers’ have strict guidelines as to what air pressure to use when mounting and demounting any sleeve and must not be ignored. Excessively high air pressure can cause the sleeve to split and may exceed the guidelines for the air mandrel itself that could cause it to explode. In case you might think that this is impossible I have actually witnessed this happen, so take heed.
When presenting the sleeve to the mandrel it should be kept as parallel as possible and not rocked back and to onto the mandrel if at all possible because this can cause splitting of the end of the sleeve.
Engraved sleeves should preferably be stored upright with adequate protection wrapped around the outside or stored in tubes or boxes with suitable end supports that will prevent it from being knocked during the storage or retrieval process.
One final point that is often overlooked is to check the dynamic balance of the air mandrel that the sleeve is mounted onto.
Improperly balanced mandrels can lead to significant vibration and harmonic issues which in turn can cause sleeves to fail prematurely and certainly will not allow the anilox surface to transfer a uniform thickness of ink or coating to the printing plate.
It can even cause premature wear to the printing plate and doctor blade so it is well worth the trouble to check it out.
Based on the length of the article hopefully you will understand why I did not include it in the care and handling of anilox rollers.
If I have failed to answer all of your questions please do not hesitate to write and let us know.
What is more critical in terms of line count and volume when related to an anilox engraving?
This is a very common question and one that deserves more comment on in view of its affect on your final print quality and perhaps just as important your ink or coating usage.
Let’s start with the basic principle of what you are trying to achieve firstly with ink. In most cases you are trying to achieve a given density and uniformity of color and thickness that will enable you to run at an acceptable speed.
With most coatings, adhesives, lacquers, cold & heat seals you are normally looking to achieve a particular coat weight and thickness.
The individual anilox cell therefore must be able to carry a given volume of ink or coating and collectively be able to transfer just enough to the surface of the printing plate.
When transferred to the substrate it should them result in an appearance, thickness, coat weight, color and density to suit the specified or desired result.
This all sounds very complex and can be very daunting but the factor that impacts the finished result in relation to the anilox is the volume.
It is so critical that I have frequently used the phrase” volume is sanity, line count is vanity”, when trying to help printers make their choice of engraving.
Yes line count is important in terms of uniformity of laydown, dot size and graphical definition, but without the correct volume you cannot achieve any or all of the other factors.
With modern engraving technology there is a push towards higher and higher line counts which does allow thinner coating/ink thicknesses, coat weights and press speeds to be achieved which is great but there is a hidden cost in terms of longevity of the anilox, degree of time needed to keep the cells clean, scoring and general premature breakdown of the cell walls due to the relatively thin cell walls of the cells.
There is no doubt that you need to think of line count very carefully when dot size, plate screen line count and graphic definition are key components of any design but do bear in mind if the anilox cell is not capable of carrying the volume of ink or coating that is necessary, consistently revolution after revolution then the line count becomes a lesser factor.
Can you please describe the various options available for measuring anilox cell volumes , from a printers perspective.
Being able to determine with some accuracy the theoretical volume of a given anilox cell is an area that challenges printers and engravers alike. From a printers perspective what you really want to know is if the anilox you are about to use is capable of providing a sufficient volume of ink to the printing plate that is uniform from side to side and around the full printing plate circumference. You may have noticed that I used the term ”theoretical volume” which you might think strange and more to the point unacceptable when you what some guarantee of what cell is capable of carrying. From this perspective knowing what a cell can hold is relatively easy to calculate, knowing what will finally be transferred from the cell and ultimately from the plate surface to the substrate is an entirely different element hence the term” theoretical volume”. How to measure a cell volume consistently, accurately and affordably as a printer are other key considerations. To begin with the use of pocket illuminated scopes or more expensive gravure scopes work well in a print environment but will only help you to determine if a cell is plugged and needs cleaning. That said from a day to day to use or not to use these tools are invaluable and should be made readily available for all operators and are easy to use with minimal training. For more meaningful volumetric measurements printers have used liquid ink measurement as one method where a known amount of ink is spread onto the anilox surface from a pipette and then drawn down around across the face of the roll with a small spatula or blade. A rubbing is then taken of the ink blot and the surface area of the ink is calculated before being converted into a volume. This method is very dependent on the skill of the operator, the age of the ink, room temperature and while these can be considerable variables it has been proven to give a reasonable prediction of the likely volume of an area of cells on a given anilox. A more modern method uses a known amount of ink that is encapsulated in a plastic bubble which when placed against the surface of an anilox will give a volume reading against a printed scale in either metric or imperial measurements. Neither method however will give a line count and both can be as much as +/- 10-15% dependent mostly on the operator skill and other variables mentioned. Another technique used by many printers that do not need an instant result is the use of foil impression tapes where a rubbing is taken of the anilox surface and then given to their engraver who will carry out an analysis of the rubbing using a interferometer. These devices use optical laser scanners linked to computers and software programs that will compute the cell shapes , depths, openings and output a volume and line count with remarkable accuracy. This said other than the line count the actual final volume still depends on the many variables in the process such as the cell shape, coating porosity, ink viscosity, surface tension between anilox, plate, substrate, pH of the ink, ink type , doctoring system –blade or rubber roll. I could go on but I think you probably get the reason why volume is generally called “theoretical. In addition the interferometers although now more affordable are still several thousand dollars and need to be handled carefully , by well-trained operators . Personally I think as a printer you still need to rely on the expertise of your engraver and work hard to have a good roll cleaning practice in-house to minimize the plugging of the cells to maintain your volumes. Being able to measure the loss of volume or otherwise is critical but trying to prevent the loss of volume in the first place is where your focus really needs to be.
Why does my anilox not transfer the exact volume of ink that the manufacturer states on the roll or inspection report?
Although it is not often clearly stated all anilox volumes are given as a theoretical volume as there are so many variables that can and will affect the final volume of ink or coating that is released from each cell. The volume that you will be given by all manufacturers is a mathematical calculation based on the cell opening, depth and base of the cell and is usually an average of a group of cells, the exact number of which depends on the method of measurement and equipment used. Now this number will be quite accurate but as mentioned it is the other variables on press that really affect the final volume of ink or coating that will be transferred. For most modern ceramic anilox this can be as much as 85% or more but due to the surface energy between the anilox, metering roll, printing plate and finally the substrate the final amount will and does vary. This variance can be quite dramatic particularly when a ink metering roll is used which can actually lead to a greater amount of ink being transferred than has been quoted due to the hydraulic forces between the anilox and metering roll and the limited ability to sheer the excess ink or coating from the surface of the anilox. In some instances where extra coat weight or density is desirable this can be beneficial but if you are wanting to maintain consistent densities and coat weights then a doctor blade is always going to give you more consistent results and better volume control. The actual chemistry, viscosity, temperature, substrate, plate material, press speed, drying system also all have a bearing on how much volume can and will be transferred. Finally, how well you keep your anilox clean will also have a dramatic affect on any anilox cell’s volume carrying capacity which is why good house keeping and cleaning of the anilox is so vital from day one that you put it on the press. The use of the right cleaning solutions, stainless brushes (for ceramic) and cleaning systems such as ultrasonic’s are all essential if you want to sustain any anilox’s volume carrying capabilities. Of course if you change any of the other factors previously mentioned the volume transfer will change as well so maintaining good records and being aware of these variables is vital if you want to get the maximum ink or coating to be released from each engraved cell.
What is the simplist method of determining the right anilox line count and volume to suit our needs, without the need for us to read an entire book about it?
It is true that you could write an entire book about the many factors that can and should influence your choice of anilox line count and volume to suit your needs. Having said that I understand how confusing it can be for many printers and how essential it is to make the right decision reading this key factor on any press. The first thing I usually say to most printers is that it really is not rocket science .Yes there is a science to it and it can be a very complex subject if you happen to have a degree in graphic technology, but in the everyday world of Flexography few people have the formal training in our process that would be necessary for the average person to understand the absolute intricacies of the selection process. The simplest way of making the right choice of line count and volume is to choose the vendor that has the personnel with enough knowledge of the entire process, and not just based on how cheap they are. They will be able to advise what would be best for you, but they will first need some basic information, so the following are some key factors that you should be able to provide your vendor that will allow them to help you make the right line count and volume selection to suit your specific needs.
- What graphics are you intending to print i.e.: solid only, solid & line, line & tints, screens, process print.
- What line counts will your tints or process screens be?
- What will be the minimum dot size?
- What pigment concentration will your inks have?
- What viscosity will your inks be running at?
- What ink system will you be using i.e.: water, solvent UV?
- What substrate will you be printing on in particular is it absorbent or non-absorbent?
- What coating thickness and coat weight will you require?
- Will you be running with a trailing or reverse angle blade?
- Will you be using a rubber metering roll?
- What speeds will you be running at?
- What plates are you running with rubber or photopolymer?
- What line count and volumes are your existing anilox?
Sounds like a lot of questions I know but unfortunately this is the minimum of information that needs to be considered. This also assumes that you will have already carried out a finger print of your press or presses to help to determine the sort of dot gain and other capabilities and limitations that your equipment and existing tooling may have. Unless you are buying your first press and do not already have any anilox you need to be cautious about making radical changes to your anilox line count and volumes as this may also require a drastic change to your ink chemistries and prepress allowances.
Are all ultrasonic cleaning systems the same, and are they safe and effective in cleaning anilox rolls?
The answer is no they are not all the same and yes they can be effective in cleaning your anilox rolls. Conventional ultrasonic systems unfortunately can cause hot or dead spots known as nodes and anti-nodes. This occur when sound waves generated at the transducers, travel to the top of the liquid and on returning collide with the next wave. This creates a hot spot of cavitation below and above which there is formed less cavitation-a dead spot. It is these hot/dead spots that can be potentially harmful to engraved rolls. Fortunately a European manufacturer has overcome this issue with the development of a frequency sweep technology that modulates the frequency 100 times per second which allows for cleaning of all engravings safely and efficiently. This technology makes the cavitation process uniform throughout the liquid which ensures a consistent clean to all sizes of rolls and engravings. You should also ensure that the cleaning solution added to the water is not to caustic as this can cause potential blistering of the anilox base. Using the frequency sweep technology allows for much milder solutions to be used that are safe for the environment, the product and the operator as they are bio degradable. The less safe conventional systems depend on very caustic cleaning additives which are environmentally unsafe and dangerous to both the operator and the product.
We hear so much about best practice being necessary for good quality print but how do we define what is best practice?
This is a very big subject but for me best practice is about eliminating as many variables as possible on and around the press. You need to look at each aspect of the print process and determine what you believe to be the most effective in helping you to achieve consistent results. This usually starts by measuring and recording what is being done to help to determine if it is repeatable and if the results are acceptable. Generally the use of measuring devices such as spectrophotometers, densitometers, video web inspection, interferometers, viscometers are necessary to help capture the necessary data in an accurate form that can then be repeated and measured accurately each time a job is run. Always try to get your suppliers involved at the earliest stage possible as they will then be able to assist you in achieving what is best practice for you and your company and more to the point, how to define it.
Can you describe what a peristaltic pump , how does it work, and what advantages does it have?
A peristaltic pump uses rotating rollers that turn against a flexible tubing which creates a pressurized flow of a given ink or coating. Peristaltic ink pumps are used widely in printing presses where good ink flow is essential.
How the Peristaltic Ink Pump works
Peristaltic ink pumps have a pump head, drive, and various types of flexible tubing in which the ink/coating is propelled forward with each rotation. Pump heads can have a variety & of number of rollers. The tubing material and length can also vary, all depending on your requirements. The tubing is usually made of silicon or other plastic materials, all of which will have to be replaced dependent on the solution being pumped and the hours run. In general the flow rate of the ink/coating is relative to the rotation of the rollers. The flow rate also depends on the inner diameter of the tube and the viscosity of the ink/coating being pumped. Pumps can be operated manually or by a battery. Peristaltic pumps are very useful in using more viscous inks, adhesives and coatings. They are also good with sheer sensitive liquids. They can come with variable speeds which allow controlled ink/coating flow. Modern peristaltic ink pumps are equipped with inverter drive units, which allow the user to plug the pump in and control the speed as well as the direction of flow by a simple switch mechanism. Peristaltic ink pumps do not need any valves and seals which means very little maintenance is required.
Can you help me better understand the differences between CMYK, HexachromeTM and Opaltone TM color models.
Let’s start with CMYK which is the original color system that believe it or not was invented over 100 years ago.
This is a subtractive color model that is generally used in process printing. Most people use CMYK to describe the process itself and is an abbreviation of the process color inks used, that being Cyan, Magenta, Yellow and key (black).
Generally the colors are printed in the order as it is described but this can be varied dependent on the requirement of individual jobs.
This technique works by partially or entirely masking colors on a lighter background which is usually white. This in turn reduces the amount of light that will be reflected
off a printed image, other color models use just RGB , but these are additive techniques that use a combination of primary colors. Black is achieved by a combination of these colors and is generally used when deeper black tones are wanted.
This color model is still by far the most widely used method of achieving multiple colors in most markets.
Now Hexachrome TMoften referred to as the CMYKOG was introduced in 1996 and is limited by trademark, patent and is a licensed process for those wanting to use it.
Hexachome is a sophisticated enhanced version of the subtractive color model that uses much purer ink set of Cyan,yellow,magenta ,black inks, plus a very strong orange and green.
With this combination of six colors over 90% of all solid colors can be created, which is almost twice as much as with the traditional 4col CMYK model.
The HexachromeTM inks also have brighteners in them which also add to cleaner colors being achieved, which in turn helps to produce a much larger color gamut that is close to a RBG model.
This system is quite complex and needs RIP systems that can handle these colors and will and is challenging for those new to this technology.
Well if 6 colors are good then 7 colors should be even better ,which is the claim for the OpaltoneTM color model. This technology uses standard CMYK process inks, plus unique OpaltoneTM red, green and blue additive primaries.
With these colors it is possible to create over 2880 digital hues that produce very vibrant color and density.
Thus the need for a black ink is completely eliminated with black being produced using RGB that saves on a lot of make ready and generally gives improved gray balance and richer shadows.
Again this system is trademarked and licensed, of course you need to remember you need up to seven color stations if you want to take advantage of this system although to be fair many jobs can be printed with just six colors due to its wide color gamut range.
Again you will need compatible worklow systems with appropriate software to handle this 7 color process.
Can you please describe dot gain, what is its root cause and what is its general impact on print quality?
Dot gain is generally understood as the actual growth of a dot both physically and by what can be measured optically by using a microscope. In simpler terms it is the difference in dot size from what was output on a film or digitally to your plate to what finally appears on the printed substrate. Densitometers actually measure both the physical and optical change in the dot to calculate its theoretical final size. There are many variables that affect dot gain from the actual ink system, plate durometer, thickness, ink film thickness, sticky back, plate to substrate impression, anilox to plate impression, ink metering system. With new digital to plate technology dot gain can be compensated for greatly thanks to the ability of being able to produce dots of 1 thou or less. In terms of print quality dot gain is generally undesirable particularly in high light areas and when trying to produce vignettes. While it is mostly commented on in relation to the size or growth of an individual screened dot the same effect occurs with text and line images which can cause fill in and general blurring of the final finished graphic. With a flexible plate generally the thicker the plate the more dot gain is generally seen and the same can be said for plates that are produced using traditional negatives. New digital software , thinner plates , improved sticky back and laser output devices are doing a great deal in reducing this issue but it is still dependent on the press and its operator to achieve a minimal impression set to achieve the least possible dot gain.
What is anilox cell volume?
Cell volume is a critical component of the ink delivery equation. Having a repeatable and reproducible volume measurements provides valuable information to press operators, who can use that information to streamline make-readies. Unfortunately, measurement readings taken by various roll suppliers using different quality verification methods do not necessarily provide the accuracy and consistency printers need, an issue made glaringly obvious by the Troika study.
Kudos to Troika for taking the initiative to conduct the banded roll measurement trials with suppliers on multiple continents. Kudos as well to the FTA’s Flexo Quality Consortium for taking on the issue of industry-wide standardization of measurement techniques.
Clearly, some methods produce more accurate and repeatable results than others. There are, of course, other factors to consider, especially for individual printers who have purchased or are considering purchase of systems for internal verification and periodic spot-checks of their roll inventory. Cost, robustness of the system to stand up to use in the a production environment, vendor support and training, availability of replacement parts, sensitivity to vibration, ease of use and ease of calibration are just a few. Yes, ideally, every anilox manufacturer would use the same methodology, which would vastly improve consistency from roll to roll and manufacturer to manufacturer.
However, there is not a one-size solution that fits every circumstance. As Paul pointed out, impression tape provides a mirror image of the cells, which is portable and can be photographed and measured as though it was the actual roll surface, but in a dirt and vibration-free laboratory environment. Although not as repeatable as measuring the roll itself, use of impression tape greatly reduces potential for damage to expensive measurement systems in field use or transit. If, (for whatever reason), it is not practical to have a particular system in your facility, consider having roll audits conducted by your roll supplier using impression tape. This can be an excellent alternative to extract some extremely beneficial information about the condition of your roll inventory.
If you already have an in-house measurement system, be sure to review the Flexo articles highlighting the FQC’s findings so you know if you are comparing apples to apples or apples to orangutans.
We appear to use a whole range of chemical cleaners in and around our press room .What solutions should we be using or not using particularly on our anilox rolls and is there anything else we can use to help assist the cleaning of them?
Chemical cleaning solutions have been and are commonly used in our industry on a daily basis. The problem is with many cleaning solutions that are deemed to be effective is that they are very caustic and as a result are not environmentally friendly, are a danger to the operator and can even cause blistering of your anilox roll. EPA and OSHA standards vary dramatically by state and should be carefully followed to ensure that your company is in compliance. Having copies of the MSDS sheets for each solution and fully understanding the solution components will help ensure you are in compliance and that they are safe for your operator and product as well as the environment. Many solutions can have a very bad reaction with your inks so it is even worth talking to your ink vendor if you intend to try a new solution. All ceramic coatings have some porosity so you need to be careful with any solutions that may be very acidic or alkaline as they can and will attack the metal base; aluminum is particularly susceptible to attack by such products. If you are manually cleaning your ceramic anilox you can use stainless steel brushes to help break down any dried ink deposits. While blast systems have been popular ultrasonic cleaning technology is gaining in popularity as more environmentally friendly, nonhazardous bio degradable solutions can be used due to the action of the ultrasound more aggressive caustic solutions are not required. These systems help eliminate the need for long winded manual cleaning that inevitably results in overly aggressive solutions being used to help clean rolls out of pure frustration. So bottom line, if your solutions have a very high or low pH then you need to investigate why and look for an alternative before you either damage your rolls, endanger your operator , impact your environment or fall foul of your state regulations.
Comment on the loss of Thomas Allison Jr
This past week we lost yet another leading Flexographic innovator Tom Allison Jr. Building on his father’s invention of the first truly effective doctor blade edge finishing machine which ended over a century of hand-shaped and finished gravure doctor blades. Tom Allison Jr. continued to build on his father’s success and dramatically enhanced his company’s reputation with many doctor blade innovations making it the world’s leading authority in regard to doctor blade technology and materials. To say he will be missed by his many friends and associates really does not in any way reflect the absolute respect that everyone had for Tom and his dedication to the flexographic community. Never one to mince words, but always willing to provide advice and support to any that asked Tom’s knowledge of the Flexographic process and in particular the heart of the press, “the inking system”, was second to none. His expertise has played a large part in helping our industry achieve the consistency and quality that allows the flexographic industry to still enjoy significant growth on a global basis. He became the mentor to many like myself but never demanded anything, not even a thank you; so as he cannot say no need to thank him now, Thank you from the bottom of my heart Tom for your friendship and constant support, you will be sadly missed!
What should we consider when choosing a doctor blade?
The following has been taken from an article by Bill Warner of Allison Systems which I feel summarizes much of Tom Allison Jr’s feelings when asked the same question.
With the doctor blade being a mission critical part of the printing process, purchase the best quality and most appropriate blade you can for your application and doctor blade related problems will be reduced or eliminated. Work with your doctor blade supplier to determine the best choice of material and profile for your doctor blades. Your blade supplier most likely has had experience with the same printing requirements, issues, and problems that you have and will have targeted guidance in the choice of blades for your application.
Regardless of the type of doctor blades you use, material quality is of utmost importance. Protect your anilox rolls and print jobs by making sure basic metal, composite, and plastic blade stock is proven in service and is purchased from a quality source and traceable by the supplier. Beyond
the choice of doctor blades, your doctor blade supplier will also likely be able to help with doctor blade usage and safety training, as well as diagnostic worn blade analysis.
About the Author: Bill Warner is a design engineer with Allison Systems Corp. He has 23 years of experience with doctor blades and custom retrofit doctor blade systems for flexographic and other printing processes.
Can you tell me what variety of materials is available for covering of corona treater rolls?
Dielectric materials as they are known come in three main types: Elasommeric, inorganics and plastics.
The choice of which is suitable for you depends on the application and of course each material has its own strengths and weaknesses.
Elastomics usually include silicone, bonded silicon and Hypalon, including some proprietary formulations. Hypalon was one of the most popular coatings but is very susceptible to pin holing and knife cuts. It is generally used on larger rolls.
Silicone is not only coated on a roll but can come in a sleeve form which makes repair of the roll much quicker and easier. This makes silicone one of the most popular dielectric coatings. Epoxy coatings have generally been used as a alternative to Hypalon as it is less likely to pinhole and has reasonable cut resistance. Ceramic coatings have become very popular due to their excellent electrical and mechanical properties and lasts longer than most other materials. Finally there is glass which is applied in several layers using a casting method but has to be applied to specially formulated carbon steel due to the high temperatures needed to fuse the glass to the base material. The finished coating is very hard and dense and has a very smooth finish.
You have explained CTP technology, but my question is more fundamental is now the right time to invest in a digital system, and does it make financial sense for the medium to small printer.
As with all new technologies choosing the right time to embrace it is a decision that every manufacturer has to make.
Jump too soon and you pay the highest price as so few are being built, plus you can be plagued with teething problems.
But leave it too late and your competitors already have an edge on you in terms of their understanding of the technology, and in the meantime stand to steal some of your customers from you if the technology can be proven to produce a better finished product, or make them more efficient.
That said the numbers seem to be showing that digital CTP systems and materials are beginning to outpace conventional systems with over 400 plus having been installed in North America.
The good news with so many being installed is that prices are beginning to become more affordable as is the material and availability.
There is some evidence that film processors and materials are also becoming scarcer which in turn will lead to higher prices.
Workflows and processing are beginning to show great improvements and efficiencies as well as consistency from job to job with a digital system.
So the answer is in most cases, yes now is the right time, but do make sure your system can be upgraded as new software becomes available making the prepress process even more automated than ever before. One last comment ITR (In the round technology) although not new and with still a long way to go to gain acceptance in North America is beginning to gain more interest and is being beta tested by several companies so there is still one large step to take before a totally digital CTP system is fully embraced, but mark my word it will become the ultimate technology for all premier flexo printers over the next decade.
We seem to always be damaging our anilox, what can we do to reduce this and is there any way of repairing the edges of the anilox without a full replacement?
Considering how long anilox have been around you would think that this topic would be long since over but unfortunately it continues to be the bane of every print shop. I will also assume that you are referring to laser engraved ceramic anilox, even though impact damage and scoring are as prevalent if not more they generally do not suffer from chipping but certainly do wear much faster. Having been involved in the manufacture of anilox in my previous career for many years I can also say that damaged anilox are the primary reason for replacement that is after plugging of the cells, but that is another conversation. Damage to anilox falls into three main categories: Impact, scoring & chipping. Impact damage is usually caused by the roll surface coming into a hard usually sharp surface or having a nut, bolt or other foreign object run through the print section. Scoring is a little more complex and although it can also be caused by contamination in the ink such as metal particles and other larger hard objects it more often comes from running blades dry, running blades out of alignment, applying to much pressure, running at the wrong angle or simply choosing the wrong material, thickness or just not changing it soon enough. Chipping generally occurs on the edge of the anilox which is the most fragile area of any ceramic anilox. It is critical if a anilox is chipped that it be filled immediately with an epoxy filler or two part filler such as JB weld as quickly after the damage has occurred. Although it will never be a permanent fix it will slow the rate of break down, help reduce further damage to the blade and leakage from the edge of the roll. If you do not repair the chip immediately it will migrate around the circumference of the entire edge of the roll making replacement the only option. One thing many printers do not take into account is where the ceramic particles go when they chip off the roll of all which is into the ink and how much these ceramic particles actually contribute to scoring of the roll face so it can have to major visible effects on the anilox and not just on the edge of the roll. In my experience if the repair is carrier out speedily and with some care the repair can hold up for several months or longer if it is monitored and perhaps even repaired again if it falls out again .
It seems that there is a digital revolution happening with a new on-demand technology being brought out every time you pick up a trade magazine, can it really compete with flexo and if so how worried should we be?
It is very true that digital printing is fast gaining ground on all print processes when it comes to short run quick turn around on demand printing. The newest technology offers roll to toll, CMYK inkjet engines with variable droplet technology. They can print on a wide range of substrates with newer ink chemistries that have excellent adhesion, density and fade resistance. With the latest systems having dieless finishing capabilities even the shortest of runs can be produced for a designer that is simply wanting to look at a design concept to a winemaker that may only have a few thousand bottles of wine to label. Variable data is even possible so that every label can be customized and with color management profiles spot color replacement is also possible. All that said to do all of this from start to finish still means very slow speeds of less than 10 feet per minute all be it of a high quality. So should we be worried, as a flexographer you may find it strange when I say not only should we not be worried but I strongly believe that we should learn to embrace it. It is a fact that for the foreseeable future runs are going to keep getting shorter and variable data is going to be demanded more and more so having a digital system either running alongside or in combination with your existing flexo system seems to me a very logical step. It is already common for many flexo presses to have in line gravure, screen ,die cutting, lamination ,embossing , so why not digital? So for small runs, variable data, multiple varieties and not wanting to have to buy a die digital complete production systems would seem to be a technology that we should at least learn to understand and where possible incorporate into our existing flexo system, that way you will have e nothing to worry about and another customer that you may be able to retain.
Do all viscosity cups have the same accuracy?
There must be more than over 50 test cups available around the world and dependent on the liquid that they are intended to measure some are more accurate than others .Traditionally our industry has favored Zahn # 2 cups, although the world standard is the DIN # 4 cup that is a true 4mm metric, and is said to have a greater degree of accuracy than the Zahn cup. The truth however is the operator habits and method of timing relative to the start and ends of flow time and failure to adequately clean the cups from one test to the next have far more dramatic effects on the results. Although viscosity measurement with a test cup is still the most popular basic procedure to measure liquid ink on the printing presses, lack of training and poor discipline continues to produce inaccurate results. In order to accurately regulate viscosity, measurements must be done with clean cups on a consistent basis along with incremental corrections to maintain viscosity, yet rarely is. For these reasons, if you want consistent results I generally recommend automated devices are used particularly for longer running jobs.
We seem to be getting ink drying on our plates more than normal and our ink supplier is telling us the ink formulation supplied is correct so what else could be causing this other than the ink?
Well assuming that your operators are not radically adjusting the ink on press and that your ink supplier is supplying the correct formulation to suit your anilox, plates and substrate you may need to look at your driers. Maintaining the right velocity, balance and direction of air between decks is critical if it is not to end up being directed onto the plate cylinder that will cause the ink to dry on the plate. Driers can become easily blocked over time with ink and substrates and dampers may be adjusted during regular maintenance and not correctly reset. You can check the velocity of the air from your driers and this should be routinely checked to ensure it complies with the manufacturer’s recommendations. You did not mention if this was common on all decks or just one or more. If it appears to be on only a few of the decks the it is almost certainly more of a mechanical issue ie dampers opened to wide, angled incorrectly, improperly balanced or some sort of blockage could be causing air to be deflected onto the cylinder or cylinders causing the premature drying of the ink on your plates. Do also double check that one or more operators are not putting additives into the ink to help speed up drying this can and will also contribute to ink drying on the plate if carried out to any excess. If this is the case you need to start with fresh ink as any sued stock may be contaminated and will continue to cause the same problem.
Can you give me some general guidelines for using dyne pens?
Dyne pens are used the world over to give a cheap and reasonably accurate treatment level of the material that you intend to print on. They can however give some very misleading or inconsistent results if the pens are used improperly and the following should help to give you more consistent results when using any type of dyne pen. Although it can depend to some degree on the type of pen and from what manufacturer most pens have a life of 6 -12 months assuming you put the caps back on them after use, so make sure you know when they were bought and when opened. If they become contaminated or have become out of date they must be replaced. Putting too much solution down by pressing too hard on the material being tested will almost always give a false reading. Try not to touch the surface that you intend to test, a dirty surface will lose its wettability .Never allow the pens to be exposed to sunlight, just as leaving the tops off , this will potentially alter the dyne readings. Each pen will have a specific dyne reading so be careful when specifying what range you think you need for your material. Try to maintain a constant pressure when drawing a line across the material to be tested. All treated surfaces are sensitive to time so be aware that the treated level when change the older the material gets and as such should be used as soon as possible after it has been treated. Always store pens at room temperature.
What is “Expanded color gamut”, and is it something that Flexo printers could benefit from or will it present even more challenges?
“ECG”, expanded color gamut utilizes a common set or six or seven process colors to create all colors on any given package including spot colors. This means that spot colors are created using screens and solid overprints to create them which present a challenge for the printer in ensuring perfect registration between each color build. For flexo the exact choice of process colors has not really been decided but generally is seen as Cyan, Magenta, Yellow, Black, Orange, Green & Violet. Of course to accommodate these extra colors you will need to modify your anilox selection by adding additional process rolls. ECG will give you very precise control over being able to predetermine what each overprint of color will create and as such make it easier to meet the designer’s expectations. There is however limitations as far as metallic and pastels when using ECG compared with conventional flexo inks. ECG presents many challenges for your prepress department in building colors and watching out for fine serif text and intaglio areas that will challenge your print operator if they are not taken into consideration when creating your color separations for our plates. ECG will enable you to create very vibrant rich clean colors but does change all of your traditional trapping rules. Generally you will use less ink with ECG ink systems as all colors are screened but does demand better housekeeping practices with your anilox and plates. To achieve the best results you must commit at least one of your presses totally to ECG , trying to switch from conventional CMYK to ECG will not only be confusing to everyone but will not allow you to achieve the quality improvement and cost savings possible with ECG technology.
Can ultrasonic cleaning damage my anilox rollers?
If the ultrasonic system is not specifically designed and proven for this application then damage may occur. The Caresonic system is specifically designed and proven over the last 20 years for the safe and efficient cleaning of laser engraved ceramic rollers. Caresonic uses a patented frequency sweep ultrasonic generator that automatically sweeps the frequency 100 times a second to prevent damage that can occur from a fixed frequency unit. With over a 1500 systems world wide Caresonic guarantee the safe cleaning of the anilox roller.
Do we need a dual frequency system for fine screen and coarse screen rollers?
No, not with the Caresonic system. This is handled automatically by the patented technology we use.
Do you have to use strong chemicals or solvents in the cleaning system?
Caresonic provide a complete process that will guarantee the performance of your cleaning system. A full range of detergents are available from to suit all requirements, all of which are biodegradable and only require mixing at 3% by volume with water regardless of your ink and coating type. Although the general purpose detergents are alkaline, because they are mixed in low concentrations the diluted product is relatively low hazard.
How often do you have to change the cleaning solutions?
This depends on usage and the amount of contamination removed. On average most printers change the solutions every 2 – 4 weeks.
How many rollers can we clean at a time and do we need to remove bearings and gears?
As all Caresonic equipment is purpose built, you can have a single roller unit to a multi roller unit. All Caresonic systems are based on rotating the anilox so that only a segment of the engraved face is in the liquid at any one time and the journal ends are outside the liquid, meaning that in most cases the bearings and gears do not require removing. All type of roller cleaners can be designed to suit your individual system; contact us with your specifications.
Why choose ultrasonics over any other type of cleaning system?
Ultrasonic cleaning of engraved rollers and parts has been proven over the last 10 years as being the most successful and cost effective method of cleaning with major benefits such as lower capital costs than other systems, flexibility in cleaning multi rollers and parts in the same system, low running costs and no mess. Ultrasonic cleaning is also environmentally friendly and poses no major Health & Safety concern.
What else can we clean using ultrasonics?
Ultrasonic cleaning is an extremely efficient way of cleaning most items. In the print industry, as well as engraved roller cleaning, many units have been provided for ancillary component cleaning and wash up, i.e. for trays, doctor blade chambers, ink tanks, pumps and splash guard. Other applications include flat and rotary screen cleaning and stripping, polymer plate cleaning and rubber roll cleaning.
What do we do with the dirty water generated?
Caresonic units are offered with a pump and filter system as an option. Not only will they keep the cleaning liquid cleaner and prolong the time before changes but also remove the majority of solids prior to disposal. The cleaning chemicals are biodegradable and where necessary, neutralizers can be provided and hence on consultation with your local water authority, most printers are allowed to discharge the waste into the foul water drains.
Can we believe all the hype with regard to flat topped dots on the newest photopolymer plates?
Perhaps it is my age but they say if you live long enough most things will come into fashion several times during your lifetime and I suppose the same goes for graphics and plate production. Just in case anyone cannot remember flat top dots are what all dots looked like when we produced analog plates and in particular rubber molded plates. It has not been any secret that photopolymer plates have longed struggled to produce a dot that had a true flat surface to it and in fact have tried to hail these rounded surface dots as a steep forward in reducing dot gain. The problem they forgot to mention was that it can dramatically reduce the life of a plate particularly in the finer dot, text and line areas. So finally after a decade or so of digital rounded dots and a lot of marketing spin printers can now get plates with dots that have a flat top thanks to new UV led exposure units and inert gas exposure units that can emulate what analog plates did and still do naturally. The truth is flat topped dots, text or lines always produce crisper sharper images just don’t be fooled into thinking this is something new but do be grateful that the manufactures have finally recognized a simple truth, that while the world may well be round in the world of dots and sharper print, flat is better”!
Can you explain when I should use flexible dies and what if any benefits/disadvantages do they have over solid dies?
Flexible dies using a magnetic cylinder are most often used for shorter run jobs with common repeats.
There are a number of cost advantages when using flexible dies these include, reduced make-ready time when same repeat jobs can use the same magnetic base, less storage space is required, back up tooling is less expensive , and freight costs are much less.
It is vital that you use only cylinders that are in good condition and must run true with minimum TIR.
It is not unknown for flexible dies to move and in some instances it is recommended to actually tape the edges of the die to improve stability.
The smallest repeat recommended for use with flexible dies is 8” so you must ensure that you have a large enough repeat to reduce the possibility of deflection. Most repeat lengths are usually between 12 and 24”, but you also need to consider the press width as well.
Solid tooling is generally used and advisable for longer running jobs as they have greater durability, rigidity , and can be repaired and re-sharpened, flexible dies cannot be repaired and when worn or blunt must be replaced.
Magnetic cylinders are not cheap but if you have many common repeats they are well worth the investment. Most flexible dies can be produced in a few days, solid dies usually take two or more weeks.
How does the thermocrhomic ink work?
These inks change color as their temperature changes. Our thermochromic inks all work the same way:below the activation temperature they are colored and above the activation temperature they are clear or lightly colored. As the ink cools, the original color returns.
What is the standard lead time to manufacture this ink?
Standard lead time is 10 business days. The product will be shipped by the 10th business day from the day it is ordered.
Can Thermochromic flexo ink be mixed with different chemicals?
We don’t recommend mixing any foreign chemicals into the ink. Please consult with CTI before adding any additives or chemicals. Alcohols are not to be added to the ink, they will damage the thermochromic color-changing properties.
How do I store the ink and for how long?
CTI’s products should be stored in a cool, dry place and away from sources of UV light. The inks are stable when stored away from heat. The material is combustible and should not be used near open flame. Store Below 80° F. Water-based and solvent-based flexo inks must be used within three months of purchase, whereas all other flexo inks must be used within twelve months of purchase. Consult MSDS prior to use.
What is the “clearing point”?
Clearing point refers to “the temperature in which the ink stops losing color.”
How do we get a darker color?
Darker color can be achieved by increasing your film weight, typically by using a higher BCM anilox.
How does Photochromic ink work?
These inks are invisible until they come into contact with UV light, like sunlight. When photochromic ink is exposed to UV light, it blooms into color.
We have noticed that many of the teeth on our press gears have various wear patterns on them. Can you describe the cause for the variety of wear patterns and what they may cause in our final printed result?
Gears are intended to drive all types of cylinders and although they are a separate item when they are positioned on the journal of a cylinder it really becomes an integral component that is key to achieving a quality printed result. As with anything else I am a great believer in you gets what you pay for and in particular with gears so when ordering always buy from a reputable supplier usually your OEM or supplier that may have been recommended by them. All gears are prone to wear over time due to the natural stress and pressure that is put on them as they mesh together to drive various cylinders throughout any press. However if they are they are not maintained correctly then you will see uneven wear patterns occurring which can and will dramatically affect your print quality. One of the major issues is ink that will inevitably get onto your gears at some point and if not cleaned off in a timely manner will attract further dust and other particulates which if allowed to dry and compact at the bottom of the teeth will result in chatter and gear marking that will show in your print. You should also look out for abrasive materials in particular if you are cleaning your rolls with baking soda or plastic pellets as they can and will also cause great damage to gears and bearings if not removed as quickly as possible. Improper or lack of greasing will cause dramatic wear patterns in all gears but you must make sure that the lubricant is not itself contaminated that can cause pitting and other general wear to the teeth of the gears. Running your gears dry will immediately begin wearing the teeth of your gears immediately and should therefore should be avoided at all costs. To remove ink and other contaminants from around the teeth of the gears they will need to be scrubbed periodically and re-lubricated. Gears that are noted to be showing any form of wear should be replaced as quickly as possible. When gears cannot running freely and mesh together consistently will result in horizontal banding across your print and other inconsistent print results in both ink laydown and registration resulting in inconsistent quality and print results.
I read some recent comments on how Flexo compares with Gravure what is your opinion?
This question comes up on a regular basis, but really the true question is,” is it cheaper? “After all that was the primary purpose why Flexo was invented to produce a cheaper, simpler print process than gravure and letterpress. There is no doubt that at the outset it was substantially less expensive and was indeed simpler, but the big challenge was quality & consistency. Today Flexo has answered the last to points by producing some of the best quality print that can be found in any process and when measured and controlled can produce this quality consistently. To achieve these improvements this has come at an ever increasing cost and demands the very latest technologies, equipment, materials and inks to be able to compete with gravure and offset. So the bottom line is our quality does challenge that of gravure in just about every area and in packaging with fine text and small graphics without the serrated edge of gravure can even produce stronger sharper images. For short to mid- size runs it is also more cost effective due to the speed of changeovers but when it gets to extended long runs it is debatable whether it is less costly. Trying to remain as unbiased as possible I do feel that Flexo’s versatility, and continuous technical developments will continue to keep it at the forefront in terms of print quality but as with all new developments it does come at a price, the question is will the buyer be willing to accept higher costs for higher quality!
How can we be more environmentally friendly as well as create a more sustainable mindset within our company?
During my many plant evaluations and general discussions with different management teams the topic of pollution prevention, environmental issues and sustainability is always being brought up. As printers you can have a direct and immediate impact in all of these areas, and the key to how successful you can be is really dependent on how much education you provide to every person involved in your production process. Whether you are ISO approved or otherwise you need to document what you start with and in particular what this creates in the form of waste be it hazardous or just creates a further risk. Sustainability is all about reducing what you use or better still what can be reused. On press this could mean installing chambered ink systems, higher line count anilox, better roll cleaning, using bio degradable non VOC no HAP cleaning solutions, printing with 4 col process, re-blending of used ink, keeping containers and open fountains covered. Recycling of cleaning solutions or the use of cleaning techniques such as ultrasonic’s both reduce the amount of solution that has to be disposed of and help maintain the efficiencies of your product and equipment. Reducing set up times & materials are obvious areas that can have a radical impact on your efficiencies and waste stream so do look at these areas closely as they can have a dramatic impact o0n your waste streams. Segregating waste and the use of reusable container’s or recyclable materials are easy and very effective methods for all companies wanting to see immediate benefits and savings. Making these changes and looking for ways of finding more, means commitment from owners and management at every level, so clear communication, encouragement, recognition and training are all vital elements to achieving a more environmentally friendly and sustainable program.
How critical is prepress in helping Flexo achieve the final printed product?
This is an interesting question and one that needs a much longer answer than the one I am about to give at this moment. Prepress in its entire forms can and does have an enormous impact on your final print quality. And yet for all of the sophistication that we have in equipment and software I have to say it is possibly the weakest link in most print shops. The primary reason in a large part is the misconception that if you have the most sophisticated software and hardware that it cannot do anything wrong. The reality is that it only does what the operator makes it do. If the operator does not have adequate knowledge of Flexographic principles and more importantly what your presses are capable of then you will only ever achieve mediocre results. What today’s software and hardware does do I make it easier to manipulate and repeat consistently what you know will and has worked. The problem that we have is that very few companies understand the critical need to educate and train their prepress operators and assume that if they can manipulate an image then they must know what they are doing. Because a program can automatically trap and separate colors does not mean that what is done will suit your particular press needs. This is the reason for fingerprinting your press to determine the dot gain, registration and size of dot or image that can be achieved. It is then still up to the prepress department to determine what allowances and adjustments need to be made to a given image that when finally ink is transferred from the plate to the substrate will produce the final printed product. So, how critical is prepress?, I would have to say it is possibly the most subtle yet most important part of the entire print process.
How do we go about measuring the treatment level of materials that we are using on and off press?
Probably the most widely known method used in and around the press room is the use of a Dyne pen to measure the treatment level of most materials. It provides a very fast method of checking the treatment level of a substrate being used. The tip of the pen is drawn across the entire web in a straight line and at the same time you look to see if the solid line does not break up for at least 2 seconds. Dyne pens come with different dyne level solutions and are designed to indicate surface treatment levels on polymeric materials. It should be understood that with repeated use the tips of the pens can become contaminated but they do give a quick and reasonably accurate result that any operator can be trained to use. They usually have about a six month shelf life. You should date them when you first open them and must always put the lid back on after each use.
Another method is to use a cotton swab using dyne solutions of various concentrations. Similar to the pen the swab is placed onto the substrate having first been dipped into a container of solution and spread over an area of approximately one square inch. You may need to use several differently calibrated solutions to determine what treatment level you have on your material. Again if the wetting solution stays intact for two seconds the treat level is at least as high as the dyne level of that solution. You must use a different swab for each test to avoid contamination. Again although this has been used for a long time it can still be inconsistent. Because of this it is usually do by your ink or coating supplier in a controlled area.
The final and most accurate method is a draw down test. In this a piece of material of approximately 8.5 x 11” is pinned to a board and a single drop of three different dyne solutions are placed at the top of the material to be tested. A wire wrapped rod is then drawn down across the droplets and again when the liquid breaks after 2 seconds you will know what the treatment level of the film is as indicated on the solution provided. It may sound like a lot of effort but if you really want accurate results this is the most accurate although you must always clean the rod after every use and watch the shelf life and storage of the solution at all times.
How long should a photopolymer plate last for?
This is possibly one of the most frequently asked questions in flexo regardless of the machine that they are being run on or the substrate that they are being printed on. The causes of premature wear and failure of any plate are dependent on many variables and the press and substrate are but two of them. Over impression and trying to run a plate when it is improperly inked up are two other key factors that will dramatically affect the life of any plate. Clearly some plate materials will and do perform better under the manufacturers specified conditions so great care should be made to follow these recommendations as closely as possible. The actual processing of any plate also has a major effect on any plate so great care should be taken to ensure that plates are correctly exposed,washed out, dried and finished. Failure to process your plates exactly as prescribed by the supplier and to monitor the condition of your exposure unit, laser head, and washout unit can and will lead to underperforming plates. All plates have different resistances to inks & solvents and again you must consult with your plate supplier and ensure that the plates are not used in conjunction with the wrong ink or solvent systems. Highly pigmented or metalized inks can have a significant effect on many plates regardless of what you do and clearly failure to clean dried ink from a plate at any stage of its use will cause premature wear. Defoamers tend to affect most plates so you should keep the use of them to an absolute minimum. Prolonged exposure to UV light and ozone environments will both cause plates to dry out and crack so they should be protected from both elements whenever possible. Excessive heat whether from driers or caused by friction will again affect many plates and as already mentioned over impression between the anilox and plate cylinder and plate cylinder and substrate can and will have a severe impact on a plate. Failure to mount a plate correctly by leaving air bubbles and creases between the plate and sticky back will cause not just plate wear but print issues all day long.You should also make sure that your plate cylinders are true and straight as well as your gears are clean and not worn as any inaccuracies will transfer to the surface of the plate which again will lead to uneven wear to the plate surface. Recycled board, tissue and other fibrous substrates including dusty materials will all cause wear to a plate as well. Improperly polished and course line counts on your anilox can also affect plate life. Finally, keeping your plates clean and dry and properly stored when not in use are other fundamental ar4eas that can either maintain or destroy a plate if not properly taken care of. Always scrub a plate with soft bristled brush, use mild detergents, protect from exposure to sun light or ozone and do not let the plate rest on anything while still mounted around a sleeve or cylinder. If stored loose they should have a foam interlayer and stored flat r hung vertically in appropriate storage hangers. So how long should plates last? Well you tell me as it really depends on how well you look after and treat your plates every time you use them.
How much time do we need to spend on press maintenance, and what would you recommend as daily basic maintenance needs?
There never seems to be enough time to carry out basic maintenance in most print shops but there always has to be time made when there is a mechanical failure. The truth is if you carry out regular daily maintenance on your equipment you will be amazed at how much longer your equipment will last and how much more efficient you will become. No matter how basic or sophisticated your equipment continuous operation of your machinery will result in continuous wear and tear. Even if you do carry out the appropriate oiling, greasing, but fail to carry out these fundamental requirements it will for sure result in some form of mechanical failure that can lead to significantly higher repair costs. The logic given by most managers for not carrying out basic repairs or maintenance is the inconvenience when trying to run their equipment, or lack of available personnel so they resort to what is commonly termed “breakdown maintenance” ie “ fix it when its broke”. Clearly this is not a logical statement and in reality always results in higher costs and greater “unplanned” down time which at its worst could even result in losing a customer due to your failure to deliver a quality or on time product or both. So to some extent how much time you will need for maintenance depends somewhat on how many hours you are running, the age of your equipment, speeds you are running, materials, ink systems and market you are serving. Basic needs including oiling, greasing, replacement of obvious broken parts, visual inspection of all moving parts, tracking of production output to help identify drop of in productivity that may help determine some of the less obvious areas of non-visible wear and tear. Most of these aspects can be taken care of in a matter of minutes and can save hours of down time as well as untold benefits in print quality, operator morale and customer satisfaction. So what you need in place is a preventive maintenance program and by this I mean the more you carry out regular planned maintenance the better you will be in every aspect of your productivity, profitability, and the more you will be able to prevent unplanned downtime and costly repairs that you have not been able to budget for.
Many people are saying that Flexo is capable of producing anything that offset or gravure can do, and for less; how true is this?
Well as a Flexographer for almost 40 years my reaction is and always has been absolutely, yes! Experience has also shown me that in reality when attempting to convert a package from any other print process that there is a considerable amount of effort that has to be put into any design and that is just the same for Flexo. There is no doubt in my mind that if you have a great team in your prepress and print department and a customer that is aware of the capabilities of the flexographic process that we are capable of producing outstanding printed product that can in many instances look as good if not better than offset or gravure printed materials. With the state of the art digital prepress software & hardware, new plate materials & tapes, in the round sleeve technology, new ink chemistries and new servo press technology the companies that continue to stay ahead of the curve with these products and have the right expertise both in-house and externally can often produce as good a product for less. The question is are you prepared to place yourself and your company at the cutting edge of technology by investing in the products, equipment and people that will enable you to also say, yes we can! You might think that the equipment makes all the difference and of course it is critical but probably greater than all of this is the caliber of your team and the constant need for retraining and evaluation. There is so much information available now and so many options that making the right choice for your business and your customer is key to you and their success. New screening software is now enabling the modern flexo printer to print up to and beyond 200 lpi and EGC technology and similar is allowing almost unlimited colors to be achieved. Even the range of substrates which have always been almost unlimited for flexo is continuing to be extended with non- woven materials and many other exotic laminates and extruded materials. I have to say it is much easier to create flexo from a new design than from an existing printed product as the buyer will always have a fixed perspective as to what to expect and see but with adequate communication at all stages of the process flexo is often showing that it can indeed produce world class print that is a more than a match for any other print process regardless of what name. However, it is up to you to prove if it can be done for less!
We are having adhesion problems with our ink when we do standard crinkle and tape tests, can you please suggest what may be the root cause of our problems?
Though not always the case many causes generally relate to your inks such as high or low viscosity, inks drying to fast or to slow or sometimes the wrong ink system for the material you are trying to print. More often the root cause is just inconsistent treatment of the film or insufficient treatment that will allow the in to key adequately to the substrate. It may be necessary to apply a primer prior to printing even with treatment dependent on the ink chemistry you are using. Also make sure you have sufficient airflow and heat from your driers as insufficient of either can and will also cause adhesion issues. Finally you may even have an ink surface tension issue which is something you would have to ask your ink supplier to check out for you. Always check the surface tension of the material you intend to print as even adequate initial treatment levels can and will decay over a period of time.
Can you give me some suggestions on how to handle my inks more efficiently with less waste?
Ink is one of the largest consumable costs for all printers not just in the cost per pound but also the cost of disposal so efficient use of any ink is highly desirable from every aspect. The first step is to ensure that you are ordering not just the correct ink for the print application but importantly that you correctly estimate the amount of ink needed for each job. This is particularly important if you are using more specialized inks such as metallic inks. It is equally important to ensure that you try to schedule jobs with the same colors to run as a group so that you will save in press wash ups and unnecessarily contaminated ink when being drained back to their ink buckets or barrels .All inks should be carefully labeled so that every operator can easily identify them and if you have bladed or two roll presses even which press they were run on as the viscosity and chemistries may need to be different, and don’t forget the date of usage. Try to always use your oldest inks first and always make sure ink lids are securely fastened down on all cans and drums. Use chambered ink systems for more efficient ink metering & lower ink volume , and use higher screen lower volume anilox with higher pigment strength inks to ensure the thinnest ink film possible. This will dramatically increase the mileage that you get from each pound of ink. Maintain your anilox to ensure you have minimum blocking of the cells so that you do not have to have your inks adjusted to compensate for the loss of volume form the anilox cells due to plugging. Ultrasonic systems do an excellent job of getting to the bottom of every cell and removing not just the pigments but the resins as well. If you are washing up the anilox on press make sure that non of the wash up solution gets into any fresh ink buckets .This is a major issue with water based inks so great care should be taken to try not to let these inks dry on the anilox or other machine components. Blending your own colors from a base color ink kitchen is an excellent way of ensuring that you only mix exact quantity of ink that you need for each job and also makes reworking of your inks easier as well. With water based inks make sure that your operators know how and when to measure the pH of the ink and how to adjust the viscosity as necessary. This will not only reduce your ink cost but also your waste costs. Make sure that you get ink draw downs from your vendor and check carefully against your color swatches when received and before you take the ink to press or pump up to the print deck. If you are using solvent or water based inks and have the option to switch to UV inks this ink system will greatly reduce your ink consumption.
Is digital platemaking the future, and if it is what type of plate will work best for my business?
There is no doubt that digital plate processing is the future for all plate systems so if you are still using analog film technology to make your plates with you need to be looking at a digital system now. As with all newly emerging technologies there are many different competing technologies. This is not just related to the hardware but is very much interlinked to the software, plate material and plate processing systems. You might have thought it a difficult decision to decide what material, plate thickness and washout process to use such as water, solvent or thermal in the past but you now have to contend with the addition of software programs and laser exposure systems that can make your head spin. Fortunately most major prepress equipment and plate material suppliers offer a complete turn-key package and technical support the likes of which has never been seen before. This is because the decision process is a complex one and varies dependent precisely on your business model and the print market that you are supplying. This is because the presses, substrates, press speeds, graphic content, end use of the product , environment , operator skill set, location , investment required and legislation all impact on your decision. It has indeed become a challenge for everyone and that includes the experts alike and is likely to go on for some time. The good news is whichever technology you choose it will be infinitely better than your traditional technology in terms of quality and sustainability but as with all new technology it comes at a price and generally requires heavy investment initially and continuous re-investment if you want to stay in front of your competition. Plates come in a wide variety of materials, durometers, solvent/ink resistance and thicknesses but in my opinion it is the software and your operator skill and understanding of your printing capabilities that can and will have a profound impact on the end result of what you print. The trick is to be patient and look for a supplier that Is willing to provide plenty of support in a form that you can understand and walk you through the many variables that there are , while allowing you to try the materials until you find a selection that works for you. The major thing is not to make a decision based on what another printer is doing elsewhere even if they are in the same market , your needs are likely to be unique and there is no guarantee that he has made the right choice. In my experience it takes many months of trials before any conclusion can be made which is why you need to find a supplier that will support you during and after your decision process. Like all technologies it will be a matter of continuous development .As always in our industry there will continue to be choices to be made. The key as with all digital , electronic technologies is to understand than more than ever before you cannot afford to stand still and become too complacent as there will always be a new development right around the corner that will continue to drive our industry to new heights. So what plate type will work best for your business? It’s the one right around the corner of course!
It seems that everyone is talking about 2D bar codes and other mobile tags. What benefits do they bring to the consumer and the seller over traditional bar codes?
Barcoding is so common place now that they are included on almost every type of product and packaging that you can imagine. The problem with conventional UPC linear bar codes is that they the amount of information that can be incorporated into them is very limited and until relatively recently with the advent of smart phones and apps could only be read at the checkout of a store. That said they are well proven and continue to be used with great success. Their successors have been the QR (quick response) 2D bar codes that again in conjunction with smart phone, app technology can physically connect an object to a digital experience such as a video for example. This gives marketing companies the opportunity of a life time to be able to promote and enhance a potential buyers experience beyond anything that was possible before their invention. You can put a 2D barcode on almost any printed packaging, posters, signs, websites, clothing, adverts and you can scan them with any smart phone and instantly see information on line that the manufacturer/agency has created. They have an open –source platform that means they do not need to have access on line to decode them. They can also be in black and white or basic process colors. Tags must have a white border to ensure it remains readable. The width of the white space should be equal to the height of the bottom black bar, and not have any encroachment of lines, figures, or other elements. While many of the products may not be packaging there is no doubt that they will be included on most packaging and for the foreseeable future UPC barcodes will continue to be used but in time I have no doubt the QR 2D barcodes will gain in popularity and will continue to be developed by designers and printers alike.
What is (ITR) technology, and how can it benefit my company?
“ITR”, otherwise known as “In the round” is the generic term that has been used for a long time to describe any image that has been produced around the circumference of a plate cylinder or sleeve in either a photopolymer or elastomer covering. The technology has been used primarily in Europe for over thirty years with elastomer coatings being vulcanized, ground and directly laser engraved onto sleeves and integral rolls. While plate material has and still can be exposed in the round and is classified by some as “ ITR” , I personally only classify it as true “ITR” if the material has been bonded or vulcanized to the sleeve or roll circumference and engraved or washed out while in a continuous format. As to the benefits of true “ITR” they are many ranging from, dramatically increased press speeds, improved print quality, improved registration, more uniform densities, less dot gain, less bounce, reduced waste, improved productivity, improved profitability, less set up time, less make ready. I think you should be getting the idea by now that if plates are eliminated and you use ITR technology your efficiencies and profitability will dramatically improve.
Is it really worth the cost to switch from conventional plates to digital direct to plate technology?
Having been involved with direct to plate technology for over three decades, yes it has been that long and longer since it was introduced I have to declare that I am somewhat biased.
In my case we were directly engraving rubber coated rolls, sleeves and rotary screens using the earlier Scitex systems and direct laser systems but evn then we could see the many benefits if only in eliminating the myriad of films and step and repeating that was needed to make the printing plates by conventional photographic exposure.
Sure we did have a steep learning curve and we did have some limitations but today’s direct to plate systems have virtually eliminated most of these issues and can now produce the smallest positive and negative dots consistently from plate to plate time after time.
If for no other reason it is the consistency of the plate making process that all manufacturers now offer that I can strongly recommend the cost to switch to the new DTP systems and feel that with the final step to direct to sleeve engraving now coming into being even the few limitations of the printing plate are also about to become history.
The payback just in eliminating the film work and not having to worry about the deterioration of the film separations or damage caused by mishandling quickly covers the investment in the new equipment needed for the digital process and with the new hybrid screening technologies is allowing many flexographers to go beyond the 150-200lpi screen range with confidence and in some cases up to 300lpi.
What are the benefits of printing with UV inks?
Generally speaking UV inks will allow you to run faster, achieve crisper, sharper print achieve brighter colors and gloss reducing the need for over varnishes.
If the growth of UV usage is anything to go by of 10% verses 4% or less for other ink systems it would appear that all print markets would agree.
Because of the minimal dot gain and spread with UV flexo printers are achieving print quality consistency and detail that has never been achieved before on all types of substrates.
UV inks are also much kinder to your anilox with almost no plugging caused by the ink itself in the anilox cell you will get much more consistent ink release from your anilox and much longer life which is a great cost saving as well as print quality and scrap material saving. UU does not dry by evaporation as other ink systems do so it has little or no effect on the immediate environment.
You have talked about ultrasonic, plastic bead and bicarbonate cleaning of analog, and other than manual cleaning what else is available?
The most recent addition to anilox roll cleaning uses the very method in which it was created by the means of laser technology. Rolls or sleeves are placed in an enclosed unit and rotated while a laser beam is exposed onto the engraved surface of the anilox, and by controlling its power output, traverse speed and rotation the contaminants are vaporized leaving little or no residue. Needing no solvents, water or other cleaning solutions other than the laser beam itself the process is very efficient and produces little or no waste. It can be used on any engraving and is able to get right down to the bottom of each cell. The process is fully automated and needs little or no labor other than putting the rolls in and taking them out of the machine.
Is laser cut die cutting the way of the future or is it a proven technology already?
Laser technology in itself is a very well proven technology that is used in many industries and used to cut many different materials. With a roll making background myself I can certainly testify to its incredible capabilities in being able to engrave many different forms of elastomers, metals and ceramic coatings. It is certainly the preferred technolo9gy when it comes to laser exposure of today’s photopolymer plates which in a large part has been greatly enhanced with the dramatic developments in software programs that are now readily available. All that said I do believe it is the way of the future for die cutting label stock materials but does still seem to be challenged with some materials. To be fair with the constant addition of new materials and demands from many buyers it is understandable that some of the more exotic materials and complex shapes being demanded will be a challenge but as I have found from personal experience the laser manufacturing industry is not slow at finding solutions to meet the many demands that are thrown at it. Just like digital printing , laser technology has many areas of improvement needed such as speed as , heat build up and coping with different stock materials and thicknesses which will all have their own learning curve, but I am certain they will be overcome. So is it proven technology I many ways yes but for sure it will be the way of the future !
Many of our print cylinders, anilox and web guide rolls on our older machines are in need of refurbishment but our supplier is suggesting we have them completely re-engineered as light weight cylinders which cost much more than our original solid cylinders. Is he right that they will give us better performance and other savings, or is he just trying to get more money out of us?
As with everything else in the Flexo industry roll technology has not stood still from the early solid or thick walled tubular designed rolls that we are probably all familiar with, light weight rolls have indeed become the new standard. Using combinations of carbon–fiber, fiberglass, aluminum many rolls offer even greater rigidity and performance than more traditional heavily built steel walled cylinders. Reduced roll weight creates less wear and tear on bearings, journals, and with less start up inertia much less wear on the drive motors and clutch’s and often leads to smaller motors being needed so less power is also consumed. Handling and moving of lighter weight rolls also makes for easier handling when lifting rolls in and out of the press and makes storage racking much less costly to build, and if rolls must be manually handled makes the process much safer. Light weight rolls generally maintain their TIR longer as there is less sag created and much less stress put on the journals when running and again when being lifted in and out of the press. The down side as you say is they do generally cost more because light weight rolls are a much more complex design but the benefits and payback are well worth the initial extra investment.
Can you comment on the importance of maintaining your anilox?
It is interesting that I should be asked this question as I am in the middle of producing a much longer article regarding this subject. The fact that the anilox is the heart of any flexographic printing press in itself should tell every operator the importance of maintaining their anilox. Let’s assume however that you have firstly purchased a well-made anilox from a reputable manufacturer it is vital that you keep the engraved surface as clean as possible at all times to ensure that it is able to pick up and release a uniform volume of ink or coating across its face and around its circumference consistently throughout the print run and from job to job. Failure to maintain your anilox will result in inconsistent densities, coat weights and print quality all of which will result in higher scrap levels, slower speeds, greater downtime, and of course less profitability. So is it important to maintain your anilox ? Well unless you do not want to remain in the printing industry for very long I would have to say it is critical and should be the key component of any planned maintenance program.
We are really struggling to get our anilox and print sleeves on and off our mandrels do you have any tips as to what we could do to reduce these issues?
The first key point with all sleeves and mandrels is to keep them absolutely clean.
Any ink, water, cleaning solution residue, tape or adhesive that gets onto the surface of the mandrel or the inside of the sleeve will cause removal problems of the sleeve from the mandrel.
Remember most sleeves only being expanded by a few thousandths of an inch so even the slightest amount of contamination on the surface of the mandrel or the inside of the sleeve can and will cause major problems.
Care should be taken not to damage the surface of the mandrel, so any scratches or burrs should be polished to a smooth finish. Similar damage to the inside of the sleeve will not only cause removal problems but may actually cause it to split when put under pressure so even greater care should be taken with the inside of the sleeve to prevent any form or scratching or scoring of the sleeve.
If you are using a simple air mandrel with an inlet hole through the journal or header and air holes drilled through the wall of the core near the end of the core face and in the middle great care should be taken to ensure that your air that is pushed into it is free from any moisture or oil. Even the slightest moisture whether it is in the form or oil or water will cause major release issues if it gets between the inside of the sleeve and the outer surface of the mandrel. In addition water moisture or vapor can and will cause corrosion within the core itself which in turn can build up in the air outlet holes and also cause further contamination between the sleeve and mandrel face. In extreme instances it can even weaken the core structure which could lead to catastrophic failure.
In my experience mandrels that have air piped to each individual hole is far safer and in fact makes the air mandrel no longer a air vessel that would under normal circumstances be certified to be able to withstand the air pressure used to lift the sleeve off the mandrel.
Having a small bevel on the end of the mandrel where the sleeve is introduced will certainly help to push the sleeve onto the mandrel instead of having to walk it on which can cause cracking of the edge of the sleeve.
Make sure that your sleeves are never dropped on their sides this will more than likely distort the sleeve making it oval instead of round and the only solution is to replace it.
This is particularly pertinent with regard to the anilox sleeve with its multi layer construction. If your anilox sleeve has an end ring and you see a crack appear between the ring and the sleeve it should be glued with a suitable epoxy resin to help reduce the complete failure rate of the sleeve but is usually inevitable once this has occurred and is just a matter of time before the sleeve becomes unusable.
Even spraying silicon or wax to the mandrel surface can cause problems if it is allowed to build up on the mandrel surface.
If you mandrels are not fixed on press you also need to invest in a suitable jig to hold the journal of the mandrel so that the roll can be held in the air to allow the removal of the sleeve from the opposite end.
The truth is parallel sleeves will always have some removal issues at some point during its life time no matter how good your housekeeping is.
In the early days when sleeves were initially introduced they had an internal structure this eliminated almost all sleeve removal issues and allowed very low air pressure to be used to remove them, personally I still feel this was the better design.
Why does my printer say he cannot use my offset artwork files for his flexo printing process?
This is a common issue that many printers have to struggle with on a daily basis.
While flexo is proving to be more than a match for offset it still uses a compressible plate and therefore allowances have to be made for sublimation and compression when creating the necessary color separations whether in hard copy or digital format.
Such areas that need particular attention are font sizes, intaglio and relief line dimensions, range of colors and screening technique and dot size and shape used.
What are the benefits of servo technology?
Starting with the obvious reduction in gears, servo technology has impacted just about every aspect of the flexographic process to the point that many printers are now able to match or even better litho quality.
By eliminating conventional gear and drive systems registration can be held at all speeds with in many cases +/- 0.001” being achieved, and guarantees no gear marking.
Make ready and set up times are dramatically reduced due in a large part to the automation of the press that this technology has brought to flexo.
This has a significant impact on reducing waste and overall costs no matter what the substrate. Full recall of all preset settings can and is now being achieved thanks to the servo capability guaranteeing consistency from one job to the next.
All of these factors lead to greater efficiency which in turn leads to more profitability giving those that upgrade to or purchase servo built equipment a great competitive advantage.
What is ITR technology, and what are some of its benefits from today’s flexographic printer?
Although ITR technology may appear new to many printers it has been attempted and in recent years proven to be a successful technique of exposing or engraving rubber and photopolymer coatings “ In the Round” instead of in a flat sheet form, hence the term ITR..
For all of our many successes in the world of graphic software and plate making the issue of having to manually mount the printing plate onto the plate cylinder or sleeve is still a major headache for most printers.
The ITR method eliminates the need for manual mounting, eliminates the need for sticky back. and can guarantee registration between colors without the need for video web mounting or pin registration systems.
There is no need to worry about plate lift, and no need to worry about distortion factors as this is all taken are of when the image is exposed, etched and engraved into the coated surface of the roll or sleeve.
For many this technology could not have arrived a moment to soon, and for others it may be seen as a more costly way of getting an image ready for printing.
Even though this technology as it always has had its doubters I have no doubt that this will become the standard process for any Flexographer, that wants to run and remain profitable, while meeting the needs of today’s buyers, that will continue to demand perfection with every print run. This is really the holy grail that flexo has been searching for all we have to do now is grasp it with both hands and make sure that it succeeds for everyone’s sake.
What plate mounting tips can you suggest to help us produce more consistent results?
You did not say what inconsistencies you were having with your mounting but some of the more common issues include mis-registration, plate lift, air entrapment, plate movement and uneven ink transfer.
Mis-registration is by far the most common and the most serious issue for any printer as it usually means having to stop the press to either adjust the plate on press or may even entail having to remove the plate cylinder to remount the plate.
This is usually caused by human error and mis-judgement when positioning the plate onto the plate cylinder particularly if only using your naked eye to match register marks.
If mounting manually by eye it is best to have two or three fine vertical lines built into your bearer and to make sure that plates are trimmed accurately and square so that you can almost butt them together when the plate warps round the cylinder. You may need to use a magnifying glass to help make a final adjustment but when mounting by eye only it takes a lot of practice to develop the skill necessary to do it reasonably accurately. Applying a couple of lines of a yellor marker pen to the surface of the tape also reduces the tack enough to allow you to readjust the plate without pulling the tape away from the cylinder surface which can cause rippling and air bubbles under the tape. The better method of course is to use on one of the many video mounter proofers that are able to magnify even a tiny dot so that the operator is able to position it to hairlines on the video screen within fractions of a thousandth of an inch time after time.
There are also pin mounting systems in which holes can be drilled through a carrier sheet or the plate itself and are then mounted onto removable raised pins that are on the cylinder and can be removed after the plate has been adhered to the cylinder itself.
Plate lift occurs more often when on press and is usually the result of solvent, ink or water getting under the edge of the plate a short term fix can be to apply a black sharpie to the edge of the underside of the plate which usually reactivates the adhesive of the mounting tape sufficiently to help it stay down. If this is a common problem you can apply a plastic sealant around the edge of the plate immediately that you have mounted the plate and let it dry this is usually very effective.
Air entrapment between the tape and cylinder or tape and plate is always the result of failing to apply the tape uniformly to the cylinder by means of wiping the surface of the silicon cover sheet as it is pulled around the cylinder and if any air bubbles are seen stopping to readjust and smooth down the tape as you move around the circumference of the cylinder. You can use the palm of your hand, a cloth or even a rubber coated hand roller with the same applying when you adhere the plate to the tape. Mostly it is due to the impatience or lack of care when applying the tape or plate so it is well worth taking your time and doing it properly.
Plate movement is usually caused by the improper choice of tape and adhesive to suit your print application in that the adhesive is unable to hold the plate when running at speed due to ink or solvent attack or even extreme temperatures. Very often it is the result of trying to reuse the same mounting tape from one job to the next and while tempting to cut down on tape usage the downside of plates moving and failure to hold them in position usually far out ways any savings that you thought you might make by using the same tape several times over. Often managers are not aware this is going on and is done by operators meaning well but just do not realizing the consequences of being penny wise and dollar foolish.
Remember most tapes are pressure sensitive so only really achieve full adhesion between he plate, tape and cylinder when actually running.
If you are leaving plates mounted on a cylinder for a future run after first having cleaned them you can wrap Ceram wrap around the cylinder to help keep the plate and tape under pressure. Also always keep plates stored in a reasonably stable temperature and try not to allow them to be exposed to excessive ozone or UV as these will both attack the plate surface.
Mounted plates should never be allowed to be stored with them sitting on anything or having anything sat on them as this will cause flat spots. Cleaning the plates carefully after every run will significantly extend the plate’s performance and life expectancy.
Uneven ink transfer can be caused through improper plate finishing or contamination becoming trapped between the plate, tape and cylinder so all plate mounting areas must be kept clean at all times and plates and tape checked for any particles before mounting them in position.
My company is interested in using ultrasonic’s to clean our anilox, how does it work, how long does it take, and is it safe?
Ultrasonic’s uses a process termed “cavitation” where micron size bubbles form and collapse rapidly in a liquid. Cavitation is produced by the alternating high and low pressure waves generated by high frequency (ultrasonic) sound. During the low pressure phase bubbles grow from microscopic size until during the high pressure phase they are compressed and implode.
The bubble stores a lot of energy and heat inside it until the implosion event when near a solid object changes the bubble into a suction jet which can travel at speeds up to 400km/hr away from the surface.
This combination of pressure, temperature, and velocity is what frees contaminants from the substrate that they may be bonded to.
Because of the sub micron size of the bubbles during the cavitation process the smallest openings in a laser engraved ceramic surface or other component can be cleaned very effectively.
Cleaning time will vary, depending on such things as the degree of contamination, how long the material has been on the roll or component, temperature and degree of cleanliness desired. It makes sense to remove excess ink or other coatings from whatever you are trying to clean as this will not only take longer to remove but will reduce the effectiveness of the process as well as the life of the cleaning solution.
In terms of how safe the cleaning process is I presume you are referring to the engraved surface when an anilox is being cleaned. The answer is that it depends on the system that you are using, the safest are systems that use a frequency sweep ultrasonic generator that automatically modifies the ultrasound hundred so times a second which if fixed could eventually affect some surfaces. In the case of rolls or sleeves they should also be rotated, the best systems have fully automated preprogrammed rotation systems for the safest and most consistent cleaning.
I have never been a 100% certain when it came down to anilox line count and volume selection and am even more confused with the recent variety of non- hex channeled style of engravings. Will these new patterns replace the traditional hex patterns and how do I make the right selection to suit my needs?
You are not the only person to be confused by the extended range of channel shape and stretched hex cell patterns that are beginning to be promoted by many different engravers. They are the result of the latest laser and software programs to have been developed over the last few years and have given engravers a renewed motivation to search for the ultimate universal engraving. The reality is that it is really all about the volume of ink that you are able to deliver to the surface of the plate as uniformly and as thin a coating as is possible that will ultimately give you the ideal color density. Certainly the channeled and stretched cells help to maintain a more uniform flow of ink or coating around the anilox and dramatically help reduce plugging that can be found in more conventional hex shaped cells. In my opinion we are not far away from not being too worried about specifying the line count but rather the volume that we are looking for which in part should simplify the process and could lead to a dramatic reduction in the number of anilox that you might require in your inventory. As to whether they will replace the more conventional cell structures I really do not think so at the moment, but would go so far as to say that they can be a useful addition to the menu of rolls that you can put at your printers fingertips when trying to meet certain specific coat weights and ink densities. They will depend very much on the ink industry catching up with this new development with inks and coatings probably needing to be milled specifically for these unique engravings in the meantime you need to work closely with your engraver and ink provider to help you make the best decision to suit your specific needs. Like everyone else I will reserve my final judgment until we have a few more years of empirical feedback from the industry.
We are an offset printer but sometimes get jobs that the customer wants to have printed Flexographically. We recently sent a set of our existing files to a flexo printer only to be told that he could not use them to make plates and would have to completely re format the files to suit his process. Can you explain what changes he will have to make or is he just trying to make money out of us.
This is a common issue when trying to print a Flexo job from existing offset artwork. Let me say first of all your chosen printer is not trying to make money out of you. Flexo and offset whilst both capable of producing high quality work both need to have files sympathetically separated to suit each process. To begin with most offset jobs create solids from process screens regardless of what images are within those solid areas which allow for very exact color matching, but require perfect registration; and little or no dot gain. Flexo on the other hand generally prints solids as spot colors and reserves process areas for graphic images but will always have some dot gain and with most plates will find it difficult to achieve absolutely perfect dot to dot registration. For this reason most colors will have a trap of the lighter color under the darker color that it runs up to whereas offset files will have little or no trap. Because of the tendency for Flexo to produce some dot gain and for colors to spread a little fine relief lines and intaglio lines/ dots have to be opened up or reduced a little when the files are being produced which again is something that offset prepress operators really do not have to worry about. In terms of screening while many Flexo printers can now achieve line counts of over 250 lpi the average is in the 150 LPI range for most jobs while offset is much higher. So I have to say that rather than making money out of you I think this printer is trying to save you money and the headache of having to explain to your customer why your files did not permit the production of a job as good looking as your offset print as they would not be sympathetic to the Flexographic print process just as Flexo files would not entirely suit your process.
We are offset printers but are being told by many buyers that flexo is simpler, cheaper and can match our quality, I do not agree but have no real flexo experience, so who is right ?
Let me first of all say that this is a topic that we may never agree on because it really depends on how open minded we can both be.
As you said you are an offset printer, and I have been involved with flexography all of my working life, and similar to your not having experience with flexo I have to admit to not having spent much time delving into the offset process.
In fact I have spent most of my career defending and lobbying for flexo in the same way as you have for offset.
So now we know where the lines are drawn, let me first try to define the two processes and then begin to make some comparisons before finally trying to answer your question.
Offset uses a surface thin plate that has a surface treatment that attracts ink and water to different areas that I then transferred to a blanket which in turn transfers the imaged areas to the substrate.
Flexo on the other hand uses a rubber or photopolymer raised area that is inked up by an anilox roll before transferring the image to the substrate.
Now I mentioned the word ink, and again this is where the two processes differ dramatically. With offset you have thick oil based slow flowing ink that has to be transferred between a chain of rollers to make it thin enough to transfer to the treated plate surface. With flexo you have a choice of water, solvent and UV liquid inks that flow and dry rapidly.
Now to try to answer your question perhaps I should respond to each of the points that your buyers were saying about flexo firstly being simpler.
As much of an advocate as I am for flexography I have to admit that achieving good, consistent print quality with flexo is anything but simple.
Compared with offset the skilled flexographer has a lot of choices to make such as which ink system, what type of plate, thickness and hardness of plate, what mounting tape to use, to name but a few of the many options that have to be made. So simpler, I would have to disagree with but would have to say that today many flexographic printers follow strict industry guidelines that help make the process very repeatable and consistent.
Again with the second statement of flexo being cheaper I do not believe that this is the right word to use, competitive, good value for your money,. Like most buyers that don’t know flexo they equate the first statement of simpler to meaning cheaper when in fact I have already proven that the many options that have to be considered in flexo compared to offset make it anything but simpler, but consistent and highly efficient techniques , processes and equipment in flexographer today do make it very competitive.
Now to the quality term and on this point I have to agree there are many areas that flexographic print quality does compare favorably with offset and on some substrates I would have to say does an even better job. The truth is flexo can print on the widest range of substrates of any print process which is one of the major reasons for its popularity in the first place.
So who was right? Simpler, cheaper, a match for offset quality, it all depends on how much you really understand about each print process, so now that you both know a little bit more perhaps you will be able to make your own decision., But if you want more information to make a more educated decision write back to me with more questions or comments and we can continue the debate.
I am new to the plastics industry can you describe the difference between HDPE and LLDPE film material?
(HDPE ) High density Polyethylene was the first linear polythene that was introduced in the late fifties. Its higher density provides good stiffness, environmental resistance to stress cracking and to low temperatures. It has been and is still immensely popular and is used in many different markets.
(LLDPE) Low-Density Polyethylene was the second linear fill and was introduced in the early eighties although some forms were available as early as the sixties. It is very similar to HDPE but has a number of differing side chains that can be made up from butane, hexene and octane. It has good tear strength and impact strength and is very much seen as the workhorse of the industry. To each can be added color, slip, anti-fog, anti-lock and anti-stat agents which makes both materials very versatile. A newer form of LLDPE IS mLLDPE which is another linear polyethylene called Metallocene Polyethylene. Its main advantage is that as its density decreases the melting point also decreases whereas LLDPE density has little effect on its melting point.
Can you explain a little about Plate distortion & stretch factors?
All plates are prone to distortion and shrinkage in particular traditional molded rubber plates that will shrink and stretch both in their length ,width and thickness , usually in the range of 1,5 to 2%. This is very much determined by what materials are included in the plate construction, the compounds themselves, the plate thickness, and the size of cylinder or sleeve it is to be mounted onto. Now with photopolymer shrinkage issues are generally disregarded as in theory they should not shrink with the stabilization (polyester sheet) that is bonded to the back of the photopolymer. This said, anyone that makes plates knows not to expose and washout plates from the same job running around the plate length and the across the plate width as a difference in tightly registered plates will be seen as a slight mis-registration due in part to the different alignment of the polymer strings which can cause a slightly different stretch or apparent shrinkage difference. This can even apply between plates that consist of heavy solids and other plates that have little or no print areas, in particular with thicker plates and deeper etched plates. This is why it is critical to maintain a uniform depth when plates are washed out if photopolymer and applies the same to metal molds if chemically etched. All plates will distort( stretch) when wrapped around a curved surface and will elongate on the outer surface and contract on the inner surface of the plate. For modern photopolymer plates the standard calculation is 3.1416 x 2 times plate thickness over its repeat length. Plates mounted on stickyback prior to mounting o the print cylinder have much more surface stretch and distortion than when mounting a plate onto the stickyback that has already been mounted on the print cylinder or sleeve.
How do we maintain and enhance the life of our photopolymer plates not just during the run but in particular when we come to use them for a second run or more?
Assuming that you have the right plate material that is compatible with your ink & other chemicals used on and around the press there are a number of fundamental practices that should be followed at all times with all types of photopolymer plates. Probably the single factor that most printers fail to observe is to not allow ink to dry hard onto the plate during and after use. During the run and in particular with solvent and water based inks when the ambient temperatures are high ink will begin to build up on the leading ad training edges and in between screened areas so they need to be scrubbed, in between reel changes and particularly at the end of a run. Dust and other contaminants can also build up around certain areas of the image particularly fine screens and if left to harden can cause the raised image to become brittle and if not removed before running can result in the image area being sheared away from the base of the plate. Build up on the floor of the plate, leading edge and trailing edges while not necessarily detrimental to the plate can also cause ink to be transferred to the web. You should always consult with your plate supplier as to what solution to use to clean your plates and use a soft bristled brush to minimize any abrasive effect to the face of the raised image. Using hardened bristled brushes and worn or damaged brushes and shop rags often result in causing a great deal of unnecessary damage to plates so ensure a good supply of clean brushes and lint free cloths at all times is essential. When setting impression between the anilox and plate cylinder, plate cylinder and substrate always try for a kiss impression. Excessive impression between either areas of the print chain can and will cause premature wear and damage to any plate in particular thinner caliper plates. Making sure that you have the right tape to plate combination can not only reduces dot gain and improves graphic quality but again will also enhance the life of most plates . If you can leave your plates on the original sleeve or integral plate cylinder this will lessen the chance of the plate being damaged during removal by the operator. If they have to be removed from the sleeve or plate cylinder great care must be taken to not damage the plate , after which it should be thoroughly cleaned & dried before storing preferably in a hanging folder with a foam or silicon paper inter layer between each plate with the image to the polyester backing of the next plate. Plates should not be put into envelopes and piled one on top of another. Neither should any object of any weight be allowed to press against the plate for any length of time. If the plates have been left mounted on the plate cylinder it must be supported such that the plate is not touching the wall of a storage box or core that it may be stored in for protection purposes. Plates should always be protected from high ozone atmospheres, direct sunlight and excessive heat and cold. Either a dedicated person should be used to ensure that plates are properly cleaned, stored and inventoried after every run or sufficient time given to the operator to do it themselves. Unfortunately in my experience neither option is implemented very often and plates are only cleaned halfheartedly and put away if at all in the manner that I have recommended. So if you want to maintain and enhance the life of your plates during and after the run you must implement good housekeeping practices and hold all involved totally accountable when it comes to maintaining and storing your plates in an acceptable manner.
Platemounting tape tips and overview
It is fairly well established that ‘foam’ adhesive plate mounting tapes can dramatically improve flexo print quality.
It is fairly well established that ‘foam’ adhesive plate mounting tapes can dramatically improve flexo print quality. With the development of thinner polymer plates further growth is now expected as their performance relies
even more on effective mounting and the integrity of the compression characteristics of the mounting tape used – writes Alan Harris.
Richard Eeles of Beiersdorf UK tesa Division, says that not so long ago, the industry standard thickness for polymer printing plates was 6.35mm and adhesive plate mounting tape was designed accordingly. Today, technology allows the manufacture of photopolymer plates just 0.76mm thick. These
deliver significantly better individual dot characteristics and offer the potential for even higher quality printing of combination half tones and line work across a whole spectrum of substrates at lower prices and with
faster production times. Thinner plates use less material and cure quicker so costs are reduced.
In the label printing sector thinner plates have proven popular where they have eased the problem of fitting plates around the smaller cylinders used on machines. Now the technology is being adopted in the carton printing
Originally, thicker foam tapes, or cushion mounts as they are often called, were also employed to solve spacing and packaging problems on certain machines where varying set up tolerances and printing plate variances had to
be accommodated. Eventually, along with old ‘hard plate soft tape’ and ‘soft tape hard tape’ rules, these applications will become dated as the latest precision printing machines replace older equipment.
Flexo ’99 witnessed the European launch of tesa’s ‘Big Foam 60 thou'(1.5mm) product developed especially for printers who mount ’67 thou’ printing plates. Eeles says that this heavyweight tape affords secure mounting free from air entrapment and is claimed to be very stable. Such is
its strength that it obviates the need for the polyester backing used to prevent stretching on its thinner cousins.
In common with all ‘foam’ tapes, tesa’s Big Foam helps to minimise dot gain and deliver enhanced print quality, particularly when combination screened images and solid areas need to be printed accurately alongside one another.
Tom Viser of Scapa Tapes says that the huge interest generated by flexographic printing over the past few years is in part attributable to improvements that have raised quality standards. These include inks, plates
and paper quality. Of equal critical importance however, is the way plates are fixed to the cylinder prior to the commencement of the print run. While the plate needs to be repositional before printing begins, it must also
remain resolutely in place during high speed print runs. With such paradoxical demands, it is essential to pick a plate mounting tape with the right performance parameters.
What tapes have to offer
Scapa say that double sided tapes used to fix plates to the
print cylinder,are typically made up of four layers:
o Rubber adhesive on the cylinder side
o High density PR- foam backing
o Film backing
o Acrylic adhesive on the plate side.
Specific printing jobs may demand particular technical tape performance but as a general rule, printers need to consider the following criteria:
o Good rebound to compensate for inconsistencies in the system
o Clean removeability in one piece to avoid time spent cleaning machinery between print runs
o Excellent adhesion and shear resistance
o Easy mounting, repositioning and demounting.
Scapa flexographic plate mounting tapes are specifically engineered with a compressible foam layer to compensate for variations in plate and/or cylinder thickness. They can generally be used to mount both rubber and photopolymer stereos onto steel or rubber covered cylinders. In effect,
using foam mounting adhesive tapes mean that it is the foam that compresses rather than the printing plate itself during the printing process. The foam ‘bounces’ into any gap between the plate and cylinder. The result: clean,
sharp images and excellent contrast.
Providing the performance required by flexographic printers today depends on foam density, together with consistent foam thickness. ‘Foam quality is the real differentiator,’ according to Viser. ‘The foam must maintain a
consistent thickness as an even cell structure will promote even compression and good recovery throughout the print run.’
To achieve the required density, the foam layer is generally compressed. Compression can destroy the foam morphology however, resulting in dot gain. This is why Scapa has invested heavily to grind the foam layer in its own manufacturing plant. The foam is carefully ‘shaved’ to precisely the right thickness, preserving the basic structure. The result is tight tolerances of
+/- 4 microns.
Just as important as the structure of the foam is consistency of thickness. With precise thickness across the width of the tape, end print quality is improved. Many tapes incorporate extra thickness to ensure that the foam
meets the minimum requirements. Infrared testing in process can be used to ensure that every single millimetre of the foam meets the right thickness requirements. Precision testing implemented by suppliers guarantees tighter
tolerances than the norm.
Pick your tape
Printers face a huge choice of foam mounting tapes and selection can be daunting without a clear understanding of how different products perform.
For printers who prefer to stock just one tape Viser says that Scapa 4355 is a 20 thou tape that offers a good all round solution. It is said to provide optimum results on half tone printing and high speed block printing. For
label printing, Scapa 4399 15 thou tape can be used. A 60 thou tape is also available for use on non-standard plate thicknesses or older equipment. 3M is a leading player in the production of plate mounting tapes. The company¹s products include 3M Flexomount and Cushion-Mount Solid Printing Tapes. According to 3M United Kingdom PLC, the caliper control and advanced adhesion of Flexomount makes it ideal for applications requiring maximum ink
density and minimum pin holing.
Ideal for both rubber and photopolymer plates, this vinyl-carrier tape is said to deliver consistent holding power yet peels off easily without leaving a residue when the job is done. Amongst 3M¹s Cushion Mount solid printing tapes is 3M 949. This 0.50mm tape has a differential adhesive system on a high-density elastomeric foam. The
non-liner side has a rubber resin adhesive, while the liner side uses an acrylic formulated adhesive. This product is ideal for rubber plates and helps to reduce cylinder bounce at higher speeds. 3M¹s 933 (0.38mm) and 939 (0.50mm) are suitable for photopolymer plates.
Characteristically they have a rubber adhesive on each side of high density elastomeric foam.
Other products from 3m include Cushion Mount Plus Process printing tapes; Cushion Mount Plus Firm Combination printing tapes; Soft Combination printing tapes; Standard Combination printing tapes, and the Thin Tape range.
3M also produce Cylinder Mount Build Up tapes. Thinner plates can enhance printing quality but in the past, they often required an investment in new cylinders, gears or sleeves or a change in plate mounting tape thickness.
The Build-Up tapes are said to provide printers with a more cost effective solution to the problem of meeting press undercut and pitch diameter requirements when using thinner plates.
Carrie Houghton of Davies Tapes says that liner caliper can make or break the efficient mounting operation. Thin improperly coated liners cause air
pockets to form between the mounting tape and cylinder. This can happen while the tape is being applied to the cylinder or while the liner is being removed from the tape. These air pockets can go undetected until a kiss
impression is applied on the press. Heavier silicone treated liners maintain adhesive integrity prior to and during the mounting operation and provide excellent release characteristics without tearing.
Davies Tapes provides a number of its products with embossed, structured or creped liners to overcome this problem. Tapes incorporating these features
include F10E, F15, F20 and F25.
While technical advances in flexographic printing are enabling printers to produce award winning print results, it is important not to neglect the role of any of the components in flexo¹s success, including plate-mounting tapes.
Are their any benefits to using peristaltic type pumps over diaphragm & centrifugal pumps?
There are many benefits when using peristaltic pumps in that they are low maintenance having no valves or seals, there is no contamination, no corrosion, they do not cause cavitation or bubbling and clean up of a peristaltic pump compared with a diaphragm or centrifugal pump is about a third of the time.
Peristaltic pumps are also capable of handling low to high viscosity inks, coatings and adhesives and deliver near constant flow rates regardless of the print deck heights.
I have a very simple question, how do I calculate the cut back of a print cylinder to allow for my tape and plate?
You are right it is simple but you will be surprised when I tell you that many people get it wrong. What you must do is determine your finished diameter for the circumference that you intend to print so for instance if you have a 12” repeat divide by Pi ( I tend to use 3.1416) =3.820”
Then multiple your plate and tape thickness by 2 so if your plate is 0.067” and your tape is 0.010” add them together and multiply by two ie 0.077 x 2 = 0.154. Now you can simply deduct this number from your finished diameter so 3.820” less 0.154” = 3.666”.
You now have your undercut diameter for your print cylinder but remember if you are mounting you plate on a sleeve you will have to deduct the thickness of the sleev x 2 as well.
Do make sure that your plate cylinder is perfectly parallel and has a hardened polished surface to be able to withstand the punishment it will sustain throughout the process of having plates and mounting tape repeatedly stuck down, removed and cut on it.
I have a very simple question, how do I calculate the cut back of a print cylinder to allow for my tape and plate?
You are right it is simple but you will be surprised when I tell you that many people get it wrong. What you must do is determine your finished diameter for the circumference that you intend to print so for instance if you have a 12” repeat divide by Pi ( I tend to use 3.1416) =3.820”
Then multiple your plate and tape thickness by 2 so if your plate is 0.067” and your tape is 0.010” add them together and multiply by two ie 0.077 x 2 = 0.154. Now you can simply deduct this number from your finished diameter so 3.820” less 0.154” = 3.666”.
You now have your undercut diameter for your print cylinder but remember if you are mounting you plate on a sleeve you will have to deduct the thickness of the sleev x 2 as well.
Do make sure that your plate cylinder is perfectly parallel and has a hardened polished surface to be able to withstand the punishment it will sustain throughout the process of having plates and mounting tape repeatedly stuck down, removed and cut on it.
There are a lot of blade materials available today, what factors do I need to take into account when trying to decide what will work best for me?
This is perhaps one of the most debated questions in every flexographic market today. It is a question that is asked in every area of flexographic printing, but there are some basic questions you need to ask yourself when setting off down this path, and are as follows:
- What surface will the blade have to wipe against? – for example chrome or ceramic.
- What ink/coating system will you be using, such as solvent,water based or UV.
- What viscosity will you generally be running at?
- What line count will you have on your anilox?
- What volume of ink will your anilox be carrying?
- What print length do you intend to run?
- Is employee safety an issue when handling the blade?
- Is it a single blade or chamber blade set up?
- How clean of a wipe must you have?
- Will it be running in a corrosive environment?
- How abrasive is the ink or coating that you will be running?
- What speed will you be running at?
- How skilled are your operators?
- What quality of graphics do you intend to run?
Quite a list I am sure you are thinking and truthfully not everything that could be asked for every application but if you have made the right choice of vendor they will be only to willing to provide the best advice, you just need to ask for their help.
Can you tell me what QR codes are and how we can generate them?
The letters QR stand for Quick Response as they can be read quickly by a cell phone user. Originating in Japan they are becoming very popular all over the world. The US has taken to them so much so that we are way ahead of Europe in terms of overall interest. Although generally seen in only black they can be printed in other colors as long as there is enough contrast for them to be read. The reading devices are QR code reading programs that you can very quickly and simply download to your cell phone in most cases for free. The sites that offer the readers also offer the ability for you to be able to generate the codes that can also be downloaded and printed in almost any format you care to think of. They can also be printed very small or large enough to fill a bill board. The codes allow for almost any information to be seen by the reader from text, to video, movies, product data, contact information, events, the list is only limited to your imagination. They are suitable for large and small businesses and although not everyone may reach for their phones to nap them they are coming, even the USA today newspaper has one on the front page. You could even add one to your business card with all your contact information saving the customer having to enter all your information into his phone with just one or two clicks. It was reported recently that in a subway station in Seoul, Korea they have virtual displays of food with QR codes that gives them the ability to view and order their shopping while travelling and then have it delivered right to their door just after they get home. It seems that they like other codes such as Microsoft tags are not only here to stay but are likely to morph into even more ingenious marketing tools, and just as we were all getting used to UPC barcodes!
Is there one printing plate that will suit all my needs?
Well the simple answer is No, but I am sure you all ready knew that when you penned the question. Yes, there are plates available that are able to handle a wider range of demands, but with so many variables to be taken into account it is unlikely there will ever be one plate to suit all your needs, unless of course you are printing the same job, on the same machine, with the same ink on the same substrates.
In today’s competitive market place and buyer demands the reality is most printers have to take on what ever work the salesman brings through the door, be it 4 color process, solid & line work or screens in excess of 175lpi.
The good and the bad news is that there is a wide range of solid and liquid plates available for the printer to choose from and most reputable suppliers will be only to willing to help you to make the right choice for your unique application.
What is the best method to clean my anilox rolls?
It would be to easy to say good old fashioned “elbow grease” was the solution ie : manual scrubbing of the anilox, but to some extend there is some truth in this statement. Manual scrubbing with the right type of brush, in combination with the appropriate cleaning solution, can and will help to get an anilox roll clean. If you note, I did say “will help” but the truth is that while manual cleaning does just that it is not efficient, is hugely labor intensive, and absolutely cannot get into the bottom of the individual cells where the real hardening of the ink and coating is taking place.
The solution has to be and is mechanical cleaning, but before you say eureka there are several options to consider.
These include Ultrasonics- this method can only be done off press and uses sound waves to implode microscopic air bubbles in a tank of heated liquid which very quickly and efficiently can clean all sizes of rolls. This method is very effective and generally only needs short cleaning times for most rolls.
Media Blasting- this process uses an abrasive medium that is blasted at the roll surface, and again is done off press. Rotational speed, dwell time, air pressure, traverse speeds need to be carefully monitored at all times.
Baking soda cleaning- Similar to the media blasting but utilizes baking soda as the cleaning media but can be done off and on press. Same consideration needs to be made to speeds, rotational, traverse and blast pressure as media blasting.
Cyrogenic cleaning- A very environmentally friendly process that uses dry ice pellets to remove the contamination from the roll surface and cell structure, but cannot reach into the smaller cell engravings. Air velocity is a serious consideration. Can be done off and on press.
Laser cleaning – A very high tech cleaning method that can be done off and on press, thermally ablates material from engraving but can be slow.
We are offset printers but are being told by many buyers that flexo is simpler, cheaper and can match our quality, I do not agree but have no real flexo experience, so who is right?
I was very interested in your article concerning the handling and storage of engraved and coated rolls, but what about sleeved anilox technology?
Why is it so important to control ink viscosity, and if so how do I control it?
Can you help me better understand the differences between CMYK, HexachromeTM and Opaltone TM color models.
There are a lot of blade materials available today, what factors do I need to take into account when trying to decide what will work best for me?
Can you explain when I should use flexible dies and what if any benefits/disadvantages do they have over solid dies?
Is it really worth the cost to switch from conventional plates to digital direct to plate technology ?
What are the benefits of printing with UV inks?
Almost everyone seems to be talking about RFID technology, what exactly is it? And does it have as much growth potential as everyone seems to be saying?
To begin with RFID is an abbreviation for Radio Frequency Identification and has been used since the early 60’s but as you say is being talked about by everyone now..
It usually consists of a transponder that can be implanted or attached to a wide variety of products, equipment and critical documentation.
The technology ensures easy identification of a product and has become very important for inventory management of materials and products in many industries including our very own.
Perhaps the largest growth market is in the security market where even documents can have the “tag” as the transponder is also know embedded into them to prevent removal from a particular area.
The tag is really a very small microchip with an antenna fitted to it, which can be implanted in a wide variety of materials that is dictated by its use.
There are three forms of tags, active, which has a battery attached to it and allows it to transmit to a reader, semi active, this has a battery that feeds the microchip but requires additional power from the reader and passive, which depends on the magnetic field sent to it from the reader.
It was probably Wal-Mart that started the push towards RFID when it demanded that its vendors be able to provide product with RFID identification in the majority of its products for easier inventory management, warehousing and identification.
The RFID tag comes in two formats, the first only gives the product a unique identification code and the second allows information also to be written to it via a hand held reader. Although similar to barcodes in some ways the RFID tag does not have to be scanned optically but communicates by radio waves and can transmit through paint, ink, dirt and any other non metallic materials.
In the label industry there is a large growing market for security labels and smart labels and has helped to significantly reduce theft for many stores and has become particularly popular within the pharmaceutical industry to help prevent counterfeited drugs, even libraries have got in on the act for their books.
The newest format is chipless technology which is where the real excitement is today for many printers as these use chemical particles that have varying degrees of magnetism and only become active when exposed to the electromagnetic reader.
With the varieties available a binary code has been created which when printed onto a substrate even allows barcodes to be printed than can then be scanned from several feet away. It has huge potential for governments and will no doubt be used for printing of currencies to help further reduce counterfeit money for example.
So does it have growth potential? all I can say is we haven’t seen anything yet as I believe with the development of new ink, reader technology and materials that this product will find even more uses in all markets including our industry particularly for inventory control of pallets, reels of paper, printing rolls, ink , product tracking, to name but a few.
We seem to damage our anilox and other coated and engraved rolls far too frequently can you give us some general guide lines as to what we can do to reduce this from happening as frequently?
Clearly engraved cylinders are very valuable, so taking good care of them is very critical and yet as you say many rolls have to be replaced due to mechanical damage generally caused by mishandling. As there are many different areas that rolls are handled I have broken my answer down into several sections, and to be fair damage may not always occur in your facility as I will explain.
All rolls should be inspected for any damage that may have occurred during shipping.
Check the crate for external damage initially as this can be an indicator to possible damage to your roll and then open up the box and check to see if the roll has moved or suffered any impact damage. Any obvious damage should be stated on the shipping paperwork and if possible corroborated by taking photographs.
When boxes are dropped journal supports can often collapse so it is important to check if the roll surface has dropped onto the floor of the box. In the case of rubber rolls this can cause flat spots and although other coatings can result in fracturing of the coating or destruction of the engraved surface if applicable.
Removal from the box
Great care must be taken when removing your roller from the box as it is at this point that many rolls are inadvertently damaged due to the use of incorrect lifting slings such as very narrow slings or chains both of which can be very damaging to most surfaces.
Generally most rolls should be lifted by the journals although in some cases this is not possible and a wide lifting belt can be used. When lifting from the journals always protect the edge of the roll with appropriate packing material from the pressure of your lifting straps. Both compressible and rigid coatings can suffer severe damage if the roll edges are not adequately protected at this and each stage of lifting your roll.
It is vital that all personnel who are required to handle any rolls understand how even the most robust rolls can be damaged as a result of inappropriate handling from arrival in your warehouse to storage and installation.
Good sturdy packaging is essential for shipping and storage of your rolls.
For most rolls wood is the general packaging of choice, although when shipping into Latin America and other international destinations wood free packaging is now being considered, rather than heat or chemically treated wooden packaging.
It is essential when building any box that you allow enough room to ensure that the surface of the roll does not touch the inside walls of the box and to also allow sufficient room for lifting straps or belts to be placed around the core or journals.
I generally suggest plus 4” on top of the finished roll diameter to allow adequate clearance for access with lifting straps etc.
To maximize the performance and life of any roll it is advisable to adopt a good preventative maintenance program for all rolls in all machines.
Before start up and at shutdown all rolls should be inspected for any obvious surface defects including routine inspection of journals and bearings for potential fatigue or necessary lubrication or bearing replacement as may be required.
Flat spots or other impact damage should be investigated immediately in an attempt to minimize the problem and to ensure that all set up and operational procedures are being followed rather than let the problem become more severe.
Nip pressure and load weight should be removed from all rolls when machines are not in operation and in the case of doctor blades and chamber systems they should be backed off from the anilox surface when the anilox is not turning.
All rolls should be cleaned with your vendors recommended cleaning solutions and equipment to help maintain the performance of your roll and in the case of your anilox its ability to pick up and transfer the volume of coating or ink that it is meant to carry.
Alignment and gap control in the case of glue applicator rolls is vital not just at installation but at each start up to ensure that your coating or ink is being transferred evenly across the web or other substrate , and to prevent inappropriate contact pressure that may cause mechanical damage or inappropriate metering of your coating or ink.
Print cylinders with plates directly mounted to them should be scrubbed clean and finally and allowed to dry before wrapping with a stretch wrap material to reduce plate lift and a impact resistant cover that is light proof . Clearly they must be stored without the plate surface being in contact with anything else during storage.
If you do not intend to use your roll immediately it is sensible to leave it in its original packing case to reduce the potential for accidental damage.
Rolls should be stored in a dry environment that is not prone to extreme temperature changes, ozone or exposure to direct sunlight. The last two elements are particularly important where rubber rolls are concerned although extreme temperature changes can and do affect all types of rolls. Many rubber compounds actually freeze at approximately 34° F and as most compounds lack hydrolytic stability they may swell or deteriorate due to prolonged exposure to moisture or high humidity.
Moisture can and does cause severe corrosion of all steel surfaces and as a result can undermine many surface coatings.
Most forms of light and ozone will cause surface oxidation on most compounds which tends to appear as a white or grey powdery build up, and if left for to long will affect the performance of the compounds physical properties. Wrapping the roll with a light proof paper and avoidance of areas where machinery, generators, or other electrical equipment are used will also reduce rolls to excessive exposure to ozone.
All rolls will also benefit from being rotated 180° every 3 months or 90° every 30 days to help prevent rolls developing excessive TIR or sag.
Can you explain the benefits I can expect by maintaining my anilox cell volume?
By maintaining your cell volume you will:
- be able to maintain a constant ink formula
- reduce your ink costs
- reduce doctor blade wear from dried ink build up on the roll surface
- improve print quality and consistency
- reduce scrap levels
- increase machine speeds
- improve the longevity of your anilox
- maintain color density maintain coat weights
- reduce machine downtime
- reduce labor cost
- reduce your make ready costs
We have just bought our first printing press, what are the general safety guidelines that we should follow around a printing press?
As with any industrial equipment there are many components that can be hazardous to an operator and not just the press itself.
The following are some of the more key points that I would suggest you
Basic safety equipment and clothing should be used and mandated by your company so that every person on or around your machine at least takes the most basic of precautions such as steel toe capped shoes with soles that will prevent slipping, safety glasses, ear plugs, hair nets (long hair must always be tied back). No jewelry of any kind should be worn and if you can afford it I strongly recommend that you provide work outfits for your operators to wear. You might think this extravagant but the danger of wearing loose or other ill fitting clothing or clothing made from inappropriate materials is well worth the cost when compared to having to replace some one permanently or even temporarily if they have been injured due t wearing the wrong clothing that might get caught in a moving part of the press. If your operators do not wear gloves all the time they should be encouraged to wear cut resistant gloves when cleaning or changing doctor blades. They should also be encouraged to use a barrier cream on their hands and finish by washing their hands with an appropriate hand cleaner & moisturizer. Making sure every operator knows exactly where all the nip points are on any equipment and of course where the emergency stops are located. Your operators should be encouraged to keep the general press area clean and to wipe up any spillages at all times. When cleaning or washing any press component rubber gloves should be provided and used at all times. Starting up a press all operators should be encouraged to shout out clearly that he is about to start the press and that it is his responsibility to check that everyone is clear of the press before he starts it running. Cloth rags should not be used anywhere near any nip points in preference for lint free paper wipes or brushes with handles that allows the operator to stay clear of the nip point. Safety knives should be provided to help minimize potential cuts from older style box cutter knives and certainly loose blades should not be used at any time. Where operators have to go under larger pieces of equipment or there are any significant overhead elements that may result in them banging their heads on then hard hats must be provided. Every operator must be taught the correct lockout procedure and be provided with the appropriate locks when repairs must be carried out in and around the press that may be hazardous to the person involved. I recommend frequent safety training and frequent refresher courses for all personnel at all levels.
Can you please explain what causes score lines on my anilox rolls?
Even when using ceramic anilox they are still prone to scoring which can be caused by a number of things. Ceramic is certainly more resistant than a chromed anilox and in most cases it is only the surface of the engraved ceramic but this alters the surface characteristics and will show as a light or dark line on your substrate.
- Contamination in the ink – this could be caused by hardened particles of ink or resins clumping together and then getting trapped between the blade and the surface of the anilox. It can also come from metal particles that can get into the ink or other metal objects such as screws, washers or bolts.
Much of these elements can be overcome by have rare earth magnets and stainless filters in your ink line.
- The doctor blade- misalignment of the doctor blade, to much pressure, wrong angle , leaving dried ink on the tip of the blade and running the blade against the anilox when it is not properly inked up are all know to cause scoring of the anilox.
Clearly making sure your blade, blade holder and chamber are all correctly aligned will solve most of these issues. As will making sure you have the correct angle between 30-35 degrees and making sure that the blade is not overly pressured against the face of the anilox will also help. Stainless steel blades are also prone to splintering so should be avoided in most cases. Plastic blade tips can also soften and allow particles to become embedded in the tip of the blade which again can score the anilox.
- Roll edge chipping– if the coating on the edge of the anilox roll is chipped and the roll is not repaired or replaced then the ceramic particles will get into the ink and can again become trapped between the tip of the balked and the ceramic surface. It is imperative when a roll is chipped that you plug the damage with a liquid metal material to help slow down the process of the chipping or replace your roll. It is also important that the operator is encouraged to inform their supervisor of any rolls with chipped edges so that they can be removed from the press and the ink also disposed of if the chipping is seen after a run as this will mean the ink will be contaminated with ceramic particles that cannot easily be removed with filters and being inert can not be pulled out with magnets.
We are constantly having problems with scoring of our anilox rolls can you explain what the likely cause is and how we can prevent or reduce this issue?
Second only to plugging of the anilox, scoring is the next most common reason for anilox having to be replaced. Score lines can consist of deep gouging lines, shiny polished lines and lines that just don’t appear to print properly. The deeper gouged lines are usually the result of particles becoming trapped between the blade and the roll surface or burrs on the doctor blade itself. Contaminants such as paper fibre, dried ink pigment, nylon brush bristles & metal shavings are all responsible elements but can be dramatically reduced with the introduction of a filter in line that has a stainless steel mesh filter and rare earth magnet. Blade alignment, pressure and angle can all have a significant, and can dramatically increase or help to reduce the problem if the blade is correctly set up and replaced in a timely manner. Lighter shiny lines are usually caused by dried ink particles either in the ink or left on the lip of the blade. Starting the print station up with the anilox dry against the doctor blade will clearly make the issue wore. Solid non printing lines are usually caused by particles of metal or ink trapped in the cells and need to be scrubbed out or ultrasonically cleaned. So to help prevent and reduce scoring always filter your ink both during the run and when returning it to the shelf, ensure your blade is correctly set up, never run the blade dry against the face of the anilox, use a good quality blade to reduce burrs occurring, replace your blade frequently, not just when you see a scoring problem because then it is too late and you will have to replace your roll.
We have been having problems with our end seals on our chamber blades for years and have tried many different options but with little or no improvement, what are we doing wrong?
The problem with finding the most suitable seal for your specific chambers is that there are so many variables. That said there are some key elements that you need to consider when trying to determine the best choice to suit your needs. The first is to find a reputable supplier with plenty of experience with seals and preferably one that can fabricate them for you. There are a wide range of materials from foam, felt, neoprene, rubber , plastic for example. Choosing the cheapest such as foam may not be the solution for everyone but for some it may work just the same as the most expensive may still not be the answer so using a qualified experienced supplier can save a lot of headaches, and unnecessary trials. Seals must be flexible but rigid enough to hold their shape and maintain the necessary seal between the roll , chamber and blade to minimize any leakage. Even the best seals will have some minor leakage from time to time as they wear. Lubrication can be key to helping extend the life of most seals; felt usually comes presoaked in petroleum jelly although it is always worth having some food grade lubricant at press side if you feel the seal is not lubricated sufficiently. It is well worth cleaning your chamber and installing the initial seals out of the press to be able to check that your seal is fitting without being distorted due to a size or shape issue , before putting it in the press and running it .Bear in mind some inks and solvents can be very aggressive on seals ,and if you have got older chambers they may have all warped slightly or been damaged during cleaning so all these factors must be taken into consideration with your supplier before making your final decision. Of course your decision should be easy, it’s the one that works , not the cheapest or the most readily available or from Fred because he’s local, it’s not rocket science just common sense.When you work with the right supplier I am sure they will very quickly help to determine what you have been doing wrong.
Every printer I talk to these days seems to be using sleeves in one form or another; can you briefly describe the benefits of using sleeves in a flexo environment?
Sleeves have been around for a long time, although it has to be said that Europe embraced this technology significantly earlier than North American market and whereas ITR (in-the –round) digitally imaged sleeves are only just gaining traction here in the US again in Europe it has been widely accepted for twenty years or more. Sleeves are lightweight and mostly come in parallel form although tapered sleeves were the standard for many years. They come in a multitude of wall thicknesses so really help to accommodate variations in plate and tape thicknesses although I really question the inch thick plus walled sleeves and their long term viability. Being able to mount plates directly on the sleeves and leave them mounted if preferred for repeat runs dramatically reduces repeat mounting and allows for easy storage. When used for anilox sleeves it allows for anilox line counts to be changed rapidly and again minimizes storage costs and makes handling of them easier. For jobs that have continuous backgrounds, diagonal repeats or where you want to stagger the individual print lanes to reduce bounce sleeves again are the perfect solution. For presses with fixed, cantilevered mandrels print sleeves and anilox can all be changed in minutes by an individual operator in many cases with no lifting equipment needed unless you are running very wide tissue or wide web sleeves. They can also be rubber or polymer coated for laser engraving, ground for flood coats or digitally imaged in the case of polymer coated sleeves.
Can you recommend how we should be storing our plate and anilox sleeves, and are there any particular procedures we need to carry out before storing them?
It is generally recommended to store sleeves vertically by most manufacturers and not on poles or in boxes horizontally. If you store your sleeves on poles that are horizontal this can lead to sleeves becoming oval shaped over time. The same can apply to sleeves stored horizontally in boxes and in the case of plate sleeves with plates still mounted on them if the sleeve is not kept from resting on the bottom of the box it can also lead to flat spots developing on the plates. There are a number of modular systems for this very purpose that allow maximum storage in the minimum floor space and ensure that they are adequately protected at all times. Before putting sleeves away they should be cleaned inside and out to remove any contamination in the case of the anilox from the engraved surface itself and with the plate sleeve the plates should be wiped clean to remove any residual ink. In both cases great care should be taken to ensure that the inside of the sleeves are wiped clean to remove any moisture or other contamination. You should also inspect the sleeve for any impact damage to its surface, end face or the inner fiberglass sleeve itself such as scoring or splitting. If any scoring or splitting of the end rings or the fiberglass sleeve is seen then the sleeve should not be stored but should be considered for replacement. Sleeves are very fragile on the ends so great care should be taken when taking them off the air mandrel. Rubber matting should be on any floor area that the sleeve may have to be placed even if only for a few seconds. Ideally properly constructed intermediate storage trolleys should be used that are built to adequately support and protect the sleeve while being changed out or taken to the storage unit. In addition you should also make sure your air mandrel is clean at all times and that all air supplies are put through a drier and air filter to eliminate any moisture or oil getting into the cylinder and ultimately between he inner sleeve and the mandrel surface making the sleeve almost impossible to remove in some case.
Can you describe the different types available to printers today and the benefits that we might expect should we choose to use them?
Again this is another subject deserving of a much larger article but the following will give you a basic understanding of the options that are available to you and the potential benefits. Sleeves have been around for a long time and are used in just about every print market. When first introduced the inner diameter of the sleeve was tapered and although still available the vast majority now have a straight inner core. The straight inner diameter allows sleeves to be put onto a mandrel from either end but if pushed past the initial holes of a mandrel that are normally on one end only it can result in the sleeve getting stuck on the based mandrel. The tapered inner diameter sleeve is however less prone to moving compared with the straight bored sleeve. Sleeves are usually constructed of fiber-glass reinforced plastics or carbon fiber reinforced plastics. They can be coated with all types of elastomer and other polymer based materials. In their raw ground state they can be mounted directly onto with photopolymer or rubber plates using conventional sticky back materials. Sleeves are now commonly used with ceramic coated laser engraved surfaces to replace conventional integral anilox although this entails adding a compressible coating on to the base sleeve, then a thin walled steel or aluminum tube before being plasma coated, ground polished and laser engraved. While not simple to manufacture and certainly not cheap they do give the printer the ability to switch line counts & volumes relatively quickly both on and off press. Where much larger than normally diameters are needed and only one mandrel base is available sleeves can be mounted one on top of another in a “piggy back” arrangement. Other benefits for sleeves include lighter weight, making them easier to handle & store, when needing reworking. Where sleeves are coated and ground to size they can be used for flood coatings of varnishes, tints, adhesives and other coatings. They are cheaper to ship, and make changing from one elastomer coating or engraving much easier. Plates can be left on the direct mounting sleeves saving time in not having to remount plates. Finally ITR or in the round technology is now gaining favor in many areas with a continuous layer of photopolymer being added around the sleeve continuous images can be exposed and developed in the round. This eliminates the need for costly mounting time, guarantees perfect registration and will allow you to run faster as designs can be staggered reducing any bounce.
What determines when a spot color should be used verses building it from CMYK?
This is generally a question asked quite a lot in flexography even though 4 color process CMYK is used frequently, where solids and specific colors are demanded spot colors are generally preferred. Most commonly spot colors are used for corporate logos or other specific elements that dictate a particular shade, tone or vibrancy. It is a common fault in many files transferred from gravure or offset where colors are most commonly built with 4 col process and it is assumed that Flexo can do the same. Spot Colors as a rule tend to be used for all text to maintain legibility and to eliminate any mist-registration in the Flexographic process. It does demand that you are able to print more than 6 colors but as most modern presses are 8-10 colors it is not usually a problem and will guarantee much better quality print. It can be very difficult to print some finer screens with large solid areas for some printers and is usually overcome by separating the solid away from the screen even though they are intended to be the same color.
What is the best way to control & remove static build up on our press & other equipment?
Static build up on presses and other press room winding devices is inevitable when materials are separated quickly from one another, and in general terms increases as you run faster. There is not much you can do to stop it but it can be removed with a wide variety of equipment that can range from a simple piece of copper tinsel to sophisticated pin array ionizers and electrical static bars. Originally these bars had to be very close to the web but the latest systems can work as much as 36” away from the web and are particularly suited for unwind and rewind rolls. Tinsel while cheap is not particularly effective at removing lower charges and needs to be replaced regularly so while the more sophisticated active static control devices are more expensive to install they more than pay pack your investment with their consistency and reliability. Failure to remove static is just not an option when you consider the impact on scrap levels and coating and ink laydown and adhesion properties. One thing you do need to bear in mind is that the high voltage static elimination bars to get very contaminated and must be cleaned on a regular basis to maintain their performance.
We have been using a hard vinyl sticky back tape for mounting of our photopolymer plates which seems to work reasonably well. Our supplier has suggested we might try a softer tape but it is more expensive what are the benefits to doing this and what other options are there?
There is no doubt that hard vinyl tapes can be and have been the workhorse for many printers for many years. They are certainly the lowest cost and the original modern mounting tape but if you are printing anything other than just solid and line work they will do little to enhance your print quality.
Softer tapes are usually of a foam construction and come in a wide variety of densities. The choice of density depends mostly on the graphics that you are trying to print and help minimize dot gain and still achieve good solid print as well. These tapes have a much more complex construction than the basic solid vinyl tapes and also come with a combination of adhesives and liners that can help dramatically improve your print quality and the actual mounting and demounting of your printing plate.
Many thicker cushion mount tapes are used to build up cylinder diameters where plate caliper has been reduced which is becoming more common as printers move to thinner plate technology but do not want the cost or rebuilding or replacing their existing plate cylinders. There are a wide variety of thicknesses that will suit all plate, sleeve and print cylinder combinations. There are tapes made specifically for fiberglass and other carbon fiber sleeves again to help ensure good repositionability and to minimize the amount o adhesive residual on the sleeve when the plate is removed. This applies the same for steel print cylinders as well. Many liners now have a grid pattern or other patterned structure to ensure that air is not trapped under the tape when it is being applied to the cylinder.
Softer cushion tapes not only help reduce dot gain when the plate is being compressed but also help mask other small defects found on most older plate cylinders and sleeves. That said you need to ensure that the tapes you buy have a consistent caliper the better tapes are ground to ensure caliper control, this is something you should check with a micrometer from time to time. A good cushion tape should have good compression and good recovery throughout your print run. Your vinyl tape has little or no give other than the thickness of adhesive and certainly has no recovery.
Because of their superior engineering soft/cushion tapes are general more expensive than vinyl tapes just as your supplier has said but in my opinion are worth the extra cost up front based on the benefits that you will see throughout your print runs and extended plate life that you will also be able to enjoy.
Is it true that paper can be made from stone, is it totally wood free, and is it as good for the environment as the manufacturers are claiming?
Stone paper or rock paper,as it is generally know is made from Calcium Carbonate (CaCO) with a small quantity of a non-toxic resin, usually (HDPE). The Calcium Carbonate comes from limestone and is ground p down to a fine powder like chalk with the resin acting as a binder. Once combined they make a tough, durable paper that is both water and tear resistant. It is totally wood free and can be recycled. As I understand it, it needs no water in its manufacturing process and no bleach and uses much less energy than virgin recycled pulp. Stone paper is photo-degradable after 14-18 months. They are seen by many as a good alternative to synthetic and polypropylene films due to their water, grease, tear and weather resistance. Calcium Carbonate is found all over the world and is often a waste product from other mining processes making it readily available and affordable. One last point being made of stone it is heavier than a comparable paper of similar thickness.
We had some printing issues recently and my ink technician mentioned that we might have some surface tension issues, can you explain what surface tension is, how does it affect the quality of our printing, and what does the term dyne level mean as well?
Surface tension is a property of the surface of a liquid ink or coating caused by cohesion of like molecules. Surface tension issues are a common cause for concern for anyone that is working with inks or coatings in getting them to transfer readily from one surface to another. It is this factor that may be responsible for the comments made to you by your ink technician that he may have observed with your ink or coating. Since the molecules on the surface of the ink or coating are not surrounded by like molecules on all sides, they are hopefully more attracted to the next surface in the ink/coating chain found in the flexographic process. Starting with the ink or coating, wiper roll, ink or coating, anilox, ink or coating, printing plate, ink or coating and finally the substrate. At each point of contact for the ink or coating if the next surface has a lower surface tension than the liquid and it may have difficulty in transferring to the next stage of the process that ultimately ends with the substrate, this is often referred to as critical surface tension differential. Converters have struggled with getting the perfect combination of each of these factors correct since print and coating stations were invented and can still be a cause for concern today even with all of our capabilities and print quality that for some seems effortless and for others can be a nightmare. Another term that may have been mentioned is wettability or wetting. This is the actual process when a liquid spreads on a solid substrate or material. Wettability can be estimated by determining the contact angle or calculating the spreading coefficient. Wetting or spreading of a liquid on a solid surface or material depends on the solid surface properties as well as the liquid used. One of the first surfaces that the ink will come into contact with is the wiper roll. If there is a significant difference between the critical surface tension and surface tension itself the more difficult it will be to get the ink to transfer uniformly to allow and even transfer of your ink or coating. It is one of the reasons why wiper rolls have been eliminated by many from the printing station as the rubber roll ages and hardens or oxidizes the more the surface tension properties of the roll will change. If you are using a doctor blade even then you will not escape the issue as even the doctor blade and anilox roll have their own surface tension properties and so does the printing plate and the substrate itself. Finally in terms of measurement surface tension is normally defined with the term dyne . The dictionary definition of a dyne is the value of surface tension of a liquid below which the liquid will spread on a solid expressed in dynes/cm. Most inks fall into the range of 25-40 dynes/cm , and as mentioned the lower the surface tension reading the better the surface wettability. The challenge for you and your ink technician is getting the ink and all the other elements to work together but as inks and coatings and surfaces all change during the printing process it is this factor that is the most challenging, and why many converters will ask the same questions as you have, but hopefully you will have a little better appreciation of what he his referring to in the future.
How do we decide what type of mounting plate to use with our plates to help minimize dot gain at the higher speeds we are now able to achieve?
With new press designs higher press speeds are indeed setting a new challenge for printers and mounting tape manufacturers alike. Conventional hard vinyl cheaper tapes may have been suitable for some at lower speeds but higher press speeds present a new set of dynamic issues that demands consistent compression and rebound capability of the tape to last through the entire run. Foam sticky back materials seem to struggle at higher speeds and new elastomer cushion and higher temp resistant adhesives appear to be able to cope better. There are obviously a wide variety of tapes each with their own features and with the many other variables on press it really means some due diligence on your s and your supplier’s part to try out a variety of tapes to help determine what works best for you with each plate material that you may be using. Inks, substrates, even plate cylinders all have a profound impact on the eventual dot gain you will see not forgetting the operators skill at setting the optimum pressure between the plate to substrate, anilox to plate, blade to anilox and even doctor roll to anilox. This evaluation all takes time , patience and perseverance as it is rare that you will be able to get the right combination from the outset. There is no doubt that the more experience your supplier has the better your chance of finding what will work best for you. Don’t be taken in by all the marketing hype by the many suppliers out there but instead demand that they work with you and help you find the tape that will give you the best performance. Do bear in mind that your prepress can have a profound impact on also helping to minimize your doubt gain by making the necessary allowances at the file separation and screening stage, not forgetting your anilox and ink supplier, so you must involve all of your suppliers inside and out if you what to achieve the best result and help you decide what is right for you.
Temperature and viscosity
I echo all of the other comments above. In water flexo ink, as the temperature of the ink rises, the water and amine evaporate or flash off more quickly. As a result, ink density get stronger and the ink film thickness that is transfered can also increase. This causes a host of print problems including dirty plates, dirty print and potential smearing. In addition, as ink gets thicker, chamber starvation can occur. Typically, when an operator sees this, he believes turning up the delivery pump (typically a diaphragm pump) will solve the problem. This only makes the matter worse because the diaphragm fatigues the ink to an even greater degree, causes it in increase in temperature, foam and increase the flash off of water and amine.
Let me add that with UV ink it is possible to begin the curing process if the ink gets too hot. We encountered this when our ink pans started to get around 130F. Not sure why they were getting hot, even the press mfg didnt know so our solution was to pump the ink.
The temperature has the major effect on ink viscosity and also depend on what type of ink you are using. Increase in temperature reduces viscosity for every ink and lower temperature decreases in ink viscosity.
Like in solvent ink increase in temperature will be loss in solvent which can causes many issue as well as viscosity can go down or can go higher if you loose lot of slovents and your print quality will detoriate.
In UV inks increase in temperature will reduce viscosity, which can have some effect on print quality because now your anilox might not carry that much ink but in some case little increase in temperature may help your print quality due to lower in viscosity ( like some time you put thiner in ink to reduce viscosity).
In water base increase in temperature most of the time will have neagtive effect on print quality as well as certain in can gel due to crosslinker and also some polymer may gel.
In this you can fill the cell of anilox also and your transfer of ink to substarte will be very poor.
The main effect of temperature is to change the viscosity of the ink. As the temperature rises the vsicosity will drop. this will effect the ink transfer process and the amount of ink transfered to the substrate. Thius will effect colour. If you monitor viscosity, for example with an automated viscosity control system you will see the viscosity drop as the temperature rises.
As many people monitor ink viscosity as a method of controling colour strength then you could be confused into thinking the ink was getting weaker, whereas in fact the colour strength is the same or because of solvent evaporation getting stronger (solvent evaporation will generally increase the colour strength). So it is possible if your ink is getting warming then the effect of these two processes (evaporation and temperature) will mask each other, making the ink appear to remain with constant viscosity, but in fact will be changing in colour strength as the proporation of solvent decreases.
For some research investigations we have used ink temperature to control the viscosity independently of the ink strength.
If you need more information, on our web site www.swansea.ac.uk/printing, under the research section there are lists of our published Journal and Conference papers (mostly in TAGA and IARIGAI) on the effects of temperature etc.
We also run a summer school for EFIA which includes ink characterisation and its effects.
Even though printing is a long established process, with thousands of years of experience, we have a saying in Swansea “If printing was that simple it would be rocket science”.
What are the deciding factors when trying to choose between thin walled rigid and flexible sleeves and bridge mandrels?
The most obvious factor is cost. Thin sleeves cost a fraction of the cost of a bridge mandrel but then again you will need air mandrels for the sleeves to sit on and will need a wider range to suit your various print repeats. For this reason many companies setting out on a sleeve program begin with bridge mandrels and thinner sleeves to help minimize the initial investment but often find at a later stage the cost of the bridge mandrel replacements to be very high compared with only having to buy thinner sleeves. They are also usually more readily available whereas bridge mandrels can have a significant lead time of months and not weeks with some thin sleeves also being available off the shelf. This can be critical when you are trying to win an order from a competitor. If you have many jobs with short runs then thin sleeves enable you to keep jobs mounted whereas bridge mandrels would be too costly in most cases. Thin sleeves mounted on a good quality steel base mandrel also tend to run truer for longer than a bridge mandrel/thin sleeve combination. Thicker rigid sleeves are more susceptible to splitting than flexible thin sleeves. Flexible sleeves however are the most competitively priced. So in general I would generally favor thinner sleeves with a wider mandrel range because in the longer run this initial larger investment will lead to longer term savings when having to add more sleeves and as mentioned thinner sleeves are also much more readily available from more suppliers.
What tooling would you recommend that I provide to my press operators?
This is a very interesting question and one that I am very familiar with when I am auditing pressrooms. It is also an area that almost every pressroom that I evaluate fails on as well, and yet is refuted by most managers and owners alike. What I mean by this is that most companies generally do supply tooling at press side for their operators but over time they get damaged, worn out, mislaid or just not put back where they came from. The net result is operators spend a good portion of their day looking for tools or trying to use what they have, which is usually not the right tool for the job. So before I make my recommendations please ensure that whatever tooling is provided is at the very least kept in clear sight on a shadow board for instance so that it can be monitored or in a lockable tool box or similar. Now back to the basic question tooling, for most facilities regardless of the press I always think of safety first for the operators so ear plugs, back braces, safety glasses, cut resistant gloves, safety knife , printers apron are the minimum for all press rooms to start with. From a quality perspective there should be a lupe, 100x illuminated scope, screen finder, pantone book, steel rule & flexible tape measure. No one expects an operator to be a maintenance engineer but a basic wrench set, metric & imperial allen key set, flat head and cross head screwdriver and pliers are all essential tools. Other useful tooling includes scissors, calculator, dyne pens, marker pens, stop watch, zahn cup, pH meter. Off press but certainly nearby you will need a densitometer and viewing cabinet for color matching. It may seem a lot but if you want to keep your press up and running and your operator at press side then you had better make sure that these items are readily available at all times. It should be noted that this is not intended to be an exhaustive list but rather a guide line it is highly probable that you will have your own additional unique tools that you may find vital for the maximum productivity of your press room.
When talking to different prepress people they all seem to refer to the overlapping of colors differently such as overlap, trapping, grip, under-draw, which is correct, and is there a standard amount that should be applied?
I agree there does tend to be a variety of terms used when running one color slightly under another to help hide any slight mis-registration during printing and the truth is they could all be used but generally the term when producing electronic files is trapping. In Flexography it is very difficult to butt fit colors together without having some mis-registration although more modern presses are remarkably accurate and the amount of trapping between colors is now very small compared to earlier flexo printing needs. As to how much to apply it really depends on the age of your press, operator skill and the colors that are required to butt up to one another although a black key-line can hide a lot of registration issues. Clearly if there is no key-line you have to be aware that trapping one color under another will create a line of another color which may not always be desirable so great care should be taken when producing the separations for all designs. Many software programs will apply trap between different layers of color automatically dependent on what parameters have been preset but care must be taken if there is only a very thin or no key-line on the original design, and should be discussed with your press personnel before final files and plates are made.
We are running with plate and anilox sleeves but are getting a lot of uneven wear to our plates and uneven print densities across the web can you suggest what might be causing these issues?
Most sleeves are built up of a combination of an inner carbon fiber or fiberglass sleeve, a compressible inter- layer and a final aluminum shell if it is to become a anilox sleeve, or again carbon fiber or fiberglass if it is to be a plate sleeve. It is this very combination of materials that generally leads to the issues that you’re asking about and the real issue which is run out that can only be measured with a dial indicator when pressed against the outer surface of the coated anilox sleeve or the outer wall of the plate sleeve. As each sleeve ages the inner layers are prone to delamination caused by hardening, softening, shrinkage, bond failure, or contamination from water, solvents and inks. This results in loss of concentricity between the various layers that will cause run out and in turn can lead to premature damage of the printing plate, doctor blade and will be seen visually in the printed product as uneven color densities or variations in the overall print quality of the job you are running. Unfortunately this problem can occur within weeks or months of installation dependent on how the sleeve has been run and has been handled. If the sleeve is dropped or knocked over this can cause distortion and delamination within the sleeve which will not only cause run out issues but may even prevent it being able to be slid onto the air mandrel, again the only solution is to replace the sleeve.
What are the benefits of printing with UV ink compared with water based?
Perhaps the most obvious benefit with UV ink is the quality of print that can be achieved. As there is little or no dot gain dots and text are much crisper and sharper meaning that you can print finer detail, cleaner for longer and more consistently than with water based inks.
It can be difficult to control water based inks viscosity and rate of evaporation as the press room temperature increases which will affect the color strength and likelihood of drying on the plate again UV does not suffer from any of these issues/
This means that it is also much easier to repeat the same quality from job to job and print combinations of screen and solids on the same plate.UV ink also tend to have a much greater gloss removing the need for another UV varnish which will give you another print unit that you could run. Generally UV has a much greater chemical resistance and also gives greater adhesion and scratch resistance.
Because UV does not dry on the plate or anilox inks can be left on press overnight saving time in set up the next day and also reduces the loss of volume firm premature plugging with your water based inks which is a major issue for all printers. Generally you will have less waste as your set up is much shorter with UV inks stability and should allow you to print faster with less ink being used as well.
Special inks such as metallic’s and fluorescents also have much better stability and color strength with UV.
You will also get significantly better ink mileage from your UV ink usually around 50% of the ink weight is needed to achieve the same or better density than with water based inks.
Talking with my ink supplier he mentioned that there are two types of UV inks , can you tell me what they are and if one is better than another?
Not that I am an ink chemist, but I believe your supplier was probably referring to free radical chemistry and cationic formulas. Free radical UV inks have acrylates and oligomers as their primary components, and are used in flexo, gravure rotary letterpress and offset coatings. They also have a photoinitiator that will allow them to absorb UV light energy to be able to form free radicals, which in turn starts the polymerization process. They also have other additives such as silicones, waxes and other inhibitors. Cationic inks use very different epoxy resins and other monomers as the primary components as well as a photoinitiator. They do have similar additives as cationic inks. Cationic is the most common system used because it has more capabilities and the raw materials are more readily available. They have better solvent , abrasion resistance and are more compatible with water based inks, Cationic inks are claimed to have better adhesion and although longer to cure do give good barrier protection, and it is claimed the base materials are less toxic.
One of my ink technicians mentioned the introduction of UV LED curing systems as having a number of benefits over conventional UV systems could you explain what they might be?
While UV LED curing may have a number of benefits its success will depend very strongly on ink companies producing LED compatible inks which to my knowledge there are not a lot of and what there is are mostly directed towards the digital market for inkjet printers.
UV LED has been shown to have stable outputs over long time periods, with up to 30,000 hours of life being claimed possible. One of its most exciting benefits is its lower electricity usage, which has been shown to be particularly good for flexo and sheetfed where larger systems tend to b used and as such use more power. Claims of up to 50 percent savings in terms of power for each unit have been made and so far appear to be standing up to scrutiny. They do not release any ozone, as they operate in the UV-A spectrum. The units are also smaller, and because they are solid-state devices they are generally easier to integrate and control. All this can lead to reduced environmental and health and safety concerns for many applications. This said they do seem to need relatively low run speeds although ink companies are saying that they have new ink chemistries coming out that will allow faster curing that is necessary if UV LED is to gain any growth in the existing UV market place. They are also quite expensive but as mercury becomes more of an issue there may be no option but to move in this direction.
We are considering switching to UV inks that will require UV lamps to cure them but are concerned about the heat that they might generate and how long the bulbs will last.
All UV lamps operate at high temperatures but all have systems that will keep the lamps cool and include air, water or both to pull the heat away from the lamp and press area which will stop the housing of the lamp becoming unacceptably hot. Air-cooled systems rely on air flow through the lamp housing to keep the housing from emitting excessive heat, with the exhaust air being drawn away from the press. Water-cooled systems rely on chilled water flow through the lamp housing to remove heat, with the heated water passed through a closed-loop chiller. Most systems have safety interlocks to prevent heat damage to the substrate should the web stop with the shutters open. Should this occur an electronic signal from the press will tell the lamp to go to standby power and the shutters to close. Most lamps are warranted for 1,000 hours of use, with most lasting 2000 hours of useful life or more. Total life expectancy will depend on power levels used to cure; using only low and medium power levels will extend the life of a lamp. Good maintenance programs that include regular cleaning of the bulbs and reflectors will dramatically help maintain their performance and hence life. If the reflectors are allowed to remain dirty, the power level needed to cure must be increased, which will shorten lamp life, excessive heat in the lamp housing may cause improper airflow and if the blower were not to function, or the air hoses are damaged or blocked will also shorten lamp life.
What images can we print using a variable data inkjet printer, and can we print on any substrate?
It should first be understood that all VDP (Variable Data Printers) are not all capable of producing the same images at the same speed. That said most systems are capable of producing sequential numbering, 1 and 2 D bar codes, random numbering, harvest marks, graphics. Speed and resolution of print can and does vary a lot from machine to machine. Again although most substrates can be printed on including absorbent and non- absorbent materials, not all VDP systems offer the variety of inks to be able to do this. Most systems only print in one color that being black but more advanced systems can print in other colors and other specialty inks.
We measure our ink frequently to check its viscosity and adjust as necessary so why do we still get tonal shifts with our colors?
It is true that viscosity has a direct impact on color strength but one parameter that many people do not think about is the temperature of the ink. Even if your facility is temperature controlled as ink is used and recirculated its temperature will begin to increase and in environments that are not temperature controlled this increase can be quite dramatic. Even though you might be measuring the same viscosity in an ink as its temperature increases this can and will have an impact on its shade and tone. This can be overcome with more modern viscosity systems that have the ability to chill the hosing the ink travels through and in such a way is able to maintain the ink at a constant temperature throughout the run and the entire shift. Your ink company will be able to advise you as to the ideal temperature to run your inks at and will vary dependent on the ink chemistry, speeds and substrate that you are printing on.
Want to know how to increase your productivity by 25% or more?
Sounds impossible, well it’s much easier than you may think, but you might not like to hear the reason why. This is because the fault lies with the failure of many print managers & owners to ensure that every job that is presented to the press is absolutely ready to run, and yet when challenged most owners and managers deny that this is the case. All too often when the root cause is fully and honestly evaluated as to why a press is not run more than 40 -50% of any given work day it is discovered that the job was not press ready and so most of the day is spent actually getting it ready to run. The problem seems to lie in the actual understanding of the term “Press Ready” which in my experience seems to have a different meaning to printers & owners alike. The irony of course is there can only be one meaning, which in my book means” Ready to run”. The sad fact however is that in most print shops there is so much denial, finger pointing and failure to hold people accountable for the failure to ensure that jobs are made ready to run that by the time people begin to realize how bad the situation is the company is often on the edge of collapse. To some degree it is not the actual understanding but the accountability or lack of by management and ownership in making sure that those responsible for getting a job to press do their part and at each step if the process is not correctly defined and signed off that there is a system of stopping the job at that stage to force the correct actions to be carried out. So where does making a job press ready start. It may surprise some to realize that it starts when the job is quoted and subsequently written up. If the job is incorrectly priced or an impossible time frame promised then things are only going to go downhill from there. Clearly if you’re pricing is too high you will not get the job in most cases, and if to low you will not be able to make a profit on it. Neither is desirable and this is just the start. Next the job most be correctly interpreted for number of colors, repeats, die’s that may be required, substrates, adhesives, inks, plates or other special tooling. Assuming that all of these elements are correctly identified then they must be ordered or drawn from existing inventory and if plates are not supplied they need to be made along with any relevant electronic files /color separations that have to be produced as well as approved before the plates can be made. Assuming all of these elements are taken care of then the job must be scheduled to go on the correct machine or machines that are necessary to produce the job while also ensuring that the operators with the necessary skills to produce the job are also available. All of these elements must be presented to the operator so that they can put them to press without the need to have to find the inks, stock, print cylinders/sleeves or have to mount their own jobs. All too often though I am told by many print managers and owners that they cannot afford a person or persons to stage a job ready for the operator to run and instead rely on the operator to do it themselves. Now in most wide web shops it has long been understood that someone other than the operator should present all of the key elements ink, stock, pre-mounted sleeves/rolls, tooling etc to the press but most narrow web & label printers regularly expect their press operators to get a job ready to run. Whether you are a wide, narrow or tag & label printer not adequately staging a job ready to run and scheduling in a logical manner will lead to nothing but inefficiency and massive down time. So how do you become 25% or more effective with your press uptime, ensure you are correctly quoting and scheduling your jobs, make sure you schedule them in a realistic manner ie hot, really hot is not a plan, and making sure your operators have the necessary skills and that your equipment is capable of running the job are all critical success factors.
We are about to switch from wiper rolls to a doctor bladed system, what are the pro's and cons between a bladed and two roll system?
There is no doubt that if you want to achieve cleaner more consistent print quality then a doctor bladed system is the way to go.
That said if you have been running for a long time with a rubber wiper roll and your operators have little or no experience with using doctor blades then
you need to understand there will be a learning curve as with all new practices and equipment.
You did not mention what type of doctor blade system you have adopted or what materials you will be using so I will briefly cover the basics of the available systems.
When doctor blades were introduced a positive angle (trailing blade) was used but today the reverse angle blade is used in most all flexo applications.
Unlike the trailing blade the reverse angle blade works against the rotation of the anilox roll as it meters the excess ink from the surface of the anilox.
Using a doctor blade will dramatically improve your control over the ink film thickness that you lay down and will allow you to run faster as unlike your
old rubber wiper roll the reverse angle blade will not be pushed away from the anilox surface as you try to run faster.
This means however that you must maintain your anilox cleanliness and be more certain that you have the correct line count and volume
engraving on your anilox as a blade will not allow you to open up the nip impression between as you will have got used to with your wiper roll system.
The blade angle and pressure are critical factors to maintaining a good clean wipe of your anilox surface.
Blades can be made from a multitude of materials ranging from blue /white carbon steel, stainless steel, plastics, laminates, composites so there is a lot of choice
although carbon steel is by far the most common.
Blade thicknesses and blade tip configurations also vary although the beveled tip blade is still the most common with thicknesses generally varying dependent
on the ink system being used, generally the more viscous the ink the thicker the blade.
Inks need to be filtered in particular when using blades as any metal or hard particles that get into the ink can become trapped between the blade and anilox resulting in scoring
of the anilox engraving.
Blades must not be run out of alignment or dry as scoring of the anilox will also occur.
If you have selected a chamber blade system then you will have two blade’s a metering blade and a retaining blade, so alignment, blade angle and pressure are even more critical.
Seals also become a factor with chambered systems in retaining the ink in the chamber, make the wrong choice and you will have a lot of ink all over your press.
That said the chamber system gives you the best control over your ink chemistry, its viscosity and will dramatically reduce your ink consumption as well as further improve the consistency of your print quality.
Rubber wiper rolls have a tendency to wear unevenly, swell, shrink, crack and allow for excessive wiping pressure and exaggerated alignment issues so you have made the right choice which ever blade system you have chosen but you will have a learning curve and should ask for as much support from your vendor as you think you will or might need.
Send in the fast form below to ask a Flexo Expert anything about Flexo.
Answers typically the same day or within 24 hours.