Who You Gonna Call?  Ghost Hunting in Flexographic Printing

Apex International Blog

by Doug Jones, Apex International

Ghosting, a faint image from another part of the design that appears where it shouldn’t, has always haunted the flexo industry.  Ghosting is most obvious in areas where large solids are used and always on printed side of substrate in the image area.  

ghosting-image

What causes ghosting?

Fortunately, the cause is far from supernatural.  While much has been written on the subject, most agree on these six issues as the most likely causes of ghosting.

  • Ink starvation
  • Ink fluidity is not appropriate
  • Chambered doctor blade not adapted
  • Mechanical issue
  • Anilox roll is not properly cleaned
  • Premature drying of ink on the anilox roll

What can I do?

Leave the Proton Pack at home!  The next time you have an issue with ghosting, try working through each of these possible solutions.

  • Increase ink level and/or pressure into the chambered doctor blade.
  • Use higher anilox roller volume
  • Add solvent (retarder) to increase ink fluidity, to flood the cells, and avoid ink drying into cells
  • Use a specific design of the chambered doctor blade to force ink to flood the cells
  • Select anilox roller where the circumference is a whole number multiple of the repeat length of the design times the number of plates round the cylinder or change the diameter of the plate cylinder
  • Increase the speed of the machine

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Are Your Doctor Blades Due for a Checkup?

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by Catherine Green, All Printing Resources

In flexography, print defects can stem from a multitude of moving parts, making troubleshooting feel like a constant game of chase. Much like the human body, with proper care and maintenance, all parts of this highly complex system can work together in harmony.

While the anilox roll is the heart of the printing press, the doctor blades are the workhorses that let the anilox do its job properly. Without even, consistent ink metering, the anilox is unable to deliver a uniform, measured ink film to the printing plate surface– its primary (and only) function. Ensuring your doctor blades are set properly in the press can make or break your printed result.

Doctor Blade Pressure

By inspecting the contact patch surface, information can be gathered to determine if the blade pressure across the chamber is set evenly. Uneven blade pressure can be due to misaligned chambers or incorrect installation of the doctor blade into the blade holder. Also, contaminants in the ink can leave behind score lines in the blade, or worse, the anilox roll. Looking for these clues and correcting the issue with proper ink filtration can prevent anilox refinishing and costly press downtime.

Installation of the doctor blade into the holder is easily one of the most commonly overlooked factors in the process. If the blade is installed incorrectly, it is nearly impossible to achieve proper ink metering. Doctor blades should always be installed into a clean holder, completely free of ink residue or other debris. When placing the new blade into the holder, ensure the blade is fully seated, then secure the blade from the center, working your way out to the ends. Following this simple procedure will ensure you’re starting a straight and true blade with each changeover.

This photo shows the precise measurement of a used doctor blade’s wear angle. (Click image to enlarge.)

This photo shows the precise measurement
of a used doctor blade’s wear angle.

If the press uses a chambered system, you’ll need to ensure the end seals fit properly and the blades are in the proper position in relation to the end seal. Check the fit of the seal in the chamber by looking for any gaps or excess compression around the seal. Also be sure that the anilox radius is an exact match to the anilox used on press. The fit should always be snug and accurate. To further prevent leaks, ensure the doctor blade overlaps the end seal halfway.

Once the blades are properly installed, the correct blade pressure is set, and the press is up and running, how can we know everything is performing as expected? This is where doctor blade analysis comes in. By carefully analyzing the used blades (both metering and containment, where applicable), APR’s Technical Solutions Group can pinpoint issues such as improper blade angles, poor blade mounting, or uneven chambers. This can be quite helpful when troubleshooting an existing problem, setting up a new press, or testing doctor blades.

To schedule a doctor blade trial or find out more about our analysis services, contact Catherine Green at c.green@teamflexo.com.

About the Author:

Catherine-Green_200Catherine Green – Catherine has over 12 years experience in graphic arts. An honors graduate of Clemson University’s Graphic Communications program, she has held positions in prepress, platemaking, and technical support. Before joining APR’s Technical Solutions Group, Catherine worked for Asahi Photoproducts as their Technical Specialist for North America. She brings expertise in digital platemaking, prepress, and process improvement to the TSG. She is an active member of the FTA, serving on both the Excellence in Flexography judging panel and FQC groups.

All Printing Resources, Inc. (APR) is a proven resource for solutions, trusted service, and support to the flexographic printing industry. APR delivers measurable performance enhancements and total cost reductions, including the after sale attention needed to see optimal results. APR represents some of the most innovative product lines worldwide and takes a “team” approach to deliver process improvement and innovative solutions

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How to Supercharge Your Water-Based Flexo Inks

Apex International Blog

by Jeanine Graat, Apex International

Global Environmental awareness is driving the printing industry to consider other ink systems in order to print more ecological packaging. Water-based inks are often praised as the green solution for a more sustainable product. They are a comparatively eco-friendly product, but when it comes to printing inks on to films and plastics, water creates problems

  1. Unless we print on high absorbency substrates, water inks require significant heat to dry and to leave a cured ink film on the substrate. In other words, they require energy that negates any positive ecological benefits from the use of water-based inks.
  2. Water has a high surface tension, which can print beautiful perfect dots however creates mottled/pinholed solids, which means that in order to ‘wet out’ on most plastic surfaces, the surface tension has to be reduced considerably in order to achieve good print quality and smooth laydown of ink.
    That is done by adding a surfactant or a solvent, which contaminates the water immediately. Depending on the substrate, the type of press, the printing speed, the amount of solvent can range between 2 – 20% of the press-ready ink.
  3. Waterbased ink is also susceptible to foaming creating micro bumbles which thickens the ink and creates a reduced ink transfer. In order to solve this, the ink can be adjusted with anti-foam agents which in turn create drying issues and trapping problems.
  4. Water has to be combined with solvents in order to dissolve the kinds of resins that provide good adhesion on packaging films. Read: more chemicals!
  5. Switching from a solvent based ink to a water based ink cannot be done overnight, because of the different transferring capabilities. It often means modification to the anilox rolls because a shallower, more open cell structure is required to print water based inks.
  6. Contamination between solvent inks and waterbased inks creates an adversus chemical reaction that can result in the ink setting solid and then a major cleaning of anilox, pumps, pipes is required. Therefore, a press is required to be dedicated to waterbased inks to ensure press efficiency is maintained and waterbased ink print is viable.

How to Supercharge Your Water-Based Flexo Inks

Having touched on the characteristics of water based inks here above, it cannot be left unmentioned, that critics have doubts on the printability of water based inks as well. They appear to result in:

  1. Poor scratch and rub resistance (especially shortly after printing)
  2. More difficult to re-wet
  3. More difficult to clean
  4. Comparatively lower gloss and poorer color strength
  5. Ink sets onto the plates creating ink build up and an inconsistent print
  6. Slow drying and therefore more heat/energy required
  7. Highest risk of clogging inside the anilox cells (especially with low-volume anilox rolls)
  8. Very difficult to control and guarantee a consistent and repeatable ink transfer (because of the pH and viscosity)

Water based inks – the future of printing!

Still, ink suppliers and also machine manufacturers dare to announce that water based inks are the future of printing. And a major part of the success of printing water based inks, lies in the actual transfer of the ink. Many of the above print issues can easily be solved when the right configurated anilox roll is used.

Apex International have performed several successful trials together with different ink brands in combination with leading machine manufacturers. The results reported by the ink manufacturers was:

  • The shallow surface structure of the open-slalom laser engraving technology developed by Apex, results in no clogging. The most effective ink transfer allowing for the maximum ink replenishment within the Anilox surface compared to the restricted limits of any conventional engraving is realized. A very thin layer of ink can be transferred and less drying time is needed (energy savings!).

ShallowCells_GTT

  • Major advantages with no air inside the print process. In a closed-cell structure (image left), air gets trapped inside the cells and especially with waterbased inks, that is a disastrous combination. With the open-slalom structure (image right), the ink flows freely and the air will not get stuck inside the cell, it simply flows away. Less air simply means a better lay down of ink and better results on gloss and color strength. A side effect of having no air inside the print process, is the fact that a defoamer is no longer needed, which makes water-based printing an even more ‘green’ way of printing packages.

How to Supercharge Your Water-Based Flexo Ink  How to Supercharge Your Water-Based Flexo Ink

  • With an open structure, the phenomen Dot Dipping does not occur. The explanation is simple: pressure causes counter-pressure, ink escapes through the opening and the result is over-inking. The water-based ink does not set onto the plates and will not cause ink build up and therefore inconsistent print is no longer an issue. The below image shows this:

How to Supercharge Your Water-Based Flexo Inks

  • The key to the success of waterbased inks is to control the viscosity and the pH and the key benefit of the open-slalom surface structure is a consistent ink transfer and the ability to print repeatable results with no air inside.

Conclusion: the last 5 print issues (out of the 8 mentioned) caused by waterbased inks, can be improved by using Apex GTT Anilox technology, which is a very good step in the right direction of a greener Flexo future.

Samples of waterbased prints performed by different ink brands on 3 different machine types will be available in the ‘Green – Waterbased Area’ at the Apex stand (11B26). Receiving your samples by visiting theDrupa stand, or by requesting your sample pack here.

See physical proof of state-of-the art ink-transfer technologies that obviously supercharge your water based inks!

Reserve your FREE Sample Pack!

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Troubleshooting Part 2: Coating/Laminating

Troubleshooting: Coating & LaminatingBy Tom Kerchiss, RK Print Coat Instruments Ltd

Co-operation and shared goal setting has become increasingly prevalent in label and package printing and converting as all supply chain providers and operatives strive to meet benchmark standards while endeavoring to make a profit. Regardless of whether the process step that you are engaged in is printing at the start of a run or it’s a converting process at the end of a run it is in every one’s interest that process variables and what causes them are understood and that inconsistencies are bought under control in the shortest possible time, with minimum inconvenience and with as little waste generated as possible.

It goes without saying that process quality is only as strong as its weakest link. For example, if print is of the highest quality this will count for nothing if a subsequent coating process, slitting or rewinding goes awry. Apart from product throwaway the printer will have wasted time, energy and material turning out a product with value only to see it scrapped.

When it comes to print processes such as flexography there are devices now such as the FlexiProof for identifying, resolving and controlling ink variables; for colour matching and determining printability: gloss, durability, rub resistance, etc. Other devices, such as the hand held portable trouble shooting device, the EsiProof were covered earlier in an editorial entitled Part 1 of Troubleshooting.

Coating and laminating are process areas that are theoretically straight forward but are becoming more complex as time goes on. Coating and laminating has its own set of challenges, some of which the coating technologist seemingly has little control over.

Coating

The substrate onto which the coating is applied is often responsible for a range of defects inclduing: poor adhesion, poor planarity and lay-flat. Substrate associated issues of note include winding irregularities as well as the defects that arise as a result of airborne and other forms of contamination. These defects can occur during substrate manufacture, product shipment and storage and during on machine processing including, when the product is being fed through the machine or on being unwound and rewound. In many instances the problem is exacebated by the presence and generation of electrostatic forces. Even the operator may introduce contaminants such as skin, hair and fibre from apparel.

An inability to coat a substrate uniformily or to wet the substrate effectively warrants mention. In order to deposit a fast flowing fluid coating onto a given substrate with no voids or inconsistencies its necessary that the surface tension of the coating solution and the substrate surface interface optimally.

To achieve the best of surface conditions it may be necessary for the surface to undergo modification via flame/electrical discharge or plasma treatment. Another approach is one taken by the manufacturing chemist whereby surface tension characteristics are measured and the formulae is manipulated within specific parameters.

As with many of the problems that arise during processing, regardless of whether its flexo printing, slitting, coating or laminating there is rarely a clear cut solution, its often a case of eliminating possible causes one by one. Coating uniformity or lack of it can sometimes be due to substrate manufacturing variability or an innapropriate choice of coating applicator. For instance, variation in the thickness in a non-transverse direction can, particularly if knife coating is the selected applicator method affect coat uniformity. The reason that knife coating technology is susceptible to substrate variation is that the blade is set at a fixed height and therefore substrate/coat contact interface is critical.

Staying with knife coating for the moment its worth noting that the way in which an air knife coating is applied can produce some unexpected results. When a coating is deposited on a web at high speed the flow of fluid is subject to an alternating flow regime. All laminar flows on a moving web have a parabolic velocity profile with the fluid at the surface of the web moving at the speed of the web. The fluid at the air interface however, behaves differently and is just a bit slower than the speed of the actual web. In effect the volume flow up exceeds the volume flow down.

With regard to air knife coating the thicker flow builds up just below the air impingement zone or meniscus. Once the air knife allows the thinner coating flow to pass, any excess liquid collects below the meniscus and will not flow on until the lower layer builds up and becomes thick enough to balance the upward shear force that derives from the web. This ebbing and flowing produces tiny fluctuations in the flow of coating just above the air knife which can result in the coating looking flawed. Sometimes the coating fluid smooths down and has a desirable varnish or enamel looking finish. Sometimes it does not smooth down and the coating shows signs of chatter or streaking. If this occurs the coating operative has little choice but to experiment, find an appropriate suficant, one that will promote post coat smoothing without jeapordising wetting or adhesion properties.

Laminating

Laminating throws up its own share of problems. Sometimes when a two ply dry bonded laminate comes off the machine it has a hazy appearance. This often perplexes everyone, especially when the job has been run previously without any problems using the same substrate and adhesive. In reality the clue to what’s causing the problem is in the hazy appearance. If too little adhesive is applied to the primary substrate high and low spots willl allow air bubbles to develop and with it the hazy appearance. If the adhesive coat weight is increased the haziness should disappear.

As with most processing functions attention to detail pays off. For example coatings and primers must be dried properly. Lets consider an out of line heat seal coating application as an example.

This heat seal coating is applied to foil for the purpose of providing adhesion to polyester. The heat seal coating is deposited on one side of the foil. This coated foil travels through an oven and the dried coated foil is wound up in rolls. The rolls are then stored until they are needed. The roll is unwound and combined with the polyester by passing the two substrates through a heated nip to effect the bond. The material is then rewound with the foil/heat seal coating/polyester ready for shipment to the customer.

Any coating or primer must be dried completely. If not the material could become tacky and when wound up in on itself the material will adhere to the backside making subsequent unwinding impossible

Good housekeeping is a must. The flow rate to roll coating pans should be monitored and adjusted; solution and applicator temperatures must also be watched and the gap between applicator and coating roll measured with substrate in place. Consideration must be given to the correct coating applicator. A slot die applicator may well give good results when used with a closed surface substrate such as polyethylene as the fluid will not penetrate and will be uniform. However the same applicator if used on a substrate with an open porous surface would produce a less uniform result as some of the fluid will penetrate into the pores. In this instance a knife coater would be the best option because as the blade is fixed at a set height from the web there will be uniformity of coating fluid and the pores or cells of the substrate will be filled.

Coating viability depends to a large extent on selecting the most appropriate coating method for a product to be processed – not always easy. The coating operative must take into account product function, desired coating weight, quality level needed, raw materials required, and of course the material onto which the coating is to be applied needs to be considered. There is a wide range of pre and post metered coating technologies that can be used. But which one will give the best reproducible quality? Sometimes its trial and error to determine which technology to use and this is especially true when it comes to developing new products.

The Rotary Koater

The Rotary Koater, a pilot printing, coating and laminating system designed and developed by RK Print Coat Instruments is an ideal system for those faced with daily coating/laminating challenges. As a research and development tool it enables the manufacturer, the printer, the converter and others, to undertake R & D on an economical scale and under precisely controlled conditions. It can be used to test different formulations, substrates and processes. It is also highly effective as production machine for the small-scale production of specialized materials.

On the other hand there are those organizations that for one reason or another need specialized machines; a standard machine simply won’t suffice. The VCM or Versatile Converting Machine meets the needs of this niche market.

Each VCM is purpose built and unique to each customer. A precision system, each is built under conditions of close commercial security. Customers are able to select from best available technology including 15 different printing/coating technologies.

rkprint

RK Print Coat Instruments Ltd
Litlington, Royston, Hertfordshire SG8 0QZ
www.rkprint.com sales@rkprint.com

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Troubleshooting: Colour Consistency

Troubleshooting: Colour Consistency

By Tom Kerchiss, RK Print Coat Instruments Ltd

Because colour has such a powerful influence and plays an important role in building a winning brand – everyone from brand owner to marketer to the printer and converter are seeking colour harmonization across all packaging shapes and formats, regardless of whether the substrate is flexible film or carton.

Achieving Colour Consistency

Achieving consistency in colour on press is sometimes easier said than done.  Colour in itself can be a slippery customer, colour may agree with set numerical values but when its visually being reviewed and approved for a particular job its not unknown for the customer to voice colour accuracy concerns, the reason being that the way we each interpret colour differs. 

But that’s not all, problems that arise when colour is being evaluated can include geometric metamerism, a phenomenon exhibited by colours that appear to be a match at one angle of illumination and viewing but when the angle of illumination is changed they no longer match. Geometric metamerism can normally be traced to issues surrounding gloss and/or substrate surface texture.

Certain colours when used on specific substrates can produce results that can be unexpected. For example, in situations such as flexo printing on transparent films for bread wrapping, the scattering characteristics of an opaque white ink layer greatly affects the appearance and colour of the finished product.

Printing and package converting can sometimes seem to be a constant struggle to combat process variables. Colour inconsistency is a major cause of production bottlenecks, delays, waste (energy, materials, labour & time) and missed deadlines.  Colour variations are of course far from being the only variable that the flexographic package printer has to contend with there are many others that can occur some of which the root cause of the problem may at first be difficult to pin point. Sometimes it’s more about eliminating what the problem isn’t. In other words methodically working against a checklist eliminating the obvious until what remains is the solution. Think carefully before panicking has something changed? Defects such as dirty prints, where clumps of ink larger than the half tone image are transferred to the moving web may be caused by increased press speeds and using inks that are not optimized for that purpose and/or the necessary changes have not been made to the dryer, e.g., slower drying speeds.

UV curable inks can present several challenges such as spitting and dive-in. The latter can generally be resolved by adjusting the speed of the press in relation to the curing lamp wattage. Spitting can be controlled by lowering the viscosity of the ink, though that is not always possible and by adjustment/replacement of a suitably optimized doctor blade. 

Colour may sometimes appear more intense than it should be. In this instance it’s often down to one of two causes: too much ink is being carried by the metering roll/doctor blade; alternatively the problem is related to the colour of the ink being too concentrated during mixing. Adding an extender in controlled amounts will enable an ink kitchen operative to resolve this problem. If the problem has been identified as one of too much ink, the volume can be reduced by adjustment of the metering system or by adding thinners.

While colour may appear too intense when a proof is made the reverse can occur as well: colour can look washed out or paler than expected. If this occurs it can be due to the ink being too thin, insufficient ink is being picked up which may be due to a clogged up anilox. The flexo printer to resolve this problem can increase the viscosity of the ink with fresh and un-thinned ink; clean the anilox or increase press speed or a combination thereof Good housekeeping, which includes cleanliness and routine maintenance checks are important.  It is also worthwhile having troubleshooting and other devices that help to identify and resolve potential problems in place. This is especially important when the printer is working against the clock and the customer is awaiting delivery of an order. One such troubleshooting device is the hand-held ‘take anywhere’ EsiProof colour-matching tool from RK Print Coat Instruments, which can be taken from machine to machine.  This device helps to reduce downtime and on-press waste and offers a return on initial capital outlay of a few weeks.

The Esiproof is a compact precision unit into which an anilox roller, EPDM stereo roller and doctor blade are fitted to enable the user to obtain realistic, high quality flexographic proofs, up to one metre in length. The use of a doctor blade enables the proofing of all flexo inks including high viscosity UV curable inks. The unit enables colour proofing for both customer approval and spectrophotometer readings.

The Esiproof has been modified to make the already competitively priced device, even cheaper, but without compromising on performance. For instance the micrometers used for adjustment have been replaced with springs. Highly adaptable, the Esiproof can be supplied with ceramic laser engraved rollers from 140 to 800 cells per linear inch or with mechanically engraved steel (QCH type screen) and chrome plated anilox rolls. Both ceramic and steel anilox rollers are interchangeable.

The Esiproof is an ideal tool for pressroom managers enabling them for example to quickly produce proofs from multiple machines on the fly. It facilitates the proofing of fine tones, and higher viscosity inks such as UV curing inks.

Another device, one that can be used by producers and users of flexographic inks as well as by substrate and other manufacturers and suppliers is the  FlexiProof. This device saves time spent adjusting inks on press and contributes to consistent product quality. In addition to colour matching, determining printability and resolving issues surrounding ink and substrate: the FlexiProof, which is a scaled down but component critical exact version of a flexographic press can be used for pilot runs and the trialing of unfamiliar materials.

It is ideal for standard test procedures such as evaluating gloss, scuff, chemical resistance and durability.  This compact device is available in a number of variants, including the FlexiProof UV for the inline curing and proofing of UV inks and the FlexiProof LED UV for heat sensitive substrates.

rkprint

RK Print Coat Instruments Ltd
Litlington, Royston, Hertfordshire SG8 0QZ 
www.rkprint.com sales@rkprint.com

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Top Causes of Anilox Scoring and How to Prevent Them

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by Doug Jones

A score line in an anilox roll is a groove that has run directly through the engraved surface.  The score shows a visible line in the printed or coated product and is irreversible. Once the surface is scored, the roll must be reconditioned or replaced. For these reasons, it is crucial to learn how to prevent scoring whenever possible. Below you will find an explanation on score lines, the different types and how to prevent them from occurring and keeping your print quality as high and consistent as possible.

3 types of score lines:

  • Cosmetic or Preliminary
  • Lightly Polished
  • Severe or deeply gouged

Anliox Scoring - Score lines

Anliox Scoring - Samples of score lines on different substrates

Samples of score lines on different substrates

What Causes Score Lines?

Over Impression

Over impression can cause premature wear to the doctor blade and roll. Long Blade tip slivers can easily cause score lines: these are formed when the blade bends back causing wear on the side rather than the tip.  As the side of the blade wears through, the tip breaks away in the form of a long metal sliver.  Normal shavings from blade wear from “kiss impression” will not damage a roll.

Doctor Blade Tip Material & Settings

Are you using the same blade for whites or metallic inks as you do for conventional ink? Using incorrect blade tip and material for type of ink can have disastrous results and hardened blades significantly increase the chance of scoring.  The same can be said of replacing the blade on every anilox change.  A blade “seats” to a specific LPI and is not meant to be used again.  Blade forms to anilox and becomes a “Micro” saw.  Finally, try resetting the doctor blade chamber after installing new blades.  A worn blade is shorter than a new blade and if chamber does not reset, there will be excessive pressure.

Try a nickel coated anti-scoring blade. Nickel is softer than steel and ceramic, many converters use this very successfully as it is more forgiving and can cover potential misgivings in the metering process. It will also last longer because of coating; cleaner doctoring because blade is stronger; resist corrosion better because the blade has a barrier coating.  And remember, always use higher quality blades. A low quality low cost blade can break down fast.

Anliox Scoring - Score Line Check List

Helpful Hints

  1. Coated blades are more forgiving than uncoated blades.
  2. The doctor blades should never extend past the ends of the seals, but should be flush and even with the bevels on the end seal.
  3. A coated blade will offer more “forgiveness” than an uncoated doctor blade and compensate for error
  4. Chattering blades vibrate and this action can act like a jack hammer to the ceramic and break cell walls
  5. If too soft, improper end seals will cause leakage and operator might adjust setting to compensate putting more pressure on anilox and stress on the blades. Do not set chamber to stop leaking.
  6. Correct placement of end seals allowing even contact with anilox and consistent transfer of the ink film to plat
  7. Shims break off or can become exposed to the anilox surface and cause scoring
  8. Ink resins can glue pigments, blade metal and other debris to the blade

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Imaging the Possibilities

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by Catherine Green, All Printing Resources

Exploring Today’s Plate Imaging Options
A common fear among those still using film imagesetters to produce photopolymer plates is that their device is on its last days–barely hanging on to operational status. Replacement parts are few and far between, leaving little choice but to scour the Internet for parts and redundant equipment to keep the imagesetter operational. In a recent survey, some imagesetter users reported expenses of up to $9,000 annually for parts and services. It also represents taking the risk that the imagesetter can be repaired in a timely fashion (or at all) to avoid costly downtime. The purpose of this article is to present options available to satisfy nearly every budget and quality requirement.

Choosing an imaging system that fits your needs is critical to a successful return on investment. Not only should the current requirements be considered, but perhaps more importantly future needs and objectives.

  • What are the objectives of your company in the next five years?
  • What level of quality will your customers demand, and what will your competitors have to offer?
  • How many finished plates per hour or shift need to be completed?
  • What are your typical and maximum finished plate sizes?

Before selecting an imaging device, knowing the answers to these questions will ensure that this important asset will fit your needs for many years to come.

Eliminating Film: A Streamlined Platemaking Workflow
For those seeking a way to eliminate film from the platemaking process, there are several options. Direct engraving, laser ablation, and inkjet CtP are all filmless plate imaging options. While all three methods yield an imaged flexo plate, there are considerations for each method that can make or break these technologies as a fit for your business.

Laser Ablation
By far the most popular digital platemaking option, laser ablation devices use a YAG fiber or diode laser to ablate image areas on digital flexo plates (plates with a black carbon LAMS layer). Ablation refers to the process of the laser beam(s) vaporizing the black carbon layer, exposing the plate material beneath. This allows the ablated areas of the plate to be exposed to UVA light and cure, forming the printing image. Specially engineered ablative films can also be imaged by this type of device to produce positives or negatives for applications requiring film. Laser ablation devices are the current industry standard for digital platemaking for a number of reasons including high quality output, wide selection of compatible plate materials, and overall efficiency.

Laser Ablation Pros:

  • Efficient throughput of plates.
  • High resolution imaging capabilities and specialty screening options.
  • Small overall footprint with minimal auxiliary equipment.
  • Excellent reliability and ease of use.
  • Seamless imaging capability (with Esko CDI Cantilever and ITR plate sleeves).

Laser Ablation Cons:

  • Initial cost of equipment can be a large expense.

The largest and leading supplier of laser ablation devices is Esko. Esko is a global supplier of integrated solutions for the packaging and labels, sign and display, commercial printing and publishing industries. Esko has been developing software and hardware innovations for packaging and printing for decades. The company invented digital flexo in 1995 and has been leading the development ever since. Esko’s flexographic solutions are used in about 90% of high quality flexo production. Today, Esko is synonymous with excellent quality and consistency in all flexo printing applications.

Another global supplier of laser ablation plate imaging devices is Xeikon. Formerly known as FlexoLaser, Xeikon’s ThermoFlexX devices also utilize a YAG laser for ablating plates. In December 2015, Flint Group acquired Xeikon to expand their reach into the digital printing market, forming a new division called Flint Group Digital Printing Solutions.

Inkjet Computer-to-Plate
As a newer technology in the plate imaging market, Inkjet CtP eliminates film from the platemaking process by utilizing inkjet technology to print a mask layer onto analog sheet photopolymer. The process is simple, fast, and the equipment is the least expensive of the digital plate imaging options. While overall image quality is not on par with laser ablation, this option would be suitable for narrow web printers who can work with the small plate size requirement and are not planning to implement high resolution/high LPI printing techniques.
DigiFlex is the exclusive manufacturer of the FlexoJet 1725 Inkjet CtP device for flexographic plates. Their unique bi-component ink and laminated primer system make this device compatible with nearly any analog plate on the market. Uniquely, the Aquaflex Optima plate does not require the laminated primer to be applied, resulting in a streamlined workflow and consumable savings.

Inkjet CtP Pros:

  • Small device footprint.
  • Quiet operation, even suitable for office environments.
  • Can utilize same analog material through transition to digital imaging.
  • Flat top dot is produced when primer is applied.

Inkjet CtP Cons:

  • Imaging resolution is lower than laser ablation.
  • Periodic manual cleaning is required.
  • Ink and laminate consumables required for operation.
  • Printed mask must be removed with water before solvent processing.
  • Limitation on the size of the plate that can be produced.

Figure A – Comparing Laser Ablation to Inkjet CtP Plate Imaging

apr-figa

Direct Engraving

Direct engraving machines image plate materials using a high-powered engraving laser. The laser destroys the non-image areas of the plate to create relief. These machines eliminate film as well as traditional plate processing equipment, and can provide nearly unlimited dot profiles (shoulder angles and tip shapes). While these machines can provide some unique capabilities, they can be quite expensive. Here are some key factors to take into consideration:

Direct Engraving Pros:

  • Two step platemaking process (engraving, cleaning).
  • Nearly unlimited control of dot shape and shoulder profiles.
  • Seamless imaging capability.

Direct Engraving Cons:

  • A limited number of materials can be engraved using this process.
  • The engraving laser can only produce one sheet/sleeve at a time, so throughput is considerably less than other platemaking processes.
  • These machines are typically large and can require filter and suction equipment to be installed in a separate, specially-designed room.

Direct engraving devices are available from SPGprints, Hell Gravure, Luscher, and Kodak.

Negatives Without the Negativity

If the analog platemaking process better suits your company’s needs, or if you are using liquid photopolymer, continuing with film may be the best option for you. Thermal film imagesetters provide durable, high quality film negatives (or positives) with the convenience of a thermal desktop printer. These devices utilize a precise thermal imaging head paired with a special thermally-sensitive film to create finished film in one step. No chemical processing, no additional equipment, no hassle. All Printing Resources carries the EXILE line of thermal imagesetters, which offers a variety of sizes for nearly any application.

Thermal Imagesetter Pros:

  • Excellent density, crisp edges – suitable for many applications.
  • Durable film can be stored for 20+ years without degrading.
  • Fast, chemical free film output. No processing or darkroom required.
  • 1200 x 1200 dpi resolution is suitable for fine line work and screen rulings up to 120 LPI.
  • Small device footprint, no extra equipment.

Thermal Imagesetter Cons:

  • Not suitable for screen rulings over 120 LPI.
  • Thermal print head is a consumable, but replacement can be covered with film purchase agreement.

Inkjet film printers are also available, but image quality is compromised as compared to thermal film or traditional imagesetter film The images in Figure B show the difference in edge definition and image formation between these two technologies.

Figure B – Comparing Thermal and Inkjet Film Imaging Quality

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EXILE Technologies (formerly OYO Instruments) is a leading manufacturer of professional-quality thermal imaging equipment, film products, and direct-to-screen devices. EXILE Technologies is proud to manufacture all equipment in the United States.

If you are new to digital platemaking, or simply looking to upgrade your current equipment, All Printing Resources can help. We offer the equipment options, on-site training, and flexographic printing know-how to ensure your plate making process is completely optimized and performing to it’s full potential.

Quick Reference Chart – Plate Imaging Options
apr-table

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Plugged Cells?

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Cell plugging is a common issue associated with anilox rolls. It is a costly problem that can be controlled or eliminated from your process through the use of recent technological advancements and a preventative maintenance program. Instead of listing the many problems that cell plugging creates, I’ll get right to the real focus of this article: how to maintain consistent anilox volume control. We all know that there are an enormous amount of variables in the Flexo process. In order to stabilize those variables and maximize your investments, it is up to you to control the issues that are within your power. This article is intended to give you the tools to do just that.

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The Anilox Roll

The anilox roll is the mechanical heartbeat of every Flexo process. With each beat of that anilox heart, there is either a sellable or a non-sellable product being created. Managing the variables of the anilox process is where the preventative maintenance program really comes into play. Controlling, tracking and performing scheduled preventative maintenance are the keys to ensuring the making of a consistently sellable product.

Press operators and their support team are the human heartbeat of preventative maintenance. Their cooperation and proper training will maximize your anilox investments and facilitate the production of consistently sellable product off the press. The process is as follows: the volume of each anilox correlates directly to the ink film thickness consistently being transferred to the plate; the ink that is being metered by the anilox must be maintained at optimum and recommended pH/viscosity levels to ensure precise and uniform ink release, as well as a decrease in plugging issues. Common practice by press operators is to add base to ink on press to compensate for inadequate printed ink density and this is costly. A individual anilox rolls unanticipated volume loss, creates the need to make ink adjustments or change anilox rolls. Due to the intricacy and importance of the anilox roll, operators need to; care for them, get to know them, and subsequently trust each roll in their mix to maintain the highest levels of productivity.

Technologically speaking, recent advancements have given rise to improved cell geometry and greater consistency of engravings. Pamarco’s EFlo engraving is a prime example of an advancement in anilox cell geometry. This new technology  provides the ability to improve both productivity and metering consistency.

EFlo engraving

The EFlo engraving is an extended cell that allows for 15% more ink release, while having the shallowest, flattest-bottomed cells. The shallow shape of the cells means longer running press times without the need for stopping to clean up. Longer press times means increased productivity. Cell-plugging issues are also reduced through the use of the shallow cell geometry, making it easier to thoroughly clean and maintain consistent ink films. These translate to an increased line screen of your anilox roll when converting from conventional → EFlo, due to the improved control of ink release.

Cell Plugging & Effective Anilox Care

Information compiled by Pamarco through anilox evaluations points to many converters struggling with both cell plugging and effective anilox care. Cell volume is one of the keys to understanding these problems. The cell volume is measured in Billion Cubic Microns or “BCM.” This is the volumetric capacity of ink or coating that an individual engraved anilox cell can carry. Maintaining uniform volumetric capacity throughout all of the engraved cells on an anilox roll is critical in effectively producing consistent, quality products. It only takes a 10 to 15% reduction in cell volume because of plugging to create consistency issues on press. Pamarco’s Cell Restore has been proven to be a solution to this difficulty throughout the industry, and was formulated specifically for breaking down cross-linked, water-based resins.

Cell plugging is caused by a build-up of dry ink or coating in the cell bottoms. Cell Restore was engineered with a focus on breaking down and swelling the dry ink, and that’s exactly what it does. It is a neutral pH, spray-on solution that fractures cross-linked resins on a micro emulsion layer, without jeopardizing the life span of the ceramic coating. It is also very user friendly. After applying the Cell Restore and letting it work for 5 minutes, a micro-fiber pad is used to remove the swelled and suspended resins from the cells. It is recommended to incorporate this cleaning solution into your regular Preventive Maintenance schedule to prolong the time period between major cleanings (I.E. Soda Blasting Units from Eaglewood Technologies Sanilox System).

In conclusion, incorporating a comprehensive program focused on maintaining the integrity of your anilox roll inventory will add value to your investment.  Your process will see a reduction in hidden costs, improved quality and greater consistency. The print nip for each unit of a Flexographic press should be looked at as a body, surrounding its mechanical heart (the anilox roll). It works to the favor of both the printers and the converters to collaborate with and draw upon the expertise of their vendors. When properly utilized, the relationship that you have with your anilox roll vendor can greatly benefit your business.

About Pamarco:

Committed to the market since 1946. From offering the most extensive portfolio of products on the market, to offering the best consultative advice, to delivering an overall superior customer service; all underpinned by their passionate corporate culture, Pamarco has been able to build enduring and meaningful relationships with converters and OEM suppliers all around the world. To find out what Pamarco can do for you, visit www.pamarco.com.

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Filed under Anilox Rolls, Printing

3 Tips to Prevent UV Ink Spitting

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by Doug Jones, Apex International

UV inks are considered by many to be the most popular in the narrow-web space.  And for good reason.  Print results with UV inks are consistently better than those using water or solvent-based inks.  But the use of UV inks is not without its challenges.  Chief among those challenges is the issue of spitting.

There are several theories as to why spitting occurs with UV inks and not with water or solvent inks.  Generally, these revolve around the higher viscosity of UV inks comparied to water or solvent and the impact it has on the doctor blade.  Specifically, the higher viscosity can move the blade just enough to allow more ink than is intended to slip through.  Other theories suggest that anilox cell type, viscosity, press speed and doctor blade specifications all play a role.  Regardless, the results can be a disaster, particularly at high speeds.

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While exactly why spitting occurs is a subject for debate, what is not in dispute is that the relationship between doctor blade and anilox is at the core.  If spitting is creating a challenge in your shop, try these tips for better print results:

1. A stiffer doctor blade may prevent excess ink from getting under and transfering to the plate and substrate.

Testing shows a thicker blade will minimize UV spitting because they resists hydroplaning and do not allow texcess ink to transfer to the anilox.

2. Try a 30° anilox cell with openings

The ink can move through the openings in the anilox cell walls preventing ink from being built up onto the back of the doctor blade.  (Situation 1a).

Ink_Spitting_2

A word of caution: This solution is only temporary. Because the roll will wear over time, the openings will become smaller and eventually disappear. So over time you will get the same situation as with the regular anilox roll. Ink will built up at the back of the doctor blade (situation 1b).

3. Try GTT Channel engravings.  

There is no pressure built up at the doctor blade because the ink can move through the GTT channels. Therefore no ink builds up onto the back of the doctor blade and no ink drops from the doctor blade onto the flexographic plate or substrate.

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Get the flexo solutions guide now!

 

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Color Evaluation Pitfalls in Flexo Applications

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by Tim Mouw, Applications Engineering & Technical Support Manager, X-Rite Pantone

Lighting plays a huge role in how you perceive color, making a light booth a crucial part of any flexographic visual evaluation program. It can help you verify whether the color of your product is acceptable, plus ensure colors will remain accurate in every lighting condition at point of sale and after purchase.

Visual evaluation is especially important for packaging applications, which require consistent color across different substrates, inks and printing processes. You can spend hours getting brand colors right, but if packaging doesn’t match on the store shelf, the product will be seen as inadequate.

Always view your prints under lighting conditions that conform to ISO standards. In addition to D50 (daylight), you may need to view production samples under other lights that simulate store or household lighting to assure that different parts of the package, such as the label and the box, will continue to match on display shelves or in the consumer’s home.

X-Rite’s Spectralight QC

 X-Rite’s Spectralight QC is a holistic visual color assessment system with state-of-the-art light sources capable of meeting practically any brand owner specification.

However, just using a light booth isn’t enough. Today we’ll share a few common pitfalls our customers encounter when visually evaluating color.

  1. Light booths are painted Munsell gray, a neutral shade that does not distract your eyes from the colors you are evaluating. It’s important to keep everything else around you neutral, too. Wearing brightly colored clothes or storing objects in your light booth will distract your vision.
  1. Make sure your light booth is the only source of light in the room. If you set it up it in the print shop under bright fluorescent lighting, or place it near a window with sunlight pouring through, these light sources will interact with the standard source you have selected in your booth and skew your results.

X-Rite’sLight Booth

  1. Do you wear glasses or contacts? Make sure the lenses aren’t tinted, because even a little color can make a difference when you’re judging slight variations in color.
  1. When looking for color difference between two samples, they should be touching. Leaving even a little blank space between them can trick your eye into missing a slight shift in color.

Judge QC

With five light sources, X-Rite’s Judge QC will help you evaluate standard to samples and batch-to-batch color variation.

  1. Staring at a color for longer than a few seconds doesn’t improve your decision-making ability. In fact, our delicate eyes require frequent rest during critical color evaluation. Once they start to get tired, they’ll send incorrect information to your brain, so only look at a sample for a few seconds, then close your eyes and let them rest before looking again.

Want to learn more? Check out The Science Behind Visual Evaluation on X-Rite’s blog for a more technical explanation for making your visual evaluation program the best it can be.

Mouw_TimAbout the Author:

Tim Mouw is the manager of the Applications Engineering and Technical Support Team for X-Rite in the Americas. In his role, Tim oversees a team of 20 technical support specialists that help customers improve color quality control processes. Over the past two decades, Tim has tough over 300 courses on color science across North & South America, Europe, Asia, and Australia.

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Filed under Color Management, Printing