Pinning Technology for Clean Transfer

Pinning Technology for Clean Transfer is a unique plate technology engineered by Asahi Photoproducts to transfer all remaining ink to the print substrate due to the photopolymer plates having a lower surface energy than other plates on the market. Not only does this deliver stunning graphical quality, but it also improves overall production efficiencies due to reduced makeready waste and fewer press wash-ups.

pinning_technology_infographic

Asahi AWP™ water-washable plates use Pinning Technology for Clean Transfer. This enables them to produce superior results compared to both traditional and digital flexographic printing plates. They also are a more environmentally sustainable solution. It should be noted that up to 15 litres of solvent per plate are used in the solvent-based platemaking process. The entire AWPTM plate manufacturing process creates little waste, just unexposed polymer residues and wash out solution, which are collected and safely incinerated.

In a recent controlled test comparing water-washable plates to standard solvent-based plates, results indicated operations could achieve in an immediate ROI when switching to these plates.

  • For the conventional plate, the run length was 37,368 linear metres. It took a total running time of 173 minutes. Total press down time was 47 minutes for plate cleaning and make-ready. Waste produced was 1,025 metres. OEE efficiency was calculated to be 72%.
  • For the Pinning Technology plates, the run length was 38,000 linear metres. It took a total running time of 140 minutes. Total press down time was 8 minutes for plate cleaning and make-ready. Waste produced was 450 metres OEE efficiency was calculated to be 91%.

pinning

Pinning Technology plates produced 575 linear meters less waste material. They resulted in a 26% improvement in overall equipment effectiveness (OEE) with fewer press stops for plate cleaning and more consistent overall quality. For a 24-hour operation, this translates to the ability to process at least two additional jobs per day at a higher quality level with more contrast and less environmental impact.

OEE AWP

The cost benefit of the AWP plate may vary depending on the customer’s production profile but is typically between 25% – 35% vs. conventional plate technologies.

Due to their exceptionally precise registration, plates with Pinning Technology for Clean Transfer also make it easier to implement Fixed Colour Palette printing to virtually eliminate the need for spot colour inks, reducing ink inventories and minimising or eliminating the need for press wash-ups between jobs.

Using fixed colour palette printing, the breakeven between flexo and digital printing continues to fall to as short a run length as 350 metres. This means that flexo is competitive with digital for all but the shortest runs, and there are many benefits packaging converters can gain by moving to this model, including very short job changeover times with minimal or no wash-up and limited waste due to the fact that inks do not have to be changed. Plus, more than 90% of Pantone colours can be accurately rendered using fixed colour palette printing.

Pinning Technology for Clean Transfer is an innovation in flexographic plate technology and a win/win for forward-thinking flexo printers.

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Addressing Metering Challenges of White Inks

by Daetwyler

White-Inks-Infographic

WHY ARE WHITE INKS DIFFICULT TO WORK WITH?

All professional printers eventually come up against the metering challenges of white inks. Throughout the industry, white inks are notorious for being inconsistent and requiring frequent changing of doctor blades often. The longer a doctor blade lasts, the more expensive it is in many cases. Weighing the cost of a doctor blade vs. the cost of press downtime is as issue printers and coaters deal with constantly. The issue with metering white inks is actually a little more complicated than just buying the right blade.

GATHER PROFESSIONAL SUPPORT:

First and foremost, ink, anilox, and doctor blade suppliers should all be consulted in a cooperative manner. When everyone knows the details of the scenario, a more comprehensive solution can be attained. Having end seal suppliers involved can also prove useful. Most people working in these industries are either printers themselves or have at least been involved in the print industry for some time – so they will most likely be able to relate to your specific challenges.

COMMON SENSE ANSWERS:

Having your press and chambers in optimum condition can provide big results. By taking care of the mechanical issue in order to optimize the setting of the chamber at the lowest amount of pressure possible, run times for both doctor blades and end seals can be significantly extended. By simply taking the extra 10-15 minutes to clean a deck and an extra 2 minutes to set it lightly and evenly, some issues may be completely resolved. It’s definitely worth investigating before moving on to more involved solutions. CAREFUL SET-UP AND MAINTENANCE: Maintaining the proper viscosity and ink/vehicle/solvent ratio is another very important consideration when it comes to working with white inks. Often, when issues come up with white inks, even though other printing functions have been problem-free for some time, viscosity and solvent ratios are a primary reason behind the problem.

In most cases radius tipped blades are used for any roller under 600 lines per inch (lpi). Switching to a radius tip blade from a lamella or bevel blade may help or eliminate many white ink challenges. Increasing the thickness of the blade may help as well. However, remember, the more steel you throw at the problem, the more it increases anilox wear – so proceed with caution. Many printers elect to use a coated blade to address the wear, quality and press downtime issue with metering white inks. These coatings are generally significantly harder than a standard doctor blade but not quite as hard as the ceramic anilox roller itself. Other ingredients in the coatings can help address coefficient of friction values (COF). These coated blades can greatly increase doctor blade wear but should also be installed in the chambers properly and care should be used setting them. They are significantly higher in cost, though proper care when using them can increase the return on your investment. In some cases, plastic blades have been used with promising results. While this has not proven to work across the board for consistent metering, it may be worth looking into.

Download the full White Inks White Paper for more information. 

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6 Factors of Maintaining Plate Quality

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by Catherine Green, All Printing Resources

6-factors-plate-quality-800x800-300x300Platemaking is a science, not an art. While there is a bit of flexibility in specifications for different processes, there are defined parameters that must be followed if high quality plates are to be made consistently. In this article, we’ll discuss six important factors for making high quality plates.

1. Relief Depth

Relief depth is the difference in height between the printing surface and the floor of the plate. We can obtain this measurement by measuring the overall plate thickness, then subtracting the floor thickness.

There are recommended relief depths for different plate thicknesses:

Plate Thickness Ideal Relief Depth Max Relief Depth
0.045” (1.14mm) 0.018” – 0.022” 0.022”
0.067” (1.70mm) 0.018” – 0.022” 0.025”
0.112” (2.84mm) 0.020” – 0.025” 0.030”
0.250” (6.35mm) 0.050” – 0.070” 0.070”

2. Imaging Quality

Whether you’re using digital or analog plates, the finished plate cannot exceed the quality of the original image carrier. If you’re making analog plates using film, confirming proper film density (over 4.0) is critical. With digital plates, the digital imager must to be checked for correct focus and power settings periodically (every 4 to 6 weeks, or any time the laser head is contacted by a loose plate). These tests can be done yourself with the proper tools and training, by your digital imager supplier, or by APR’s TSG group.

3. Exposure Conditions

Plate exposure units contain two types of UV bulbs: UVA bulbs (for back, main, and post exposures), and UVC bulbs (for light finishing). For maximum plate quality, these bulbs must be monitored and replaced at the end of their useful life. While extending exposure times to make up for weak bulbs can work in a pinch, this tactic sacrifices plate quality. Longer exposure times can lead to broadening of the plate’s shoulder angle, resulting in dot gain and filling in of fine reverse detail (especially with analog plates). In addition, the plate room environment should be kept clean and free of dust to prevent any unwanted debris from contaminating the plate before or during exposure.

4. Polymer Saturation

Both solvent and aqueous platemaking use liquid to wash away the unexposed photopolymer in the plate’s non-printing areas. This liquid, whether a hydrocarbon solvent or water, will eventually become contaminated with dissolved polymer solids. The level of saturation, or percent solids, can have a dramatic effect on both plate quality and equipment maintenance. In solvent platemaking, it’s recommended to keep the concentration of solids below 6% to ensure optimum plate washout and keep equipment maintenance to a minimum. If the solids are allowed to collect above this level, the result can be increased washout time, which results in a longer dwell time in solvent for the plate, culminating in a longer drying time. Extensive cleaning may also be needed to remove excess polymer buildup throughout the system. In aqueous platemaking, weekly solution changes and machine cleanings are key to trouble-free operation. Since aqueous polymer doesn’t dissolve completely in water, there is a chance that small particles of polymer could re-deposit onto the plate if they are not removed from the system. It is essential that these machines are kept clean and proper filtration is used to manage the washout solution. The exception to this rule is thermal plate processing. Since thermal processors utilize a one-time-use wicking media to remove the uncured photopolymer, there is no polymer saturation to monitor– only the amount of wicking media remaining in the machine.

5. Drying

One of the most important, yet most overlooked factors in solvent plate quality control, complete drying is crucial to consistent platemaking. Incomplete drying can be caused by a number of factors including early removal of the plate from the dryer, inadequate dryer air circulation, and improper drying temperature. To check a solvent plate for complete drying, remove the plate from the dryer and allow to cool for 5 minutes. Next, measure the overall plate thickness with a micrometer. The plate should be no thicker than 0.001” – 0.002” over the original plate gauge (be sure to measure the original gauge on a sheet of raw material). When plates are not completely dry, they remain swollen from absorption of solvent. This can lead to problems on press including poor registration, over-impression, and decreased plate life.

6. Plate Handling

Good plate handling and storage practices can save time and money with both press downtime and plate remakes. Plates should always be handled with care, and treated as a fragile component of the printing press. Never place objects on top of plates, fold/crease plates, or expose plates to unknown chemicals. Plates can be only be stacked flat when foam or parchment paper is placed between them to prevent direct contact. Environmental factors that can harm printing plates include exposure to room light or sunlight, and storage near ozone-producing equipment (most common offenders include: HVAC and electrical equipment). To ensure maximum plate life, used plates should be cleaned as soon as they are removed from press using an approved cleaner and a soft horsehair brush. Another great option for plate cleaning is an automated plate cleaning machine. These simple machines make quick work of dirty plates, produce consistent cleaning results with minimal labor, which streamlines the post-press workflow and makes the most of valuable employee time.

By following these simple steps, you will ensure that your platemaking and storage is as efficient and effective as possible.

For more information regarding products or procedures mentioned in this article, contact Catherine Green of APR’s Technical Solutions Group (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.

About All Printing Resources, Inc. (APR)

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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Bringing Gravure Quality to Flexo

TCL Packaging Teams with Creation Reprographics & Asahi Photoproducts to Bring Gravure Quality to Flexo

 

About TCL Packaging
TCL Packaging is a leading UK printer and converter of packaging films. The company provides food and non-food flexible packaging and promotes itself as a supplier of perfectly printed packaging films. TCL partners with Creation Reprographics for plate production. Founded in 1999, TCL Packaging invests in the latest technologies to ensure the highest quality packaging production. It has a team of 55 staff working across reprographics, lamination and ink technical management.

TCL Packaging Managing Director Mike GoldingChallenge
When current Managing Director Mike Golding joined the company in 2009, he saw a need to develop new systems, procedures and go-to-market strategies to bring the company in line with then-current market realities. After completing a management buyout in 2012, Golding set about finding the best solutions to increase TCL Packaging’s competitive advantage, productivity, and profitability, while reducing its environmental footprint.

Solutions
In addition to investing in a new 70,000 square foot facility in Telford and three new Uteco presses, Golding turned to the company’s repro house, Daventry-based Creation Reprographics to find a way to bring gravure quality to flexographic printing. Creation Reprographics was able to help the company meet those requirements using Asahi Photoproducts AWPTM water washable flexographic plates to deliver the photo-quality reproduction that brand owners and retailers seek in the specialty packaging market.

Results
“From the outset, TCL aimed to be a technically capable, high quality packaging producer; and the fact that much of the original team is still in place is testament to the vision and focus we’ve have engendered in the business in recent years,” says Golding.

Dean Langford, TCL Production Manager, attributes much of the company’s success to the focus on teamwork at the site. “We are very demanding as a customer to our supply chain,” he says, “but we also believe that every problem can be turned into a success, as long as there is collaboration. We grow and develop our people internally, and we partner with our suppliers to get the best business and product performance.”

Partnering for Success

TCL & Creation Reprographics Shopfloor

One of TCL’s valued partners is Creation Reprographics. The Daventry-based company’s use of Asahi AWPTM plates was a key factor in establishing the relationship. Founded in 2004 as a reprographics studio, Creation Reprographics provides a range of platemaking, proofing, design and management services. It delivers high levels of customer service for brand, label and wide-web print customers and supports brands with innovative technical production strategies, including moving work from gravure print to flexo for more flexibility without any compromise in quality.

TCL & Creation Reprographics Shopfloor

Whilst flexography has always been a more efficient and cost effective printing process, the challenge has been to close the gap between offset and gravure printing, both in terms of quality and environmental sustainability. Plate manufacturers have been challenged to create a more environmentally friendly plate without losing the benefits and advantages of quality and efficiency; and according to both TCL and Creation Reprographics, Asahi Photoproducts has met that challenge with its AWPTM plates.

Asahi AWPTM Benefits
Traditionally, water washable plate quality has been considered a second-best solution when compared to solvent plates. However, the AWPTM plate does more than match traditional solvent technologies; it outperforms the best digital plates currently available for flexo. For the first time, a digital photopolymer plate can hold extremely small dots, smaller than those of solvent processed plates; and its stability on press is superior to solvent plates. The plate is engineered to deliver a sustainable quality output with fast plate access time. Its water processor keeps water use to a minimum and washed photopolymer residues are filtered, resulting in solid polymer cake that is easily recyclable.

In addition, due to the smaller dot size, low dot gain and high dot stability of the Asahi AWPTM plates, especially when used in combination with the latest generation of screening technologies, as well as its extraordinary ink transfer that minimizes press stoppages due to wash-ups, these plates deliver the best of all worlds – high quality, smooth gradations with vignette fades to zero, environmental sustainability and optimum overall equipment effectiveness (OEE).

“At Creation, we pride ourselves on our approach to the environment,” says Matt Franklow, Managing Director. “We invested in AWPTM Plate technology from Asahi Photoproducts some years ago as part of our environmental strategy. The AWPTM Plate uses water rather than solvent to clean the plates, which has to be better environmentally. And it uses water sparingly.” At Creation Reprographics, rainwater from the site roof is collected, filtered and then used for plate processing before being recycled again, minimising the carbon footprint of the process even further.

A Winning Combination
All of these factors presented a winning combination for TCL. Langford adds, “We’re all about replacement of gravure here at TCL. We initially assessed about five different flexographic plates. But when we began working with Creation Reprographics we were really impressed with the quality standard they could deliver on the Asahi AWPTM plate solution. Working with our repro team, Creation Reprographics took two eight-colour gravure jobs, did extensive colour management and fingerprinting work and delivered them in five colours for our new Uteco line investment, with outstanding performance according to our customer.”

Langford concludes, “The fact that we can drive our print performance up above standard gravure using the Asahi AWPTM plate, says we going to be competing and ahead of the game in the long term.”

And the strategy is working. Today, business is booming at TCL Packaging. For the past three years, TCL has been growing at an average of 10% per annum, which outstrips overall market growth, with the UK flexo packaging market having grown at about 3% annually in recent years.

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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

Download the Flexographics Solutions Guide

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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

Apex-logo-300

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

Get the flexo solutions guide now!

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