Tag Archives: flexography

Dr. John Writes: A Blast from the Past – Flexo Print Fault Guides from the ’90s

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During a recent ‘de-clutter’ session at home I came across my 1998 box of materials from the EFTA in England, and took a quick trip down memory lane with a printed copy of the “Typical Flexo Print Faults” guide from Sun Chemical. As I thumbed through it I was amazed at just how BAD the issues looked when viewed through ‘today’s eyes’. I know the guide contained truly bad cases for each defect to make sure the fault was visible, but to some degree these really were daily occurrences back then. It struck me how few of these we see today, and if we do see them, how they are never present to that degree.

The list of “Typical” Flexo Print Faults In 1998 included:

  1. Poor Trap
  2. Ink Smearing / Dot Bridging
  3. Dirty Print / Fill In
  4. Mottled Print
  5. Print Striations
  6. Uneven Colors
  7. Poor Ink Coverage
  8. Pinholes or Fisheyes
  9. Washboard Print
  10. Dark or Dirty Print Color
  11. Ink Foaming
  12. Weak Print Color
  13. Inconsistent Print Color
  14. Dirty Print / Halos
  15. Dirty Print / Feathering

 What’s with all the Dirty Print?

Did you notice that 5 of the 15 print faults involved the words “Dirty Print”, and several of the others could easily be considered in that type of category? It’s sometimes easy to forget that only 15 or so years ago Flexo had a LOT of issues, struggling with lower quality and a highly inconsistent process.

What is also interesting is that the primary causes of these print faults were not due to a single factor; they were due to issues with the ink, anilox, ink supply, plate, doctor blade, operator, substrate, tape and press combined. The improvements that have been made since that time, and that give us the flexo performance we enjoy today, have truly been across the board – though it’s true to say that they don’t always happen in perfect synchronization.

When one supplier comes up with the latest major advance, it often takes time to completely step the industry forward, because no one component is independent of all the others. As an example, and one that’s close to my heart, when new significant improvements in plate capabilities are introduced, they are supported in implementation over the following years by continuous improvements in the ink, anilox, tapes and the press, until they all come together to unlock the true capabilities of the plate – and vice versa.

The Supermarket Test

It used to be that you could walk down the middle of any supermarket aisle, and a wide one at that, and you could spot the flexo printed products on the shelf from 5 feet away. The typical Flexo halo was often the first giveaway, but now that is very much the exception, and you need to get a lot closer than 5 feet to see it!

As an industry we should be PROUD of what we have done, as suppliers, printers, and service providers, we are now as good, and on most days better than the other print processes that we could only dream of matching back in 1998, on a wider range of inks and substrates than ever before. It’s why we mustn’t stop collectively educating our end users, especially those ones that have long memories, about the capabilities of 21st century flexo.

We’ve come a long way in the last 15-20 years – but it’s important to not become complacent and accept that even the Flexo we are printing today is “good enough”. There is always room for improvement and I know that I, for one, will not stop trying.  J

OK, back to those boxes…

Dr. John’s Contact Information:

John-Anderson-AugFor anyone who does want to email me, please use john.anderson3@kodak.com and please don’t miss out the number 3 in the address, or you will reach another John Anderson in Kodak manufacturing!

Have a wonderful day,
Dr. John, WW Business Development, Packaging, Kodak

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Filed under Print Defects, Printing

Anilox Roll Cleaning Essential to Effective Ink Delivery

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by Flexo Concepts

Anilox_Cleaner_300X298You spend plenty of time selecting the correct anilox roll for a job. Careful consideration goes into line screen, cell geometry and cell volume in order to guarantee that a precise amount of ink or coating is delivered to the substrate. Aniox roll cleaning is essential to maintain this precision. If you neglect to clean your rolls on a regular basis, you will not get the most out of your anilox investment. Plugged cells will affect print quality and cause you frustration, waste and downtime. An anilox cleaning program consisting of daily, weekly and deep cleaning will preserve the integrity of the anilox engraving and ensure quality, press efficiency and longer anilox life.

When a newly engraved anilox roll arrives from the manufacturer, volume is even across and around the surface of the roll. As the roll is used, however, a residual amount of ink or coating material is left behind in the cells after the transfer has taken place. The residue dries and creates build-up in the cells.  Over time, these deposits decrease the capacity of the cells and reduce their ability to carry and release the volume of ink or coating for which they were designed. This residue also raises the surface tension, or dyne level, of the roll and increases the tendency of the coating to “cling” to the surface. When this occurs, the roll will not release the proper volume or ink or coating to the plate.

Benefits of regular anilox roll cleaning:

  • The repeated transfer of a precise volume of ink or coating
  • Consistent coverage
  • Reduced labor and less downtime
  • Fewer job rejections and waste
  • Longer anilox life and lower re-working costs

Flexo Concepts recommends a 3-step anilox roll cleaning program:

1. Daily wiping to prevent ink or coating build-up
Applying a liquid cleaning agent by hand and wiping down the roll with a clean, lint-free cloth on a daily basis is the simplest and most effective way to prevent keep ink and coating from drying and building up in the cells. As a basic rule of thumb, the best time to clean a roll is as soon as it is removed from the press. The longer inks, resins, adhesives, etc. have been allowed to sit in the engraving, the harder these materials are to remove. To maximize cleaning performance, choose a cleaner specifically formulated to remove water-based, UV or solvent-based chemistries based on your application.

2. Weekly scrubbing with a paste-like cleaner and an anilox cleaning brush
brush_ss_orange_450X268
Manually scrubbing the roll once or twice a week with a brush and a paste or cream chemical cleaner will mechanically loosen and remove any ink or coating residue that remain in cells despite daily cleaning. The cleaner is applied to the roll, vigorously scrubbed in a circular motion with an anilox cleaning brush and flushed with water while the roll remains in the press. It is important to remember that stainless steel brushes are suitable only for ceramic anilox surfaces and brass bristles should be used for chrome surfaces to prevent damage to the engraving.

3. Monthly deep cleaning to remove tough ink or coating deposits
Over time a residual amount of ink or coating material is left behind in the cells and the roll requires a deep cleaning to remove these tough deposits. The most common methods of deep cleaning are chemical wash and ultrasonic. The roll is removed from the press and placed into a chemical bath where it soaks in a powerful cleaning solution before being subjected to a high pressure rinse or ultrasonic vibrations to loosen and dissolve the deposits. These methods vary in cleaning effectiveness, risk of damage to the roll, and water and chemical consumption.

Like on other parts of the press, a maintenance program for anilox rolls keeps the ink delivery system running at its peak. Regular anilox roll cleaning will prevent anilox cells from plugging with ink and coating residue and stop build-up before it dries. Maintaining anilox rolls through a regular cleaning program can pay off tremendously in terms of maximizing print quality, press efficiency and cost control.

Click here for more information on our anilox cleaning brushes

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Filed under Anilox Rolls, Cleaning, Printing

Viscosity & pH Control: Increasing Productivity Through Automation

FlexoGuide-600

Paul Lancelle, Technical Solutions Group, All Printing Resources, Inc.

Ongoing control of ink viscosity remains as, arguably, the most significant variable in the flexographic reproduction process. If it is not controlled continuously and closely, uniform ink coverage and accurate color match cannot be achieved. Given the costs of solvent and water-based inks, printing operations of any size can save significant costs by controlling ink viscosity.

A good incentive for increasing your understanding of viscosity is to keep in mind that improper viscosity can cost money: a shift of one second on a #2 Zahn Cup can result in 50% excess ink laydown. Improper or high and low “spikes” in ink viscosity also result in ongoing color management issues, as this same one second shift can result in a change in color measuring dE 2 or greater. Viscosity affects not only the hue and strength of the printed color, but impacts other print quality attributes including ink lay, dot gain and trapping. Additionally, performance properties such as coating weight, drying speed and solvent retention are all affected by ink viscosity.

For water-based ink applications, equally important is the ongoing monitoring of pH, due to the interrelationship that exists between pH and viscosity control. Water based inks rely on precise pH control to maintain resin solubility and stability. While manual monitoring remains the “least expensive” means of monitoring pH and viscosity throughout a print run, it is quite common for these methods to quickly turn into a “tail chasing the dog” scenario due to several difficult to control factors:

  • Inconsistent measurement practices between operators
  • Accuracy of efflux cup
  • Irregular timing between monitor checks
  • Disruptive solvent/amine mix “shock” (too much at once)
  • Pigment differences between inks
  • Varying solvent/amine evaporation points

Whether running water or solvent based ink systems, checking ink manually with a stop watch and measuring cup or automatically with an unreliable mechanical system simply does not meet the demands of today’s packaging buyer in terms of color consistency within a job and from one run to the next.

Of equal significance lies the point of ink temperature control. Temperature is a critical parameter in the printing process, and is very often underestimated. Ink temperature is affected not only by ambient environmental conditions, but by press speed and run length, as well. With the ongoing trend toward higher press speeds, ink temperature control has warranted a greater focus. As ink temperature rises, viscosity drops and evaporation rates increase, resulting in another critical balance point. By controlling the ink temperatures, significant ink and solvent savings can be realized and color stability will improve, as well.

Automated control systems were developed to overcome shortcomings and limitations of manually measuring viscosity and pH. Although automated systems have been available for many years, a better understanding of ink, the printing process and the influence of viscosity and pH on print quality have resulted in improved and more reliable systems. Most new presses sold today, particularly in the wide and mid-web segments, come equipped with varying types of advanced automated viscosity, pH and temperature control systems. It is of common industry agreement that ink viscosity should not vary by more than +/- 5% throughout a run… a standard that is difficult to achieve with manual measurement practices. Most of today’s automated systems feature even tighter tolerances than that. The benefits realized by the printing operation are numerous, but primarily include:

  • Ink and solvent savings-often estimated between 25-60%
  • Print quality and consistency through consistent color reproduction
  • Ink quality is maintained throughout a run
  • Maximized press operating speeds
  • Minimized waste
  • A permanent record for quality control purposes

For these reasons, it is well worth the consideration and investment in retrofitting older model presses with automated control systems. Print managers must select a viscometer/pH control system based on their production needs, and this is dependent upon numerous factors, including operator acceptance, consistent measurement and control, fit with existing equipment, expected cost savings, and maintenance and repair.

FIGURE A “Falling Body” Inline viscometers

FIGURE A
“Falling Body” Inline viscometers

The traditional and prevalently common method of automated viscosity control in the printing industry has been with “falling body” technology. The basic concept is to measure the elapsed time required for a ball to fall, under gravity, through a sample-filled tube. The measurement is taken periodically and is not a continuous measurement. See Figure A.

More recently, the flexo print industry has been moving more towards the adoption of “vibrating rod” technology, which consists of a straight metal rod maintained in resonant vibration by a continuously applied power source. Installed in-line to the fluid flow, the sensor is between the ink pump and printing deck. Using the integrated computer, the viscometer emits sound waves in the ink-much like a musical “tuning fork. “A detection circuit then analyzes the changes in these waves caused by the tiniest of

FIGURE B VISCOWAVE Vibrating Rod in-line viscometer

FIGURE B
VISCOWAVE Vibrating Rod in-line viscometer

variations in the ink viscosity. See Figure B.

The advantages demonstrated with “vibrating rod” technology, particularly when choosing the VISCOWAVE technology offered by New Celio Engineering, are multiple when compared to “falling body” methods. Demonstrated improvements can be seen from:

  • High accuracy rate
  • No moving parts=cleaning not required
  • Easy in-line installation
  • No maintenance
  • No wearing parts
  • Compact and lightweight
  • Full stainless steel construction

In addition, the VISCOWAVE comes with built-in temperature measurement and has options for controlling ink temperature to provide a “complete package” toward automated ink control.

Consideration of the added benefits recognized from the higher accuracy and dependability combined with reduced maintenance and cleaning may lead to printers with previously installed versions of automated viscosity control systems recognizing a significant ROI when upgrading to these newer technologies. The same concept holds true for automated pH control, as earlier systems were often found to be challenging to clean and maintain.

APR represents New Celio Engineering, offering a full line of viscosity, pH and temperature control systems, as well as heat exchangers, wash up systems, mixing stations, solvent and/or ink distribution lines. Customized turnkey solutions can also be provided. To learn mopre about the New Celio System, click here, or contact one of our Technical Specialists.

For more information, call us at 1-800-445-4017, or fill out the Information Request Form.

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Filed under Ink, Printing, Viscosity

Polyester Containment Blades Win over Steel

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Polyester_coil_knockout_300x135For such a seemingly insignificant part of the press, the containment blade’s job is an important one.  After all, it is a fundamental component of the doctor blade chamber.  By forming an enclosed system, the containment blade plays a key role in allowing the printer to maintain ink viscosity, minimize skimming, lower ink consumption and simplify cleanup.

In wide web applications, choosing polyester containment blades over steel is a smart way to save money, improve safety and reduce your environmental impact.  Unlike the metering blade, which has a direct impact on print quality, the containment blade only has to contain ink in the chamber.  This gives a printer more options to choose from with regard to blade materials.  Learn why polyester is a superior choice over steel.

Top 5 reasons to switch to polyester containment blades:

  1. Trail doctoring – Some printers experience trail doctoring at higher press speeds when using steel containment blades. Steel blades are too stiff to allow back-doctored ink to pass underneath the blade and back into the chamber.  Ink builds up on the back side of the blade, pools at the end of the chamber and eventually slings onto the press and web.  This situation not only creates a mess but also affects print quality.  Printers can eliminate trail doctoring by using polyester containment blades.  This material is equally effective at containing ink in the chamber but thin and flexible enough to let back-doctored ink return to the chamber.
  2. Cost – Polyester containment blades cost substantially less than steel blades. The price per inch for polyester typically ranges from one-third to one-half that of steel.
  3. Safety – By replacing one of the steel doctor blades in a chamber with polyester, you can reduce your risk of doctor blade injuries by 50%. Unlike steel, polyester blades are safer to handle than steel and won’t cut press operators when they are installing and removing them from the press.
  4. Environmental impact – During production, polyester blades emit a small percentage of carbon dioxide compared to steel blades. Using polyester containment blades can help printers meet requirements for reducing their carbon footprint.
  5. Anilox damage – Polyester containment blades will not score or damage anilox rolls. The material is soft and contains no sharp fragments which can break off, become lodged against the roll and destroy the engraving as the roll turns.  The material is non-abrasive and won’t cause excessive wear on the roll.  Replacing or re-engraving anilox rolls is expensive, so extending their life can be a huge cost savings.

Printers are always looking for ways to improve efficiency and save money.  Why not choose a containment blade that not only costs less but also has additional pressroom benefits?  Polyester containment blades offer a less expensive and safer alternative to steel that also reduces trail doctoring and environmental impact.  It’s amazing how such a small change can make such a big difference!

Request a Polyester containment blade sample

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Filed under Doctor Blades, Printing

Are you experiencing Pin-holing and Production Pitfalls? – Part 2

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In the previous Part I of this blog http://www.flexoglobal.com/blog/, I talked about the ink transfer process in flexographic printing and how it can introduce the problem knows as pin-holing. Over the years, manufacturers have tried to solve the problem in various ways with limited success. Likewise, flexo printers have tried to compensate for the pin-holes by applying more ink to the job, and more pressure on press, but that only drives up costs and introduces other complications.

The best way to solve the problem is to use a specific imager technology to apply a texture pattern on the surface of the plate that breaks up the surface patterns from the anilox roll. By breaking up the anilox pattern, it breaks up the pin-hole pattern, and significantly improves the ink transfer. As I noted in my last installment, that solution exists today and has been driving improved quality in flexo around the world.

Kodak’s innovative, award-winning KODAK DIGICAP NX Patterning is a standard component of the KODAK FLEXCEL NX System designed to address these ink challenges in flexo—specifically solid ink densities compared to gravure printing. Enabled by KODAK SQUARESPOT Imaging Technology, unique to the FLEXCEL NX System, the function of DIGICAP NX Patterning is to image a unique pattern into the surface of the plate.

Compared to traditional surface patterning technologies, DIGICAP NX Patterning is significantly smaller and finer. It is a true micro surface texturization of the plate surface, applied to the 1-bit TIFF in the RIPing process, and utilizing half-pixel imaging at 10.6 x 5.3 microns size, or 2400 x 4800 dpi.

With the ability to create unique patterns in the surface of the plate that overcome production challenges with heavy solid areas, or the application of white ink for flexible packaging, users are seeing dramatic quality improvements. Because of the improved ink transfer, printers are able to more easily achieve their target densities and eliminate the need to chase density with more ink, more pigment, and more pressure. For flexo printers, the result is greater color gamuts, cleaner brighter colors, better print quality, higher print speeds, and greater consistency.

Why are color gamuts improved with this solution? Because the solids are clean rather than being pin-holed, which results in light and dark variation in the colors, often the cause of the term “muddy” colors associated with Flexo. Also, when overprinting to build colors such as in 4- or 7-color process, the results are cleaner and brighter. Having the ability to build cleaner and brighter colors enables flexo printers to do more of their work with process printing instead of having to rely on more expensive spot colors. It also improves the printer’s ability to standardize ink sets, whether for 4- or 7-color process printing.

DIGICAP NX Patterning has been one of the lead technologies in the “flexo revolution” over the last five years, truly allowing printers to achieve the densities of gravure printing, and helping to stop the chase for density caused by excessive pin-holing with traditional flexo. It has been a key enabler in brand owners increasingly accepting that flexo is no longer a second-class print process, easing the transition from offset and rotogravure to flexo.

Innovation in flexo is an ongoing process, and one in which Kodak maintains a passionate commitment. R&D teams continue to explore additional areas where differentiated plate imaging technology can further increase print quality and reduce or eliminate production obstacles. As we look to the future, Kodak technologies such as DIGICAP NX Patterning, SQUARESPOT Imaging Technology, and KODAK HYPERFLEX Imaging Software will provide the foundation for technical advancements in flexo.
Printers are certainly benefiting from these innovative imaging technologies, but they are not the only ones. Brand owners are constantly looking for ways to design packages that catch the eye of the consumer and set their products apart from the competition. Print quality, color vibrancy, and reproduction accuracy are top of mind for marketers—it’s the job of the printer to make it happen and to keep costs in line.

Dr. John’s Contact Information:

John-Anderson-AugFor anyone who does want to email me, please use john.anderson3@kodak.com and please don’t miss out the number 3 in the address, or you will reach another John Anderson in Kodak manufacturing!

Have a wonderful day,
Dr. John

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Are you experiencing Pin-holing and Production Pitfalls? Part I

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Flexographic printing technology, like all other printing technologies, relies on the transfer of ink to a range of substrates. With flexography, that transfer begins with the anilox roll, which is designed to enable a controlled, predicatable transfer of ink to the plate surface. Ideally, the ink is transferred to the surface of the plate as a series of dots, but in reality, rotation of the anilox roll often turns the dots into ridges. So the ink transferred from the plate to the substrate can contains ridges and voids—otherwise knows as pin-holes.

Because the ink layer is not continuous, the printed piece suffers from a loss of density and color vibrancy. To get the highest possible density with the least amount of ink, the ink needs to be printed in a thin continuous layer, with no voids. If you can accomplish this, the light from the source reflects evenly and continuously to the observer—in this case, to the consumer viewing packaging on the shelf. But trying to apply more ink to counteract the problem increases drying times and slows presses down, and applying more impression to increase the density results in compressed highlights and reduced tonal reproduction.

More ink also requires the use of a higher volume anilox roll, but these rolls often have lower LPI value, with bigger cells and a larger gap between the centers of each ink dot. What you get then are potentially larger voids between the ridges of ink.

Over the years, several approaches have been developed to try to eliminate pin-holes in flexographic printing. One such approach is to reduce the amount of gap between the anilox cells on the roll. This can also increase the ink flow, but there are production limits on how much this can be done. Another option is to change the surface of the plate, which typically involves creating small cells in the surface of the plate that carry ink in an attempt to transfer more ink to the substrate, but this increases ink use, drying demands, and slows the presses further.

Another newer alternative is to use a specific imager technology to apply a texture pattern on the surface of the plate, like regular rectangular islands surrounded by a thin sea of ink that breaks up the cell pattern from the anilox roll. By breaking up the anilox pattern, it breaks up the pin-hole pattern, and significantly improves the ink transfer.

By breaking up the pattern, this solution allows the transfer of the ink in a smooth layer without the large pin-holes, resulting in cleaner brighter colors, and higher densities, with the same or lower ink laydowns. Also, it should be noted that contrary to popular belief, solid densities are impacted more by the smoothness and eveness of ink laydown than they are by the actual volume of ink transferred, and increased densities with lower ink laydowns allow for better overprints for cleaner and brighter expanded gamuts, without adversely impacting drying times or press speeds.

The key is that better ink transfer allows printers to achieve their target densities, generally eliminating the need to chase density with more ink, more pigment, and more pressure. These features alone often allow printers to achieve greater color gamuts, better print quality, higher print speeds, and greater consistency.

So how do you modify the plate surface to create these surface texture patterns? With the right technology, it’s a fairly simple process that yields impressive results and opens up many more opportunities for flexographic printing.

Learn more on the technology that will prove helpful to address “Pin-holing and Production Pitfalls” you may experience – read Part II of this series next week.

Dr. John’s Contact Information:

John-Anderson-AugFor anyone who does want to email me, please use john.anderson3@kodak.com and please don’t miss out the number 3 in the address, or you will reach another John Anderson in Kodak manufacturing!

Have a wonderful day,
Dr. John

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Filed under Print Defects, Printing

Exposure Bulb Tips

FlexoGuide-600by Catherine Green†, All Printing Resources

Why should I replace my bulbs if they still illuminate?

nyloflex-FIII-Combi-300x300UV-A and UV-C exposure bulbs lose output intensity over time. The gases inside the bulb become inert, resulting in longer start up time while the UV output diminishes. This results in longer, inconsistent exposure times.

If you have an integrator on your exposure unit you may not be aware of the change because the integrator compensates for the difference. We suggest a weekly test of the number of seconds that correspond to the number of units for your standard exposure. This will enable you to determine how much strength your bulbs have lost. If you do not have an integrator, we suggest doing a weekly exposure test using your own test image or one supplied by your plate supplier. This image should contain all of the standard elements needed to properly evaluate the plate. These include, various screen tints, isolated dots, lines, type, solids and reverses. By using the same exposure time each time and saving the last test plate for comparison you will be able to see any noticeable change in your exposure times. The most efficient method to test your bulbs is to use a UV-A meter. This unit reads the bulb intensity and produces a numerical reading. You can record the readings and determine when your bulbs need to be replaced. It is widely recommended to replace your bulbs once they reach 10mW/cm2 or below, although this number can be higher for high-LPI work and HD Flexo.

A note about exposing HD Flexo plates:

Esko recommends UV-A output no lower than 18 mW/cm2 for all HD Flexo plate exposures. We have found that this guideline can vary depending on the photopolymer used. The APR Technical Solutions Group can assist you with specific questions (Contact us).

When you first turn on the power to your equipment (cold start), it provides high voltage until the bulbs light. This strains the starting circuitry, power supply and the quartz (glass) of the bulbs. If you allow excessive start time to the cold start and exposures with old lamps you risk equipment failure.

Unreliable and inconsistent bulbs can cause re-makes and wasted material. We suggest bulbs be replaced before they burn out. Save a few of your old ones as temporary replacements. When replacing bulbs, replace all of them at the same time. This will give you quicker exposure times and your equipment will operate at maximum efficiency.

How can I get the maximum usage from my bulbs?

Here are a few simple steps to get the most from your investment in new bulbs:

  • Use cotton gloves when installing new bulbs. If you clean them before use and install them using gloves you will avoid the oils from your fingers and other contaminants that can cause premature failure due to the high operating temperature in your exposing equipment.
  • Clean your bulbs on a regular basis to ensure the maximum reflected light.
  • Check the electrical contacts regularly for pitting or corrosion, which can cause arcing and failure of the bulb or equipment.
  • When installing new bulbs, apply pressure at the ceramic or metal ends never apply pressure to the quartz.
  • If your exposure unit has cooling fans and or filters, clean the blades, lubricate the motor bearings as needed, and check to make sure the fans are operating properly. The vents must be clean and free of any obstruction to allow for maximum ventilation and unrestricted airflow. Keeping your bulbs cool will improve their life.
  • Make sure that the bulbs you are using are the correct type for your equipment. Many units require specific spectral output. If you change types, make sure your equipment is compatible.
  • When you install new bulbs, record the date, life hours and bulb part number. This simple record will help you establish an effective maintenance and replacement schedule.

And lastly, don’t be intimidated by equipment manufacturers who insist you use only their brand of bulb. The bulb simply receives the output from the power supply, so it cannot harm your equipment. Just be certain to buy from a reliable supplier that will make sure you have the correct bulb for your equipment, and be able to help you should a problem arise.

As LED exposure technologies become more popular, it is important to note the difference between these technologies and bank light systems. LED systems have variable output, so the light intensity can be easily controlled and adjusted. Also, LEDs are temperature-controlled and instantly light to full power, so there is almost no variation in the exposure process. APR represents both Esko’s Inline UV exposure solutions, as well as Flint Group’s NExT flat-top LED exposure technology.

† Based on an article originally written by Larry Dingman in November of 2002, updated in August of 2014 by Catherine Green.

For more information, contact us using this link. Also, read this related article by Catherine Green on our TSG Blog: UVA Light Sources Exposed.

About the TSG:

We have formed our Technical Solutions Group to encompass our full range of expertise in all critical areas of the flexo process. This team is made up of industry professionals dedicated to being up to date on new technologies, armed with the last in diagnostic tools, and experienced in problem solving that can achieve sustainable results. The TSG have walked in your shoes, and has felt your pain. For any specific questions about determining plate wear through reflectivity readings and 3D color mapping or assistance in determining your plate wear pass/fail limits, please feel free to contact us.

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Filed under Plate Technology, Printing

Minimizing Plate Costs Part 3 – Identifying When the Plate is Worn

FlexoGuide-600

By Tim Reece, All Printing Resources

Introduction

Image of slightly worn plate edg

Image of slightly worn plate edg

I think many would agree that it is easier to take steps to help extend plate life and minimize damage to the plate than to effectively recognize a worn plate in need of replacement. As a matter of fact, the odds are often greater that the plate will be damaged, lost, or require a change in artwork before it can be deemed “worn out”. One of the most difficult questions to answer in our industry is, “How long should my plate last?” or “How many feet or impressions should I expect to get out of my photopolymer plates?” If we all knew the answer to these questions, then throwing out worn plates would be as easy as tracking the footage. But considering the number of factors that must be taken into consideration this is not a reasonable expectation.

Graph of the same plate edge - showing the shoulder profile

Graph of the same plate edge – showing the shoulder profile

A few months have passed since we explored some of the more common but less controlled causes for replacing the photopolymer printing plate in Part 1 & 2 of this series. During the past few months, we have uncovered a tool that makes identifying a worn plate far easier than ever before. Part 3 will focus on how to properly identify a worn plate and take the “guess work” out of the decision to replace the plate.

The Problem

Plate wear color mapping. As plates wear the worn edges change hue.

Plate wear color mapping. As plates wear the worn edges change hue.

How many times have you witnessed a long production run slowly drop off in image quality during the printing process? There is a common reaction to this circumstance. (1.) Take a deep breath, cross your fingers, and hope you can make it to the end of the run. (2.) Start making a deal with GOD, promising that if the plates just last until the end of the job, you promise to never use them again, and this time you really mean it. (3.) Stop the press…

It is after the press is stopped, that we come to a split in the road. Do we take a chance that replacing the stickyback will be enough to get us by or do we replace the plate? The truth is that it can often go in either direction. Unless the edges of the plates are clearly visibly worn, or the screens are breaking down, we just don’t know what to do at this moment. Replacing the stickyback could take 10-20 minutes, but it may not fix the problem. If it doesn’t correct the problem, we then have even more downtime without the proper action being taken. Depending on plate type, a replacement plate could take 1-3 hours and that’s if platemaking is on-site. Then there is the sickening thought of making or ordering a new plate only to find out the first one really wasn’t worn out.

3D Image of same plate with slightly worn edge.

3D Image of same plate with slightly worn edge.

The Solution

The best way our Technical Solutions Group (TSG) has found to determine if a plate should be identified as “worn out” is through image analysis and/or 3D plate scanning. The most effective means found to determine wear on the plate was through 3D color mapping, as described below. As each of these plates wear, the surface also changes. Most often the wear shows at the leading or trailing edges. Depending on the type of plate, the wear can either begin to polish the plate, making it more reflective in worn areas, or on some polymer materials with an already smooth surface, wear can have a roughing effect. Regardless of the direction it takes, in each situation there is a measurable change and there is a definite reduction in plate height in the worn area(s).

The Tool - Troika AniCAM 3D Scanning Microscope

The Tool – Troika AniCAM
3D Scanning Microscope

Using a 3D microscope, the process of identifying plate wear becomes much easier to determine. 3D dot profiling allows you to check surface topology of solids, dot shape, relief depth (even between dots) and detect the first signs of plate wear. The AniCAM 3D Scanning Microscope with Flexo Plate QC is easily

positioned onto the photopolymer plate and physically does not touch the area analyzed. This particular device is portable so measurements can be taken in the press room, the plate room or in the plate storage area. 3D color mapping shows distinct color differences as the plate experiences wear in increments as small as a micron. Wear can be identified using this method far before differences in plate thickness could be detected on a plate micrometer. Note: 1 micron = 0.00003937″. An added benefit to this method is that it can be done while the plate is still mounted to the sleeve or print cylinder, further minimizing press downtime.

A Two-Step Process

The first step in establishing a system to identify worn plates is to establish a target that will most likely fail in the trim area where run control targets are likely to exist. Your first inclination may be to use an ultra-highlight dot patch, but a solid patch is often a better choice. Tonal patches often have the ability to absorb some of the abrasiveness of the anilox and substrate, whereas a solid polymer surface only has the compressibility of the stickyback and often show the first signs of wear. It’s kind of like the flexibility your hand has when the fingers are extended compared to rolled into a fist. The solid patch could be as small as a ¼” square area. The nice thing about wear first showing up on the edges of a solid is that you can establish your “fail” benchmark before process or screen areas are affected. You may decide to insert a fine .5 pt horizontal line ¼” wide, or even isolated dots as “fail areas”. The targets you design should be based on your experiences and what you see failing first.

The second step is to create a pass/fail benchmark. If using a conventional plate reading device, take a reflectivity reading on what has been established as “target(s) likely to fail”. Each reading only takes a moment, but takes into account roughly 700 reflectance % data points across region of interest (ROI) and they can be plotted in either the horizontal or vertical axis to avoid laser signatures that can give misleading results. If using an AniCAM with Flexo Plate QC, you will simply place the device on the plate on what has been established as “target(s) likely to fail” and with one click the device will build a 3 dimensional image of the plate surface along worn targets. Take these readings from the point the plate is new, through varying degrees of plate wear, i.e. skipping edges, loss of image sharpness, all the way up to the point of failure. We found that once wear was evident .002″ in from the plate edge that it would quickly become visually apparent and then spread to screen areas. Your pass/fail will likely depend on plate type, thickness, and durometer.

You will be tempted to want to associate and assign a “moderate wear” or a “fail” to the number of impressions or footage while performing this step. The amount of impressions and footage experienced is only one small factor of plate wear. DO NOT assume that the plate knows how long it has run and when it’s time to quit. There are too many changing variables to base plate wear on footage or impressions alone. What you will find is a pass/fail tolerance which has quantitative data to support your findings.

About the TSG

We have formed our Technical Solutions Group to encompass our full range of expertise in all critical areas of the flexo process. This team is made up of industry professionals dedicated to being up to date on new technologies, armed with the last in diagnostic tools, and experienced in problem solving that can achieve sustainable results. The TSG have walked in your shoes, and has felt your pain. For any specific questions about determining plate wear through reflectivity readings and 3D color mapping or assistance in determining your plate wear pass/fail limits, please feel free to contact me at 847-922-0134 or treece@teamflexo.com.

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Filed under Plate Technology, Printing

Dr. John Writes: Digital Printing – Friend Or Foe For Flexo Printers?

why-in-the-world

By Dr. John Anderson

As I travel throughout the US & Canada these days, the conversations often turn from flexo, to digital printing as the technology for the future. If you listen to the marketing hype then digital is poised to take over from flexo as the process of choice for packaging. I guess one day this may be true, but is it really imminent?

What makes me smile most about the conversations is the thought that it has to be one technology or the other, where in reality a combination of the two, producing products for the optimum cost and efficiency, is the most likely solution for a LONG time to come.

When I started my PhD back in 1993, researching screen printing at the University of Wales Swansea, it was a 3 year research project sponsored by the UK government and the Screen Printing Association, with 30 screen printer companies as members of the project group. The drive behind the project was the emergence of digital printing, and how it was being marketed to wipe out and replace the screen printing industry within a few years. Sound familiar? There were huge issues in the screen printing industry at the time, with companies experiencing, in some cases, waste in excess of 50% of all of the raw materials, high costs, and bottlenecks with the slowest of the major print processes. In reality a perfect target for the digital printing technologies.

Half way through the project, just 18 months later, all of the project member screen printing companies were still in business, and every one had added some form of digital printing to their business. Instead of eliminating all of the screen printing, it was used to replace the high waste loss making short runs and allow the screen printing process to be used on more profitable jobs. By combining the two, it allowed the printer to reduce costs and increase profitability. In fact many of the printers commented over time that the digital printing services helped to attract more new clients, who then also gave them their screen printing work as well, making digital a true friend and not a foe!

Today, 19 years later, digital now has a much larger % of these companies, in some cases 100% of the business, but in many others screen printing is still used where it has technical or economical benefits over digital in terms of ink film weight, specialty inks, investment costs, or a number of other reasons.

So as we look at the packaging market, can we expect the same to happen with flexo and digital printing? I think the simple answer is yes, but in a long time from now! Flexo is still a strong and rapidly growing print process with many benefits and advantages that will make it a much tougher to replace than screen printing, or even litho in commercial and book printing.

Digital printing has come a long way. The new technologies and presses promise new levels of productivity, but they still face challenges in speed, substrate compatibility, conversion requirements, and food contact regulations, etc. High speed continuous inkjet seems to be the most likely contender to address the speed and productivity and ultimately the food contact regulations will be solved without the high cost barrier laminations of today, but the challenge to take over from Flexo remains a significant one.

There are certainly parts of the market today that are better suited to digital technology; narrow web labels is a clear example. At the last Labelexpo over 40 companies promoted their versions of digital printing presses. This year in Chicago there are sure to be even more! The challenge is how to transition from short runs and variable data, to producing millions of labels, or shrink wraps, or pouches with fixed graphics, and be able to do it economically.

There are thousands of flexo presses in the market, most are already paid for, many running at speeds of 1000-2000 ft/min on a 50+” wide web CI press, or 300-800 ft/min on a narrow web press. To match the productivity of one new fast change wide web CI Flexo press will take 3 or more digital presses, with each digital press costing as much if not more than the Flexo press. The economics of the press costs and replacing existing equipment may be digital’s biggest challenge in the next 15+ years.

A key benefit of the digital press has always been no plates, and instant change overs, but the quick change sleeved flexo presses, standardized process printing, and minimal startup waste focus, has somewhat eliminated most of the benefits for digital for all but the shortest runs. Plus as more printers move to co-printing multiple versions of jobs side by side, for example 4 cookie varieties run side by side instead of 4 individual jobs at 4 across each time, this reduces the flexo plates used on this set of jobs to just 25% of before, and increases the run length to be 400% longer, lowering costs and increasing productivity.

Flexo has also gotten smarter, higher quality, faster, and more productive, raising the bar daily for the digital offerings. Flexo today can also match or better the quality of digital, a fact that was certainly not true 5 years ago, so quality is no longer a driver to choose digital. The amount of packaging in each supermarket or store, and the number of stores globally, means that the challenge is way beyond any of today’s digital printing presses.

In the near term one area that digital and flexo WILL work together is in hybrid systems. Combining flexo and digital in-line, with flexo printing the standard overall graphics, and digital taking care of the identification, ingredients, etc., especially for the number of languages in Europe, etc., This practice is already starting to be seen, but for mass volume commercial viability production must be at flexo speeds, and not slowed significantly by the digital printing. It is exciting to see digital print technologies coming into the packaging space now that are starting to make this a reality.

The next wave of enhancements for digital printing will include hybrid technologies combined on existing presses,that add variable data and QR codes to help drive customer interaction, or brand value in the perception of the end customer, or security information with offset and flexo presses for packaging, to enhance and/or protect the final product.

As a flexo industry we should not be afraid of digital printing at all, instead we should be looking at how can we leverage and use digital to grow and enhance our businesses, and give our end customers and brands more of what they are looking for.

I am looking forward to seeing many of you at Labelexpo in Chicago this year, one of the best places to see the latest and greatest in flexo and digital technologies, and judge for yourself where the future is heading.

Dr. John’s Contact Information:

John-Anderson-Aug

For anyone who does want to email me, please use john.anderson3@kodak.com and please don’t miss out the number 3 in the address, or you will reach another John Anderson in Kodak manufacturing!

Have a wonderful day.

Dr. John
john.anderson3@kodak.com

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Filed under Plate Technology, Plates

Dr. John Writes: Do You Accept Things as “NORMAL” in Flexo that You Should NOT Accept Any More?

why-in-the-world

Throughout my time in the flexo market I have continuously been involved in research, training, troubleshooting, and projects to revolutionize the industry. Sometimes the results are small, sometimes big, sometimes accepted, but most often resisted. Most often the answer when I ask “Why do you do that?” is “because we always have!”

After a while you get into the same habits, and without realizing it you end up in the same mode of “that’s normal for flexo” and accepting some things that you really should not. We all do it! One example that comes to mind is “I have to choose between good highlights or good solids, I can’t have both!” This comes from the typical pinholed nature of the solids in flexo and the four main actions that people take to address it:

  1. Increase the amount of ink used with higher anilox roll volumes
  2. Increase the ink strength with more pigment
  3. Apply more impression pressure from the plate to the substrate
  4. Separate the screens (highlights) and solids onto two separate plates for that one color

However, when we look at each of these four “normal” actions in flexo, because of the need to choose between highlights and solids, we see the true results:

1. MORE INK! Adding more ink does not eliminate the pinholes in the solid, but instead it applies larger ridges of ink to the substrate surface. More ink means more raw materials, more solvent to remove in drying; more drying means more energy as heat. More dryer energy often means that there is a need to slow the press down to achieve this, resulting in lost productivity. These are all “normal” actions in flexo, resulting in more raw materials, more energy, higher costs, and reduced productivity.

Other issues with using more ink are that it tends to cause more dirty print, which causes more stops to clean the plates, and increases the risk of damaging the plates. This is a cost in time, productivity, and materials, but results in inconsistent print quality, and often negatively impacts subsequent processes such as lamination and slitting/conversion when the materials need to be stripped out. A common accepted “normal” action to reduce the risk of dirty print is to reduce the applied resolution, as LPI, making the minimum dots bigger, decreasing image quality capabilities.

2. MORE PIGMENT! Pigment is the component of the ink that provides the color we are looking for, and the theory is to use more pigment for more color. But when the ink is applied in ridges separated by pinholes, the effect and value are minimized. The best way to get the strongest and cleanest color is a thin even layer of pigment with no pinholes, more like what we traditionally see in gravure printing! The light then reflects more evenly, giving a cleaner, brighter, and stronger color.

Pigment is one of the most expensive, if not the most expensive, components in the ink, so adding more increases the costs significantly. Also if you keep adding pigment, density goes up until it reaches a point at which it interferes with the ink flow and can cause the density to drop. Most flexo inks are pigmented to the maximum, often beyond the optimum value for efficient printing. Ink flow is a critical factor, especially as press speeds increase, and poor ink flow will result in ink starvation and poor solids.

This can also cause increased dirty print in a similar way to more ink volume in the first action, with similar solutions to address it, resulting in higher costs, lower productivity, and lower image quality!

3. MORE IMPRESSION PRESSURE! This is something that every flexo printer in the world seems to know—that when you apply more impression pressure from the plate to the substrate, the density goes up!

When you ask why, not many can explain it to you, but they know it just works! The explanation for this is actually very simple—the ink is applied in ridges separated by pinholes or voids; and as you apply more pressure on the top of the ridge, the ink is squashed sideways, filling the voids and increasing the ink coverage, and increasing the density achieved!

 dr-john-5-1

Image 1: Typical Flexo Solid – showing the ridges of ink and pinholes

Unfortunately most also work on the principle that “If a little more impression pressure is good, then a lot more must be better.” This results in over impression, and that introduces a whole new set of issues.

Over impression causes excess dot gain in the highlights, accelerated plate wear in the highlights, and ink build up for dirty print. Although true for flat top and round top dots, the issues are particularly true for the round top dots of traditional digital LAMS (Laser Ablative Mask System), with the very small surface area being very sensitive to the pressure, growing rapidly, and causing excess heat and friction to wear the smallest dots. This accelerated wear, along with impression sensitivity of traditional LAMS plates, causes greater operator sensitivity and inconsistency in setup and through the run.

Over impression also tends to drive the ink off the smaller dots to the edges more, causing ink build up, resulting in dirty print. This then means more stops to clean the plates and that increases the risks of plate damage. Increasing the minimum dot size can help—with a lower LPI for the image, larger dots are less sensitive, tend to be flatter on top, and distribute the impression better. But doing this is a clear sign of accepting that this is normal to compromise the highlights to improve the solids.

4. SPLIT SOLIDS & SCREENS! This is really a sign of having to throw in the towel and accept that instead of one or the other you need to get the best of both worlds. This is a normal action with traditional LAMS plates with their rounded tops, and less often with the digital flat top dot solutions. This means more prepress—two plates, two mounting tapes, two inks, two print stations to setup, two driers to run, etc. Basically more materials, more energy, so more costs. One thing in its favor is that doing this means the plate suffers less from ink starvation and drying issues, and often runs easier and faster at times with traditional LAMS plates.

These four actions are “normal” and accepted as necessary throughout flexo, and in the past they often were needed. Today however this is not true.

The micro plate surface texturizations designed to break up the pattern that causes the pinholing in the ink transfer—like DigiCap NX introduced by Kodak in 2010, which minimizes pinholing without needing more impression pressure—has resulted in a very new situation. Now the ink volumes and pigment loads can be reduced, with often 25 percent lower anilox volumes. This means less ink is used, fewer raw materials, lower cost materials, and less energy to dry, plus this can often mean higher press speeds in turn.

All of the micro surface texturizations like DigiCap NX, or its closest clone, help the densities achieved! Kodak DigiCap NX is the simplest with no loss of imager speed or increased costs. They all require flat top dot structures without oxygen inhibition to form correctly on plate, which also helps with greater impression latitude and plate life. But only Flexcel NX with pixel for pixel imaging to gives you the optimum imaging in the highlights. The others all give up the positive effect for the highlights in traditional LAMS imaging of dot sharpening through oxygen inhibition shrinking the dots to be smaller!

dr-john-5-2

Image 2: Solid produced with same anilox roll and ink as Image 1 using DigiCap NX

The days of choosing highlights or solids are almost past us now as a normal practice, unless you are still using the rounded top dots of traditional LAMS plates! Yet many people still seem unaware that they don’t need to make that compromise, or accept its resultant effects in terms of costs, materials, and productivity.

Isn’t it time you proved to yourself that you don’t need or want to compromise in the same way anymore, and you really can get both at the same time? So why not try for yourself, either with Flexcel NX, alone or head to head with the competitions best? I know you will glad you did.

Dr. John’s Contact Information:

John-Anderson-Aug

For anyone who does want to email me, please use john.anderson3@kodak.com and please don’t miss out the number 3 in the address, or you will reach another John Anderson in Kodak manufacturing!

Have a wonderful day.

Dr. John
john.anderson3@kodak.com

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Filed under Ink, Plate Technology, Print Defects