Manufacturers of anilox rolls, and the converters who use them, continue to push the developmental boundaries of these critical flexographic tools.
By Michelle Sartor
The anilox roll is a unique component of the flexographic printing process. It is the only process by which ink is transferred to the plate by use of a roller into which billions of cells have been formed. As with any piece of equipment, those involved in flexo are trying to improve the performance of anilox rolls to improve the quality of print jobs.
Anilox rolls are engraved with cells that pick up and transfer the ink. The amount of cells per inch is measured through the line count, which is the number of cells per inch. Anilox rolls with higher line counts transfer less ink to the plate because the cells are smaller in all dimensions, but more printed detail can be obtained. Manufacturers are constantly working on development of cells and more effective line counts. Mike Huey, technical graphics manager for the Western division of Harper GraphicSolutions in Charlotte, NC, USA, says, “Some of the most significant developments are the use modified thermal YAG lasers and high-end optics. Better optical designs give us better beam clarity and control of the beam while the newest lasers allow us to engrave higher line screens and higher volume.”
Samples of anilox rolls, courtesy of Stork
David Lanska, Midwest regional sales manager for Stork Materials Technology in Milwaukee WI, USA, says, “For us, the fiber laser engraving technology we introduced the industry to a few years ago has become the new mainstay, rendering YAG for all practical purposes obsolete. Because the cell wall linings are extremely smooth, there are less gripping spots for ink to stick to. As a result, the cells don’t tend to plug up as easily and clean up easier than rolls engraved with YAG lasers. Because these rolls require less time in the cleaning system, they experience less wall deterioration.”
Stork also offers its Xtreme Volume Anilox to converters. Lanska says, “While not suited to every situation and ink type, Xtreme Volume allows printers to achieve color at higher line counts for striking process printing with distinctive image detail, smoother screens, flowing vignettes, and enhanced tonal ranges. In the center ranges, Xtreme Volume Anilox provides rich solid densities and intense fluorescents, while on the low end of the line count scale, printers achieve tantalizing results with adhesive laydown, dimensional varnish effects and milky opaque white.”
John Batistatos, narrow web division of Praxair Surface Technologies in Alsip, IL, USA, explains his company’s anilox offerings: “Praxair has developed specialty engravings that differ from standard 60 degree engraving. These specialty engravings are an open cell technology that gives our customers a variety of advantages. These engravings are called ART, RFID and REV. ART technology is used for applying highly viscous materials such as adhesives, coatings and solid colors. Its tremendous laydown makes it great for heavy solids and where customers have had problems in the past with pinholing. Customers are also seeing increased opacity on white inks by using ART. RFID technology is designed specifically for those customers printing RFID antennas and have to lay down silver conductive highly viscous inks. REV technology has benefited customers by allowing them to print multiple jobs with the same roll. It allows them to print heavy solids and fine dots with one engraving and reduces the amount of rolls they have to inventory.”
Developments continually occur with anilox rolls because companies are always trying to improve their production. Todd Luman, technical lab supervisor for Harper GraphicSolutions, says, “A common goal among anilox manufacturers is to manufacture an anilox roll that is more robust, resistant to scoring and possesses the release properties of a chrome roll. The bar is constantly being raised in our industry to match the print quality of gravure. From the anilox side, we are creating engravings that will aid the printer in doing so.”
Because new products are not necessarily proven, acceptance can be slow. Luman says, “Anything new is different and sometimes different is viewed as wrong. It all depends on the converter. Some don’t want to change or try something new. Others are receptive, want to be on the leading edge and have embraced the new technology and worked through the bugs to get their process in control. I think those that are complacent will be surpassed.”
Carol Harrison, technical sales representative of CTS Industries in Cedartown, GA, USA, believes adoption among converters can be slow. “Most are impressed with the new technology, but they will continue to work with conventional products until the demand and cost for the new designs are justified,” she says.
Cells of an anilox roll. Photo courtesy of Stork.
Lanska says that at Stork, “We have had overwhelming response to fiber optic engravings for general, all-purpose anilox rolls. Xtreme Volume is better suited to several specialty areas.”
Huey says, “The converters have embraced the technology especially for high-end anilox rolls and it is not uncommon to see narrow web printers consistently using 1400 to 1600 line count anilox for process printing at 175 to 200 line screen plates.”
Traditionally, narrow web converters have used anilox rolls with line counts below 1000. Line count has been increasing, however. Lanska explains, “Most converters are still running the majority of their anilox rolls from 360-800 LPI. With new plate technologies emerging, we are seeing a migration of more and more process rolls into the 700-1000 LPI range. Generally, the line count stratosphere is reserved for the few intrepid companies endeavoring to push the envelope and set new standards of process print quality.”
According to Mikolajczyk, “Ninety-five percent of narrow web rolls ordered at this time are below 1200 line screen although we are receiving more requests for these line screens at this time.”
Luman agrees that higher line counts are becoming increasingly popular. He says, “Today 1200s and higher are more common than a few years ago. As the plate, ink technology and press technology (higher speeds, stability, etc.) evolve, the higher anilox screen counts will be required to produce high-end results.”
Others see the trend already occurring. John Batistatos says, “1200 line count is very prevalent. We continue to see more and more printers going in that direction. This is being driven by higher line screen plates.” Huey agrees and says the majority of narrow web printers use 1200 line count and above.
In addition to line count requests, converters also ask anilox manufacturers for other specifications. Batistatos says, “They have been asking for their anilox rolls to last longer with less plugging. They are also asking for higher opacity levels when printing white and higher ink density for all their colors.”
According to Lanska, converters want quality, consistency and predictable print results from their anilox rolls. He says, “Converters want to dazzle customers with new print effects that can be used to help promote the products. Achieving bright bold color, heavy opacity on background white, application of conductive inks or inks with embedded particles for unique, covert product identification and counterfeit protection, and even dimensional varnish effects are just a few of the unique situations where anilox cell architecture plays a role.”
Luman says, “Most commonly, converters are looking for one roll to serve multiple functions: print process, combo and solids.”
Using any piece of equipment comes with difficulties and anilox rolls are no exception. Mikolajczyk says, “One of the largest hurdles we see are when customers try to use the wrong type of engraving to try and print a job rather than get the right engraving for the specific job application. The proper approach is to find the right roll that works. It is not always the case that the high end roll is what the print situation will call for.”
A visual representation of Praxair’s REV engraving
Lanska has this advice for converters: “Clean rolls promptly, thoroughly and carefully. Understand the proper use and limitations of your particular cleaning system. Rinse the rolls with warm water after cleaning and dry with a clean rag. Keep rolls covered to protect them in storage.”
Batistatos says, “Regular cleaning of rolls with hand cleaners reduces the need to use harsher methods of cleaning that may cause damage to the engraving.”
Mikolajczyk agrees. “The trick is continued cleaning to prevent the rolls from getting dirty to the point where only the most aggressive cleaning techniques will work. Pamarco’s CARE program has been designed with this concept in mind, utilizing chemical cleaners in a regimen of daily wash-up, weekly deep clean and quarterly maintenance cycles to keep anilox rolls in peak condition,” he says.
Harper GraphicSolutions’ Luman says, “There are many effective cleaners on the market and many off-press cleaning systems. We are constantly making modifications to our cleaners to enhance the effectiveness.”
In addition to cleaning, Harrison cites lightweight technology as an option for better handling and care. She says that lighter anilox rollers make clean-up and storage easier for the operator and can help eliminate damages.
Predicting how long an anilox roll will last is difficult because roll care and maintenance play such a pivotal role in an anilox roll’s life. Most involved with the technology talk about a range for life expectancy. Mikolajczyk says anilox rolls typically last two and a half to five years.
Lanska has a similar timetable. “Generally, we expect most rolls to last from two to five years — more when run against a rubber nip roll. High line count rolls run at high speed against metal blades may not make it that long. The biggest key is preventing damage since that is the primary cause for roll resurfacing.”
Batistatos has a higher estimate. “With proper care and handling, our customers have experienced life cycles in excess of 10 years.”
CTS’ Harrison explains why putting a timeframe on anilox life is difficult: “In a perfect world, with a 40-hour work week, normal use, regular cleaning, we’ve seen rollers as old as 10 years. Others, we’ve seen wear in less than a year. It depends on the application the printer is running.”
After continued use, anilox rolls will not work as well as when they were new. Harrison explains, “The operator will notice a much shinier coating on the surface of the anilox roller, comparable to a dull reflection as well as surface spotting.”
Huey says, “When rolls wear out, the cell walls become wider, the surface typically becomes shiny and the colors print lighter. When this occurs, an anilox can be remanufactured by stripping old ceramic, applying new ceramic and engraving to customer-specified line screen and volume.”
Although it’s possible to remanufacture anilox rolls, sometimes the most cost effective solution is to purchase a new one. Mikolajczyk says, “When they wear out they can be reconditioned. The decision for new/rework often depends on freight and other factors such as, does the roll base itself need considerable rework to make it a cost effective exercise. Often in the case of narrow web rolls it is most cost effective to save on the freight and rework to buy new.”
The cost of an anilox roll is difficult to pinpoint because several factors determine price. Lanska says, “Anilox cost is a function of surface area, line count and complexity of the base construction. Narrow web rolls range from a few hundred dollars to a few thousand each.”
Harrison says, “For the most part, the prices can begin as low as $500 and continue to climb, with averages for narrow web running between $800 and $1,800.”
Anilox sleeve technology is relatively new in the narrow web industry. The sleeves perform similarly, if not identically, to their anilox roll counterparts. Huey says, “Lifespan is similar and based on care. I cannot commit to or rubber stamp this, but the ‘typical’ anilox sleeve can be remanufactured successfully two to three times. Therefore if the typical engraving lasts two to three years and a sleeve can be remanufactured two to three times, the lifespan is between four and nine years.”
Sleeve technology is not extremely common, but it is increasing. Lanska says, “Anilox sleeves, a technology that has proven itself in wide web, is making a transition into the narrow web arena. The improved registration, quicker roll changes and reduced waste offered by servo technology provide justification for adapting this technology to the narrow web sector. There is growing interest in anilox sleeve technology for the narrow web segment. The costs, however, must be weighed against the benefits.”
Batistatos agrees that interest in sleeves is increasing. Praxair manufactures anilox sleeves and has seen more inquiries for the technology. He says, “We have provided sleeves to several top end printers this year.”
Luman points out, “It is more common than three years ago, but a lot of the advantages that exist in the mid to wide web market don’t exist with narrow web sleeves.”
Sleeve advantages and disadvantages
As with any equipment option, there are pros and cons that converters need to weigh before deciding whether or not to use anilox sleeves. Positives associated with sleeves that Mikolajczyk cites are lower freight costs and lighter weight. He also says sleeves are easier and safer to handle and are reprocessable. Batistatos adds that sleeves reduce setup times for the printer.
Lanska sees many pros in using sleeves. “The biggest advantage with sleeves is the ability of the sleeved presses to hold incredibly tight register even as the machine is ramping up to or down from the desired press speed. Sleeves are much lighter weight than conventional steel anilox rolls. Used in conjunction with cantilevered design presses, the process of changing out sleeves takes a fraction of the time it typically takes to change out conventional anilox rolls. Tooling costs are reduced because you do not need a separate set of gears and bearings for each anilox. Storage systems can be manufactured from lighter weight materials because they have to support less weight.”
Several disadvantages exist as well. Huey says, “Sleeves are less rigid than rolls with journals, which takes us back to care of the rolls. They also cannot be remanufactured as many times as rolls with journals.”
An imaging photo from CTS. A customer requested that the engraving specifications appear on the face of the anilox roller so LPI can be determined without removing the roller from the press.
Lanska says, “Cost is a major consideration with anilox sleeves. Ready availability of replacement sleeves could certainly be another, especially if one became damaged. Sleeves are well suited for situations where frequent installation and removal is the norm because that is where the time and waste savings can rapidly add up. Because of their high cost, sleeves should not be used with catalytic inks. If catalytic ink ended up drying on the roll, it would have to be resurfaced.”
As Lanska points out, anilox sleeves are more expensive than rolls, generally two to five times as costly as conventional steel cores of the same dimensions.
Huey explains, “The cost of the ceramic and engraving are the same whether it is a sleeve or an anilox with a journal. An anilox sleeve can cost two to three times as much as a new anilox base.”
Although the sleeves are more expensive, in the end, converters may find them to be the best option. Mikolajczyk says that sleeve prices are higher, but when maintained properly, sleeves can be more cost effective since they are lighter weight and have lower freight costs.