The anilox roll is often referred to as the “heart” of the flexo printing process. Much like our human hearts, the anilox roll’s function lies in distribution. While our human hearts distribute blood, maintaining the health and functionality of our limbs, muscles and other vital organs, flexo’s “heart” distributes ink to the process’s other vital components – the printing plates.
As the anilox roll goes, so goes the flexo process. So much like us humans need to take care of our hearts – eating right, not smoking, exercising – it’s paramount for flexo label converters to maintain their anilox rolls. Should an anilox roll become compromised with dirt or damage, so does the print quality. With that said, taking the time to follow proper maintenance procedures is of the utmost importance.
Handle with Care
Regardless of cell structure or how an anilox roll is constructed or engraved, they require a thorough care and maintenance program, as a damaged anilox roll can be detrimental to a print run, costing a converter wasted ink, labelstock, labor and time.
“One of the most common ways an anilox roll gets damaged is simple poor handling, resulting in the ends or surface of the rolls getting damaged,” says Alex James, director of Harper GraphicSolutions. “If the damage is on the surface and in the print areas, a defect in color will be visible.”
Jean Jackson, sales manager NA Printing for Praxair Surface Technologies, explains how mechanical damage from mishandling anilox rolls can be avoided by using protective measures. “Anilox rolls become damaged by hitting the edge or roll face during installation or removal from the press without the face or edged protected. Thin Roll Covers and radiused roll edges will help with the chips and dents that occur with impact to the roll face. Some of this damage can be from softer aluminum press components that potentially can be removed with caustic cleaners. These dents or nicks in the roll face can print dark or light spots in the image and the edge chips can sling ink in the press causing housekeeping issues,” she says.
To prevent damage, Praxair recommends training with the press and maintenance teams, and “utilizing covers when possible for installation in the press and always when in storage off of the press, as we supply covers with all new narrow web rolls,” Jackson says. “We also suggest sturdy racks that are protected from fork truck and cart contact along with covers while on the rack.”
Bobby Furr, flexo services manager for Max Daetwyler Corporation, says anilox rolls should be protected with roll covers at all times. “When installed in the press, the covers should remain on and then taken off the anilox roller when the roller is secured and into place,” he says, adding that when not in use anilox rolls should be stored in a roll storage type of system. “This will allow for the proper storage and easy identification of the anilox rolls.”
Harper Corporation offers a number of products designed for both anilox storage and protection. Harper’s Echo-Pro is a padded roll cover and the Echo-Cover is a non-padded roll cover. For anilox sleeves, Harper offers Shield-Pro covers. “These products will keep your anilox inventory protected and lasting longer,” says James, adding, “Journaled anilox rolls should be stored by the journals on padded racks. Sleeve anilox rolls should be stored vertically on padded racks.”
While a dropped or knocked-around roll will cause physical damage, many times its ink contamination that can be the leading culprit pertaining to anilox damage.
“It is very important that inks be strained with cheese cloth or some type of mesh screen on a regular basis,” advises Daetwyler’s Bobby Furr. “Dried ink particles, used doctor blade steel particles and paper dust and such will circulate back to the inks and if not filtered or collected, can cause serious damage to the anilox roll,” he says. “When an anilox roll is damaged, it is permanent. What this means is the damaged area will show up in the print. If the anilox has a severe score line, that line will show up in the print. If the anilox has a deep scratch or gouge, that area will show up in the print. And once a line or scratch or anything of this nature shows up within the engraved area of the anilox roll, the anilox will have to be re-engraved and can cost thousands of dollars,” Furr says.
While Daetwyler offers an anilox storage system as well as well as anilox protective roll covers, the company also offers Daetwyler Magnets, products that prevent possible debris from steel doctor blades contaminating the inking system and causing damage that way. Furr explains, “These are Rare Earth magnets with pull rates from four to eight pounds. These magnets are specifically designed for inking systems to attract any magnetized debris within the system.”
Another form of protection can be found in anilox roll coatings. Praxair leverages its history as a coating supplier to metallurgically qualify and test all of its anilox coating and engravings. “As a supplier of ceramic powder and coating equipment along with delivering coating services to our customers in many highly demanding industries like aircraft engines and energy production, we have a consistent, hard chrome oxide coating with very low porosity, which delivers long life since we started in engraving rolls in 1983 in the US. We work with our technology team to insure the integrity of the full process and test new technologies,” Jackson says, adding, “We also work with our co-suppliers and customers to help optimize the process of ink, blades, aniloxes, cleaners and settings. This can greatly help the engraving life and deliver improved productivity on press.”
A damaged anilox roll can be down but not out. Available to converters are a variety of repair kits that can provide savings as an alternative to new rolls or engravings.
The first step in determining if a roll can be repaired is finding out how badly damaged it is. At Daetwyler’s manufacturing facility there’s intricate microscopy, allowing anilox experts the ability to look at damaged rollers and take microscopic pictures and images of the damage.
“Typically, a technical report with images of the damage will be presented to the customer with recommendations on how to solve the issue,” Furr says. “If an anilox roller is damaged within the engraved cell area, you cannot repair that area as it will fill in the cells should you attempt to repair it. An attempt to print with an area of no engraved cells (repaired printed cell area) will show up in the print and become rejected. If the anilox roller is damaged or chipped on the ends of the roller or outside of the designated printed area, it can be repaired.”
Daetwyler has developed and offers a Cylinder Repair Kit, which allows you to take the epoxy and fill in the dings or chips within the ceramic or chrome roller. “The epoxy will harden within 15 minutes and is permanent and will not come out making it an effective method for repair,” Furr says.
Jean Jackson notes that if there is an edge chip, Praxair has had some success extending the roll life by very carefully cleaning and filling the edge chip with metal epoxy. “The scratches should be evaluated as they might be material that is on the surface of the engraving and can be chemically removed from the cell walls,” she says. “The anilox supplier should work with you on the evaluation and cleaning materials to determine feasibility and impact on the ceramic and engraving.”
Harper offers a hardening compound called Chip Fix that addresses damage at the ends of rolls. “However, if the damage is on the surface, in the print areas, the anilox will need to be remanufactured,” James says.
Cleaning is Critical
A clean anilox roll is a crucial part of overall print process. The purpose of an anilox roll is to deliver a very specific volume of ink to the plate and then onto the web that travels through the press. If a roll is dirty and the cells are filled with excess dried inks and resins, then the wrong amount of ink will be delivered by the anilox.
“Delivering the wrong amount of ink by the anilox can distort the colors that are on the printed product. This is especially noticeable when the printed product is a process job,” says Joe Walczak, president of Sonic Solutions. “When one anilox is not delivering the correct amount of ink in a process job, the finished product’s colors can be quite distorted. If the poor quality is noticed by the press operator, then they must stop the press, and find out what the problem is. This all means wasted time and materials. The cost of the print job goes up, and profits go down. If the poor quality is not noticed then the printed product goes to their customer. They might then reject the order and require reprinting, or even worse – they go to a different printer.”
Sonic Solutions specializes in a type of cleaning called ultrasonics. With ultrasonics, the anilox roll rests on top of an ultrasonic tank and then rotates slowly to allow the roll to become clean. “The ultrasonic tank is filled with a cleaning solution, which is used for two purposes,” explains Walczak. “First, it is used to soften the dirt and debris within the cells of the anilox. The second purpose is for it to be used to transmit the ultrasonic waves to the roll, which have a drawing or vacuuming effect on the anilox. The ultrasonics then pulls all the dirt and debris off of the anilox. The beauty of ultrasonics is that it will go into each and every crevice of the ceramics on the anilox and vacuum the debris off.”
Ultrasonic cleaning works by causing the ultrasonic transducers that are bonded to the bottom of the tank to vibrate very quickly, causing positive and negative energy to form within the cleaning solution. Walczak says, “This then causes air pockets or bubbles to form within the solution and hence on the anilox roll. The air bubbles then collapse, creating a drawing effect. Think of a balloon that is filled with air. When you release the balloon, the air quickly escapes from the balloon – it’s the same with ultrasonics. The air bubble goes into the cells of the anilox and collapses – just real fast.”
Ultrasonic cleaning is a two step process. “We call it the 90/10 - Max 5 Rule,” Walczak says. “The first step is to start soaking the anilox roll, allowing the roll to rotate on top of the system. Here, you are allowing the solution to wet and soften any of the inks and dirt inside the cells. It’s a very important step that is 90% of the cleaning. The second step is to apply the ultrasonic power to the system to soften dirt and debris which is gently vacuumed out of and off the cells of the anilox – this is 10% of the process. You do not allow the ultrasonics to be on for more than 5 minutes each time, hence - 90/10 - Max 5.”
Sonic Solutions recently introduced its Phoenix line of upgraded equipment, featuring a number of enhancements that protect the anilox roll and the cleaning system. These include an external interchangeable power generator, higher frequency of ultrasonics with smaller bubbles that can get into the smaller cells of higher line count rolls, replaceable ultrasonic transducers, and low liquid level heater protection.
The proper time to clean an anilox roll is a question often asked of anilox cleaning suppliers. Bill Malm, regional sales manager for Flexo Wash, responds by saying having a routine cleaning schedule is good, better is cleaning after each job, but the best time to clean is immediately upon removal from the press. “In a perfect world, anilox rolls are cleaned immediately,” Malm says. “The majority of inks and coatings used in our industry are formulated to resist moisture, chemical, rub, scuff, etc. These are all tools and processes used to clean an anilox roll. The longer an ink or coating has been allowed to dry in the cells, the more difficult it becomes to clean.”
With regard to the cleaning process Flexo Wash uses, Malm says that while some consider it a chemical bath or shower, he likens it to “a touchless car wash, minus the pink foam.”
Flexo Wash uses water-based liquids that break down into the smallest molecular particles, thus allowing easy penetration into the smallest cells to loosen and dissolve the inks, coatings and adhesives. The Flexo Wash process starts with a wash cycle, where rotating chemistry is applied to the surface of the roll. Next, a drain cycle returns the remaining chemistry back to the wash tank for re-use. After a high pressure water rinse, the dry cycle’s compressed air removes water from the surface. “The complete cycle typically lasts between 15-20 minutes,” Malm says.
Flexo Wash works as a plug n’ play system – set the time, close the lid and push the button. Additional advantages, Malm adds, are in its inherent safety for the rolls, employees and the environment, but also its performance. He says, “Our technology is proven to deep clean cell counts of up to 2,800 cpi. Flexo Wash-cleaned anilox rolls and sleeves last longer because our technology does not wear down the cell walls, therefore maintaining as much of the original cell volume as achievable, and available cell volume is restored in just minutes. Also, the cleaning solution is captured and filtered for re-use again and again resulting in low operating costs.”
Today’s anilox cleaning challenges are not only different, they’re more difficult. Due to the higher cpi and smaller cells, anilox rolls are more fragile and susceptible to damage. “This will cause some traditional cleaners and processes to lose their effectiveness, Malm says. “Our process allows your operators to focus on changeovers and running the press instead of cleaning, which results in increased production and profitability.”