Harper Anilox Rollers: Plate Dot Versus Anilox Cell Models

Anilox Scoring Prevention Guide (continued)
III. Primary Cause Prevention Checklist: Never over pressure doctor blades to get more color Keep chamber and blades aligned. Check vertical and horizontal alignment at least once a month. Use a piece of blade material as a feeler gauge. Bring the chamber in while checking the upper and lower blade. They should contact the anilox at the same time. Clean the brackets that hold the blade so the blade does not ripple when tightened down. Tighten clamps from the center out using even pressure. Do not continue to use blades that have exceeded their maximum wear. Develop a regular schedule to change blades. Overused blades put large pieces of metal into the ink from deflection and irregular pressure. They also create danger of the chamber ends contacting the anilox. When new blades are installed, reset the chamber pressure. Many people simply swing the chamber back into position without readjustment. This causes over pressure on the blade since the chamber is still adjusted for a worn blade. Purchase anilox rolls within proper depth-to-opening ratio for a smoother surface. Never rotate a dry anilox roll against the doctor blade. Do not set chamber to stop leaking. Set pressure to where anilox stops flooding. If seals leak, then correct seals. Educate all employees involved in the printing operation regarding the issues above. IV. Secondary Causes of Score Lines Secondary causes of score lines occur in cases where blade pressure setting is under control. When scoring suddenly becomes a problem in your operation or on a certain press, there is a pretty good chance that one of these issues is damaging your anilox. Following is a list of these secondary scoring culprits: Inferior blade material (Figures 9 & 10) Ceramic chips from damaged roll ends (Figure 11) Blade overhang (Figure 12) Small dried ink chunks that contain metal particles (Figure 13) Plastic or composite blades with embedded particles (Figure 14) Press parts rubbing on the roll, such as blade chambers or splash guards These secondary causes will continue to contribute to the damage of your anilox if prevention measures are not implemented and enforced. Viewing the Secondary Causes
Inferior Blade Material (Fig. 9) As the blade wears, ‘cold flow’ steel curls back and builds up on the edge of the blade away from the anilox. These slivers break away or hang on the edge and can cause scoring. This condition is similar to the slivers produced from over pressure of the blade.	Fig. 9
Low Quality Blade Material (Fig. 10) Shown at right is another example of low quality blade material that contains impurities in the steel. This breaks away in pieces, rather than being honed off into micro-slivers of metal fibers. Improperly engraved rolls may have a rough surface that causes the blade to wear quickly releasing chunks of metal particles into the system. This condition is aggravated when blades are used too long in the press.	Fig. 10
Ceramic Chips from Damaged Roll Ends (Fig. 11) Bumping anilox ends against press frames, roll racks, or other items, causes ceramic to chip off the edges (or the end of the roll face). Once started, chipping continues to put large damaging ceramic particles in the ink. Also, when the doctor blade runs against this rough surface, it wears severly and puts large chunks of metal into the ink. The chipped roll shown in Figure 11 occurred from failure to change a worn out blade. Rather, the crew kept adjusting the chamber as the blade wore. Eventually, with the blade long past its useful life, the chamber ends contacted the anilox and gouged the ends of the roll face.	Fig. 11
Blade Overhang (Fig. 12) As shown in the photo at right, overhanging the blade too far past the end of the anilox causes pressure on the blade wearing a deep ‘vee’. The greater the overhang and the longer the use of the blade, the greater the pressure. This is a common cause of large particles. Try to keep the ends of the blade as flush with the end of the roll as possible. Changing blades regularly minimizes this condition.	Fig. 12
Small Dried Ink Chunks that Contain Metal Particles (Fig. 13) Dried ink particles probably are not causing score lines. However, when the dried ink pieces carry metal, they are a vehicle for destruction.	Fig. 13
Plastic Blade with Embedded Metal Particle (Fig. 14) Figure 14 shows a plastic blade with a metal particle embedded in it. Plastic or composite blades do not doctor as cleanly as steel. They are, however, safer. Printers may still experience scoring with plastic blades. Metal is introduced through equipment wear or corrosion, water lines, parts rubbing on rolls, ink drums, or ink mixing propellers. If we use plastic and steel blades in combination, the chunks from the steel blade may embed in the plastic. Keep in mind that non steel blades have reduced scoring in some instances while increasing it in others.	Fig. 14
V. Secondary Cause Prevention Checklist: Clean the press to keep dried ink out of the system. Use the strongest, largest magnet possible to remove metal. The best location seems to be in a canister on the pump in feed line. If you do not pump your ink, find a place in the fountain. Keep the magnets clean! Stainless steel blades contain enough magnetically attracted material. Do not use steel wool to scrub parts. Check blade chamber or holders for corrosion. Flush the ink through the chamber or fountain as fast as possible to get the metal away from the anilox and to the magnet. Repair chipped roll ends. Avoid overhanging blades as much as possible. Strain the ink returns. Make sure equipment is in good repair. Also check that mixers do not rub against drums or ink kits and pumps do not have wearing shafts. Use good quality blade material. Plastic blades may allow metal to embed in them. Educate all employees involved in the printing operation regarding the issues above. Suggested Plan of Action To determine whether a magnet will reduce scoring, the following test method has proven helpful: Select a roll for evaluation. (A new roll with no scoring is best.) Install a canister filter and fit it with a strong, large magnet on the infeed line of a pump. The strong magnet filter and selected anilox become inseparable. That is, when the anilox is in use, the magnet is on the ink supply line. Review the issues concerning blade pressure, overhanging blade ends, etc. Explain the reason and goal of the test with supervisors and press crews. Observe the roll for scoring over a designated period while inspecting the kinds of metal pieces collected on the magnet. In numerous cases, this method has proven itself as a precaution against metal and reduces or eliminates scoring. Of course, if you do not pump your ink, a strong magnet in the fountain is an alternative. V. Precision Tools Require Proper Care, Consider Precision Instrument Covers For Your Rolls One of the simplest and most cost-effective ways to protect your anilox is roll covers. Roll covers send a very strong message to your print crews: "Professional covers show the value of your anilox investment and encourage careful anilox care and handling." Harper now has custom-made, professional roll covers available. Contact your sales representative for details. Realize that anilox rolls are precision tools requiring proper care. Modern rolls print far better than the rolls of just a few years ago. However, along with the superior printing characteristics comes the obligation to take a few simple precautions to protect them. These precautions soon become routine and will make life easier in the long run.
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