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FLEXO Magazine : June 2012
Technologies & Techniques A Better Impression Anilox is scientific By lee Kluttz Originally printed in January 2012. The anilox roll is widely known as the heart of the flexo- graphic press and Harper is very proud to announce continuing development of new anilox manufacturing technology. To someone on the outside looking in the past few years, the anilox roll may have seemed a dormant part of the flexographic industry. However, Harper has been very busy behind the scenes developing further advancements to take the manufacturing of anilox rolls to a new echelon. The technology of manufacturing an anilox today is not the same as compared with five years ago. Customers demand more consistency, repeatability and tighter tolerances. Every- thing is measured in the printing world including ink viscos- ity, dot gain, density, feeds, speeds, and waste. With that in mind, Harper has taken the same systematic approach to the manufacturing of anilox rolls. The company has made major investments and committed a substantial amount of time and focus in order to scientifi- cally measure every process of manufacturing an anilox roll. A major part of investments have come in the form of new technology, equipment, software development and instrument purchases to scientifically measure processes in a constant effort to maintain consistency. In the ceramic coatings process, Echoplasma, the compa- ny has purchased a large number of state-of the-art thermal spray plasma systems. Some of which are replacements as part of the continuous improvement program and others are due to increased customer demands. Touch screen thermal spray units will be established within the next year. LONGEVITY ESSENTIAL The hardness of the company ’s ceramic coating aver- ages 1,200 Vickers and is operated in a range between 1,100 to1,300. Some may ask why this is important and, from extensive experience, Harper has learned ceramic hardness above 1,300 Vickers changes the mechanical property and the ceramic becomes too hard and consequently, brittle. This could cause the coating to crack under pressures normally associated during regular press operation. By keeping the hardness of the ceramic coating within this range, the com- pany is able to provide the customer with the hardest ceramic possible to ensure longevity, while at the same time allowing it to remain durable. Maintaining a minimal amount of porosity is just as im- portant as maintaining the correct hardness. Our porosity averages .5 percent with an upper limit of 1 percent. Keeping porosity to such a low level allows Harper to maintain consis- tency when engraving the line screen as well as to ensure a uniform volume across the roll face. The company also has one of the first employees in the flexographic industry to be a certified CTSO thermal spray specialist to help maintain these standards. For example, when engraving a 1,200-line anilox with 2.0 BCM, if you have porosity (coating voids) that measures 25-30 microns across it becomes impossible to hold a consistent cell shape or volume because the opening of a 1,200 lpi cell is only 19 microns. It will be impossible to create the cell wall structure necessary to prevent the low percent- age dot from being overloaded with too much ink. As press speeds and line counts increase, so has the importance of the surface finishes of our rolls prior to laser engraving. With superfinishing SOP, every anilox surface is measured using a non-contact surface finish instrument and the Roughness Average (RA) is recorded. RA measuring gauges are used to measure roughness after polishing and before laser. This is vital because roughness plays a criti- cal role in determining how a real object will interact with its environment. Rough surfaces usually wear more quickly and have higher friction coefficients than smooth surfaces. Rough- ness is often a good predictor of a mechanical component’s performance and longevity since irregularities in its surface may form cracks or corrosion. To put this in perspective, ceramic imaged cylinders are not possible because ceramic by nature has too much porosity. SMOOTH SURFACE One way in which Harper controls consistency in the laser engraving machines is by giving operators the best possible TECHNOLOGY TO WATCH Harper Anilox • Introduction Date: Currently Available • Benefits: Presses are running at continually increasing speeds • Impact: Anilox technology is forever changing • Watch for: Stronger, harder, more durable anilox • 2012 Exhibitions: INFO*FLEX, Labelexpo Americas 8 FLeXO june 2012 www.flexography.org