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FLEXO Magazine : June 2013
elimination of potential moiré patterns coming from the plate line screen. Ink systems at this time were mostly solvent and the plates were rubber. CERAMIC COATINGS Further development came in the 1960s and 1970s with the introduction of a random ceramic roll. This type of roll is produced by blending titanium dioxide and aluminum powders, which are sprayed at high temperature onto a roll. These melted particles solidify on the roll in a random pattern of holes and an irregular surface of heights. While this was an improvement in durability it did not compare to the quality of the engraved chrome plated rolls. Next in the evolution was the micro-ce- ramic engraved rolls. In 1973, Pamarco incorporated, applied, and was granted a patent for an anilox roll that was en- graved and spray coated with ceramic 0.0025-0 .003-in. thick. The size of the ceramic particles had to be controlled or the engraved cells would fill and not transfer ink. The limitation was also in line screen---220 cells per inch. LASER ENGRAVINGS Pamarco's Europe division had been laser cutting continuous rubber rolls for the wallpaper industry. An idea was brought forward to manufacture a more durable anilox roll. Leveraging a rela- tionship the company had with Union Carbide (now Praxair) which special- ized in coatings; they jointly worked toward laser engraving ceramic rolls. Union Carbide brought this technol- ogy to the United States and Pamarco became its sales agent for two-to-three years. The contract ended and Pamarco purchased its first laser and installed it in Roselle, NJ in 1984. The need for a controlled ink transfer became more important as the other parts of the flexographic printing system developed. Advances in ink chemistry and plates demanded an anilox roll with improved ink release and uniform transfer to the plate. In the early 1980s, CO2 lasers had 400 to 800 watts of energy and produced cells with a single hit. Screens were limited to less than 500 lpi with limited volume capacity. Later in the 1980s, CO2 lasers were developed with 1,000 watts of power and a split beam technology that in- creased the volume range. The Ablative YAG Laser of the 1990s had very little thermal energy but made well formed cells with little recast. Line screens of 900--1,000 were possible and were suc- cessful to attain high levels of graphics. The drawback was the lack of re-cast ceramic that made these engravings prone to wear and scoring, thus cutting the lifespan. As the power of the lasers continued to climb, the ability to produce higher line screens followed. Through the 1990s the Ablative multi hit YAG and CO2 lasers continued to improve as new optical and electronics were developed. These allowed for improved cell struc- ture and volume ranges. At this time, photopolymer plates were being introduced to the market, www.flexography.org JUNE 2013 FLEXO 63 "Polymag® Tek's Traversing Water Wash Systems are the only contact web cleaning solutions on the market today, that can cost effectively keep up with the dirt, dust and contamination challenges that are presented by utilizing today's 100% recycled CRB and URB board stocks. These systems will be a key component in your company's sustainability efforts. Call for a quotation today. Polymag® Tek, where BLUE is the new GREEN! Proudly designed, fabricated and assembled in the USA!" Polymag Tek, Inc 215 Tremont Street, Rochester, NY 14608 1/800-787-0830 Tel: 585/235-8390 www.polymagtek.com