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FLEXO Magazine : June 2014
New Polymer Doctor Blades Can Replace Steel More Durable, Safer, Longer Life Kevin McLaughlin Y es, steel doctor blades used to be the only option to produce high end graphics. And yes, a printer had to deal with shorter blade life, anilox scoring, pressroom inju- ries and other limitations of the material. Not any- more. Today’s next generation polymer materials and advanced MicroTip engineering have at last produced a doctor blade with the metering quality of steel but with the safety and blade life benefits of traditional plastic. This blade can replace steel in a full range of flexo printing applications from solids and lines, to reverses and fine print, to screens and process work. STEEL VS. TRADITIONAL PLASTIC Until now, steel has been widely accepted as the only blade that can produce high end graphics. Due to its thinness and stiffness it was considered the only blade material that could achieve a fine point of contact sufficient to execute a clean wipe on a high linescreen anilox roll. Steel has many disadvantages, however, despite its superior me- tering ability. The blades abrade easily, causing them to wear quickly, and need to be replaced frequently. Operators run the risk of being cut when removing worn blades from the press and metal fragments can come loose and score anilox rolls. By comparison, the characteristics of traditional plastic doctor blade material require these blades to be thicker to provide the same rigidity. While they last significantly longer and are safer to handle than steel blades, their thickness prevents them from maintaining a fine contact area with the anilox. As they wear and their contact area with the anilox roll grows, they produce changes in tonal value and dot gain when metering high linescreen rolls. For this reason they have histori- cally been limited to jobs with low to modest graphics requirements. NEXT GENERATION POLYMER Today, specially formulated polymer doctor blades offer the best of both steel and plastic. Unlike traditional plastic, the stiffness of the next generation material, together with a precisely engineered edge, allows the blade to achieve and maintain a fine contact area with the anilox roll. The blades deliver effective metering on linescreens up to 2,000 lpi and can be used to produce graphics of the highest quality. 80 FLEXO | JUNE 2014 TECHNOLOGY & TECHNIQUES Anilox Roll, Doctor Blade, Ink Selection Guide