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FLEXO Magazine : June 2013
Technologies & Techniques HD Flexo Blades High Demand / High Definition By Paul sharkey In the past 40 years, no print method has advanced more than flexography. Compared to its primary rivals of offset and rotogravure, 1970s flexo was crude—and so were the results. Its primary advantage was price. In fact, like me, you may recall that some of the award-winning frozen food packaging at a 1970s FTA Forum was better viewed from a distance, so the process printed image would gain resolution. Beginning in the early 1980s, all areas of flexo became much better at printing solids and line work. Still, printers struggled with screens and process. Today, flexo successfully competes with rotogravure and offset in all market segments and does so based on quality at a competitive price. Success did not happen overnight. Instead, a lot of changes have taken place to the important ink management and ink transfer variables. NEW HD WORLD • In the new environment of HD Flexo, an ideal doctor blade must: • Engage a 1,000 cpi anilox surface, without damaging it • Operate at press speeds in excess of 1,000 fpm with less drag and less friction • Wear slower and more evenly with wear debris smaller and less threatening to thin walls of high line anilox • Perform over time in an extended gamut press environment • Meter a wider range of inks and coatings including UV, EB , metallic, florescent, pearlescent, thermal chromatic, as well as traditional solvent and water based ink • Resist flex under pressure The core purpose of a doctor blade in the flexo process is to remove excess ink from the anilox surface; to leave behind a perfectly smooth ink film for transfer to the image on the plate and to do this without damaging the anilox. The most precise and even metering takes place when the blade makes contact with the anilox in the reverse or sheering position at an angle between 30° - 35°. Modern day, high speed, central impression flexographic printing press. www.flexography.org June 2013 FLeXO 65