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FLEXO Magazine : November 2009
30 FLEXO NOVEMBER 2009 www.flexography.org The method of ink transfer is the essential difference between litho-offset, rotogravure and flexographic printing. The anilox roll and the raised image flexible printing plate are unique to flexography. And that's where this story begins. The advances in technology enabling flexo to compete effectively with offset and rotogravure's quality really began as a result of the introduction of the laser engraved ceramic anilox surface in the 1980s. For the first time, it was possible to increase the surface line count beyond 360 cells per inch, which, until then, was the maximum an engraving tool could knurl onto a mechanically engraved anilox surface. The process advantage resulting from increasing the num- ber of cells on an anilox surface is that it became possible to reduce the thickness of the surface film of ink and in doing so reduce the primary source of image growth or dot gain. Fine print screens or process print were not possible when running an anilox at 360lpi. Even though the advantage of improved ink transfer achiev- able from higher line count anilox surfaces were obvious early on, it wasn't immediately possible to jump from 360 to 1,000lpi. Instead, it took years of development work to modify the other key process elements. Photopolymer plates were introduced in this period, mounting tapes were improved, new types of ink metering systems including chambers were developed, and inks changed dramatically so they could all function together. Each process element had to adjust and readjust to the new reality of the other. In the beginning of flexo's process improvement journey, development centered on gaining better control of the ink transfer process. As the basic flexo transfer process evolved, press manufacturers were required and allowed to develop press capabilities that weren't necessary or possible before. The Golden Age of Flexo Are Gains Still to be Realized? Maybe... Maybe Not! By Paul Sharkey • Most printers still face basic challenges of premature anilox wear. • Higher quality doctor blades lead to long-term qual- ity results. • There is always room for best practices, regardless of technological advancements. While flexographic printing technology has changed greatly since the 1970s, good habits of quality control have not. Photo courtesy Mark Andy Inc. TECHNOLOGIES & TECHNIQUES
Sustainable Fall 2009