The determination of using the standard screening angles when printing with 400-count anilox rolls and 100 line images via flexography

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Title: The determination of using the standard screening angles when printing with 400-count anilox rolls and 100 line images via flexography
Author: Ahrens, John
Abstract: From the pioneering efforts of the early 1960 's, flexography has shown steady progress in the development of four color process printing. However, the ability to consistently produce it is limited to an elite group. The vast majority of companies have yet to competitively enter this demanding area of printing. For these companies the time, expense, and expertise required to conduct an indepth study is a major deterrent. Outside information must be made available to aid the companies. The FTA and its members have greatly contributed by publishing an array of information; although, some basic questions have yet to be answered. Of these questions, proper screen angling for the elimination of moire' patterns is an open topic. The occurrence of moire' patterns in flexography is the result of the 45 degree cellular pattern of the anilox combined with the 45 degree tonal pattern of the plate image. To eliminate the moire', most f lexographers "offset" the four screening angles by a predetermined amount. For example, instead of screening at 45, 75, 90, and 105 degrees, a company may screen at 52, 82, 97, and 112 degrees. The recommendation of offsetting the four screening angles was given in 1968 and was based on tests conducted with 200 and 220 anilox rolls. Since that time, Parmarco, Inc., has introduced finer count anilox rolls under the trade name of "Tone and Process." It is the belief of Mr. Douglas E. Tuttle, Vice President, Marketing, Parmarco, Inc., that when using Tone and Process anilox rolls, the following is true: [1] A moire' will not be produced with the 45 degree plate image . [2] The standard angles can be used by f lexographers when printing four color process work via flexography. [3] A Tone and Process anilox roll will produce a moire1 once it is sufficiently worn. The thesis hypothesis addresses the topic of screen angling when printing four color process work with 4 00 TPB anilox rolls and 100 line plate images. The methodology focuses on three separate tests. Tests one and two investigate the suggestion that the standard angles can be used without a moire' appearing in the final print. Test three considers the suggestion that a moire1 will be produced with the 45 degree printer once the 400 TPB anilox is sufficiently worn. The results of tests one and two support the hypothesis that the standard angles of 45, 75, 90, and 105 degrees can be used by the flexographer when printing with 4 00 TPB anilox rolls and 100 line plate images. It is also concluded that a 400 TPB anilox will produce a moire' once it is sufficiently worn.
Record URI: http://hdl.handle.net/1850/8736
Date: 1980-06

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