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FLEXO Magazine : October 2009
26 FLEXO OCTOBER 2009 www.flexography.org A radiometer (or light meter) measures bulb output. Calibrate in terms of energy, not time. All UV lamps do lose some intensity over time, but it is a gradual loss. 16 0 4 8 12 20 24 28 Back Exposure Step Test A back exposure step test. Photo courtesy MacDermid Printing Solutions. Platemaking Calibration 4.0 FIRST Recommends A New Way of Looking at Plate Imaging and Measurement By Tom Cassano What's changed in the world of plates and platemak- ing since the release of FIRST 4.0? In order to answer this question properly it was necessary to revisit the Prepress Sections of the Premier, Second, and Third Editions of FIRST (Flexographic Image Reproduction Specifications and Tolerances), where the Printing Plate sub-sections are lo- cated. With respect to actual specifications and tolerances for printing plates, they have changed little since FIRST debuted in 1997. The minimum dot specification has gone from 2 per- cent to 1 percent for certain plate types, and caliper variation tolerances haven't changed. Surprisingly, relief specifications for any plate type were not included until the Third Edition of FIRST debuted in 2003, and those remain unchanged. This is all due to digital imaging technology, which created a radi- cally different dot profile and structure that requires less relief to remain stable during the printing process. While different photopolymers have been developed over the years to address certain needs and image reproduction challenges inherent in the flexo printing process, there hasn't been a major transformation in the technology since the Premier Edition. Did simply changing from a 2 percent dot to a 1 percent dot, imaged on a---technologically speaking--- stable" pho- topolymer platform make us, as an industry, better printers? The correct answer is no." What made us better printers is FIRST. Here is where things are significantly different. A NEW LANGUAGE FIRST 4.0 devotes much more verbiage, along with chart and graph templates, for gathering, understanding, mea- suring, and utilizing data for process control than in prior editions. It is in this context, specific to photopolymer printing plates, that the remainder of this article will focus. Printing plate measurement and control initially appears in the Second Edition in Section 16.9, and again in the Third Edition in Section 16.10 where six specific plate attributes and the tools to measure them are detailed. Table 16.10 from FIRST Third Edition. Printing Plate Measurement & Control Properties to Measure Measurement Device/Tool Durometer Shore A Gauge only for material < 0.250" (6.4mm) Total Caliper Plate Micrometer Plate Relief Plate Micrometer Minimum Dot Exposure Flexo Plate Analyzer Maximum Dot Exposure Flexo Plate Analyzer (maximum dot exposure not yet available) Line Width Microscope TECHNOLOGIES & TECHNIQUES
Sustainable Fall 2009