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FLEXO Magazine : January 2014
FURTHER OPTIMIZATION With the optimum print parameters established, the focus then turns to print benchmarking, characterization and validation. More to the point, every other process downstream must be calibrated to rectify the gamut capability demonstrat- ed by the particular set of print conditions (color profiling), and the process must be repeated in order to establish realis- tic targets and tolerances (statistical process control). SETTING A BENCHMARK When the optimal ink, anilox, plate and mounting tape combination has been determined, the initial step of the profil- ing process typically involves a “benchmark” printrun that aids in determining print curve compensation to be applied to the selected profile target. The “fingerprint” or “character- ization” pressrun then captures gamut capability achievable from a given print condition. Results achieved from this press characterization also aid in defining ongoing “run targets” for press operators as it relates to solid ink density and dot area measurements ob- tained from “control patches” placed on production runs. Through the application of “standardized” targets and software programs available today, building color profiles for application in the prepress and proofing stages has evolved into a fairly automated and uncomplicated process. What re- mains critical, however, is conducting multiple readings from the print results in order to establish a predictable average. As Mark Samworth so aptly states in some of his presenta- tions involving the application of process color print in flexo, the two facts of establishing color profiles are: • If your production run matches your profile run, the pro- file will produce accurate color • Your production run will not match your profile run IS IT WORTH IT? While these facts may prompt the question of “Why is it even worth it?” everything relates to the given truth that the number of variables involved in the flexo print reproduc- tion process leads to successful process control measures, including the “smoothing” or “synchronizing” of color profiles, in order to obtain the most predictable results. An equally important component—one that is often overlooked—is that monitors and proofing devices are religiously calibrated to specification. Process control in the platemaking area relates largely to ensuring consistency in the finished product. This can include both instrumental and visual verification and includes param- eters related to plate height, floor thickness, “overwash” spec- ification, dot area measurement and surface tack. FIRST 4.1 provides a good general guideline for estab- lishing and maintaining photopolymer printing plate spec- ifications. With digital platemaking there also exist certain specifications related to maintaining accurate laser focus and intensity that vary by manufacturer. Not to be overlooked in the establishment of an ongoing process control program is the assurance of maintaining conformity in remaining process variables like substrates, sleeves, mounting tape, raw printing plate material, proof- ing stocks, etc. through COA from the manufacturer or internal veri- fication. APPRECIATING AUTOMATION Technology available today has enabled our industry to more accurately automate, quantify and control many of the key process components, such as: • Ink viscosity and pH • Impression and registration • Anilox cell depth and condition • Film surface treatment and tension • Color variance throughout a run All of this has resulted in increased control and a vast reduction of process variables. With that being the case, why is it then that so many printers have experienced limited suc- cess printing to standards? Part of the reason could be that we tend to place too much emphasis and focus on the indi- vidual components of the process themselves (presses, inks, anilox, plates, proofs) as compared to viewing the individual components as an integrated whole and addressing process control from that angle. Expanding the color gamut with flexo has and will continue to lead to many dynamic opportunities for the flexo printer, particularly in the flexible packaging market segment. In the end, whichever path a particular printer may choose toward optimizing the achievable printed color gamut, the keys to success lie in the establishment of a stringent and achievable process control program at the outset, as well as aligning with the most qualified and dependable industry suppliers and partners in defining and implementing the process plan. n About the Author: Paul Lancelle is a member of the Techni- cal Solutions Group at All Printing Resources, Inc. He is a 37 year veteran of the printing industry, including more than 22 years in flexo prepress, plate and print technical applications. An active member of FTA, he has served as a past Forum chair, board member, supplier vice chair and FTA chairman of the board. He remains active on the awards and FIRST committees. Paul has spoken and conducted training on flexo technical topics on five continents. The combination of plate, sleeve and mounting material, referred to as the “plate package,” interacts to influence print quality and ongoing process control. (Photo credit: FIRST 4.1) www.flexography.org JANUARY 2014 FLEXO 57