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FLEXO Magazine : September 2009
60 FLEXO SEPTEMBER 2009 www.flexography.org TECHNOLOGIES & TECHNIQUES It's now time to print the production job---how do I control the process and get consistent color? Opportunity In Hand: Now It's Time to Deliver Consistency The Case for Process Control and Process Improvement By Bill Pope and Michelle Beuscher Art courtesy EskoArtwork. Authors' Note: This is the third in a series of three articles cov- ering an updated methodology for printing as detailed in the Print Section of FIRST (Flexographic Image Reproduction Specifications and Tolerances) 4.0. This CGATS (Committees for Graphic Arts Technology Standards)-endorsed approach is intended to help the printer become more successful through optimization, fingerprint- ing, characterization, process control, and process improvement. To read Part I, see FLEXO July page 18 and Part II, see FLEXO August page 30. Last we checked in with our printing department man- ager, he had successfully fingerprinted and characterized his printing process and determined process capability indices repre- sentative of the process. Now it's time to print the first production run, hold color as consistently as possible, and meet the agreed upon release specifications. This is accomplished through the third and final aspect of the methodology: process control. Further, process improvement activities will help meet customer expectations while contribut- ing to internal quality and productivity improvements. USING THE FINGERPRINTING Recall from last month's article that part of what comes from the fingerprinting activity is information and data repre- senting how the press was set up and run. These serve as the bench- mark for future runs. Consider this "placing the stake in the ground"--- the condition that our printing department manager is trying to get the process to achieve again. There are two main categories that the information falls into: press set- up information and mechanical and process control parameters. PRESS SET-UP INFORMATION Press set-up information comes from accurate documentation and use of a good press oper- ating data sheet. There, all the information necessary to set the job back up again should be documented---everything from ink sequence, ink batch information, anilox selection, stickyback type, doctor blade information, substrate infor- mation, and every other component or material used in the pressrun. Again, the key is to know exactly how the press was set up. Now, it's not likely that more of the same batches of materials (inks, stickyback, substrate, etc.) will be available on future runs, but the goal is to only allow into the process materials that are consistent with the ones used during the fingerprinting pressrun. Suppliers should freely be providing key attribute information about their product on a Certificate of Analysis (CoA). The CoA should accompany every batch of product and only product that conforms to agreed-upon specifications should be allowed into the plant. MECHANICAL CONTROL PARAMETERS While the press was running during the fingerprint, there were mechanical press settings and material attribute parameters that were set and monitored. Mechanical press settings could include things like press speed, tension set- tings, dryer or lamp set points, and others. Material attribute • The goal is to only allow into the process materials that are consistent with the ones used during the ﬁngerprinting pressrun. • Knowing how the press was set up and run and how various materials “behaved” during the run is critical in deﬁning the same conditions for future production runs. • The data generated from the ﬁngerprinting pressrun should be used not only for setting up the process control plan, but also for identifying process improve- ment opportunities. • By following the steps of the methodology outlined in FIRST 4.0, printers can effectively optimize, ﬁnger- print, characterize, and control and improve the printing process