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FLEXO Magazine : November 2011
Selection Guide Anilox Rolls & Doctor Blades Which cell shape is right foryou? Asdiscussed,fortheapplicationofprocessandpantonecolors,the60°hexagonalcellshapeis preferredfortheultimatecontrolofthedesiredinkfilmforthehighestqualityprintatvolumes typicallyusedforprocessandcombinationwork. Atvolumesandinkfilmthicknessesforsolidsandcombinationstheuseofa30°hexagonalcell shapewithachannelwillallowinksofalltypesandcoatingstoflowunderneaththedoctor bladefacilitatingasmootherlaydownforimproveddensity,opacityandsolidcoverage. Resultswillvaryfrommarkettomarketdependingonalloftheelementsoftheprocess workingtogether.Beingaprocess,allelementsmustbeoptimizedfortheapplicationathand. Thecombinationofanilox,ink/coating,printingplate/tintscreen,mountingtape,doctor blade(s),andsubstratewillmeansuccessorfailure,progressorsetback. Withsomanycellpatternsandchannelsavailable,Iwouldencourageprintersandsuppliersto askquestions,investigateopportunitiesforresearchanddevelopmentandthenconducttheir owntesting. Abandedrollperhaps,whenappropriate. Rememberthatwhenachangeismadetoanelementoftheprocess,attentionmayneedtobe giventotheelementswithwhichitworks tooptimizeprintqualityandprocessefficiency. Fromlefttoright:40°Channel,ElongatedHex,SerpentineChannel,StraightChannel,Trihelical, 30°HexWithoutChannel,45°Quadshapedcellpatterns. structure and reflective density on the substrate. A study by the United States Environmental Protection Agency showed that a relatively modest temperature increase of 5-10C could lead to significant rise in ink and solvent/reducer costs. An array of options of differing com- plexity is available to control these vari- ables. At the most basic, a hand-held Zahn cup and a stopwatch can be used to measure viscosity, with the operator adding solvent to thin if necessary. For water-based inks, a stand-alone pH meter can give a quick and accu- rate reading of the alkalinity of the ink. At the mid range, mechanical viscosity maintainers will keep the ink at a preset point for the length of the run. Finally, automatic viscosity controllers, of varied designs, provide run-to-run repeat- ability, press interfaces, and precision hands-off control. Dealing with temperature is more an issue of alleviation than prevention. As most of the heat generated comes from ambient conditions and friction in the inking system, there is little the operator can do to stop heat from being added. Climate control in the printing facility will help, but adding this is usually not an option short of major construction. Ad- ditionally, running pumps with a variable- speed drive to only pump what is needed will aid in keeping heat in check. Eliminating heat and controlling tem- perature needs to be done with a heat exchanger. There are two typical styles available to the printer—water-jacketed tanks and in-line cooling units. Water- jacketed tanks allow chilled water to flow around the tank, usually on the bottom to prevent condensation from running into the ink. In-line exchangers typically use water flowing through copper pipe or across flat plates to draw heat from the ink as it is being pumped. Either system should be integrated with a control to avoid over-chilling the ink, and the resul- tant problems that would create. PUTTING IT INTO PRACTICE Implementing the “Four C’s ” of Total Ink Dynamics is a relatively minor cost compared to both the upfront cost of a press and the continuing operating costs, such as labor, energy, substrate, and ink. But the payback can be great, especially in terms of providing the length of run and run-to-run consistency your customers demand. Start with one deck and experiment with solutions to the four categories. Ask your vendors to audit what you are do- ing and recommend potential improve- ments. Continually benchmark your progress. Analyze the value of changes against the benefits they provide. In a short time, we are confident that you will see improvements that your customers—and your CFO— will appreciate. n About the Authors: Craig Shields is president, Graymills Corp. , Chicago, IL. Ed Dedman is director of emerging technologies. The two specialize in ink delivery system design and engineering. 40 FLEXO november 2011 www.flexography.org Your Location Our Location Online Maximize the effectiveness of your personnel, equipment, software and materials. A&V offers training programs and support designed for every level of flexo experience. Training is offered on-site at your location, our locations or online. Take advantage of our cloud- based training sessions. • Process Control Technology • Sustainability Training • Basic Plate Processing Training • Color Management • FlexSysTM Simulator Training • Workflow Training • Training for Emerging Technologies • Press Characterization • G7 Certified Expert Training on Staff Flexo Training & Technologies 866.282.7697 | fx 800.223.6869 www.AndVre.com | info@AndVre.com AV 9626 TrainingTech_ad.indd 1 8/9/11 9:54:32 AM FLX_November11.indd 40 11/8/11 3:54 PM