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FLEXO Magazine : October 2009
www.flexography.org OCTOBER 2009 FLEXO 41 Relief variation of .004” Relief variation of .0001” .067” Plates .030” Plates .067in. plates to .030in. without the need to re-fingerprint and produce new separations. PLATEMAKING SPEED & CONSISTENCY Today 's digital .030in. plates are extremely easy to process. Handling ultra-thin plates is easier on the operators, as there is less weight. This helps reduce damage and makes the ergonomics of loading large plates into the equipment easier. Complete solvent processing of thin plates from exposure through detack takes a little less than an hour (depending on the equipment). One of the most frustrating aspects of traditional platemaking has been setting the back exposure and maintaining consistent relief depth. Many plates each year are rejected due to variation in the plate relief as a result of the variability of the back exposure or washout. With .030in. photopolymer plates, you wash the plate completely down to the PET backing. This means the usual floor variations seen with .067in. plates of +/- several thousandths of an inch are now just a few microns. This is good news for platemakers! For all intents and purposes, the relief is perfectly consistent at .023in. on every .030in. plate. REDUCED SHIPPING AND PACKAGING When switching from .067in. to .030in. plates, one elimi- nates about half of the finished plate weight. This is of tremen- dous benefit to companies that ship their plates. For example, using the online quotation* of UPS Co.'s next-day air service, a cost was calculated for shipping a box with seven plates 42in. by 60 in. in size from Chicago to Dallas. By simply reduc- ing the weight in changing from .067in. to .030in. plates, the quoted cost went from $191.85 to $138.70, a savings of $53.15 per shipment. In a year one would save $13,288 in ship- ping cost, based on just one shipment per business day, 50 weeks per year. Of course many companies ship much more than one job per day, so the savings would be even higher. (*Source: UPS.com June 1, 2009, Des Plaines IL to Irving TX, UPS Next Day Service, weight reduced from 54.2lbs to 30lbs in same-size box.) LESS DISTORTION AND CUPPING Due to less physical thickness of .030in. plates, they require about half the image elongation compensation of .067in. plates. Some types of work may not require any distortion at all. Another age-old problem is that of cupping. As thicker processed plates are mounted around cylinders, the solid images tend to distort, as the surface of the image stretches and pulls against the polymer beneath it. This happens more at the centers of solid images than at the edges. The result is that the plate edges poke outward, and the centers of im- ages depress down, forming the cup-like distortion. This is the reason why when operators set impression, the edges of the solids tend to print before the centers. More impression is needed to fully print solids and the long-term result can be shortened plate life, density variation, and over impression of fine details. Once again, thin is better. The .030in. plate in theory will always have less cupping distortion than the same material in .067in., resulting in more even and faster impres- sion setting with less long-term plate wear. BETTER FOR ECO-EFFICIENCY Another convincing benefit of thin plates is quite pertinent in today's market: sustainability. Thanks to the fact that thin- ner plates are made from less material and require less ma- terial and energy for processing, the calculated eco-efficiency benefits of .030in. plates as compared to .067in. are substan- tial. Based on data from the BASF Eco-Efficiency Analysis (EEA) published in the Nov. 2008 issue of FLEXO Magazine, we further calculate that using .030in. solvent processed plates would reduce global warming potential by an estimat- ed 32 percent along with an estimated 40 percent reduction in energy consumption. This benefit would hold true, accord- ing to the study, regardless if comparing to .067in. solvent or thermally processed plates. The reasons behind the figures are rather straight forward. Less polymer material results in less absorption of solvents in the wash, a shorter drying cycle, less packaging, and of course, less waste disposal at the end of the product life cycle. MAKING THE CONVERSION The leading concern with the use of .030in. plates is how to make the transition from thicker plates. If one owns presses, cylinders, and sleeves with an undercut for thicker plates, there may be tooling costs involved. The practicality of converting to .030in. plates really depends on the individual printer, so only general statements can be provided in this article. Printers are advised to meet with their plate, sleeve, tape, and press suppliers to discuss specific possibilities and the costs for implementation. In general, one must change to a larger diameter sleeve or cylinder to compensate for the thinner plate. To make up the difference, options include: FIGURE 2: A comparison of dot gain using a medium density cushion tape. FIGURE 3: Thinner plates result in more consistent washout and relief on, as compared to .067in. plates. TECHNOLOGIES & TECHNIQUES
Sustainable Fall 2009