Metal Finishing Guide Book

2012-2013

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finishing equipment & plant engineering IMPORTANCE OF RACK DENSITY BY DAN DAVITZ PRODUCTION PLUS CORP., COLUMBUS, OHIO In any coating process there are four main requirements: careful surface preparation, the proper coating, a good application system, and a well-designed racking system. One may ask, ���Why would a well-designed racking system be a requirement for any coating process?��� It is one thing to coat a sample part for a customer to prove what your capabilities are; however, it is something else altogether to coat the same part on a full production line and make a profit doing it. Making a profit requires coating as many pieces as possible quickly and efficiently while maintaining the highest level of quality. There are two keys to a profitable production finishing line: the line speed, which determines the number of cycles per hour per day, and the number of parts racked on the line for finishing. The reason that these two keys are so important to a profitable finishing line is that when you consider washing, rinsing, drying, cooling, coating, baking, and handling, along with building space, utilities, waste disposal, and rejects, each of these overhead factors is related to how many part scan be processed per hanger, or per cycle. In other words, part density directly affects profit. If there is anything that should stimulate your thinking about racking, it should be the impact that high-density racks can have on your production finishing line. THE WELL-DESIGNED RACKING SYSTEM A well-designed rack will address four areas: part density, proper grounding, rack maintenance, and flexibility. Part Density Most racks are welded structures designed to handle as many different parts as possible (see Fig. 1). Because they are welded, the vertical space between parts is set for the longest part to be hung. When shorter parts are hung, there is wasted vertical space between pieces. The same principle is true when applied to the horizontal spacing between pieces. Part hooks are welded at distances set for holding the widest part and thus, when smaller width parts are hung, the horizontal space between parts is wasted. With regard to part density, the best type of rack will be adjustable to allow for variables in both the vertical and horizontal spacing and Fig. 1. Side bars adjust vertical spacing, and removable hooks maximize part density in both directions. The adjust horizontal spacing. side bars of the rack should allow for up-anddown movement of the horizontal cross members to eliminate wasted vertical space. Part hooks should be adjustable at any time (even between cleanings), to 844

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