Casting rejects that are discovered during machining force foundries to produce extra castings to satisfy orders. When substantial numbers of parts are rejected, deliveries are delayed, machining time and costs are lost, and the product cost and lead-time is increased. The American Metalcasting Consortium (AMC), which is supported by The Defense Logistics Agency (DLA), the American Foundry Society (AFS), and selected foundries producing military castings has supported efforts to reduce foundry and machine shop scrap. In one of the project tasks, the University of Alabama at Birmingham (UAB) has worked with foundries producing military castings to implement casting technologies that will reduce casting rejects. Bulk density measurements and tests to measure mold binder content were performed on samples from fluidity spiral molds (70 percent silica /30 percent zircon), 100 percent zircon ring molds, and 70 percent silica /30 percent zircon ring molds. The experiments concluded that there were no significant differences in densities or in the amount of binder in them olds used in these experiments. Parts made from molds composed entirely of zircon were more dimensionally consistent than parts from molds made from 70 percent silica /30 percent zircon molds. The results indicate that the thermal expansion coefficient of the sand used to make the molds plays an important role in producing parts within their intended tolerances.
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