The proportion of dies that are stored with residual aluminum (die prefill rate) has a strong influence on the cost of die shop operations. Prefilled dies require less die shop labor, consume less caustic chemicals, and are not damaged in handling or maintenance. This paper statistically examines the relationships between prefill rate, die failure rate, storage time, and die shop costs in a 4-press soft alloy (6060/6063) plant. Surface finish die failure rate was not increased by storing dies for more than one year, prefilled or not. Prefilled dies gave a slightly higher die failure rate than non-prefilled dies, but the difference was outweighed by the cost savings from using prefill. Other influences on prefill practices are discussed, with emphasis on how to maximize prefill rate without adversely affecting extrusion performance.
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