Precision Die Design by The Die Expansion Method

Abstract

A new method for the design of precision dies used in cold forging, extrusion and drawing processes is presented. It is based on die expansion. It attempts to provide a clear-cut theoretical basis for the selection of critical die dimensions for this group of precision dies when the tolerance on product diameter (or thickness) is specified. It also presents a procedure for selecting the minimum-production-cost die from a set of design alternatives. The results show that as external die diameter increases, die expansion decreases while die strength increases. Also, as the degree of die compounding increases, die expansion decreases and die strength increases. Comparison of theoretical and experimental results shows good agreement especially at full die cavity filling stage. Die selection from a set of multi-layer dies is based on the die that has minimum Design Effectiveness Index (DEI) which gives the minimum-production-cost die. It is hoped that the design method, apart from providing solutions to simple design problems, can be applied as a first approximation to the solution of more complex problems, based on a clear-cut theory rather than the usual rule-of-thumb method. Thereafter, more sophisticated computer-based methods may be applied for refinement.