Optimal die Design for Cold Extrusion Processes

Abstract

The design of cold extrusion processes requires the optimisation of several process variables in order to obtain a defect free product. The fulfilment of different objectives, such as the minimisation of forming loads or the homogeneity of the deformations, is highly requested. Nevertheless, several other relevant aspects of extrusion processes have to be taken into account and require a suitable optimisation of the process parameters and in particular of the die shape. In this paper, tool life has been assumed as the most relevant goal and an effective die design procedure as been setup. It is well known that fatigue cracking of the dies is the principal cause of dies failure in cold extrusion and that fatigue cracking is related to the stress/strain distribution in the zone of highest loading; thus the proposed approach is aimed to the research, through statistical techniques, of the function linking the die profile and the radial stress distribution in the die itself. By this way the most suitable die shape has been designed able to ensure the minimisation of the stress peak and an almost uniform pressure distribution at the specimen-die interface.