The failure analysis of a deep drawing die in the manufacturing of an automotive shock absorber cap

A deep drawing die, employed in the manufacturing of an automotive shock absorber endcap presented premature wear in a part of the region of contact with the blank. This led to unacceptable scratching and surface finish in the produced endcaps, resulting in an excessive scrap rate and undesirable finishing operations in order to repair the defects, when possible at all. Initially, the surfaces of parts produced in new and in worn dies were analyzed. The loads and strains in the endcap and in the dies were then evaluated, through a finite element analysis (FEA) utilizing the DEFORM 7.0 software. The validation of the simulation was performed comparing the experimental measurements of the part thickness with those supplied by the numerical simulation. The validated FEA model indicated an excessive pressure on the worn region, reaching unacceptable levels for the chosen die material. The solution to the failure would involve a change either in the die material, or in the process design, or in the die/blank lubrication.