Optimisation of the Stamping Processes for a Drawn-Part Made of Aluminium

Abstract

The present work has been undertaken in order to investigate the possibilities of improvements in the production technology of aluminium drawn-parts. Past technology does not guarantee the production of high quality elements. Aluminium is difficult to use in sheet-metal working processes, mainly because of a susceptibility to the formation of aluminium „build-ups” on the tools, i.e. on the punch and die. The “build-ups” can be limited or even completely eliminated by a proper selection of the technological lubricants and proper surface treatment of the tools (e.g. surface coatings). In order to determine the influence of some technological lubricants and anti-adhesive layers on frictional resistance occurring during the sheet-metal forming process a typical “strip-drawing” test has been carried out. 1050A aluminium strips with thickness of 0.5mm have been drawn between two steel die inserts. Tests have been carried out with lubrication and in dry conditions. Additionally, two anti-adhesive coatings - TiN and Cr coatings were tested. Friction coefficients for different frictional pairs have been determined. In order to analyse how friction impacts on the course of sheet-metal forming process a numerical simulation based on the finite element method was performed. A four-stage stamping process of an aluminium cup was analysed. The value of the friction coefficient was changed in order to take into account frictional resistance. Thickness of the cup walls was assumed as one of the parameters determining the usefulness of the drawn-part because it determines its strength.