Development of a Die Compensation Algorithm for Sheet Metal Stamping With Deformable Tools

The numerous sheet forming technologies that use rubber or flexible tools are generally based on one rigid (metallic) die or punch, in order to ensure a geometrical precision and repeatability of the parts. If, on the contrary, the complete tooling setup is based on deformable tools, the final part quality and geometry can be hardly predicted and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The implemented procedure is demonstrated with a tooling setup made of machined thermoset polyurethane punch, die and blankholder, for the production of an aluminum deep drawn part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic than steel. The proposed procedure is able, within a limited number of iterations, or even after the first step, to reduce the geometrical deviation between the actual stamped geometry and the reference part. This methodology represents one step towards the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.