Study on the usability and robustness of polymer and wood materials for tooling in sheet metal forming

Abstract

The traditional market of sheet metal parts is based in high production volumes normally greater than 10.000 parts by using high-speed presses and highly automated operations, being the tooling usually made from steel or cast iron, which ensures the needed robustness for such production volumes. Current trends in stamping industries can be characterized by the increasing demand for individualization of products which leads to a growing development towards an increasing number of product variants, lower production volumes and shorter innovation cycles. These trends have triggered research in the development of faster and cost-effective tool manufacturing techniques suitable for low production volumes, since high investments in steel tools can only be compensated by huge volume series of one and the same part during long life cycles. A promising approach for production of small series of complex sheet metal parts is the use of non-conventional tooling materials such as polymers, wood and low melting point metals. The usage of these alternative materials in tooling is still looked with some suspicion, due to the lack of know-how on its processing and also on its wear durability, influenced by the required product geometry, blank material and expected production volume. In this paper a study on the use of non conventional materials for tooling, to be used for producing a complex sheet metal part, is performed. The evolution of tool wear, roughness and geometrical changes in punch and die radius were measured and its influence in the stamped part geometry evaluated, for an imposed production volume target of 500 parts. Also a comparative study of the tooling costs is presented in order to assess the aptitude and economical feasibility of the use of these tooling materials for low production series.