Failure Analysis of Rapid Prototyped Tooling in Sheet Metal Forming—V-Die Bending

The demand for rapid, low-cost die fabrication and modification technology is greater than ever in the sheet metal forming industry. One category of rapid tooling technology involves the use of advanced polymers and composite materials to fabricate metal forming dies. However, due to their lack of strength as compared to conventional metal dies, the use of polymer dies is often limited to prototype or short-run production. In addition, because the mechanisms by which they fail are not fully understood, the dies are designed on the basis of experience and intuition. This study investigates the failure of V-bending dies fabricated from an easy-to-machine, polyurethane-based, composite board stock. Based on the mechanical behavior of the die material, several failure criteria are proposed to predict die failure mode and the corresponding die life. Both computational and experimental methods are employed to assess the accuracy of the criteria and to identify the dominant process parameters in V-die bending.