This paper deals with the radii of draw dies for sheet metal parts, like fenders, hoods, and doors. For relative flat parts, like hoods, it is important to get at least a 2% forming rate in the middle of the part to reach minimum of stiffness, work hardening, and sufficient geometric accuracy. This can be influenced by the punch radii. Therefore, optimal punch radii should be known.
First experimental results about optimal punch radii where published by J.L. Duncan and B.S. Shabel in the SAE-Paper No. 780391.
At the Institute for Metal Forming Technology of the University of Stuttgart, Germany, a “Modified Duncan Shabel Test” (MDS-Test) has been developed. This test makes it possible to investigate not only the punch radii but also the die radii.
This paper shows optimal punch and die radii as a function of sheet metal, sheet thickness, as well as of the die material.