2012 Volume 53 Issue 616 Pages 434-438
Backward extrusion is the most common method of forming bosses within product cases. However, backward extrusion requires a very large forming load. To overcome this disadvantage, we developed bottom compression drawing to replace backward extrusion in our previous study. In this study, the formability and boss forming limit in bottom compression drawing are investigated by a series of experiments and finite element analysis. The results showed that the failure at the punch shoulder occurs when the radial tensile stress at the punch shoulder reaches the tensile strength of the sheet metal. With increasing surface roughness of the counterpunch, the formable zone of a solid boss expands. Adhesion on the counterpunch surface can be observed with repeated forming cycles under a dry condition, but the irregularity in the product configuration converges to a befitting level after a few forming cycles.