The Correlation Between Punch Forces and Wrinkling for Aluminum Sheet Metal Stamping with Adjustable Drawbeads

An experimental investigation into punch forces during a sheet metal stamping operation was performed for a sheet metal stamping die with a flexible blankholder and adjustable drawbeads. Tests were performed for various combinations of blankholder force and drawbead positions. Punch forces were measured using an instrumented punch and wrinkling in the sheet flange was measured during the forming processes using non-contact proximity sensors located near the blankholder edge. The results were correlated with those of the punch forces. Additionally, using a wrinkle criterion based upon part quality, an operating envelope for the die system was obtained and the relation between drawdepth, drawbead penetration, and blankholder forces was developed for the die system.