Developing an automated system for predicting the shape and volume of an air pocket on the draw die

Abstract

Metal stamping is widely used in the mass-production process of automobile manufacturing. During the stamping process, air may be trapped between the draw die and the panel and/or between the punch and the panel. The air pocket not only rapidly increases the forming load in the final stage, but also deforms the product just formed because of compressive air inside the air pocket in the knockout process. To prevent these problems, air bent holes are drilled in the die to exhaust the trapped air, but all processes associated with the air bent holes are performed based on the empirical know-how of workers in the field due to lack of data on shape and location of an air pocket in the stamping process. Therefore, this study developed an automated design system for predicting the shape, position, and volume of the air pocket on the draw die by using the AutoLISP language in AutoCAD. The system is able to display the shape of the air pocket built up in the draw die and to calculate automatically its volume by strokes. Therefore, the theoretical size and the number of air bent holes are calculated by predicting and analyzing the position and volume of the air pocket. Results obtained from the system can be used by the designers or manufacturers of the stamping die to carry out field work more efficiently.