Volume Morphing to Compensate Stamping Springback 2009-01-0982
A common occurrence in computer aided design is the need to make changes to an existing CAD model to compensate for shape changes which occur during a manufacturing process. For instance, finite element analysis of die forming or die tryout results may indicate that a stamped panel springs back after the press line operation so that the final shape is different from nominal shape. Springback may be corrected by redesigning the die face so that the stamped panel springs back to the nominal shape. When done manually, this redesign process is often time consuming and expensive.
This article presents a computer program, FESHAPE, that reshapes the CAD or finite element mesh models automatically. The method is based on the technique of volume morphing pioneered by Sederberg and Parry [Sederberg 1986] and refined in [Sarraga 2004]. Volume morphing reshapes regions of surfaces or meshes by reshaping volumes containing those regions. Since then, FESHAPE has been significantly enhanced further through extensive production applications and validations of more than five hundred stamping dies (draw, trim and flange).
The method is applied in an automotive setting and used to compensate springback in sheet metal stampings. Springback data consists of displacement vectors distributed throughout a panel. These vectors can be node displacements predicted by finite element analysis or calculated by the measurements from a scanned die tryout panel. The displacements are much smaller than the lengths and widths of panels and generally affect large regions of the panel.
FESHAPE morphing uses displacement vectors to control the morphing distance and direction. There are many options to create the various types of volumes and boundary conditions for specific applications. Features include global morphing, local region morphing, iterative morphing as well as methods to interpolate or modify the displacement vectors.