Using Volume Morphing to Alter Panel Designs to Compensate Shape Distortion in Assembly

As automotive panels are assembled in a vehicle, they are subjected to shape distorting forces, e.g., the pressure of door seals. A standard technique for preventing shape distortions is to alter the panels’ computer aided design (CAD) in such a way that the panels assume the desired design shape under the action of the distorting forces. Volume morphing, a technique pioneered by Bézier (1978, “General Distortion of an Ensemble of Biparametric Patches,” Comput.-Aided Des., 10(2), pp. 116–120) and by Sederberg and Parry (1986, “Free-Form Deformation of Solid Geometric Models,” International Conference on Computer Graphics and Interactive Techniques, Proceedings of the 13th Annual Conference on Computer Graphics, pp. 151–160), has been extended and implemented in a computer software package called FESHAPE, created at the General Motors Research and Development Center. FESHAPE automatically modifies CAD models according to a finite set of displacement vectors obtained, e.g., from finite-element analysis or scanning tryout parts. This article discusses how FESHAPE has been successfully applied to compensate door panel distortion caused by door seals.