A CAD-Driven Flexible Forming System for Three-Dimensional Sheet Metal Parts

A novel system for the forming of three dimensional sheet metal parts is described that can form a variety of part shapes without the need for fixed tooling, and given only geometry (CAD) information about the desired part. The central elements of this system are a tooling concept based on a programmable discrete die surface and closed-loop shape control. The former give the process the degrees of freedom to change shape rapidly, and the latter is used to insure that the correct shape is formed with a minimum of forming trials. A 540 kN (60 ton) lab press has been constructed with a 0.3 m (12 in) square pair of discrete tools that can be rapidly re-shaped between forming trials.

The shape control system uses measured part shapes to determine a shape error and to correct the tooling shape. This correction is based on a unique “Deformation Transfer Function” approach using a spatial frequency decomposition of the surface. Data is presented showing the forming limits of the discrete tooling concepts. The use of the shape control system is examined in a series of closed-loop forming experiments. In all cases the parts are formed to within the system accuracy in four forming trials two for calibration and two closed-loop cycles.