Control of a Sequential Brakeforming Process

The process of sequential three point bending (or “bumpforming”) is often used to produce smoothly varying simple curvature parts. The process involves bending and incrementing the bend line in sequence to produce the desired curvature profile along the arc length of the part. The actual shape produced represents the integration of small local shape changes, and the opportunity for error is great since knowledge of the bending properties of the material is required to accurately plan and execute the sequence. As a result, the manual process is slow and highly inaccurate. In this paper an in-process control method is presented that performs two functions: 1) sequence planning based upon an optimization between allowable variations about the desired shape and processing time; and 2) closed-loop control of the desired shape to insure accurate parts even when material properties or dimensions change.