Control of the fabrication of long slender workpieces of arbitrary shape—part I: Open-loop control of the multi-axis bending process

Computer numerically controlled (CMC) multi-axis bending is a new metal-forming process usedto fabricate long slender workpieces of arbitrary shape and cross section. This process can achieve higher productivity and flexibility than conventional forming processes. However, a manual trial-and-error process has been adopted to find control commands that would produce accurate part shape in massproduction. This traditional approach which completely relies on the skills of the machine operator often results in long lead-times and great cost in setting up the bender for a new part. A new methodology has been developed, using the geometrical concept of intrinsic part representation, to model theworkpiece and fabricating process. The process model compensates for elastic springback, and can beused to predict a set of initial multi-axis control commands which will eventually converge to the final commands through a feedback process. The effectiveness of the method has been demonstrated experimentally.