Tool Path Generation for Free Form Surfaces in Robot-Based Incremental Sheet Metal Forming

摘要

This paper describes a new development in incremental, robot-based sheet metal forming (Roboforming). Roboforming is a dieless sheet metal forming process which ensures cost-effective manufacturing of prototype parts and small batches. Its principle is based on flexible shaping by means of a freely programmable path synchronous movement of two industrial robots driving work-piece independent forming tools. The final shape is produced by the incremental inward motion of the forming tool in depth direction and its movement along the contour in lateral direction on a helical path. The supporting tool, with its simple geometry, holds the sheet on the backside by moving synchronously along the outer contour, at constant depth. In this way no special dies are needed. For milling machines, which are used in numerous incremental forming approaches, CAD/CAM interfaces exist for generating necessary tool paths. For industrial robots only a few simple solutions emerge, which do not have the potential of classical CAD/CAM interfaces and are unusable for cooperating robot systems. While the two coupled robot programs can be programmed manually for simple geometries, this approach does not work for complex geometries. In this paper a further development in robot programming systems is presented that is now able to derive helical tool paths from any CAD file and generate two cooperating programs for the forming and the supporting tools. The helixes pitch is variable and dependent on the geometry's wall angle. To increase the part accuracy a process database is used, that stores relevant information about the process parameters, sensor data and used equipment. Based on this information strategies for increasing the part accuracy can be applied.