CAx-chain in robot-based incremental sheet metal forming

As a result of constantly growing market requirements for customized small-scale production and prototyping, Roboforming (robot-based incremental forming) is developed for sheet metal forming in a quick, precise and dieless way. In the Roboforming-process, two KUKA robots hold respectively a forming and a supporting tool which have a universal ball-sized structure. The sheet is firmly clamped in a fixture frame and both robots are connected to a robot controller realizing the synchronization. Similar to other incremental forming methods, the final shape of workpiece is kinematically generated by the movement of the forming tool along the lateral direction and its gradual infeed in the depth direction. Additionally, the use of the movable supporting tool raises the process accuracy and further increases the production flexibility by abandoning the structure-specified die. The objective of this work is to develop a CAx-chain in Roboforming, including CAM and CAE, which are responsible for the tool path generation and the process simulation. Compared to the traditional forming processes like deep drawing or stretch forming, the dies are replaced by a universal forming tool and its related long trajectory. The effort and time spent on dies are transferred to generate an adequate tool path in AISF (Asymmetric Incremental Forming). High demands are put on developing a specific CAM-system to fulfill all the requirements including different forming strategies. Therefore the CAM-system always plays a key role in AISF. Compared to a capable NC-machine, the use of a robot system and two synchronized universal tools in Roboforming can further reduce the investment cost and raise the process flexibility, but it increases the difficulty of path generation because there is no mature CAM-solution available for Roboforming. Thus the developed CAM-solution in this work can export adequate files for the applied robot control system as well as realize different forming strategies involving two synchronized tools. After the CAM-process, a CAE-model is built up responsible for the robot animation in a virtual robot-cell. It proves the correctness of tool path and avoids any unwanted collision during the later forming process, which ensures the process safety. By considering the real material properties and various process conditions inside, another FE-model is able to predict the forming results like geometrical deviation and forming force. The whole CAx-chain is a basis for the development of Roboforming and makes the advantages of this innovative method carried forward.