Prediction of Path Deviation in Robot Based Incremental Sheet Metal Forming by Means of an Integrated Finite Element – Multi Body System Model

Abstract

The main influence on the dimensional accuracy in incremental sheet metal forming results from the compliance of the involved machine structures and the springback effects of the workpiece. This holds especially for robot based sheet metal forming, as the stiffness of the robot’s kinematics compared to a conventional machine tool is low, resulting in a significant deviation of the planned tool path and therefore in a shape of insufficient quality. To predict these deviations, a coupled process structure model has been implemented. It consists of a finite element (FE) approach to simulate the sheet forming and a multi body system (MBS) modeling the compliant robot structure. The forces in the tool tip are computed by the FEA, while the path deviations due to these forces can be obtained using the MBS model. Coupling both models gives the true path driven by the robots. Built on this path prediction, mechanisms to compensate the robot’s kinematics can be implemented. The current paper describes an exemplary model based path prediction and its validation.