Optimization of the Calibration Process in Freeform Bending Regarding Robustness and Experimental Effort

In the freeform bending process, the obtained geometry is determined by the kinematics of the bending head. In order to derive the motion profiles leading to a part within tolerances, the correlations between bending results and machine settings are investigated. This inverse problem is solved by generating calibration curves, whose aim is to correlate the bending radii with the head movement from experimental tests results. Nevertheless, slight adjustments in the shape of the calibration curves show a significant impact on the bending results. In this paper, the robustness of the calibration process is investigated. First, the effect of different interpolating methods is considered. In addition, the influence of the experimental points is examined by comparing the performance of global and local data for the interpolation. Finally, calibration curves obtained with different ratios between the translation and the rotation degrees of freedom are compared. In this way, the interactions between the given parameters are investigated and a more efficient process for calibrating the freeform bending machine can be determined. This allows the reduction of the experimental effort for determining the relation between the machine parameters and the bent result as well as optimizing the process with respect to the geometrical deviations and dimensional stability.