Model-based ‘Chase-the-Ball’ Calibration of a 5-Axes Machining Center

A procedure for model-based calibrating 5-axes machining centers is presented. Machine errors cause relative TCP deviations between a sphere and probing system that can be measured in X, Y and Z simultaneously during a five axes measurement cycle. The exact kinematic configuration of the machine tool can be identified by numerically reproducing the errors that would cause deviations closest to the ones measured. The measuring device, the machine model and the measurement procedure are described briefly. A method well known in robotics is applied to evaluate the mathematical stability of the error identification. With it a suitable number and location of measuring poses and a suitable model setup can be determined. A new general Monte Carlo approach using a full machine error model is applied to determine the expected overall geometric behavior of the machine tool after the calibration. With it uncertainty estimations can be made for any calibration approach. Finally, measurement results before and after the calibration are shown.