Kinematic calibration

A calibration method for a numerical controlled machine tool, wherein the numerical controlled machine tool comprises a working table and a machine head with a main spindle, the numerical controlled machine tool further comprises at least 3 linear axes (X, Y, Z) and at least 2 rotation axes (A, B, C) by which the main spindle and the working table can be moved relatively to each other, the numerical controlled machine tool having a jig with a calibration ball mounted on the working table and the main spindle having mounted a touch probe, wherein the calibration method includes the step to measure the position of the calibration ball by conducting with the touch probe at least 4 contact measurements with the mounted touch probe, wherein the position of the calibration ball is changed at least three times by rotating the working table or the machine head around the rotation axes (A, B, C) and the step of measuring the position of the calibration ball is repeated for every position change of the calibration ball, and wherein the calibration method uses a kinematic model for generating from the at least three measured positions of the calibration ball a compensation model to compensate the kinematic errors occurring with a relative movement between the working table and the main spindle, wherein the calibration method measures the positions of the calibration ball with a measurement sequence which includes the combined movement of the calibration ball around at least two rotation axes (A, C, B), wherein the measurements around a first rotation axis (C, B, A) include at least two rotational position movements around a second axis (B, A, C);

• wherein the position of the calibration ball is measured in the coordinates of the linear axes X, Y and Z, wherein each measured calibration ball position (Xk, Yk, Zk) is memorized in a position table;
• and
• wherein the kinematic model of the calibration method calculates the kinematic error occurring by the movement of the rotation axes (A, B, C) based on the linear axis positions (Xk, Yk, Zk) memorized in the position table.