Method and device for determining centers of a hollow shaft rotatably clamped as a workpiece in a machine tool

A method for determining centers and the spatial course of these centers of a hollow shaft rotatably clamped in a machine tool as a workpiece, which shaft is machined on its outer surface at least in sections, the method comprising:

• that first of all, by means of at least one sensor operating according to the eddy current principle, the radial distances between the sensor and the workpiece contour are detected without contact at at least two defined axial positions in defined angular relative positions between the axis of rotation of the sensor and the axis of rotation of the hollow shaft over at least one full angle of the workpiece contour,
• in that a vector of polar coordinates with the values of angle and radius with radial distances is then formed by calculating any desired constant radius with respect to the detected radial distances, which vector is converted into Cartesian coordinates, and a geometric workpiece center point which can be assigned to the corresponding axial position of the hollow shaft is calculated by means of averaging,
• in that a center axis lying in space is then calculated from at least two workpiece center points calculated in this way at different axial positions by means of a regression analysis, which center axis approximates the workpiece center points and in that subsequently, starting from the center axis along the axis of rotation of the hollow shaft, any desired number of diameters concentric to the center axis are calculated, with which new clamping seats for the hollow shaft are machined, which define the axis of rotation of the hollow shaft anew and concentrically to the center axis.