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

A method for aligning a workpiece with an axis of rotation of a machine tool, wherein the workpiece comprises a longitudinally-extending, hollow shaft defining an outer surface and an inner cavity comprising an annular workpiece contour extending for a length of the workpiece, wherein a first end of the workpiece is engaged with a first rotatable chuck of the machine tool and the workpiece is supported by a first clamping support and a second clamping support of the machine tool that engage the outer surface of the workpiece, the method comprising:

• (a) positioning at least one sensor supported by a tool carrier of the machine tool in proximity to the annular workpiece contour;
• (b) measuring, with the at least one sensor, a distance between the at least one sensor and the workpiece contour, wherein measuring the distance is carried out over a plurality of defined angles of the annular workpiece contour and at a plurality of locations along the length of the workpiece to obtain measurement data;
• (c) calculating a geometric center point of the workpiece at each of two or more of the plurality of locations along the length of the workpiece to obtain two or more geometric center points of the workpiece;
• (d) calculating an approximated longitudinal central axis of the workpiece from the two or more geometric center points of the workpiece;
• (e) disengaging the first clamping support from the outer surface of the workpiece;
• (f) machining a plurality of first clamping seats in the outer surface of the workpiece and radially concentric to the approximated longitudinal central axis of the workpiece;
• (g) engaging the first clamping support with a first one of the plurality of first concentric clamping seats in the outer surface of the workpiece;
• (h) disengaging the second clamping support from the outer surface of the workpiece;
• (i) disengaging the first end of the workpiece from the first rotatable chuck of the machine tool;
• (j) engaging a second end of the workpiece with a second rotatable chuck of the machine tool, wherein the second end of the workpiece comprises a second one of the plurality of first concentric clamping seats in the outer surface of the workpiece;
• (k) machining a plurality of second clamping seats in the outer surface of the workpiece and radially concentric to the approximated longitudinal central axis of the workpiece;
• (l) engaging the second clamping support with a first one of the plurality of second concentric clamping seats in the outer surface of the workpiece;
• (m) disengaging the first clamping support from the first one of the plurality of first concentric clamping seats in the outer surface of the workpiece;
• (n) disengaging the second end of the workpiece from the second rotatable chuck of the machine tool;
• and
• (o) engaging the first end of the workpiece with the first rotatable chuck of the machine tool, wherein the first end of the workpiece comprises a second one of the plurality of second concentric clamping seats in the outer surface of the workpiece.