U.S. Philips Corporation

Gerrit H Van Gool

Johannes H Van Leest

Johan C Wijn

Arie Van Tooren

In a method for measuring a reference position of a tool relative to a workpiece, the tool is fastened to a first holder of a machine tool. The workpiece is to be manufactured using the tool and is fastened to a second holder of the machine tool. The tool provides a distinguishing mark on the workpiece in a predetermined reference position of the first holder relative to the second holder. Subsequently, the distinguishing mark is detected by a sensor. Therefore, the reference position of the tool relative to the workpiece is determined from a position of the first holder relative to the second holder. The tool and the sensor are fastened in fixed, permanent positions relative to one another and relative to the first holder. The accuracy of measurement of the position of the tool depends exclusively on the accuracy of positioning of the first holder relative to the second holder. The accuracy of machining the workpiece is not hurt by the accuracy of measurement of the reference position of the tool relative to the workpiece. The sensor may be optical, with a focusing error detector. The second holder may be rotatable about a Z-axis, with the first holder being displaceable parallel to an X-axis which is perpendicular to the Z-axis, and the distinguishing mark being a circular groove in a surface of the workpiece which extends perpendicularly to the Z-axis.

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Eindhoven, Netherlands

Gerrit H Van Gool