Method and device for controlling the working depth for a numerically controlled machine tool.

摘要

The device is provided on a machine tool, wherein the drilling or milling operating head (12) comprises an axially movable spindle (14) and a workpiece hold-down (17), and wherein the working depth is controlled according to the relative position of the tool (16) with respect to the hold-down (17), defined by sensing a reference member (56) by means of the tool (16). To avoid the errors due to the thermal expansion in defining the reference position between the tool and the hold-down, before the reference member (56) is sensed, an electric power supply heats the spindle (14) by sequentially energizing the phases of the statoric coil of the spindle electric motor (76). The reference member (56) comprises a proximity sensor (64) operated by the tool (16) through an air pad piston (67).