CONTROL APPARATUS AND METHOD FOR HOLDING A WORKPIECE IN A MACHINE TOOL.

摘要

A machine tool such as a lathe for machining a workpiece (5) having a longitudinal axis and being held at opposite axial ends by face drivers (33, 34) that are affixed to the spindle of a respective moveable headstock (12, 22) and securely contact the workpiece end faces with a predetermined pressure. A first servo loop is established to control the position of the headstock (12, 22) on the basis of detected position information and a second servo loop is established to control the movement of the headstock (12, 22) so that the pressure against the workpiece end faces is kept at predetermined values. The second servo loop may utilize the detected position of the headstock (12, 22) or it may utilize the monitored command value for purposes of judging whether modifications to the command value are necessary to provide the desired pressure values. A torque limiter also may be used to provide the desired control.