Adaptive Clamping Control on High Performance CNC Lathes

Abstract

The loss of clamping force caused by centrifugal forces is one of the major workpiece-holding problems on high speed and high performance CNC lathes today. The Adaptive Clamping Control has been developed in order to improve the work-piece-holding process. The hydraulic pressure of the clamping cylinder is set on a programmed value by means of proportional pressure valves and pressure transducers and controlled by the NC. The pressure controlled is dependent on the speed level, gripping diameter and jaw-geometry. However some other important parameters also have to be taken into consideration such as: workpiece-stiffness, tip-stiffness of jaws and chuck-stiffness.

A computer macroprogram has been developed to program clamping in connection with the workpiece programming on the CNC lathe. By setting the relevant clamping parameters into the program, the hydraulic pressure values are automatically calculated and controlled by the NC in such a way that constant gripping force can be kept on the machine independent of the speed level.