Patent ID: 6437534
Filing Date: 2002-08-20
Classification: G05B

Abstract:
A method of controlling an NC machine tool which has a feed drive system and is operative on the basis of a machining program, the control method comprising:generating an operation command signal on the basis of the machining program and a time constant; generating a velocity command signal by multiplying a deviation of a present position signal fed back from the feed drive system from the generated operation command signal by a position loop gain; generating an electric current command signal by multiplying a deviation of a present velocity signal fed back from the feed drive system from the generated velocity command signal by a velocity loop gain; and controlling a drive motor of the feed drive system on the basis of the generated electric current command signal for driving thereof, wherein a machining mode is determined from the machining program and, if the machining mode is a drilling mode, the operation command signal is modified by adding a predetermined operation modification value to the operation command signal, and the generation of the velocity command signal is based on the modified operation command signal when the feed drive system is driven to be retracted opposite to a drilling feed direction.