Correction Method at Time of Feed Axis Reversal

A stick motion correction method which corrects stick motion which occurs at the time of reversal of a movement direction of a feed axis of a numerical control machine tool, which stick motion correction method comprising steps of:

• storing a position command to be commanded to a servo motor from an NC program of said numerical control machine tool for each predetermined control period from a current position command to a position command after a predetermined time;
• calculating a reversal correction command based on the stored position commands;
• calculating an advancement time for advancing a timing of addition of said reversal correction command to a speed command or torque command of said servo motor from the reversal timing of said servo motor, based on information obtained from operation of said servo motor or commands to said servo motor;
• and
• adding said reversal correction command to the speed command or torque command of said servo motor to correct stick motion at a timing advanced from the reversal timing of said servo motor by exactly said advancement time.