Control device for machine tools and machine tool control method

A machine tool control device which controls a machine tool having a spindle and a feed axis, wherein the spindle relatively rotates a cutting tool and a workpiece, the feed axis relatively moves the cutting tool and the workpiece, and the machine tool cuts the workpiece by cooperatively operating the spindle and the feed axis, the control device comprising:

• a feed command calculation unit which calculates a feed command for moving the feed axis relative to the workpiece;
• an oscillation phase calculation unit which calculates an oscillation phase that is a phase of oscillation for reciprocally moving the feed axis based on number of rotations of the spindle;
• an oscillation phase compensation unit which compensates the oscillation phase;
• an oscillation amplitude calculation unit which calculates an oscillation amplitude that is an amplitude of oscillation for reciprocally moving the feed axis based on the feed command;
• an oscillation command calculation unit which calculates an oscillation command for reciprocally moving the feed axis based on the oscillation amplitude and the oscillation phase after the compensation of the oscillation phase by the oscillation phase compensation unit;
• and
• a command synthesizing unit which calculates a synthetic command for driving the feed axis by superimposing the feed command and the oscillation command,
• wherein the oscillation phase compensation unit advances the oscillation phase when a position of the feed axis in the synthetic command is in an upwardly convex range of a trajectory of the feed axis and delays the oscillation phase when the position of the feed axis in the synthetic command is in a downwardly convex range of the trajectory of the feed axis.