Control device for machine tool performing oscillation cutting

A control device for controlling a machine tool for cutting an outer peripheral surface or an inner peripheral surface of a workpiece with a tool, the machine tool having a main shaft for performing a relative rotation between the workpiece and the tool around a central axis of the workpiece, and at least one feed shaft for performing a relative feeding between the tool and the workpiece along a generatrix of the outer peripheral surface or the inner peripheral surface of the workpiece, the control device comprising:

• a position command generation part for generating a position command for the at least one feed shaft based on a relative rotation speed of the workpiece and the tool and a relative feed speed of the tool and the workpiece;
• and
• a feed shaft control part that controls the at least one feed shaft according to the position command,
• the feed shaft control part comprising an oscillation command generation part that generates an oscillation command for the at least one feed shaft such that the tool performs intermittent cutting on the workpiece, the feed shaft control part being configured to generate a torque command based on a resultant command obtained by adding the oscillation command to a position deviation, which is a difference between the position command and an actual position of the at least one feed shaft to thereby control the at least one feed shaft;
• the feed shaft control part further comprising an elastic deformation amount calculation part for calculating an elastic deformation amount of a structure between an output terminal of the at least one feed shaft and a machine oscillating terminal which produces oscillation for the intermittent cutting, based on the torque command;
• wherein
• the oscillation command generation part generates the oscillation command based on the rotation speed, the position command, and the elastic deformation amount such that the oscillation command becomes a positive non-integral multiple of the oscillation frequency with respect to the rotation speed.