Provided is a control device for a machine tool that can suitably shred chips in a state without good conformability. A control device for a machine tool which oscillates a tool and a workpiece relative to each other while machining comprises: a comparison unit that compares the oscillation amplitude calculated value calculated by an oscillation amplitude calculation unit and the oscillation amplitude minimum value set by a minimum value setting unit; an oscillation command generation unit that generates an oscillation command on the basis of the oscillation condition and the value of the oscillation amplitude obtained from the comparison results of the comparison unit; and a position/speed control unit that oscillates the workpiece and the tool relative to each other on the basis of a superimposition command obtained by superimposing the oscillation command over a position command.

The purpose of the present invention is to both break down chips and suppress sympathetic vibration in a machine. This work machine control device superposes a swinging command for commanding relative swinging between a workpiece and a cutting tool onto a movement command for commanding relative movement between the workpiece and the cutting tool, thereby generating air cuts in chips from the workpiece to break down the chips. A position information acquisition unit of the work machine control device acquires position information related to the relative positions of the workpiece and the tool. A state assessment unit of the work machine control device assesses that a state of instability is in effect, under the condition that a positional deviation exceeds a threshold value, the positional deviation increasing with increases in the difference between actual relative positions that are based on the position information and command relative positions that are based on the movement command and the swinging command. A swinging switching unit of the work machine control device performs a switching process for switching a swinging condition in relative swinging, under the condition that it is assessed that the state of instability is in effect.

Provided is a machine tool control device that can realize a desired scrap length while suppressing deterioration in machining accuracy. This control device 1 is for a machine tool which performs machining while causing a tool and a workpiece to oscillate relative to each other, the control device 1 being provided with: an oscillation command generation unit 13 for generating an oscillation command on the basis of an oscillation condition; an oscillation command correction unit 14 for correcting the oscillation command so that main-axis phases in given oscillation phases are not identical to each other; and a position/speed control unit 18 for causing the tool and the workpiece to oscillate relative to each other on the basis of a superposition command generated by superposing the oscillation command corrected by the oscillation command correction unit 14 on a movement command.