Movement control apparatus for machine tool

A movement control apparatus for a machine tool, comprising:

• a tool post with a plurality of tools arranged parallel for machining a workpiece;
• a drive unit adapted to move at least one of the tool post and the workpiece in a direction of a first axis and in a direction of a second axis that intersects the first axis to make a relative movement happen between the workpiece and the tool post, and adapted to overlap the movement in the first axis direction and the movement in the second axis direction to make the relative movement happen in such a manner that the workpiece moves around the periphery of the tool post, thereby changing the tools;
• a travel boundary arc setting unit adapted to set a travel boundary arc in such a manner that the travel boundary arc is inscribed in the first and the second axes and an axial center of the workpiece or a forward end center of the workpiece passes through a position distant from a corner portion of a tool by a radius of the workpiece;
• and
• a control unit adapted to control the drive unit to make the relative movement happen in such a manner that the workpiece moves around the periphery of the tool post from the first axis to the second axis along a travel locus outside the travel boundary arc.