Controller for machining device and control method for machining device

A control method for a machining device, the machining device including a table that holds a workpiece, a main shaft that holds a tapping tool, a first feed motor that relatively moves the table and the main shaft in a first direction parallel to a longitudinal axis of the main shaft, a second feed motor that relatively moves the table and the main shaft in a second direction intersecting the longitudinal axis, and a main shaft motor that rotates the main shaft around the longitudinal axis,

• wherein the control method involves controlling the first feed motor to move a distal end of the tool between a retracted position where the distal end of the tool is retracted from the workpiece and a predetermined depth position in the workpiece, controlling the second feed motor to position each of a plurality of tapping positions of the workpiece relative to the tool, and controlling the main shaft motor to control rotation of the tool, the control method comprising:
• a tapping step of performing tapping at one of the tapping positions by moving the distal end of the tool from the retracted position to the predetermined depth position while rotating the tool in a normal direction;
• a retracting step of retracting the tool from the workpiece by moving the distal end of the tool from the predetermined depth position to the retracted position without stopping while rotating the tool in a reverse direction;
• a positioning step of positioning a subsequent one of the tapping positions relative to the tool and switching a rotational direction of the tool from the reverse direction to the normal direction, the tapping step, the retracting step, and the positioning step being repeated sequentially;
• a step of starting relative movement of the workpiece and the tool in the positioning step at the same time as when the distal end of the tool passes a reference position between the workpiece and the retracted position in the retracting step;
• a step of completing the relative movement of the workpiece and the tool in the positioning step at the same time as when the distal end of the tool passes the reference position in the tapping step;
• and
• a step of controlling a timing at which acceleration of the relative movement of the workpiece and the tool finishes in the tapping step and a timing at which deceleration of the relative movement of the workpiece and the tool starts in the retracting step based on a distance from the one tapping position to the subsequent tapping position in the second direction.