Numerical control apparatus

A numerical control apparatus that controls a machine tool including an X axis for moving a turret to which a plurality of tools are attached, an H axis for rotating the turret, and a C axis for rotating a work and not including a Y axis orthogonal to the X axis, the numerical control apparatus comprising:

• an imaginary-Y-axis control unit configured to execute an imaginary Y-axis control mode, the imaginary Y-axis control mode being a mode for converting an X-Y axes movement command in a machining program described in a program coordinate system into a command in a machine coordinate system including X-H-C axes and for driving the X axis, the H axis, and the C axis in association with one another according to the converted command;
• an acquiring unit configured to acquire, when an emergency stop occurs during the imaginary Y-axis control mode, present positions of the X axis, the C axis, and the H axis at time when the emergency stop is released;
• and
• a restoring unit configured to restore a present X-axis coordinate position and a present Y-axis coordinate position in the program coordinate system from the acquired present positions of the X axis, the C axis, and the H axis, wherein;
• the imaginary-Y-axis control unit includes:
• a separating unit configured to separate, for each block, a command of the machining program created in the program coordinate system into a first movement command and a second movement command, the first movement command including at least one of an X-axis movement command and a Y-axis movement command, the second movement command including at least one of an H-axis independent movement command and a C-axis independent movement command;
• a coordinate converting unit configured to convert the first movement command into a command of the machine coordinate system including the X-H-C axes;
• a combining unit configured to combine the converted H-axis movement command and the separated H-axis independent movement command and combine the converted C-axis movement command and the separated C-axis independent movement command;
• and
• a driving unit configured to control to drive the X axis, the H axis, and the C axis according to the converted X-axis movement command and the combined H-axis movement command and C-axis movement command,
• the numerical control apparatus further comprises a first storing unit configured to store a movement amount by the second movement command before the emergency stop, and
• the restoring unit separates a position equivalent to a movement amount stored in the first storing unit from the acquired present positions of the X axis, the C axis, and the H axis, performs conversion in a direction opposite to a direction of the coordinate conversion by the coordinate converting unit using a result of the separation, and restores the present X-axis coordinate position and the present Y-axis coordinate position in the program coordinate system.