Numerical control apparatus

A numerical control apparatus installed in a machine tool which includes:

• a plurality of transfer devices which transfer a movement target object, which is a workpiece or a tool to process the workpiece, when the workpiece is processed;
• and a special command input device for inputting, from outside, a special command for instructing an operation involving a velocity change of the movement target object separately from normal transfer of the movement target object performed when the workpiece is processed, each of the transfer devices including a support for supporting the movement target object, and a driving device which transfers the movement target object by transferring the support in a predetermined movement axis direction, the numerical control apparatus performing numerical control of each of the transfer devices and comprising:
• a storage unit which stores a processing command program which specifies a processing path to indicate a path where the movement target object is to move as a reference time elapses when the workpiece is processed;
• a computing unit which calculates, on the basis of the processing path, a moving distance of each support in the corresponding movement axis direction per set unit time;
• and
• a drive control unit which causes each driving device to transfer the support corresponding to that driving device in accordance with the moving distance of each support calculated by the computing unit, wherein
• in response to the input of the special command to the special command input device, the computing unit changes a length of the set unit time from a length in the state immediately before the input of the special command to a length corresponding to the velocity change of the movement target object instructed by the special command, and calculates, on the basis of the processing path, the moving distance of each support in the corresponding movement axis direction per set unit time of which length has been changed.