Numerical control device, method of controlling the same, and system program therefor

A non-transitory computer readable medium storing a system program to be executed by a central processing unit of a numerical control device which machines, based on the system program, a workpiece fixed to a table using a machine tool having a plurality of linear movement axes and at least one rotational movement axis for turning a table, the system program comprising:

• an interpolation-command reading step of reading an interpolation command included in a machining program;
• a coordinate-system transformation command determination step of determining whether a coordinate-system transformation command, for transforming the interpolation command from an interpolation command in a non-machine coordinate system into an interpolation command in a machine coordinate system, is attached to the interpolation command read in the interpolation-command reading step;
• a first interpolation step of obtaining, in response to determining in the coordinate-system transformation command determination step that the coordinate-system transformation command is not attached to the read-in interpolation command, a first movement amount corresponding to each of the movement axes in accordance with the interpolation command;
• a second interpolation step of transforming, in response to determining in the coordinate-system transformation command determination step that the coordinate-system transformation command is attached to the read-in interpolation command, the read-in interpolation command into an interpolation command in the machine coordinate system, to obtain a second movement amount corresponding to each of the movement axes in accordance with the transformed interpolation command;
• and
• a driving step of driving a servo motor corresponding to each of the movement axes based on the first movement amount or the second movement amount,
• wherein the second interpolation step transforms a start-point coordinate and an end-point coordinate in the non-machine coordinate system included in the read-in interpolation command, to which the coordinate-system transformation command is attached, into a start-point coordinate and an end-point coordinate in the machine coordinate system, respectively.