Numerical control programming method, apparatus therefor, and program for causing a computer to execute the method

A numerical control programming apparatus that creates a working program for controlling a machine tool with a numerical control apparatus which grasps a material using a chuck of a first main spindle to perform the working of a first step and alternately grasps the material using a chuck of a second main spindle after the working of the first step to perform the working of a second step, the apparatus comprising:

• a storing unit that stores a solid model of a part shape, a solid model of a material shape, a step dividing position of the step, and an overlap amount between the steps;
• a lathe shape forming unit that forms a solid model of a lathe shape on the basis of the solid model of the part shape;
• a lathe sectional shape forming unit that forms a sheet model of a lathe sectional shape on an X-Z plane on the basis of the solid model of the lathe shape;
• a first/second step working sectional shape forming unit that forms a sheet model of the lathe sectional shape of the first step and a sheet model of the lathe sectional shape of the second step on the basis of the sheet model of the lathe sectional shape, the step dividing position, and the overlap amount;
• a first step unwanted shape deleting unit that selects an edge of the step dividing position from the step dividing position and the sheet model of the lathe sectional shape of the first step, obtains a tangential vector from the selected edge and divides and deletes, by the obtained tangential vector, the sheet model not needing to be worked in the overlap part of the lathe sectional shape of the first step from the sheet model of the lathe sectional shape of the first step;
• and
• a second step unwanted shape deleting unit that selects an edge of the step dividing position from the step dividing position and the sheet model of the lathe sectional shape of the second step, obtains a tangential vector from the selected edge and divides and deletes, by the obtained tangential vector, the sheet model not needing to be worked in the overlap part of the lathe sectional shape of the second step from the sheet model of the lathe sectional shape of the second step.