To set offset quantity of a rotary cutting tool in extremely short time in comparison with the case when the calculation of a trigonometric function is performed by using a normal vector of a cutting surface of a machining object.
Pieces of contour data by every layer are individually taken out from model data of a completed product by a slice processing. Three-dimensional data of a ball is sliced with the same pitch as the one of the respective layers along a diameter extended in the vertical direction of the ball (steps S21, S22). Processings to calculate the radius of many tools are performed by every piece of slice data extracted from the three-dimensional data of the ball. A current layer is determined, a lower point of the tool is defined as being present on a position corresponding to the current layer (steps S23, S24) and pieces of tool radius data corresponding to the respective layers are extracted for all the remaining layers respectively. Pieces of the slice data of the respective layers are quantitatively offset by using pieces of the tool radius data corresponding to the respective layers. OR data obtained by performing an OR arithmetic processing for all pieces of the slice data of the respective quantitatively offset layers is defined as quantitative offset data of the current layer (steps S25, S26, S27).
HIGUCHI AKIRA
KOGA DAISUKE
NAKAJIMA HIROSHI
