Method of creating NC data for machining curved surfaces

A method of automatically creating NC data in an NC data creating apparatus and machining a curved surface, comprising:

• a first step of inputting data specifying a first three-dimensional surface and data specifying a second three-dimensional surface that defines a cutting boundary in a depth direction of said first three-dimensional surface;
• a second step of generating a first plurality of point-sequence paths defining said first three-dimensional surface and generating a second plurality of point-sequence paths that define said second three-dimensional surface;
• a third step of determining a tool nose point sequence corresponding to a point sequence on said first curved surface based on said first plurality of point-sequence paths;
• a fourth step of determining a projected point sequence obtained by projecting said tool nose point sequence onto a reference plane, and determining a projected point sequence on said second curved surface obtained by projecting said first-mentioned point sequence onto said second curved surface;
• a fifth step of checking if a line segment connecting the tool nose point sequence and a line segment connecting the projected point sequence on said second curved surface intersect and if they do intersect, determining a point of intersection P(i,j);
• a sixth step of creating NC data up to a point of said intersection P(i,j) if the line segments intersect;
• and
• a seventh step of subsequently machining a curved surface by performing a pick-feed using the NC data.