An approximate method for generating draft on a free-form surface

When a CAD system is used to design a model manufactured by die casting, in jection mould or another method, and the finished product is drawn out of a mould, it may be necessary to give the model draft. This paper presents a method for generating the draft on a free-form surface. An isocline curve a nd an isocline surface are first defined, then generated approximately. The approximate isocline surface, which becomes the draft on the free-form sur face, is a ruled surface with a nonrational B-spline form.