Sufficient conditions for draft angles on general B-spline surfaces

Many manufacturing processes, e.g. casting, forging, moulding, require that components must have a sufficient draft angle. Ensuring this when using general B-spline surfaces is a difficult task, often requiring iterative modeling. In this paper a theorem is presented that provides sufficient conditions to ensure draft angle on B-spline surfaces. The theorem is used to develop a simple algorithm that was used to add a draft angle to two surfaces.     

A note on two-sided holes in implicit quadric spline surfaces

Some implicit spline surface schemes require filling two-sided holes [Dahmen 1989; Guo 1993] and a blending technique of Warren (1987) can be used to fill two-sided holes in quadric spline surfaces. This note shows that there are important cases where the blending technique does not apply. These cases are identified and an applicatble technique is proposed.