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.