A new computational method for MAT of injected parts integrated in part modelling stage

Abstract

In this paper we present a simple and fast approach for MAT generation in discrete form. It is used for manufacturability analysis in the part modelling stage of injected parts. The method is a volume thinning method based on straight skeleton computation, modified and applied in 3D on B-rep models in STL. The volume thinning of the B-rep model is based on its boundary surfaces offset towards the model interior. The surfaces’ offset is done with an adequately proposed offset distance which makes some of the non adjacent offset model surfaces overlap (they ‘meet’ in mid-surface or MAT). Offset surfaces are used to reconstruct the topology of a new B-rep model (offset model). Overlapping surfaces in the offset model are detected, separated and aggregated to MAT. For adequate MAT precision and adequate MAT radius function, we propose to treat B-rep model concave edges (vertices) as cylinders (spheres) of zero-radius and offset them in an adequate way. On these bases, we present an iterative algorithm in which MAT is constructed in an incremental way by consecutive volume thinning of the obtained offset models. MAT construction is finished when an empty offset model is obtained. An algorithm has been created and implemented in Visual C++. Some of the obtained results are presented in this paper.