Hierarchical slice contours for layered-manufacturing

This paper proposes a contour-processing system to enhance the capability and efficiency of fabricating complex objects in layered manufacturing (LM). It consists of a tolerant slicing algorithm and a topological hierarchy-sorting algorithm. The tolerant slicing algorithm aims to overcome the constraints of computer memory and the computation instability commonly inherent in conventional slicing methodologies, while the topological hierarchy-sorting algorithm constructs the topological relationship of complex slice contours. The tolerant slicing algorithm adopts a simple pick-and-drop approach to minimise the memory usage. It extracts one facet at a time for slicing. Hence, complex and large STL models of virtually unlimited file size can be sliced effectively. The algorithm is relatively fault tolerant in that inconsistent contours due to defects of the STL file may be automatically repaired. The topological hierarchy-sorting algorithm constructs the hierarchy relationship of complex slice contours, with which virtual prototyping and surface reconstruction algorithms can be conveniently applied. In particular, slice contours with established hierarchy relationship facilitate collision detection in multi-material assemblies, as well as the optimisation of laser/binder path in LM by avoiding redundant back-and-forth movement. (C) 2002 Elsevier Science B.V. All rights reserved.