Protecting Facets in Layered Manufacturing

Abstract

In Layered Manufacturing, a three-dimensional polyhedral object is built by slicing its (virutal) CAD model, and maufacturing the slices successively. During this process, support structures are used to prop up overhangs. An important issue is choosing the build direction, as it affects, among other things, the location of support structures on the part, which in turn impacts process speed and part finish. Algorithms are given here that (i) compute a description of all build directions for which a prescribed facet is not in contact with supports, and (ii) compute a description of all build directions for which the total area of all facets that are not in contact with supports is minimum. The first algorithm is worst-case optimal. A simplified version of the first algorithm has been implemented, and test results on models obtained from industry are given.