Protecting critical facets in layered manufacturing

Abstract In layered manufacturing, a three-dimensional polyhedral object is built by slicing its (virtual) CAD model, and manufacturing 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 maximum. A simplified version of the first algorithm has been implemented, and test results on models obtained from industry are given.

[1]  Prosenjit Bose,et al.  Feasibility of Design in Stereolithography , 1997, Algorithmica.

[2]  Michiel H. M. Smid,et al.  On some geometric optimization problems in layered manufacturing , 1999, Comput. Geom..

[3]  Paul F. Jacobs,et al.  Rapid Prototyping & Manufacturing: Fundamentals of Stereolithography , 1992 .

[4]  Kevin W. Bowyer,et al.  Aspect graphs: An introduction and survey of recent results , 1990, Int. J. Imaging Syst. Technol..

[5]  Michiel H. M. Smid,et al.  Computing the width of a three-dimensional point set: an experimental study , 1999, JEAL.

[6]  Kurt Mehlhorn,et al.  LEDA: a platform for combinatorial and geometric computing , 1997, CACM.

[7]  H. S. M. Coxeter,et al.  Vorlesungen über die Theorie der Polyeder , 1935 .

[8]  Michiel H. M. Smid,et al.  Multi-criteria geometric optimization problems in layered manufacturing , 1998, SCG '98.

[9]  Leonidas J. Guibas,et al.  Walking on an arrangement topologically , 1991, SCG '91.

[10]  T. C. Woo,et al.  Computational Geometry on the Sphere With Application to Automated Machining , 1992 .

[11]  Michiel H. M. Smid,et al.  Minimizing support structures and trapped area in two-dimensional layered manufacturing , 1999, Comput. Geom..

[12]  Jörg-Rüdiger Sack,et al.  Separating a Polyhedron by One Translation from a Set of Obstacles (Extended Abstract) , 1988, WG.

[13]  Lutz Kettner,et al.  Using generic programming for designing a data structure for polyhedral surfaces , 1999, Comput. Geom..