In layered manufacturing (LM), 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 process-planning step in LM is choosing a suitable 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. We describe a robust, exact, and efficient implementation of an algorithm that computes a description of a subset of all build directions for which a prescribed facet is not in contact with supports. We also present test results on models obtained from industry, and on collections of random triangles.
Bibliographical noteFunding Information:
We thank Larry Roscoe, Don Holzwarth, Jon Holt, Jeff Kotula, and Tom Studanski of Stratasys, Inc. for useful discussions. In particular, they proposed Problem 1 to us. We also thank them for allowing us to test our implementation on their polyhedral models. This work was funded in part by a joint research grant by DAAD and by NSF. This work was done while J.S. and M.S. were at the Fakultät für Informatik, University of Magdeburg, Germany. Part of this work was done while J.S. and M.S. visited the University of Minnesota in Minneapolis, and while R.J. visited the University of Magdeburg. Research also supported in part by NSF grant CCR-9712226.
Copyright 2004 Elsevier Science B.V., Amsterdam. All rights reserved.
- Computational geometry
- Layered manufacturing
- Spherical geometry
- Union of convex polygons