A Method to Generate Exact Contour Files for Solid Freeform Fabrication

Existing methods to create contour files generate a polygonal approximation of the contours instead of an exact representation. This paper presents a method to generate exact contours from Constructive Solid Geometry (CSG) representations. The method preserves the accuracy of the contour files provided the primitives used to generate the CSG tree are polygonal or quadric objects. Due to the inclusion of quadric objects into the primitive set an additional effort to solve for the intersection points between two quadric curves is required. The paper also presents a method to convert piecewise quadratic contours to toggle point files for raster scanning solid freeform fabrication processes.Mechanical Engineerin

Direct Generation of Contour Files from Constructive Solid Geometry Representations

Geometry processing for layer-based Solid Freeform Fabrication consists of at least two steps: slicing the geometry to obtain the part contours for each layer, and scan-converting the layers for laser scanning (or other device-dependent in-layer processing). This paper discusses the generation of contour files directly from Constructive Solid Geometry (CSG) representations for the Selective Laser Sintering process. Previous work at The University of Texas focused on slicing CSG representations composed of quadric primitives. This paper extends previous work at UT to include the torus, a fourth degree surface, as one of the CSG primitives. Slicing a torus results in a fourth degree equation in two variables, which represents a curve in two-dimensional real space. For. some special cases, this fourth degree equation may be sub-divided into two second degree equations. For the cases where the fourth degree equation cannot be sub-divided, a method is presented to approximate the fourth degree curve with second degree curve segments.Mechanical Engineerin

Preliminary Experience with Selective Laser Sintigrapbic (SLS) Models of the Human Temporal Bone

To assess the accuracy of three-dimensional models of the human temporal bone generated from computed tomographic (CT) data.Mechanical Engineerin