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Proceedings of CAD'17, 2017, 5-9
Slicing Point Clouds for 3-D Printing

William Oropallo, Les A. Piegl, Paul Rosen, University of South Florida
Khairan Rajab, Najran University

Abstract. Due to the complexity and the instability of numerical methods, the common practice of slicing has been to decompose the free-form object, designed with NURBS [4], into simple facets (triangles) and slice the faceted (STL) model. This seems like a doable approach, however, decades of experience has shown that this approach, while avoids complex mathematical issues, creates its own numerical problems. To begin with, tessellating a complex NURBS model is a difficult task and the authors have yet to see a robust tessellator. But never mind the tessellator, the fundamental problem flies in the face of CAD companies that work collaboratively, yet their systems are largely incompatible. When the part travels down the design pipeline, it is converted from one data format to the other. By the time it reaches the printer, it suffers from gaps, overlapping surfaces, dangling edges, just to name a few. Put a tessellator to it and slice it, and you have a disaster. This paper argues that it is time to ditch everything that is complex, error prone and inaccurate, and organize the rest into a simple system that is easy to maintain. In this research we eliminated the STL conversion and all error–prone numerical algorithms, and converted the NURBS object to the simplest entity: a set of points. The slicing is done on the point cloud model employing practically no numerical procedure.

Keywords. 3-D printing, NURBS, Point cloud, Object slicing

DOI: 10.14733/cadconfP.2017.5-9