Non-uniform offsetting and hollowing objects by using biarcs fitting for rapid prototyping processes

This paper presents a new method of using non-uniform offsetting and biarcs fitting to hollow out solid objects or thick walls to speed up the part building processes on rapid prototyping (RP) systems. Building a hollowed prototype instead of a solid part can significantly reduce the material consumption and the build time. A rapid prototyped part with constant wall thickness is important for many different applications of rapid prototyping. To provide the correct offset wall thickness, we develop a non-uniform offsetting method and an averaged surface normals method to find the correct offset contours of the stereolithography (STL) models. Detailed algorithms are presented to eliminate self-intersections, loops and irregularities of the offsetting contours. Biarcs fitting is used to generate smooth cross-section boundaries and offset contours for RP processes. Implementation results show that the developed techniques can generate smoothed slicing contours with accuracy for rapid prototyping without suffering from handling the huge number of linear segments of the traditional methods.

[1]  Bahattin Koc,et al.  Adaptive ruled layers approximation of STL models and multiaxis machining applications for rapid prototyping , 2002 .

[2]  B. Su,et al.  Computational geometry: curve and surface modeling , 1989 .

[3]  Sang C. Park,et al.  A pair-wise offset algorithm for 2D point-sequence curve , 1999, Comput. Aided Des..

[4]  B. Choi.  Surface Modeling for Cad/Cam , 1991 .

[5]  K. Tarabanis,et al.  Path planning with offset curves for layered fabrication processes , 1995 .

[6]  Dereck S. Meek,et al.  On surface normal and Gaussian curvature approximations given data sampled from a smooth surface , 2000, Comput. Aided Geom. Des..

[7]  Wayne Tiller,et al.  Offsets of Two-Dimensional Profiles , 1984, IEEE Computer Graphics and Applications.

[8]  S. T. Tan,et al.  Using dexels to make hollow models for rapid prototyping , 1998, Comput. Aided Des..

[9]  K M Yu,et al.  Speeding up Rapid Prototyping by Offset , 1995 .

[10]  Bahattin Koc,et al.  Smoothing STL files by Max‐Fit biarc curves for rapid prototyping , 2000 .

[11]  Debasish Dutta,et al.  Layered manufacturing of surfaces with open contours using localized wall thickening , 2000, Comput. Aided Des..

[12]  K. M. Yu,et al.  Implementation and evaluation of thin-shell rapid prototype , 1998 .

[13]  Dinesh Manocha,et al.  Simplification envelopes , 1996, SIGGRAPH.

[14]  Barry I. Kelman.  A Distributed Workstation Architecture: The Convergent Cluster , 1984, IEEE Computer Graphics and Applications.

[15]  Takashi Maekawa,et al.  An overview of offset curves and surfaces , 1999, Comput. Aided Des..

[16]  Yuan-Shin Lee,et al.  Surface interrogation and machining strip evaluation for 5-axis CNC die and mold machining , 1997 .

[17]  Debasish Dutta,et al.  Region-based adaptive slicing , 1999, Comput. Aided Des..

[18]  Bahattin Koc,et al.  Ellipse-offset approach and inclined zig-zag method for multi-axis roughing of ruled surface pockets , 1998, Comput. Aided Des..

[19]  K. M. Yu,et al.  Octree reinforced thin-shell rapid prototyping , 1997 .

[20]  Bahattin Koc,et al.  Max-fit biarc fitting to STL models for rapid prototyping processes , 2001, SMA '01.