Surface Techniques and Tips

Don LaCourse, eDocHelp
November 17, 2004
reprinted by permission from

The table below lists some of the more common techniques for constructing surface geometry in 3D CAD systems. Please note that this listing is by no means complete. There are many additional advanced surface techniques in use today. Again, our emphasis here is to provide tips for surface construction that can ultimately affect their usage in solid models.

3D CAD Tips

1. Look out for surfaces that have the potential of self intersecting. These include sweeps due to trajectory, revolves due to rotation angle, rules due to curve relationships, and offsets due to curvature.
2. All surface areas have seams (as in a revolve) or boundary curves. When positioned in a resulting solid topology, these seams and boundaries should be located away from other edges or vertices. Vertices or edges should never coexist within system tolerances unless they in fact share common boundaries.
3. Surfaces generated directly from boundary curves such as rules and patched are preferred over surfaces that are excessively trimmed.
4. When possible, always share existing vertices and edges between surfaces.
5. Some techniques such as lofting, meshing, and patching approximate surface curvature between defining boundaries.
6. If possible, when techniques generate new boundaries on surfaces such as with fillets, reconstruct mating surfaces from the new boundaries rather than trimming the existing surfaces.
7. Techniques that generate tangent surface edges are recommended even if they result in a trimmed surface.

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About the Author

Don LaCourse is principal partner of eDocHelp, which provides e-documentation, online help, technical writing and 3D modeling services for the CAD/CAM, manufacturing and other service-oriented industries. eDocHelp recently launched 3DCADTips, a 3D CAD resource site. Don has over 25 years of experience in design and documentation. He gained much of his experience during his 10 years as a tier-one automotive designer with Textron, Inc. He also helped NASA and the European Space Agency (ESA) design and document their joint SpaceLab 1 project that flew on board several of the early space shuttle missions. Don also brings product and injection mold design and documentation experience to eDocHelp. Don had his first book published in 1995 serving as editor-in-chief for the McGraw-Hill publication "Handbook of Solid Modeling," where he contributed, edited and managed over 25 industry-leading authors. He is currently a contributing editor for Cadalyst magazine.

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