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CAD to STL: Get Quality Parts Everytime

If you've ever ordered a prototype or production part online, your part may have looked different than you expected. Why? Because sometimes data is lost when you convert your file from CAD to STL. Since nearly every rapid prototyping and digital manufacturing (end-use parts) organization uses STL files to build parts, it is important to understand what STL is and what settings you can adjust to get the part you really want.

The .STL file format has turned into the Rapid Prototyping industry's standard data transmission format. This format approximates the surfaces of a solid model with triangles. For a simple model, such as the box shown in figure 1, its surfaces can be approximated with twelve triangles, two on each side, as shown in figure 2. The more complex the surface, the more triangles produced as shown in figure 3.

Almost all of today's CAD systems are capable of producing an STL file. For the user, the process is often as simple as selecting File, Save As and STL. Below are steps for producing high quality STL files from a number of today's leading CAD systems.

General Steps

Most CAD packages will have a couple of options that affect the quality of the STL.
  • Changing a "Deviation" type of value will alter the overall output or tessellation.
  • Changing an "Angle Tolerance" type of value will alter smaller details in your file.
The tighter these parameters, the more triangles placed on the surface of the model.
  • Simple geometries tend to be a few hundred kilobytes in size.
  • Complex models will range from 1-5MB in size and still produce good parts.
  • For many models, files larger then 5MB may be unnecessary and often result in more time to get your quote and models back.
In all cases, export your STL file as a binary file. This saves on time and file size. Please note, these are general guidelines and may not work or in some cases, produce the best possible STL file. Please consult your user's guide or the software developer's for more information or technical support. Should we determine that your STL file is not adequate for production, we will contact you for an updated file.

Download The Complete CAD-to-STL Guide