27.4. How Does Rapid Prototyping Work?

Regardless of the specific machine/process, the basic steps used for rapid prototyping are the same:

  1. A surface or solid model CAD file must be generated.

    • Generally, solid model programs such as Pro Engineer® and Solid Works® create a better STL file than a surface modeler. The term "water tight" refers to how close surfaces are joined in a surface CAD program. This can be a source of problems when working with rapid prototyping. If you are working with a surface modeler CAD program, you should increase the system default tolerance to 6—8 decimal places and establish good drawing practices. Some CAD designers take surface shortcuts that may seem like time-saving decisions at the moment, but create problems after the file gets more complicated and moves into rapid prototyping.

    • When working with an assembly of parts, rapid prototyping gives the user the option to create them as one part or as individual parts. Some RP machines can make parts with various colors to highlight and differentiate features.

  2. This file must be saved as an STL file. This is a conversion option in the CAD program and usually requires nothing more than following the "Save As" command.

    • The STL file was first created for the stereolithography rapid prototyping process but has been adopted as the standard for present day RP files.

    • The output STL file is a series of triangles or facets. The size of these facets can be controlled by settings during the conversion process. The settings ...

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