Taking Advantage of Stereolithography

ACAD only A discussion of solid modeling wouldn't be complete without mentioning stereolithography. This is one of the more interesting technological wonders that have appeared as a by-product of 3D computer modeling. Stereolithography is a process that generates resin reproductions of 3D computer solid models. It offers the mechanical designer a method for rapidly prototyping designs directly from AutoCAD drawings. The process requires special equipment that will read computer files in a particular format.

AutoCAD supports stereolithography through the Stlout command. This command generates an .stl file, which can be used with a Stereolithograph Apparatus ( STA ) to generate a model. You must first create a 3D solid model in AutoCAD; then you can proceed with the following steps to create the.stl file:

Choose File Export to open the Export Data dialog box.
In the Save As Type drop-down list, select Lithography (*.stl). Click the Save button.

Tip
You can also type Stlout at the command prompt to bypass steps 1 and 2.
At the Select a single solid for STL output: prompt, select a solid and press . The solid must reside in the positive X, Y, and Z coordinates of the World Coordinate System. Also note that most stereolithography apparatus cannot produce undercuts such as the hole of a donut shape when the donut is oriented vertically.

The AutoCAD 3D solids are translated into a set of triangular - faceted meshes in the .stl file. You can use the Facetres system variable to control the fineness of these meshes. See Chapter 17 for more information on Facetres.