What is a solids model?

In layman's terms, a solids model is a 3D, watertight geometry comprised of nothing more than a set of triangles. Consider a cube. Six sides. Two triangles per side. Twelve triangles in total. Each triangle has two sides, but no thickness. To be considered a valid, and buildable solids model, each of the twelve triangles must face the right direction, and all of their edges must match up to each other perfectly.

A "bad" solids file. Yellow lines show open edges, and the red triangle indicate that they are facing the wrond direction.If a model that has any of these problems is built, it may not build correctly. The resulting model may contain strange artifacts, skipped layers or missing surfaces or pieces. As you can imagine, spending a little time fixing the model before trying to build it will ultimately save time and money.

Repairing a file like this can be very tedious. You can see how many triangles are required to create this simple geometry. Several tools are available which are geared specifically toward fixing solids files. They often allow for some level of automated fixing, however, as the geometries become more complex, the automated solutions often fall short, leaving us to attack issues triangle by triangle.

When a file is completely fixed, the entire model will appear as one solid color.A "fixed" solids file. This part has been checked inside and out to insure that all triangles and surfaces are facing the correct direction, no edges are open and all ofther issues are resolved. At this point, we can proceed to building the part.