Author Topic: Notes on DesignCAD 25's STL export feature  (Read 983 times)


  • Kindly Curmudgeon
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Notes on DesignCAD 25's STL export feature
« on: July 29, 2015, 10:32:56 AM »
As you know, DesignCAD 3D Max 25 now offers the ability to export objects as STL files. While this is definitely progress, the results may not always be perfect, and your 3D printer software may balk at what you've just exported. Here are some possible reasons and workarounds:

1) Facet normals may not all point in consistent directions. This is usually visually indicated in your 3D Printer or Slicer software as facets of a different color. Some slicers will go ahead and work with the flipped facets, but others may refuse. Fortunately, most such programs contain an analysis tool that can detect such problems and fix them automatically. Look for tools like "Analysis" or "Repair" or "Fix Normals".

2) Object is not "manifold", i.e. it's not a completely closed surface with no extraneous interior geometry. Unfortunately, these kinds of objects are easy to create with DesignCAD if you're not careful. For example, extruding two adjacent planes that share one edge, then defining the entire result as a single solid, results in two interior facets where the two adjacent edges got extruded. About the best you can do in this case is explode the solid, find the unnecessary facets, and remove them manually, then re-define the solid. For such a simple case as this, rather than declaring both solids to be one, activate the "use surface representation for solid operations" setting in General Options, then add the two solids together. The Solid Surface result will not include the redundant planes. (Sometimes this trick will work even if you don't activate "use surface representation" first.)

3) Exporting files as DXF, then using another tool to convert the DXF to STL. DesignCAD's "classic" solids may contain facets that are too complex for 3D printing and slicing software to handle. If these programs encounter a facet that is more complex than a triangle or a convex "quad", they may simply omit the offending facet. This will result in holes in your solid. This problem can be mitigated by first converting the "classic" solid to a solid surface, then when exporting to DXF select the "Triangulate Solid Surfaces" export option.

4) Sloppy Geometry. DesignCAD lets you define ANYTHING as a solid -- it doesn't have to be a closed surface, and the points don't have to meet up. When you export such sloppy geometry to STL format, DesignCAD will simply take your word for it that "yes this is really a solid" and output the geometry as is. There is no automatic cleanup or annealing function to heal stuff with holes in it. You can try re-importing the STL output, and check for holes using shading or hidden line removal.
« Last Edit: June 30, 2016, 08:23:46 AM by DrollTroll »
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