Convert AutoCAD DWG to STL: what works and what does not
DWG holds anything: plans, sheets, solids. Only part of that has volume to become STL.
DWG is AutoCAD's format, and DXF is its open counterpart, exported by nearly every CAD. Both hold anything: a house plan, a sheet for laser cutting, a 3D solid. Only part of that becomes STL, and it helps to know which before trying.
What converts
- Meshes (MESH and polyface): straight to STL.
- 3D faces (3DFACE): each becomes one or two triangles.
- Flat-faced solids (3DSOLID made of boxes, wedges, straight extrusions): the converter reads the geometry and tessellates it.
- The drawing unit (mm, cm, m, inch) is read from the file and converted to millimetres.
What is refused, and why
- 2D drawings. Plans, sections, laser-cut sheets: lines on a plane, no volume. There is no STL of something with no thickness. For sheet parts, extrude in the CAD and export.
- Solids with curved surfaces. A 3DSOLID with a round hole, chamfer or fillet is stored in a proprietary format (ACIS) that no free tool can read. Neither our converter nor the other free online ones; those that do pay for an SDK licence.
In both cases the screen tells you right away, instead of handing over an empty or distorted STL.
The shortest path: inside AutoCAD
If you have AutoCAD, the STLOUT command exports any solid, curved or not, straight to STL. For STEP, STEPOUT. Both come out in the right unit. The online converter is for when you received the DWG and do not have the program.
Step by step in the converter
- Open the DWG to STL converter and drop the file.
- If the DWG has curved solids, part of it is left out and the screen says how many. The part may be incomplete: check the preview.
- Check the dimensions in millimetres and download the STL.
DXF from SketchUp or Revit follows the same rule. If the source program exports STL or STEP, prefer that: it is more faithful than going through DXF.
