When using the export to dwg function in Sketchup Pro, all objects in the Autocad file will become block references. The block references can be exploded in Autocad, but will end up in faces or lines, not usable to edit. In the following way it is possible to convert a Sketchup drawing to a dwg with solids (even without SketchupPro):
- Explode all components to it's sub-components.
- Make the model as clean as possible. Use for example the Solid Inspector 2 plug-in to clear duplicate lines or to restore other errors in the components.
- Make all components closed.
- Save the drawing in skp version 7 format.
- Import the version 7 skp file using the Import Skp plugin
- You will now have one big block reference.
- Explode this. There is now a collection of block references for each object.
- Select all and explode. You will now have block references (of objects that had an error in Sketchup), and meshes (of objects ready to convert).
- Select a mesh, right-click and choose 'select similar'.
- All meshes are now selected.
- Type CONVTOSOLID.
- (Set the system variable SMOOTHMESHCONVERT to 2 first)
- Convertable meshes are now a solid. Select a solid, choose 'select similar' and hide all solids.
- Select all. What's now left is, 1) unexplodable block references (in Sketchup components with sub-components) and 2) unconvertable meshes (components in Sketchup with an error). Repair the errors in Sketchup or re-draw them in Autocad, depending on what's easier.