DWG 2d export always makes everything out of lines, including arcs/circles/curves. To get true ACAD arcs/circles etc you need to use the 3d export. Then it retains them as arcs/circles/polylines... If you set the 3d export options to include faces in the export you get a polymesh inside a group [you could explode the SKP group before exporting ?] If you set the 3d export to be edges only you will get any edges which you have 'welded' as 'curves' appearing a 'polylines' in the CAD file. You could also thick about 'welding' the whole perimeter of the face into one curve - which would then export as a single polyline ? See the attached examples... Fräskontur Tischplatte-PolyMesh.dxf Fräskontur Tischplatte-PolyLines.dxf

To reiterate the previous two posts... You could probably make that with far fewer facets without losing anything in the appearance. Your faulty object is probably quite small... There is a well know limitation in SketchUp... SketchUp cannot create very tiny faces. Its tolerance is ~1/1000th" - so if you have a small facet with one or more very short edges it will assume that the start and end points of the tiny edges are coincident and so it will not add the edge. Consequently the face[s] relying on each tiny unmade edge will not get created either. Scale up your object x100 [or more], perform the operation and there should now be no overly small edges, so the facets will be made as hoped. Scale down x0.01, the then tiny facets will be kept because although small edges cannot be made they can exist ! You need to be aware of the size limitation and scaling 'trick' when using several native operations - like FollowMe - and any Plugins which do operations which could give tiny geometry in their outputs. Humongous geometry can also have similar issues, but that is rarer