I render photorealistic stuff out of my AutoCAD models.

The DWG you saw previously is the part to the right.

You might wonder why I bother with this question if the surfaces are going to end up in 3dsMax anyway where I could flip the normals. But yet, I want to model a fault free model in AutoCAD so that I won't need to do extra adjustments afterwards in 3dsMax...

You can render anyway with simple colors even  if you don't affect a material to your solids.

If you affect a material it can be smarter...

Planar surface can be exploded and output lines. A surface can be built from them with SURFNETWORK.

After exploding the rounded corner, it can be rebuild with Loft with Guide Curves.

If we wanted a command similar to Rhinos FLIP, I think it has to be programmed in .NET or similar.

I didn't manage to explode to a 3D face, it rather turned into something else.

Please have a look at this DWG

https://www.dropbox.com/s/kv50hyq08zi0ayi/Surfaces.dwg?dl=0

(I don't know how to attach - if someone would please tell me how, I can attach the file here for future reference)

Colors:

Green: Regular surfaces.

Yellow: When I exploded the surfaces, they turned into regions, not 3d faces.

Red: The problematic surfaces, ie need their faces to be flipped. I can see that the faces are flipped when I export this to 3dsMax.

See if it works for you and thank you in advance.

Thanks. We don't have Inventor at the office just now, but maybe at some point. If it opens and saves DWG natively, this would be a acceptable detour to fix and then save and continue in AutoCAD. Otherwise, I could as well use 3dsMax to fix the normals, and re-export.

But I'll wait to hear if someone hopefully knows an AutoCAD way for solids/surfaces similar to the first suggestion that was for 3d faces.