Hello,to use AutoCAD 3D models in animatins I'd like to export them to Blender. The usual way seems to be to import the files in Sketch Up Pro and to export them from there to whaterver Blender can read.I'm still using a AutoCAD demo version and will be using the student version afterwards. Sketch Up Pro 7 can't read the files. What might be wrong?? Or any better ways to do that?Error message from Sketch UP:"Error opening AutoCAD import file: Unknown ErrorThis does not appear to be a valid AutoCAD DWG or DXF fileor the file is write protected"The file is definitely not write protected

It does not matter that you are using a trial version of AutoCAD and it won't matter in the future if you are using the student version either.  What will matter is whether or not SketchUp Pro 7 can import (or open directly) drawing (DWG) files created in the 2013 file format.  If it can't then you would first have to do a "saveas" in AutoCAD to an earlier file format like 2010 or possibly even 2007. 

Thank you! But I already tried to save it to earlier formats.Maybe the problem is about the object not being a solid. I created a new topic on that.

The error message has nothing to do with the type of object you are trying to import.

For solids the command STLOUT should create an STL file which Blender can import

True. I tried the 2004 version format an it worked. Unfortunately it exported only the wireframe, not the surfaces. But at least..