brl-cad is a solid modeling tool (like Catia, pro-engineer, etc.) but open source and has conversion engines to and from the application.

The URL to the homepage is:
http://www.brlcad.org/

True, its origins are a bit doubtful but it seems to hold well in a Linux environment and it is full of potential.

Questions, obviously, remain among which:

Q: why is the IGES file conversion so patchy (not a single success yet) and is it user error?

Q: is there a tool to morph one 2D shape into an other?

Q: is there a convenient scripting tool that will allows the conversion of arbitrary solids into models that brl-cad can understand? tlc/tk is already heavily supported but is there example code available?

Q: IGES is a good but somewhat unstable format so what is the experience with sending these models converted to IGES to be produced?

Q: I have tried the dxf conversion into qcad without success.  What am I doing wrong?