Thank you Rob, on the other hand, when I import AutoCad files to Spaceclaim, lines are properly transfered whereas surfaces and bodies are transfered but in a small scale.

Normally they are transfered in inches whilst I work in meters (I use meters also in AutoCad).

Default units in AutoCad and Spaceclaim are both in meters, just when I import the file it turns to inches. Let's say I have a surface of 70mx11m in Autocad. Then when I import it becomes 70inx11in.