Dxf does not support 3D. You can use the satout command to output the 3D drawing of cad to sat format. In proe, select the menu "Insert-* * Appreciate Data-From File ..." and select ACIS file (*. SAT), find the sat file just output, just open it. ? After AutoCAD2008 version 2008, you can choose File-Output and save it as a file in sat format.