Create surfaces from AutoCAD solids
Solid objects need to be transformed into surface meshes for import into RadTherm.
Step 1: Use AutoCAD’s 3dsout command to create and export surfaces of solid objects.
Step 2: Select all objects you wish to export. Parts assigned to a single layer in AutoCAD will be imported a single part in RadTherm. RadTherm’s editor can reassign elements to new parts if desired, but layering is the easiest way to organize parts for analysis in RadTherm.
Step 3: Assign a filename to the 3DS file.
Step 4: Create a new AutoCAD drawing into which you will re-import the saved 3DS surface file.

Create surfaces from AutoCAD solids
Solid objects need to be transformed into surface meshes for import into RadTherm.
Step 5: Use the 3dsin command to import the 3DS surfaces back into AutoCAD. Select the file you exported in Step 4.
Step 6: Select the surfaces from the import dialog you wish to import. To import all objects, click “Add All”.
Step 7: Objects can be split by materials, if desired. For Most users, the default settings are correct. Click “OK”.

Explode and save in DXF format
Step 8: Use the explode command (this makes the 3DS surfaces 3D FACES).
Step 9: Type all to explode all surfaces.
Step 10: Use the dxfout command or the Save as command to create the dxf file (any dxf version is OK).
Step 11: Assign a filename to the dxf file. This file will be imported into RadTherm. After import, it is not needed. AutoCAD can now be closed.

Start RadTherm and open or import file
Step 12: Launch RadTherm. You can open the file directly by selecting File->Open. In this case your thermal model will consist only of the geometry from AutoCAD. If you wish to ADD this geometry to an existing thermal model, choose the File->Import command. If you import new geometry, you will be prompted to append or replace any existing geometry. 
Step 13: At the bottom of the open dialog box, select the filetype AutoCAD DXF, and locate the dxf file.
Step 14: Choose the proper units for this geometry.
Step 15: The geometry is now loaded. You can use RadTherm’s tools in the Geometry tab to manipulate the geometry as needed. You are now ready to use the Editor tab to assign thicknesses, material properties, and surface conditions to the components.

About mesh quality
The standard meshes created by AutoCAD tend to consist of high aspect ratio triangles. This type of mesh generally yields poor results in analytical models. There are several ways to improve the quality of your mesh. RadTherm 7.0 (not yet released) will include a remeshing tool capable of creating very high quality meshes. 3rd party tools can be used to create good quality meshes from geometry originating in AutoCAD. For more information on meshing, visit our meshing pages.