Pin,
If you want to create beam elements, then an IGES wireframe is what you want to use! You do not want to import a solid model if you want beam elements. A beam element is just a straight line at the centroid of the cross section. So, the CAD drawing should be a helix of one line. (If you can split the helix into smaller straight-line segments in the CAD, that will make it easier.)
After setting the "Files of type" on the Open dialog, click the "Options..." button before choosing the filename. On the IGES Wireframe import options, make sure "Import as 2-D objects" is not checked. Then choose the filename.
FYI: You should be able to import IGES files that contain a solid model. Under "Files of type", you should see entries for "IGES" and "Wireframe IGES". The first one is for the solid models.
John Holtz, P.E. Global Product Support
Autodesk, Inc. If not provided already, be sure to indicate the version of Inventor Nastran you are using!"The knowledge you seek is at knowledge.autodesk.com" - Confucius 😉
