Yes, the Geometry > Surface > NonManifold Add command can be used to solve a geometrical interference in FEMAP, I use this "trick" a lot when receiving CAD Assemblies models where interferences "by error" between geometrical parts is quite common. The workflow is explained here:
1.- The following picture shows a clear interference between two parts (yes, it is a simply CAD assembly, but is valid for complex geometries as well):
2.- Issue command "Geometry > Surface > Nonmanifold Add" and select the bodies where you want to solve the geometrical interference. Please use a reasonable tolerance: is not the same to add bodies of 25 meters long than parts of a few millimeters, "play" with the tolerance if necessary. Also please note that now you have a single body named "General Body Add": the icon is different that a regular 3-D solid or a regular 2-D surface, have you noted it before?.
3.- The trick comes now: use command "Geometry > Surface > Recover Manifold Geometry", and the result will be three bodies!!. The command will take the selected “general bodies” in your model and separate them into individual component “Manifold” Parasolid solids (FEMAP solids) or sheet solids (FEMAP Surfaces).
4.- Once the “Manifold” solids and sheet solids have been recovered, the commands on the Geometry, Solid... menu will be available to modify and operate on the geometry again: for instance, you can use "Geometry > Solid > Add" command to join the correct solids as desired to solve the interference .., OK?.
Enjoy!. Best regards, Blas.
Blas Molero Hidalgo, Ingeniero Industrial, Director IBERISA • 48004 BILBAO (SPAIN) WEB: http://www.iberisa.com Blog Femap-NX Nastran: http://iberisa.wordpress.com/