Edges and Ridges

I want to create a solid as combination of 3 or more shells, save it to IGES so that when I give to NetGen or some other meshing program it will keep the shell boundaries but mesh everything inside no matter how many faces it has or what so ever.
I've been testing with a simple cube put together from 6 shells(each side) and then I export it as IGES and everything is perfect. But the moment I i create one of the shells from not one but two faces(two halves of one side) NetGen meshes without crossing the the edge in the middle of the side.
Is there a way to mark edges as, for the lack of better word, 'free' and others as ridge.
Thank you in advance,

daon's picture

That's the cube..