Converting assembly to solid part body?

Hi,

Does anyone know how to create a single, airtight solid body from an assembly that preserves the exterior details while removing the interior details? This is what the old Simplify Assembly command did in NX8,5. unfortunately it is not longer available in my NX11.

Probably it is a whole job to do it manualy. So I already would be happy if I could just convert the assembly to one solid body file.

Thanks for the prompt reply.

Rollin.