Re: We need one of these on the ISS
I've seen a number of these work in CAD conferences. The main limitation is the materials available, although they're working constantly on that. A little crescent wrench was one of the demos.
The machine I saw had the regular structural material, and a special filler material that was used to hold loose parts in place during the process, and could be dissolved easily later.
They used a thin thread of material that was "printed" in layers. The one in this system seems to use something that fixes specific parts of a powder matrix.