Has anybody experimented with GMAW for additive manufacturing? The thing is, welding wire is so much cheaper than ABS or PLA filaments and, well, it is steel you are printing in, not some flimsy plastic! I imagine the arc deposition printhead would be constructed similarly to one used in plastic filament printers, except there is no need for the heating element (so, even simpler). Welding often requires fast Z speed (to finely control the arc) so i think Delta (DeltaMaker) chassis would work best. GMAW calls for some sort of inert gas to insulate heated metal from oxygen. It would make sense to seal off most of the interior of the printer and fill it with heavier than air inert gas during printing.
I would highly appreciate any pointers on existing 3d printer designs employing this deposition method as well as flaws in design i outlined here.