[EricH]

Originally Posted by Arch3Dpt

Could an arch-welder head be used as on a 3D printer?

Could it? Probably.

Is it going to be useful? Possibly--most 3D printers that could be modified for an arc welder tip are under a foot of travel in any direction, which may or may not affect usability (though it'll certainly affect size of parts that can be welded). Also I can't think of anything that would need that much precision (we're talking in thou here) in terms of arc welding. Might want to try a CNC router modification first.

Is it a good idea? No. There's a lot of stuff that could go wrong, ranging from melting plastic (reprap-type machines) to warping the print surface (VERY bad if you ever want to change back) to any other safety concerns with exposed welding.

As stinglikeabee pointed out, you're pretty close to sintering, but those types of 3D printers are a minimum of 6 figures, not counting material cost--and in some cases, shielding.