[freeandfreezing]

Its a long way from a CNC Tig welder to a machine which can generate sizable 3D structures of steel or titanium which have similar grain structure and strength to structures made using traditional techniques.

There isn't a revolutionary benefit to being able to 3D print in steel if the resulting part has the strength of aluminum, or plastic.

However making a good robot Tig welder does seem like a worthwhile project...

[cripplecreek]

This is a couple years old but revolutionary technology none the less. Made even more impressive due to the fact that the inventor is a self taught metallurgist.

a heat-treatment that makes steel 7 percent stronger than any steel on record — in less than 10 seconds.

http://www.sciencedaily.com/releases/2011/06/110609173718.htm

[Talisker]

There isn't a revolutionary benefit to being able to 3D print in steel if the resulting part has the strength of aluminum, or plastic.

Heating and cooling within directed magnetic fields can remove stress and align grain. I wonder if full-hardness 3D metal printing will end up being a two-step process.