If you've been following my website for a while you've no doubt read me yammer on again and again about 3D printers that can only use low-melting point plastics as feedstock for manufacture. Usually ABS or PLA plastic, because they're cheap and relatively easy to acquire. Joshua Pearce and his research team at Michigan Tech announced late last year that they've developed an open source metal deposition printer for fabricating tools and components for which plastic isn't appropriate. Their printer lays down thin layers of metal instead of plastic to build up much stronger objects. The total cost to construct …