BTW, I took a tour of Valve with none other than Jeri Ellsworth a couple of weeks ago when I was in Bellevue. She showed me a lot of cool stuff they were working on and many nifty machines including some 3d printers. One extruded 2 kinds of plastic, a regular PLA or ABS (not sure) and a 2nd that was just used for support structures and could be disolved in a bath afterwards. Seemed like a neat use for a "dualstruder".