lots of potential: Theta Printer - Simultaneous Dual Extrusion http://buff.ly/1j1m4oD
I’ve been pondering something like this for the purpose of better printing round objects like gears and such. Not the dual extruder but the rotating 4th axis. One problem I have with this is that the linear speed near the center of the platform approaches 0 no matter how fast you rotate the platform and rotating the platform fast will be difficult for a large variety or reasons, for instance, angular momentum and the effect it might have on adhesion of parts nearer the perimeter.
i’m particularly interested in getting high speed prints, imho this is one of the key criteria to get 3d printing to the masses.
Jason, I designed the arms to be able to overshoot the center a little bit. This means that when you are doing short moves near the center, the platter never has to do a full 180° (only 90° at most). The slicer has to be programmed to take advantage of this, however.