Thing-O-Matic 4-Axis Stepper Extruder

It's clear from the RepG source code and firmwares on git that Makerbot is just about to release a MK6 extruder, which will be stepper-driven on the 4th axis of the Thing-O-Matic. You can stay ahead of the curve by getting in now! Driving your stepper from the axis gives you control as fine as you'd possibly like. In addition, it's a great way to get around the problems some people (me!) have had with the Thing-O-Matic extruder controller's motor port; it's not used in this build (although I