NOTE - Probably not worth printing just yet, needs work. I have been running with this for a while, and because of the changes I made so that there was no holes to tighten the clips around the linear bearings, it weakened over time resulting in many failed prints. That was with just one extruder on it. Also, it was very hard to get the timing belt inside it. I think the idea is still good, but it's back to the drawing board for adjustments. I am trying to go dual extruder on my i3. I am very happy with my Greg Wades extruder for the i3, and I didn't want to lose print space in my X (which I made out of wood). It's much easier to extend my Y axis, since I just need to get slightly bigger pieces of threaded rod. I have added a backplate and modified the carriage a bit to make it possible to mount a second gregs wade extruder to the back.. It's hard to assemble at the moment, because the back plate gets in the way of easily inserting the timing belt. Prints nicely without supports. No guarantee it will work: At the moment, I fear the back extruder's NEMA 17 motor will hit the upper bearing mount. That could be adjusted by adding about 1 cm to the back plate, but I worry that will be a bit much torque. None the less, this is a starting point for a back-to-back extruder mount. I was hoping I could modify the wade hinged extruder to use nema 14 motors, but it calls on 40n-cm of torque, which is about 8 times more than the nema 14's I have can provide. First, you need to get the Prusa i3 plans: https://github.com/josefprusa/Prusa3 The openscad files I have uploaded need to be copied into the box_frame folder. Make sure carriage_l is set to 80 in the configuration.scad. You may need to trim the m3 mounting bolts, as the extruders currently line up back to back, and the bolts I have at the moment for the front extruder are too long and get in the way of mounting the back extruder.