I made a derivative because I wanted a single object that would allow direct drive of both DC and stepper motors, offset steppers using Ruttmeister's gears http://www.thingiverse.com/thing:5795 and incorporate ScribbleJ's tensioner!http://www.thingiverse.com/thing:6402 http://www.thingiverse.com/thing:5795The above links contain instructions on assembly and required components.I have not made this part yet as I'm running very low on ABS. However I've sliced it up in SF and the mesh has no errors and looks fine.Lenbok suggested adding a cleaning portal to get to the filament drive gear so it could be flossed without needing to take the tensioner off, which is the only modification in the second file. If there are any glaring errors let me know and I'll tweak the file.