Ron's Compact Extruder, Mark III (Q90607)

A direct drive extruder designed for use with a Minebea geared stepper motor, a Makerbot drive wheel, and a MakerGear GrooveMount (or similar) hot end. Version 3 simplifies the design a bit, and tweaks it to make a stronger print. I left ulti_rcx_2.stl, along with the old sources here because I broke ultimaker support while redesigning it. Version 2 addresses two issues I had with version 1. 1) Idler pressure was very touchy - as you increased pressure on the idler, it would put axial force on the motor's gearbox, which can't be good. I added a pocket for a 115ZZ bearing, to buttress the drive shaft. 2) I found that even with the bearing on the drive shaft, I have to run the motor hotter than I'd like, so I added a bracket for a 40mm fan. Also, I split the extruder body into 2 slices, to make it easier to print. Finally, thanks to canadaduane, we now have a variant which replaces the ultimaker's bowden extruder with a lightweight carriage mounted extruder. P.S. ezmobius (actually, Triffid_Hunter) has designed a fan shroud to go with his extruder body which is better than the bracket I provided, so use the fan shroud from http://www.thingiverse.com/thing:24390