After the success of my first printable extruder design (the Printruder, see http://www.thingiverse.com/thing:958 ), I wondered, if there would be an even simpler and better design for a Printruder.
This is what I came up with.
Please note, that there are two flavors of the main part ("Motor Block"):
This design is for use with the standard timer belt pulley, which comes with the MakerBot Extruder MK3/MK4.
This design is for use with a 10mm worm-gear style pulley
You only need one of both. Be sure to print the correct one!
The PCB holder parts are optional.
There's a post on my blog on this with more detailed information and step-by-step build instructions:
In order to mount the Printruder II in a MakerBot, you might want to print also a pair of Printable Extruder Holders: http://www.thingiverse.com/thing:1912