3Drive

3Drive is a direct drive extruder for an E3D hotend (but should be easily adaptable for other hotends that use a slot mount), designed with the following criteria:

* Compact and robust - you can butt two of these end-to-end, or side-to-side, for dual extrusion

* Close constraint of the filament - I use PTFE tube as filament guide throughout the body (before and after the Mk 8 drive gear), this means flexible filaments should not be a problem.

* Easy load - I wanted to be able to load new filament without removing the spring tension. The idler body has a thumb flap which lets you open the gap to insert new filament, although in practice the close constraint means that most filaments can just be pushed through without releasing the idler pressure.

* Mk 8 drive gear - the best drive gear I have yet found, sharp teeth and small circumference.

* E3D v6 - The mounting is designed for an E3D v6, however that should be easy to adapt for any other groove mount hotend.

I mount