E3D v6 Direct Drive Extruder
by Thingiverse
Direct drive extruder for E3D v6 1.75mm hot end. The included X-carriage is compatible with Prusa i3.
The extruder is designed so that the hot end is as close as possible to the x-carriage for maximum rigidity and build area. There are optional mounts for LJ12A inductive bed probe and 5015S filament cooling turbine - highly recomended.
I started with this design: and redisigned it completely, since I found it flexes too much under high extrusion speeds and reduces build area.
The drive gear is a bit inaccesible due to the stepper motor being in front, but I haven't found this to be a problem. The filament can be loaded by inserting it right to the drive gear and then extruding about 70mm.
You will need:

Nema 17 stepper motor
MK8 Drive gear
40mm fan
5015S turbine fan (recomended)
LJ12A inductive bed probe (optional)
5x10x4mm ball bearing
Some M3 and M4 nuts and bolts

The extruder works extremly well with classic filaments like PLA and ABS. I haven't tried any flexible filaments yet.
Note: Some parts in the pictures are mirrored. I suggest you mirror them according to your printer location for the best accesibility.