Summary

Alternative filament feeder that uses a bolt directly attached to the stepper to feed filament.

Instructions

Download and print bolt_feeder_base.stl, then join together with 4 3mm bolts. The bolts act as a friction hold to adjust the tension on the filament. There is space left for brackets to be placed where the bolt holes are. The filament comes out of the exact centre of the model, which should make joining this with other extruder brackets a bit easier.

Still to model:

brackets for mounting to hot end, stepper motor
- joiner to connect stepper motor to bolt head

I got frustrated with the extruder feeder clogging up with bits of PLA, so had a think about what other mechanisms I could use to feed the filament, preferably without the need for purchasing extra metal parts. This is my first attempt at something a little different that feeds the filament directly beside the bolt, using the bolt thread to push the filament.

Initial model:

M8 thread depths were taken from http://www.newmantools.com/tech/threadm.htm
Update 1:
added 0.25mm to circle radiuses to account for extrusion width
Update 2:
modified enclosure (hopefully a near-final design) to hold full length of bolt and support brackets

The openSCAD file has variables for almost all the things you might want to adjust. In particular, bolt/screw length, bolt/screw diameter, and filament diameter.

Bolt filament feeder