Adrian's Geared Extruder

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Adrian's Geared Extruder

Release status: Experimental

Finished-rear.jpg
Description
Geared Nema17 Extruder Driver
License
GPL
Author
Contributors
Based-on
Categories
CAD Models
External Link


Introduction

Finished-front.jpg

I wanted to design a universal extruder driver that could

  1. Be bolted to the X carriage of Mendel and run as a normal extruder,
  2. Be mounted somewhere at the side and drive a Bowden extruder, and
  3. Be mounted somewhere at the side and drive a Bowden paste extruder, as outlined here.

This is my first hack at a solution.

This design was made to extend Wade's neat geared extruder that you can find here. (Wade's design was based on my original here.)

Features

  1. 55:11 gear ratio means that the motor runs on very low current
  2. No hobbing or knurling to make the filament driver
  3. Torque transmitted using a wing nut, giving low stress on reprapped gears
  4. Uses the same 624 bearing as the rest of RepRap Mendel.

What you need

This describes what you need to build an extruder to mount on Mendel. Other variations will be added below when they have been tested.

The design files (AoI, STLs, and the complete RFO for immediate reprapping) are in the repository here.

Bom.jpg

This picture shows all the parts (some partly assembled) except for the two M4x20 screws that attach the extruder to Mendel's X carriage.

Description Quantity
M3x10 4
M4x12 2
M4x20 2
M4x45 6
M4x55 2
M4 nuts 13
M4 wing nut 1
M4 washers 21
624 bearings 3
NEMA17 stepper 1
M4 threaded rod 70mm
4mm diameter rod 25mm
M4 insert 1
Strip-board 50mmx25mm
4-way pin headers 2
4-way ribbon cable 130mm
16mm dia PTFE 50mm
M6 threaded brass 36mm
Thermistor 1
Kapton tape 200mm
Nichrome wire 6 ohms
Araldite rapid About 5 ml

Here is a complete list of all the non-reprapped parts and materials.

The M4 Insert is the heart of the device. It is available from here. It has an internal M4 thread and a locking grub screw. This means that it is very easy to mount on the 70mm length of M4 threaded rod, but that - once it is tightened up - it never slips.

Putting it together

The large 55-tooth gear is the one that drives the filament. It connects to the 70mm M4 threaded rod using a wing nut, which spreads the torque load on it and thus reduces the stress that the plastic is subjected to.

Wing-filing.jpg

Start by offering up the wing nut to the slots in the large gear on the opposite side to the projecting boss. Some wing nuts fit immediately. Unfortunately there does not seem to be a completely standard shape for wing nuts, so you may have to file down the inner shoulders of yours to fit, as shown here.

Driven-gear-assembly.jpg

This shows the assembled filament drive. The sequence from the bottom is:

M4 nut M4 washer 624 bearing M4 washer M4 Insert M4 washer 624 bearing M4 washer M4 nut GAP M4 nut M4 wing nut gear M4 washer M4 nut

Drive-gear-fitting.jpg


Driven-gear-assembly.jpg


Driven-gear-assembly-fitting.jpg


Finished-front.jpg


Finished-rear.jpg


Motor-filing.jpg


Nozzle-assembled.jpg


Here it is working

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