Wade's Geared Extruder

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Wade's Geared Extruder

Release status: Stable

Geared Nema 17 Extruder
CAD Models
External Link

My Repraps, both Darwins and Mendels are all currently limited by the speed and reliabilty of my extruder. I use a Mk II Extruder for most of my printing, as it has proven to be the most reliable, but it won't extrude much above 3 mm^3/s of ABS or PLA. My goal is to try and build a reliable, printed extruder that can extrude at least 6 mm^3/s, and with luck, more.

I have built several direct drive pinch wheel extruders, but none have yet had enough torque to extrude at 3 mm^3/s, so I decided to backtrack a bit and try for a more robust extruder design.


  • extrude/print at high speed;
  • good for use with a low torque Nema 17 motor;
  • no need to glue the PTFE barrel;
  • no need to use expensive metal gears;
  • no need to use expensive and complex tools - just one hand drill, a file and a M3 tap;
  • no need to make splines on motor shaft;
  • no need to do two precision flats on motor shaft;

Mechanical Construction


  • 3 X 608 bearings;
  • 1 X M8X50 bolt;
  • 1 X M8 nut;
  • 4 X M8 washers;
  • 1 X M8X20 piece of bar, threaded bar or a bolt;
  • 4 X M4X40 bolts;
  • 4 X M4 nuts;
  • 4 X M4 washers;
  • 4 X M3X10 bolts;
  • 2 X M3X35 bolts;
  • 2 X M3 nuts;
  • 8 X M3 washers;

How to build it

I used a hand drill and a file to cut the slot, then hobbed it with an M3 tap mounted in the drill, using bearings mounted in a vise to let the bolt spin - see the next videos:

M8 1.jpg

M8 2.jpg

M8 2inside.jpg

M8 2gears.jpg

So far so good!

Here's the test jig:

M8 test jig.jpg

This extruder hit 16 kg - here's the results: M8 shoulder bolt - 7.0kg, adjusted tension, new springs - 11.0 kg,

Tightened springs, 3 trials:

15.5 kg, 16.5 kg, 15.25 kg

The final failure mode was the stepper running in reverse, as opposed to the filament slipping. That's quite promising.

3D CAD Files

Here's the design files for the latest version:

Finally, here's a spreadsheet to help calculate the proper feedrates: media:feedrates.ods | media:feedrates.xls