Wade's Geared Extruder

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Revision as of 16:27, 15 July 2010 by Casainho (talk | contribs) (Added video showing the extruder working/printing.)
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Wade's Geared Extruder

Release status: Stable

Geared Nema 17 Extruder
CAD Models
External Link

Characteristics/advantages of this extruder:

  • 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;

Video recorded by Casainho showing his Geared Nema17 Extruder working/printing: My first reprap mendel print-jpcasainho-20100622.jpg

Photos from Thingiverse , of other people's copies of this extruder.

Here is a link to a previous version of this page that describes an earlier version of this extruder that uses an M4 shaft, and includes more details about pull testing the two versions: "Geard Nema 17 Exteruder Version 0.5"

Mechanical Construction


  • 3 X 608 bearings (Skateboard bearings);
  • 1 X M8X50 bolt;
  • 1 X M8 nut (Nylock works better, but a pair of nuts will also work);
  • 4 X M8 washers;
  • 1 X M8X20 piece of smooth bar, threaded bar or a bolt;
  • 4 X M4X45 bolts;
  • 4 X M4 nuts;
  • 4 X M4 washers;
  • 4 X M3X15 bolts;
  • 2 X M3X35 bolts;
  • 8 X M3 washers;
  • 4 X Springs - 1 mm diameter wire, wound to an OD of 10 mm, with 4 active coils. For a given filament drive force, you'll need about twice the spring force - ie, if you want 100 N of filament drive, your springs need to push with about 50 N each.

Printed Parts

  • 1 X M8_Extruder_Block_3.stl
  • 1 X M8_Extruder_Idler_Block_2.stl
  • 1 X 11t17p.stl
  • 1 X 39t17p.stl


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 from Casainho: If you're not sure where to cut the pinchwheel slot, test assemble the extruder, making sure you leave room for the motor mount bolt heads under the 39 tooth gear, and mark the M8 bolt where it crosses the filament feed channel.

M8 1.jpg

This is an earlier version with using threaded rod - it's harder to get the hobbing concentric when you cut it into the threads.

M8 2.jpg

Using the smooth part of a shoulder bolt works better.

M8 2inside.jpg

Note - I prefer to use a Nylock nut on the end of the M8 shaft. Locktite should work as well, or a longer bolt with two nuts.

M8 2gears.jpg

So far so good! If you add 3 or 4 M4 washers on each bolt before you put the idler block on, it will reduce the idler block travel when loading new filament, making loading new filament much easier.

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.

Hot End

Attach a length of 16 mm OD PTFE using the two M bolts to pin it in place. I pre-drilled the PTFE mounting holes with a 2.3 mm drill, which made for a tight friction fit.

The nozzle can be built however you like; I build them similar to this: http://reprap.org/wiki/Mendel_extruder

I use 8mm od brass rod, with a 4 mm ID melt chamber, insulated nichrome wire and furnace cement to hold it all together.

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