Status: version 3.1, beta testing

View 3D CAD file:

Github repository:


ItemAmountDescriptionSource of supplyComment
Extruder Screw1extruder screwcustom part, steel, drawing/parameters
Extruder Barrel1includes mount and water cooling channelscustom part, steel, see step file
Nozzle1standard 3D printer nozzle, type E3D V6 1.75mm; optionally hardenede.g. nozzle diameters are 0.4 or 0.6mm
NEMA 23 Stepper Motor with gear box1see notes below

Shaft Coupler1rigid shaft coupler 10mm to 12mm, D=max30, L=40e.g. [] or []do not use flexible couplers, they cannot take axial load
Heating cartridge240W, 24V, 6mm x 30mm

Metal Cage1several laser cut aluminum partscustom parts, aluminum 3mm,
laser-cutting folder on github

Pellet Inlet1
custom part, PLA/resin, 3d printed, see github
Pellet Tank1
custom part, PLA/resin, 3d printed, see github
Temperature Sensor1standard thermistor for use with 3d printer controller board (e.g. 100K NTC)


for attaching the inlet to the lower aluminum plate
for connecting pellet inlet and tank
M3 brass insert6
e.g. []
Pneumatic fitting G1/8"2Fitting G1/8" for 4 or 6mm tubinge.g. Festo QSML-1/8-4-100

for water cooling, use tubing size to fit your cooling system

We recommend liquid thread sealant

Closing plug G1/8"1Closing plug G1/8" hex sockete.g. []We recommend liquid thread sealant

To run the extruder you will also need a water cooling system:

  • the best (and also most expensive) option is a industrial water chiller
  • Another good option is a PC cooling system, including pump and a radiator
  • Alternatively just use a cheap aquarium water pump. If you have a big water reservoir (>3 liters) you can also skip the radiator

We are currently mainly using PolyMIM materials, as these feedstocks can be debindered easily in a water bath. See DIY 3D Printing with MIM Feedstock for tips on using the extruder for 3d printing.


The extruder uses a NEMA23 stepper motor with gear box. It needs to have the following specs:

  • The gear box needs to have 4 M5 threaded holes for mounting, lying on a circle d=45mm
  • The gearbox shaft should have a diameter of d=12mm. Use a different coupler if the shaft has a different diameter
  • The gearbox diameter should be D=56mm or smaller
  • The length of the motor and gearbox are noncritical for the design. Typical sizes are L1=60mm and L2=56mm
  • The gear ratio should be in the range of 1:15 to 1:47. A gear ratio of 1:28 seems to be a good compromise, but is hard to get

Sources of supply:

Size/Mounting Holes

Assembly Notes

  • The aluminum plate directly above the barrel needs to be manually adjusted to create a smooth transition between the hopper and the barrel inlet. For this, chamfer the edges with a file.
  • The left and the right side aluminum plate are similar, but not identical. The 3d printed inlet only fits in one of them.
  • If you want the inlet to be on the right side instead of the left side, you can do that without modifying the parts, they are symmetrical.
  • For the water cooling parts:
    • The barrel includes channels for water cooling. There are 3 openings: the 2 next to each other are inlet / outlet, the 3rd one needs to be closed
    • For inlet and outlet install a G1/8" fitting for 4 or 6mm tubing. Choose the tubing size that fits your cooling system (or use an adapter)
    • Use a G1/8" closing plug with hex socket to close the 3rd hole
    • We recommend liquid thread sealant to make the connections water tight
  • At the backside of the barrel tip there is a M3 threaded hole. This is intended to mount your temperature sensor. If you have a glass body type thermistor, use a soft (e.g. PTFE) washer backed by a standard (metal) washer to hold it down to prevent damaging the sensor.
  • There are two 6mm bores in the barrel tip for inserting standard 3d printing heating cartridges. They usually stay in place without needing anything fastening. Use a punch near the bore if the cartridge is loose.

Copyright FabLab München e.V. 2021-2023
Licensed under the CERN-OHL-P v2
You may redistribute and modify this documentation and make products
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