This section shows you how to assemble the extruder drive. All the parts for the extruder drive, except for the NEMA17 motor, should be in the bag labelled ‘Extruder drive set’.

Extruder body

The extruder body holds the stepper motor, which drives the plastic filament.

# Component Qty Type
NEMA17 motor 1 Hardware
Extruder drive block 1 Extruder drive
Extruder small gear 1 Extruder drive
Retaining tongue 1 Extruder drive
623 bearing (10mm diameter) 1 Extruder drive
M3 washer 1 Extruder drive
M3x12mm countersunk socket screw 3 Extruder drive


Take the extruder body, one M3x12mm countersunk screw, the 623 bearing and an M3 washer. ORM2-extruder-drive-build-06
Put the screw in from the back, in the hole in the corner of the extruder block. Put the 623 bearing in the hole, on the screw. Put the washer on top of the bearing, as shown. This washer is sandwiched between the bearing and the motor; without it, the bearing will bind on the motor and not turn, and the extruder drive will function poorly. ORM2-extruder-drive-build-10
Fit the motor on top of the washer and bearing. Do the screw up loosely. ORM2-extruder-drive-build-12
Screw the other two M3x12mm countersunk screws through the extruder body and into the motor, to mount the motor solidly. Tighten all three screws. Check that the bearing can turn freely. ORM2-extruder-drive-build-13
Push the small gear onto the motor shaft. This should be a tight fit. Ensure the flat part of the bore of the gear is aligned with the flat on the motor shaft before applying too much force. The gear has a small lip at the bottom of the teeth. This side must be against the drive block face. There should be a small gap (0.5mm to 1mm) between the gear and the face of the extruder body. If you put a piece of folded paper under the gear when you push it down this will set that gap. Pull the paper out. Check the motor turns freely. ORM2-extruder-drive-build-14

Large extruder gear

The large extruder gear drives the filament through the Bowden tube and into the hot end.

# Component Qty Type
Extruder large gear 1 Extruder drive
Hobbed insert 1 Extruder drive
M3 washer 2 Extruder drive
M3 nyloc nut 1 Extruder drive
M3x25mm hex head screw 1 Extruder drive
MR93ZZ bearing (9mm diameter) 2 Extruder drive


Push the M3x25mm hex head screw through the gear. The hexagon head of the screw should be held tightly by the plastic part. Slide the two M3 washers on to the screw, followed by one MR93ZZ bearing, then the hobbed insert. The insert is symmetrical so it doesn’t matter which way round it is fitted, but it needs to be screwed tight. Most pairs of pliers have half-round holes in their jaws; use these to grip the hobbed insert. Tightening the insert pulls the hex head screw into the gear, and locks the bearing and hobbed insert in place. ORM2-extruder-drive-build-02
Slide second MR93ZZ bearings on, followed by the M3 nyloc nut. Tighten the nut hard against the bearing. Don’t hold the hobbed insert to tighten this nut, as that will tend to loosen the insert. Hold the gear instead. ORM2-extruder-drive-build-03
Now push the large extruder gear sub-assembly into place in the extruder body. With filament loaded, the gear can’t come out, but without filament, you should be able to pull the gear off for easy cleaning of the hobbed insert. ORM2-extruder-drive-build-15
Make sure the gap behind the gear is correct, and turn the large gear a few times to check it is meshing smoothly with the small gear. If it isn’t, check that the large gear isn’t too close to the extruder body; it may bind with the lip on the bottom of the small gear. You may also need to file the teeth of the small or large gear, if there are any inconsistencies due to manufacture. Feed a short length (200 mm or so) of filament into the drive. When it is engaged with the hobbed insert and you hold the large gear still it should be impossible to pull the filament out of the drive using your fingers. Wind the test filament out. ORM2-extruder-drive-build-16

The retaining tongue

This secures the Bowden cable from the hot end into the extruder drive.

The retaining tongue that is included in the extruder drive set. Orm_Tongue_01
For safe keeping, insert it in the drive. It goes in with the forks of the tongue upwards. ORM2-extruder-drive-build-17
It should hold itself in the drive. ORM2-extruder-drive-build-18
The finished assembly. ORM2-extruder-drive-build-19

Mounting the extruder drive on the printer

The extruder drive assembly can now be mounted on to the machine.

The x-axis-plate has three slots that the extruder drive can fit into. The standard wiring will reach to the first or second slot. Drop the drive into the first slot, then the end of the extruder body fits into a slot in the x-rib. It is held in place by the weight of the motor. ORM2-extruder-drive-build-20