NOTE: For G5 Nema8 please follow instructions on the G5 Flex Assembly page until end of step 3.7 then continue here.


Note: Assembly of the G5 Nema8 is largely the same as the G5 flex with some slight differences. This is primarily due to the mounting of the Nema8 motor with worm gear attached to the motor shaft, instead of drive being delivered via flex shaft.

Because of the difference between the flex shaft and Nema8 motor shaft the worm gears are different and are not interchangeable.

To continue, you will have completed assembly up to and including step 3.7 on the G5 Flex Assembly page leaving you with an open shell, and lubricated wheel gear on the assembled layshaft sitting in the G5 base as shown in the image below.

The G5 Nema8 parts buffett (and those screws would not stay still)


3.8  After applying lubricant to the wheel gear in previous steps, place the extruder top onto the assembly. Use the M2.5×30 (1 of) and M2.5×25 (2 of) cap head bolts to secure the assembly together.

The M2.5×25 bolts should go into the holes beneath the motor mounting feature as highlighted below. To keep the assembly together before installation onto the printer, use M2.5 nuts underneath to hold it together.

G5 Nema8 bolt locations


3.9   Now we fix the worm gear with lower bearing onto the motor. If the motor came with the gear attached you can skip this step.

Apply some cyanoacrylate adhesive into the bore of the worm gear making sure it is spread around the inner diameter of the bore.

Holding the gear with the bore facing upward to avoid the adhesive running down the motor shaft and into the motor, firmly push the motor down from above as far as it will go.


The press fit of the worm gear onto the motor shaft is enough on its own to hold the gear securely. Using the cyanoacrylate adhesive provides added insurance that the gear is fixed solid to the motor shaft.

The motor shaft will have a small amount of longitudinal movement when being pressed down. This is normal and will release when pressure is removed. The worm gear will be correctly positioned on the motor shaft, with clearance between the motor body and top of the gear.

Flex3Drive G5 Nema8 motor with worm gear and bearing fitted


3.10   Fitting the Nema8 motor with worm gear and lower bearing onto the G5 is completed after the extruder is mounted onto an adaptor mounting plate, or onto the 3d printer, depending on the 3d printer and carriage arrangement.

The lower bearing acts as a lateral support to avoid excessive sideways load on the motor shaft. When fitted, the motor is held rigid due to the way the forces act upon the mounting points, and lower worm gear bearing.

Once the motor is correctly seated, use the 2 x M2x10 button head screws using the supplied 1.3mm hex key.

G5 Nema8 with motor fitted to assembly


3.11   Assemble and fit the Tension Arm as per steps 3.11 and 3.12 on G5 Flex Assembly.

Note: the G5 Nema8 Tension arm is slightly different in shape to provide clearance from the motor when it is fitted. However the profile shape on all G5 tension arms can be reworked if so desired.

Flex3Drive G5 Nema8 Tension Arm assembly
Flex3Drive G5 Nema8 Tension Arm assembly fitted


3.12   Prepare and fit the PTFE filament guide tube as per step 3.14 on G5 flex Assembly.

The PTFE filament guide on the G5 Nemaq8 should be long enough to protrude above the motor for easy access.It can also be secured to the motor body with a cable tie.

Flex3Drive G5 Nema8 showing filament guide tube

This completes the assembly of the Flex3Drive G5 Nema8 extruder. For more information and examples of how it is fitted to different 3d printers, please see the Installs section