Technical intro.

The Flex3Drive G5 is a sweet little extruder platform. By design it can be comfortably driven by a suitable flexible shaft or smallest available nema8 motor, features our original Quick-Lock tensioner, and is fully open source.

At just 75g for the complete assembly, the G5 Nema8 is the worlds smallest lightest and most accurate true direct drive extruder. The G5 Flex comes in at a fraction over 27 grammes.

Whilst they are small the G5’s are packing the best available filament drive gears on the market (are also open source) along with our proprietary high performance 40:1 worm wheel gearset with involute tooth profile and manufactured using our own injection mould tools with a proven high quality Dupont polymer.

The G5’s also have the smallest footprint of any extruder on the market.

Flex3Drive G5 Nema8 weight check
Flex3Drive G5 mechanical footprint


The reduced moving mass and high gear ratio results in several benefits to deliver noticeably better print quality. Using a 40:1 gear ratio was found to be the optimal ratio during early testing and development, because it specifically achieves two critical design objectives.

  1. Minimizes load on a flexible shaft as far as possible avoiding excessive torsional load
  2. Can be reliably driven by smallest (lightest) spec nema8 available or with our powerful flex’ shafts.

…whilst not exceeding maximum speed capabilities the stepper motor

A ratio below 40:1 significantly increases loading on a flex’ shaft (end to end deflection) leading to uneven extrusion, poor printing, wavy surfaces, bounce and retract issues, reduced working life, sensitive to installation etc. Transmission of drive must be absolute and precise.To guarantee this under all conditions over the long term, we use a 4mm diameter heavy duty bi-directional flexible driveshaft.

For a Nema8 variant, using a lower ratio than 40:1 will require at least a heavier (nearly x2) Nema8 running near its maximum limits (causing it to run excessively hot whilst having significantly lower max rpms with its higher inductance).

In terms of major ends goals, everything evolved around a greater goal, and so the hard part has been done. There are various mounting solutions provided aswell with more being constantly added.

Use and Installation

Mechanical installation is largely the same for both, with the obvious exception of the driveshaft. There are a couple slight differences on the extruder assemblies between both. Firmware and slicer setup is the same between them.

Installation of either is easy, and will follow an approximate order something like below depending on machine and general chaos in your surroundings, and take less than an hour once you have all the downloadable plastic parts ready to roll.

  • Print the parts (if you bought barebones kit)
  • Assemble layshaft
  • Assemble G5
  • Fit to 3d printer.
  • Fit motor/flex
  • Setup firmware
  • Setup slicer
  • Run a test print

To Flex or Nema8?

This could depend on your longer term goals for a target machine, and budget. The afor mentioned greater goal of easy lightweight multi-filament may also come into play. There are pros and cons with both.

Nema8 does not require a flex’ shaft, but does require the motor. Slightly easier installation but higher cost due to motor and worm gear required. More than x2 weight penalty compared to flex, but still less than one quarter nema17 motor on its own. Using 2 nema8 vs 2 flex doubles the moving mass impact.

Nema8 for a single filament machine for slightly easier install if you have the budget, go to flex for 2 or more or if you want to update to dual in the future. That is not to say multi filament cant be done with the nema8’s just needs stronger build/belt points.

Either way, you just add a single drivetrain to upgrade a filament, or grab a multi-pack to achieve those easy multi-filament dreams with unbeatable value.