Flex3Drive 2in1 Duo – Exclusive



The Flex3Drive 2in1-Duo is a new addition to the F3D ecosystem of remotely driven extruders that we pioneered. A compact lightweight dual direct drive extruder and hotend package designed to work together from the ground up. We have put in a lot of work to create a dedicated extruder and hotend package with the smallest footprint of any dual filament system currently available. By utilizing our already proven 40:1 gear train driven by our robust flexible shafts, coupled with a slim dual channel hotend we have a small powerful and effective package for mixing, switching and multi-material.

The Extruder

The main extruder body has a mounting hole footprint of 43mm x 24mm. The hotend is fixed directly to the extruder body, so no need for adaptors for different machines. Just a simple bracket template. The two extruder channels are separated by a distance of 4.5mm between centres which feed down into the hotend.

We have retained our original vertical locking tension arm with the cam lever arrangement that provides a solid and non flexing tension arm assembly. this means the same tension on the filament between filament changes and during print time, all the time, every time.

Filament loading is also extremely easy with filament guide tubes integrated into the tension arm. Simply unlock the tensioner, pull the old filament out and insert new filament and relock the tensioner. Filament is guided all the way into the hotend. No need to remove the tension arm.

The Hotend

Designed for dual 1.75mm filament our dual channel JHead style hotend is a new development, unique in the marketplace. It includes the ability to change nozzles which are available separately in sizes from 0.25mm through to 0.8mm. Standard supplied size is 0.4mm. The 2in1Duo avoids issues related to leveling two separate nozzles, designed with the intention of delivering dual filament extrusion with ultimate convenience and ease of setup.

It is also possible to run two dissimilar materials such as a rigid and a flexible material if the printing temps are in close range. Imagine printing a hand prosthetic, using an ABS for the fingers, and a flexible material for the knuckles and finger joints. Imagine no more. The 2in1Duo will enable this. It should be noted the hotend is not suitable for hit temp materials above 255c at this time, we have a separate all metal version in the pipeline.


As with all the extruders in the Flex3Drive ecosystem the 2in1Duo comes complete with its own cooling system based on 3 x 25mm fans. One centrally mounted fan keeps the hotend cool whilst two other fans mounted below on each side provide print cooling with a pair of small directed print ducts. The shroud mounts onto the hotend clamps, and the print cooling fans mount onto the shroud.

Printing Modes

The 2in1Duo is versatile and can be used in several ways. Depending on the part being printed, you can avoid use of a purge tower by doing the colour change within the infill. Alternatively, dependent on material type, colours etc, a purge tower as small as 23x23mm will provide a clean colour transition. The 2in1Duo can also print in a single colour mode as and when required. Just keep both filament channels loaded to avoid pushing filament up and out of an empty channel.

The F3D App

Our gcode post processor app provides easy access to simple switching and gradient mixing throughout the height of a print, using gcode produced from a standard single nozzle slicer output. Sweep a single gradual colour transition throughout a print, or graduate the transition multiple times back and forth. This can also be done with a sharp transition, to give a striped effect. Simply load your gcode file into the app, select your preferences and a new gcode file will be saved with the required changes made.

The app currently supports gcode output from Cura and S3D, and targeted at either Marlin or Duet firmware since slightly different commands are required between the two.

Slicing and Firmware

Profiles for Cura and S3D have been created, from which the user can then change based on specific needs however these baseline templates provide a very good starting point that will achieve good quality dual colour prints out of the box so long as some simpyk standard procedures are followed (such as setting material type, true diameter and temps correctly).

Full support is provided for setting up the latest version of Marlin (1.1.8 at time of writing)

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Features include:

  • Aimed specificaly at dual colour prints – dual materials can also be printed if temp ranges match.
  • Complete with dual filament hotend
  • Changeable nozzle tips from 0.25 – 0.8mm
  • Single quick release tensioner keeps both filaments correctly tensioned
  • 40:1 gear ratio delivers highest resolution filament control of any extruder+hotend currently available
  • Fully guided filament inlet through the tensioner arm provides full pass through containment
  • Fully contained filament force path below the filament drive gear – nowhere for the filament to go except down
  • Integrated hotend mounting holds the hotend securely
  • Easy carriage mounting with central hotend location
  • Robust construction will last for thousands of hours of trouble free printing
  • Integrated hotend cooling
  • Smoothly print fine (50 micron or less) layer heights
  • Torquey enough for high speed machines
  • Available with any length driveshaft
  • Carriages and template drawings will be available in our download section
  • Comes with full instructions
  • Compatible with all dual drive capable electronics and all 1.8 degree step angle Nema17 motors

Whats in the Box?

  • Complete and assembled 2in1-Duo extruder for 1.75mm filament
  • 2in1-Duo dual inlet hotend (attached and wired in)
  • Flexible Driveshafts with printed motor shaft couplings
  • 2 x Motor mount assemblies
  • 2 x Motor Caps to support the flexible shaft above the motor
  • PTFE Tubing for driveshaft and filament guide (upto 4mtrs depending on target machine)
  • Tubing Clips
  • Hotend Shroud + print cooling
  • 3 x 25mm hotend and print cooling fans
  • Fastener Kit