Prusa I3 MK2/MK2S extruder upgrade

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Prusa I3 MK2/MK2S extruder upgrade


This extruder upgrade are for Prusa MK2 or Prusa MK2.5 where you do not have the Bondtech Drivegears. This kit contains the necessary parts to convert to our newly designed extruder with 3:1 gearing ratio for better precision and resolution together with optimized geometry for the heatsink cooling and many other cool features. I also lowers the moving weight to reduce ghosting and vibrations.



With the new Add-On this kit also supports MK3s filament sensor.
Download the files for the printable Add-On here:


This extruder upgrade kit is for the Prusa MK2 or the Prusa MK2S where you don't have our Bondtech gears. This kit contains the necessary parts to convert to our freshly designed extruder that uses 3:1 gearing ratio for improved precision and resolution, optimized geometry for the heat-sink cooling and many other improved features It also reduces the moving weight to reduce vibrations and ghosting.

This is a co-development work with awsome guys in the Prusa Community like Chris Warkocki, Grégorie Saunier (Bear Upgrades), Olof Ogland, Erik Bjorgan, Josh Jones, Kyle Wiehe, Marc Evertz, Matt Harrison, Ocie Ward, Sando Bendig, Vecko Kojchevski (Vecko Extruder), Steven Mölby that have provided excellent feedback and suggestions of how to develop the "perfect" extruder setup for the Prusa series printer. A lot of work has been spent in this project and we have tried to listen to all the inputs in order to find a solution that can be fitted to a Prusa I3 MK2, MK2S, MK2.5 and MK3.

The extruder parts are not optimized for FDM printing but for SLS printing that we use to produce the housing parts in polyamide 12 for maximum precision and strength.

This kit comes with this 25 mm pancake stepper that have 18 Ncm in torque for a lightweight but powerful extrusion and a new stepper cable for connecting the motor.

The original part-cooling fan 50x15 radial fan is used in this setup and is not included.

This setup is made to use a 40x40x10 heat-sink cooling fan that needs to be purchased separately, it is not included. The original part-cooling fan on MK2 and MK2S is 30x30x10 and will not fit.
For more effective HotEnd cooling we recommend a fan with high pressure like Sunon's MF40100V1-1000U-G99 or similar.

A FDM-printed filament sensor cover is included.

This extruder will fit the stock MK2, Mk2s carriage's and also other popular designs like MK3, Vecko, Zaribo and Bear. Check the guide for available X-Carriage here:

The E-steps needs to be updated to 415 for MK2, MK2s and MK2.5 and is easy to do by downloading this g-code file, put it on the SD card and select to print the file esteps.gcode which will set the esteps and save it. For MK3 it needs to be 830 as it uses 32 bit microstepping, use this file instead.

Weight reduction is 121 g, from 387 g as default setup compared to 266 g for this setup (Extruder, steppermotor)

This project is licenced under GPL V3 and the STEP-files are available here.


Bondtech Github. Contains Stepfile, installation manual, exploded view, and others.

Chris Warkocki Github: Contains new firmware with modifications for this extruder, read the description.


Note! This firmware is for MK3s users with the new filament sensor.

The firmware is based on 3.7.0 stable version of Prusa-firmware and support MK3s users with a Bondtech extruder.

Bondtech specific changes:

  1. Estep set to 830.
  2. Adjusted Z_MAX_POS to allow Z and XYZ calibration.
  3. Changed printer name.

Download the firmware here:


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