MK3NX extruder

Description:

This is my fifth “NX” project (after ProtoXtruderNX, AeroXtruderNX, AeroHGXtruderNX, TitanHGXtruderNX) adapting the HGXlite drive and a lever inspired by the NEXTRUDER from @Prusa3D.

Although I designed and printed the model myself, I don’t own an MK3 to test it directly. Based on the published makes, it’s clear that users’ prints confirm the usefulness of this idea across different MK3 versions.

MK3NX is a modification of the original MK3S+ extruder and is characterized by:

1. Identical Nozzle Geometry: It maintains the same nozzle positioning relative to the X, Y, and Z axes as the original extruder—meaning no changes to the printer's build are needed aside from modifying the extruder itself.

2. No Firmware Modifications Required: Only an update of the e-steps is necessary.

3. Reversible Upgrade: You can revert back to the original extruder at any time.

4. Utilization of Original Components: It uses the original heatsink, hotend, NEMA 17 motor, fans, and SUPERPINDA sensor with a IR filament sensor.

5. Improved Filament Feeding: Equipped with a large filament feeding gear (HGX gearbox) that works in tandem with a lever inspired by the ingenious design of the Nextruder.
   The new gear arrangement doubles the resolution of the filament feeding mechanism, delivering improved precision and smoother extrusion.

6. 360° Print Cooling: Features 360-degree print cooling using the original 5015 fan, modeled after my previous MK3S cooling remix from MK4S.

7. Prepared for MMU: The IR sensor is coupled to the tension lever (no ball blocking the filament), and an M5 socket for Fitting M5-4 has been added.

8. Cost-efficient Modernization: The upgrade involves only the purchase of the HGXlite gearbox, bearings, screws, and other necessary assembly parts.

9. There are no Bondtech gears—Issue #602 is limited or should not occur.

NOTES:

• This project is my own idea for modifying the extruder of the MK3S+ printer.

• It is not a certified solution dedicated to the Prusa MK3S+, nor does it comply with VDE, IEC, or similar standards.

• Any modifications to the printer increase the risk of accidents and fires.

• Never leave the printer powered on unattended.

• Use it at your own risk.

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To build the MK3NX you will need:

1. MK3S+ original extruder (original heatsink, hotend, NEMA 17 motor, fans, SUPERPINDA sensor, IR filament sensor, screws etc.).

2. HGX lite kit (affiliate link)

3. Trianglelab brass gear 5mm/0.5M 17T (affiliate link) or other similar 5mm/0.5M17T(affiliate link).

4. DIN 6325 3x16 mm m6 steel cylindrical mandrel (not affiliate link) as an shaft for the large filament wheel.

5. Tubular spacer 4x3x9mm x 1pcs - I made one out of a brass tube that I have(affiliate link)
   

6. Shaft 3x7.5mm x 2pcs (I cut a free pin 3x16 from the HGX gearbox) or some ready-made shafts (affiliate link)
   

   
    

7. 683ZZ bearings with U-groove x 2pcs (affiliate link)

8. spacer 6x3x8mm x 1pcs (affiliate link)
   

9. Spring 5x15x0.8mm x 2pcs (affiliate link)- I made two from the long one I bought earlier(affiliate link)

10. Heatsink PTFE tube 4,5mm longer than original (MK3S+) 42.3mm +4,5mm =46.8mm(tolerance +/- 0.2mm).

11. Screws and nuts (you can find some in the old extruder and in the HGXkit):
    - M2x8mm SHCS x 1pcs (from MK3S+ extruder)
    - M2x10mm or longer x 1pcs
    - M3x50mm SHCS x 2pcs trimmed to M3x37.5mm
    

    
    - M3x20mm BHCS x 2pcs (from MK3S+ extruder)
    - M3 nyloc nut x 2pcs
    - M3x6mm SHCS x 1pcs
    - M3x10mm SHCS x 5pcs (from MK3S+ extruder)
    - M3x14mm SHCS x 3pcs (from MK3S+ extruder)
    - M3x18mm SHCS x 3pcs (one from MK3S+ extruder)
    - M3x20mm SHCS x 3pcs (from HGXlite kit)
    - M3x22mm SHCS x 1pcs (from MK3S+ extruder)
    - M3x27mm SHCS x 1pcs
    - M3x30mm SHCS x 1pcs
    - M3x35mm SHCS x 1pcs
    - M3x40mm SHCS x 2pcs (from MK3S+ extruder)
    - M3x45mm SHCS x 2pcs
    - M3x59,5mm SHCS x 1pcs
    - M3nS - quantity not greater than that of the original MK3S+ extruder
    - M3 nut x 12pcs

Inventory does not include items needed for X-carriage installation - I assume X-carriage will not change.... You may possibly need to adapt to the IR sensor plug.

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Firmware - MARLIN

The extruder motor's rotation direction in the firmware remains unchanged.

>>> outdated data:: The theoretical e-steps value for the new MK3NX gear system is E637.9. (see updated 28.10.2025)

!!!

@DougMorrisDC_910730 gave me the current e-steps for his MK3NX:

M92 X100.00 Y100.00 Z400.00 E651.02

THANK YOU!

!!!

!!!Please note that the E-STEPS value should be properly calibrated/verified for each specific printer. !!!

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How do you change the e-steps value on the MK3S+?
You can use one of the two methods below:

1. Using the LCD Interface:
Navigate to the printer's main menu.
Press and hold the dial (or button) to access advanced hardware settings, where you can change the e-steps value.
Set the e-steps to E637.9 and confirm the changes.
The printer will either restart or automatically save the new value in the EEPROM.
2. Using G-code Commands:
Connect your printer to your computer and open a terminal (using software such as Pronterface, OctoPrint, or the terminal in PrusaSlicer).
Send the command:
M92 E637.9
to set the new e-steps value.
Then send the command:
M500
to save the changes to the EEPROM.

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Printing Settings and Post-Print Actions.

I have included notes, printing settings, and post-printing procedures in the file: "MK3NX print settings tips and after printing en.pdf" file.

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Assembly MK3NX

The assembly can be divided into three parts:

1. Preliminary Assembly: Assemble the new gearbox along with its housing. This step is intended to verify that the parts have been printed correctly, to check the backlash between the HGXlite gears and adjust the lever pressure.
   I recommend pre-assembly - especially if you only have one printer.

2. Main Assembly: Assemble the MK3NX extruder.

3. Final Assembly: Mount MK3NX to x-carriage.

The instructions for both the initial and main assemblies are provided in separate PDF files.

Installation of the MK3NX to the X-carriage, should be carried out according to PRUSA's instructions available on their website.

I recommend the X-Carriage back remix by @BentDerailleur:

https://www.printables.com/model/1720960-prusa-i3-mk3-x-carriage-back-with-slot

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The following 3D models have been used to visualise MK3NX:

https://grabcad.com/library/prusa-superpinda-1

https://grabcad.com/library/fan-4010-orion-fan-od4010-24hb01a-1

https://grabcad.com/library/e3d-v6-hotend-5

https://grabcad.com/library/pneumatic-quick-connector-poc-4-m5-1

https://grabcad.com/library/nema-17-40x40mm-1

https://github.com/prusa3d/MKxS-IR-sensor/tree/master/rev.041

https://github.com/prusa3d/Original-Prusa-i3/tree/MK3S/Printed-Parts/STEP

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Updated 25.05.2026

I have uploaded a new version of MK3NX Main Assembly en v1.pdf.

I have incorporated @BentDerailleur’s comments into it.

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Updated 20.05.2026

Updated description.

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Updated 08.03.2026

Updated description.

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Updated 04.03.2026

Updated description.

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Updated 04.11.2025

Updated description.

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Updated 28.10.2025

Updated description.

I updated the value of e-steps according to information from @DougMorrisDC_910730

THANK YOU!

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Updated 18.09.2025

Updated description.

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Updated 07.06.2025

Updated description.

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Updated 05.06.2025

I have added the revised MK3NX Main Assembly en v0.1.pdf