November 26, 2025
Description
In early 2025, I replaced my two PRUSA MK4S printers with two PRUSA CORE ONE printers (one assembled and one kit).
The second MK4S printer had the MMU extension; I kept this accessory to remount it on the one delivered as a kit.
I received the CORE ONE printer as a kit in April 2025, the same date that firmware 6.3.1 supporting MMU was released.
See my others add-ons for the MMU3 :
First of all, it is essential to update the Nextruder to make it compatible with the MMU.
Follow the official PRUSA procedure: https://help.prusa3d.com/guide/9a-mk4-s-mk3-9-s-nextruder-mod_683106#683464
For space reasons, I wanted to keep the MMU positioned at the rear of the CORE ONE (as on the MK4S) and I wanted a mounting method similar to that of the MK4S (suspension from the frame) so as not to have to replace any parts.
For these reasons, I designed a rail that attaches to the rear of the CORE ONE printer (the mounting holes already exist); the rail has the same shape and dimensions as the MK4S frame.
Additionally, the rail allows to slide the MMU laterally without any fixing or adjustment devices.
1a. Prepare accessories :
- 2 x M3x12mm SHCS screws (or 2 x M3x10mm for rail V2B)
- 2 x M3 washers
- 2 x M3 lock nuts
1b. Position the rail on the rear frame and insert the two M3x12mm SHCS screws into the existing holes.
1c. Secure with the two M3 washers and the two M3 lock nuts.
1d. Suspend the MMU on the rail.
1e. Open the cable cover on the back of the printer, unscrew and remove the Xbuddy board cover. Route the MMU cable through the top left hole of the cover and connect it to the expansion card. Carefully close the xBuddy board case.
1f. Close the cable cover on the back of the printer ; the hole for the MMU cable already exists.
The best position is to put the MMU3 on the right of the rail to avoid the PTFE tube being too tight when using filaments in slots number 1 or 2.
The assembly uses the original PTFE tube from the CORE ONE.
This must be removed from the side sensor and then connected to the MMU.
The PTFE tube must pass through the upper acrylic plate. A first solution would be to make a hole to allow the PTFE tube to pass through to the MMU. By analyzing the movements of the print head, we see that the PTFE tube moves back and forth because its attachment point is off-center relative to the Swingarm axis.
On the surface of the acrylic plate, the PTFE tube moves in a 4cm x 4cm square. Such an opening could create an uncontrolled hot air leak for specialty materials (ABS, ASA, PC, etc.).
I therefore opted for a system that allows the PTFE tube to move horizontally while maintaining its tightness as it passes through the acrylic plate.
2a. Prepare accessories :
- 3 x M3x10mm SHCS screws
- 3 x M3 lock nuts
2b. Remove the acrylic top plate by removing the plastic clips and remove the PTFE tube from the side filament sensor.
2c. Place the acrylic plate on a piece of cardboard (be careful, the plate is not symmetrical) in the position it has on the printer. Place "PrusaCoreOne_MMUH_AcrylicCuttingTool" on the top right corner of the plate with the inscriptions visible.
2e. Align the M3 holes of "PrusaCoreOne_MMUH_AcrylicCuttingTool" with those of the acrylic plate; the two large corner holes must be perfectly aligned ; drive the screws into the cardboard. With a felt-tip pen, trace the outline of "PrusaCoreOne_MMUH_AcrylicCuttingTool".
2f. At the intersection of the two lines, drill a 3mm hole; this will prevent the acrylic plate from cracking. Then cut the acrylic sheet along the edges of "PrusaCoreOne_MMUH_AcrylicCuttingTool".
2g. Insert three M3 nuts into "PrusaCoreOne_MMUH_PTFEGuideBase".
2h. Place "PrusaCoreOne_MMUH_PTFEGuideBase". under the frame in the upper right corner and pass the PTFE tube through its hole.
2i. Slide "PrusaCoreOne_MMUH_PTFEGuideDisk" into the PTFE tube ; its central hole is inclined to follow the curve of the PTFE tube.
2j. Slide “PrusaCoreOne_MMUH_PTFEGuideCover” into the PTFE tube. Pass the (1) and (2) M3x10mm screws through the holes in the frame. Tighten the three screws with the three nuts.
2k. Connect the PTFE tube to the MMU.
2l. Slide the acrylic plate onto the top frame, inserting it into the guide slots. Finally, fix the acrylic plate with the plastic clips.
How it works :
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At the time of publishing this model, the "PRUSA CORE ONE MMU3" profile is not yet available.
While waiting for it to be officially released, I have developed a "PRUSA CORE ONE MMU3" profile to be able to use the MMU ; it is inspired by those of the MK4S MMU3 and the CORE ONE.
3a. Open PrusaSlicer
3b. In 'Printer' select the System preset 'Prusa Core ONE HF0.4mm nozzle'
3c. Click on the cog-wheel and 'Edit preset'
3d. Click on 'Printer' tab :
- Général > Capabilities > Extruders : 5
- Général > Capabilities > Single Extruder Multi Material : Checked
- Custom G-code > Start G-code : replace with the text of "CustomGcode_Start_dancan13f_V2.txt" file
- Custom G-code > End G-code : replace with the text of "CustomGcode_End_dancan13f_V2.txt" file
3e. Save the preset as “Prusa CORE One MMU3 HF0.4 nozzle”. If you have configured a physical printer, associate the "Prusa CORE One MMU3 HF0.4 nozzle" preset with your physical printer.
Note : If the first filament selected is not #1, the printer show this message :
/!\Warning
The G-code is not fully compatible.
/!\ The nozzle flow rate does not match.
Click on the “Print” button to continue.
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04/05/2025
New version for MMU3 Profiles ("CustomGcode_Start_dancan13f_V2.txt" and "CustomGcode_End_dancan13f_V2.txt" inspired by the PrusaResearch.ini file in which the CORE ONE MMU3 configuration is still in comments.
Thank's to @Atilla_335002.
27/05/2025
Marking chapter "3. MMU3 SETUP" as OBSOLETE.
29/05/2025
New files (with and without screws holes) :
. “PrusaCoreOne_MMUH_MMU3HolderV2.stl” (with holes)
. “PrusaCoreOne_MMUH_MMU3HolderV2B.stl” (without holes ; to mount with M3x10mm)
This rail is 17mm higher ; it allows the mounting of the MMU3 with the original Prusa Advanced Filtration.
02/06/2025
New file “PrusaCoreOne_TopCover_Cutted.step” for those who wish to make an acrylic panel cutout.
04/06/2025
New files “PrusaCoreOne_TopCover_Cutted.dxf” and “PrusaCoreOne_TopCover_Cutted.pdf” converted from “PrusaCoreOne_TopCover_Cutted.step” by @chris-hill.
19/08/2025
New version of file “PrusaCoreOne_TopCover_Cutted.step” without any chamfer.
License:
Creative Commons — Attribution — Noncommercial
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dancan13f
