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10A. MK4 Setup and Calibration

10A. MK4 Setup and Calibration

10A. MK4 Setup and Calibration
Relevant for:
Last updated 19 days ago
10A. MK4 Setup and Calibration
 Difficulty
Difficult
 Steps
25
 Available languages
CSPLDEESITFR
Attaching the MMU unit (part 1)
Attaching the MMU unit (part 1)
Attaching the MMU unit (part 1)
Attaching the MMU unit (part 1)
The MMU3 unit should be placed onto the top part of the printer's frame.
Place the MMU3 unit onto the frame.

Attach it just by the top hooks.
Look from behind, there are "clamps", which will be used to lock the unit to the frame in the next step.
Attaching the MMU unit (part 2)
Attaching the MMU unit (part 2)
Press the back part of the MMU3 unit downwards slightly, until the clamps lock to the frame.
Check that both bottom clamps on the unit are fully engaged.
If you need to remove the unit from the frame, simply lift the back part up to disengage the clamps.
xBuddy preparation
xBuddy preparation
xBuddy preparation
xBuddy preparation
On the left side of the printer, remove the four M3x6 screws holding the xBuddy box cover in place. Then, take off the cover.
Loosen the two M3x18 screws holding the ext-cable-holder.
Raise the cable holder.
Use needle-nose pliers to remove the indicated part of the cable holder, creating space for the MMU cable.
Guiding the cable
Guiding the cable
Guiding the cable
Guiding the cable
Guide the cable from the MMU unit along the frame, directing it towards the electronics.
Guide the cable into the xBuddy box through the opening on top.
Connect the MMU cable into the marked connector on the xBuddy board.
Closing the electronics box
Closing the electronics box
Closing the electronics box
Reattach the ext-cable-holder, ensuring that the MMU cable on the side is properly seated and that none of the cables are being compressed.
Tighten the two M3x18 screws on top of the ext-cable-holder.
Align the xBuddy box cover with the xBuddy box and secure it with four M3x6 screws.
Software Download
Software Download
Software Download
Visit the MMU3 page on Help.Prusa3D.com
Download the latest Drivers & Apps package.
MMU3 on MK4 requires Drivers & Apps (PrusaSlicer) version 2.7.3 or newer.
Leave this page open for the upcoming steps!
Install the downloaded package on your computer and open the PrusaSlicer app.
PrusaSlicer is part of the Drivers package. It includes the firmware upgrade tool. The Drivers package also includes some sample objects to be printed.
PrusaSlicer setup for MMU3
PrusaSlicer setup for MMU3
PrusaSlicer setup for MMU3
Open the PrusaSlicer Assistant / Wizard. (Configuration > Configuration Assistant > Prusa FFF)
Find the MK4 Family and make sure that Original Prusa MK4 MMU3 option is selected.
The default nozzle is 0.4mm from factory.
Click Finish to close the Wizard.
In Printer: menu, select the MMU3 printer profile for future slicing.

Please be aware that the MMU3 on MK4 IS NOT COMPATIBLE with older PrusaSlicer profiles or G-codes for MMU2, MMU2S, or even MMU3 + MK3S+ or MK3.5.

Using an incompatible G-code file on the MMU3 + MK4 could lead to a failed print or potentially damage the printer!

Firmware files download
Firmware files download
You will need to update both the firmwares for the printer as well as the MMU unit. Use just the newest firmware versions together.
Please refer to the MMU3 Firmware Compatibility article to find out exactly which firmware version you need.
Head back to Help.Prusa3D.com
Download the lastest Firmware package for your printer model.
Firmware Upgrade: Printer
Firmware Upgrade: Printer
Firmware Upgrade: Printer
IMPORTANT!!! Before you proceed further; There are two firmware files. One is for the printer. The other one is for the MMU3 unit. Both needs to be flashed to the respective device.
Printer’s firmware - .bbf file
for the MK4 control board: 
(e.g. MK4_MK3.9_firmware_6.0.0.bbf)

Update the printer’s firmware. First, transfer the firmware file onto a USB drive.

Turn on the printer and connect the USB drive into it. Press the RESET button to restart it. Then, select the FLASH option on the screen to begin the update.
MMU3 control board firmware:
(e.g. MMU3_FW3.0.3+896.hex)
This firmware update must be applied directly to the MMU unit using a computer. We will flash the MMU unit firmware in the upcoming steps.
Turning the MMU on
Turning the MMU on
Turning the MMU on
After finishing the firmware update, make sure there are no filaments loaded neither in the extruder, or in the MMU unit.
Navigate to the LCD menu > Settings > MMU

and make sure the MMU is turned on.
This option not only turns on the MMU functionality in the firmware, but also turns on the power for the MMU unit, which is necessary to do a FW update.
From now on, the reset button on the printer resets also the MMU unit. Wait for a while, the MMU unit will go through the self-test routine. (accompanied by flashing LED lights on the MMU unit) Wait until it boots up properly, before issuing any commands to the printer.
Since you've converted the extruder to the MMU version, when prompted to reconfigure the filament sensor's behavior, which will appear immediately, choose 'Continue'.
MMU3 Firmware flashing (part 1)
MMU3 Firmware flashing (part 1)
MMU3 Firmware flashing (part 1)
The MMU3 firmware file needs to be flashed into the MMU unit itself. Find the microUSB connector on the right side of the MMU3 unit.
Connect the unit to your computer using the bundled microUSB cable.
On your computer, select the appropriate MMU firmware file compatible with your printer model.
MMU3 Firmware flashing (part 2)
MMU3 Firmware flashing (part 2)
MMU3 Firmware flashing (part 2)
MMU3 Firmware flashing (part 2)
Open PrusaSlicer and select Configuration ->Flash Printer Firmware from the top menu.
Hit Browse and select the MMU3 firmware image file on your computer.
(e.g. MMU2S_MMU3_FW3.0.3+895.hex)
Serial port should be auto-detected.
Hit Rescan if your printer is not listed in the Serial port: column
Hit the Flash button.
Wait until the Flashing Succeeded! message appears.
After the flashing finishes, disconnect the USB cable.
In case of any issues with flashing the firmware please visit our troubleshooting article.
Gears calibration
Gears calibration
Gears calibration
Now, we need to calibrate the planetary gearbox in the Nextruder.
Go to the Home screen and navigate to Control -> Calibrations & Tests, scroll down and select Gears Calibration.
Once you get to the Gearbox Alignment part, select Continue and follow the on-screen instructions.
Gearbox Alignment
Gearbox Alignment
Gearbox Alignment
Gearbox Alignment
During the Gear calibration process, you will be prompted to:
Undo the idler lock (swivel). Make sure it is in the open position - lifted up.
Loosen the three screws on the front of the gearbox by 1.5 turns.
The printer will go through the automatic gearbox alignment. This process can’t be seen from the outside.
Once prompted, tighten the three screws in the indicated pattern.
MMU Filament sensor calibration
MMU Filament sensor calibration
MMU Filament sensor calibration
MMU Filament sensor calibration
When the Gearbox Alignment is complete, you should be prompted to continue to the filament sensor calibration.
There should be no filament inside the extruder before the calibration process starts. 
Make sure the idler lock (swivel) is closed.

During the filament sensor calibration, you will need to use a short piece of filament. Prepare a filament and select Continue.

Don’t insert the filament before being prompted to do so!
Once prompted to, insert the filament.
After successfully calibrating the filament sensor, remove the filament from the extruder.
Footer adjustment
Footer adjustment
Footer adjustment
Footer adjustment
Turning on the MMU unit automatically displays the filament sensor and Finda sensor information on the status bar on the display. If for some reason this information is not displayed or you want to adjust the order, proceed as follows.
On the printer, visit the Settings > User Interface > Footer.
Make sure there is Filament sensor (FSensor) selected in any of the fields.
Make sure there is SuperFINDA sensor (Finda) selected in any of the fields.
You will see the respective symbols and sensor values displayed on the bottom of the screen.
The sensor values are also shown in the Info > Sensor Info menu.
SuperFINDA sensor calibration info
SuperFINDA sensor calibration info
SuperFINDA sensor calibration info
SuperFINDA sensor calibration info
Good! After calibrating the filament sensor in the extruder, we can move on to calibrating the SuperFINDA sensor inside the selector on the MMU unit.
In the next step, we will adjust the sensor's position and check if it detects the filament correctly.
It is EXTREMELY important that both the filament sensor inside the extruder and the SuperFINDA sensor work reliably and provide accurate readings. Otherwise, you will have trouble with the device.
There is an inspection window on the side of the selector where you can observe the SuperFINDA's position. It is a good starting point to line up the bottom of the SuperFINDA probe with the top of the inspection window when looking from the selector motor side.
If there is a filament in the selector, the steel ball is risen and should be detected by the SuperFINDA sensor. The distance between the ball and the sensor is what must be perfectly calibrated.
SuperFINDA calibration
SuperFINDA calibration
SuperFINDA calibration
SuperFINDA calibration
Take a piece of filament with a sharp tip and insert it into the selector through the brass threaded opening on the front.
Take a look at SuperFINDA from above and watch for the little red light inside the sensor to turn off when the filament raises the steel ball inside.
Red light = no filament detected = FINDA 0 / OFF

No light = filament detected = FINDA 1 / ON
If the light is still on, lower the SuperFINDA slightly.

If the light doesn't go on, raise the SuperFINDA probe by releasing the screw by its side, moving the probe, and tightening the screw back up.
Watch the sensor readings on the LCD (Info > Sensor Info -> FINDA ) Note, there is a slight lag in the sensor's readings on the LCD; proceed slowly.
Keep repeating the test by inserting and removing the filament. Watch the values on the LCD. Adjust the SuperFINDA height accordingly until you get reliable readings from the sensor each time you insert and remove the filament.
Error code details (Part 1)
Error code details (Part 1)
Later on, an MMU error screen will show up if something goes wrong during the operation. See the example image; the first line describes briefly, what's the error about.
prusa.io/04101 is a web address, where you can view a detailed article about the exact issue, and how to fix it.
The status of the filament sensor is always displayed in the Footer section of the error screen to assist in diagnosis.
Adjacent to it, you will find the status of the Finda sensor.
(Note the FINDA status reading on the LCD has a slight delay.)
Error code details (Part 2)
Error code details (Part 2)
Error code details (Part 2)
The bottom line are the solution buttons. Some errors have multiple solutions.
You can also visit a detailed error description page via the QR code.
MMU unit being in an error state is also indicated by its LED lights flashing.
While in an ERROR state, the buttons on the MMU unit can be used to resolve the error too.
The middle button usually replicates the LCD solution buttons function.
Note, if the MMU unit is in IDLE state, the buttons have a different functions; For example; If there is no filament loaded, the side buttons can be used to move the selector right and left. But more on that later.
Fittings INFO
Fittings INFO
Fittings INFO
Fittings INFO
On the MMU, the PTFE tube that guides the filament to the printer is secured using FESTO pneumatic fittings.
Various versions of these fittings have been used in MMU units or with other Prusa products shipped before April 2024.
However, the MMU3 on the MK4 printer requires the latest evolution of the fitting, which has an internal diameter of 2.6mm.
FESTO fittings appear identical from the outside. Be careful not to mix old with new ones.

Using an incorrect version of the fitting on the MK4 can lead to the printer malfunctioning. Ensure you use only the fitting provided in your MMU3 MK4 package to avoid any issues.
MMU-to-Extruder PTFE tube parts preparation
MMU-to-Extruder PTFE tube parts preparation
MMU-to-Extruder PTFE tube parts preparation
For the following steps, please prepare:
360x2.5mm PTFE tube (1x)

The PTFE tube bundled with the MMU3 for MK4 has an internal diameter of 2.5mm. In case you are upgrading from the 2mm ID MMU2S tube, and you have trouble distinguishing between the old and the new one, try comparing the internal diameter of the two. See the second picture. The tube on the left is the new one.

A 2.5mm ID PTFE tube is required for the MMU3.
FESTO fittings (2x)
MMU-to-Extruder PTFE tube
MMU-to-Extruder PTFE tube
MMU-to-Extruder PTFE tube
MMU-to-Extruder PTFE tube
Attach the Festo fittings onto both sides of the PTFE tube.
Push the PTFE tube fully in.
Quick tip: If you need to remove the PTFE tube from the fitting, press the blue collet in. While the collet is pressed, first press the PTFE tube in, then pull it out entirely.
Attach the PTFE tube onto the printer. One end goes onto the selector. The other goes onto the extruder. Tighten the fittings up using the Uniwrench.
Spoolholders setup
Spoolholders setup
Spoolholders setup
Congratulations! The hardest part is over.
The Buffer and spools setup in the picture is the one we will be trying to achieve. Arrange the spool holders and the buffer as seen in the picture.
Hook up the "printer holder" part on the buffer to the extrusion on the printer.
The PTFE tubes should go from the spoolholders to the buffer. Then, from the buffer to the back of the MMU.
Note the spool holder positioning. It is important that filament has as straight path as possible and that nothing interferes. PTFE tubes should not be bent too much. Otherwise, the filaments will jam.
There were multiple versions of the spool holder available with the MMU3. Refer to one of the pictures, depending on your spool holder version.
Spoolholder-to-Buffer PTFE tube
Spoolholder-to-Buffer PTFE tube
Spoolholder-to-Buffer PTFE tube
Spoolholder-to-Buffer PTFE tube
Connect the PTFE tubes from the MMU unit to the BOTTOM row of collets on the buffer, ensuring you match the numbering on both the buffer and the MMU unit.
Attach each end of the PTFE tube from the Buffer to the PTFE holder on each Spool holder.
Make sure each spool holder is hooked up to the corresponding filament position number. (marked 1 to 5 on the MMU unit and the buffer.)
There have been several versions of buffer parts available, which might look slightly different. However, the assembly process remains the same.
The MMU3 for MK4 necessitates the use of the latest version of the buffer components. If you're using an older version, it's essential to rebuild the device using the most recent version available.
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