⬢The MMU3 unit should be placed in the middle of the top part of the printer's aluminum 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.

⬢Make sure the unit is in the middle of the frame. Once we engage the clamps, it won't move left and right as easily anymore.

⬢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.

⬢Take the Ext-cable-holder-a plastic component. There is a small part that needs to be breaked off in order to make space for the MMU cable. Remove the part using needle-nose pliers.

⬢Similarly, remove the break-off part on the Ext-cable-holder-b.

⬢Loosen the two M3x10 screws on top of the cable cover.

⬢Guide the MMU/Printer cable through the corresponding opening into the xBuddy box.

⬢Plug the MMU/Printer cable into the corresponding connector on top of the xBuddy board.

⬢Attach the cable-holder-b back onto the xBuddy box using two M3x10 screws.

⬢Insert two new zip-ties into the marked opening on the inside of the xBuddy box. Make sure the zip-ties wrap around the cable bundle.

⬢Attach the cable-holder-a part using two M3x18 screws. Make sure no cable is getting pinched.

To verify the remaining cable connections are connected properly, refer to the MK3.5 assembly guide

⬢Ensure all connectors in the cable bundle remain fully inserted.

⬢Wrap the zip-ties around the cable bundle and gently tighten. Cut off the remaining zip-tie.

⬢Align the xBuddy box cover with the xBuddy box and secure it with four M3x6 screws.

⬢Visit the MMU3 page on Help.Prusa3D.com

⬢Download the latest Drivers & Apps package.

⬢Leave this page open for the upcoming steps!

⬢Install the downloaded package on your computer and open the PrusaSlicer app.

⬢Open the PrusaSlicer Assistant / Wizard. (Configuration > Configuration Assistant > Prusa FFF)

⬢Scroll down to MK3.5 Family and make sure that the corresponding printer + MMU3 option is selected.

⬢Click Finish to close the Wizard.

⬢In Printer: menu, select the MMU3 printer profile for future slicing.

Note, the MMU3 on MK3.5 is reverse-compatible with the older MK3S+ MMU3 or MMU2S Slicer profile and G-codes - but not with the MMU2 profiles!

⬢Open up the firmware bundle you have downloaded earlier. Open one of the folders dedicated to the MK3.5 printer (marked by MK35)

⬢There are two firmware files in the folder. One for the printer, the other one for the MMU unit.

⬢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.

⬢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'.

⬢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.

⬢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. MMU3_3.0.0.hex)

⬢Serial port should be auto-detected.

⬢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.

⬢Using a 2.5mm Allen key, make sure the lock screw for the chimney is not tightened up. Don't remove it entirely. It holds the chimney together.

⬢Carefully tighten the calibration screw on the side so that the chimney moves all the way to the left.

⬢Tighten the calibration screw until the chimney moves all the way to the left.

⬢Insert a 1.5mm Allen key into the extruder. Don't push it all the way in yet.

⬢Go to Info > Sensor Info on MK3.5

The Fil. sensor should indicate value 0 / NINS when the Allen key isn't pushed all the way in so the idler door isn't tilted outwards.

⬢Now push the 1.5mm Allen key down until it reaches in between the Bondtech gears.

⬢The idler door on the right of the extruder should tilt outwards slightly simulating an inserted filament.

Please, repeat this check several times.

⬢Confirm the sensor works correctly: See the LCD again if the Filament sensor number

⬢When the sensor works reliably and correctly, please lock the chimney in place by tightening the lock screw from the top.

⬢After tightening the screw, verify the readings on the LCD are still correct when inserting and removing the Allen key.

⬢Good! You have calibrated your IR filament sensor. Now, 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.

⬢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.

⬢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.

⬢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.

⬢360x2.5mm PTFE tube (1x)

⬢FESTO fittings (2x)

⬢Attach the Festo fittings onto both sides of the new PTFE tube (4x2.5x360mm)

⬢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 Unikey.

⬢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.