1. Introduction

Relevant for:

MMU3

Last updated a month ago

Difficulty

Very easy

Steps

Available languages

Step 1 MMU History and Printer Compatibility

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Welcome to the MMU3 guide! There were several generations of the Original Prusa Multi-Material printing solution. Verify you are looking at the correct guide for your MMU unit and your printer.

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MMU1 for MK2 and MK2S printers (introduced in 2016-2018)

It used four separate extruders feeding one nozzle.

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MMU2 for MK2.5 and MK3 (2018-2019) Five filaments feeding one direct-drive extruder.

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MMU2S for MK2.5S, MK3S, MK3S+ (2019-2023)

Introduced a chimney on the extruder with the IR-filament sensor.

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And finally, the current model:
MMU3 for MK3S+, MK3.5/S, MK3.9/S and MK4/S.

MMU3 is the one we will be dealing with in this guide.

Step 2 Supported printers

⬢Original Prusa Multi-Material MMU3 is currently officially supported only in combination with these printer models:

⬢Original Prusa i3 MK3S+

⬢Original Prusa MK3.5/S

⬢Original Prusa MK4/S or MK3.9/S

If you have an older machine like the MK3 or MK3S, it is recommended to upgrade it to at least MK3S+ first.

For more info on Printer compatibility, visit the MMU3 Compatibility article.

Step 3 MMU3 + Enclosure

The MMU3 is also supported with the Original Prusa Enclosure.

⬢If you plan to use the MMU3 with the Enclosure, first assemble the printer with the MMU3 using this guide.

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Once you’ve completed the printer + MMU3 assembly, continue to the Enclosure assembly guide.

⬢Make sure your printer is fully assembled and works perfectly before you proceed to attach the MMU3 onto it. Make a few single material prints. If it has any issues, fix the issues first. Diagnosing printer issues can be harder with the MMU attached.

⬢As you embark upon the assembly process, we cannot stress enough the importance of carefully following each and every step.

Step 5 Tools required

⬢The tools needed for the MMU3 Kit assembly are available as an optional bundle.

⬢Needle-nose pliers (1x)

⬢Universal wrench (1x)

⬢Philips PH2 screwdriver (1x)

⬢Allen key 1.5mm (2x) the short and long one

⬢Allen key 2mm (1x)

⬢Allen key 2.5mm (1x) the short and ball-end long one.

For some steps, we recommend having the following extras:

- A measurement tool, preferably a caliper or digital caliper Or - you can print one.

- Flush cutters, which can be useful during assembly.

Step 6 View high resolution images

⬢When you browse the guide on help.prusa3d.com, you can view the original images in high resolution for clarity.

⬢Just hover your cursor over the image and click the Magnifier icon ("View original") in the top left corner.

Step 7 Labels guide

⬢All the boxes and bags containing the parts for the build are labeled.

⬢Most of the part drawings on the labels are scaled 1:1 and can be used to identify a part.

⬢You can download and 2D print a Prusa Cheatsheet with the 1:1 scaled fastener drawings. help.prusa3d.com/cheatsheet. Print it at 100 %, don't rescale it, otherwise, it won't work.

Step 8 We are here for you!

⬢Lost in the instructions, missing screw or cracked printed part? Let us know!

⬢You can contact us using following channels:

⬢Using our 24/7 live chat

⬢Or by writing an email to [email protected]

⬢Or, you can use the comments under each step.

Step 9 Pro tip: inserting the nuts

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During the MMU3 kit assembly, some screws require tightening with an angled Allen key. Ensure the screw stays perfectly perpendicular to the thread. If it’s difficult to turn, fully release it, realign, and start again to avoid cross-threading.

⬢For deep openings, use a long screw like the M3x30 as a handle to help position the nut.

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If a hex nut won't fit, use a fully threaded screw (e.g., M3x10, M3x18) and insert it from the opposite side to drive the nut into place.

Step 10 Printed parts

⬢If you ordered the MMU3 Kit without plastic parts, you will need to print them using the pre-sliced G-codes before you can proceed with the assembly.

The parts must be printed perfectly in order for the MMU3 to work correctly: no warping or lifted corners, stringing or other irregularities.

If you can’t guarantee the parts being flawless, get the MMU3 kit with the factory-printed plastic parts instead.

⬢In case some parts get broken during the assembly, you can reprint them. Please check all plastic parts before starting your build to make sure there are no issues.

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The MMU3 printable parts are available at Prusa3D.com Printables profile

More info is available at: Prusa3D.com/prusa-i3-printable-parts/

Step 11 Prepare your desk

⬢Tidy up your desk! Tidying up decreases the probability of losing small parts.

⬢Clear your workspace. Make sure you have enough room. A nice clear flat workbench will get you the results you are aiming for.

⬢Let there be light! Make sure you are in a well-lit environment. Another lamp or even an extra flashlight will probably come in handy.

⬢Prepare something to contain the plastic bags and the removed packing materials so you can recycle them afterwards. Make sure there are no important parts being discarded.

⬢OK, we are ready. Let's start!