1. Introduction

Relevant for:

MMU3

Last updated 6 days ago

Difficulty

Very easy

Steps

Available languages

Step 1 MMU History and Printer Compatibility

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Welcome to the MMU3 assembly 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, MK3.9 and MK4 (2023-now)

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

⬢Original Prusa MK4 / MK3.9

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

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

Step 3 Disclaimer

⬢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 the importance of carefully following each and every step.

Step 4 Tools required

⬢The required tools 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 chapters, as an extra, we advise considering:

- a measurement tool; a caliper or digital caliper would work the best. Or - you can print one.

- Flush cutters might come in handy during the assembly too.

Step 5 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 6 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 7 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 8 Pro tip: inserting the nuts

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Some parts require you to use an Allen key at an angle to tighten a screw.

Even though the key is angled, make sure the screw is perfectly perpendicular to the thread while tightening it. If it is hard to turn, release the screw fully, re-align it, and start tightening it from the beginning to avoid cross-threading it!

⬢For deep openings, use a long screw such as the M3x30 as a handle.

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If a hex nut won't fit in: use a screw with a thread along its entire length (typically: M3x10, M3x18) and screw it from the opposite side of the opening to drive the nut in.

Step 9 Printed parts

⬢If you ordered the MMU3 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 10 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!