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1. Introduction

1. Introduction
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Last updated 9 days ago
1. Introduction
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Step 1 MMU History and Printer Compatibility

MMU History and Printer Compatibility
MMU History and Printer Compatibility
MMU History and Printer Compatibility

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.

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

It used four separate extruders feeding one nozzle.

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

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

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

And finally, the current model:
MMU3 for MK3S+, MK4 (2023-now)

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

Step 2 Supported printers

Supported printers
Supported printers
Supported printers
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
(support for MK4 will be announced later on)

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 Firmware 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

Tools required
Tools required
Tools required
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 高解像度の画像を見る

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

Labels guide
Labels guide
Labels guide
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 ヒント: ナットを差し込む

ヒント: ナットを差し込む
ヒント: ナットを差し込む
ヒント: ナットを差し込む
ヒント: ナットを差し込む

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.

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

Printed parts
Printed parts
If you prefer to print the plastic parts yourself, use the pre-sliced G-codes and print all the required parts before proceeding with the assembly.

The printed 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 of printing it yourself.

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.
The MMU3 printable parts will be available at prusa3d.com/prusa-i3-printable-parts/

The recommended material is PETG. 

If you opt to slice the parts yourself, use PrusaSlicer with 0.2 mm layer height, GRID infill at 20%. No supports are required. 

Step 10 Prepare your desk

Prepare your desk
Prepare your desk
Clear your workspace. Make sure you have enough room. A nice clear flat workbench will get you the results you are aiming for.
OK, we are ready. Let's start!
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