Prusa Research i3 MK2.5S Multi Material Upgrade 2S User manual

ENG

Please always refer to http://www.prusa3d.com/drivers/
for an updated version of this 3D printing handbook (PDF download).
Translated versions of the handbook are available at:
Czech: www.prusa3d.cz/ovladace/
French: www.prusa3d.fr/drivers/
German: www.prusa3d.de/treiber/
Polish: pl.prusa3d.com/sterowniki/
Italian: www.prusa3d.it/driver/
Spanish: www.prusa3d.es/drivers-y-manuales/
Assembly manual is available at http://manual.prusa3d.com
Multi Material Upgrade 2S (MMU2S) is compatible only with Original Prusa i3 MK2.5S /
MK3S.
This handbook is based on the MMU2S firmware version 1.0.5 and MK3S/MK2.5S
firmware version 3.6.0. Using other (older) firmware versions may lead to incorrect
results. Please, update your MMU2S unit regularly.
USEFUL LINKS
● Official website: www.prusa3d.com
● Newest drivers: www.prusa3d.com/drivers
● Knowledge base: help.prusa3d.com
● E-shop: shop.prusa3d.com
● Slic3r PE @ GitHub: www.github.com/prusa3d
● MMU2S Objects: www.prusa3d.com/printable-3d-models/
Symbols used in this handbook:
Important notice, tip, hint or information that helps you print with ease.
Read carefully! This part of the text has the greatest importance - either for user
safety or for proper printer service.
Handbook version 1.0 from February 25, 2019 © Prusa Research s.r.o.
1

About the author
Josef Prusa (born Feb 23
rd
, 1990) became interested in the 3D printing phenomenon before
joining Prague’s University of Economics in 2009. At first, 3D printing was a hobby, a new
technology open to changes and improvements. This hobby soon became a passion and
Josef grew into one of the leading developers of Adrien Bowyer’s international, open source,
RepRap project. Today, you can see the Prusa design in different versions all around the
world. It is one of the most popular printers, and thanks to Josef Prusa’s machines, the
knowledge of the 3D printing technology significantly increased among the public.
Jo’s work on self-replicating printers (you can print the other printer parts with your printer) is
still ongoing. Currently, the Original Prusa i3 MK3S is on the market - the third and latest
iteration of the original 3D printer. It is constantly updated with the latest innovations, such as
the brand new Multi-Material Upgrade 2S, which you have just purchased.
Josef Prusa also organizes workshops for the public, participates in professional
conferences dedicated to the popularization of 3D printing. For example, Josef lectured at
the TEDx conference in Prague and Vienna, at World Maker Faire in New York, Maker Faire
in Rome and at the Open Hardware Summit hosted by MIT. In addition, Josef teaches
Arduino at Charles University and was a lecturer at the Academy of Arts in Prague.
In his own words, he imagines that 3D printers will be available in every home in the
not-too-distant future. “If anything is needed, you can simply print it. In this field, you just
push the boundaries every day... We're glad you're part of it with us!”

 
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Table of contents
About the author 2
Table of contents 3
1 About the product 5
2 Quick-start instructions 6
3 Placement and setup 7
4 Flashing the firmware 8
4.1 Flashing firmware on Windows 9
5 Initialization procedure 11
6 Loading/Unloading/Selecting/Ejecting filament 11
6.1 Loading all five filaments at once 12
6.2 Loading one of the filaments using the LCD Menu 12
6.3 Loading one of the filaments using the MMU control buttons 12
6.4 Ejecting filament 13
6.5 Load to the nozzle 14
6.6 Unload filament 14
6.7 F.I.N.D.A explained 15
7 Calibration 15
7.1 IR filament sensor calibration 15
7.2 Calibrate the Z-axis 16
7.3 First Layer Calibration 17
7.4 Individual filament calibration 19
8 First Print 19
9 Printing in Multi Material Mode 20
9.1 Importing objects into Slic3r PE - STL, 3MF, AMF 20
9.2 Setting up colors 21
9.3 Slicing a multi-material object 22
9.4 Smart wipe tower 22
9.4.1 Wipe tower placement 22
9.4.2 Purging volumes 23
9.5 Wipe to infill 25
9.6 Wipe object 26
9.7 Supported Materials 27
9.8 Soluble Supports 27
9.8.1 Soluble support interface only 27
9.8.2 Completely soluble supports 28
9.9 Power panic support 28
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10 Printing in Single Mode 29
10.1 Colorprint 29
10.2 SpoolJoin 30
11 Handling 30
11.1 Mounting/Unmounting the MMU2S unit 30
11.2 Transporting the printer 31
12 Menu structure 32
13 Troubleshooting 34
13.1 MMU load failed - Blinking red LED 36
13.2 MMU needs user attention - Blinking red LED 38
13.3 All five LEDs blinking red 39
13.4 All five LEDs blinking red and green 39
13.5 Selector not moving 39
13.6 Loud clicking and idler unable to move freely 40
12.6 Filament not extruded during the print (missing layers) 41
13.7 Filament cannot go through the selector 41
13.8 Different filament tip shapes after the unload 42
13.9 F.I.N.D.A. does not detect the absence of the filament 43
13.10 Pulleys covered with filament dust 43
13.11 Can not update the MMU2S firmware 44
13.12 Crash detection 44
13.13 MMU2S factory reset 44
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1 About the product
Multi Material Upgrade 2S (MMU2S) is the latest revision of the Multi Material Upgrade 2.0,
originally released in 2018. Our unique multi-material printing solution is now compatible with
the Original Prusa i3 MK2.5S and MK3S 3D printers. Actually, MMU2 and MMU2S units are
almost the same, but the printer extruder is equipped with a new filament sensor
mechanism, which improves the reliability of the MMU2S unit. Thanks to the new type and
placement of the filament sensor, the MMU2S unit now receives feedback from the printer,
that the filament is loaded into Bondtech gears, making the complicated filament length
calibration obsolete. The MMU2S allows to load up five filaments simultaneously, which
enables the users to print even more complex and more colorful objects.
To unlock the maximum potential of your printer with the MMU2S, use our latest Slic3r Prusa
Edition slicing software. Offering a multitude of unique features, Slic3r PE is the go-to
solution for single and multi-material printing. The latest version introduces options such as
Wipe to infill or Wipe object and helps you save time and filament by utilizing various smart
routines. See the picture below to learn the official names for each MMU2S part. We will be
referring to these names in our guide.
Pict. 1 - The Multi Material Upgrade 2S
Pict. 2 - Location of the Reset button and of the micro USB port
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2 Quick-start instructions
We get it. You just assembled the MMU2S according to Assembly Guide, connected it to
your printer and now you are eager to start printing. :) But give us just a second! There’s a
couple of important steps you need to take before you can print your first multi-material
G-Code. Please note that these instructions are just a quick overview for users who already
have experience with 3D printing. We highly recommend reading the full instructions.
1. Download and install Drivers & Apps from www.prusa3d.com/drivers, update
printer firmware with Slic3r PE 1.41+.
2. Place filament spool holders next to the printer, the filament buffer behind the
printer and pull filament strings through the filament buffer in designed order.
3. Run Z-axis and First Layer calibrations.
4. Print your first test object!
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
3 Placement and setup
During filament changes, all of the filament is unloaded from the orange/white PTFE tube in
the front. Our new solution for dealing with retracted filament is a device called filament
buffer. The filament string creates a loop inside in order to prevent tangling. The setup
requires a space of at least 70 × 100 cm.
Pict. 3 - Filament buffer and spool holders setup
Basic steps for the arrangement of spool holders and the filament buffer:
1. Place the filament buffer behind the printer and attach it to the frame using the built-in
clips. Pay attention to the correct orientation of the filament buffer.
2. Attach PTFE tubes leading from the MMU2S unit in the designated order and secure
them with screws. See the Pict. 4.
3. Place the spool holders into two lines. The first line of spool holders should be at
least 20 cm from the filament buffer. Three spools are in the front line and two spools
between them in the rear line. Make sure, that the short PTFE tubes on the other side
of the buffer are pointing toward the spool holders (see picture above for reference)
4. Insert all filament strings through the filament buffer in the correct order (Pict. 5).
Avoid crossing the filament strings in the buffer. The string must go directly
through opposing holes on the same level (Pict. 5)
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
Pict. 4 - Order of PTFE tubes plugged to the buffer
Pict. 5 - Loading filament into the buffer
The placement described above is ideal as an initial setup and it is designed to save as
much space as possible. Alternatively, you can place the filament buffer and spool holders
behind the printer in line. There are other possible setups which you can try, so feel free to
experiment. But remember, that excessive bending of PTFE tubes causes high
resistance when loading filaments, which may result in various issues during printing.
4 Flashing the firmware
Before you start using the MMU2S, the printer’s firmware needs to be updated, otherwise,
the printer won’t communicate with the new unit. The MMU2S motherboard can be also
updated with a new firmware, which comes as a separate file. Please keep in mind that there
are slightly different flashing procedures for each board and that firmware files for the printer
and the MMU2S can be released independently. Drivers, apps and firmware files can be
downloaded from www.prusa3d.com/drivers.
WARNING: Do not disconnect the printer during the flashing process!
MAKE SURE YOU HAVE THE CORRECT FIRMWARE FILE FOR THE DEVICE
YOU WANT TO UPDATE

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4.1 Flashing firmware on Windows
1. Go to www.prusa3d.com/drivers and download the correct firmware for your printer
and/or MMU2S unit. Please note that there is a different firmware for each of our
printers and also a different type of firmware for the MMU2S.
2. Download the latest Drivers & Apps package from the same page and install it.
Make sure that Slic3r PE and Drivers are selected in the installation wizard.
3. Turn on the printer and wait for the initialization to complete.
4. Connect your printer to your PC using a USB cable. The type of USB cable and the
port depend on which type of firmware you want to flash.
a. TO FLASH PRINTER FIRMWARE: Use the standard procedure - connect the
printer mainboard (RAMBo) to your PC using a square-shaped USB-B 2.0
cable.
Pict. 6 - Connection of printer mainboard (RAMBo)
b. TO FLASH MMU2S UNIT FIRMWARE: Use a micro USB cable to connect
the MMU2S unit to your PC.
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Pict. 7 - Connection of MMU2S unit
5. Start Slic3r PE and select Configuration -> Flash Printer Firmware.
6. A new window will appear. Your printer should be detected in the ‘Serial Port’ box.
7. Click Browse to select the downloaded firmware file.
8. Press Flash! and wait for the process to finish.
9. Once the flashing process is finished, you can disconnect the printer from your PC.
Pict. 8 - Flashing new firmware
If the MMU2S unit is not recognized in the Device Manager, it’s possible that your
antivirus software has prevented the drivers from installing. Try installing them
manually from the destination directory - it’s C:\Program Files\Prusa3D\Rambo by
default. Also, you can try a different USB port or a micro USB cable.
To flash the firmware on MacOS or Linux, please download the latest version of Slic3r PE for
your system, then download the firmware files and follow the procedure described above.
Downloading and installing USB drivers is not necessary.
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The firmware for our lineup of printers is updated regularly. To ensure the best
possible experience when working with the printer and the MMU2S, it is necessary to
always use the latest firmware.
5 Initialization procedure
MMU2S unit is turned on simultaneously with the printer. After that, the homing procedure of
the idler body (extruder stepper) is started. Homing of the selector is started only when the
selector needs to move, not directly after being turned on. It means, that the initialization is
successful even in case the printer is turned on with a string of filament loaded in the nozzle
(which blocks the selector from moving)
During homing procedures, a repeated clicking can be heard. Don´t worry about it, it’s
a part of the procedure.
6 Loading/Unloading/Selecting/Ejecting filament
It’s essential that you cut the end of the filament as shown in the picture. The sharp
tip ensures proper insertion of the filament into the MMU2S unit. Also, try to
straighten the filament string with your fingers and make it as straight as possible.
You don’t need to preheat the nozzle as filament loading pushes the filament only to
the MMU2S unit. Insertion of the filament to the extruder is done automatically
during print.
Pict. 9 - Loading the filament
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6.1 Loading all five filaments at once
1. Go to LCD Menu - Load filament - Load All.
2. The selector will move to the first position, the first LED will start blinking red.
3. Push the filament to the first PTFE tube until it’s caught by the drive gear.
4. The filament will be pushed until it’s detected by the FINDA, then it will be retracted
from the selector, ready to be extruded when needed.
5. The LED indicator will turn green, signaling successful filament load, the selector will
move to the 2nd position.
6. Repeat the process for the remaining 4 filaments.
6.2 Loading one of the filaments using the LCD Menu
1. Go to LCD Menu - Load filament - Load filament 1/2/3/4/5.
2. The selector will move to the first position, the corresponding LED will start blinking
red.
3. Insert the filament into the correct PTFE tube and push it until it’s caught by the drive
gear.
4. The filament will be pushed until it’s detected by the FINDA, then it will be retracted
from the selector, ready to be extruded when needed.
5. The LED will turn green.
6.3 Loading one of the filaments using the MMU control buttons
1. Using the left and right control buttons, move the selector to the position
corresponding with the filament number you’d like to load.
2. Insert the filament inside the white PTFE tube and continue pushing it until it’s not
possible to push it any further.
3. Press and hold the middle control button for a few seconds.
4. The corresponding LED indicator will start blinking red.
5. Push the filament a little bit further into the white PTFE tube until it’s caught by the
extruder.
6. The LED indicator should turn green after a short while, signaling successful filament
load.
To unload filament simply pull the filament string from the white PTFE tube manually.
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Pict. 10 - Inside of the MMU2S unit with properly loaded filament
If you want to verify proper load of all five filaments before print, select LCD Menu - Load
filament - Load all. The MMU2S unit should quickly try loading and unloading all 5 filaments
one after another without any user interaction. After the last position, the LCD Menu should
quickly try loading and unloading all 5 filaments one after another without any user
interaction. Green LED should signal the success of load after each position.
6.4 Ejecting filament
Found in LCD Menu - Eject Filament - Eject Filament 1/2/3/4/5. It’s advised to run this
procedure after you use up filament scraps through the automatic depletion function (LCD
Menu - Settings - SpoolJoin [on/off] - 9.2 SpoolJoin). It allows you to remove the last
remaining piece of filament from the loading tubes after a filament spool is completely used
up.
Ejecting during the print:
1. Pause print via the LCD menu.
2. Select the Eject filament option and choose which filament you want to remove.
3. Then, the selector moves to the side and the filament string is ejected forward
(through the MMU2S unit).
4. Remove the rest of filament string and press the knob.
5. Select the Load filament option and insert a new filament string as usual.
6. Resume the print process.
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Pict. 11 - Ejected filament string is ready to be removed
Please note that the ends of the filament string must be straight in order to perform
the ejecting process correctly.
If the next filament slot is empty (filament string is not inside the MMU2S), the printer will ask
you to insert filament. This is indicated by a red LED light above the empty filament slot.
Press the middle button on the unit and the filament will be loaded. If the operation is
successful, the LED changes to red-green flashing. Continue the print by pressing the right
MMU2S button.
Please note that the nozzle has to be preheated in order to perform a filament
ejection procedure, because the filament may still be in loaded in the printer’s
extruder.
6.5 Load to the nozzle
It is possible to load the filament not only to the MMU2S unit but also all the way to the
printer’s nozzle. This is useful when printing older MK3/MK2.5 G-codes on a printer with the
MMU2S unit attached. So if you have an existing G-code for single-material printing, you
don’t have to re-slice it using the MMU2S Single Mode profile. Just select option Load to the
nozzle, select type of material, wait for the nozzle to preheat and select which filament you
want to load. Then simply print the single-material sliced G-code.
6.6 Unload filament
If the filament is loaded to the nozzle you can unload filament using this function. If the
nozzle is not preheated, the preheat menu will automatically appear. Select the filament
type, wait until the nozzle is preheated and confirm the unload by pressing the LCD knob.
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6.7 F.I.N.D.A explained
F.I.N.D.A is an older design P.I.N.D.A probe repurposed as a filament sensor. When the
filament is pushed through the selector, it raises a stainless steel ball. Its movement is
detected by the F.I.N.D.A. There is a small red LED light on the back of the probe. As soon
as the filament is detected, the light turns off.
When the filament is removed, the stainless steel ball falls back down. Please note that the
ball is pulled down by gravity, that means the filament sensor won’t work if you for whatever
reason turn the MMU2S unit upside down.
Pict.12 - F.I.N.D.A.
7 Calibration
Since the assembly of the MMU2S requires the printer’s extruder to be
disassembled in the process, it’s very likely that your printer’s Z-axis is now shifted.
It’s essential to re-calibrate the Z-axis and run the First Layer Calibration routine
before you start printing!
7.1 IR filament sensor calibration
The calibration of the IR sensor is based on the correct position of the chimney with the
sensor (IR sensor holder) on the extruder. Calibration is purely mechanical.
1. Before you start, make sure that the filament is not loaded!
2. Unscrew the Festo fitting on the extruder.
3. Open the LCD menu - Support - Sensor info and focus on IR value.
4. Loosen both M3 screws on the chimney (green marks).
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5. Move the chimney as far left as possible (red arrow) and make sure, that the IR
value is “0”.
6. Tighten the M3 screws on the chimney.
7. Prepare the smaller 1.5 mm Allen key which was included in the kit. Insert the Allen
key instead of the filament. Optionally loosen the extruder idler.
8. If IR sensor value is “1”, the calibration is done. If not, continue with the next
step.
9. Pull out the Allen key from the extruder.
10. Loosen the M3 screws on the chimney and move chimney little bit to the right side.
Make sure, that IR value is still “0” and continue with step 5.
Pict.13 - IR filament sensor calibration
7.2 Calibrate the Z-axis
In your printer’s LCD menu, go to Menu - Calibration - Calibrate Z and let the printer run
the calibration procedure. The procedure consists of raising and lowering the Z-Axis and
measuring 9 points on the print bed.
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Pict. 14 - Z calibration
Alternatively, you can run a “manual” Z-axis calibration. After you power on the printer, press
and hold the knob for 2 seconds. A new menu will be displayed, showing the letter ‘Z’ and a
number representing the current height of the Z-axis. Rotate the knob clockwise until both
ends of the Z-axis hit the top part of the frame.
Once the Z-axis is calibrated, you can proceed with the First Layer Calibration.
7.3 First Layer Calibration
1. Load a PLA filament into at least one MMU2S slot.
2. Check if your printer’s print surface is completely clean. Please refer to your model’s
handbook to learn more about surface maintenance.
3. On your printer, go to LCD Menu - Calibration - First Layer Cal.
4. The printer will warm up and ask you which filament should be used. Use the
on-screen menu to choose the desired PLA filament for the test.
5. The printer will probe the bed and start printing a zig-zag pattern on the print surface.
The nozzle must not by any means touch the printing surface.
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Pict. 15 - How to tune the nozzle height in real time during the test print. Note: -0.640 mm is
only for illustration.  Your setting will be different!
Observe the line which is being extruded on the print surface. A new menu will automatically
show up, with an option to tune the nozzle height in real time by turning the knob. The aim is
to adjust the nozzle height until the extruded plastic sticks nicely to the bed and you can see
that it is being slightly squished. The value should not exceed -2.000 mm. If you have to
adjust it more (e.g. -2.500), move the P.I.N.D.A probe slightly higher. Please refer to
our knowledge base in case the P.I.N.D.A probe needs to be realigned.
Pict. 16 - The properly-tuned first layer
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If your printer was working without any issues before adding the MMU2S unit, these two
calibrations should be everything you need to start printing. In case you still have trouble
calibrating the first layer height, please refer to the printer’s handbook or our knowledge
base at help.prusa3d.com.
7.4 Individual filament calibration
Information for advanced MMU2 users, who already performed filament
length calibration before: although you can enter the service menu and run
Individual filament calibration procedure, there is no reason to do it anymore.
The length of the filament is automatically controlled thanks to the new IR
filament sensor.
The only reason to run the calibration is in case you have changed the length of the
front PTFE tube between the extruder and the MMU2S unit. With the calibration, the
filament loading will be faster. In that case, please refer to this manual:
https://manual.prusa3d.com/Guide/Service+menu+-+Individual+Filament+Calibration/
842
8 First Print
First Print checklist:
✔ MMU2S Unit attached
✔ New printer firmware flashed
✔ Spool holders and the filament buffer are correctly placed
✔ Filaments loaded
✔ Performed Filament, Z-Axis, and First Layer calibrations
For your first print, we recommend using one of our G-codes.
If you have installed the latest driver package with the MMUS2 option selected, you can
use the ‘3D Objects’ shortcut on your desktop that will take you to a folder containing
MMU2S objects and G-codes.
Place the desired G-code(s) on your printer’s SD card, insert it into your printer’s SD card
slot and select the object to print in LCD Menu - Print from SD Card. Wait for the printer to
start the process.
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