Original Prusa i3 MK3S With MMU2S Review

I have to be careful with this review. LOL. Many of you know that I am an official BETA tester for Prusa Research. I assure you I don’t get any form of compensation for this review. Yes, I am a huge fan of the Prusa brand and that obviously has a reason. Josef Prusa and his incredible team create wonderful 3D printers. They even have there own in-house filament production facility where they create some of the very best filaments on the planet. I think that is something we can only applaud.

I did visit Josef Prusa (and my buddy Jennes) just last year. We had had an amazing time there. But enough of this, time to talk about my Original Prusa i3 MK3S with MMU2S (Multi-Material Upgrade v2S).

Original Prusa i3 MK3S

The Original Prusa i3 MK3S is the successor of the award-winning Original Prusa i3 MK2 3D printer. It has a newly designed extruder with Bontech drive gear, many sensor upgrades, and a new magnetic MK52 heatbed with replaceable PEI spring steel print sheet which is available in both smooth PEI and textured powder coated PEI. Frame stability has improved through aluminium extrusions for the Y-axis. It has a power panic feature which gives the ability to finish active print jobs after a power loss. The EINSY Rambo motherboard with super silent Trinamic2130 drivers also is a nice piece of technology.

It is very silent during operation even in “normal” printing mode. The board can even detect skipped layers and layer shifting so failed prints are “almost” a thing of the past. One of the most important advantages of buying an Original Prusa 3D printer is that you will also have access to great customer care directly from Prusa Research technicians and also the ever-growing online Prusa Community. There are so many experienced users from all around the world. And many of them are able and willing to help out with any questions or problems. The connected MMU2S (Multi-Material Upgrade 2S) gives you the ability to print models with up to 5 colours, and/or materials.

multi material Anatomic Heart in five colors using the MMU2S
Just finished a multi material Anatomic Heart in five colors using the MMU2S.

Beta Testing For Prusa Research

As I told earlier in this post, I am an official “external” BETA tester for Prusa Research which means that I test many different aspects of their printers. I test normal customer experience, new 3D printers (SL1/MINI), new Firmware versions, print settings, and so much more. I can say I am an experienced Prusa printer user and tested many different configurations.

The Original Prusa i3 MK3S performs better than any printer I used in the price range below €1000,-. Because it can print in temperatures of almost 300 degrees Celcius it can print most materials available today. Some materials tend to behave better when printed in an enclosure. Most common materials like PLA and PETG perform great without enclosure on the MK3S. I also print many hard to print materials such as carbon-filled PA and architectural stone- or clay infused filaments so I needed to create an enclosed environment form my MK3S.

Prusa IKEA Lack Enclosure v2

Luckily there is a cheap solution for the i3 MK3S with MMU2S. You can download files from the PrusaPrinters site. After that, you’re able to print the parts for the Prusa IKEA Lack enclosure v2 (for MMU2S). You can actually build a good enclosure out of a cheap IKEA Lack table. Just add 5 acrylic sheets and some PETG printed parts. It looks great and works amazingly well too. The temperature in my printer room is around 19 degrees Celcius most of the time. Sometimes it reaches much higher or lower temperatures. When my enclosure is completely closed off the level is around 33 degrees Celcius inside it with the build plate set at 95 degrees. This is perfect for PA and other materials prone to warping and cracking.

It’s All About Proper Calibration

Most of the time when I’m printing multi-material objects I’m using PLA. PLA is very easy to print on any 3D printer. It is available in many colours and performs very well in the MMU2S unit. Some users are experiencing issues when using the MMU. In my opinion, it really is a matter of proper calibration. When following the steps in the 3D Printing Handbook by Josef Prusa and using the advised (and calibrated) filaments you are able to achieve amazing things on your Original Prusa i3 MK3S with MMU2S.

How Does The MMU2S Work?

The MMU2S works as follow. You slice your 5 colour model using PrusaSlicer. Let’s say you’ve imported a model with 5 different colours. You can import the model in PrusaSlicer as 5 separate files. After this, the software will ask you if you would like to handle the model as a multi-material print and for this example, we choose yes. After this, it’s time to feed your 5 prefered colours of PLA through the 5 PTFE tubes and the filament buffer. Your Original Prusa i3 MK3S 3D printer has one single extruder.

The MMU unit has a selector that moves left and right to select one of the 5 inputs. Ones the correct input is selected the unit pushes the material via a single tube to the extruder of the iMK3S. A sensor picks up when the filament hits the extruder gear and takes over from the MMU unit. It first wipes previously used material out the nozzle printing a purge block. When the new colour comes out and resumes printing the chosen section of the model. To do all this, the MMU2S unit uses 3 stepper motors and an extra controller board connected to the EINSY Rambo board of your printer.

RepBox For The MMU2S

Prusa style RepBox by Repkord
Source: Repkord.com

Another cool thing to mention is that Pooch from Repkord was a guest during last weeks PrusaLive YouTube episode. Jo Prusa asked him about the possibility to include the handy RepBox as an option in the Prusa webshop. Pooch from Repkord loved the idea so we might see an Original Prusa RepBox in the official Prusa webshop soon. It would be a nice addon for MMU(2S) users. The RepBox is perfect to house your filaments for single extruder 3D printers too. I am going to buy one the day it gets released.


I made many incredibly beautiful prints using the Original Prusa i3 MK3S with MMU2S by Josef Prusa. One thing to consider before buying the MMU2S is that you really need to be a bit more experienced user that knows how to fix issues for this upgrade to work properly. Jo Prusa is very honestly telling this on his website and social channels. Another “downside” for some makers might be that your print time will increase with multi-material models. This is because of all the tool changes and colour wipes the 3D printer needs to do.

And yes, these colour changes cost a lot of material as well. There are ways to minimise the amount of waste by using features as “wipe into infill”. There will always be waste material when printing multi-material objects in this manner. Sometimes the weight of the purge block is two times the amount of the printed item itself. That only is in extreme circumstances making thousands of tool changes. You sometimes need all 5 colours in one layer. If that is the case from the bottom to the top of the model it costs more material. These really are the only downsides of the MMU2S I can think of.

For me, the Original Prusa i3 MK3S with MMU2S is still the number one choice for multi-material 3D printing. PrusaSlicer and the Hardware work together seamlessly. The Firm- and Software are updated continuously. 24/7 Customer Service and Support is the best I’ve seen. And the Prusa Community is always there to help out and is rapidly growing.

When buying an Original Prusa i3 MK3S, you have two options. You can buy the 3D printer built and tested by Prusa technicians. There is also the option of purchasing the kit version. Building the printer yourself is great fun. Also, you will get to know your i3 MK3S in the best possible way. The incredibly detailed (online) manual makes the assembly super easy.

The MMU2S unit is only available in kit version. Assembly of the MMU2S is not very hard. It also comes with detailed manual and instructions.

A nice selection of prints made with the Original Prusa i3 MK3S with MMU2S.

Are you considering buying an Original Prusa i3 MK3S printer with MMU2S, just the printer or a different Original Prusa product? Then please use my affiliate link to the ONE AND ONLY OFFICIAL Prusa Research webshop! In this way, you are supporting me big time and this helps me a lot in future projects.

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