This manual guides you through upgrading your Original Prusa MK4 to MK4S or MK3.9 to MK3.9S, with all instructions applying to both upgrades.
NOTE: The provided pictures feature the MK4S, so you may notice MK4S logos across the manual.
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1. Introduction
Menu
- Original Prusa MK4/MK3.9 to MK4S/MK3.9S upgrade
- 1. Introduction
- 1. Upgrade manual info
- 2. Preparing the upgrade kit
- 3. What will be upgraded?
- 4. Getting the necessary tools
- 5. Labels guide
- 6. Printed parts - versioning
- 7. We are here for you!
- 8. Pro tip: inserting the nuts
- 9. View high resolution images
- 10. Important: Electronics protection
- 11. How to successfully finish the assembly
- 12. Prepare your desk
- 13. Parts no longer needed
- 14. Cleaning the hotend
- 15. Reward yourself
- 16. Preparing the printer
- 17. MMU3 preparation
- 18. Additional Information
- 2. Upgrading the Y-axis
- 3. Upgrading the xLCD
- 4. Upgrading the Nextruder
- 4B. Upgrading the Nextruder (MMU3)
- 5. Upgrading the connectivity
- 6. Preflight check
- Manual changelog
1. Introduction
⬢Please prepare the upgrade kit received from Prusa Research.
MMU3: This manual also includes instructions for MMU3 owners. These instructions are separated and indicated in advance.
⬢MK4/MK3.9 upgrade to MK4S/MK3.9S includes changes to:
⬢New Y-axis tensioning mechanism printed from PCCF material for greater heat resistance.
⬢New injection molded xLCD cover.
It is compatible with certain xLCD board versions. In case of incompatibility, a new printed cover will be provided—more information is in the relevant chapter of the manual.
⬢New 360° cooling on the Nextruder.
⬢New high-flow Prusa Nozzle CHT.
⬢Improved Wi-Fi antenna.
⬢Brand new NFC antenna.
⬢Use the tools that came with your MK4/MK3.9 printer.
⬢For this upgrade you will need:
⬢2.5mm Allen key
⬢Torx key T6
⬢Torx key T10/8
⬢Wrench 13-16
⬢Universal wrench
⬢All the boxes and bags including parts for the build are labeled.
⬢The labels include the list of contents and part count.
⬢You can download a Cheatsheet with 1:1 fastener drawings from our site prusa.io/cheatsheet-mk4s. Print it at 100 %, don't rescale it, otherwise, it won't work.
For PRUSA veterans: Fasteners are divided into individual bags according to its type. Not into packages for individual chapters, as it was with previous printers.
⬢Most of the 3D printed parts are marked with their version.
⬢E, F and Gx series (e.g. E1) - those parts are printed on Prusa Research farm and are distributed with the kit.
⬢R, S and Tx series (e.g. R1) - those parts are available for download at prusa.io/printable-parts-mk4s. They are identical to the factory ones.
In case you have issues while assembling the printer with the certain printed part, please try to find this label and tell it to our support team.
⬢Lost in the instructions, missing screw or cracked printed part? Let us know!
⬢You can contact us using the following channels:
⬢Using comments under each step.
⬢Using our 24/7 live chat here at help.prusa3d.com
⬢Writing an email to [email protected]
⬢3D printed parts are very precise, however, there still might be a tolerance in the printed part and the same goes for the size of the nut.
⬢Therefore it might happen, that the nut won't fit easily in or might be falling out. Let's see, how to fix it:
⬢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. While tightening the screw, the nut will be pulled in. Remove the screw afterwards.
⬢Alternative option: you can use X-holder tool included in the package. Insert any screw (typically: M3x10 or M3x18) and screw the nut fully on the tip of the thread. Push the nut into the printed part and remove the screw with X-holder.
⬢Nut keeps falling out: Use a piece of tape to fix the nut temporarily in place, as soon as you insert the screw in, you can remove the tape. Using glue isn't recommended as it can partly reach into the thread and you won't be able to tighten the screw properly.
⬢Every time we recommend using the "screw pulling technique", you will be reminded with Joe's avatar ;)
Parts in the pictures are used as an example.
⬢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 button ("View original") in the top left corner.
WARNING: Make sure to protect the electronics against electrostatic discharge (ESD). Always unpack the electronics right before you need them!
⬢Here are some tips to prevent damage to the electronics:
⬢Keep the electronics inside the ESD bag right until you are asked to install them.
⬢Always touch the sides of the board only while handling it. Avoid touching the components on the surface.
⬢Before you touch the electronics use any conductive (metal) structure nearby to neutralize the possible static charge from your hands.
⬢Be extra cautious in rooms with carpets, which are often a source of electrostatic energy.
⬢Clothes made of wool or certain synthetic fabrics can easily gather static electricity too. It is safer to wear cotton clothing for the assembly.
To successfully finish the upgrade please follow all these:
⬢Always read all the instructions at the current step first, it will help you to understand what you need to do. Don't cut or trim unless you are told to!!!
⬢Don't follow pictures only! It is not enough, the written instructions are as brief as they could be. Read them!
⬢Read the comments from the other users, they are a great source of ideas. We read them too and based on your feedback improve the manual and the entire assembly.
⬢Use a reasonable force, the printed parts are tough, but not unbreakable. If it doesn't fit, check your approach twice.
⬢Most important: Enjoy the build, have fun. Cooperate with your kids, friends or partners.
⬢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.
⬢Certain parts will no longer be needed for this upgrade. A list of these parts is provided at the end of each chapter.
Keep all parts until you complete the chapter, then discard the unnecessary items according to the list provided at the end of that chapter.
Tip: You can repurpose any removed electronic parts for your future projects.
⬢You may also have leftover fasteners, with the quantity varying depending on your MK4 version.
CAUTION: Always compare the new parts with the provided pictures to avoid confusing them with the old parts.
NOTE: For visually similar parts, we will always notify you when new parts are involved.
WARNING: The hotend and heatbed are very HOT. Do not touch these parts!!!
⬢The upgrade includes a replacement CHT nozzle. Ensure the hotend is clean before the exchange, as a dirty hotend can make it difficult to remove the installed nozzle.
If you have a Prusa hotend sock on the hotend, remove it.
⬢On the printer screen, go to Control -> Temperature -> Nozzle Temperature and using the knob set 250°C.
⬢Wait at least 5 minutes. The remains of the filament must be warmed up slightly so that they can be removed more easily.
⬢Using the brass brush, carefully clean the heaterblock and the hotend from the filament residue. Avoid contact of the brush with the hotend cables, as this could cause a short circuit.
⬢When the heaterblock and the hotend are perfectly clean, cool down the printer. On the screen, navigate to Preheat -> Cooldown.
Wait until the hot parts are cooled down to ambient temperature. It takes approximately 10 minutes.
⬢Based on the feedback, building the MK4S/MK3.9S printer is even more enjoyable compared to the MK4. However, you should still treat yourself for every finished chapter. Look in the box and find a bag of Haribo Bears.
The biggest issue from our experience (MK4, MK3S+, MK3S, MK3, MK2S, ...) is inadequate bear consumption. Many of you didn't have enough gummy bears for all chapters, some even ate them all before they started!
⬢After years of thorough scientific research, we came to a solution => At the end of each chapter, you will be told a specific amount of bears to consume.
⬢Eating an incorrect amount than prescribed in the manual might lead to a sudden boost of energy. Please consult a professional in the closest candy store.
Hide the Haribo for now! From our experience, an unattended bag with sweets will suddenly disappear. Confirmed by multiple cases all around the World.
Before you start with upgrading your printer, do the following:
⬢Unload filament from the printer.
⬢Take off the spool holder.
⬢Remove the print sheet.
⬢Move the X-axis to the center of the Z-axis.
Turn the printer OFF and unplug the power cord.
⬢Remove the USB stick from the printer.
This step is only for the MK4/MK3.9 + MMU3 users!
⬢Disconnect the PTFE tube fitting from the Nextruder.
⬢Remove the MMU3 unit from the printer and set it aside. We will re-install it later on.
⬢Carefully cut off the zip-tie holding the MMU-Printer cable on the MMU unit.
⬢Disconnect the cable from the MMU unit.
This information applies to users planning to install accessories, such as the Original Prusa Enclosure, or upgrades like the MMU3.
⬢Before installing any accessories, it's essential to assemble and test your printer according to the instructions. Once the printer is fully functional, follow the separate MMU3 or Enclosure assembly manual to modify the printer for installation.
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