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MK4/MK3S+ kit shipping from $50 (DHL)
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Original Prusa i3 MK3/S/+ to MK3.9 upgrade kit

MK3.9 contains everything from the MK4 except for the X/Y/Z motors (Nextruder motor is included). You will reuse the frame, PSU and motors from your MK3S+. And if you want, you can additionally buy the new precise MK4 motors (eliminate Vertical Fine Artifacts, 0.9° per step) and complete the upgrade to MK4 later.

 

Before you order the upgrade, please check which PSU your printer came with and which version of the heatbed connector is installed. This is important for correct compatibility with the upgrade. Depending on the selected options, we can send you additional components to ensure compatibility with the upgrade.

 
psu comparison foto

Which PSU does your printer have?

  • Black PSU - you are all good
  • Silver PSU - you will need to add a compatible wiring harness or a black PSU (in the configuration box above)
heatbed comparison foto

How many screws does your heatbed have?

  • 2+3 screws (power cable connected with screws) - you are all good
  • 2+1 screws (power cable soldered) - replacing the bed will be necessary
Be sure to choose the correct options in the top right menu before you place your order!

 
 

This product is supplied as a kit - you must assemble it yourself!

Printed parts are NOT included! Please print them before you disassemble your MK3S/+! The filament is included in the upgrade package.

Important: The black injection-molded spool holder is not part of the upgrade package. If your printer didn't come with it (early revisions of MK3), you can purchase it here.

Here is a closer explanation of the difference between the MK3.9 and MK4 upgrade packages: the only difference is in the stepper motors. The MK4 uses higher-precision stepper motors that help eliminate VFA (Vertical Fine Artifacts) – these are tiny surface artifacts that are visible if you closely inspect a printed object. In other words, the motors in the full MK4 upgrade are the cherry on top – if you’re chasing the highest possible level of quality, they will come in handy. But the MK3.9 upgrade is very close to that.



This product includes:

  • 32-bit xBuddy board (same as MK4)
  • Metal xBuddy case (and cover)
  • xLCD screen (same as MK4)
  • Nextruder parts (including E motor)
  • Cables for Nextruder, Heatbed, xLCD
  • Expansion joints for Heatbed
  • New belts for X & Y axes
  • Fasteners and other accessories
  • New rods and bearings for Z axis
  • Filament for printable parts

Parts kept from your MK3S/MK3S+

  • Frame and extrusions (new MK4 has just a different look)
  • PSU* (same wattage/voltage as MK4)
  • Heatbed MK52 24V (thermistor and power cables will be changed)
  • X/Y/Z motors
  • X/Y rods and bearings

*Please note that silver PSU will require a cable adapter. More information will be provided later.

 

MK3S/+ Upgrades Comparison

 MK3.5 upgradeMK3.9 upgradeMK4 upgrade

Build volume

250 x 210 x 210 mm | 9.84 x 8.3 x 8.3 in250 x 210 x 220 mm | 9.84 x 8.3 x 8.6 in250 x 210 x 220 mm | 9.84 x 8.3 x 8.6 in
MainboardCustom 32-bit xBuddy electronics with STM32Custom 32-bit xBuddy electronics with STM32Custom 32-bit xBuddy electronics with STM32
Stepper DriversTrinamic 2130Trinamic 2130Trinamic 2130
Stepper motorsRegular 1.8° X,Y stepper motorsRegular 1.8° X,Y stepper motorsPrecise 0.9° X,Y stepper motors (prevents VFA)
MMU3 support

Yes

Yes

Yes

Extruder electronics

No

Custom breakout board for connecting fans, thermistors and other parts.Custom breakout board for connecting fans, thermistors and other parts.
Filament pathAluminum heatsink, all-metal hotendAluminum heatsink, all-metal hotendAluminum heatsink, all-metal hotend
Drive system

Direct drive

Nextruder Planetary Gear System, 10:1 gearbox ratioNextruder Planetary Gear System, 10:1 gearbox ratio
First layer calibrationManual adjust ZFully automatic (thanks to the Load Cell sensor)Fully automatic (thanks to the Load Cell sensor)
Quick-Swap nozzle system

No

Yes

Yes

LCD screen3.5″ graphic 65k color screen3.5″ graphic 65k color screen3.5″ graphic 65k color screen
Bed calibration

Automatic, Mesh Bed Leveling

Automatic, Mesh Bed Leveling (only on print area)Automatic, Mesh Bed Leveling (only on print area)
One-click Printing

Yes

Yes

Yes

Status LEDs

Yes

Yes

Yes

Input shaper

Yes

Yes

Yes

Filament Sensor

Yes (IR)

Yes (built-in Hall sensor)Yes (built-in Hall sensor)
Loadcell sensor

No

Yes

Yes

Advanced sensors

3 thermistors + SuperPINDA, fan RPM sensors

Filament sensor, Loadcell sensor, Power panic, 4 high-precision thermistors (genuine Semitec) + fan motors RPM monitoringFilament sensor, Loadcell sensor, Power panic, 4 high-precision thermistors (genuine Semitec) + fan motors RPM monitoring

Power panic

Yes

Yes

Yes

Ethernet connection

Yes

Yes

Yes

Wi-Fi connection

Yes

Yes

Yes

Prusa LinkIntegratedIntegratedIntegrated
Print mediumUSB drive / LAN / internet via Prusa ConnectUSB drive / LAN / internet via Prusa ConnectUSB drive / LAN / internet via Prusa Connect

Firmware update interface

USB driveUSB driveUSB drive

Kit price

249 USD / 279 EUR (VAT incl.)499 USD / 549 EUR (VAT incl.)579 USD / 639 EUR (VAT incl.)
 Buy MK3.5 upgradeBuy MK3.9 upgradeBuy MK4 upgrade

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    Handbook (EN) (change)

    In stock

    Preparation time: 1-3 business days.

    $499
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