United StatesOriginal Prusa i3 MK3/S/+ to MK3.9S upgrade kit
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.
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)
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
This product is supplied as a kit - you must assemble it yourself!
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
- PCCF printed parts
- Injection molded parts (PG cover and xLCD cover)
- WI-FI module
- NFC module
- High-Performance 360° Cooling Fan and Fan shroud
- High-flow Prusa CHT nozzle - 0.4 mm
Parts kept from your MK3S/MK3S+
- Frame and extrusions (new MK4S has just a different look)
- PSU* (same wattage/voltage as MK4S)
- 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
| MK3.5S upgrade | MK3.9S upgrade | MK4S upgrade | |
| High-Performance 360° Cooling | No | Yes | Yes |
| High-Flow Nozzle | No | Yes | Yes |
Build volume | 250 x 210 x 210 mm | 9.84 x 8.3 x 8.3 in | 250 x 210 x 220 mm | 9.84 x 8.3 x 8.6 in | 250 x 210 x 220 mm | 9.84 x 8.3 x 8.6 in |
| Mainboard | Custom 32-bit xBuddy electronics with STM32 | Custom 32-bit xBuddy electronics with STM32 | Custom 32-bit xBuddy electronics with STM32 |
| Stepper Drivers | Trinamic 2130 | Trinamic 2130 | Trinamic 2130 |
| Stepper motors | Regular 1.8° X,Y stepper motors | Regular 1.8° X,Y stepper motors | Precise 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 path | Aluminum heatsink, all-metal hotend | Aluminum heatsink, all-metal hotend | Aluminum heatsink, all-metal hotend |
| Drive system | Direct drive | Nextruder Planetary Gear System, 10:1 gearbox ratio | Nextruder Planetary Gear System, 10:1 gearbox ratio |
| First layer calibration | Manual adjust Z | Fully automatic (thanks to the Load Cell sensor) | Fully automatic (thanks to the Load Cell sensor) |
| Quick-Swap nozzle system | No | Yes | Yes |
| LCD screen | 3.5″ graphic 65k color screen | 3.5″ graphic 65k color screen | 3.5″ 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 monitoring | Filament 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 |
| NFC connection | Yes | Yes | Yes |
| Prusa Link | Integrated | Integrated | Integrated |
| Print medium | USB drive / LAN / internet via Prusa Connect | USB drive / LAN / internet via Prusa Connect | USB drive / LAN / internet via Prusa Connect |
| Firmware update interface | USB drive | USB drive | USB drive |
Kit price | 249 USD / 279 EUR (VAT incl.) | 499 USD / 549 EUR (VAT incl.) | 579 USD / 639 EUR (VAT incl.) |
| Buy MK3.5S upgrade | Buy MK3.9S upgrade | Buy MK4S upgrade |
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.
This product is supplied as a kit - you must assemble it yourself!