Prusa i3 MK3

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Prusa i3 MK3 Documentation
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Prusa i3 MK3

Release status: working

Prusa i3 MK3 is a design by Josef Prusa.
CAD Models
External Link

The Prusa i3 (iteration 3) MK3 is the newest and most current 3D Printer design by RepRap Core Developer Prusajr. The i3 MK3 incorporates lessons learned from the previous Prusa designs. See also Prusa Mendel (iteration 2).

Infobox info icon.svg.png Derivates
The Prusa i3 is a very popular design, which led to many people creating derivates. We list these derivates in Category: Prusa i3 Derivate. Also check the Prusa i3 Variants page, as well as the Prusa i3 Development page


Main improvements

The following is a list of the main improvements from MK2S.

  • Filament sensor
  • Power Panic
  • RPM sensing fans and Noctua fan
  • Ambient thermistor and P.I.N.D.A 2 with thermistor
  • EINSY Rambo motherboard
  • Trinamic 2130 drivers with layer shift detection, faster and silent printing
  • New robust Y axis made out of aluminium profiles
  • Bondtech hobbed gears
  • Magnetic MK52 Heatbed
  • Powder coated PEI spring steel print sheet
  • Ready for OctoPrint


Offical kit available (Sep 2017)

In May 2016, the MK3 has been announced by Prusa with the phrases of "IT'S BLOODY SMART!".

B7/R3 extruder parts released (Jul 2018)

In July 2018, Prusa3d released a new updated extruder with better airflow for both fans. The new parts are available on Prusa's website and on the github page.

Multi material upgrade 2.0 (August 2018)

In August 2018, Prusa started shipping the MMU2.0. The upgrade consists of five spoolholders with bowden tubing and a filament switching mechanism on the top of the printer frame. The upgrade makes the printer capable of using up to five materials in the same print with just a single direct drive extruder and one hotend. The switching mechanism has it's own custom control board based on Atmega 32u4.

Textile wrap upgrade + more B7/R3 parts (Nov 2018)

Since November 2018, the MK3's have been shipping with a textile sleeve wrap for the cables instead of the previous spiral wrap. The textile wrap is supposed to make the wires last longer. New B7/R3 parts have been released:

a new Einsy RAMBo case with better and easier to use cable mounts and an add on slot for Octoprint

an updated x axis that is easier to assemble

reinforced y axis parts (the previous version sometimes cracked during assembly)

reinforced Z motor holders

MK3S and MMU2S released(Feb 2019)

In February 2019, Prusa3d released a new version of the MK3 called MK3S. The upgrade swaps out the previously used unreliable laser filament sensor for an IR one (thus requiring a complete extruder redesign) and improves the Y axis tensioning system. The new printed parts are designated C1/R4. As with MK2S, all new orders ship with this upgrade already in place. Prusa offers the upgrade for $24.2. The MMU2S upgrade is free for all MMU2 owners and consists of a redesigned extruder that prevents jamming and a filament buffer that prevents tangling. It also includes the MK3S upgrade. New orders of the Multi material upgrade from now on ship pre-upgraded to MMU2S.

Printed Parts

The STL files are available on Prusa Research. The SCAD and some STEP files are available on Github



Unlike previous Prusa machines, the MK3 runs on 24 volts. The fans run on 5V supplied by the mainboard.


The printer uses EinsyRambo as the main controller.

Filament sensor

This optical filament encoder is sensing the movement of the filament. So the printer can detect not only filament outage, but also a jammed nozzle. In addition, you can use filament auto loading function with this sensor.

MK3 uses a laser filament sensor aimed directly at the filament, which proved unreliable because different filament reflected the laser in different ways.

In the MK3S extruder, the filament moves aside a bearing ball which presses a small lever, triggering an infrared laser sensor. In this design, the sensor functions the same way a normally closed micro switch would, so the sensor cannot sense if the filament is moving or not.

Z endstop/bed leveling sensor (PINDA 2)

The printer uses an 8mm NPN inductive proximity sensor for bed leveling and as a z axis endstop. The heated bed has nine chunks of metal embedded in it in a grid pattern for automatic bed warp compensation. Normally, inductive probes have different triggering distances with different temperatures. The probe has an integrated thermistor to help the board compensate for that.



The extruder uses Bontech drive gears and an E3d V6 hotend with the standard e3d thermistor (Semitec 104GT), a 24V 40W heater and a 0.4mm brass nozzle. The extruder is a direct drive one, the Bondtech gear is mounted directly to the motor shaft.

Heated Bed

The printer uses a custom MK52 heatbed. The bed is made out of very thick PCB with 27 embedded magnets. The magnets hold a removable sheet of spring steel that is either powder coated with PEI or has a replacable PEI sheet glued to it. The steel sheets can be removed immidiatelly after a print stops and a new sheet can be inserted, resulting in faster printing in large quantities. After the printed objects cool down, they can be easily removed just by flexing the sheet.