Prusa i3

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Prusa i3 Documentation
Main page | Prusa i3 Buyer's Guide | Prusa i3 Build Manual | Prusa i3 User Manual | Prusa i3 improvements

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Prusa i3

Release status: working

Description Prusa i3 is a design by Josef Prusa.
License GPL
Author Prusajr
Based-on Prusa i3
Categories Prusa i3, Prusa i3 Development, Prusa Mendel Development, Prusa Mendel, Mendel Variations, Cartesian-XZ-head
CAD Models none
External Link Github

The Prusa i3 (iteration 3) is the newest and most current 3D Printer design by RepRap Core Developer Prusajr. The i3 incorporates lessons learned from the previous two Prusa designs, as well as other popular modern RepRap 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




  Single Sheet Frame Box Frame
Plastic Parts (exc. Extruder) 26 29
Non Printed Parts (approx.) 337 293
Cost (USD) $300-1000 $300-$800
Controller Electronics Almost all RepRap Almost all RepRap
Printing Size (mm) 200 x 200 x 200 200 x 200 x 270
Motors 5 x NEMA 17 Stepper 5 x NEMA 17 Stepper
Frame Material 6mm Aluminium, Wood 12mm Wood
Frame Manufacture Laser Cutter, CNC, Water Jet Basic Woodwork Tools
Pro Easy assembly Rigid XZ to Y Connection
Con Specialised Tools Looks less professional?

Main improvements

The following is a list of the main improvements made upon the Prusa Mendel Iteration 2

  • Enhanced frame rigidity (prevents x-axis backlash)
  • Easy assembly
  • Parametric files for multiple sizes/bearings or bushings


The development of the Prusa Mendel is hosted on github:


Prusa i2 (November 2011)

On 11-11-11, the Prusa i2 is announced on the reprap blog.

Prusa i3 (May 2012)

The first commit to the Prusa3 GitHub repository.

"Final refactoring complete" (September 3 2012)

Josef Prusa: "Final refactoring complete."

There were many commits the following months, evidencing the continuous development process.

The rate of commits dropped rapidly after August 2013.

However, that is not the end of the Prusa i3 development. See the Prusa i3 Development page here.

Original development moved to Vanilla (January 2014)

Prusa moved the original development to "vanilla repository" on Github in January of 2014.

Offical kit available (May 2015)

In May 2015, the official kit became available from Prusa.


Main article: Prusa i3 Variants

The release of the Prusa i3 under the GPL license and numerous other factors (its low cost, minimal BOM, simple assembly and calibration procedures, more than adequate documentation, etc) have encouraged the further development of a growing number of Prusa i3 "variants" worldwide, with different parts, different materials and different assembly processes, but which altogether adhere to the general looks, component assembly, dimensions and functionality of the original Prusa i3.

See the page Prusa_i3_Variants for an attempt to list the Prusa i3 Open Source variants along with their differences / improvements and "genetic lineage". Also check out the Category: Prusa i3 Derivate page which lists using the wiki tagging feature.

Printed Parts

OpenSCAD files for the printed parts are available on the Github repository.

To compile the parts and render STL files, copy configuration.scad.dist[1] to configuration.scad, and customize by editing values.

Precompiled STL files to make the printer can be found at the Clone Wars page for the i3, and here zipped up:[1]

Frame type

Most major Prusa i3 Frame Styles fall into two categories: the Single Sheet Frame, and the Box Style Frame.

The Single Sheet Frame is designed to be manufactured through the use of a Laser cutter, WaterJet, or CNC Mill / Router Table. There are two current development tracks within the Single Sheet Frame, an Aluminium frame style, and a gusseted Wood frame style. Both are designed to support 6mm or thicker framing material. Both the EiNSTeiN variant and the i3 Rework designs use single sheet aluminum frames, as do most kits. The Box Style Frame, on the other hand, is designed to be easily manufactured at home with basic woodworking tools. The Y-axis for both frame styles is similar to that of the older Prusa Mendel Iteration 2.

Single Sheet Frame

This is a frame created from flat metal sheet, typically Aluminium, but can also be made from other material with a thickness usually between 3mm (0.125 inch) and 6mm (0.25 inch).

Prusa i3 with a single metal sheet style frame.
Prusa i3 with a single metal sheet style frame.


  • Looks professional (subjective).


  • Requires specialized tools (e.g. abrasive water jet cutter, laser cutter, CNC router) or contracting out.
  • Less rigid connection between XZ-frame and Y-frame part.

Box Style Frame

This frame is created from 8 small sheets of wood.

Prusa i3 with a box style frame
Prusa i3 with a box style frame


  • Can be created with standard DIY tools.
  • More rigid connection between XZ–frame and Y–frame part part.


  • Looks less professional (subjective)


Stepper Motors

The Prusa i3 uses, including the extruder, 5 NEMA17 stepper motors. Two of these motors, the Z axis motors, are connected to the same stepper driver of the electronics. If using Wade's Extruder, its stepper motor needs a minimum holding torque of 40Ncm (0.4Nm). More information can be found on the Stepper Motor page.

Controller Electronics

About any RepRap controller works for the Prusa i3. Required features: 4 stepper drivers, 1 thermistor input and 1 heater output for the extruder and optionally another thermistor/heater pair for the heated bed. Choosing the best one for your printer is mostly a matter of taste. For comparisons, see List of electronics, Comparison of Electronics and Alternative Electronics.



On November 12th, 2012 Josef Prusa (@josefprusa) tweeted a picture of his metal frame i3 with a custom dual extruder mounted.

Prusa i3 with an unnamed dual extruder mounted.
Prusa i3 with an unnamed dual extruder mounted.

Previous posts on Prusa's twitter feed reveal that Sound (Slic3r's Developer) inspired Prusa to attach a dual extruder.

In may 2015 was published the &makers single direct drive extruder named &struder, was designed to use on Wood multitool and now is adapted to use on prusa i3.

Heated Bed

The Prusa i3 includes a Heated Bed which allows for the use of materials such as ABS and nylon which can experience significant warping if printing on a cold platform.

  • MK3 heating bed, aluminum plate thickness of 3 mm, uniform heating, fast, back has good heat preservation, high temperature can be heated to 120 degrees


Filament Holder

For Sheet Style,

For Box Style,



  1. Please note that the zipped files are not compatible with holes for the Z axis brackets in the Prusa3ALU-*.dxf drawings, at least the ones in the old/ folder in github. Also, the models for Y-axis brackets are for M8 rods. Compiling your own and investigating the Prusa github packages is highly recommended!