Prusa i3

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Prusa i3 Documentation
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Prusa i3

Release status: working

Prusa i3 is a redesign by Prusajr.
CAD Models
External Link


The Prusa i3 (iteration 3) is the newest and 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 RepRaps designs.


  • Printed Parts: ???
  • Non-Printed Parts: ???
  • Material Cost: ???
  • Cost: ???
  • Printing Size: ??mm x ??mm x ??mm
  • Precision: ??mm (position/printing)
  • Speed: ??cm/s (position/printing)

Main improvements

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

  • enhanced frame rigidity (prevents x backlash)
  • easy assembly
  • parametric files for multiple sizes/bearings or bushings


The development of the Prusa Mendel is hosted on github:


Printed Parts

The STL files to make the printer can be found at Clone_wars:_Prusa_iteración_3.

To compile yourselve use the files from Github [[2]] (box style files) [[3]] (Single sheet style) Copy configuration.scad.dist to configuration.scad and fill custom settings section there

RP every .scad in this directory (except complete-printer) once. Aim for 0.3mm layers and 2.2 extrusion width (width over thickness), for 0.66mm stroke width. Printer is tested at this setting.

Using doc/complete-printer.scad as a visual clue and doc/manual.txt as a guide, build the printer.

Frame type

There are two major Prusa i3 Frame Styles, 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. The Box Style Frame 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 a single sheet of metal, typically Aluminum, but can also be made from various Materials with a thickness greater than 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 specialised tools (e.g. Water flow jet cutter)

- Less rigid connection between XZ-frame and Y-frame part

Box Style Frame

This frame is created 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


- 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.

//Need name, info, and link to this extruder and how to build it. Can anyone help? -idolcrasher

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

Heated Bed

Heated Bed

Filament Holder

Here you can find some ways how to place the filament spool to the printer

TODO list some ways