Building the cheapest possible Prusa i3 MK2

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What is the cheapest possible, real 3D printer you can buy without making one compromise after the other? That’s the question we’re asking by building a Prusa i3 MK2-style 3D printer that comes with most of the important features of the original one from Josef Prusa and requires a bit more work for sourcing and building the machine, but most importantly, we’re going to build it only with the most affordable set of parts.

This page will serve as a hub for part lists and build guides as the project moves along! All build videos and the accompanying project videos have been organized into a neat playlist!

Electronics and extruder

Each of these parts were picked for a reason – be it because they are better than the alternatives, or, as expected, simply cost less than anything else. You can find the full explanation and the accompanying video on its own page, but here are the lists of parts we’ve covered so far!

Electronics

PartFunctionQty neededCheapest offerSeen at
Mechanical endstop boardsEndstops2$0.34Aliexpress
Reprap heated bed aluminumHeated bed1$6.42Aliexpress
100K BTC with cableHeated bed temperature sensor1$0.52Aliexpress
RAMPS 1.4Mainboard1$3.69Aliexpress
Arduino Mega 2560 cloneMainboard1$7.13Aliexpress
12V 20A power supplyPower supply1$14.79Aliexpress
A4988 driverStepper motor drivers4$0,73Aliexpress
Reprap 14pcs wire setWiring1$3.05Aliexpress

Optional parts

PartFunctionQty neededCheapest offerSeen at
LCD Controller, character-based versionLCD and SD card reader1$7,49Aliexpress
LCD Controller, graphical versionLCD and SD card reader1$9.49Aliexpress
IEC socketPower input1$1.17Aliexpress
Rocker switchPower switch1$0.99Aliexpress

Extruder Assembly

PartFunctionQty neededCheapest offerSeen at
5V M8 inductive sensor Z probe1$5.09Aliexpress
1.2mm Extruder springs (pack of 10)Extruder springs1$0.96Aliexpress
Hobbed gearFilament drive gear1$0.80Aliexpress
E3D v6 Jhead with fan and thermistorHotend1$5.00Aliexpress
2x4mm bowden tubeHotend-extruder liner1$0.80Aliexpress
50mm radial fanPart cooling fan1$1.16Aliexpress
625 bearingExtruder idler bearing1$1.50 (10-pack)

Update: Thx to the hint from FB User David Kiddell we now know about this better Mk2 Extruder Design from Geoff Sim on Thingiverse.

Frame and motion

The frame is a fairly standard i3 type – you could go with  a kit or make it yourself. The cutting template is attached at the bottom of the page, a .dxf file for CNC routing or lasercutting can be found on Prusa’s github!

Frame and fasteners

The fasteners have been adapted to work with a thicker frame and to make use of the alternative components used in this build. If you don’t want to cut the frame yourself , you can also buy one!

PartFunction / noteQty neededCheapest offerSeen at
18mm or 3/4" plywood/OSB/...Frame material370x370mm~$1.00
Optional: Thinner material (10mm or 3/8") for bed carriageBed frame material225x225mm~$1.00
M3x10 cap-head screw (DIN912)16
M3x18 cap-head screw (DIN912)18
M3x20 cap-head screw (DIN912)7
M3x30 cap-head screw (DIN912)21
M3x40 cap-head screw (DIN912)3
M3 nut (DIN934)42
M3 nyloc nut (DIN985)Locknut, alternatively jam two regular nuts or use threadlock4
M3 square nut slim (DIN562)6
M3 washer (DIN125)22
M3 fender washer (DIN9021)30
M5 nut (DIN934)2
M5 threaded rod (DIN976)1m
M8 nut (DIN934)alternatively slim nuts for aesthetics22
M8 washer (DIN125)22
M8 threaded rod (DIN976)cut to 4pcs of 205mm1m
M10 nut (DIN934)alternatively slim nuts for aesthetics14
M10 fender washer (DIN9021)4
M10 washer (DIN125)Can be replaced by fender washers with new printed part8
3D printed partsSubstitute the parts linked below for compatibility with the components listed here1 setGithub
M10 threaded rod (DIN976)cut to 2pcs of 360mm1m
2.5x100mm zip tieslike, 100Amazon

Linear motion

What’s listed here is the way I’m building this printer, an even cheaper option would be to go with IGUS bushings and generic 8mm smooth rods!

PartFunctionQty neededCheapest offerSeen at
8mm smooth rods, 320m, 330 or 350mm, 370mmX, Y Z linear guide2 each size$26.98Aliexpress
LM8UU bearingsX, Y, Z linear bearings10$5,70Aliexpress
GT2-2M 6mm belt (often just called "GT2") (set with pulleys)X, Y belt2m$0.52Aliexpress
GT2-2M 16T pulleys, 5mm bore (set with belt)X, Y belt pulleys2-
GT2-2M 16T idler pulley, 3mm boreX, Y belt idlers2$2.48Aliexpress
NEMA17 stepper motorX, Y, Z (x2), E stepper motors5$41.00Aliexpress
5x5mm flexible couplerZ-axis coupler2$1.60Aliexpress

Printed parts

Most of the printed parts are the exact ones from the MK2, however you don’t need all of them and a few have been modified to make them work with the cheaper components. Where possible, they should still be compatible with the original parts.

To get them printed, try 3DHubs (I’ve got a few printers listed, too :-), a local FabLab or Makerspace or convince a friend to print them for you!

Standard parts

These are from PrusaResearch’s Github page

PartQty needed
extruder-body.stl1
extruder-cover.stl1
extruder-idler.stlprint modified design
fan-nozzle.stl1
x-carriage.stl1
x-end-idler.stl1
x-end-motor.stlprint modified design
y-belt-holder.stl1
y-corners.stl2 for 350mm Y smooth rods, 4 for 330mm Y smooth rods
Y-distance.stl1
y-idler.stl1
y-motor.stlprint modified design
z-axis-bottom.stl1
z-axis-top.stl1

Modified parts

Also based on the original MK2 files, but modified for the parts suggested for this build. These parts are attached at the bottom of this page!

PartQty needed
Z-nut holdah x4.stl4
extruder-idler (simplified) x1.STL1
x-end-motor (new endstops) x1.stl1
y-corners (open) x2.STL2, for 350mm smooth rods 0, for 330mm smooth rods
y-motor (new endstops) x1.STL1

Optional parts

With the standard and modified parts, you should be able to build a 3D printer capable of printing its own upgrades. The following parts are non-essential addons, like an LCD mount or bed probe protector. While these can be a starting point, there are plenty of alternative parts and upgrades available on Thingiverse and Youmagine!

PartQty needed
LCD-cable-clip.stlA few
LCD-knob.stl1
LCD_SupportA.stl1
LCD_SupportB.stl1
LCD_cover.stl1
PINDA_protector.stl1

Stay tuned as we move on with the build of the super-cheap Prusa i3 MK2. This page will get updated as progress is made!

Download Attachments

  • zip MK2 Dolly printed parts set 2017-03-17
    Complete set of printed parts (including individual parts listed below)
    File size: 4 MB Downloads: 6865
  • pdf Prusa i3 frame
    Easily printable Prusa i3 (MK2) frame. No brace. 370mm wide and tall (check your print scale!)
    File size: 451 KB Downloads: 14038
  • dxf Alu frame dxf
    Originally made from 6mm aluminum, but also works for wooden frames. From: https://github.com/josefprusa/Prusa3-vanilla/blob/master/src/alu-frame.dxf , licensed GPL v3
    File size: 79 KB Downloads: 4462
  • stl extruder-idler (simplified)
    Updated extruder idler design with printed bearing rod and integrated bearing shoulders. Fully featured replacement and usable with the Original MK2 design!
    File size: 403 KB Downloads: 4768
  • stl y-motor (new endstops)
    Original X-motor end with a mounting point for the PCB endstop
    File size: 158 KB Downloads: 3349
  • stl y-corners (open)
    Modified design to allow use of longer (350mm) smooth rods for the Y-axis. Use these corners in the rear of the machine and let the rods overhang.
    File size: 64 KB Downloads: 2907
  • stl x-end-motor (new endstops)
    Original X-motor end with a mounting point for the PCB endstop
    File size: 890 KB Downloads: 3077
  • stl Z-nut holdah x4
    M5 nut holder compatible with the original Prusa i3 MK2 parts.
    File size: 360 KB Downloads: 2994
  • zip MarlinFirmware
    Firmware as used on the Dolly Build
    File size: 1 MB Downloads: 3017