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

Part Function Qty needed Cheapest offer Seen at
Mechanical endstop boards Endstops 2 $0.34 Aliexpress
Reprap heated bed aluminum Heated bed 1 $6.42 Aliexpress
100K BTC with cable Heated bed temperature sensor 1 $0.52 Aliexpress
RAMPS 1.4 Mainboard 1 $3.69 Aliexpress
Arduino Mega 2560 clone Mainboard 1 $7.13 Aliexpress
12V 20A power supply Power supply 1 $14.79 Aliexpress
A4988 driver Stepper motor drivers 4 $0,73 Aliexpress
Reprap 14pcs wire set Wiring 1 $3.05 Aliexpress

Optional parts

Part Function Qty needed Cheapest offer Seen at
LCD Controller, character-based version LCD and SD card reader 1 $7,49 Aliexpress
LCD Controller, graphical version LCD and SD card reader 1 $9.49 Aliexpress
IEC socket Power input 1 $1.17 Aliexpress
Rocker switch Power switch 1 $0.99 Aliexpress

Extruder Assembly

Part Function Qty needed Cheapest offer Seen at
5V M8 inductive sensor Z probe 1 $5.09 Aliexpress
1.2mm Extruder springs (pack of 10) Extruder springs 1 $0.96 Aliexpress
Hobbed gear Filament drive gear 1 $0.80 Aliexpress
E3D v6 Jhead with fan and thermistor Hotend 1 $5.00 Aliexpress
2x4mm bowden tube Hotend-extruder liner 1 $0.80 Aliexpress
50mm radial fan Part cooling fan 1 $1.16 Aliexpress
625 bearing Extruder idler bearing 1 $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!

Part Function / note Qty needed Cheapest offer Seen at
18mm or 3/4" plywood/OSB/... Frame material 370x370mm ~$1.00
Optional: Thinner material (10mm or 3/8") for bed carriage Bed frame material 225x225mm ~$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 threadlock 4
M3 square nut slim (DIN562) 6
M3 washer (DIN125) 22
M3 fender washer (DIN9021) 30
M5 nut (DIN934) 2
M5 threaded rod (DIN976) cut to 2pcs of 350mm 1m
M8 nut (DIN934) alternatively slim nuts for aesthetics 22
M8 washer (DIN125) 22
M8 threaded rod (DIN976) cut to 4pcs of 205mm 1m
M10 nut (DIN934) alternatively slim nuts for aesthetics 14
M10 fender washer (DIN9021) 4
M10 washer (DIN125) Can be replaced by fender washers with new printed part 8
3D printed parts Substitute the parts linked below for compatibility with the components listed here 1 set Github
M10 threaded rod (DIN976) cut to 2pcs of 360mm 1m
2.5x100mm zip ties like, 100 Amazon

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!

Part Function Qty needed Cheapest offer Seen at
8mm smooth rods, 320m, 330 or 350mm, 370mm X, Y Z linear guide 2 each size $26.98 Aliexpress
LM8UU bearings X, Y, Z linear bearings 10 $5,70 Aliexpress
GT2-2M 6mm belt (often just called "GT2") (set with pulleys) X, Y belt 2m $0.52 Aliexpress
GT2-2M 16T pulleys, 5mm bore (set with belt) X, Y belt pulleys 2 -
GT2-2M 16T idler pulley, 3mm bore X, Y belt idlers 2 $2.48 Aliexpress
NEMA17 stepper motor X, Y, Z (x2), E stepper motors 5 $41.00 Aliexpress
5x5mm flexible coupler Z-axis coupler 2 $1.60 Aliexpress

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

Part Qty needed
extruder-body.stl 1
extruder-cover.stl 1
extruder-idler.stl print modified design
fan-nozzle.stl 1
x-carriage.stl 1
x-end-idler.stl 1
x-end-motor.stl print modified design
y-belt-holder.stl 1
y-corners.stl 2 for 350mm Y smooth rods, 4 for 330mm Y smooth rods
Y-distance.stl 1
y-idler.stl 1
y-motor.stl print modified design
z-axis-bottom.stl 1
z-axis-top.stl 1

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!

Part Qty needed
Z-nut holdah x4.stl 4
extruder-idler (simplified) x1.STL 1
x-end-motor (new endstops) x1.stl 1
y-corners (open) x2.STL 2, for 350mm smooth rods 0, for 330mm smooth rods
y-motor (new endstops) x1.STL 1

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!

Part Qty needed
LCD-cable-clip.stl A few
LCD-knob.stl 1
LCD_SupportA.stl 1
LCD_SupportB.stl 1
LCD_cover.stl 1
PINDA_protector.stl 1

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: 10334
  • 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: 20348
  • 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: 6838
  • 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: 6208
  • stl y-motor (new endstops)
    Original X-motor end with a mounting point for the PCB endstop
    File size: 158 KB Downloads: 4445
  • 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: 3839
  • stl x-end-motor (new endstops)
    Original X-motor end with a mounting point for the PCB endstop
    File size: 890 KB Downloads: 4139
  • stl Z-nut holdah x4
    M5 nut holder compatible with the original Prusa i3 MK2 parts.
    File size: 360 KB Downloads: 4049
  • zip MarlinFirmware
    Firmware as used on the Dolly Build
    File size: 1 MB Downloads: 4952