Prusa Mendel (iteration 1)

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Prusa Mendel Documentation
If you are building this machine using SAE (imperial) fasteners, see also SAE Prusa Mendel.


Prusa Mendel is the Ford Model T of 3D printers.

Like the Model T, the Prusa Mendel improves on a previous design by being more streamlined for manufacture. The Prusa Mendel is a simpler remix of the original Mendel. By default, it uses printed bushings instead of regular bearings, though options to substitute inexpensive lm8uu linear bearings or other types of bearings or bushings are available. The current version uses three 608 bearings in total, one for the X axis and two for the Y axis. The 624 bearings are gone altogether.

Prusa's main goal is to be the purest and simplest 3D printer you can build.

  • It's much simpler to build it.
  • It's much simpler to modify it.
  • It's much simpler to print it for your friends.
  • It's much simpler to repair it.

Because of its complexity, the Prusa Mendel can be a living thing. I update it all the time. It's a unique feature but it should be standard. We are living in feature, we don't care if it's a bit different every time; our printer will print it in same time ;-)


  • Printed Parts: 45 (extruder drive included?)
  • Non-Printed Parts: 388
  • Material Cost: ???
  • Cost: ??? (assembled)
  • Printing Size: 200mm x 200mm x 100mm (8.2" x 8.2" x 4.1")
  • Precision: ??? (position), ??? (printing)
  • Speed: ??? (position), ??? (printing)

Video Clip



The development of the Prusa Mendel is hosted on github:

You can follow the changes on Changelog.

You can sign up for github for free and fork the project to begin working on it.


Bill of Materials

Printed Parts

Quantity Description Type Comments Diagram
2 coupling RP stl[[1]] Pm-coupler.jpg
3 endstop-holder RP stl[[2]] Pm-endstop-holder.png
1 x-carriage RP stl[[3]] Pm-x-cariage.jpg
1 x-end-idler RP stl[[4]] Pm-x-idler.jpg
1 x-end-motor RP stl[[5]] Pm-x-motor.jpg
1 y-motor-bracket RP Pm-y-motor-bracket.jpg
2 z-motor-mount RP stl[[6]] Pm-z-motor.jpg
4 belt-clamp RP stl[[7]] Pm-belt-clamp.jpg
8 bar-clamp RP Pm-bar-clamp.jpg
2 rod-clamp RP Pm-rod-clamp.jpg
2 pulley RP Pm-pulley.jpg
4 frame-vertex with foot RP Pm-frame-vertex-foot.jpg
2 frame-vertex RP Pm-frame-vertex-footless.jpg
12 pla-bushing RP-PLA check your build file, the file makes either 4 or 12 Pm-bushings.jpg
NOTE: Many alternatives exist to the standard Prusa RP parts. Head over to RP alternatives to check out other options. If you are just getting started with reprap, it is recommended to use the standard BOM of RP parts to keep life simple.

Non-Printed Parts ("vitamins")

Note that additional parts are required for the extruder, although some extruder parts are included in the table below.

Quantity Description Type Comments
83 M8 nut Fastener Buy a 100-pack to be on the safe side. M8nut.jpg
93 M8 washer Fastener Buy a 100-pack to be on the safe side. (Grade 2 works fine.)
6 M8×30 mudguard / fender washer Fastener These are also known as penny washers, they have a much larger outer diameter than regular washers.
2 M4×20 bolt Fastener To mount the extruder
2 M4 nut Fastener To mount the extruder
2 M4 washer Fastener To mount the extruder
22 M3×10 bolt Fastener
16 M3×25 bolt Fastener Or eight M3×25 bolt plus eight M3x20 bolts. The M3x25 bolts are too long for the recent Prusa z-motor-holder and rod-clamp, and also for the Z motor couplings. See Section 8, steps 4 and 13 for details.
4 M3×40 bolt Fastener
70 M3 washer Fastener
40 M3 nut Fastener 8 optionally locknut / stop nut / nyloc
2 M3 grub screw / set screw Fastener M3x8 seems about ideal but anything 6mm or longer should do. If these are hard to get, additional M3×10 bolts will do the job instead.
3 608 roller skate / inline skate / skateboard bearing Bearings You don't need to ask for a "608 bearing" at a skate shop, just ask for wheel bearings.
4 ballpoint pen springs Spring To fit over M3 bolts. Ballpoint pens are a common, cheap source of suitable springs. They are about 25mm long and compress to about 10mm.
6 M8×370mm Threaded rod 3 per side

Note: The threaded rods can be cut from larger 6x1m pieces (see Threaded Rod Cut Order below).
4 M8×294mm Threaded rod front / rear
3 M8×440mm Threaded rod top / bottom
2 M8×210mm Threaded rod Z-leadscrew
1 M8×50mm Threaded rod or M8x30 or longer bolt for X idler. Take care: if the bolt is too long, it may not be threaded along a sufficient length
2 8mm×420mm Smooth rod X-bar

Note: 304 Stainless Steel, A2 Tool Steel, or O1 Tool Steel are recommended for smooth rods as it can help to prevent friction from rust and manufacturing (straightness) standards are higher. Rust issues can be prevented on the normal steel rods by maintaining a coat of oil. The smooth rods can also be cut from larger 3x1m pieces (see Smooth Rod Cut Order below).
2 8mm×406mm Smooth rod Y-bar
2 8mm×350mm Smooth rod Z-bar
1 225mm×225mm print top plate Thick Sheet
1 140mm×225mm print bottom plate Thick Sheet Note: The Prusa Iteration 2 design does not use a print bottom plate.
1 840mm×5mm T5 pitch timing belt Belt Y axis
1 900mm×5mm T5 pitch timing belt Belt
5 NEMA 17 bipolar stepper motor Motor
50 small cable binder / ziptie Consumables or other cable management
10 8mm Linear Bearings - LMU88 Bearings