Prusa Mendel

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Prusa Mendel

Release status: working

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 ;-)



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 Pm-coupler.jpg
3 endstop-holder RP Pm-endstop-holder.png
1 x-carriage RP Pm-x-cariage.jpg
1 x-end-idler RP Pm-x-idler.jpg
1 x-end-motor RP Pm-x-motor.jpg
1 y-motor-bracket RP Pm-y-motor-bracket.jpg
2 z-motor-mount RP Pm-z-motor.jpg
4 belt-clamp RP 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.
6 M8×30 mudguard / fender washer Fastener
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
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 or A2 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 X axis
5 NEMA 17 bipolar stepper motor Stepper Be sure to get ones with at least 20mm of shaft length. Shorter shafts require modifications to the X pulley assembly and Z motor couplers. One of the five motors, for use with the extruder, should be capable of creating a holding torque of at least 40Ncm, at the very least.
50 small cable binder / ziptie Misc
1 Wade's Geared Extruder for 1.75mm filament RepRap Universal Mini Extruder; or any other compatible extruder for either
1 Electronics + endstops This can be RAMPS, Sanguinololu, Gen6, Gen7, Gen3, or any other Mendel compatible electronics. Endstops are either optical switches or microswitches (Recommended), and you need three, one for each of the X, Y, Z axes.
Quantity Description Type Comments
3 30mm×10mm Optoflags Thin Sheet if using opto endstops
2 8mm ID spring Spring to eliminate backlash in the z axis
1 object with precisely 290mm length for frame alignment
1 object with precisely 234mm length for frame alignment

Note: You can combine the latter two by having a piece of thick sheet with dimensions 290mm×234mm. Make sure to mark which side is which.

Threaded Rod Cut Order (when cutting from 1m lengths):

 Required: 6x1m Long 8mm Threaded Rods (or 5x1m pieces + 1x50cm piece)
 Rod 1: 370mm, 370mm, 210mm, ~50mm (The last piece will end up somewhat shorter than 50mm. )
 Rod 2: 370mm, 370mm, 210mm, ~50mm ( Use it for your idler. Alternatively, an M8x30 or     )
 Rod 3: 370mm, 294mm, 294mm, ~42mm ( longer bolt can be used.                              )
 Rod 4: 370mm, 294mm, 294mm, ~42mm (Also, a piece of M8x20 threaded rod can be used        )
 Rod 5: 440mm, 440mm, ~120mm       ( for the wade's/greg's extruder idler.                 )
 Rod 6: 440mm

Smooth Rod Cut Order (when cutting from 1m lengths):

 Required: 3x1m Long 8mm Smooth Stainless Steel Rod 
 Rod 1: 420mm, 420mm 
 Rod 2: 406mm, 406mm
 Rod 3: 350mm, 350mm

The Prusa Mendel uses the 4 drivers in the standard Mendel electronics package to drive 5 motors by using two steppers wired in parallel to one driver [1].

Where To Purchase

See the Mendel Buyers Guide for information on where to purchase all of the parts needed.

See the Prusa Buyers Guide for information on where to purchase all of the parts needed.

Printing the Parts

A printed set of Prusa Mendel parts

Printing a Prusa on a Mendel

There are now four plates, sized sized to fit within a 200 x 200 x 140mm build platform.

mendle-plate-1.stl ~12h04m

mendle-plate-2.stl ~7h50m

mendle-plate-3.stl ~8h16m

mendle-plate-4.stl ~3h54m

(The Printing Time Estimates provided are based on 30mm/sec print speeds, and 25% infill. Your times will likely differ.)

(Help me out here: Are Bushings/bearings another print?)

Printing a Prusa on something else

Last but not least, if you have a machine won't print the above plates, or if you're in need of spare parts, all the .stl files necessary to print a Prusa Mendel are available on the PrusaMendel Github where you can download them and print them individually.

Buy the printed parts




Prusa Improvements/Hacks

See Also