User:Virtlink/Prusa Mendel (iteration 2)/Bill of Materials

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Prusa Mendel Documentation

This is the Bill Of Materials (BOM) for the Prusa Mendel i2.

It is consistent with the build instructions.

This includes:

  • Greg's Hinged Accessible Extruder Carriage
  • Bearing variants: ABS/PLA, LM8UU or LM8EUU
  • Cold glass/mirror bed
  • T2.5 timing belt
  • Aluminium T2.5 pulleys
  • ABS/PLA Z-axis couplings
  • ABS/PLA bearing guides

This does not include:

  • An electronics mount

For variations, please adjust the quantities you use accordingly. See below.

Printed parts

The files you need for the printed parts can be found in the PrusaMendel GitHub repository. Run generate-metric.bat (or one of the batch files for the linear bearings) and it'll generate all the STLs needed. You will need OpenSCAD installed and it will need to be in your path.

The following is a list of what needs to be printed:

  Quantity STL file Additional notes
I2-bar-clamp.png 8 bar-clamp.stl  
I2-bearing-guide.png 3 bearing-guide.stl 2 for Y-axis idlers, 1 for X-axis idler.
I2-belt-clamp.png 4 belt-clamp.stl  
I2-belt-clamp-nut-holder.png 4 belt-clamp-nut-holder.stl  
I2-coupling.png 2 coupling.stl Two parts are in one STL, print twice.
I2-endstop-holder.png 3 endstop-holder.stl  
I2-frame-vertex.png 2 frame-vertex.stl  
I2-Frame-vertex-foot.png 4 frame-vertex-foot.stl  
I2-rod-clamp.png 2 rod-clamp.stl  
I2-x-carriage.png 1 x-carriage.stl Pictured part fits LM8UU bearings.
I2-x-end-idler.png 1 x-end-idler.stl Pictured part fits LM8UU bearings.
I2-x-end-motor.png 1 x-end-motor.stl Pictured part fits LM8UU bearings.
I2-ybrac-t.png 1 ybrac-t.stl  
I2-y-bushing.png 3 y-bushing.stl Pictured part fits LM8UU bearings.
I2-z-motor-mount.png 2 z-motor-mount.stl  

Parts for Wade's extruder are also included with the iteration 2 STL's:

  Quantity STL file Additional notes
I2-wade.png 1 wade.stl  
I2-wade-big.png 1 wade-big.stl  
I2-wade-small.png 1 wade-small.stl  

Other non-printed parts

The following parts can not be reproduced on a RepRap and have to be found elsewhere.

  Part Name Basic Extruder Additional notes
Varilla-roscada-r1.jpg M8 threaded rod, 210 mm 2 0 Z-axis lead screws.
Can use 300 mm too.
Varilla-roscada-r1.jpg M8 threaded rod, 294 mm 4 0 Front/rear frame.
Can use 300 mm too.
Varilla-roscada-r1.jpg M8 threaded rod, 370 mm 6 0 Triangle side frames.
Varilla-roscada-r1.jpg M8 threaded rod, 440 mm 3 0 Top/bottom frame.
Can use 450 mm too.
Varilla-roscada-r1.jpg 8 mm smooth rod, 350 mm 2 0 Z-axis.
DSC04769.JPG 8 mm smooth rod, 405 mm 2 0 Y-axis.
DSC04769.JPG 8 mm smooth rod, 420 mm 2 0 X-axis.
Correas-T2 5.png GT2 timing belt, 840 mm 1 0 Y-axis. You can use T2.5 if you want. GT2 is slightly better but less available and often pricier.
Be sure to match pulleys.
Correas-T2 5.png GT2 timing belt, 900 mm 1 0 X-axis. You can use T2.5 if you want. GT2 is slightly better but less available and often pricier.
Be sure to match pulleys.
Polea T2 5.png Pulleys for GT2 belt, ~16 teeth 2 0 Can be 12 teeth, but 16-20 is advised for less backlash.
Bore diameter should be 5 mm.
Tubo goma 5mm int.png Vinyl tubing, OD: 6.35 mm, ID: 4.32 mm, L: 150 mm 2 0 Used to attach motors to the Z axis threaded rods.
Can be found at most hardware stores, typically used in toilets to connect refill tube to outlet.
Base madera 22x22cm.png MDF 6mm thick (dimensions unknown) 1 0 Used as the bottom print bed.
  Glass surface or mirror 1 0 Used as the top print bed.
Small, cheap Ikea mirrors work well.
2011-04-11-rodamiento.jpg Bearing, round 608 3 3 "6082RS" for sealed, "608ZZ" for shielded.
Don't cut costs here.
DSC05575.JPG Bearing, linear LM8UU/LME800 11 0 Or 8 x 25mm brass bushings. Check the plastic parts: in some cases an extra linear bearing is required.
If using linear bearings, don't cut costs here. Cheap ones can damage the smooth rods.
Tornillo Hyena.jpg Hobbed bolt M8 0 1 For bringing the filament down the nozzle.

Basic metal parts

Part Name Frame Y-Axis X-Axis Z-Axis X-Carriage Print bed Electronics Extruder Total Additional notes
M3 10 mm Bolt - 3 8 8 4 - - 3 26  
M3 25 mm Bolt - 4 - 8 4 - 3 - 19  
M3 40 mm Bolt - - - - - 4 - 3 7  
M3 Grub Screw - 1 - - 1 - - - 2  
M3 Nut - 4 8 8 5 5a 3 6 39  
M3 Washer - 8 - 20 8 16 6 - 58  
M4 20 mm Bolt - - - - 2 - - - 2  
M4 Nut - - - - 2 - - - 2  
M4 Washer - - - - 2 - - - 2  
M8 Fender Washer 30mm 4 - 2 - - - - - 6 Used in assembly instructions, but not necessary if bearing-guide.stl is used instead.
M8 Nut 60 - 2 4 - - - 2 68 Just buy a box of 100, spares are handy. Enough for Wade's extruder too.
M8 Washer 65 - 3 - - - - 4 72 Just buy a box of 100, spares are handy. Enough for Wade's extruder too.
  • a) Or nyloc nuts.


Part Name Frame Y-Axis X-Axis Z-Axis X-Carriage Print bed Electronics Extruder Total Additional notes
NEMA 17 Stepper motor 4 1 More information on stepper motors and their recommended torque, see the Stepper motor page.
Mechanical End Stop 3  
Stepper motor drivers
Stepper motor driver heatsinks


Stepper Motors

The Prusa iteration 2 uses 5 NEMA17 stepper motors, including the extruder. 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 iteration 2. 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.



Heated Bed

Heated Bed

Tools and supplies

To build your Prusa, you'll require the following tools and supplies:

Name Additional notes
Drill bit 8 mm  
Drill bit 4 mm  
Drill bit 3 mm  
Drill Handdrill or powerdrill.
Open-end wrench 13 mm You'll need two. A 0.5 inch open-end wrench might work too.
Soldering iron  
Screwdriver Philips head  
Calliper, 300 mm digital A 150 mm calliper works too.
Ruler 450 mm Steel or aluminium.
Wire stripper  
Wire cutters  
Zipties About a dozen.
Oil Any loose viscosity oil should work just fine for the smooth rods and Z screw. For example, gun oil.
Allen key 1.25 mm For the grub screws.
Allen key 3.00 mm For the M4 bolts.

The following tools and supplies are recommended:

Name Additional notes
Wire wrap  
Sigarette lighter  
Kapton tape, 10 mm  
Pocket knife  
Pair of crimps  
Organizer For all the little parts. Preferably with removable compartments.



For a list of possible extruders, see Extruders.

= Printing bed

A heated bed usually yield higher quality finished builds with materials such as ABS and PLA, as it prevents warping. It also removes the need for printing on rafts.

Timing belt

The GT2 timing belts and pulleys seem to become the new norm.


Included in the GitHub Prusa i2 repository are STL files for ABS/PLA T5 pulleys. Both the T5 belt type and the use of ABS/PLA pulleys is no longer recommended. Whatever timing belt type you end up using, ensure your pulleys match.

Z-axis couplings

Some people prefer aluminium 5 mm to 8 mm Z-axis couplings, but others say they have a tendency to stretch.

Bearing guides

It is easier to use fender washers on each side of the 608 bearings instead of printing and glueing the ABS/PLA bearing guides. In this case, use an M8 30 mm fender washer, then a normal M8 washer, then the 608 bearing, then a normal M8 washer and then the M8 30 mm fender washer again.

Electronics mount

While you could easily make yourself a mount from MDF and secure it to the RepRap using zip ties, some prefer to print this ABS/PLA Electronics Mounting Plate for RAMPS and Printrboard.


There are all kinds of alternatives to the default Arduino Mega and RAMPS 1.4 electronics. You can find them on the Alternative Electronics page.