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We are starting a project to build and maintain a 3D printer. At the moment we are discussing which model we will focus on. Here are some options:


RepRap Prusa Mendel (Taken from Wikimedia user Julianh72)
Model: Mendel
Version: Prusa

The RepRap seems to be a promising, affordable and flexible, adaptable candidate. Especially the RepRap Prusa Mendel seems to be well suited for a Hackerspace. It costs between 450€ and 800€ as a ready set and probably less than 200€ if we get the parts locally.

The parts needed for the Prusa Mendel are almost entirely standard parts that can be found in almost any hardware store. These are mostly M8 thread rods, M8 screws and nuts, standard skateboard bearings, the common NEMA 17 stepper motor.

Here's a list of the parts needed (taken from the RepRap Wiki)

Printed Parts

Quantity Description Type Comments Printed
2 coupling RP stl[[1]] none
3 endstop-holder RP stl[[2]] none
1 x-carriage RP stl[[3]] none
1 x-end-idler RP stl[[4]] none
1 x-end-motor RP stl[[5]] none
1 y-motor-bracket RP none
2 z-motor-mount RP stl[[6]] none
4 belt-clamp RP stl[[7]] none
8 bar-clamp RP none
2 rod-clamp RP none
2 pulley RP none
4 frame-vertex with foot RP none
2 frame-vertex RP none
12 pla-bushing RP-PLA check your build file, the file makes either 4 or 12 none

Non-printed parts:

Quantity Description Type Comments Available
83 M8 nut Fastener Buy a 100-pack to be on the safe side.
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
2 M3x8 screw Fastener Anything 6mm or longer should do. Even M3×10 bolts will do the job.
22 M3×10 bolt Fastener
8 M3×20 bolt Fastener The M3x25 bolts are too long for the recent Prusa z-motor-holder, rod-clamp, and couplings.
8 M3×25 bolt Fastener
4 M3×40 bolt Fastener
70 M3 washer Fastener
40 M3 nut Fastener 8 optionally locknut / stop nut / nyloc
3 608 (roller/inline skateboard) Bearings Standard wheel bearings.
4 ballpoint pen springs Spring To fit over M3 bolts. About 25mm long and compress to about 10mm.
6 M8×370mm Threaded rod 3 per side - 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 - 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 X axis
5 NEMA 17 bipolar stepper motor Stepper At least 20mm of shaft length. One should have a torque of > 40Ncm. 13€ each
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, Generation 6 Electronics, Generation 7 Electronics, Generation 3 Electronics, or any other Mendel compatible electronics. End-stops are either optical switches or micro-switches (Recommended), and you need three, one for each of the X, Y, Z axes.

Extruder (Print-head)

Wade's extruder design (Taken from the RepRap wiki)

Printed Parts

Quantity Description Comments Printed
1 extruder block none
1 extruder idler block none
1 11 tooth drive gear none
1 39 tooth M8 hub driven gear none

Non-Printed Parts

Quantity Description Type Comments
2 608 bearings, skateboard bearings Bearings
1 M8×50 bolt Fastener to be hobbed, M8×60 has a longer smooth part, allows a second lock-nut, and may be easier to find
1 M8 nut Fastener Nyloc works better, but a pair of nuts will also work
4-5 M8 washers Fastener to space the large gear clear of the motor retaining bolt heads
1 608 bearing, skateboard bearing Bearings
1 (M)8×20 Threaded rod
4 M4×60 or M4×45 hex head bolts Fastener Hex head will work best (they won't turn), and longer than 45 mm will be easier to assemble if you can find them.
4 M4 nuts Fastener typically wing nuts
8 M4 washers Fastener
4 ~4mm ID springs Spring Sized to fit over an M4 bolt, unsprung length of 10-12mm, each spring providing 25-35N load. For a given filament drive force, you'll need about twice the spring force - i.e., if you want 100N of filament drive, your springs need to push with about 50N each.
16 M4 washers Fastener optional; 4 washers on each M4X45 idler bolt between the main block and the idler block will limit the idler travel and make reloading filament easier.
NOTE: Some users have their extruders working without springs, but springs are recommended. A good source for these springs is in the cloth-cabinet on spring loaded skirt-hangers or trouser-hangers. Just cut the right length off the springs.
Hot End Mount
2 M3×35 bolts Fastener
4 M3 washers Fastener
2 M3 nuts Fastener
1 2.5mm drill See section Hot End
Stepper Motor Mount
3 M3×10 bolts Fastener Low profile bolt heads might work better here
3 M3 washers Fastener
1 M3 grub screw Fastener To secure the pulley, ideally 8mm long, but anything 6mm+ should be fine
1 M3 nut Fastener To secure the pulley
Stepper Motor
1 NEMA 17 bipolar stepper motors Stepper 5 kg*cm (=49 N*cm, 69 ozf*in) works well; Kysan 42BYGH4803 is what I used. Should be capable of creating a holding torque of at least 40Ncm (4.07 kgf*cm, 56.6 ozf*in), at the very least.
Extruder Mount
2 M4×20 bolts Fastener
2 M4 nuts Fastener
2 M4 washers Fastener


The Generation 7 Board is easily self-made and extensible. It uses no SMD devices, needs only one layer of copper so it can be etched or possibly milled.