Prusa Mendel Documentation

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Revision as of 14:00, 3 April 2012 by Katie (talk | contribs)

A new reprap printer will built along the lines of the Prusa Mendel. You can find details of the Prusa design at the Prusa Mendel page on the reprap wiki, or you can view the sources for the Prusa at github

Prusa Mendel Frame.jpg


Having another 3d printer in the space will allow us to always have a working machine and to use one machine to help fix another if there are problems. It will also enable several people to print things out at the same time. The goal is to document this build so others can make their own printer following our documentation.


Frame is built! Next up: axes. And we have electronics, mobo flashed with sprinter fw, use pronterface to interface with it. Have to wire in steppers to finish.

Materials for the build

BOM for Prusa Mendel

Quantity Description Type Comments
83 M8 nut Fastener READY
93 M8 washer Fastener READY
6 M8×30 mudguard / fender washers Fastener READY
2 M4×20 bolt Fastener (John) / or use M5x20
2 M4 nut Fastener (John) / or use M5
2 M4 washer Fastener (John) / or use M5
22 M3×10 bolt Fastener READY
8 M3×20 bolt Fastener (John) / cut down 25mm or use as is
8 M3×25 bolt Fastener READY
4 M3×40 bolt Fastener (John) / cut down 50mm or use 35mm
70 M3 washer Fastener READY
40 M3 nut Fastener READY
2 M3 grub screw / set screw Fastener READY
3 608 roller skate / inline skate / skateboard bearing Bearings READY
4 ballpoint pen springs Spring READY
6 M8×370mm Threaded rod 3 per side - READY (Thanks Mark!)
4 M8×294mm Threaded rod front / rear - READY 4 x 340 (Needs cutting)
3 M8×440mm Threaded rod top / bottom - READY
2 M8×210mm Threaded rod Z-leadscrew - READY 2 x 300 (Needs cutting)
1 M8×50mm Threaded rod or bolt for X idler - READY
2 8mm×420mm Smooth rod X-bar - READY
2 8mm×406mm Smooth rod Y-bar - READY
2 8mm×350mm Smooth rod Z-bar - READY
1 225mm×225mm print top plate Thick Sheet (space)
1 140mm×225mm print bottom plate Thick Sheet space
1 840mm×5mm T5 pitch timing belt Belt READY
1 1380mm×5mm T5 pitch timing belt Belt READY
5 NEMA 17 bipolar stepper motor Stepper READY
50 small cable binder / ziptie Misc READY
1 Wade's Geared Extruder READY
1 Electronics + endstops READY (though I, Xaq, am still curious about TinyG...)
1 Printed parts READY


1x gen3 mobo 2x gen3 EC 5x steppers 4x stepper controllers (we'll have to pull these from the cupcake and have the cupcake use the mbi ones) 1x p4ac 4 axis stepper controller carrier board (we'll have to pull this from the cupcake too) 1x wade's extruder (assembled and working) 1x 36mm brass barrel 1x 0.5mm mbi nozzle 1x 0.5mm makergear bighead nozzle Insulator materials (have to make and document on lathe) nuts/bolts/washers - I have tons plywood/mdf for build platform

Heated Build Platform

If we want it, can get away with some other hacks if we want, or leave it out altogether.


Alden has a Tiny G board... this is attractive

How to flash firmware

download arduino18 from (sanguino extensions appear to only work with 18) download the sanguino extensions from unzip the arduino package unzip the sanguino package and copy contents to the hardware folder in the arduino folder you unzipped. get the latest sprinter fw from fire up arduino and load the sprinter sketch edit the configuration.h file to list a motherboard type of 21 plug in the gen3+ motherboard to your laptop with a usb-ttl ftdi cable. set the board to sanguino in the tools in arduino. set the serial to the port in use by the ftdi cable save/compile/upload the sketch

How to connect and control the printer

Download printrun from make sure you have python installed, or follow instructions at the url above fire up set the serial port to the one used by ftdi cable click connect to printer button you should see confirmation of printer connection in the monitor box on the right load stl and slice it with sfact in the gui, or load up a gcode file you're already processed. SD printing should work too.

To do

PSU: Done The electronics need an ATX supply (200W minimum probably, 350-700W+ would be needed if we run a heated bed) to power the mobo, and we'll need to hack out a 12V and a 5V line to connect up to the larger perfboard electronics that run the extruder/heatbed (these should be on a 12v2 rail on newer psu). I've got some connectors to do this the next time I'm in the space, or we can just cut the connectors off of the atx wires. Steppers: The P4AC 4 axis board will need to be pulled from the cupcake, and the XYZ connected to the mobo. (we'll need another 10pin idc cable. the current rainbow cable on the gen3plus setup is the X stepper cable from the cupcake stepper controller and will have to go back once we swap out the p4ac to the mendel. I have some 10pin idc cables at home I will bring in to replace the one in the gen3plus) I have the 4th pololu in the larger perfboard, but I can easily drop in a 10pin idc header so that we can have all the pololus on the one board, which I'll do the next time I'm in the space. Mosfets: tip120 replacements are attached to the board in case the current ones die or if someone has time to do the replacement. The Nchannel Power Mosfets on the larger perfboard were ones I got from radioshack, so I'm not sure if they'll be able to run the heated bed, but they should be fine for the extruder. I have proper 50V 10A mosfets I can swap in place the next time I'm in the space or if the ones in there right now fail. Motor Connections: The motor wires need to be connected to the pololus. Any 4 conductor cable should work fine. I have solid core 4 conductor wire I used on my bot at home, but the single conductor is a bit fragile and I'd recommend a nice stranded set instead. I have matching molex connectors and crimps so the connection to the p4ac board is via a plugged connector instead of soldered in or done with some other hacked connector. Endstops: The ends stops need to be hooked up. The p4ac board has breakouts for the endstops, so just need to wire up microswitches on to that board. only need two wires to each switch, signal to the COMmon contact and GND to the NO (normally open) contact, the firmware uses internal pullups for the endstop pins.