3D printing for engineers

Reprap, what is (in) it?

A dictionary / summary


Reprap stands for self-replicating rapid prototyper


1940 Mathematician John von Neumann develops a theoretical machine that can reproduce itself.

1979 First Rapid Prototype technologies patented.

1995 The term '3d printing' was coined by two MIT graduate students.

2004 Adrian Bowyer writes his manifesto Wealth without Money.

2005 RepRap blog is opened

2008 First RepRap 3D printer named 'Darwin'

2009 2nd generation RepRap Mendel is finished.

2010 Reprap family tree is exploding, and still is.


The model we built in this workshop is the Prusa i3, named after it's (mechanical) designer Josef Prša from Prague. I3 stands for iterations 3 because it is the third RepRap he designed. Development can be followed on the github.

Other popular reprap designs are: the rostock, eventorbot, printrbot, bukobot, foldarap, hugo, just to name a few.


Most used materials are PLA and ABS. The print material is a plastic string with 1.75mm or 3mm diameter.

PLA is a biodegradable plastic made out of maize. It can be used up to 60ºC and melts around 185ºC which makes it easy printable. Printing doesn't smell and it is a relative hard material.

ABS is the same plastic as e.g. Lego bricks. It can be used well above 100ºC and melts between 215 and 250ºC. It smells while printing, but fumes are not considered harmful.

Both materials are available in a wide variety of colors and are sold online in Germany through: fabber-parts, reprapsource, print2beta, nodna, and others. Generally 1 kg costs less than 25 euro.

Experimentation is done with chocolate, porcelain, polycarbonate, color mixing, and much more. For this you'd need a universal paste extruder of something similar


Get your 3D model for printing

Download models from thingiverse or dedicated projectsites or githubs.

Open Source Modeling software

OpenSCAD is widely used in the reprap community. Objects are programmed and therefore readable and commentable.

Blender is a powerful artistic open source 3D software with a steep learning curve.

FreeCAD is a command based application for technical purposes.

And there is HeeksCAD, Wings3D, Art of Illusion These programs are all open source.

Freeware modeling software

Sketch-up user friendly software for architectural design.

123d app easy to use software for modeling and scanning by Autodesk

Meshmixer intuitive artistic sculpting software.


3dtin 3d modeling for children, completely for free.

tinkercad 3d modeling for 3d printing, login obliged free edition has limited possibilities.

Any propriety software will do the trick too. AutoCAD, Inventor, Maya, 3DStudio, SolidWorks, etc.

Every model should be exported as .stl or .obj file.

A model might have errors. This you could repair with meshlab, (the free version of) netfabb, or check with minimagics

Slicing software

This category of very important software is turning the 3d file to g-code (machine instructions)

Slic3r a fast and simple slicing software, which is actively being developed.

Skeinforge slow gcode generator with more settings. Rather outdated by now.

Cura a new user friendly slicer and printerdriver in one. Recommended.

Kisslicer stands for keep it simple slicer.

See the no.1 edition of reprapmagazine for a review.


This category of software sends the g-code to the printer through the usb cable.

ReplicatorG a user friendly printerdriver, a bit outdated.

Cura a new user friendly slicer and printerdriver in one. Recommended.

Pronterface the traditional reprap printerdriver.


The control electronics are always Arduino based. Generally the Arduino Mega 2560 is used. Arduino is open source programmable electronics. It's task is to convert the g-code instructions into action.

The Arduino board needs extra electronics to set and control the temperature and to drive the motors. Usually the RAMPS electronics is used for this.

The RAMPS electronics hold 5 drivers for the stepper motors. These stepperdrivers are usually Polulu A4988 drivers.

Other variations on electronics are Gen6 and Gen7, Sanguinolulu, Megatronics, Rumba, Rambo, etc.

The motors are stepper motors. These motors turn around in (normally) 200 steps per revolution. The usual size is Nema 17 with a torque between 4.2 and 5.2 Ncm

The temperature is measured with an NTC Thermistor. This is a resistor that gets a lower and lower electric resistance as the temperature gets higher.

The endstop detects the home (=zero) position of the X, Y, and Z axis. This can be done mechanically, optically and magnetically. The latter is the case in your printer.


Every extruder has a hotend (the nozzle where the molten material comes out) and a cold end, the part that pushes the material into the nozzle.

Cold end designs

Wade's extruder straightforward design with many variations.

Bowden extruder where the heavy motor can stay in place.

Universal paste extruder to extrude chocolate, peanut butter, porcelain and more.

Einstein this is in your printer


J-Head supposedly the best nozzle out there. You have a variation of it.

Prusa Nozzle full metal hotend and therefore capable of printing higher quality plastics.

Ceramic J-Head new exciting nozzle!

Budaschnozzle design by lulzbot.

Arcol hotend rather complex hotend design, similar to the budaschnozzle.

V3 Metall a full metall extruder from Köln

Before buying a new hotend check compatibility with the plastic part of you extruder. You might need to re-print it.


In random order Germany based, for materials, electronics, etc.

reprapsource Germany based, for materials, kits, extruder, parts, etc.

print2beta Germany based, for materials, kits, etc.

nodna Berlin based, for materials.

Reprapdiscount China/ebay based.

Ebay in general has a lot to offer as well. Netherlands based, for materials, motors, electronics, belts, etc.


Irc a chatroom for direct answers. Server: channel #reprap. the wikipedia of reprap. allways fresh news of 3d printing in general.

Fabbaloo same here...

Richrap in depth technical blog. Check his 'slicer is nicer'.

Nophead in depth technical blog, equal to Richrap.

Reprapmagazine it's the reprap magazine!