Introduction
Ok, so I got myself a 3d printer from reprap pro (Mendel Tricolour, yep.. proudly develeoped in the UK so no „color“). The thing came as a complete kit.. „some assembly required“… and by „some“ we mean: you don’t have to solder SMD components otherwise EVERYTHING has to be bolted, screwed, soldered, crimped and glued.
I won’t go into detalis, if you are REALLY intrested in my build and my experiences and what I learned, go into the „animate.se“ forum and look for my tricolour build (swedish) or ask me.
After ca 20hours of pure build time i got it moving, and extruding.
How should it work?
My printer uses so called „Fused Deposition Modelling“ to make a model. Now how does that work?
Imagine you squeeze toothpaste out of the tube, in a circle, then you sqeeze another circle on top of it, and you repeat this, eventually you end up with a tube, made up of layers. The problem with toothpaste is that it doesn’t have enough stability and don’t get me started on flowing.. smells nice though…
Now instead of toothpaste my macine uses plastic (more about plastics further down). The plastic comes in long strands (filament on coils) of 1.75mm diameter and is put into the extruder, a stepper motor (a motor where the rotation can be finely controlled) feeds the strand into the hot-end where it is molten and squirted out of a fine nozzle (the kit comes with a .5 mm hole, i upgraded to a .3mm hole). Then it lays down a strand on the buildplate just like the toothpaste. The plastic is a little bit more stable and it cools quickly and becomes solid.
The whole extruder can move in x/y/z direction so you can reach any point whitin a 20x20x14cm envelope.
So layer by layer a model can be built… in theory
Slicing
I’m not going to cover how to make a model, that in itself is a HUGE art of its own (if you know how to do 3D CAD this is no problem)
Now, most models come in a .stl format, and are usualla solid 3D models (there are libraries online like Thinigiverse). In order to print them you need to translate the 3D CG instructions into instructions that can be understood by the machine, so called GCODE. GCODE tells the machine everything it needs to know to make an object. The temprature, the speed of the axis, of the extruder, the feedrate (speed of plastic squriting out) the temprature of the buildplate and whatever else is needed.
In order to make this translation so called „slicers“ are used. They add the settings for the machine to the 3D model and translate everything into GCODE.
The settings for the machine, and printout are the true craft of 3D printing. You decide how fast the printhead should move, how thick the plastic strand is (this may vary!), what temprature buildplate and hotend should have, should your fans be turned on, if so at what level, do you want to print directly on the plate or do you want some support structures (raft, skirt, brim, supports…)
If you get it wrong all sorts of stuff can happen, even if your hardware is fine.
Too high temprature an you get blobs of material and fine structures won’t cool and the whole print will become ugly or even fail
Too low temprature and you won’t get enough material, or it cloggs directly.
Too high temprature on the buildplate and you print melts (se above)
Too low temprature on the buildplate (or wrong surface) and your print can lift of the plate and wrap or fail.
Too fast and you get vibrations
Too slow and it will print for days
Turn on the fans to early and you risk lifting
Turn them on too late and you get problems with details
In summary there is a steep learning curve in this and every day i learn something new.
Actual printing
Interface
In order to control the printer there is a printer interface (I use pronterface) you connect the printer to your computer via USB and ge at control interface. You can set the tempratures, „Home“ the axis i.e. tell the printer where the printhead is, by sending it to the „endstops“ and manually drive the head to any x/y/z coordinate.
z-axis calibration
An important part of setting up is the z-axis calibration. Ideally the printhead is barely touching the buildplate when it’s at z=0, in reality it is about 1 paper-thicknes off the plate (z=0.1mm). This is set with a screw and is more of a skill than something that can be built into the hardware. The procedure is not easy and has to be repeated before every print, if you want good results.
Materials
The printer works with thermoplastics, i.e. plastics that can be formed and reformed with heat. The most common materials are Poly-lactic Acid (PLA) and Acrylonitrile butadiene styrene (ABS). PLA is made from organic materials (e.g. corn starch) and is even biologially degradeable. ABS is made from petroleum producs. Printing PLA requires 180-200 deg C and is rather unflexible, to prevent warping the buildplate should be heated to 50-60 degC or has to have a certain surface (roughed up acrylic or blue painters tape), it ha a tendency to flow if not cooled propperly. ABS is printed at about 220-230 degC, needs a heated bed (100 degC) to prevent warping and should have a very stable thermal environment (enclosure). Oh and PLA smells nicely, ABS more like acrylic glue (so I am told.. never used the stuff).
Running gcode and starting the print
Printing can be done from the computer, but can lead to problems if it something disrupts the print-program.
A better way is to download the gcode to an SD card and run it from the card in the machine, while the computer just starts the print.
Once the machine starts and the first layer sticks, you can relax, otherwise, stop the print, clean the plate, adjust the z-axis and try again…
Print done!
When the print is done you remove it from the plate, remove the supports (just break them of, or remove them with a scalpel), clean it, sand it paint it or whatever you wish to do.
About multicolor
Multicolor works by running 3 printheads with 3 different colors, these cannot be mixed, but rather layered next to each other. An addidional calibration tells the printer of the relative position of each head, each printhead has to be installed at the same height.
It works, but is complicated and the results are very dependent on the model. The printer basically prints 3 different models in the same space, and this means that all problems of a normal print are multiplied by 3. I rarely use it.
Final thoughts
The good
3D printing is really lots of fun, from an idea, to a 3D model to final pirint, if all goes well, you end up with something that you just had in your mind, sure most crafts work the same way but I don’t have the patience and dexterety to really become good to that level.
The bad
It takes time to print, even small simple items take about an hour, 15-20 minutes preparation, 30-40 minutes printing. Complex models can take days to model, slice and print.
The ugly
When it goes bad… best case your print is ugly and you have to use a lot of scalpel-work and sanding, worst case, your print destroys the machine: blobs of plastic block everything, the z-axis goes straight into the bed and the x/y axis looses calibration and tries to print in thin air or at impossible coordinates where your stepper motors scream and eventually fail.
Was it worth it?
I think so, i learned a lot, and expanded my toolbox for problem solving.
Should you get one?
If you want to tinker get a kit for 500 euros, if you want/need to make models get a propper printer (e.g. makerbot or ultimaker) for about 1500 euros, and if you need REALLY good quality get something from the pros (e.g. stratsys) 15000 euros and up…
If you don’t want to tinker, program or spend a lot of money wait a little, prices will go down preformance up and ease of use up.