Draw it, print it, fly it!
3D printing and model aircraft are a match made in heaven. I started using a 3D printer this summer to create parts for a multirotor aircraft, and a new world of possibilities just opened up to me. Some people have printed entire frames in this fashion and maybe you would like to be able to do the same … Or maybe you just want to replace that cracked servo mount. But where do you begin? Here is how you can maximize your chances of success, while reducing any possible frustrations.
From the computer, to the printer and then to the quadcopter, making a part like this takes only a few hours or less. I wasn’t happy with first version, so this is my second try. 3D printing allows you to quickly create several prototypes at low cost. Consider using PLA filament for those experiments that end up in the garbage, since PLA is biodegradable.
3D GLASSES NOT REQUIRED
3D printing is the task of creating a solid object by depositing several layers — usually of melted plastic — on top of each other, by way of a specialized machine that works like a miniature mason. Unlike a human, the machine can achieve amazing levels of precision, down to a tenth of millimeter or less, while moving at amazing speeds.
It’s called printing because the process looks very much like traditional paper printing. You give a 3D image to the machine, which then puts layer on top of layer, over and over again, until you get a shape identical to the virtual 3D model.
People have built 3D printers for metal, concrete and even chocolate. But your 3D printer will most likely use a thermoplastic. The most common and easiest to use are ABS and PLA.
3D printers used to be expensive tools accessible only to companies or the very wealthy. But open source projects and commercial printers have made the technology accessible to all. For as little as $300, you can start toying with a rudimentary 3D printer. A decent machine will cost between $500 and $1,000, with the high-end “household” printers priced at around $3,000. You can build your own, assemble one from a kit, or buy one ready to use out of the box.
When I needed a landing gear and battery holder for my quadcopter, I couldn’t find anything I liked. So I created a set of 3D printed plates and joints that would assemble perfectly with a few leftover carbon-fiber tubes and wood dowels. 3D printing has become my solution to every multirotor challenge!
BEFRIEND SOMEBODY WHO ALREADY OWNS A 3D PRINTER
If you happen to know someone who owns a 3D printer, ask them to show you the basics. That’s probably the easiest way to learn. It also means that you’ll have somebody who can help you with your own printer at some point if you hit a bump. By the way, it’s common courtesy to compensate your friend for using up his entire filament. If you can’t find anyone, look into collective workshops like a Fablab, a hackerspace or a makerspace. Assuredly, they have a 3D printer you can use and they usually offer training. Try it and find out if it’s something that you like.
A piece of advice: do not rent a 3D printer by the hour! Printing a successful part takes a lot of time — especially at first.
In my case, I started at a local workshop called, “La Fabrique.” The printer belonged to Étienne Léveillé, a research professional at Sherbrooke University, and he showed me the basics. His advice is to first learn CAD (computer-aided design) and to have your first prints done by somebody else. Like that friend that I just mentioned. “Once you get the hang of designing,” says Léveillé, “and it becomes too expensive or troublesome to outsource fabrication, then it’s worth looking into buying your own printer.”
HOBBYIST REVOLUTION
When building or repairing a multirotor, you can’t always buy the parts that you need. Hobbyists will often fashion their own out of aluminum, wood, foam or carbon fiber. In any case, that job requires various specialized tools and considerable skill. The process is subtractive: you remove stuff until the stuff that you have left is in the shape of the part that you need.
- 3D printing is radically different.
- It’s an additive process, which creates very little waste.
- You only need one primary tool.
- It’s easy to learn.
- It’s safe and relatively quiet.
- And you can do other things while the machine does all the real work.
Plastic also happens to be very light, which makes it an ideal material for an aircraft. And if you crash and break it, just print a new one.
3D MODELING IS EASY – SERIOUSLY!
Websites like Thingiverse.com have vast libraries of parts and objects that you can download and print but most of the time, the part that you are imagining in your head doesn’t yet exist. The Internet has many good, free, 3D modeling programs to chose from, so you can start playing around with them right away!
I divide 3D modeling software into two categories: artistic and engineering. Creative software like Blender (open source) or Maya will allow you to make complex, aesthetic shapes. Unfortunately, they struggle at engineering parts with very specific dimensions that carry over faithfully to the real world. That’s why I usually design with parametric software like FreeCAD. AutoCAD is even better, but expensive. There’s also SketchUp, a free and easy-to-use alternative, but more limited in its capabilities. Tutorials are also abundant online.
I estimate that, as a total newbie, it took me around 10 hours of self-learning to make my very first 3D model of a practical object, and an extra 10 hours to really feel comfortable with the software. My advice is to start with a simple project. You may be tempted to design a full frame from the start. Don’t! Begin with simple things like a box for a circuit board or an arm for a servo, and gradually work your way up.
You can print overhanging parts, up to a certain point. Small cylinders usually work, as do slopes of less than 45 degrees (depending on the diameter of the extruder). Notice, however, that I gave this part a flat, square foundation to compensate for the very steep slope of the cylinder. I also had to run a drill through the holes to clean them up. When designing a part, be mindful of your 3D printer’s limitations.
BUYING YOUR OWN 3D PRINTER
Once you’re sure you want to take the leap, the first decision that you need to make is whether to buy a ready-to-use 3D printer or a kit that you assemble yourself. Adrian Bowyer, inventor of the RepRap Project, says that if you’ve built and flown a model aircraft, you probably have the necessary skills and should consider assembling your own 3D printer. “The very lower cost ones tend to be available as kits,” he says.
RepRap is the name of the most prominent open source 3D printer project. It has spawned several successful and widely used machines, such as the Prusa i3 and the Prusa Mendel. A RepRap printer is not specific to the company that you buy it from. For example, you can buy a kit for a Prusa i3 from various stores, with small variations from one store to another. The website 3ders.org is a good online reference for comparing kits and prices.
As Bowyer puts it, “I would recommend anybody who’s going to buy to go onto the [RepRap] forums (reprap.org) and get some independent advice or look at people’s experiences.”
Outside the RepRap universe, companies such as MakerBot, Printrbot and New Matter, to name only a few, offer easy-to-use consumer-type 3D printers.
Before buying, Léveillé suggests that you download and install the free software that is required for that printer. Play around with it to see if you like it. “The feeling you will get from that user interface can tell you a lot about the amount of effort that the manufacturer put into creating a product that is easy-to-use.”
The smaller 3D printers will have a 100 x 100mm printing bed. The bigger and moderately more expensive ones will be 200 x 200mm or more. I recommend going with something close to 200 x 200mm. The smaller ones are good for learning, but you’ll soon wish you had more space to work with. You should also make sure that your printer has a heated bed.
Buy your 3D printer from a reliable store. Some sellers on eBay, AliExpress or DealeXtreme may leave out important parts such as the heated bed or even the extruder, and you might not notice at first.
MAKE IT REAL
Most 3D printers require a connection to a computer and the installation of a specific piece of software to operate it. From this user interface, your computer will ingest the 3D model in the form of a stereolithography file (usually a .STL) and transform it into a program called a G-code. The G-code is uploaded to the printer, which then goes to work. Printing a part can take anywhere from a few minutes to several hours, depending on the size of the object.
Bowyer recommends that you stay away from aircraft parts at first. “Start by making more chunky, more solid objects, just to get the hang of the technology. The thing to do then is to progress to the sorts of things that [you] actually want to make […] like wing spars.”
COMMON PROBLEMS THAT MAY RUIN YOUR PRINT
Gravity. Remember that your 3D printer works somewhat like a brick layer, stacking thin films of plastic on top of each other. It can create overhanging parts, but only up to a certain point. Some parts may require the printing of a support structure which you remove at the end.
Weak foundation. You need the very first layer of the print to stick firmly to the heated bed. Otherwise, the extruder may end up dragging the plastic around instead of laying it down. I’ve also had parts detach from the bed mid-print because of poor adhesion. Depending on the type of bed, people may use a heat-resistant film, Kapton tape, a liquid adhesive or a combination of those solutions.
Moisture. ABS and PLA filament will absorb humidity over time, which creates tiny bubbles in the plastic and changes the size of the filament. Those can ruin your print. Store your filament in a sealed container with a desiccant.
Heat. When printing very small layers, remember that the previous layer needs to solidify before the machine puts a new one on top of it. Otherwise, you’ll get something out of a Dali painting. Some settings can help fix that.
LOTS OF VIRTUAL KNOBS
Your biggest hurdle may be getting your 3D printer properly configured so that it will produce a quality print every single time. In this case, price may be a factor. Léveillé points out that if you paid less than $400 for your machine, you may have to spend many hours tuning before it will produce good-looking parts. Nonetheless, he believes “anybody can get good results if they spend enough time fine-tuning their printer.”
Bowyer puts it this way: “The machine itself has a lot of virtual knobs to twiddle and change things like temperature, speed, depth of layers. The key thing is online advice.” If you’re using one of the more common machines, chances are that it will do a decent print out of the box. If not, you can usually copy somebody’s configuration from a forum, and that will get you started on the right path.
Everybody agrees that patience is key. That’s no different than flying an aircraft for the first time. And Bowyer highlights the payoff: “Once you get your printer working, it will carry on working for you for years, producing lots and lots of stuff.”
SHOP TALK
- Filament: raw plastic in wire form, usually ABS or PLA. Filament comes in various colors and is usually sold on spools of 1 kg or more. It may be 1.75 or 3.0mm in diameter. Make sure you buy the right kind for your printer.
- Extruder: the mechanical part that holds, melts and pushes the filament.
- Nozzle: hot end of the extruder, from which the melted plastic is squirted (or extruded). They come in various sizes. Smaller (0.3mm) is more accurate and gives a smoother finish. Bigger (0.5mm) is faster and more reliable.
- Heated bed: the working surface on which the 3D printer prints. It must be heated to ensure proper adhesion and to prevent warping.
- Stepper motor: driving force of the printer. A type of brushless motor that divides a full rotation into a number of equal steps. The motors usually drive long endless screw rods that, in turn, move the heated bed and/or the extruder.
- Slicing: the act of having a computer software “slice” a virtual 3D object into several horizontal layers. The same software then draws the path that the extruder will have to follow in order to print those layers.
- G-code: the program generated after slicing. It contains every single action that the 3D printer has to accomplish in order to create an object.
- Cleanup: the manual task of removing any excess plastic from a finished 3D printed part.
By William Levasseur
