By Murat Ali and Andrew Wright
31st May 2016
It probably hasn’t escaped you that 3D-printing is ever more popular, with news agencies reporting on the latest medical, home office and aerospace innovations that utilise this fantastic technology. What might not be immediately obvious is the similarity between what you can do in your front room and what Boeing, Airbus, the European Space Agency, NASA and multiple others are doing using similar principles.
Think of words such as precise, expensive, high-level, complex and advanced. Cutting-edge, although an overused cliché, applies in all except the actual process. Printing in 3D is actually a very simple concept; just layers of material one after the other, gradually building up anything from simple to ridiculously complicated shapes. The process can be used to manufacture parts such as a critical jet turbine blade, or a simple part for your model aeroplane at home, made by you.
The basics of 3D-printing
The technology to do all of this now exists and all we need, aside from a moderate pile of notes with which to purchase the kit, is to know how to use it. So where better to start than in school. Think back to technology lessons involving traditional methods of woodwork, and (hopefully we’re not too old to say) more recently computer-based electronics and programming, which along with materials science are the basic building blocks of this new technology. Mix into this the current generation of engineers with Computer Aided Design (CAD) and manufacture (CAM) skills, and you have the basis of efficient design to production processes when it comes to 3D-printing.
So what exactly is this supposedly magical technology, and how does it work? Undoubtedly most of you reading this either own or have used a printer at some stage. Your printer effectively reads data from a PC, laptop or device that you sent the data from and physically prints that data: up, down, left and right, and across the page onto paper using ink. This can be referred to as two-dimensional (2D) printing. Now imagine you replace the ink with a material such as plastic or metal and the printer is now able to print that material: up, down, left, right, and away from the page. This exciting prospect is the basis of three-dimensional (3D) printing. Now we open up a huge opportunity to produce parts that can usefully be used on a model plane, and even parts of a jet engine. It works by starting from the bottom and building up layers of material as it moves it’s way up, like building a house from bottom to top, one brick at a time. It therefore seems logical to call this, ‘additive manufacturing’, because the material is added one step at a time.
This technology makes it possible to manufacture parts that conventional processes may not be able to achieve. It can make producing prototypes easier, especially if your prototype can be produce to a small scale. You could 3D print this on your desk and examine your idea as a 3D object rather than a flat image on your computer screen. You even have control over the porosity of the component, which is a technical word for describing how much empty space there is inside the part. This means you could make the part lighter and with less material than the same part machined from a solid piece of material.
Some challenges to overcome
There are of course some temporary drawbacks. We say temporary because, as the technology improves, we would expect these drawbacks to diminish. Some of the key challenges at the moment are:
– the availability of materials,
– producing parts as quickly and accurately as some current manufacturing methods,
At the moment it would be feasible to 3D print a complete model plane; however, the larger the part is the bigger the 3D-printer needs to be to print it.
Bearing this in mind, it is understandable that the current use of this technology for production of small batches, or even on mass scale, is in the making of relatively small parts. Being small may help to meet the safety regulations. As far as aviation is concerned, we don’t think of a Jumbo Jet as being particularly small, so you’d be right in thinking that 3D-printing a complete jetliner would not happen any time soon. In fact, imagining a 747 gradually appearing out of a giant printer the size of a multi-storey car park may be beyond even the most exaggerated science fiction minds. However, a Jumbo Jet, section of the International Space Station, Air Force fighter jet, or a weather balloon is made up of small parts, so this is good news for the status of the 3D-printing technology today.
Why is this good news? Do we just want to use 3D-printing for the sake of it? Well not necessarily, there are actually some spectacularly good advantages to it which we will come to later.
3D-printing for the skies
There is a fundamental engineering principle referred to as: KISS – Keep It Simple, Stupid. While a coarse phrase, it simply makes the point that the more complicated something is, the more chance something may go wrong. A component made of four parts, made in four different locations by four different machines, inevitably introduces more unknowns as a system made up of one part. Assuming each part is equally reliable, a Jumbo Jet with four engines has twice as much chance of having an engine failure as a twin-engined aircraft. So if possible, it would be ideal to have two enormous engines (or even one) but that introduces more issues, such as bending stresses, however we can talk about this another day. Reliability is a massive issue and consideration in Aerospace, as you can imagine. We can cover that another day too when we look at how to minimise unknown issues that may occur during manufacture. A quality program called Six Sigma can be used to minimise the defects in manufacturing and decrease the risk of something being made outside of the specification.
The point is that 3D-printing opens up the opportunity to produce parts, and improve safety and reliability in a way which may not have been previously possible, therefore complex multi-part systems may be replaced with parts which are less likely to fail. So in Aerospace we have new possibilities of simplify a system using 3D-printing; by taking a part that previously had 4 different bits due to the limitations of the manufacturing process, we may be able to ‘print’ it as a single part. We can do it in reverse. Instead of starting with a big bit of material and reducing it down with drills and so on and so forth, we start from nothing and build it up, layer by layer. Every layer is being laid from the ground up, effectively emerging up out of nothing, therefore we can avoid issues getting in to any sharp corners or producing complex shapes using big tools. Instead of subtracting, we are adding. Additive manufacture.
For 3D-printed parts to be used safely on an aircraft, what conditions do they need to withstand? The answer to this question largely depends upon what section of the aircraft the part is for, how long it is required, and what is the risk and consequence of failure. For a model plane you can afford to take more risk as the ultimate price to pay will be a crash landing in a field and maybe a plane bumping someone on the head if you are really unfortunate.
Let’s start inside the aircraft. For items used within the cabin (such as a table tray) the parts need to withstand the loads placed upon them by the passengers, cabin crew and pilots. last thing anyone wants is for a lap full of cottage pie and orange juice. The parts also need to withstand vibrations whilst the aircraft is operating and the impact loads during landing.
Now for the outside of the aircraft. Have you ever noticed icicles on your window, even when the sun is shining in the skies? The temperature outside the aircraft can be all the way down to around -75°C, depending on the type of aircraft and weather conditions at cruise altitude. Considering that water freezes at 0°C helps you appreciate how cold it really gets up there outside the aircraft. The power of flight means that we can travel across the world in reasonable amounts of time, but the plane rushes through the air at incredible speeds to achieve this, hitting the air particles along it’s way. If parts outside the aircraft are not designed with cold temperatures and aerodynamics in mind or are not able to withstand the aerodynamic forces, they may fail.
Moving from freezing temperatures to scorching hot temperatures, the jet engine. There is some good news here, 3D-printed parts are already being certified by the Federal Aviation Authority (FAA) in the US for use on Boeing aircraft. 3D-printing has allowed for complex shapes to be achieved which were unable to be achieved using traditional machining techniques. The fact that material is being built up means that there is very little waste of material which is good news for the environment and for those who pay the company bills. This really sets a precedent for future development and we can only hope it will continue in this way. For the air traveller; lighter, simpler and more reliable parts will hopefully lead to safer, more reliable and cheaper air travel in the future.
Safety in aviation is the number one priority. There simply is no market without confidence in safety. We only need to look at what happened to the aviation industry after September the 11th, or to the airline Pan Am; an industry that was massively successful but ultimately subject to events that undermined consumer, passenger and confidence. More than anything, we as members of the public empathise with those involved in such tragic events because flying for business or pleasure is such a commonplace and necessary factor in almost all of our lives.
Of course 3D-printing is not only for commercial aviation, because of the vast variety of aerospace applications we could talk about now. It is a huge market, and as we said above, anything likely to affect vast numbers of the travelling public is going to be subject to some pretty heavy safety regulation. The manufacture of aircraft is already subject to some of the closest scrutiny of any engineering production in the world, and the introduction of new parts and innovative processes will understandably be looked upon with extra suspicion and caution. Pilots in particular are highly risk-averse: that means we are suspicious of change because it introduces risk. Engineers are no different, but we must balance the need for improvement and innovation with reliable and well tested methods to ensure we are progressing in a safe way.
Despite these challenges, the use of 3D-printing for producing parts for planes that take you to your wonderful holiday destination is still in its infancy, however, it is showing great promise. The idea that you can own and use a 3D-printer to produce parts yourself is also exciting. This could be one of the major innovations in the future of home computing.
You could use your 3D-printer to produce the parts that contribute to the next iteration of aircraft design, even if only for your model plane. This 3D-printer could inspire your son and daughter to make and fly the best-looking toy. Even if you decide not to do any 3D-printing yourself, it is likely that you will be enjoying your flying experiences surrounded by 3D-printed parts much sooner than you think.
You can read more and follow Murat Ali at http://www.muratali.ml/ where this article has also been posted.