Ctrl + P = aircraft: How additive manufacturing will reshape aviation
Things have changed a lot since Dr Robert Sharman, global head of additive manufacturing (AM) at GKN, first became involved in 3D printing. In fact, when he started, neither term existed. His PhD was about powder deposition. The same thing but not as catchy.
Now 3D printing is everywhere. But the work Sharman’s team does is a long way away from the plastic 3D printers you can buy on Amazon for a few hundred dollars. This is one reason why GKN uses the term AM to distinguish between 3D printing for non-engineered parts and AM for critically-engineered parts.
GKN Additive has supplied AM parts to Dassault’s Falcon 5X, the Ariane 5 Space Rocket and several engine programmes. Seven aircraft types have GKN AM parts on board and GKN’s AM technology is used to make parts for many cars.
But this is just the start. While AM is certain to change the way aircraft parts are made and distributed, the impact will be bigger. It will allow manufacturers to fundamentally redesign engines and aircraft.
“AM is best when it allows you to do something that you cannot do any other way – either physically, economically or both,” says Sharman. “You can do amazing things, and they may even be cheaper in the long run. Parts consolidation is one example. The actual component may be very high value but, if you are putting several 3D parts into a single part and cutting out the assembly and weight, there is a multiplication of benefits.”
He says that, rather than looking at individual parts, the real breakthroughs will come when whole systems are built using AM.
“Everything that you see around you looks like it does because of how we make it,” says Sharman. “Holes are round because we drill them. But holes do not have to be round. If you look at your blood vessels, they continually vary in shape and size to reduce pressure loss as your blood flows through your body. AM allows you to generate systems like that that would have been uneconomical or impossible with traditional techniques.”
Engineers have been looking at natural systems or bionic design for many years but Sharman says that AM finally makes it possible to truly incorporate it. “if you look at how we make things and how nature makes things, they do look quite different,” says Sharman. “Nature tends to be right. After all, it has had a bit more practice.”
But while it opens up new opportunities, creating AM aircraft parts is not easy.
AM or 3D printing is about building things layer by layer. “Fundamentally, you take the design of a part and then you slice it down, digitally, into multiple layers and then you effectively use an energy beam to melt that layer and fuse it to the layer below,” says Sharman. “You grow the part.”
This fusion – effectively a series of micro-welds – also changes the properties of the material. “We are actually generating the material’s properties as a part of the manufacturing process,” says Sharman.
Whilst plastic 3-D printers rely on polymers, creating a new metal part is much more complicated – and not just because aircraft parts are used for more critical roles. AM manufacturers can make hundreds of small adjustments that change the property of the part.
“There are lots of variables you can change. These include the energy beam power, the size of each layer, the type of material, the powder and others. If you are using powder, the size, the shape, the morphology makes a difference. As does the speed at which you scan, the part at which you scan the energy beam, and so on,” says Sharman. “It is a multi-parametric system. Each of those different parameters need controlling and understanding because of the change to geometric shape – every shape is different.”
One reason that AM is still evolving is that manufacturers need vast amounts of computing power. The calculations and data they store and process now were not economically possible just a few years ago.
“Once you understand all those parameters, it is about understanding how all those different elements of the process come together effectively to give you what we call an energy density – the window which allows fusing,” says Sharman. “That is also linked to geometry. If I am making something thick, the cooling as it melts is different than if I make something thin, and if I make an intersection. For a complex part, that heat flow is different for every geometry and every part. “It is hugely complex, and this is a blessing and a curse. The curse is that it is complex to get it right; but the blessing is that you can really do some quite amazing things that would be unthinkable with conventional manufacturing.”
While lots of companies are experimenting with 3D printing for interiors, the extra complexity involved with metal aircraft parts limits the number of companies targeting this market. Another barrier to start-ups is the need to work with regulators. At the moment aerospace regulators and OEMs are still learning about AM manufacturing. Manufacturers need to prove new techniques as well as their quality systems. This gives existing suppliers like GKN an advantage.
Aviation is also benefitting from developments in other industries, like automotive and rail. Sharman says that developments in other markets mean that AM will change aviation faster than many people think. Adoption of AM will also depend on new aircraft and engine projects. The widespread adoption of composite parts has taken almost 40 years.
Sharman is confident that every major upgrade or new clean-sheet design project will use AM. One reason for this is that OEMs are keen to understand the process better so want to use AM on all new projects.
Pretty much every aircraft part can now be made using AM. But Sharman does not expect this to happen.
“Probably the biggest error people make is that they come up with something that’s already being made and say, ‘Can you make it?’ The answer is almost certainly ‘yes’. But then ‘why would I?’ The biggest advantage is, and certainly this is what we are seeing in the market today, being able to either use materials or generate materials that you couldn’t process otherwise.”
Sharman says there are ceramics and metals that manufacturers have studied for years but have not been able to use in production – either for cost or processing reasons. Using AM can also cut down wastage, allowing manufacturers to use more expensive metals.
“AM allows you to use materials that you could not otherwise use. And there is functionality, as well. I think a lot of people focus on the lightweight design but, because you can generate hugely complex structures, you can generate shapes for functional parts that will otherwise be physically or uneconomical to make, with huge impact.”
An example of this could be the acoustic liner of an engine. At the moment, these are typically built with a regular honeycomb design. AM allows manufacturers to make each cell different to absorb a certain frequency of wavelength of noise. This could make liners better at absorbing sound whilst weighing less than traditional ones.
AM will change the whole parts supply chain. As costs come down, it will be possible for every airport to have printers or AM machines. An aircraft’s monitoring systems could alert maintenance shops that a new part is needed and a new one could be created before the aircraft lands. Rather than having millions of dollars tied up in parts, manufacturers and maintenance companies could just own printing machines and stock powder. Several air forces around the world are working on this at remote bases.
“We are not there yet with structural parts,” says Sharman, “but several airlines are already looking at printing interiors for polymer parts such as interiors at airports. This is probably not as far away as you think – interiors and small fittings could be one year away.”
AM will also make it possible to repair parts. A worn blade can be rebuilt rather than scrapped. “We are already in production with certain freeform deposition AM techniques,” says Sharman. “You can repair and build up high-value components much more cost-effectively in some cases – and repair components that previously would be unrepairable.”
Some engine OEMs are hoping that, eventually, they will be able to rebuild parts while they are still inside an engine.
Sharman says that AM is evolving fast and equipment is improving all the time. The industry has only really been around since the late 1980s and has transformed in the last five years. He is certain that it will keep changing.
“AM will, without doubt, be very significant in aviation. It will change the world in manufacturing and design. It has started happening today but it is not all going to happen tomorrow,” he says. “We are just at the start of the revolution. It is not a future technology, it is a technology of today, but there is a lot more to come.”