Additive manufacturing with metals holds unrivalled importance in aircraft production for quicker throughput times, more cost-effective components and freedom of design. Now a new range of benefits are emerging, including lightweight construction, bionics and a fresh approach to design.
A bracket connector used in the Airbus A350 XWB was honoured as a finalist in the running for the "2014 German Industry Innovation Award." Previously milled from aluminium the part is now printed in titanium, making the bracket significantly lighter than before.
But what does the change in manufacturing strategy mean for aircraft manufacturing as a whole in terms of prospects and technology?
In a recent panel discussion, Prof. Dr.-Ing. Claus Emmelmann, CEO, Laser Zentrum Nord GmbH, Hamburg, Frank Herzog, CEO, Concept Laser GmbH, Lichtenfels and Peter Sander, Head of Emerging Technologies & Concepts, Airbus, Hamburg, spoke about how 3D printing is enabling “bionic” aircraft designs.
“Our primary objective is to reduce weight,” explained Sander. “This approach helps our customers, the airlines, operate their aircraft more economically. Additive layer manufacturing or laser melting with metals, also known simply as 3D printing, allows us to design completely new structures. They are actually more than 30% lighter than conventional designs realized using casting or milling processes. Another factor is that we can proceed directly from 3D designs to the printer, that is, the laser melting system. Usually tools are required to manufacture aircraft parts – this is now no longer the case for us. This saves money and shortens the time until the component is available for use by up to 75%. To cite an impressive statistic: previously we budgeted around six months to develop a component – now, it's down to one month.”
Emmelmann added: “The advantages for structural elements used in aircraft are obvious. The high degree of geometrical freedom of design enables more effective lightweight construction solutions compared to conventional approaches. For the brackets we're currently focusing on, this means a considerable weight reduction, which in turn translates into lower fuel consumption and the potential to increase the load capacity of aircraft.”
So how exactly has the additive manufacturing process changed the project process? What are the effects of moving from traditional milled or cast components to 3D printed components?
Emmelmann commented: “Since tools are not required in the process, it's now possible at an early stage to produce functional samples of components that are very close to being ready for series production without incurring the high cost of tools or other pre-production expenses. This means that sources of error can be identified in the early stages of the design process, which allows for optimisation of processes within the project as a whole.”
Sander suggested: “Milling of aircraft parts in particular results in up to 95% recyclable waste. With laser melting, we produce components with "near-final contours," which are associated with waste of only around 5%. This makes the process especially attractive when valuable and expensive aircraft materials, such as titanium, are being used. Compared to casting, we have the additional advantage of not requiring any foundry tools.”
Cabin bracket for the Airbus A350 XWB made of Ti, manufactured using LaserCUSING
Herzog said: “In addition to reduced resource consumption, the freedom of design enjoyed by aircraft engineers is also quite attractive. The ability to economically keep component density under control and determine the microstructure quality are additional aspects. Another fundamental quality feature is the ability to define the force distribution within the component, which is often impossible with conventional parts or is considerably more difficult to achieve.”
Weight reduction is perhaps the most significant advantage of 3D printed parts. Shapes can be optimised to use the least amount of material possible that will give the same effect as a traditionally manufactured part. So are there any limits to this?
“When it comes to metals in aircraft construction, welding is the most common process,” explained Sander. “Aircraft manufacturers have long been familiar with it. From experience, we know how welded components must be handled to satisfy the high safety requirements. However, we still have to learn how best to take advantage of implementing the new geometrical freedom in component design. Toward that end, we will have to perform many structural tests and trials over the coming years. The result will be a novel "bionic" aircraft design, I'm sure of it.”
Sustainability is a key concern for the aviation industry as aircrafts are expected to operate for a long lifespan crossing decades. Therefore the manufacturing of spare parts in low batch sizes is imperative to the efficiency of the industry.
“Since February of this year, Air Transat in Montreal has been flying with the first spare part printed and delivered by Airbus,” revealed Sander. “The former manufacturer of the injection-moulded part for a Cabin Attendant Seat in an A300/310 was no longer available; the tools had been scrapped. At that time, the question we faced was whether to invest in new tools, at a cost of US 36,000, or to take advantage of 3D printing. By using the laser melting process, we were able to offer the part at a cheaper price from the outset, without tool costs.
“Additive manufacturing is generally characterised by various aspects: decentralised, rapid turnaround, quick time from implementation to the finished component,” explained Herzog. “It allows for lower logistics and warehousing costs. It uses fewer resources than conventional manufacturing methods, which makes it a green technology. Even production-on-demand is possible. We also have to consider the small lot sizes common in aircraft manufacturing, which are another factor in favour of an additive process.
Emmelmann said: “The comparatively small unit quantities involved in aircraft manufacturing favour laser additive manufacturing techniques. The additive manufacturing process does not allow us to take advantage of any economies of scale, as is the case for other production methods.”
Looking to the future, the opportunities for additive manufacturing in the aircraft industry are promising with increased sustainability and the opportunity to develop and integrate various functions such as cooling components into parts. The capability to produce an entire assembly in a single piece and integrate functionality show that laser melting will add pivotal benefits to the future of an industry set to double in capacity in the next 20 years.
Sander said: “If development continues in a similar manner, I see no technical restrictions. The decision will then ultimately be based on cost-effectiveness and on the industrial availability of metal powders and high-speed machines.”
Emmelmann concluded: “We won't be printing complete aircraft, even in ten years. But I'm confident that in the future laser additive manufacturing will be capable of producing increasingly larger and more complex components in a cost-effective manner. This will be possible thanks to the rapid pace at which the system technology is being further developed, and the increased productivity associated with such advances.”