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How hybrid manufacturing will help plane companies make the most of 3D printing

Joseph Flaig

An Airbus A380 is assembled in Toulouse, France (Credit: Shutterstock)
An Airbus A380 is assembled in Toulouse, France (Credit: Shutterstock)

Planes in the Airbus A320 family weigh up to 75.6 tonnes, stretching up to 44.5m long.

Despite the aircraft’s scale, the European aerospace giant pumps 55 of them out of its factories every month.

That is set to increase to 63 a month by 2019, as the manufacturer seeks to meet a backlog that was reported to stand at 6,000 orders earlier this year. Even that could increase in future, as Airbus explores new technologies such as additive manufacturing (AM).

The manufacturer already uses the technique for some parts, including brackets and spacer panels. A talk at the recent TCT Show by the company's head of technology product management, José Ortiz, highlighted printed parts’ potential for wider deployment in cabins. But the technology could spread further through future aircraft thanks to an advanced new technique.

Novel designs

Also speaking at the TCT Show at the NEC in Birmingham was Nour Eid, a technologist from the Aerospace Technology Institute (ATI). Airbus already uses AM for local repair and services, he said, and the technology will lead to more customised parts in the near future.

Although 3D printing holds promise for those areas, they are relatively niche. The biggest benefits for the aerospace sector will come after the biggest commitments, said Eid.

Illustrating his point with a graph from the ATI’s recent Insight report into the topic, Eid walked through AM’s application in aerospace manufacturing. At first, companies identified components they could print. Then, they slightly improved their function and capability, cutting weight and cost from the parts.

The next step, and one that is within reach, is irreversibly redesigning components for AM to shrink assembly lines, use fewer tools and create less waste. After that will be multi-functional design, using hybrid manufacturing to embed systems and sensing within structural components to cut cost and weight across the entire aircraft.

The technique could reduce the thousands of components in an airliner, or improve reliability and performance of parts. But unfortunately, says David Wimpenny from the Manufacturing Technology Centre in Coventry, a number of major challenges remain.

Hybrid cubed

Hybrid manufacturing encompasses a number of techniques, including building something conventionally before printing on to it, or printing with AM before using traditional subtractive manufacturing to finesse the part.

Even more advanced is what Wimpenny calls “hybrid cubed”, printing two or more materials together into one component within the same printer. The process could be one of the most promising for aerospace, allowing the desired internal printing of sensor wires within wing spars, for example.

It is still “very early days,” Wimpenny tells Professional Engineering. “One of the biggest problems we have got with printing multi-materials is that we don’t have the design tools that allow particularly sophisticated designs of materials… they tend to specify the shape but not the material variation, because we’re not used to that.”

Even more fundamental issues lie beneath, says the chief technologist. “Most designers haven’t been brought up to think that they are going to start building titanium at the bottom and end with nickel at the top.”

A key engineering problem is that different materials – a metal and ceramic, for example – can have “wildly different” coefficients of thermal expansion, causing the different materials to expand at different rates and therefore weaken the interface between them. In the safety-critical aerospace sector, such an issue would be unacceptable.

The metal-ceramic hybrid part has been the Holy Grail in AM for decades, says Wimpenny, because the different material properties are suited for very different applications. One solution, he says, is a gradual combination of the two by ‘grading’ them together. “If you can grade and go for a mixture of materials at the interface, that prevents the strain from breaking the component. That’s increasingly become the direction of travel in AM.”

Other than the design, training and technical issues, standardisation and certification of material mixes remains a big issue. “You want to use them in really high-performance applications, which by their nature tend to be pretty unforgiving if a piece fails,” says Wimpenny.

One of the most promising projects is at the hybrid manufacturing group at the University of Leeds, he says. The project is reportedly about five years away from using layer-by-layer hybrid manufacturing for aerospace applications.

Beyond hybrid

“The most long-term view is looking at system level, fully integrated AM design,” says Eid. “So when we get to that 10-plus, 15-year timeframe and we are looking at developing completely new airframes for a single-aisle family, for example, AM really needs to be considered from the onset.”

The ultimate goal, says the technologist, is the ‘lights out’ factory, where robotic printers print hybrid, specially designed parts with minimal human intervention.

Hybrid manufacturing could also leave the atmosphere before long. Edinburgh rocket company Skyrora recently exclusively unveiled its 3D-printed rocket engine to Professional Engineering, and lead engineer Robin Hague said the technique would “very much be of interest” in future. “Currently, of course, parts have to be printed and then separately machined. Hybrid manufacturing will be very useful. It’s certainly something that we’re keeping an eye on.”

Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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