Whatever the structure and customs of the aircraft aftermarket, a slow but steady revolution is taking place in the parts themselves. Additive manufacturing will bring increasing counts of metal parts that are cheaper, produced on demand rather than expensively stored, integrated rather than assembled, lighter and better performing. Major aerospace OEMs are pushing these improvements as fast as technology, economics and regulation allow.
Arconic Engineered Structures already has four agreements with Airbus to additively manufacture non-engine metal parts. “We see tremendous potential for metal AM parts in aircraft systems,” says President Jeremy Halford. “AM is quickly becoming one of the most sought-after technologies in aerospace. Customers want it because it promises lighter, more complex airframe and engine components, produced cheaper and faster.”
Airbus tapped Arconic to print titanium fuselage and engine pylon components for commercial aircraft in April 2016. Two additional agreements for printed titanium and nickel super-alloy components on A320-family aircraft were signed in December 2016.
The first Arconic 3D component, a titanium bracket, was installed in September 2017. In November 2017, Arconic and Airbus agreed to jointly develop processes for printing large-scale, structural metal components, such as spars, using high-deposition rate technologies.
The $13-billion-a-year supplier works with several additive metal technologies, including powder bed, high deposition rate, electron beam and hybrid. “High deposition rate is ideally suited for larger components such as pylon, spar and rib structures because it prints up to 100 times faster than powder bed used for smaller, more detailed parts such as airframe brackets,” Halford says.
Arconic also has its own proprietary process, Ampliforge, a combination of traditional forging and additive manufacturing to achieve wrought properties in some parts. Ampliforge is designed to increase toughness, fatigue and strength, while reducing material use and lead times.
Halford says additive is now best suited for parts where it can reduce materials and costs, or consolidate multiple parts into one. Next will come the opportunity to completely redesign parts that could not be manufactured by traditional methods. Arconic is following this evolutionary path in its work for Airbus.
Another $13-billion-a year OEM, Britain’s GKN, is already delivering flying titanium AM parts for secondary structures and is working towards more critical applications, says Marko Bosman, chief technologist for additive manufacturing in the aerospace division. “GKN sees many opportunities for metal AM for aerostructures, typically titanium parts combined with composites and multifunctional parts with complex designs,” Bosman says.
One major reason: increased use of composites means aircraft demand for titanium is also growing, but conventional titanium production is exorbitantly expensive. “AM enables efficient, light-weight designs for titanium parts,” Bosman argues. “But AM for aluminum alloys is not yet economic except possibly for special parts like heat exchangers.”
The Royal Netherlands Air Force has been flying with GKN’s printed ladder bracket on a helicopter since January 2017. The part is 40% lighter but stronger and more durable than the original design and less costly to maintain. The OEM has delivered a rocket engine nozzle that reduced part count by 90%, costs by 40% and production time by 30%. GKN printed parts are also flying on Saab aircraft.
“Good candidates are components that are currently machined with high buy-to-fly ratios or assemblies of parts that can be integrated in a single part using AM,” Bosman says. “Like-for-like replacements of existing designs seldom make a good business case. It is better to design the part with AM in mind to reduce cost and weight.”
Like Halford, Bosman sees powder bed best suited for small, complex parts and deposition using wire or powder for larger parts. “Further, you can combine different AM technologies.” How long will it take to fully exploit AM potential? “There will be a lot of AM parts in the next clean-sheet aircraft design, making full use of the design freedom AM offers to lower weight and increase performance.”