With ongoing technological advancements in metal and polymer 3D printing systems, regulated industries have seen an increase in additive manufacturing adoption rates. One such sector is aviation, where a few major players take the lion’s share of the market. Companies like GE, Boeing, and Airbus have all had their fair share of run-ins with 3D printing, but what kinds of components are actually being fabricated?
The Federal Aviation Administration
When it comes to flight-critical components or components where performance is crucial if the aircraft is to operate reliably, they must receive FAA certification before they are allowed to be installed. One of the first 3D printed components to receive the certification was the LEAP fuel nozzle, which is featured in GE's GE9X jet engine. The famed engine now contains over 300 individual 3D printed parts, including temperature sensors and fuel mixers, and larger parts, like heat exchangers, separators, and foot-long low-pressure turbine blades - all serving to save weight (and fuel) via geometric optimization.
The engine recently completed its first test flight on a Boeing 777x airliner, which is the world’s largest twin-engine jetliner and passenger plane. Two previous attempts at getting the 777X airborne were made, however, the tests were postponed due to high winds. In January of 2020, however, the airplane took off from Paine Field in Everett, WA.
Honeywell Aerospace, the aerospace division of conglomerate Honeywell, also recently received an FAA certification for one such 3D printed component. The part in question – a #4/5 bearing housing – is a key structural component of the ATF3-6 turbofan engine found in the Dassault Falcon 20G maritime patrol aircraft. The part is already in production and has been installed in an operational Falcon unit, with dozens more expected to be printed by the end of the year.
Over in academia, Auburn University’s National Center for Additive Manufacturing Excellence (NCAME) recently received a $3M grant from the FAA, which it will use to commence a two-year research project to improve air travel. Specifically, the NCAME engineers will delve deeper into metal 3D printing and its materials to fine-tune the parameters required to print end-use components for commercial aircraft.
Under the hood, the Auburn project is ultimately intended to solve a core issue in additive manufacturing, which is variability in performance. Variability results in identical parts 3D printed on different machines having discrepancies in their mechanical properties. According to the NCAME, there is also a lack of understanding when it comes to the microstructures of 3D printed metal parts, and their subsequent effects on fatigue and fracture resistance. This makes it very difficult to define specifications and standards in the industry – especially with tightly controlled parts for sectors such as aviation.
3D printing polymers for aviation
While metal components certainly dominate the aviation industry, 3D printed or otherwise, there are of course polymer parts making their way into the sector too. Boeing very recently qualified 3D printer OEM Stratasys' Antero 800NA thermoplastic filament for flight parts. As such, the PEKK-based polymer can now be used to 3D print end-use components aboard Boeing's planes.
Antero 800NA is a high-performance PEKK-based polymer designed specifically for Stratasys’s industrial-grade FDM 3D printers, such as the F900 and the Fortus 450mc. It is also available as a material option for customers who opt to use the company’s on-demand manufacturing service, Stratasys Direct Manufacturing. The other filament in the Antero family is 840CN03, a close relative with electrostatic dissipation qualities.
With a tensile strength of 93MPa and an elongation at break of 6%, 800NA aims to combine the excellent mechanical and low outgassing properties of PEKK with the design freedom of FDM 3D printing. The high strength, heat and chemical resistance, toughness, and wear resistance of the filament make it an excellent jack-of-all-trades alternative to metals such as aluminum for aerospace applications.
Elsewhere, researchers from the University of Sheffield’s Advanced Manufacturing Research Centre (AMRC) have previously used 3D printing to aid in a large-scale manufacturing project for Airbus. The AMRC engineers were commissioned to work on a high-precision drilling operation involving carbon fiber, aluminum, and titanium aerospace parts.
With aerospace-grade tolerance requirements, it was crucial that cross-contamination did not occur between any holes produced during the project. The team realized that they needed drilling caps to cover up the holes, but couldn’t opt for traditional machining or injection molding as this would cause weeks of delays. With only 10 days left to produce 500 caps, the engineers turned to Formlabs’ 3D printing technology and cut the lead time down by weeks to just two days, meaning the project remained on schedule and within budget.
The next steps for aviation
Much like medical and the wider aerospace industry, the aviation sector will always have stringent quality requirements. Seeing as 3D printing is in its relative infancy, this is the major hurdle that still needs to be jumped. While the field as a whole is rapidly warming up to additive manufacturing technology, there still needs to be a heavy push towards the development of standards and widespread practices before 3D printing can begin to transition from novelty to the norm.