While the pandemic-induced supply chain crisis has eased in some industries, echoes still reverberate in aviation. As air passenger levels return to normal, orders for new planes are rising. Yet with aircraft deliveries marked in years, pressure is high to keep existing planes in the air rather than on the ground for maintenance.
As a result, MRO (maintenance, repairs and operations) concerns remain a key focus for aircraft OEMs and industry suppliers. For example, General Electric Co. recently said it plans to spin off some divisions and concentrate on aviation—including MRO. With supply chain issues continuing to hamper replacement part manufacturing—especially for critical, cast-metal parts that can take months if not years to deliver—many companies are taking a fresh look at additive manufacturing (AM) as a potential part of the solution.
The timing is good. Metal AM has reached a level of maturity that makes the technology a viable alternative for key aviation replacement part applications such as structures, turbine nozzles, vanes, blades and heat exchangers. The strength and quality of advanced laser-powder-bed-fusion (LPBF) parts exceed that of castings, with a density of 99.9%, mechanical properties approaching wrought values, and lead times of weeks versus months or even years.
Particularly with older aircraft, the necessary tooling may no longer exist or must be remade completely—with minimum order sizes making just-in-time strategies unachievable. Part-makers losing business opportunities have reached pain-point margins at which AM’s benefits of on-site, on-demand manufacturing and greater supply chain flexibility are tilting the balance to 3D printing. The most advanced AM system makers now provide material qualification, automated machine calibration, controlled parameters, real-time quality assurance monitoring and precise performance-data capture that can ease the burden of certification requirements.
Such high levels of AM production control have already proven their worth in rocket engines that have successfully launched unmanned spacecraft. Yet up until recently, because passenger aircraft are much more strictly regulated, most flight-critical AM parts in commercial aircraft have been painstakingly and expensively customized and certified by OEMs—often requiring years, or decades, and millions of dollars—making the process generally untenable for MRO.
But the picture is improving. Several AM equipment makers have been working closely with Metallic Materials Properties Development and Standardization (MMPDS) on material qualification for high-performance aerospace alloys. Backed by the FAA, MMPDS is the main source of statistically based, design-allowable properties for materials and fasteners used in commercial and military aircraft systems worldwide. Battelle, the program secretariat for MMPDS since 1956, anticipates that Velo3D’s LPBF 718 alloy will be the first AM metal to be approved for the MMPDS Handbook.
Eying certification, some AM equipment providers have moved into the applied-materials sphere—working with NASA on material-characterization builds of actual parts. The focus is on microstructure, porosity and other critical qualities, using alloys such as Ti64 and Inconel 625 and 718.
The most advanced AM system makers are incorporating such material data into built-in, machine process specification parameters, locking down common recipes that will deliver the same quality of parts from every AM build, regardless of location. This is already happening in the oil and gas industry, which has a turbo-machinery bond with aerospace: Production parts were printed on identical equipment makers’ carefully calibrated machines in different countries, meeting all design and performance specifications and demonstrating the achievability of distributed manufacturing while conforming to API20S standards.
Such projects are accelerating global standards for industrial metal AM. There’s no longer room for one-off process development that some equipment makers and their customers are undergoing. The pieces are falling into place, especially for aviation MRO, to bypass outdated barriers and consider AM as a more efficient way to qualify parts for flight.
Connect With Us
