A housing part for a sensor, a fuel nozzle of an engine, ZipDose tablets, a spinal fusion system. These are all certified additively manufactured parts. Why is each part certified important for the entire AM ecosystem? How can a certified part lead to a certified process? In fields such as aviation where safety is the number one priority certification is both crucial and not easily attained. The American FAA (Federal Aviation Administration) and it’s European counterpart the EASA (European Aviation Safety Agency) hold the responsibility to ensure the safety of aircraft and passengers, this includes certifying the AM parts incorporated in the plane. The path to certification isn’t simple, manufacturers have to get approval of every step in the AM process and not just the final product, meeting all the requirements – the design, materials, the processes, and post-processing. Each of these intricate steps has to be qualified in order to maintain the safety standards.
Defining the Standards
Before discussing the certification process, there needs to be a definition of standards – universal specifications that can be applied to AM parts. “To date, the certification of aerospace parts is on a case-by-case basis, so there clearly needs to be a more streamlined and defined process for AM to grow,” said Bob Yancey, director of manufacturing industry strategy at Autodesk. One initiative addressing this need is the Standardization Roadmap for Additive Manufacturing Version 2.0 published by America Makes and ANSI, the American National Standards Institute. The initiative is aimed at developing industry-wide standards for industrial additive manufacturing, received funding from both the public and private sector, from the U.S. Department of Defense (DoD) as well as 320 individuals from various organizations. “Coordination of standards development activity in emerging technology areas is something that ANSI excels at, and we have been very pleased to partner with America Makes to define the standards needed to help grow the additive manufacturing industry,” said Joe Bhatia, president, and CEO of ANSI.
Another initiative, this time by SAE International is the AMS-AM (Aerospace Material Specification committee on Additive Manufacturing). SAE was tasked by the FAA to form a standards committee which will develop guidance material for certification of AM parts used on aircraft. The NIAR, the National Institute for Aviation Research, will be helping the sub-committee focused on polymers (AMS AM-P) in creating technical standards for the use of polymer additive manufacturing in the aerospace industry. David Alexander, Director of Aerospace Standards for SAE International, said, “Additive manufacturing will play a significant role in the technology needed to produce parts capable of service in critical and non-critical aerospace service. The important work done by SAE’s AMS AM-P subcommittee will help the industry move forward with this technology.”
A few days ago the Farnborough International Airshow (FIA), one of the largest shows in the aerospace industry, provided a look into additive manufacturing certification for aerospace. It’s not surprising that additive manufacturing was a big part of the show and with it the topic of certification. Kim Smith, vice president and general manager of Fabrication for Boeing Commercial Airplanes and Boeing Additive Manufacturing leader, addressed the company’s involvement with Morf3D: “Developing standard additive manufacturing processes for aerospace components benefits both companies and empowers us to fully unleash the value of this transformative technology”.
From Part to Process
When a part is certified, the manufacturing process used can be applied to future parts, in such a case it could be advisable to lock this process in for every item produced based on the certification. The issue manufacturers face isn’t the quality of the AM part but the volume of production that is spread over time (and some times geographies) which affects the ability to standardize. While in traditional processes, such as injection molding, once the production line is in place, the process remains fixed for a large number of units, in AM the units produced can change continuously returning once in a while to produce another of the certified items. If there is a change in process it is a problem. The change can be a result of manufacturing on a different machine, with a slightly different material or even just discrepancies in the same machine’s settings – making sure these variables are consistent is key to ensuring the certified process is the one that’s used each time.
By qualifying an additively manufactured part for Spirit AeroSystems, Norsk achieved validation for its Rapid Plasma Deposition (RPD) process, used for industrial production. Last year the FAA gave its official approval to Norsks’ AM produced structural part, certified for the Boeing 787 Dreamliner (up top) making it “the first commercial airplane to fly with certified additive-manufactured titanium parts in structural applications”. Now Norsk plans to integrate its Rapid Plasma method (below part and process) in the manufacturing process of Spirits’ Boeing 787 fleet, achieving not only serialized production but a validated production process, paving the way to more certified parts.
Another company working towards developing a standardized production process for aircraft is Oerlikon. The company is developing standard processes with Boeing, Lufthansa Technik, and RUAG (rockets rather than airplanes), specifically, achieving repeatable processes for aircraft maintenance, and repairs using additive manufacturing. The partnership between Oerlikon and Lufthansa is intended to conduct a year-long study, starting with additively manufacturing components which will be produced in 3 locations, using the same powder material and the same settings. This will provide a better understanding of the repeatability and consistency of the process and eventually help define the standards of AM parts for aircraft. Oerlikon and RUAG are working on an additively manufactured bracket for a payload fairing, which is a huge nose cone that’s meant to protect a rocket during launch into the atmosphere. Oerlikons’ CEO Dr. Roland Fischer, commented on the collaboration: “Through our ongoing collaboration with RUAG Space, we have identified opportunities to fine-tune the qualification and certification processes, which are crucial in ensuring consistent quality in production. We are confident, that our materials and additive manufacturing expertise will further grow this important partnership.”
Parallel to efforts made to qualify parts and processes, AM material manufacturers and machine manufacturers like EOS are working on qualifying materials. According to Scott Killian, business development manager for aerospace at EOS North America, a fire-retardant Nylon developed by the company was the first fire-retardant AM material to be approved by the FAA. Now EOS is working on qualifying other materials such as aluminum used for additively manufacturing aerospace parts. Part of their work is done through NextGenAM, a collaboration with Daimler and Premium Aerotec (above seat belt buckles – additive manufactured in titanium on an EOS machine).
Ken Davis, Director of Additive Technology at Carpenter discussed the certification process at FIA a few days ago. He described it as “a constant feedback loop,” where the manufactured outcome informs the development of the material. Most of the customers are looking for materials adjusted to their needs, leading to their own proprietary powder. While this allows the company certain freedom and creativity it can complicate the standardization process. Yet the material used in AM doesn’t stand on its own, the machine settings are an integral part of the material, the same material can be used with different settings achieving different characteristics. A material cannot be certified for a specific use without the certification of the process and vise versa, in AM all variables tie together. Even though certification is complex, once all the parameters are defined and consistent certification is just around the corner.