GE Aviation’s Loyang, Singapore facility is reportedly the first maintenance, repair and overhaul (MRO) facility worldwide that has been approved to use metal additive manufacturing (AM) for commercial jet engine component repairs.
GE Aviation Engine Services Singapore (GE AESS) currently employs more than 1,700 employees in the city-state and accounts for more than 60% of GE Aviation’s global repair volume. GE Aviation is researching the MRO sector, and GE AESS recently announced that it is the first MRO facility in the world approved to perform metal additive repairs on jet engine components.
3D printed parts are typically printed using STL files generated from CAD drawings. However, this works only for new make production where the goal is to produce identical parts conforming to the blueprint. When repairing used parts, however, the repair has to be customized for each individual part because each part wears differently during service, GE said.
Additive technology in repairs also offers the possibility of embracing complexity, according to Chen Keng Nam, executive manufacturing leader at GE AESS in Singapore, who has also been involved in the metal additive roll-out.
“This disruptive technology can be used for lots of applications, not only in aviation. When I see beyond the realm of repair into new-make, it’s mind-blowing to see the parts that we can design and print using additive,” he said. “Now designers are making use of the ability to produce new designs that couldn't be imagined or manufactured before with traditional methods.”
Iain Rodger, managing director at GE AESS, also sees the potential for metal additive technology in MRO. “In this part of the supply chain our customers truly value faster turn-around time, and that’s what we are achieving,” he said. “Using our GE Additive Concept Laser M2 machines typically halves the amount of time it takes us to repair these aircraft parts.”
Blade repair
Rodger says his teams are already using additive technology to repair parts in GE Aviation’s CF6 engines, reportedly the best-selling commercial engine for wide-body aircraft. The next goal is to include parts on the CFM56, the best-selling engine in commercial aviation history.
One example is the repair of high-pressure compressor (HPC) blades that run at high speeds and tight clearances within aircraft engines. They face regular erosion and wear and tear that, over time, demand continuous repair and replacement. Repairing these blade tips used to require a long process of cutting, welding and grinding to create the proper shape.
GE Aviation has established an automated AM process to repair the HPC blade tips, saving time and costs associated with labor and machining. The team created image-analysis software that maps the shape of a used blade and creates customized instructions for the Concept Laser M2 machine to build a new tip with more precise alignment and profile.
According to the company, the 3D printed part is near-net shape and can be finished with minimal additional processing.
“Productivity has increased with our employees able to repair twice as many parts in a day compared to the conventional repair process. Less equipment is also needed for post-processing, so the floor space required is reduced by one-third,” said Rodger.
“Further to that we are currently assessing what we are going to do in turbine parts and other components beyond compressors. Day-to-day, working with customers, they will know that there's a difference as they will be seeing their parts return to them more quickly.
“To me one of the significant advantages of additive is its sustainability. This is going to allow us to repair more parts and throw fewer parts into the bin, use less energy, generate less waste and have a smaller footprint. Repair capability is a big part of the sustainability journey. As the industry expands and new technology is developed, that will only increase.”
As part of a national strategy, Singapore’s Economic Development Board supported the initial development trials and training for the introduction of metal additive technology for aviation maintenance into the country.
Shih Tung Ngiam, a senior engineering manager at GE Aviation, engine services in Singapore, was involved in the project from its inception, acting as a liaison between the local team and the wider additive community to industrialize the process.
“While teams at the GE Aviation Additive Technology Center in Cincinnati and GE Additive Lichtenfels in Germany worked on developing printing parameters for the Concept Laser M2 machine, our team here in Singapore focused on the modifications needed to make the process robust and production-friendly in a high-volume repair process,” he said.
The Singapore team designed tooling to prepare and print parts more efficiently and improved the repair process, including printing, pre and post-processing and inspection, GE said. Trials and tests were conducted to help ensure part quality and safety were adequate before the repair was substantiated.
In 2020 Ngiam and the research team also designed a pilot production line, including an automated powder recycling system, to help streamline the repair operation. While the COVID-19 pandemic disrupted the approach for a while, by 2021 its full-scale production line was ready to start.
“Additive gives us speed and productivity with less floor space required,” said Ngiam. “We gave a lot of careful consideration to how best to integrate the M2s into the rest of the repair line. We completed an assessment of which parts of the repair we should leave alone, which ones could benefit from additive and what other changes we needed to make to the repair process for it to make sense.”
The two big advantages that metal additive provides the site are speed and the near-net-shape product, GE said. This allows the team to improve productivity and reduce floor space required. Traditional methods for repairing HPC blades can involve a lot of effort to weld the blade and additional effort to remove the excess material. By using the Concept Laser M2 metal 3D printers, the repaired blade is closer to the final shape when it comes out of the machine, so it takes less labor and equipment to achieve the finished profile, according to GE.
With aerospace components, extensive analysis and testing are required before any repair can be approved, more so when new technologies such as AM are involved. GE AESS worked with GE Aviation Engineering to produce parts for testing and to establish a quality assurance process before the process could be approved. As the aerospace industry becomes more familiar with additive, the approval process could be streamlined, according to the company.
“The great dream of additive is to print spare parts on demand without even needing to have an inventory,” said Shih Tung Ngiam. “It’s true that it’s a few years away, but it will happen. But we must also recognize that change can take time, especially in our highly regulated industry, and we have to make efforts to prove that our new methods are as good, if not better, than what has gone before.”
