The Additive Manufacturer Green Trade Association (AMGTA), a global advocacy group focused on developing and promoting sustainable additive manufacturing industry practices, has published its first independent piece of research, titled “Comparative LCA of a Low-Pressure Turbine (LPT) Bracket by Two Manufacturing Methods”.

The report, commissioned by the AMGTA and authored by the Rochester Institute of Technology’s Golisano Institute of Sustainability, analyzed a commercial aerospace low-pressure turbine bracket via a life cycle assessment (LCA) – evaluating both the comparative manufacturing impact of laser powder bed fusion (LPBF) vs traditional manufacturing and the impact of a greater than 50% weight reduction of the bracket over the life of the aircraft. While the comparative result was inconclusive about which manufacturing method used more energy, the results confirmed the dramatic impact that light-weighting commercial aircraft engines and airframes have on carbon emissions.

Key takeaways

Using three separate methodologies, the LCA was inconclusive as to which manufacturing method (traditional or additive) used more energy. On balance, this neutral finding represented an improvement over previous studies showing higher energy used in LPBF manufacturing compared to traditional methods.

The study found that the biggest factor in determining the sustainability of production was a manufacturing facility’s energy mix at the location of generation, and whether that energy grid was produced using sustainable means.

The study very clearly showed that light-weighting aircraft components via AM design resulted in a dramatic reduction in carbon emissions over the life of an aircraft, with a reduction of 13,376 kg for every 1 kg of weight reduction.

The impact of light-weighting was, by far, the most important factor in determining that AM-produced components are more sustainable than a traditionally designed and manufactured part.

“The release of this peer-reviewed LCA – the first of its kind – represents a milestone for the AMGTA,” said Sherri Monroe, Executive Director of the AMGTA. “For the first time, we are able to publish tangible results demonstrating the importance of design in additive manufacturing when compared to traditional methods. This study demonstrates the very real impact that AM can have in aircraft and engine design of the future, and bodes well for using similar strategies in other industries and programs.”

Methodology

The two-year study analyzed the two brackets using three LCA methodologies, including the ReCiPe 2016 version 1.1 midpoint method, the Cumulative Energy Demand v1.11, and the Intergovernmental Panel on Climate Change’s IPCC 2021 GWP100 methods. Two of the three methods indicated that, strictly from a manufacturing standpoint, the traditional bracket required less energy to produce, while one method indicated that the AM version produced less carbon dioxide. In all cases, however, the results indicated that the energy mix of the underlying electrical grid had an outsized effect on the sustainability of the manufacturing process. The LCA was performed in accordance with ISO 14040:2006(E) and was peer-reviewed by EarthShift Global.

The underlying bracket, which is one of 12 on each of the two GE Aviation CF6-80C2B6F turbine engines powering a Boeing 767 aircraft, secures a fuel manifold to the external case of the engine’s low-pressure turbine module. It was selected by the AMGTA because it was a relatively simple part that is easy to access and locate. The additive design and manufacturing of the bracket was performed by Sintavia, in Hollywood, Florida, and printed on an EOS GmbH M290 printer using Höganäs AB Inconel 718 powder. The traditional part was manufactured by a Tennessee-based machine shop using a CNC process. The optimized AM bracket was over 50% (0.063kg), lighter than the original version. According to Sintavia, the optimized bracket outperformed the traditional bracket in terms of mechanical properties, with an increased fatigue life despite its reduced weight.

Conclusion

While the choice of the LPT bracket offered a simple demonstration of how light-weighting could work on an aircraft engine, the AMGTA believes that the lessons embodied in the current LCA could be much more widely adopted by airframers and engine manufacturers across multiple mechanical systems. Moreover, light-weighting methods of transportation using additive design technology are not only limited to LPBF, as other additive technologies (including binder jetting, directed energy deposition, and polymer printing) can similarly remove excess weight across vehicles, aircraft, and vessels.

“This study underscores the importance of using AM to develop optimized parts and components that have been light-weighted via AM technology,” said Brian Neff, CEO of Sintavia and the Chair of the AMGTA. “No other currently viable commercial technology offers such an immediate impact to carbon emissions as light-weighting aircraft parts via AM does, and we now have independently verified, peer-reviewed data proving so. We look forward to working with Boeing, GE, and all of the industry’s OEMs as they look to unleash the sustainable potential of AM across existing and future platforms.”

“The two phases of this study – production and use – have implications well beyond this specific bracket, airplane, or manufacturing sector,” added Sherri Monroe. “The negligible difference in environmental impacts during production combined with the benefits of on-demand production – when you want it, where you want it, how you want it – to deliver more resilient, efficient, and sustainable supply chains, have significant implications for the manufacturing ecosystem to deliver more sustainable solutions.”

“While this study has immediate implications for aircraft engine and airframe manufacture, the findings in the use phase extend to any part of an airplane that could potentially be light-weighted – mechanical systems, seats, service carts, galleys – and well beyond aircraft to any equipment moved by an engine or motor – vehicles, ships, trains, robots – although the energy demands for aerospace make it the biggest, most obvious, and most immediate beneficiary.”