This customized FAA-approved air duct was created using FST-compliant ULTEM 9085 thermoplastic on a Stratasys FDM-based 3D Production System
Orbis, an organization dedicated to providing ophthalmic training to communities around the world, utilizes airborne training facilities they have named Flying Eye Hospitals. Orbis’s goal is to eliminate unnecessary blindness, which afflicts 39 million globally and is preventable with proper medical care. The Orbis team performs eye surgeries and educates doctors in the proper execution of eye surgeries through two-way audio-visual links. To aid and instruct as many people as possible, Orbis’ entire hospital and training facility is housed on a converted MD 10-30 aircraft.
Stratasys had the opportunity to assist with this unique aircraft conversion, as Orbis began the process of building a new airborne hospital. Orbis began by reaching out to Structural Integrity Engineering (SIE), an aerospace company that re-designs, re-builds and re-claims old and unused aircraft. One of the more complex components needed for the new Flying Eye Hospital project was an air duct required to conform to certain curvatures as well as meet all FAA requirements for airflow. Its purpose is to filter air between the cockpit and the operating rooms. SIE chose to use additive manufacturing to create the customized air duct.
Why Additive Manufacturing is Flying High
The aerospace industry is increasingly using additive manufacturing to reduce material costs, decrease labor content, and increase availability of parts at point of use, which may have a dramatic impact on the supply chain. While aerospace was an early adopter of additive manufacturing technologies, the expansion and widespread use of 3D printing in aerospace in recent years is due to several factors:
- the ability to create complex and unique parts otherwise unachievable with traditional manufacturing
- construction of end-use parts with hollow cavities that lower a part’s overall weight without compromising on strength or mechanical performance or safety
- an emphasis on customization and small-scale production which is often needed for aerospace manufacturing
- and efficient manufacturing techniques which generate less waste, crucial to the expensive materials used in aerospace manufacturing
Shifting From Fiberglass to FDM
The 3D printed air duct needed to conform to the unique interior of the aircraft. It was seamlessly attached to the Flying Eye Hospital.
Mark Curran, Senior Engineer at SIE, has been working with additive manufacturing processes for years, but always as a way to prototype and test out new parts. During design and form & fit testing, Curran and his team realized that traditional methods of manufacturing ducts would not be ideal for the geometry of the air duct needed on the Orbis plane.
“3D printing processes are very viable for complex fitting and design, which would normally cost quite a bit if machined,” Curran said. “In discussing our needs with Stratasys Direct Manufacturing (previously known as Solid Concepts, RedEye and Harvest) Engineer Jesse Marin, he informed me that Stratasys Direct Manufacturing has material that is FAA compliant for smoke and burn regulations. We received samples of the material, ULTEM 9085, and did secondary burn tests. To pass, the samples have to extinguish by themselves within a certain amount of time. The ULTEM pieces passed the test.”
ULTEM is a thermoplastic material that has been engineered to meet very harsh environments, which is why the material has become widely used in the production of large vehicles such as automobiles, industrial equipment and aircraft.
The floor plan for the Flying Eye Hospital. Special areas include operating rooms and education areas where doctors can observe eye surgeries via two way audio-visual links.
“We took what we normally would’ve done in fiberglass and shifted our approach,” Curran said. Instead of fiberglass, Curran and his team chose to use the Fused Deposition Modeling (FDM) 3D Printing process coupled with the tan ULTEM material that worked so well for the team during testing. The success of the 3D printed material and the ability of the process to consolidate parts was met with a lot of enthusiasm from Curran’s team.
FDM is an additive manufacturing process in which thermoplastics are extruded in varying degrees of durability, layer by layer, until a final product is achieved. The process, as Curran explained, allows for multiple features to be built into the actual completed product, opening up possibilities for designers to program-in virtually any feature they require. Had Curran and his team manufactured the duct using fiberglass, the machined mold and lay-up process would have taken weeks; with FDM, the team was able to receive their part in a matter of days, and should they need a replacement or an extra part, the team could receive multiple parts in just a few days.
“We were able to design mounting feature attachment fittings into the actual part. The mounting features are usually separate. By designing them into the FDM ULTEM component, we were able to reduce our overall part count, which is always a good thing,” Curran said.
Evaluating the Part for Airworthiness
Stratasys Direct Manufacturing was responsible for achieving the FAA airworthiness certification for an additive manufactured part .
Building a part to function on an actual aircraft (versus a prototype or non-critical part) required vigorous inspection by the FAA. The FAA sent two representatives to Stratasys Direct Manufacturing to test and certify the design and build of the air duct. First, a Designated Engineering Representative (DER), who is commissioned by the FAA and carries a legal license for engineering, visited Stratasys Direct Manufacturing to verify the design of the duct would meet airworthiness requirements. A Designated Airworthiness Representative (DAR), who inspects the part to ensure everything was built correctly and that the process used meets all airworthiness requirements, visited once the duct had been built.
“Being responsible for FAA certifications opened our eyes to what additive manufacturing can accomplish,” Marin said. “We’ve always been dedicated to internal research, and improving manufacturing processes, and I think it really paid off in this project.”
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