Structural Integrity Engineering (SIE) is an aerospace company that re-designs, re-builds and re-claims old and unused aircraft. One of the more complex components needed for 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 a 3D Printing process to produce the air duct.
Mark Curran, Senior Engineer at SIE, has been working with additive manufacturing (3D Printing Machine) processes for years, but always as a way to prototype and test out new parts using Stereolithography (SL). During design and form and 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.
“We had done work with Stratasys Direct Manufacturing in the past because 3D printing processes are very viable for complex fitting and design, which would normally cost quite a bit if machined,” says Curran. “In discussing our needs with Stratasys Direct Manufacturing Engineer Jesse, 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, 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 automotives, industrial equipment and aircraft. “We took what we normally would’ve done in fiberglass and shifted our approach,” says Curran. Instead of fiberglass, Curran and his team chose to use 3D Printing process Fused Deposition Modeling (FDM)coupled with the tan ULTEM material that worked so well for the team during testing. “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.” 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 and works similar to a hot glue gun, extruding thermoplastics varying in 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.
Stratasys Direct Manufacturing proudly took on responsibility for ensuring the duct met FAA airworthiness certifications. Building a part that would be required 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,” stated Stratasys Direct Manufacturing’s Project Engineer Jesse Marin. “We’ve always been dedicated to internal research, and improving manufacturing processes, and I think it really paid off in this project.” Stratasys Direct Manufacturing successfully received an 8130 certification for their additive manufactured duct.
The Orbis team has never before used a 3D Printed unit on one of their Flying Eye Hospitals. The completed duct is 30” x 12.08” by 17.65” with a volume of 139.21.
An earlier prototype of the air duct has been awarded a place in the National Additive Manufacturing Innovation Institute (NAMII) in Washington, D.C., to display the capabilities of 3D Printing and transfer those visionary and realistic ideas to the mainstream U.S. manufacturing sector.
Jack Mc Hal, MD 10 Program Director of Orbis International, commented that their objective “is to build the most sophisticated, technologically advanced, state of the art, gold standard hospital platform”; Stratasys Direct Manufacturing’s additive manufacturing was able to meet those standards.