Catapulting Into the Skies: 3D Printed UAV Soars With Electric Ducted fan Engines
The Advanced Manufacturing Research Centre (AMRC) was established in 2001: it is a collaboration between England’s University of Sheffield and Boeing. Since its inception, the AMRC has grown considerably, and since 2008 its facilities have included the Rolls-Royce Factory of the Future, which was further expanded in 2012. The AMRC has grown not only in physical size, but its Design and Prototyping Group (DPG) has earned a worldwide reputation for innovation. This past March, the DPG unveiled a prototype unmanned aerial vehicle (UAV) which they had designed, manufactured, and successfully tested.
The original UAV was ultimately a glider, designed to be a low-cost airframe. Following design and CAD modeling, the team constructed the glider of ABS plastic, comprised of only nine unique parts, each of which was 3D printed using fused deposition modeling (FDM) technology on the Stratasys Fortus 900 mc machine. This production process was deemed superior to stereo lithography or selective laser sintering because FDM allows for lower material and equipment investment costs, and a more simplified production process for printing the fairly large pieces required to create a full-on UAV. The finished airframe had a 1.5-meter wingspan and weighed less than 2 kilograms (that’s about a 5-foot wingspan and total weight under 5 pounds to those of us using American measurements).
While the FDM printed glider was a great achievement, the AMRC knew they could continue to up their game and so the Design and Prototyping Group gathered themselves together to go one further: they took the glider model and powered it. Debuting in October at the SAE conference in Salt Lake City, the team presented a new UAV that uses electric ducted fan (EDF) engines to give it powered flight.
The new, powered UAV was a huge milestone for the AMRC, and the project — which included a successful test flight on the very first try — represents a major step forward for rapid manufacturing (RM) technology. Small- and medium-sized producers can use the techniques developed to even further reduce time, materials, and costs required to 3D print components used in both prototyping and final product creation.
“Understanding and playing to the strengths of RM processes is the key that allows us to continually develop exciting, tangible products. The UAV highlights how the AMRC’s Design and Prototyping Group strive to push the limits of design for RM and more importantly, coupled with demonstration of function, help to make the transition from theory to reality,” said Mark Cocking, the DPG’s Lead Additive Manufacturing Engineer.
The EDF propelled UAV, while a significant achievement, is not the final design the DPG has in mind; they hope to continue to develop their capabilities and eventually produce a model powered by gas turbines. UAVs powered with EDF are about the same size and have similar installation requirements as will gas turbine-powered models, making EDF a perfect stepping stone toward the next development.
Using what they learned on the glider model, the team made a series of CAD designs. FDM was used (again printed via the Fortus printer) for the center body, wing end ribs, elevons, and wing tips; as was carbon fiber (using Vacuum Infusion) for the wing skins, “duck” tail, intermediate ribs, and access hatch. By combining these manufacturing techniques with a curing resin (cutting the need for autoclave curing), direct form CAD manufacturing allowed for precision in each part’s production. This UAV required spot-on symmetry and perfect design geometry to ensure operation, and conventional techniques (subtractive manufacturing) could not closely guarantee the perfection possible in additive manufacturing.
Asymmetry in the center body could have spelled doom for the EDF system, while any asymmetry in the wings could have impacted level flight capabilities. Not only did the parts have to be produced to exact specification, they had to be assembled accurately; all relevant parts were thus designed to self-jig to upper and lower skins, bonded together with structural adhesive. The printed wing root and tip ribs, intermediate (carbon fiber) ribs, and main spars were all critical here. Fortunately careful in their design and assembly, the UAV was printed and pieced together perfectly.
The design team understood that a powered UAV would necessarily weigh more than a propulsion-system-less glider, but still set themselves a strict weight limit of 5 kilograms (about 11 pounds); the finished weight of the EDF UAV came in at approximately 3.5 kilograms (less than 8 pounds). Still, this was heavier than the glider model, and so a different technique was necessary to get the drone into the air. The team designed their own custom catapult for the launch, including FDM-printed carriage and release mechanism. The carriage locks the UAV into place on the catapult prior to launch, and allows the motors to get up to full power prior to launch so they’ll be ready to go immediately as flight begins.
Before taking to the skies, a test launch on the shop floor tethered the UAV to a zip wire. If the catapult didn’t propel properly, the engines didn’t power correctly, or any other of a thousand variables, the UAV would be saved by the wire from a shop floor crash. Tethered launches, though, went off without a hitch, and after those successes it was time to take the tests off the tether.
Check out this video of the very first catapult launch and test flight of the EDF powered UAV:
The project, it seemed, was a soaring success.
Dr. Garth Nicholson, Senior Design Engineer, said:
“The project was a success on all levels from team building, experience gained in structural and systems design, design for manufacture through testing and validation of CFD. The aircraft was developed using both an incremental design philosophy, as well as trialing experimental manufacturing techniques in carbon fiber production.”
The AMRC is going to continue on its R&D path, buoyed by recent successes. The ultimate project goal? A fully autonomous UAV with a 3-meter (almost 10-foot) wingspan. Let’s hear your thoughts on the team’s accomplishments. Discuss in the 3D Printed UAV forum thread on 3DPB.com.
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