Engineering news
Engineers at the University of Southampton have built and flown what is being described as the world's first '3D-printed' aircraft.
The unmanned air vehicle was produced in nylon using an additive manufacturing technique known as selective laser sintering. It comprised just four parts – fuselage and rudder fins, nose cone and two outer wings – with the fuselage and wings housing a number of internal mechanical components.
The Southampton University Laser Sintered Aircraft project began life as a series of Solidworks CAD design drawings. These were passed on to 3T, a specialist rapid prototype firm, who incorporated the snap fittings required to hold the four nylon parts together to form the overall aircraft.
3T also designed mountings and channels to hold the ten internal components, enabling the motor, battery, avionics and controls to be clipped into place inside the main fuselage, and two servos, one in each wing. The wings had two ailerons moulded in with hinges and there were similar large hinged flaps on the rear control surfaces. All these features were incorporated into the aircraft’s design and were built as integral parts to the main components, reducing the need for additional parts to be fitted post-build.
Jim Scanlan, professor of aerospace design at the University of Southampton, said: “The entire structure of the aircraft was printed including wings, integral control surfaces and access hatches. No fasteners were used and all equipment was attached using ‘snap fit’ techniques such that the entire aircraft can be put together without tools in minutes.”
The flexibility of the laser sintering process allowed the Southampton team to re-visit historical techniques and ideas that would have been prohibitively expensive using conventional manufacturing. One of these ideas involved the use of a Geodetic structure, initially developed by Barnes Wallace and used on the Vickers Wellington bomber which first flew in 1936. This form of structure is very stiff and lightweight, but very complex. If it was manufactured conventionally it would require a large number of individually tailored parts that would have to be bonded or fastened at great expense. But Scanlan said that the selective laser sintering technique made use of the Geodetic structure possible.
He added: “Another design idea that laser sintering facilitates is the use of an elliptical wing planform. Aerodynamicists have, for decades, known that elliptical wings offer drag benefits. Heinkel produced the He 70 aircraft in the early 1930's which exploited such a wing. More famously Mitchell’s, aerodynamicist Beverley Shenstone selected this shape for the Spitfire aircraft of the late 1930's. The Spitfire wing was recognised as an extremely efficient design but it was notoriously difficult and expensive to manufacture.
“A direct contemporary of the spitfire, the German Messerschmitt 109, used a tapered wing that was slightly less aerodynamic but roughly half the manufacturing cost of the Spitfire wing. Again, laser sintering removes the manufacturing constraint associated with shape complexity and in our project there was no cost penalty in using an elliptical shape.”
Stuart Offer, sales manager at 3T, said: “This project took little more than a month to complete. With simplified assembly due to the internal design features, selective laser sintering was the ideal solution as it also offered tremendous strength despite the weight of the plastic parts being less than 2kg. The ability to produce complex yet lightweight components contributed immensely to the success of this project.”
