by EOS, GmbH
It is not the first time that aviation history has been made in Southampton. It was in this city in the south of England that the brilliant designer, Reginald Joseph Mitchell, developed the Spitfire, the most famous British fighter aircraft in the Second World War. Happily, the more recent entry in the annals of aviation history is of a far more peaceful nature: The engineers at Southampton University have taken an innovative step in implementing their idea of an experimental, unmanned aircraft. They have developed a UAV, or unmanned aerial vehicle, using unique design and production methods made possible by laser-sintering technology. Last summer, the team successfully designed and flew the first 3D-printed unmanned plane, made entirely of nylon and known as the Southampton University Laser Sintered Aircraft – or SULSA for short.
Laser sintering offers structural freedom, meaning that designers can think in new ways. The design team from the University of Southampton wanted to build a UAV that was light and sturdy,with no structural restrictions in either design or production. By building with laser-sintering technology, they were able to use forms and structures in the construction of the aircraft that would have been impossible or prohibitively expensive using other manufacturing techniques.
“Essentially, what we wanted was to create something completely new and rather complex but using a method that was as fast, simple and cheap as possible. In itself, this is a classic trade-off. Because if you want to build something simple, the usual way is to employ parts that already exist. But since we had the opportunity to manufacture in 3D printing, we found a solution to the challenge quite quickly,“ says Professor James Scanlan, who heads the project together with his colleague, Andy Keane.
The basic framework data for the aircraft was soon determined. It was designed as a pusher, with an electrically driven tail propeller and a V-shaped vertical and horizontal tailplane. The drive components and energy supply had to be easy both to incorporate and to replace.
To implement the plan, the designers from the University of Southampton partnered with 3T RPD, who undertook the manufacture and detailing of the design, as well as supplying laser sintering knowledge and expertise. The whole project centred on the production of the structural components, using an EOSINT P 730 laser-sintering system made by EOS.
Laser sintering is a procedure by which components can be made directly from three-dimensional digital data. Before production, the data is sliced. The system then builds up the object layer by layer, using a concentrated laser beam that acts on a special powder and solidifies it.
By the end of the process, the Southampton team had successfully produced an aircraft according to plan, cheaply and quickly. The unmanned aircraft comprises four parts plus a component tray, which simply clip together. The airplane can be prepared for flight in no more than ten minutes. Clip fasteners for the internal components – of which there are only ten, including the engine, batteries, and avionics – are integrated in the fuselage.
PA 2200 plastic was chosen as the material as it keeps the weight of the aircraft low while offering a high degree of structural rigidity. The production procedure was followed by the only manual activity involved in the process: removing the surplus powder. Upon completion of the printing process, the parts were immediately ready for use. “This production method was the only way of creating the UAV in a development time of little more than a month, from the initial drawings to the successful maiden flight,” adds Stuart Offer, Sales Manager at 3T RPD. Spare parts can be made in a few days, no tools are required, and design alterations can be incorporated very quickly.
The unmanned aircraft displays great aerodynamic efficiency thanks to its form of construction. As a result of the production process and the materials used, the weight of the aircraft could be kept below three kilograms, despite it having a wingspan of approximately 1.2 metres. This is necessary because the electric motor of the pusher has a power rating of only 400 W. The performance specifications of the small aircraft are exemplary, largely thanks to its low take-off mass, and the engineers were able to achieve a maximum speed of 140 kilometres per hour. With a cruising speed of 70 kilometres per hour, SULSA has a range of about 45 kilometres or more than 30 minutes in the air. The control system was developed by Dr. Matt Bennett, who was also involved in the project.
“The flexibility of the laser-sintering process allowed the design team to re-visit historical techniques and ideas that would have been prohibitively expensive using conventional manufacturing”, says Scanlan. One of these ideas involved the use of a geodetic structure. This type of structure was initially developed by Barnes Wallis and famously used on the Vickers Wellington bomber, which first flew in 1936. This form of structure is very stiff and lightweight, but very complex. Scanlan adds: “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.”
Professor Keane notes: “Another design benefit that laser sintering provides, is the use of an elliptical wing planform. Again, laser sintering removes the manufacturing constraint associated with shape complexity, and in the SULSA aircraft there is no cost penalty in using an elliptical shape.”
Thanks to the laser-sintering technology, it was also possible to integrate the moving parts, such as the aerodynamic flaps and hinges, directly into the wings or fuselage in a single production step. “This means that there were no additional parts to attach after production, with the effect that SULSA contains absolutely no screws or rivets. The entire structure of the aircraft is printed,“ confirms Offer.
“The laser-sintering process allowed us to give the wings an elliptical form. Aerodynamics engineers have known about the advantages of this wing form for decades. By using laser sintering, we no longer had to consider the usual constraints that the production process places on this complex construction form. With SULSA, we were able to build elliptical wings, without falling victim to excessive costs.” James Scanlan, Professor at the University of Southampton
“We were able to conduct the project in less than a month from the initial draft design in May to the maiden flight in June. The internal design features were just one of the advantages of using laser sintering; a further benefit of the technique was the combination of rigidity and a low weight of only two kilograms. This made it possible for us to produce complex components with a lightweight construction.” Stuart Offer, Sales Manager at 3T RPD
EOS Tooling Video, EOS GmbH Electro Optical Systems-Laser Sintering Systems
Our sincere appreciation to Claudia Jordan and EOS, GmbH for permission to publish information about this exciting project and use of laser-sintering technology.
For further information:
Southampton is one of the leading entrepreneurial universities in the UK. It has eight faculties that cover a huge range of subject areas.
University of Southampton. www.soton.ac.uk
3T RPD Ltd
3T RPD Ltd was established in 1999 and has become a leading additive manufacturer throughout the UK and Europe. www.3trpd.co.uk
EOS GmbH Electro Optical Systems
Founded in 1989 and headquartered in Germany, EOS is the technology and market leader for design-driven, integrated e-Manufacturing solutions for industrial applications. EOS offers a modular solution portfolio including systems application know-how, software, process parameters, materials and its further development. The portfolio is completed by services, maintenance, application consulting and trainings. www.eos.info
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