Unmanned Systems Technology 004 | Delair-Tech DT18 | Autopilots | Rotron RT600 | Unmanned surface vehicles | AMRC | Motion control | Batteries

59 Manufacture The key driver for the UAV was that it should have a short manufacturing lead time, and for that reason the DPG team has used a filament deposition moulding (FDM) machine, a Stratasys Fortus 900mc. FDM is an AM process in which a plastic or metallic filament is heated until it is molten, then deposited by an extrusion nozzle onto a flat build base and layered to produce a 3D component. It was chosen because of its simplified, and subsequently faster, build process and lower material costs compared with those of stereolithography or selective laser sintering. The FDM machine used by the DPG is capable of manufacturing parts from a range of polymers, and for this UAV the team chose to use acrylonitrile butadiene styrene (ABS) M30, a derivative of standard ABS thermoplastic. It was chosen because of its higher tensile, impact and flexural strengths than those of standard ABS, and its greater layer bonding strength. The UAV’s airframe has nine parts – two wings, two elevons, two spars, two wing end fences and a central spine – and the airframe has been designed to split into two halves along the spine, allowing a larger wingspan to be built within the FDM machine’s build envelope. The machine can manufacture components up to 914 x 610 x 914 mm (36 x 24 x 36 in), and the DPG exploited this to give the UAV a wingspan of 1513 mm, a wing depth of 77 mm, a nose- to-tail length of 700 mm, tip plate height of 150 mm, elevon length of 548 mm, maximum elevon width of 115 mm and a maximum elevon depth of 22 mm. Usually, an FDM-built aircraft would need support material around its components to prevent the airframe from deforming during manufacture, but this adds to the material costs and significantly increases build time because the FDM machine has to switch between its build and support AMRC | Dossier of it The key driver for the UAV was that it should have a short manufacturing lead time, and for that reason the DPG team used an FDM machine Unmanned Systems Technology | Autumn 2015 All of the glider version’s components were additive manufactured at the same time