Helicopter manufacturer, Bell prefers the fused deposition modelling rapid prototyping process, which builds parts in high performance thermoplastics, for its functional prototype building programme on the Osprey projectBell Helicopter manufactures the heavy-lift 'tilt-rotor' Osprey, a hybrid aircraft that combines features of both fixed wing and helicopter. It can lift off, hover and land vertically, yet it can cruise at high altitudes at jet speeds. When the aircraft recently underwent an experimental tail-wiring upgrade, technicians at the Bell XWorx rapid prototyping (RP) laboratory used Stratasys' fused deposition modelling (FDM) to build tough polycarbonate wiring conduits. The branching conduits in six mating sections were installed inside the Osprey's twin vertical stabilisers for ground-based wiring tests. We built the conduit for one stabiliser and this was installed on the mock-up, recalls RP technician, Mike Storp. It was successful, so a second set was requested for the other stabiliser. After some minor variations, five more complete sets were requested for a total of 42 conduit models. It took only two and a half days to make them all, Mr Storp continues. The FDM Titan RP system ran around the clock. Keeping control of the project in-house was important to Bell but, more importantly, FDM avoided the problem of having to wait six weeks for prototypes, traditionally cast in aluminium.The Stratasys FDM Titan system can model with polycarbonate (PC) and polyphenylsulphone (PPSF) thermoplastics, which work well for functional testing. Traditional epoxy-based RP processes were simply no match for FDM in this particular application. PC is dimensionally stable, has a high heat-distortion temperature, high tensile and flexural strength and a hardness exceeding that of ABS. PPSF, moreover, includes a V-Zero flammability rating, has the highest impact strength of any RP plastic, and resistance to fuels, acids and a variety of chemicals. FDM has strong points besides durability, but ease of post-processing is at the top of the list for me, says Mr Storp. With some other processes, it's frustrating what you have to go through. They might require three times longer in post-processing than it took to build the part. FDM is a faster, cleaner process. After removing the support material, no further post-processing steps are needed. All RP processes are easy when it comes to building the part, but with some of them you really have to stay on top of it after the part is built. They can be very messy and time consuming - a hassle we don't have with FDM. The use of FDM over the course of development of a new aircraft has the potential to reduce both costs and development time. This efficient process allows us to make more iterations than we could with other processes, Mr Storp claims. That results in better-designed components, which helps to build a better end product.