Rolls Royce is unique for its patented manufacturing process of its hollow wide-chord titanium fan blades. To make these fan blades light and strong the fan blades are made from titanium 6-4 alloy with a hollow internal “Warren–Girder” structure. This is done using 2 processes namely Superplastic forming and Diffusion bonding. The manufacture process starts with 3 sheets of forged titanium. A material called stop-off is printed onto 2 of the sheets which will stop them from joining together in the diffusion bonding process. The 3 sheets are then sandwiched together, and placed in a Furnace where the diffusion bonding takes place. A Flat sheet is produced and all layers are joined except in areas where stop-off has been applied. Thereafter, the Flat sheet is shaped at high temperatures, in a super plastic forming process. High pressure gas is blown between the sheets, very much like blowing up the balloon forming the fan blades aerofoil shape. The Central sheet is stretched and forms the girder structure. After which the aerodynamic shape of the blade is cut out of the plate, the root fixings are machined and the blades surface is polished to make the surface smooth to ensure the engine is as efficient as possible by reducing the surface drag. Processes used in manufacturing Fan Blades
* Application of stop-off
Stop-off material is a chemical used to prevent diffusion bonding on areas where it is applied. It may be made of the following materials, such as yttria boron nitride, graphite or alumina. In the application of stop-off for manufacturing, the chemical is printed onto the metal to form a pre-determined pattern such that, during super plastic forming, when the inert gas is blown through the gaps of the material where the metal is not joined, it will cause the Girder structure to be formed internally. * Diffusion Bonding
Diffusion bonding is a method of joining metallic materials, based on the principles of the atomic diffusion of...
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