TUBE NEWS 2016 May 2016 - Page 42

Welding makes major impact on 3D printing technology Fig 1: Titanium alloy airframe wing spar created using robot control of GTAW Since 3D printing was introduced there have been a number of developments, but the more recent use of fusion welding as a deposition source has opened up wide ranging possibilities in manufacturing. Because of the high cost of titanium there are clearly huge financial incentives: the aerospace industry estimates requirements of about 20 million tonnes of billet material over the next 20 years. Conventional manufacturing strategies need reconsideration. The process is one in which metal is deposited layer-by-layer to form a three dimensional shape (Fig 1). Various melting techniques have been used to achieve this aim including electron beams and lasers but one being actively pursued currently is Wire and Arc Additive Manufacture (WAAM) using a GTAW (TIG) power source. BAe Systems in the UK is working at RAF Marham to engineer ready-made parts for four squadrons of Tornado GR4 aircraft, including protective covers and guards. The WAAM process has been used by BAe Systems to produce a 1.2 metre long titanium alloy wing spar. Driving Forces Behind the Development of WAAM Electron beam and laser technology has been used with considerable success but this route to manufacture involves capital equipment that is expensive to purchase and to operate. Further work using these techniques is being undertaken in the UK, Germany and Sweden. A much more practical approach has been to use a standard arc welding procedure, usually with a GTAW (TIG) torch. The primary driving force behind the development is the potential to make huge savings in materials and therefore costs. One specific area of application is in airframe manufacture. The component in Fig 1 is made currently by machining from a solid billet or forging but over 50% of the original stock is lost as swarf. Another area under consideration is landing gear production where a cost saving of 70% is expected by using additive manufacturing. TN MAY 2016 Early work at Cranfield University for Rolls-Royce targeted aero engine applications. Researchers here developed the wire + arc deposition process to examine the use of Inconel, titanium, aluminium 42