05.09.19
Additive Manufacturing within the Rail Industry
Source: RTM August/September
Dr Ian J. Coleman, principal engineer, safety, technical and engineering at Network Rail, describes the benefits brought about by additive manufacturing and 3D printing within rail.
Network Rail’s Safety, Technical & Engineering (STE) directorate is accountable for the delivery of research and development initiatives on behalf of the businesses and UK rail industry. During the current five-year control period (CP6), £245m will be invested in a balanced portfolio of short and long-term R&D projects that have a significant focus on asset sustainability. Projects will cover the whole railway system whilst seeking to address challenges encountered at various stages of the asset life-cycle.
Discrete defect repair
The complexity of interactions occurring within the wheel-to-rail interface can lead to the formation of discrete rail head defects such as squats and wheel burns. State-of-the-art trainborne inspection technologies are deployed for automatic early defect detection. However, the follow-up repair is heavily reliant on manual processes, which can be both time-consuming and variable. Network Rail handles 6,300 weld repairable defects annually with the average cost of rail replacement being approximately £2,500 per defect, or £16m annually.
Through a European R&D project Network Rail and partners undertook collaborative R&D to investigate the feasibility of a Discrete Defect Repair (DDR) system capable of automatically scanning, removing and repairing rail head defects. The project also investigated challenges such as reducing the conventional high preheat requirement to improve the efficiency of repair, helping minimise track access requirements.
The DDR process and resulting mechanical properties were tested, which proved the system as a feasible concept for further work. Network Rail is now commissioning the next phase of design and development, including applications for in-situ repair of switches and crossings.
Railway crossing improvements
Railway crossings are subject to much higher dynamic forces than many other track components so, to help mitigate against accelerated degradation, austenitic manganese steel (AMS) is used as standard due to its good combined wear and work hardening properties. Crossings are high value track components that can also have a significant impact on train operations should they fail or require maintenance in service. Improving durability within the wheel to crossing interface will help to reduce or even eliminate associated failure modes, minimise disruptions to passengers, extend asset life and reduce whole life cost.
Through the Shift2Rail R&D programme, Network Rail commissioned research on ‘large-scale additive manufacturing (AM) of railway crossings’. The aim of the project was to establish a suitable AM process to achieve enhanced material properties within the wheel to crossing contact region whilst ensuring high mechanical performance of the main crossing substrate. Initial trials demonstrated that Metal Active Gas (MAG) processes produced successful AM weld deposits and that the material properties largely exceeded those as required by industry standards whilst also demonstrating high work-hardening potential.
Vision and future opportunities
The aforementioned are just a few very specific areas of R&D associated with the use of additive manufacturing. The wider opportunity available to the industry is vast and Network Rail is embarking on a programme of R&D that aims to bring additive manufacturing closer to reality within the rail industry.
Additive manufacturing opens the possibility to remove limitations on component design, enable the use of novel materials for improved asset performance and reduce procurement lead times by enabling just-in-time manufacturing.
Additive manufacturing is beginning to be adopted at an industrial scale and highlight tangible opportunities available to the rail industry. Imagine a depot having the ability to ‘print’ components on demand or maintenance teams utilising automated technologies that can efficiently restore critical track assets back to as-new condition.
Network Rail, in collaboration with both UK and EU industry partners, is now investigating these opportunities and what it would take to completely rethink how track and S&C components are designed and manufactured to support long-term sustainability of the railway.