Written by Peggy Jones & Daisy Martlew
Andrew Sandeman, who is in his second year of PhD research at NSIRC (sponsored by TWI CRP and awarded by Loughborough University), was awarded one of three runner-up prizes for the TWI Industrial Impact Award, held as part of the NSIRC 2019 Annual Conference. The aim of Andrew’s research is to optimise the design of a plasma cathode, which will reduce maintenance of Electron Beam (EB) guns and increase manufacturing productivity in the aerospace and automotive industries.
Although EB guns have been widely used since the 1950s, the constant demand for industrial innovation puts pressure on their capabilities: current and future manufacturing goals require high-integrity processing. Conventional EB guns are inconsistent, due to how acutely sensitive thermionic emission is to the cathode surface. This leads to wear on the cathode, which limits its lifetime before it must be replaced: typically a few hours to days for welding. This adds extra cost to the process, as well as introducing another variable: despite calibration, each cathode introduces a different beam consistency.
Replacing the cathode so frequently also introduces a risk of incorrect gun setup. As cathode lifetime is further shortened if the gun vacuum is compromised, harsh production environments are not feasible: a consistent vacuum must be maintained in order to produce reliable results.
TWI has been developing plasma cathode electron beams (PCEB) to address the need to improve weld quality and productivity. Plasma cathodes are resistant to the wear mechanisms that affect conventional EBs, such as cathode wear, erosion of the thermionic emitter, and poisoning from residual gas. This technology is still subject to deficiencies: Andrew’s PhD research focuses on optimising its design to achieve maximum beam current.
Through modelling a plasma cathode, and verifying the results with experiments, Andrew is not only working to improve industrial precision, but also sustainability. Within the aerospace industry, there is a drive to reduce CO2 emissions during the building and operation of aeroplanes. The materials creating these emissions are becoming more costly and scarce, so it is in the interest of both industry and the environment to adopt technology which can reduce wastage of raw materials.
The newfound precision of PCEB reduces the risk of error and wastage. When used in additive manufacturing, PCEB allows manufacturers to redesign aeroplane parts to have minimised weight, improving fuel efficiency and further lowering costs and emissions. The current by-to-fly ratio in the industry is 10-to-1 or higher: additively-manufactured freeform design components could be a solution to this problem, in terms of both wastage during production, and emissions during use.
Application of PCEB to the automated welding of turbochargers within the automotive industry could also prove beneficial. They improve the efficiency of combustion engines, reducing carbon emissions and pollutants.
Both industries, and others, will benefit from the lesser operational demands PCEB makes on them: it can be operated in coarse vacuums, as part of automated production lines, and offers reduced down-time, maintenance, and calibration. Andrew’s efforts will provide a more in-depth understanding of how plasma cathodes operate, thereby clarifying the factors which define its repeatability and performance.
Andrew’s recognition in 2019’s Industrial Impact Awards celebrates his, and other students’ research making a significant contribution or innovative approach to solving an industrial problem.
Andrew said “my experience so far of studying at NSIRC has been quite unique and has made me more independent. On the one hand it’s challenging for me to have no other students working in a similar field; on the other, I think the diversity of the research undertaken here reflects the wide range of industrial needs we are trying to tackle.
It is very exciting to know that my research is at the cutting-edge of industrial capabilities, and if my research is successful its impact could be magnified by industry. Additionally, I’m grateful for the excellent laboratory facilities and practical support from technicians, as well as the computer I can use for running long simulations.
Currently I’m planning to do more research into plasmas after my PhD. Plasmas is also a diverse field so I’m sure I’ll be able to find another exciting topic. I would also like to continue to develop my computational skills and apply them in research”.
For more information on NSIRC and opportunities available visit: nsirc.com.