Browsing by Author "Dhokia, Vimal"

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    Manufacturing at double the speed
    (Elsevier, 2015-11-02) Allwood, Julian M.; Childs, Tom H. C.; Clare, Adam T.; De Silva, Anjali K. M.; Dhokia, Vimal; Hutchings, Ian M.; Leach, Richard K.; Leal-Ayala, David R.; Lowth, Stewart; Majewski, Candice E.; Marzano, Adelaide; Mehnen, Jorn; Nassehi, Aydin; Ozturk, Erdem; Raffles, Mark H.; Roy, Rajkumar; Shyha, Islam; Turner, Sam
    The speed of manufacturing processes today depends on a trade-off between the physical processes of production, the wider system that allows these processes to operate and the co-ordination of a supply chain in the pursuit of meeting customer needs. Could the speed of this activity be doubled? This paper explores this hypothetical question, starting with examination of a diverse set of case studies spanning the activities of manufacturing. This reveals that the constraints on increasing manufacturing speed have some common themes, and several of these are examined in more detail, to identify absolute limits to performance. The physical processes of production are constrained by factors such as machine stiffness, actuator acceleration, heat transfer and the delivery of fluids, and for each of these, a simplified model is used to analyse the gap between current and limiting performance. The wider systems of production require the co-ordination of resources and push at the limits of human biophysical and cognitive limits. Evidence about these is explored and related to current practice. Out of this discussion, five promising innovations are explored to show examples of how manufacturing speed is increasing - with line arrays of point actuators, parallel tools, tailored application of precision, hybridisation and task taxonomies. The paper addresses a broad question which could be pursued by a wider community and in greater depth, but even this first examination suggests the possibility of unanticipated innovations in current manufacturing practices.
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    Realisation of multi-sensor framework for process monitoring of the wire arc additive manufacturing in producing Ti-6Al-4V parts
    (Taylor & Francis, 2018-04-30) Xu, Fangda; Dhokia, Vimal; Colegrove, Paul A.; McAndrew, Anthony; Williams, Stewart W.; Henstridge, Andrew; Newman, Stephen T.
    Wire arc additive manufacturing (WAAM) is arc welding-based additive manufacture which is providing a major opportunity for the aerospace industry to reduce buy-to-fly ratios from 20:1 with forging and machining to 5:1 with WAAM. The WAAM method can build a wide range of near net shapes from a variety of high-grade (metallic) materials at high deposition speeds without the need for costly moulds. However, current WAAM methods and technologies are unable to produce parts reliably and with consistent structural material properties and required dimensional accuracy. This is due to the complexity of the process and the lack of process control strategies. This article makes a brief review on monitoring methods that have been used in WAAM or similar processes. The authors then identify the requirements for a WAAM monitoring system based on the common attributes of the process. Finally, a novel multi-sensor framework is realised which monitors the system voltage/current, part profile and environmental oxygen level. The authors provide a new signal process technique to acquire accurate voltage and current signal without random noises thereby significantly improving the quality of WAAM manufacturing.