Additive Manufacturing of Next Generation Electrical Machine Windings - Opportunities in Fusion Engineering?

More electric propulsion across automotive and aerospace has lead to a demand for significant improvement in thepower density of electrical machines. This has, in turn, triggered research into advanced manufacturing methods for higher performance magnet systems in machines. The application of Laser Powder Bed Fusion (LPBF), a form of Additive Manufacture (AM), to the current carrying coils of the electromagnetic circuit of a machine has allowed several significant improvements to the design of these parts. One benefit which can be realised in this way is the tailoring of conductor form to the operating field and the alteration of conductor topolgy to reduce AC loss. Another advantage of these manufacturing techniques is the ability to introduce methods of direct cooling to the coil, including highly efficient heat exchangers derived from generative design techniques. It is significant that the electrical conductivity achieved is now equivalent to that of conventional drawn Cu wire. This paper hypothesises that the lessons learned in developing production methods for next generation, high performance components for electric machines might also find utility in the very demanding electromagnetic circuits found in magnetic confinement fusion. Potential benefits for the production of Cable-in-Conduit Conductor (CICC) superconducting (SC) bus-bar joints, or even larger elements of conductors are discussed. This is used to motivate future experimental studies of the mechanical and electrical performance of AM Cu at cryogenic temperatures as well as the further development of the manufacturing state of the art

Improving the feel of 3D printed prototypes for new product development: A feasibility study of emulating mass properties by optimising infill structures and materials

Product prototypes and particularly those that are 3D printed will have mass properties that are significantly different from the product they represent. This affects both functional performance and stakeholder perception of the prototype. Within this work, computational emulation of mass properties for a primitive object (a cube) is considered, developing a baseline numerical method and parameter set with the aim of demonstrating the means of improving feel in 3D printed prototypes. The method is then applied and tuned for three case study products – a games controller, a hand drill and a laser pointer – demonstrating that product mass properties could be numerically emulated to within ~1% of the target values. This was achieved using typical material extrusion technology with no physical or process modification. It was observed that emulation accuracy is dependent on the relative offset of the centre of mass from the geometric centre. A sensitivity analysis is further undertaken to demonstrate that product-specific parameters can be beneficial. With tuning of these values, and with some neglect of practical limitations, emulation accuracy as high as ~99.8% can be achieved. This was shown to be a reduction in error of up to 99.6% relative to a conventional fabrication

Direct thermal management of windings enabled by additive manufacturing

This is an accepted manuscript of an article published by IEEE in IEEE Transactions on Industry Applications on 27/09/2022, available online: https://doi.org/10.1109/TIA.2022.3209171 The accepted version of the publication may differ from the final published version.The electrification and hybridization of ground- and air-transport, in pursuit of Carbon Net Zero targets, is driving demand for high power-density electrical machines. The power-density and reliability of electrical machines is ultimately limited by their ability to dissipate internally generated losses within the temperature constraints of the electrical insulation system. As the electrical windings are typically the dominant source of loss, their enhanced design is in the critical path to improvements in power-density. Application of metal additive manufacturing has the potential to disrupt conventional winding design by removing restrictions on conductor profiles, topologies and embedded thermal management. In this paper, a modular end-winding heat exchanger concept is presented, which enables effective direct cooling without occupying valuable stator slot cross-section. In addition, this arrangement eliminates the need for a good stator-winding thermal interface, thereby allowing mechanical or other less permanent winding retention methods to be used, facilitating non-destructive disassembly and repair. A prototype winding is fabricated and experimentally tested to demonstrate the feasibility of the concept, yielding promising results.This work has been funded by EPSRC Grant Number EP/f02125X/1 and EP/S018034/1 as part of a Future Electrical Machines Manufacturing (FEMM) Hub feasibility study.Published versio

Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds

This paper reports a novel, negligible-cost and open-source process for the rapid prototyping of complex microfluidic devices in polydimethylsiloxane (PDMS) using 3D-printed interconnecting microchannel scaffolds. These single-extrusion scaffolds are designed with interconnecting ends and used to quickly configure complex microfluidic systems before being embedded in PDMS to produce an imprint of the microfluidic configuration. The scaffolds are printed using common Material Extrusion (MEX) 3D printers and the limits, cost & reliability of the process are evaluated. The limits of standard MEX 3D-printing with off-the-shelf printer modifications is shown to achieve a minimum channel cross-section of 100×100 μm. The paper also lays out a protocol for the rapid fabrication of low-cost microfluidic channel moulds from the thermoplastic 3D-printed scaffolds, allowing the manufacture of customisable microfluidic systems without specialist equipment. The morphology of the resulting PDMS microchannels fabricated with the method are characterised and, when applied directly to glass, without plasma surface treatment, are shown to efficiently operate within the typical working pressures of commercial microfluidic devices. The technique is further validated through the demonstration of 2 common microfluidic devices; a fluid-mixer demonstrating the effective interconnecting scaffold design, and a microsphere droplet generator. The minimal cost of manufacture means that a 5000-piece physical library of mix-and-match channel scaffolds (100 μm scale) can be printed for ~$0.50 and made available to researchers and educators who lack access to appropriate technology. This simple yet innovative approach dramatically lowers the threshold for research and education into microfluidics and will make possible the rapid prototyping of point-of-care lab-on-a-chip diagnostic technology that is truly affordable the world over