Abstract – Additive manufacturing, commonly known as 3D printing, is an emerging technology that is gaining considerable research interest in recent years. In particular, metal printing methodologies might be successfully employed in developing lightweight and complex geometry components for electrical machines. In this paper, a soft magnetic material with a high content of silicon (i.e. ≈5%w.t.) has been characterized and its properties have been determined. The obtained material has been then used for 3D printing a salient, 8 pole rotor through selective laser melting. Finally, the manufactured rotor has been placed inside the laminated stator of a switched reluctance machine and its performance has been assessed comprehensive experimental tests. The collected results confirmed the viability of additive manufacturing technology in the electrical machine field. Index Terms—Additive Manufacturing, 3D Printing, SLM, Electrification, Electrical Machines, Switched Reluctance I. INTRODUCTION Future electrification roadmaps [1, 2], leading to the progressive de-carbonization of transportation platforms, can only be met through the introduction and exploration of game- changing technologies and unconventional design methodologies [3] for drive-train components [4, 5]. The Electrical Machine (EM) represents the key element in both hybrid / electric road vehicles as well as aircraft [6]. Whilst recent innovations in terms of materials optimization [7] and sizing tools have brought to considerable advancements in terms of efficiency, there is still a long way to go for meeting challenging power density targets [8, 9]. The potential for improvement lies on each and every component within a machine, although it is perceived that key enablers will be the clear understanding of aging phenomenology in insulating materials and systems [10-13] and the efficient utilization of advanced manufacturing techniques [14, 15]. In conventional manufacturing, a component is built by a material removing process, which is contrary to Additive Manufacturing (AM) technologies, where a data Computer Aided Design (CAD) is utilized to precisely create geometric structures via layer-by-layer material deposition. AM allows the development of net-shape parts and components featuring complex geometrical features at no extra cost, minimizing the wasted material. The only limits are represented by the resolution of the 3D printing process and the maximum build volume, which is directly related with the printer size. AM through non-metallic materials (e.g. plastics) is nowadays a well-assessed technique in various branches of engineering. As opposed to traditional manufacturing methods, AM enables the rapid prototyping of newly- designed elements, thus shortening the overall development time-frame of new products. This because the use of pressing / stamping dies, cutting tools, etc., for manufacturing new components is not a requirement in AM processes. In recent years, AM is progressively gaining popularity within the EM community. Various examples, where AM is employed for the construction of both active and non-active parts for EMs, have been reported in specialized literature [16-22]. A comprehensive and detailed review on the topic is represented by [23]. For what concerns AM of metallic elements, a technique known as Selective Laser Melting (SLM) has the potential to be employed for EM’s magnetic parts manufacturing [24, 25]. Whilst SLM-manufactured parts are relatively mature from the structural point of view, new growing research is recently focusing on the optimization of magnetic properties, so that the potential of this technique can be fully exploited in EM design [16, 24]. This work represents a comprehensive study, where a rotor for a Switched Reluctance Machine (SRM) is 3D printed through SLM and fully tested. The presented analysis covers both the physical characterization of the additively- manufactured material, as well as the actual manufacturing of the rotor. The electro-mechanical performance of the SRM employing the 3D printed rotor is then experimentally verified, and the complete torque-speed envelope of the machine is extracted. II. SLM OF SOFT MAGNETIC MATERIAL The stator and rotor cores of industrial EMs are typically manufactured by axially stacking thin sheets (generally < 0.5 mm thickness) of soft silicon-steel alloys (Fe-Si). The silicon content within the alloy has a direct influence on the machine’s efficiency, as its addition helps in cutting down eddy current losses, by directly acting on the lamination’s L. Gargalis 1 , V. Madonna 2* , P. Giangrande 2 , R. Rocca 3 , I. Ashcroft 1 , R. Hague 1 and M. Galea 2,4 1 Centre for Additive Manufacturing (CfAM), University of Nottingham, UK 2 Power Electronics, Machines and Control (PEMC) Group, University of Nottingham, UK 3 Department of Engineering, Universitá degli Studi di Roma La Sapienza, Italy 4 Key Laboratory of More Electric Aircraft Technology of Zhejiang Province, University of Nottingham Ningbo, China *Email: Vincenzo.Madonna1@nottingham.ac.uk _____________________________________ This work was partially funded from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 807081 and no. 821023. This work was also partially funded by the University of Nottingham Propulsion Futures Beacon. (Corresponding Author: Vincenzo Madonna) V. Madonna, P. Giangrande and M. Galea are with the Power Electronics, Machines and Control Research Group (PEMC), University of Nottingham, UK. (email: Vincenzo.madonna1@nottingham.ac.uk) M. Galea is also with the Key Laboratory of More Electric Aircraft Technology of Zhejiang Province, Ningbo 315100, China. Development and Testing of Soft Magnetic Rotor for a Switched Reluctance Motor Built Through Additive Manufacturing Technology