Φ Abstract – Additive manufacturing (AM) has been undergoing dynamic development in recent years. The latest evolution of AM has been recognised as a key enabling technology in a wide range of applications, some of which include medical, aerospace and automotive industries. The use of AM opens new avenues for design solutions, otherwise challenging or impossible to realise when using more conventional techniques for manufacture. No- or low-material waste and high-flexibility are some of the attributes of modern AM. This paper aims to provide an overview of the existing examples of employing AM in construction of electrical machines. The paper reviews research and development work related to all integral components of an electrical machine assembly. These include active parts like coils/windings, electrical insulation, stator/rotor magnetic core packs, permanent magnets (PMs). The machine structural/mechanical and thermal management components are also discussed in the paper. Further to these, the authors make some comments/forecasts on how the AM could improve performance and manufacturability of the future electrical machines. Index Terms—Additive manufacturing (AM), manufacturing techniques, electrical machines, machine assembly. I. INTRODUCTION UNDAMENTALS of design and fabrication of electrical machines are governed by well understood processes, which were established over decades of developments. All progress related to modern day electrical machines has been driven by two fundamental factors: demand for ‘more electric’ technologies and subsequent research-developments. It is important to note that both factors are non-exclusive in setting the new development trends, either as a results of socio- economic landscape or ‘blue-sky’ research. The research element is particularly interesting in the context of this paper. More specifically, developments of new designing methods, materials and manufacturing techniques, which had a profound impact on the evolution of electrical machines. Some of the examples denoting step changes in electrical machine technology include: advances in high-fidelity design techniques, e.g. modern computational electromagnetics, introduction of new materials like high-energy rare-earth permanent magnets (PMs) and evolution of manufacturing methods for high-volume applications. All the above mentioned examples are the building blocks of the modern ‘design for application’ of electrical machines. AM has been successfully employed in a large variety of applications, which is evidenced by a plethora of press announcements and researcher publications [1]-[45]. The Rafal Wrobel and Barrie Mecrow are with Newcastle University, School of Engineering, Merz Court, Newcastle upon Tyne, NE1 7UR, UK (e-mails: rafal.wrobel@newcastle.ac.uk and barrie.mecrow@newcastle.ac.uk). ability to create virtually unconstrained, three-dimensional (3D), no-waste, rapid-prototyping of parts and components is very attractive. The use of wide range of materials: plastics, ceramics, metal alloys and even organic-/bio-materials (bio- ink) places AM at the forefront of modern techniques for manufacture. Further to these, ability to scale up manufacture from a single prototype to high-volume, adds to the list of benefits of employing AM. An example here are large aerospace companies, which announced the use of AM for in- volume production [1], [2]. In this paper, the focus is placed on electrical machines, where materials like plastics, ceramics and metal alloys are of particular interest. The key electrical machine sub-assemblies fabricated using AM are discussed in consecutive sections of the paper. The examples include: coils/windings, elements of electrical insulation, stator/rotor magnetic core packs, PMs, motor housing/structural parts and elements for machine thermal management. The authors are aware of numerous activities related to AM of electrical machines worldwide, both on the commercial and academic side. The material gathered in this paper is limited to commercially insensitive, most of which is readily available, with appropriate references provided. As the level of technology maturity varies among the selected examples, the authors provide supplementary commentary to help navigate the large volume of information. II. AM TECHNIQUES The term ‘AM’, or the less precise synonymous ‘3D printing’, is rather broad and encompasses a wide range of techniques. The common factor for all the techniques is that a manufactured part is made by layering of material/materials based on a digital model representation. The American Society for Testing and Standards (ASTM) formulated a set of standards categorising AM techniques by the specific manufacturing processes used. There are 7 types of AM [3]: - vat photopolymerisation, - material jetting, - binder jetting, - material extrusion, - powder bed fusion, - sheet lamination, - direct energy deposition. Further to the above classification various other works on standardisation and roadmapping for AM have been ongoing [4], [5]. Powder bed fusion is the most relevant in the context of AM of electrical machines. Additive Manufacturing in Construction of Electrical Machines – A Review Rafal Wrobel and Barrie Mecrow F