ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 1 7 Demand for electric motors has increased rapidly alongside society’s clean electrification efforts in response to climate change and decarbonization challenges. Innovative technologies such as additive manufacturing (AM) are considered potential options for the realization of more efficient, lighter, and highly customized electric motors due to the design freedom they enable over conventional methods. Making AM a viable method to economically produce electric motors is tied to the potential advantages it offers, i.e., the ability to realize new topologies, novel thermal management solutions, weight reduction, and more efficient use of materials[1]. A significant change in electrical machine design philosophy has not occurred for decades, with the traditional approach involving construction of magnetic cores by stacking thin, insulated electrical steel sheets to create a 2D magnetic circuit. By contrast, AM allows construction of 3D topologies, which has led to a growing interest in development of 3D flux machines[2]. AM technologies are advancing rapidly, as are computational methods and materials development, all of which are required to make the production of high-efficiency AM electric motors a reality from both the technological and economic perspectives. This article describes some key developments and challenges related to additively manufactured electric motors in terms of manufacturing, materials development, and design. MANUFACTURING, MATERIALS, AND MOTOR DESIGN Additive Manufacturing: AM tech- nologies offer a notable advantage over traditional manufacturing methods, namely the ability to construct complex geometries with minimal tooling and the enhanced viability of highly customizable small-scale production. Use of AM could lead to optimized electromagnetic, thermal, and mechanical features and the emergence of previously unfeasible topologies such as transverse flux machines with 3D flux patterns. Currently, the most mature and widely adopted AM technology is laser-based powder bed fusion (PBF-LB), which is also capable of producing high- quality ferromagnetic cores[2]. One of the main technical limitations of commercial PBF-LB machines is that they are intend- ed for manufacturing a single material at a time. This makes incorporation of elec- trical insulating material a major challenge, which is important for loss mitigation. Development of multi-material AM is therefore seen as an important step toward production of low-loss electrical components[3]. Materials: Different types of materials are required for manufacturing electric motors, e.g., soft magnetic, hard magnetic, structural, and insulating materials. The properties of AM structural materials (e.g., steels and aluminum alloys) and soft magnetic materials (e.g., Fe-Si and Fe-Co alloys) now have magnetic properties comparable to traditionally manufactured bulk materials[4,5]. However, additively manufactured hard magnetic materials such as Nd-Fe-B do not yet possess the required material properties for high-performance applications, although development is rapidly progressing (Fig. 1)[6]. Today, PBF processed Nd-Fe-B alloys have low ADDITIVE MANUFACTURING OF ELECTRIC MOTORS The manufacture of electric motors using additive methods offers potential advantages of increased efficiency, weight reduction, and customizability over traditional processes. Tuomas Riipinen, Jenni Pippuri-Mäkeläinen, and Aino Manninen VTT Technical Research Centre of Finland Fig. 1 – Development of hard magnetic materials over the decades, including AM Nd-Fe-B alloys. Adapted from Ref. 8.
RkJQdWJsaXNoZXIy MTYyMzk3NQ==