Soft and hard magnetic materials were fabricated using additive manufacturing (AM) for use in 3D electrical machines. The effect of the characteristics and the nature of the magnetic feedstock powders was evaluated for both the cold spray (CS) and the fused filament fabrication (FFF) processes. 3D finite element analysis (FEA) was used to develop new motor topologies based on the advantages offered by AM. FEA optimization also allowed the identification of the most critical material properties and is thus a powerful tool to facilitate material development.

Introduction

Additive manufacturing (AM) of metal parts was successfully used in various applications for the fabrication of complex shape mechanical parts. As AM techniques and processes are maturing, a new focus in research and development is devoted to functional materials where various physical properties of the materials need to be optimized for their utilization. Magnetic materials are one type of functional materials that has generated interest lately in the AM community. In the last five years research and development efforts for the development of conventional magnets has been steadily increasing. The main motivation for this work is the potential benefits arising from the agility of AM processes both for the prototyping stage and for the realization of complex designs. Ultimately additive manufacturing could offer significant advantages for the low volume production of customized parts while increasing the design flexibility for magnetic components in electrical machines [1].

In most electrical machines applications, hard magnetic materials are used in combination with soft magnetic materials. When compared to AM of mechanical components AM of magnetic materials presents additional difficulties and challenges. One of the most important challenges is probably that the high energy used tends to negatively affect the physical properties of the materials. For NdFeB oxidation and phase transformation can adversely affect the performance of the magnet [2], [3]. In the case of soft magnetic materials, the difficulty to incorporate insulation between powder particles in an AM process limits their utilization when low eddy-current losses are required [4]. In order to address these shortcomings the research presented in this paper was focused on low-energy solid-state AM processes that can offer the flexibility and design advantages of AM without modifying the functional properties of the soft and hard magnetic materials.

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