Pure copper is an excellent thermal and electrical conductor, however, attempts to process it with additive manufacturing (AM) technologies have seen various levels of success. While electron beam melting (EBM) has successfully processed pure copper to high densities, laser powder bed fusion (LPBF) has had difficulties achieving the same results without the use of very high power lasers. This requirement has hampered the exploration of using LPBF with pure copper as most machines are equipped with lasers that have low to medium laser power densities. In this work, experiments were conducted to process pure copper with a 200W LPBF machine with a small laser spot diameter resulting in an above average laser power density in order to maximise density and achieve low electrical resistivity. The effects of initial build orientation and post heat treatment were also investigated to explore their influence on electrical resistivity. It was found that despite issues with high porosity, heat treated specimens had a lower electrical resistivity than other common AM materials such as the aluminium alloy AlSi10Mg. By conducting these tests, it was found that despite having approximately double the resistivity of commercially pure copper, the resistivity was sufficiently low enough to demonstrate the potential to use AM to process copper suitable for electrical applications.
Highlights• Medium powered LPBF machines can process pure Cu to an acceptable level.• Resistivity of as-built Cu increases by 33% depending on initial build orientation.• Resistivity can be reduced by over 50% from as-built conditions via heat treatment.• Electrical resistivity values once heat treated are lower than AlSi10Mg values.
Among the various technology enablers for modern electrical machines, additive manufacturing plays a key role. The advantage of having a precise control of the shape of ferromagnetic structures, whilst achieving good electromagnetic performance, fits well with the design requirements of rotating electrical machines. To a certain extent, some of the physical properties of the material can be "tuned", allowing for quick trade-off studies (i.e., prototyping), as opposed to conventional manufacturing techniques. Despite being considered an enabling technology, 3D printing of soft magnetic materials for electric motors is still at an embryonic stage. This work, thus, aims in providing an initial proof of concept. For the purpose, a switched reluctance machine is chosen as a case study. Its rotor core is additively manufactured through selective laser melting. Its performances are compared to those of an identical commercial motor featuring a laminated rotor core, via in-depth experimental tests. Initial results show that the 3D printed machine can actually develop the rated power, but with an efficiency reduction.
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