## 4 Future Work  
Selective laser melting (SLM) technology is currently unsuitable for eddy current reduction via laminated structure due to complications in printing multiple materials in parallel with different thermal behavior and due the powder bed-based nature of the process, enabling the usage of a single powder concurrently. Recent breakthroughs in powder deposition, enabling the selective powder deposition of multiple materials [38], suggests that in the near future, multi-material SLM printing of electromechanical components might be available. Presently, it can be suggested that eddy current losses can be reduced in printed components by geometrical manipulation: printing of materials with refined internal structures. The evolution of material can be accomplished by introducing air gaps to the material perpendicular to the flux direction or printing the material as a dense lattice structure. For the verification of eddy current reduction with geometrical manipulation, FEM analysis was performed on a slotted toroidal part with cross-section geometry as shown in Figure 11 alongside the FEM simulated current density J in the toroidal cross-section. The proposed geometry in the current study was chosen arbitrarily to illustrate the effectiveness of printed air gaps in the magnetic material for eddy current reduction and will require further optimization.  
Eddy current losses were again calculated from the obtained hysteresis curves, presented in Figure 12. The eddy current loss decreased from 75.3 to 10.9 W/kg (decrease of 85%) when calculating the hysteresis loops according to the true area of the slotted cross section. When taking into account, however, the full area occupied by the geometry (solid area), the average magnetic flux density across the cross-section also reduces from 1.5 to 1.2 T, suggesting a tradeoff between eddy current loss reduction through geometry manipulation and maximum flux density obtained in the soft ferromagnetic part. The air content and the filling factor of the magnetic material in the manipulated part would then dependent on the spatial manufacturing accuracy of the printing system in question. Optimally, the cross-sectional area should be as dense as possible for achieving high saturation magnetization and as partitioned as realizable for limiting the induced eddy currents while retaining the mechanical strength required by its application. Presently, state-of-the-art slotted geometry with an average relative density of 56.5% with Hilbert curve structure has been used in [13] for obtaining near fully decayed eddy currents in printed material. Lattice structures have been shown to exhibit excellent strength to weight mechanical properties for different alloys [39; 40], however have not undergone experimental or FEM magnetic property analysis in the literature. Additionally, lattice structures show even more reduced filling factor in the range of 30-40% [41].  
Figure 11: (**a**) Modeled toroid geometry, (**b**) Simulated induced current density in the toroid cross section at time moment field zero-crossing (H = 0).  
Figure 12: Hysteresis curve comparison between the modelled solid material, slotted model calculated with true area and slotted model calculated with the solid cross-sectional area.