Additive manufacturing of Fe-6.5Si cores with metal-insulator-metal structure via dual-nozzle material extrusion (MEX) technology

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This study proposes a novel approach for fabricating Fe-6.5 wt. %Si (Fe-6.5Si) soft magnetic cores using a dual-nozzle material extrusion (MEX) three-dimensional (3D) printing technology followed by a spark plasma sintering (SPS) process. A SiO2 insulator was printed between the Fe-6.5Si layers to fabricate metal–insulator-metal (MIM)-structured cores. Densified Fe-6.5Si soft magnetic cores (over 99%) were obtained owing to the resolution of the sintering problem with Fe-6.5Si because of its brittle nature using SPS. The magnetic core with a 0.2 mm-printed insulator (MC0.2) achieved a uniform insulator thickness of approximately 85 µm. Despite MC0.2 being approximately three times thicker than the single Fe-6.5Si layer (magnetic core single layer, MCS), a SiO2 insulator used in the cores of MC0.2 and MCS, resulted in comparable eddy current losses at 1 kHz. This highlighted the effectiveness of the MIM structure in suppressing the eddy currents. Thus, the proposed approach offers a promising solution for overcoming the geometric limitations of traditional stamping processes and paves the way for advanced magnetic core applications in additive manufacturing.