Electric Motor Cores from Additive Manufacturing

The Challenge

Fe-6.5%Si electrical steel offers optimal soft magnetic properties for electric machine cores, higher resistivity and zero magnetostriction compared to conventional 3% silicon grades. However, the brittleness of high-silicon alloys makes them impossible to process by conventional rolling and stamping methods. Meanwhile, the electric vehicle revolution demands complex, high-performance motor designs that conventional laminated steel construction cannot efficiently produce. Alternative fabrication methods are needed to unlock this superior magnetic material.

The Solution

This research developed a complete filament-based material extrusion (MEX) process for manufacturing monolithic Fe-6.5%Si parts. A tailored filament incorporating high-silicon steel powder was specifically developed to enable extrusion-based processing of this composition, followed by pressureless sintering to achieve full density.

Impulse excitation testing characterized the mechanical properties of sintered parts, measuring elastic modulus to verify densification quality and correlate processing parameters with structural integrity. Four-point bending tests confirmed flexural strength of 855 ± 96 MPa, while IET provided the non-destructive screening needed to evaluate multiple processing variations efficiently.

Key takeaway: MEX-produced Fe-6.5%Si stacked thin rings achieved lower core losses than NO20 commercial laminations at 100 Hz. This is the first time AM has outperformed standard electrical steel laminations.

Results

Sintered parts achieved 96–99% relative density with remarkable magnetic performance. Stacked thin rings exhibited lower core losses than NO20 commercial laminations at 100 Hz, the first time standard laminations have been outperformed by additively manufactured high-silicon steel. The team demonstrated versatility by fabricating two complete stator core designs, validating the technology’s readiness for complex electric motor applications.