SLS Prints Programmable Bonded Magnets

Key Takeaways

• Field‑assisted SLS aligns magnetic particles locally during sintering.
• Programmable electromagnets create heterogeneous magnet zones in one print.
• Printed NdFeB/FeCo samples achieved up to 14 mT remanence.
• Potential to replace post‑assembly magnetic laminations in devices.
• Scalability challenges include powder handling, throughput, and field control.

Summary

Researchers at Auckland University of Technology have demonstrated a field‑assisted selective laser sintering (SLS) process that prints polymer‑bonded magnets with locally programmable pole patterns. By integrating under‑bed electromagnets and a powder‑handling bar, they can deposit different magnetic powders point‑wise and align them with timed magnetic fields during each layer’s sintering. Proof‑of‑concept parts showed distinct remanent fluxes, especially in NdFeB/FeCo composites, after post‑print magnetization. The approach promises to embed complex magnetic field shapes directly into a single printed component, potentially eliminating traditional assembly steps.

Pulse Analysis

The convergence of additive manufacturing and magnetic materials has long been hampered by the difficulty of orienting anisotropic particles within a solidifying polymer matrix. Traditional methods such as fused filament fabrication or stereolithography rely on global magnetic fields, yielding uniform anisotropy but lacking spatial control. The Auckland University of Technology team sidesteps this limitation by synchronizing localized electromagnetic fields with the SLS laser’s point‑wise sintering, effectively writing magnetic vectors layer by layer. This technique builds on earlier field‑assisted resin printing, yet it uniquely overcomes the viscous drag and rapid solidification that previously prevented fine‑grained alignment in powder‑based processes.

In their experimental rig, a CO₂ laser sinters nylon powder while a custom powder‑handling bar vacuums and redeposits magnetic powders into pre‑programmed recesses. Under‑bed electromagnets generate up to 230 mT fields whose polarity can be switched in real time, aligning NdFeB, FeSi or FeCo particles as each slice is formed. The resulting thin‑film samples exhibited modest intrinsic remanence (1.5‑2 mT) that amplified to 14 mT northward flux after post‑print magnetization for NdFeB/FeCo configurations. Spatially confined magnetic islands demonstrated differential responses of 80‑100 mT, confirming that the process can produce dipole and multipole patterns without any post‑processing steps.

From a commercial perspective, the ability to print magnets that already possess the desired field geometry could transform electromechanical design. Motor manufacturers could integrate field‑shaping inserts directly into housings, sensor developers might embed hard‑soft magnetic domains for on‑chip flux control, and robotics firms could fine‑tune force vectors without assembling laminated stacks. However, adoption hinges on scaling the under‑bed electromagnet array, improving powder‑loading fractions, and automating the suction‑dispense choreography for larger build volumes. Should these engineering hurdles be resolved, programmable magnetic SLS could become a flagship service for additive‑manufacturing firms seeking to offer low‑volume, high‑complexity magnetic components.