Net Shape 3D Printed NdFeB Permanent Magnet

Direct metal 3D printing by Selective Laser Melting (SLM) was used to realize NdFeB magnets of different shapes. The results were compared to the magnetic properties of magnets prepared by two known alternative methods, injection molding and spark plasma sintering (SPS). A commercial metal 3D Printer was used to produce three dimensional magnetic samples. Before the printing process starts, a design of the object was created in a CAD software and sliced in layers. SPS was performed using a commercial setup. Magnetic measurements were done with a Pulsed Field Magnetometer (PFM). X-ray diffraction (XRD) was used to characterize the crystal structure of the material. The measurements werecarried out on polished surfaces of polymer embedded crushed powders. Fine-tuning of the laser parameters like laser speed, focus, and power, together with the control of the thickness of the deposited powder layer, allowed rapid production of dense net shape hard magnets with grain sizes of 1 μm, properties not easily achievable with standard manufacturing processes. Interestingly, no post heat treatment was found to be necessary to reach the final magnetic properties in this Dy-free NdFeB alloy. The magnetic characteristics of the printed samples was very good with room temperature values of coercivity identical to polymer bonded composites based on the same starting powder.