Bonded Magnet

Bonded magnet is a kind of composite material which composed of magnetic powder and binder. Bonded magnets are distinguished for complex shape, high dimensional precision, tight tolerance, no need for subsequent mechanical machining, integration capability with other functional parts, and suitable for mass production. Magnetic powder, volume fraction of binder and interior porosity plays a decisive role in the magnetic properties of the bonded magnet. Isotropic Neodymium magnet accounts for more than 80% of bonded rare earth magnet market, then other 20% are occupied by anisotropic Neodymium magnets, SmFeN magnets, and Samarium Cobalt magnets. Besides varies choices of magnetic powder, binder with different characters are also adding more diversity to the bonded magnets. The frequently-used binder includes thermosetting and thermoplastic material, thus correspond to compression molding, injection molding, extrusion molding, and calendering molding process. Bonded magnets with different binder also exhibits disparate magnetic properties, shape, and dimension adaptability.

Bonded Magnet

Characteristic Comparison of Different Molding Process

Parameter Unit Compression Molding Injection Molding Extrusion Molding Calendering Molding
Filling ratio vol% 70-85 50-70 60-80 50-70
Porosity vol% 5-8 2-5 3-6 6-10

(BH)max

(Neodymium magnet)

MGOe 2-13 2-8 10-11 6-8
Shape complexity middle very high high low
Temperature resistance of binder high very high (PPS) very high (PPS) low

Product Classifications of Bonded Magnet