Bonded magnets, also called compression bonded magnets, are an excellent choice over other magnet types. They are suitable for the application which request high magnetic field strength, general mechanical strength, and simple compression shape. Bonded magnets are manufactured by molding compression of the compound alloy powder (Neodymium or SmCo) with resin. The resin is further processed to form magnets and resistant to normal industrial solvent and automotive fluids. Since no magnetic field is applied during the compression, the finished product can be magnetized in any direction. The normal application temperatures range from below -40°C to above 165°C.
Injection magnets, also called injection molded magnets, are produced by an injection process of pre-mixed magnetic powder or mixed other composite material. Magnetic powders include Ferrite, Neodymium, and SmCo. Binder types include Nylon 6 and 12, PPS, and Polyamide, which produces an accurate and homogeneous magnetic part. Through this process magnets can be directly molded into various shapes (thin-wall ring, rods, slice, holes and pins, etc.) or over the components (shafts, cams, inserts and the like eliminating some steps) in assembly, with extremely tight tolerances and a broad range of magnetic properties and characteristics. Injection Molded magnets have good corrosion resistance in water and industrial solvents. The binders and magnetic alloys are capable of a wide range of application temperatures from below -40°C to above 180°C.
Bonded magnets can offer higher magnetic strength than injection magnets due to their higher magnetic particle density, but are limited to simpler geometries.
Neodymium magnets can be magnetized in any direction as long as it is aligned properly. In some instances multiple pole magnetizations is not possible; when it is possible, special fixtures are required.
The bonded and injection magnets are wildly used in spindle motor, step motor, synchronous motor, DC motor, brushless DC motor and sensor in automotive industry.