Improvement of the magnetic properties of injection molded polymer bonded magnets

Polymer bonded, injection molded magnets show great potential in their application in electric drives. Compared to conventional sintered magnets, the advantages of injection molded polymer bonded magnets are the freedom of design to produce complex shapes and complex magnetizing structures, as well as the option of integrating other functional parts such as shafts, bushings or gears directly in one processing step during injection molding. However, in comparison to conventional sintered magnets, polymer bonded magnets have lower magnetic properties due to the content of the polymer matrix. In order to improve the properties of polymer bonded magnets generally the filler content and the orientation degree of the particles must be increased. However, the magnetic properties of polymer bonded magnets depend on many factors with complex interactions such as the filler content, the orientability of the filler particles, the properties of the magnetic filler itself, processing parameters and the magnetic field inside of the cavity. The magnetic field in the cavity can be improved by guiding the magnetic flux in an optimal way by using tool materials with defined magnetic properties. This paper deals with the improvement of the magnetic properties of polymer bonded magnets. Thereby, the improvement of the tool design and thus, the characterization of the magnetic properties of different tool materials are of particular importance.