Additive manufacturing of polymer bonded magnets is a recently developed technique, for single unit production, and for structures that have been impossible to manufacture previously.
Also new possibilities to create a specific stray field around the magnet are triggered. The recently published work by scientists at the Institute of Solid State Physics at Vienna University of Technology, the Christian Doppler Laboratory for Advanced Magnetic Sensing and Materials and the Department of Polymer Engineering and Science at Montanuniversitaet Leoben (Austria), presents a method to 3D print polymer bonded magnets with a variable magnetic compound density distribution.
A low-cost, end-user filament extrusion 3D printer with a mixing extruder is used to mix permanent magnetic filaments with pure PA12 filaments. The magnetic filaments are compounded, extruded, and characterized for the printing process. To deduce the quality of the manufactured magnets with a variable compound density, an inverse stray field framework was used.
Rare earth (NdFeB) magnets are mainly divided into sintered and polymer bonded magnets. On the one hand, sintered magnets have the highest maximum energy product (BH)max, on the other hand polymer bonded magnets enable the manufacturing of complex shapes and magnetization structures, but with a lower (BH)max .
Bonded magnets offer a wide application range from sensor to actuator applications. Polymer bonded magnets are composites with permanent-magnet powder embedded in a polymer binder matrix. Hard magnetic particles, ferrite (e.g. Sr, Ba), and rare-earth materials (e.g. NdFeB) with a volume filler content between 40 – 65 vol.% are inserted
The research shows the effectiveness of the printing process and the simulation method. It can also be used to manufacture magnets that produce a predefined stray field in a given region. Examples for sensor applications are presented in the paper. This setup and simulation framework allows the design and manufacturing of polymer bonded permanent magnets which are impossible to create with conventional methods.