Gradient bonded Nd-Fe-B magnets
Waldemar Kaszuwara, Bartosz Michalski, Marcin Leonowicz, Maciej Bodnicki, Łukasz Ciupiński, Jakub Jaroszewicz
Quarterly No. 3, 2013 pages 174-178
DOI:
keywords: graded materials, Nd-Fe-B permanent magnets, bonded magnets
abstract The concept of fabricating disc magnets for application in stepper motors has been presented. The disc magnets are composed of two elements, magnetized in the opposite direction, having a gradient structure. Such a structure produces a effect similar to the one in multi-pole magnetizing, which is difficult to implement, especially for small size magnets. The magnets were processed using Nd-Fe-B powder bonded by an epoxy resin. As a novelty in this concept, one can regard the application of centrifugal casting, directing the magnetic particles to the region of the active part of the magnet i.e. the part interacting with the magnetic core. In the applied solution, an elongated part having axial symmetry and a cross-section equal to that of the thus designed magnet. It was shown that by the application of resin of a carefully chosen viscosity, one can obtain various distributions of powder particles along the radius of the magnet. A more favorable structure of the composite magnet for this particular application was achieved using low viscosity resin, which enabled movement of the entire powder towards the active part and provided a 43% filling ratio. The studies showed that the flake-shaped powder used in the experiment, shows a tendency to form a morphological texture, i.e. the flakes tend to locate themselves perpendicular to the radius of the cast magnet. This method of fabricating disc magnets for stepper motors provides substantial savings, resulting from using a smaller proportion of Nd-Fe-B powder while maintaining a high filling ratio in the active part of the magnet.