Design of powder aligning systems for the compression molding of radially anisotropic permanent magnet rings

The article describes the design of powder aligning fixtures for the compression molding of radially anisotropic NdFeB magnet rings. The implications of the high fields required are discussed, with particular reference to the limitations imposed on the aspect ratio of the magnets that can be satisfactorily aligned. Features for enhancing the magnitude of the aligning field in the mold cavity, e.g., a magnetic shunt to shield the inner core and tapering of the upper plate are discussed. These issues are illustrated by means of a design study on a powder aligning fixture for a NdFeB magnet ring with an outer diameter of 26 mm and a wall thickness of 3 mm. Extensive finite element analysis is employed to investigate the role of various features, and to optimize the geometry. The findings of the design study are validated by comparison with measurements on a prototype fixture. (C) 2002 American Institute of Physics.