The shapes of Nd - Fe - B permanent magnets used in practical applications are diverse, such as discs, cylinders, cylinders with inner holes; square sheets, cubes, square columns; tiles, sectors, trapezoids, polygons and various irregular shapes. Each shape of permanent magnet has different dimensions, and it's very difficult to achieve one - step molding in the production process. The general production process is as follows: First, produce large - sized (big - dimension) blanks. After sintering and tempering, mechanical processing (including cutting and drilling), grinding, and surface plating (coating) are carried out. Then, the magnetic properties, surface quality, and dimensional accuracy of the magnets are tested. After that, the magnets are magnetized, packaged, and shipped out.
Mechanical processing is divided into three categories:
(1) Drilling processing: Cylindrical and square - bar - shaped magnets are processed into cylindrical or square - tubular magnets. The processing methods include grinding - slicing processing, electric - discharge - cutting processing, and laser processing.
(2) Cutting processing: Cylindrical and square - column - shaped magnets are cut into disc - shaped and square - sheet - shaped ones.
(3) Profile processing: Circular and square - shaped magnets are processed into sectors, tiles, or magnets with grooves or other complex shapes.
The surface of sintered Nd - Fe - B permanent - magnet components generally requires smoothness and a certain accuracy. The surface of magnets delivered as blanks needs to be ground. The commonly - used grinding methods for square Nd - Fe - B permanent - magnet alloys include surface grinding, double - end - face grinding, internal - circular grinding, and external - circular grinding. Cylinders usually use centerless grinding and double - end - face grinding. Tiles, sectors, and VCM magnets use multi - station grinding machines.
For a qualified magnet, not only the performance needs to meet the standards, but also the control of dimensional tolerance directly affects its application. The guarantee of dimensions directly depends on the factory's processing capability. Processing equipment is constantly updated with the economy and market demands. More efficient equipment and the trend of industrial automation not only meet customers' increasing demands for product accuracy, but also save manpower and costs, making products more competitive in the market.
