Neodymium Loaf Magnet
Neodymium loaf magnet, loaf Neodymium magnet or Neodymium bread magnet is a loaf shape like a block mass with a rounded top. It is mainly inserted to the slot on the shaft or the flat surface of the loaf magnet glued on the shaft to work as an electric motor rotor.
Considering the precision size of the rounded top including radius, width and length, the Neodymium loaf magnet is limited to a specific application rather than a versatile usage. Therefore it is mainly customized for the industrial application.
How is the sintered Neodymium loaf magnet produced? Almost all sizes of loaf or bread Neodymium magnets are magnetized in pair through the thickness. Same as all shapes of sintered Neodymium magnets, firstly the raw materials including rare earth metals are measured to produce the suitable composition. The materials are melted under vacuum or inert gas in an induction melting furnace. The molten alloy is either poured into a mold, onto a chill plate, or processed in a strip cast furnace that can form a thin, continuous metal strip. These metal alloys or strips are crushed and pulverized to form a fine powder whose particle size is specified to contain material with one magnetic preferred orientation. The powder is placed in a jig and a magnetic field is applied while the power is pressed into a rectangle shape. In this mechanical pressing, the magnetic anisotropy is achieved. The pressed parts are heated to a sintering temperature and allowed to densify in a vacuum sintering furnace. Aging the magnets after sintering adjusts the properties of magnets.
Basic magnetic properties of loaf Neodymium magnets are set after the sintering & aging process is completed. Key data including Br, Hcb, Hcj, (BH)max, HK, should be tested and recorded. Only those magnets that pass the test can go to subsequent processes including machining.
Normally we cut the large magnet blocks to many pieces of block shaped magnets with thickness a little bigger than the final loaf magnet. And then we use profile grinding to machine the required radius size. This option of cut and grinding ensure the size accuracy of the Neodymium loaf magnet, particularly for the radius size.