Ceramic or Ferrite Magnets are produced by calcining a mixture of iron oxide and strontium carbonate to form a metallic oxide. A multiple stage milling operation reduces the calcined material to a small particle size. The powder is then compacted in a die by one of two methods. In the first method, the powder is compacted dry which develops an isotropic magnet with weaker magnetic properties, but with better dimensional tolerances. Often, a dry pressed magnet does not require finish grinding. In the second method, the powder is mixed with water to form slurry. The slurry is compacted in a die in the presence of a magnetic field. The applied field creates an anisotropic magnet which exhibits superior magnetic properties, but usually requires finish grinding.
The compacted parts which approximate the finished geometry are then sintered at high temperatures to achieve the final fusion of the individual particles. Final shaping is achieved by diamond abrasives. Usually the pole faces of the ceramic (ferrite) magnets will be ground and the remaining surfaces will exhibit “as sintered” tolerances and physical characteristics.