Bonded Ferrite is either injection or compression molded, and typically uses Nylon 6 or Nylon 12 when injection molded. Compression molded (which is very rare) is made by using epoxy mixed into the ferrite. Typically most bonded ferrite uses strontium ferrite. It costs slightly more than sintered ferrite because ferrite must be powderized and mixed with the appropriate material for carrying of the ferrite. The ferrite can be aligned in the mold which saves a secondary step. Note: bonded ferrite can also be calendared in sheets, rolls, & strips. Calendared material either uses CPE or Butyl Nitride. Additives: See Rubber Bonded Ferrite. Typical applications: sensors and encoders.
Bonded Neodymium Iron Boron is used when a higher holding force is required than what bonded ferrite produces. It can be produced using Nylons, epoxies and various additives. In that it is isotropic and has a flat grain, it cannot be oriented at time of injection. It should also be coated in order to avoid corrosion. Typically it is using Magnequench powder.
Bonded Samarium Cobalt
Bonded Samarium Cobalt is the highest grade of material that can either be made by using nylon 12 or compression molded using epoxy. It was developed by Seiko Epson Corporation and can be made radial up to 15 Mgoe, cross field up to 17 Mgoe, and axially by similar method for 15 Mgoe. Typically used in high quality stepping motors, this material has been in the market place for over 30 years and IMI has yet to have a reject of any kind.
Cast Alnico was first developed in the 1930's and uses Aluminum, Nickel, and Cobalt from the lowest levels of Alnico Bonded up to Alnico 10 which is a hot mold exothermic material. This requires great foundry and heat treating expertise. It is still widely used in watt hour meters, instruments, and some holding devices such as pot magnets and medical devices.
Iron Chrome Cobalt
Iron Chrome Cobalt is a metal alloy of cobalt and chromium. Cobalt-chrome has a very high specific strength and is commonly used in gas turbines, dental implants, and orthopedic implants. This material is machinable and malleable and was originally designed as a replacement for Cunife. While it can still be used for this, the entire application must be known to match the properties needed. It requires a high degree of skill to make this material, and the manufacturer must be selected carefully.
Sintered Ferrite is called the work horse of the magnet industry. It contains critical materials such as iron, strontium/barium, and some binding agents. It is made like dishes and fired at high temperature. It is more flux for the bucks than any other material. The majority of ferrites are produced in China. Applications include loudspeakers and motors.
Sintered Radial Neodymium Iron Boron
Sintered SmCo has a high working temperature, superior resistance to corrosion, and is suitable for machines with strict working environments and high magnetic requirements. SmCo typically is identified within two families: rare earth SmCo5 (1:5 ) and Sm2Co17 (2:17).