Different Types and Shapes of Permanent Magnets

Permanent Magnets

Alternative energy ideas involve intensive use of permanent magnets. The new rare earth magnets give super power raped up in small light weight packages. Below is a brief history and the pro's and con's of permanent magnets. With the use of super powerful permanent magnets alternative energy units that utilize wind, wave and other earthly phenomena can begin to help in meeting our energy need with out destroying the planet.

Developed in the early 1940's, the Alnico (aluminum, nickel, cobalt) family of magnets remains the material of choice for many applications. Its excellent linear temperature characteristics, high magnetic flux density, and good corrosion resistance are ideally suited for use in products of all sizes - from miniscule cellular telephone magnets weighing less than a gram to radar focusing magnets weighing 50 pounds or more.

Polymer bonded magnets have opened a new world of application opportunities. Thermo-elastomer and thermo-plastic resins can be compounded with a variety of magnetic powders to form Injection Molded, Compression Bonded and Flexible Calendared products. Injection molded magnets can be formed into complex shapes and molded directly onto other components reducing assembly costs. Compression bonded magnets, while of simpler geometries, offer higher magnetic output. Flexible sheet and strip is used in many applications including small motors, flexographic (printing) devices, magnetic filtering, and signs.

Custom fabricated magnets from the Ogallala Electronics Division utilize diverse materials in the fabrication of assemblies including metal stampings, sintered powder metal forms, foam urethane and rubbers, engineering epoxies, potting compounds, plastics, etc. All commercially available permanent magnet materials can be utilized. Capabilities include slice/dice, centerless and surface grinding, gluing, edge deburr and magnetic testing. A hysteresisgraph, gauss and flux meters allow conformance to industry and customer standards. Existing products are used in such applications as automobiles, electronic instrumentation, oil field exploration, and ultrasonic transducers.

Hard ferrite (ceramic) magnets were developed in the early 1960's as a low-cost alternative to metallic magnets (steels and alnico). Even though they exhibit lower energy when compared with other materials available today and are relatively hard and brittle, ferrite magnets have won wide acceptance due to their high resistance to demagnetization, outstanding corrosion resistance and low price per magnetic output.

Sintered neodymium-iron-boron (NdFeB) magnets, also referred to as "neo" magnets, have been commercially available since November 1984. They offer the highest energy product of any material today and are available in a very wide range of shapes, sizes and grades. Earliest use of neo magnets was primarily for voice coil motors (VCM's) in hard disk drives and this market still accounts for about 55% of total sales dollars. Other applications include high performance motors, brushless DC motors, magnetic separation, magnetic resonance imaging, sensors and loudspeakers.

Samarium cobalt magnets were first commercially available about 1970. Two materials have been developed to-date: SmCo5 and Sm2Co17. These materials are stronger than ferrite and alnico magnets and became widely used in high output motors where weight and size are an issue. They were also introduced into sensor applications where temperature stability was of importance. While neodymium iron boron magnets have replaced samarium cobalt in many applications, samarium cobalt is still used where high temperature performance, excellent thermal stability or excellent corrosion resistance is required. They are available from the Swift Levick Magnets Division in arcs, rods, flats, blocks and many other custom shapes.

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