Designing Permanent Magnets

Ferromagnetic materials are typically derived from iron, nickel and cobalt in addition to choice alloys of earth metals and naturally occurring minerals. While only ferromagnetic materials are drawn so powerfully to permanent magnets, all substances respond to the magnetism and would be considered to be weakly attracted to magnets. Such magnetized relationships are utilized in a variety of technologies, including old VHS and cassettes, credit and debit cards, televisions and computers, speakers, microphones, musical instruments like electric guitars, motors, generators, compasses and even, modern medicine through magnetic resonance imaging.

The actual design of permanent magnets can be an elaborate task involving the right materials, sizes and geometries. While the testing process of permanent magnets cannot be utilized ahead of time but must be induced only after the magnet has been built. Today there are four common classes of commercially sold magnets and each class has its own composition and magnetic properties such as alnico, ceramic, samarium cobalt and neodymium iron boron. Depending on the material, there are three units of measurement common between them that designers should familiarize themselves with. They are the unit of centimeters, grams and seconds, the unit of meters, kilograms and seconds, and the English unit of inches, pounds and seconds

  1. To begin, first specify the design of the magnet. Coercivity (Hc) measures how the magnetic field of the material switches from positive to negative. Magnetic flux density (B) measures the power of the magnetic field and varies from material to material, depending on both the properties of the material and the dimensions of the material. There are many common procedures to consider throughout the process of designing permanent magnets, but these two factors are the paramount consideration. Both factors should be used in order to estimate the permanent magnet.
  2. Now comes, choosing the actual material. These factors will come to measure, and as such, which material you choose is dependent on your own design specifications.
  3. Because the materials of permanent magnets are often taken from earth alloys like neodymium iron boron and samarium cobalt, the natural magnetism of those alloys will be taken into further consideration. Designs requiring high magnetic flux density which requires alloy materials with high magnetic flux, like neodymium iron boron, which design specifications denoting smaller fields are better fitted with materials like alnico.
  4. Finally, the actual dimensions of the materials to aide in your permanent magnet must be chosen. This will be the final deciding factor in the kind of magnetic field that will be produced, as the field will scale itself to the total volume of the given material. Finite elemental packages like COMSOL help to model the kind of field produced, and this test is no more trying than inputting the geometry of the magnet and the flux density of the material. Once these specifications are calculated, it’s time to purchase the magnetic material and begin testing.

Fabricating permanent magnets are a specialized process, and fabricating them in a laboratory by you is not recommended. Magnetic materials should be purchased from a specialized external source and then professionally machined to the specified geometry and perimeters. A portable electric device made to measure magnetic fields, such as a Gauss meter, should be used when testing the permanent magnet. To measure the magnetic field with a Gauss meter, situated the probe beside the proper side of the permanent magnet until the magnet’s strength is displayed on the LCD of the portable device. While there are three units of measurement in magnetism, a common conversion factor follows: one Tesla is equal to ten thousand Gauss.

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Andrew writes on behalf of Jobmaster Magnets. A company that is into manufacturing implementation of heavy permanent magnets and others