Magnet FAQ

There is a Difference in Magnets

Why do rare earth magnets differ in cost?
Just as there are many grades of alnico and ceramic materials, there are also different grades of rare earth materials. They are developed by several magnet material producers throughout the world, which accounts for quite a diversity in terms of energies, high temperature capabilities, and corrosion resistance.

Are magnet grades a safe guideline for selection?
Typically, each magnet material producer has a unique selection of magnet grades that may be similar to, but not identical to, those of competitors. This can lead to some confusion when a particular application is being considered. Also, most magnet material producers continue to improve their magnet materials within each grade, making magnet comparison an ongoing process.

Is there a published guide to magnet materials?
The Magnetic Materials Producers Association (8 South Michigan Avenue, Suite 1000, Chicago, IL 60603, Voice: (312)456-5590, FAX: (312)580-0165) publishes the “MMPA Standard 0100 – Standard Specifications for Permanent Magnet Materials”. This guide lists the nominal values for various grades and types of magnet materials. However, the latest manual (No. 0100-96) lists NdFeB magnets only up through 44 MGOe, and several manufacturers are presently using materials beyond that grade.

What is the difference between equivalent and alternate substitutions?
The fact that there are so many different magnet material producers making so many different grades of rare earth magnets makes it even more important that material substitutions be evaluated. An equivalent circuit would perform the same as the original circuit, whereas an alternate circuit would have different performance characteristics. Simple substitution of lower grade, less expensive material into an established circuit design almost always results in an alternate circuit, with performance inferior to the original circuit.

What performance characteristics could be affected by substitutions?
Substituting low-cost magnetic materials could result in a reduction of the magnetic field, greater sensitivity to temperature, and reduction in the life of the magnet.

What is the real price you pay when you choose a low-cost magnet material?
You risk a lot with inferior magnetic materials. All rare earth magnets are not equal. If suppliers are using inferior “low-cost” magnet material, where else are they cutting corners? Low-cost substitutes may work for specific applications, or within some constraints, but at the forfeiture of performance. Some of the most important factors include average gauss, pull tests (force), temperature effect, long-term stability (corrosion), and irreversible losses in magnetic strength.

Is there a difference in rare earth magnetic equipment?
The correct magnetic circuit geometry and the proper magnet material selection are critical design parameters when it comes to good equipment design. They interact in such a way as to affect the field strength, temperature range, and stability of the circuit. The name “rare earth” suggests that the equipment is high in magnetic strength, but the correct circuit design is critical to its success.

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