Industrial magnets are manufactured for industrial use. They include individual magnets, bulk magnet materials, magnetic assemblies, magnetic sweepers, magnetic lifts, magnetic sheet handlers, magnetic retrievers, and permanent / electromagnet combinations.

Classification

Permanent magnets always exhibit magnetic properties, whether inside a magnetic field or not. Permanent magnet materials are designated by an MMPA (Magnetic Materials Producers Association) Class. Each addresses the relevant properties, characteristics and specifications of each material, and the established sub-grades.

Historically recognized sub-grade descriptions (such as Alnico 1, 2, etc., or Ceramic 5, 8, etc.) are often referenced. The Brief Designation classifies each subgrade by the normal energy product and the typical intrinsic coercive force.

For example, a material having a normal energy product of 5.0 megagauss-oersteds (MGO) and an intrinsic coercive force of 2000 Oersteds (2.0 kOe) would be assigned a Brief Designation of 5.01/2.0. Many times an IEC Grade Code will also be presented for cross-reference.

Specifications

Important specifications include materials, strength and holding force, form factor, magnetization and special features.

Materials

Common magnet materials for industrial magnets include, NdFeB (Neodymium Iron Boron), SmCo (Samarium Cobalt), Ceramic (Ferrite), AlNiCo (Aluminum-Nickel-Cobalt), and Iron-Chromium-Cobalt.

Strength and Holding Force

The two most important specifications to consider when searching for industrial magnets include strength and holding force. The maximum energy product is also known as the magnet strength or grade.

The point on the demagnetization curve where the product of B and H is a maximum and the volume of magnet material required to project a given energy into its surroundings is a minimum. It is measured in megagauss-oersteds, MGOe.

The holding force is the force the magnet is capable of holding under ideal conditions. Conditions such as the size and shape of the parts, the surface conditions, motion, vibration, friction, holding angles, and machining forces will affect the holding force of the magnet and should be factored into the magnetic circuit design.

Physical Forms

• Block or bar
• Flexible strip or sheet
• Sheet or slab
• Rod
• Powder
• Horse shoe or U-shaped
• Button or pot
• Round, ring or disc
• Sphere or bead
• Arc segment
• Rotor or poles

Magnet Demonstration. Video Credit: Industrial Magnetics, Inc. / CC BY-IN 4.0

Magnetization

The magnet can be non-magnetized, conventional magnetization or multiple magnetizations. A non-magnetized magnet can be magnetized after it has been assembled in the magnetic circuit. A conventional magnet has one pole on each side, the north pole on one side, and the south pole on the other.

Magnets can be magnetized through the thickness, length, or diameter. A magnet with multiple magnetizations has multiple poles on each side. There are two or more sets of poles on each surface. North and South poles alternate through the thickness of the material. The number of poles on one face of the magnet is also important to consider.

Magnetizer/Demagnetizer. Video Credit: Industrial Magnetics, Inc. / CC BY-SA 4.0

Other Physical Specifications

• Weight
• Width
• Length
• Thickness or height
• Outside diameter and inside diameter

Features

• Machinable
• Coatings
• Manual release

Standards

ASTM 03.04 - Magnetic properties.

ASTM E709 - Standard guide for magnetic particle testing.

A-A-59167 - Magnet materials, permanent.

BS PD IEC/TR 62517 - Magnetizing behavior of permanent magnets.

Image credits:

Comus International | elobau sensor technology, Inc.