The Complete Handbook of Magnetizers & Demagnetizers

Chapter 1: Understanding Magnetizers & Demagnetizers

A magnetizer is a machine that forces a permanent magnetic field into a ferromagnetic part, and a demagnetizer is a machine that does the opposite: it removes a net magnetic field from a part. These functions are not niche laboratory tricks. They are everyday production steps in industries as routine as automotive manufacturing, electric motor repair, injection molding, and metal stamping. When a manufacturer needs a permanent magnet motor rotor to hold its field for years, it uses a magnetizer. When a machinist needs a steel vise to stop holding onto every piece of swarf and steel shaving, he uses a demagnetizer. Understanding how these machines work is essential to using them correctly, and knowing what they actually do, physically, prevents costly mistakes that range from failing a final quality test to destroying a valuable part in a split second.

What the Machines Actually Do

At the most basic level, a magnetizer delivers a brief, intense burst of magnetic field to a workpiece. This burst aligns the magnetic domains inside the material. A ferromagnetic material, such as iron, nickel, or cobalt, is made of microscopic regions called domains, each of which is itself a tiny magnet. In an unmagnetized state, these domains point in random directions and cancel each other out. When you apply an external magnetic field, the domains that are aligned with that field grow at the expense of others, and the boundaries between them shift. If the applied field is strong