Ask A Scientist© Engineering Archive

Index Key:   ENG020
Author:      harden
Subject:     Permanent magnet manufacture
Text:        How are permanent magnets commercially made?

Response #:  1 of 1
Author:      dipper
Text:        I do not know how they are made on a large scale, and I will bet 
that each type of magnet is made differently.  Maybe others will help outhere.  
I can tell you how they are made for permanent magnet motors though.  Once the 
material is cast (Alnico, Sumarian Cobalt, "Neo-Iron", etc.) ground, and heat 
treated (in some cases), it has no particular magnetic field.  In the case of 
a PM motor, they are all placed in the motor stator housing (or around the 
rotor in the case of  brushless systems) and placed around a cone with wire 
windings and magnetic steel on them.  It is a special machine that charges 
large capacitors, and then very rapidly discharges them through the coil 
surrounded by the magnetic material.  Depending upon the air gap, and the rate 
of discharge, and the amount of the charge, as well as the material used, 
after each discharge it will yield magnetic fields around the material in the 
motor.  A good source for this data is a magazine called "Motion" published by 
Dr. Jacob Tal in California.