Page 642 - Mechatronics with Experiments

628 MECHATRONICS
duration can also be in the order of seconds depending on the magnet material being
magnetized. Since the handling of magnetized permanent magnet pieces is difficult, it
is desirable to magnetize the magnets as late as possible in the manufacturing process
for a given magnetic product application.
8. Finally, the permanent magnet batch should be treated with stabilization and calibra-
tion processes. The calibration process makes sure that the magnetic strength of each
piece is within a certain tolerance of the desired specifications (i.e., ±1%).

Typical shapes and magnetization directions of permanent magnets are shown in
Figure 8.15. There is a critical temperature, called the Curie temperature for each ferro-
magnetic material above which the material losses its ferromagnetic properties and becomes
◦
◦
a paramagnetic material. The Curie temperature for iron is 1043 K, for cobalt 1394 K,

N M S
M
S N
Parallel to length Parallel to thickness

N
S

Multiple pole 2 poles 1 face
M
N
M

N
S
Parallel to length Parallel to thickness
N
N S

N S N N N
S
S
Radial 4 poles - 1 face

N S

2 poles - 1 face
FIGURE 8.15: Typical shapes and magnetization directions of permanent magnets. The letter
M with arrows indicates the magnetization direction of the piece.