FERRITE MAGNETS - ANISOTROPIC MFA
INTRODUCTION
Ferrite magnets are made from Black Rust/Iron Oxide (Fe2O3) mixed with various additives including Barium Carbonate for isotropic magnets and Strontium Carbonate for anisotropic magnets. There are two pressing methods, wet pressing and dry pressing. The "green" biscuit magnet is then fired in a furnace to become a solid material, a similar process to producing bone china and pottery and, for this reason, ferrite magnets are also known as ceramic magnets. All ferrite magnets give their best performance when magnetized through the thinnest dimension, called the "T" axis. Ferrite magnets are the most popular type by usage as they are economically priced and available in a wide variety of shapes and sizes.
ANISOTROPIC FERRITE MAGNETS
When pressed in the "green' stage anisotropic magnets are polarized with a strong DC magnetic field which does not magnetize the ferrite but aligns the domains and dictates the direction in which the ferrite can be magnetized in a subsequent magnetization process. Most anisotropic ferrite magnets are plainly magnetized through the "T" axis, but multipole magnetization is also possible. Anisotropic ferrites are widely used in industry for magnetic separators, head pulleys, loudspeakers, fan and wiper motors, vibrators, MRI scanners, etc.
RING
Size = Outside Diameter (OD) x
Inside Diameter (ID) x
Thickness (T) mm
Magnetized T
|
200 |
100 |
20 |
|
134 |
56 |
20 |
|
103 |
43 |
18 |
|
90 |
36 |
12 |
|
86 |
32 |
15 |
|
72 |
32 |
15 |
|
72 |
32 |
10 |
|
60 |
32 |
10 |
|
60 |
24 |
8 |
|
53 |
24 |
11 |
|
45 |
22 |
8 |
|
36 |
18 |
8 |
|
33 |
22 |
5 |
|
32 |
18 |
5.5 |
|
30 |
8 |
5 |
|
20 |
5 |
10 |
|
17 |
7 |
3 |
|
14 |
5 |
2 |
|
|
|
|
Other sizes are available from our magnet factories.
DISC
Size = Diameter (D) x
Thickness (T) mm
Magnetized T
|
30 |
15 |
|
30 |
10 |
|
30 |
5 |
|
22 |
25 |
|
20 |
10 |
|
20 |
5 |
|
15 |
8 |
|
12.5 |
4.7 |
|
8 |
8 |
|
|
|
Other sizes are available from our magnet factories.
RECTANGULAR
Size = Length (L) x Width (W) x Thickness (T) mm
Magnetized T
|
50 |
100 |
25 |
|
|
150 |
100 |
12.7 |
|
|
150 |
25 |
25 |
|
|
102 |
40 |
25.4 |
|
|
75 |
25 |
25 |
|
|
75 |
50 |
10 |
|
|
60 |
30 |
10 |
|
|
50 |
50 |
20 |
|
|
50 |
19 |
5 |
|
|
47.6 |
27.2 |
5 |
|
|
40 |
25 |
10 |
Cut block |
|
25 |
20 |
5 |
|
|
25 |
20 |
10 |
|
|
15 |
13 |
5 |
|
|
|
|
|
OTHER RECTANGULAR SHAPES
Non standard sizes and shapes can be cut from larger blocks, normally 25.4mm and 12.7mm thick. Cutting is performed only on unmagnetized ferrites as cutting of magnetized magnets is difficult, if not impossible, as small pieces of material from the cut adhere to the cutting blade. This, in turn, prevents a clean cut and normally the ferrite cracks. Diamond wheels are used to cut the ferrite and only straight cuts can be performed. A tolerance of pus minus 0.5mm can be anticipated. Minor corner cracks must be tolerated as these cannot be avoided. This type of fabrication known as "slice and dice" allows non standard or non available sizes to be fabricated.
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