Magnets Technical Information
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Basics of... Magnets
Selection Factors
When selecting a magnet for your application, consider the physical shape of the part (round, convex, concave, etc.) and the surface condition (rough, rusty, dirty, oily). Both can result in *air gaps between the contact points on the magnet & the work material, thereby reducing the magnetic holding power. These factors and the information in this section will aid in choosing the correct magnet for your application.
*Air gap: Space between the part and the magnet (paint, plating, galvinizing, protective film, etc...)
Applications :
- Holding metal sheets and parts in place
- Safety shield/removable panel mounts
- Overhead conveyor racks
- Separating stacks of sheet metal
- Die inserts
- Paint and plating racks
- Spot welding fixtures
- Hand assembly fixtures
- Shearing, punching and forming operations
- Press and Burn Table feeding operations
- Capturing or separating metal
- Cleaning or lifting metal from floors & more
Maximum Pull vs. Average Pull
Maximum pull and average pull are derived from the same magnet but differ in how you present the information. We have chosen to use average pull in our catalog. The maximum pull value is obtained by pulling a new magnet in a perpendicular motion off of a newly machined, thick piece of steel (ideal conditions is a lab). The pounds of pull it takes to break the magnet away from the steel surface is the "maximum" pull pounds. Average pull values are then derived by taking this maximum pull pounds and cutting it in half (50%). The average pull pounds are stated for the benefit and safety of the user, due to the fact that ideal conditions rarely exist in the field. Refer back the "magnet selection factors" for the part shape and surface conditions.
Materials
Flexible Magnetic Strips: made of a Ferro Magnetic powder with a polymer bonding. These low energy strips resist demagnetization and will not chip, crack or shatter. Flexible magnets form to any contour, used in office, manufacturing and inventory labeling and appliance, advertising applications. Flexible magnets can be cut drilled or shaped. Maximum temperature 160 F (70C).
Ceramic: made of Strontium Ferrite (SrFe) in a sintering process. Ceramic magnets are staples in the electronic, automotive, medical, mining, industrial, oil industries, etc. Ceramic magnets are medium strength magnet material with a high resistance to demagnetization, long time stability (losses 0.5% of its magnetic strength in 100 years), brittle material that has to be cut with diamond tipped blades. Maximum temperature 350 F (176 C).
Alnico: made of Aluminum, Nickel and Cobalt (AlNiCo) in either a casting or sintering process. Used in application environments that have high heat, Alnico magnets offer medium strength and the best temperature characteristics of any standard magnet material. Alnico magnets have a medium resistance to demagnetization and are very hard and brittle. Machining or drilling cannot be accomplished by ordinary means. Maximum temperature 800 F (427 C)
Rare Earth Neodymium-Iron-Boron (NdFeB) Magnets: made in a sintered as well as bonded forms. Commonly referred to as Neo, this magnet material provides the highest magnetic strength of any magnet material, very high resistance to demagnetization and is ideal for applications requiring maximum strength in a limited area. Because of its high iron content, Neo is usually coated or plated to prevent oxidization; avoid grinding. Maximum temperature 200 F (94 C).
Rare Earth Samarium Cobalt (SmCo): made the same as Neo. Samarium Cobalt has the highest magnetic strength combined with high temperature range which makes it ideal for applications requiring very high strength in hot environments. Maximum temperature 392 F (200 C).
Permanent Magnetic Material Properties
| Type | Components | Magnetic Strength | Maximum Temperature | Resistance to Demagnetization | Color | Machineable |
|---|---|---|---|---|---|---|
| Flexible | Ferrite Magnetic Powder with a Polymer Bonding | Very Low | 160°F (70°C) | Low | Dark Brown | Drill, Scissors |
| Ceramic | Strontium Ferrite | Low | 350°F (176°C) | High | Dark Gray | Diamond Wheel |
| Alnico | Aluminum-Nickel-Cobalt | Medium | 800°F (427°C) | Medium | Silver | EDM |
| Rare Earth | Neodymium-Iron-Boron Unplated | Very High | 200°F (94°C) | Very High | Dark Green | Avoid Grinding |
| Rare Earth | Neodymium-Iron-Boron Nickel Plated | Very High | 200°F (94°C) | Very High | Bright Silver | Avoid Grinding |
| Rare Earth | Samarium Cobalt | Very High | 392°F (200°C) | Very High | Dark Gray | Avoid Grinding |
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