SMZR 25x250 / N52 - magnetic separator with handle

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their remarkable field intensity, neodymium magnets offer the following advantages:

• Their power is durable, and after around 10 years, it drops only by ~1% (theoretically),
• They protect against demagnetization induced by surrounding magnetic influence remarkably well,
• Because of the lustrous layer of gold, the component looks high-end,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for customized forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Important function in cutting-edge sectors – they are used in data storage devices, electric drives, clinical machines as well as high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in tiny dimensions, which makes them ideal in compact constructions

Disadvantages of rare earth magnets:

• They may fracture when subjected to a powerful impact. If the magnets are exposed to external force, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on shape). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Magnets exposed to moisture can oxidize. Therefore, for outdoor applications, we advise waterproof types made of coated materials,
• Limited ability to create threads in the magnet – the use of a external casing is recommended,
• Potential hazard from tiny pieces may arise, especially if swallowed, which is significant in the family environments. It should also be noted that minuscule fragments from these assemblies may interfere with diagnostics when ingested,
• Due to a complex production process, their cost is above average,

Maximum holding power of the magnet – what affects it?

The given lifting capacity of the magnet means the maximum lifting force, calculated in the best circumstances, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Magnet lifting force in use – key factors

In practice, the holding capacity of a magnet is conditioned by these factors, arranged from the most important to the least relevant:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) causes a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under shearing force the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate reduces the load capacity.