SM 25x275 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They virtually do not lose strength, because even after 10 years, the decline in efficiency is only ~1% (according to literature),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• Thanks to the polished finish and gold coating, they have an aesthetic appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• Thanks to the flexibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in different geometries, which increases their usage potential,
• Important function in cutting-edge sectors – they find application in HDDs, electromechanical systems, medical equipment along with technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small 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 mechanical hits, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage , and at the same time strengthens 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 size). 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,
• They rust in a wet environment – during outdoor use, we recommend using encapsulated magnets, such as those made of non-metallic materials,
• Limited ability to create complex details in the magnet – the use of a magnetic holder is recommended,
• Health risk related to magnet particles may arise, in case of ingestion, which is notable in the context of child safety. Additionally, small elements from these assemblies might disrupt scanning once in the system,
• Due to the price of neodymium, their cost is considerably higher,

Maximum lifting capacity of the magnet – what contributes to it?

The given pulling force of the magnet represents the maximum force, calculated in a perfect environment, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• of a thickness of at least 10 mm
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• under standard ambient temperature

What influences lifting capacity in practice

In practice, the holding capacity of a magnet is conditioned by these factors, in descending order of importance:

• 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 checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet’s surface and the plate reduces the lifting capacity.