MP 25x7.5/4.5x5 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their notable magnetism, neodymium magnets have these key benefits:

• They virtually do not lose power, because even after 10 years, the decline in efficiency is only ~1% (based on calculations),
• They are very resistant to demagnetization caused by external field interference,
• In other words, due to the shiny gold coating, the magnet obtains an stylish 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,
• With the option for fine forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Important function in modern technologies – they are utilized in hard drives, electric motors, clinical machines or even other advanced devices,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture , and at the same time increases its overall durability,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent deterioration 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,
• Magnets exposed to wet conditions can oxidize. Therefore, for outdoor applications, it's best to use waterproof types made of non-metallic composites,
• Limited ability to create precision features in the magnet – the use of a mechanical support is recommended,
• Health risk due to small fragments may arise, when consumed by mistake, which is important in the health of young users. Moreover, miniature parts from these magnets might disrupt scanning when ingested,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Optimal lifting capacity of a neodymium magnet – what affects it?

The given holding capacity of the magnet means the highest holding force, calculated under optimal conditions, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a polished side
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is affected by the following aspects, in descending order of importance:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) can cause 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 tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a small distance {between} the magnet’s surface and the plate lowers the load capacity.