MW 20x5 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They retain their attractive force for around 10 years – the loss is just ~1% (based on simulations),
• Their ability to resist magnetic interference from external fields is impressive,
• The use of a decorative gold surface provides a eye-catching finish,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• With the right combination of materials, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• Thanks to the possibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in various configurations, which increases their application range,
• Significant impact in cutting-edge sectors – they serve a purpose in computer drives, electromechanical systems, medical equipment as well as technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in compact dimensions, which makes them ideal in miniature devices

Disadvantages of magnetic elements:

• They are fragile when subjected to a strong impact. If the magnets are exposed to mechanical hits, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks and additionally increases its overall robustness,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on form). 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 damp environment, especially when used outside, we recommend using moisture-resistant magnets, such as those made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing holes directly in the magnet,
• Possible threat from tiny pieces may arise, in case of ingestion, which is crucial in the family environments. Moreover, small elements from these magnets may hinder health screening after being swallowed,
• In cases of tight budgets, neodymium magnet cost may be a barrier,

Breakaway strength of the magnet in ideal conditions – what affects it?

The given lifting capacity of the magnet represents the maximum lifting force, measured in ideal conditions, that is:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a smooth surface
• with no separation
• with vertical force applied
• at room temperature

Lifting capacity in practice – influencing factors

Practical lifting force is determined by factors, by priority:

• Air gap between the magnet and the plate, as 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 a perpendicular force was applied, whereas under parallel forces the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate reduces the load capacity.