MP 41x15x10 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their immense magnetic power, neodymium magnets offer the following advantages:

• They have stable power, and over around 10 years their performance decreases symbolically – ~1% (in testing),
• They show strong resistance to demagnetization from external magnetic fields,
• Thanks to the glossy finish and silver coating, they have an elegant appearance,
• They exhibit elevated 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,
• Thanks to the flexibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their functional possibilities,
• Wide application in advanced technical fields – they are used in computer drives, electric drives, clinical machines and sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They may fracture when subjected to a powerful impact. If the magnets are exposed to shocks, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks and increases its overall resistance,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). 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 damp air can rust. Therefore, for outdoor applications, we suggest waterproof types made of plastic,
• Limited ability to create precision features in the magnet – the use of a mechanical support is recommended,
• Safety concern from tiny pieces may arise, especially if swallowed, which is notable in the health of young users. Additionally, miniature parts from these magnets have the potential to hinder health screening after being swallowed,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which may limit large-scale applications

Magnetic strength at its maximum – what it depends on?

The given holding capacity of the magnet represents the highest holding force, calculated under optimal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with zero air gap
• in a perpendicular direction of force
• at room temperature

Lifting capacity in practice – influencing factors

The lifting capacity of a magnet is influenced by in practice key elements, ordered from most important to least significant:

• Air gap between the magnet and the plate, as 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.

* Lifting capacity testing was performed on a smooth plate of suitable thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.