MP 32x16x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their strong power, neodymium magnets have these key benefits:

• They do not lose their magnetism, even after nearly 10 years – the loss of power is only ~1% (theoretically),
• They protect against demagnetization induced by external magnetic fields remarkably well,
• The use of a decorative nickel surface provides a eye-catching finish,
• Magnetic induction on the surface of these magnets is very strong,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which increases their functional possibilities,
• Significant impact in advanced technical fields – they serve a purpose in computer drives, electric drives, diagnostic apparatus and sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which makes them useful in compact constructions

Disadvantages of neodymium magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to external force, it is advisable to use in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage and additionally enhances its overall robustness,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent deterioration 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 humidity can oxidize. Therefore, for outdoor applications, we suggest waterproof types made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing complex structures directly in the magnet,
• Safety concern related to magnet particles may arise, in case of ingestion, which is notable in the family environments. Additionally, small elements from these assemblies can disrupt scanning after being swallowed,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which may limit large-scale applications

Maximum lifting capacity of the magnet – what affects it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, measured in the best circumstances, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

Determinants of practical lifting force of a magnet

The lifting capacity of a magnet is determined by in practice the following factors, from primary to secondary:

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

* Lifting capacity was measured by applying a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular pulling force, however under parallel forces the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate lowers the holding force.