MW 45x35 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• Their power is maintained, and after around ten years, it drops only by ~1% (according to research),
• Their ability to resist magnetic interference from external fields is impressive,
• Thanks to the polished finish and gold coating, they have an visually attractive appearance,
• The outer field strength of the magnet shows advanced magnetic properties,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• With the option for fine forming and personalized design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Key role in new technology industries – they serve a purpose in hard drives, rotating machines, diagnostic apparatus along with high-tech tools,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They may fracture when subjected to a strong impact. If the magnets are exposed to external force, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and increases its overall robustness,
• High temperatures may significantly reduce the strength of neodymium magnets. Typically, above 80°C, they experience permanent loss in performance (depending on shape). 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 corrode. Therefore, for outdoor applications, we recommend waterproof types made of rubber,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is restricted,
• Potential hazard from tiny pieces may arise, in case of ingestion, which is notable in the family environments. Moreover, miniature parts from these assemblies have the potential to disrupt scanning if inside the body,
• Due to expensive raw materials, their cost is relatively high,

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

The given lifting capacity of the magnet corresponds to the maximum lifting force, assessed in the best circumstances, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Practical lifting capacity: influencing factors

The lifting capacity of a magnet is determined by in practice key elements, according to their importance:

• 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 was measured with the use of a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular pulling force, however under parallel forces the holding force is lower. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the lifting capacity.