MP 20x8/4x3 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They retain their attractive force for almost ten years – the loss is just ~1% (based on simulations),
• Their ability to resist magnetic interference from external fields is notable,
• By applying a reflective layer of nickel, the element gains a modern look,
• Magnetic induction on the surface of these magnets is impressively powerful,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to form),
• Thanks to the possibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their usage potential,
• Important function in new technology industries – they are utilized in data storage devices, electric motors, healthcare devices and other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in tiny dimensions, which makes them useful in compact constructions

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to physical collisions, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall durability,
• They lose magnetic force at increased temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to wet conditions can corrode. Therefore, for outdoor applications, it's best to use waterproof types made of non-metallic composites,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing holes directly in the magnet,
• Possible threat linked to microscopic shards may arise, when consumed by mistake, which is significant in the protection of children. Furthermore, small elements from these magnets may interfere with diagnostics after being swallowed,
• Due to expensive raw materials, their cost is above average,

Maximum holding power of the magnet – what affects it?

The given lifting capacity of the magnet means the maximum lifting force, assessed in a perfect environment, specifically:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• under perpendicular detachment force
• at room temperature

Determinants of practical lifting force of a magnet

In practice, the holding capacity of a magnet is affected by these factors, arranged from the most important to the least relevant:

• 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.

* Lifting capacity testing was carried out on a smooth plate of suitable thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.