MP 20x8/4x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their durability, neodymium magnets are valued for these benefits:

• They have stable power, and over around 10 years their attraction force decreases symbolically – ~1% (according to theory),
• Their ability to resist magnetic interference from external fields is impressive,
• Because of the lustrous layer of nickel, the component looks high-end,
• They have very high magnetic induction on the surface of the magnet,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• Thanks to the freedom in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in diverse shapes and sizes, which increases their usage potential,
• Key role in cutting-edge sectors – they are utilized in data storage devices, rotating machines, medical equipment and technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in tiny dimensions, which makes them useful in small systems

Disadvantages of rare earth magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to external force, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage while also strengthens its overall durability,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening 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,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of protective material for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing fine shapes directly in the magnet,
• Possible threat linked to microscopic shards may arise, especially if swallowed, which is significant in the context of child safety. Moreover, tiny components from these products may interfere with diagnostics when ingested,
• Due to a complex production process, their cost is relatively high,

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

The given holding capacity of the magnet represents the highest holding force, determined in the best circumstances, specifically:

• 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 smooth surface
• with no separation
• in a perpendicular direction of force
• under standard ambient temperature

Determinants of practical lifting force of a magnet

In practice, the holding capacity of a magnet is affected by the following aspects, from crucial to less important:

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

* Holding force was tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under parallel forces the holding force is lower. In addition, even a minimal clearance {between} the magnet and the plate reduces the holding force.