MP 40x22x10 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They do not lose their magnetism, even after approximately ten years – the loss of lifting capacity is only ~1% (theoretically),
• They are very resistant to demagnetization caused by external magnetic fields,
• In other words, due to the metallic silver coating, the magnet obtains an professional appearance,
• Magnetic induction on the surface of these magnets is notably high,
• With the right combination of compounds, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the design),
• Thanks to the freedom in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in various configurations, which increases their application range,
• Key role in cutting-edge sectors – they are utilized in computer drives, rotating machines, healthcare devices and other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which makes them useful in compact constructions

Disadvantages of NdFeB magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to mechanical hits, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage while also increases its overall robustness,
• They lose strength at elevated temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the dimensions and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• 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 limitations in manufacturing holes directly in the magnet,
• Potential hazard from tiny pieces may arise, when consumed by mistake, which is significant in the protection of children. It should also be noted that minuscule fragments from these magnets may complicate medical imaging if inside the body,
• Due to a complex production process, their cost is relatively high,

Maximum lifting force for a neodymium magnet – what contributes to it?

The given strength of the magnet means the optimal strength, assessed under optimal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Magnet lifting force in use – key factors

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• 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 conducted on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, in contrast under shearing force the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate decreases the holding force.