MP 30x7/3x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They do not lose their even over around 10 years – the decrease of lifting capacity is only ~1% (based on measurements),
• They protect against demagnetization induced by external magnetic fields very well,
• By applying a shiny layer of silver, the element gains a modern look,
• They have extremely strong magnetic induction on the surface of the magnet,
• 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 shape),
• Thanks to the flexibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which expands their functional possibilities,
• Key role in cutting-edge sectors – they are used in hard drives, electric motors, clinical machines or even sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of magnetic elements:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to shocks, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from damage while also reinforces its overall durability,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is advisable to use sealed magnets made of plastic for outdoor use,
• Limited ability to create threads in the magnet – the use of a external casing is recommended,
• Possible threat related to magnet particles may arise, when consumed by mistake, which is notable in the health of young users. It should also be noted that miniature parts from these assemblies might hinder health screening if inside the body,
• In cases of mass production, neodymium magnet cost may be a barrier,

Maximum magnetic pulling force – what contributes to it?

The given pulling force of the magnet means the maximum force, assessed in a perfect environment, that is:

• with mild steel, used as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• with vertical force applied
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

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

• 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.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under parallel forces the holding force is lower. Moreover, even a small distance {between} the magnet and the plate lowers the lifting capacity.