MP 25x8x5 / N38 - ring magnet

Advantages as well as disadvantages of NdFeB magnets.

Apart from their notable holding force, neodymium magnets have these key benefits:

• Their strength is durable, and after approximately ten years it decreases only by ~1% (theoretically),
• They show high resistance to demagnetization induced by presence of other magnetic fields,
• The use of an aesthetic coating of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Magnets possess excellent magnetic induction on the working surface,
• With the right combination of magnetic alloys, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the design),
• Possibility of detailed machining and adjusting to specific needs,
• Key role in modern technologies – they serve a role in magnetic memories, drive modules, precision medical tools, also other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which enables their usage in miniature devices

Disadvantages of neodymium magnets:

• To avoid cracks under impact, we suggest using special steel holders. Such a solution protects the magnet and simultaneously improves its durability.
• When exposed to high temperature, neodymium magnets experience a drop in power. Often, when the temperature exceeds 80°C, their power decreases (depending on the size and shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• Limited ability of producing threads in the magnet and complicated shapes - preferred is cover - mounting mechanism.
• Health risk to health – tiny shards of magnets pose a threat, if swallowed, which gains importance in the context of child safety. It is also worth noting that small components of these devices can complicate diagnosis medical when they are in the body.
• Due to complex production process, their price exceeds standard values,

Optimal lifting capacity of a neodymium magnet – what it depends on?

The load parameter shown refers to the peak performance, obtained under ideal test conditions, specifically:

• on a block made of mild steel, effectively closing the magnetic field
• whose thickness is min. 10 mm
• with a surface perfectly flat
• with zero gap (no paint)
• during detachment in a direction perpendicular to the mounting surface
• in temp. approx. 20°C

Impact of factors on magnetic holding capacity in practice

In practice, the actual lifting capacity is determined by many variables, ranked from crucial:

• Clearance – the presence of any layer (rust, tape, air) acts as an insulator, which lowers power rapidly (even by 50% at 0.5 mm).
• Force direction – catalog parameter refers to pulling vertically. When slipping, the magnet holds much less (typically approx. 20-30% of nominal force).
• Element thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet limits the lifting capacity (the magnet "punches through" it).
• Steel type – low-carbon steel gives the best results. Alloy steels reduce magnetic permeability and lifting capacity.
• Surface finish – ideal contact is possible only on smooth steel. Rough texture create air cushions, weakening the magnet.
• Operating temperature – NdFeB sinters have a negative temperature coefficient. At higher temperatures they lose power, and in frost gain strength (up to a certain limit).

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the lifting capacity is smaller. In addition, even a slight gap {between} the magnet’s surface and the plate lowers the holding force.