MP 12x8/4x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets.

Besides their remarkable field intensity, neodymium magnets offer the following advantages:

• They have constant strength, and over nearly 10 years their attraction force decreases symbolically – ~1% (according to theory),
• They possess excellent resistance to weakening of magnetic properties when exposed to opposing magnetic fields,
• In other words, due to the smooth layer of nickel, the element becomes visually attractive,
• They are known for high magnetic induction at the operating surface, which increases their power,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to flexibility in shaping and the ability to adapt to unusual requirements,
• Universal use in innovative solutions – they are used in hard drives, brushless drives, diagnostic systems, also multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in small dimensions, which makes them useful in compact constructions

Drawbacks and weaknesses of neodymium magnets: weaknesses and usage proposals

• To avoid cracks under impact, we recommend using special steel housings. Such a solution secures the magnet and simultaneously increases its durability.
• Neodymium magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material stable to moisture, when using outdoors
• Due to limitations in creating nuts and complex shapes in magnets, we propose using a housing - magnetic mount.
• Health risk to health – tiny shards of magnets are risky, if swallowed, which gains importance in the context of child safety. It is also worth noting that small elements of these devices are able to disrupt the diagnostic process medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Highest magnetic holding force – what affects it?

The declared magnet strength concerns the limit force, measured under optimal environment, specifically:

• on a plate made of mild steel, effectively closing the magnetic field
• with a thickness no less than 10 mm
• characterized by lack of roughness
• without any air gap between the magnet and steel
• during pulling in a direction vertical to the mounting surface
• at room temperature

Magnet lifting force in use – key factors

During everyday use, the real power results from several key aspects, ranked from most significant:

• Distance – existence of foreign body (paint, dirt, air) acts as an insulator, which lowers power rapidly (even by 50% at 0.5 mm).
• Pull-off angle – remember that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the nominal value.
• Plate thickness – insufficiently thick steel causes magnetic saturation, causing part of the power to be escaped to the other side.
• Material type – the best choice is pure iron steel. Hardened steels may generate lower lifting capacity.
• Surface finish – ideal contact is obtained only on smooth steel. Rough texture reduce the real contact area, reducing force.
• Operating temperature – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and in frost gain strength (up to a certain limit).

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, whereas under shearing force the holding force is lower. In addition, even a slight gap {between} the magnet and the plate lowers the holding force.