MP 30x6x10 / N38 - ring magnet

Pros and cons of neodymium magnets.

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

• They do not lose strength, even after around 10 years – the decrease in lifting capacity is only ~1% (theoretically),
• Magnets perfectly defend themselves against demagnetization caused by ambient magnetic noise,
• A magnet with a metallic silver surface looks better,
• Magnetic induction on the top side of the magnet is extremely intense,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to versatility in forming and the capacity to adapt to complex applications,
• Versatile presence in modern technologies – they are used in mass storage devices, electromotive mechanisms, medical equipment, also multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which enables their usage in miniature devices

Cons of neodymium magnets: weaknesses and usage proposals

• They are fragile upon too strong impacts. To avoid cracks, it is worth protecting magnets in special housings. Such protection not only shields the magnet but also increases its resistance to damage
• Neodymium magnets lose their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation as well as corrosion.
• Limited possibility of making threads in the magnet and complicated shapes - preferred is casing - magnet mounting.
• Health risk to health – tiny shards of magnets can be dangerous, in case of ingestion, which gains importance in the aspect of protecting the youngest. It is also worth noting that small elements of these magnets can be problematic in diagnostics medical when they are in the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Magnetic strength at its maximum – what contributes to it?

The lifting capacity listed is a result of laboratory testing conducted under standard conditions:

• on a block made of structural steel, optimally conducting the magnetic flux
• possessing a thickness of minimum 10 mm to ensure full flux closure
• with a plane perfectly flat
• with zero gap (without coatings)
• under perpendicular force vector (90-degree angle)
• at ambient temperature approx. 20 degrees Celsius

Impact of factors on magnetic holding capacity in practice

In practice, the actual holding force is determined by several key aspects, ranked from crucial:

• Air gap (between the magnet and the plate), since even a microscopic clearance (e.g. 0.5 mm) can cause a drastic drop in force by up to 50% (this also applies to paint, rust or dirt).
• Loading method – catalog parameter refers to detachment vertically. When attempting to slide, the magnet exhibits significantly lower power (often approx. 20-30% of nominal force).
• Wall thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of generating force.
• Metal type – different alloys attracts identically. High carbon content worsen the attraction effect.
• Smoothness – full contact is possible only on smooth steel. Rough texture create air cushions, reducing force.
• Thermal factor – high temperature reduces pulling force. Too high temperature can permanently damage the magnet.

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under shearing force the holding force is lower. Additionally, even a minimal clearance {between} the magnet and the plate reduces the lifting capacity.