MW 8x20 / N38 - cylindrical magnet

Strengths as well as weaknesses of neodymium magnets.

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

• Their strength is maintained, and after approximately 10 years it decreases only by ~1% (according to research),
• They retain their magnetic properties even under strong external field,
• In other words, due to the reflective surface of gold, the element is aesthetically pleasing,
• Magnetic induction on the top side of the magnet turns out to be extremely intense,
• Thanks to resistance to high temperature, they are able to function (depending on the shape) even at temperatures up to 230°C and higher...
• Thanks to freedom in shaping and the ability to adapt to specific needs,
• Huge importance in innovative solutions – they serve a role in magnetic memories, brushless drives, diagnostic systems, and industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which enables their usage in miniature devices

Disadvantages of NdFeB magnets:

• At very strong impacts they can crack, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• When exposed to high temperature, neodymium magnets experience a drop in force. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They rust in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited ability of producing threads in the magnet and complex forms - preferred is casing - magnetic holder.
• Potential hazard to health – tiny shards of magnets pose a threat, in case of ingestion, which is particularly important in the context of child health protection. It is also worth noting that tiny parts of these products can be problematic in diagnostics medical after entering the body.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

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

The declared magnet strength refers to the limit force, measured under optimal environment, meaning:

• with the contact of a yoke made of special test steel, ensuring full magnetic saturation
• with a thickness of at least 10 mm
• with an ideally smooth contact surface
• with zero gap (no coatings)
• under vertical force vector (90-degree angle)
• at standard ambient temperature

Impact of factors on magnetic holding capacity in practice

Holding efficiency is influenced by specific conditions, such as (from most important):

• Gap between surfaces – even a fraction of a millimeter of separation (caused e.g. by varnish or dirt) drastically reduces the pulling force, often by half at just 0.5 mm.
• Load vector – maximum parameter is obtained only during perpendicular pulling. The shear force of the magnet along the surface is typically several times lower (approx. 1/5 of the lifting capacity).
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of generating force.
• Steel grade – the best choice is high-permeability steel. Cast iron may generate lower lifting capacity.
• Smoothness – full contact is possible only on polished steel. Rough texture reduce the real contact area, reducing force.
• Temperature influence – hot environment weakens pulling force. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.