MP 40x22x10 / N38 - ring magnet

Strengths and weaknesses of rare earth magnets.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They do not lose power, even over nearly ten years – the decrease in power is only ~1% (theoretically),
• They have excellent resistance to magnetism drop as a result of opposing magnetic fields,
• In other words, due to the glossy finish of gold, the element becomes visually attractive,
• They show high magnetic induction at the operating surface, making them more effective,
• 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 constructing and the capacity to modify to specific needs,
• Versatile presence in high-tech industry – they are commonly used in data components, electric drive systems, precision medical tools, as well as other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer high power in tiny dimensions, which allows their use in small systems

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can break. We recommend keeping them in a special holder, which not only protects them against impacts but also increases their durability
• When exposed to high temperature, neodymium magnets experience a drop in strength. Often, when the temperature exceeds 80°C, their strength 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
• Magnets exposed to a humid environment can rust. Therefore when using outdoors, we advise using waterproof magnets made of rubber, plastic or other material resistant to moisture
• We suggest casing - magnetic mechanism, due to difficulties in realizing threads inside the magnet and complex shapes.
• Health risk resulting from small fragments of magnets pose a threat, if swallowed, which becomes key in the aspect of protecting the youngest. Additionally, small elements of these magnets can disrupt the diagnostic process medical in case of swallowing.
• Due to expensive raw materials, their price exceeds standard values,

Magnetic strength at its maximum – what it depends on?

The specified lifting capacity refers to the maximum value, obtained under laboratory conditions, meaning:

• using a plate made of low-carbon steel, serving as a circuit closing element
• with a cross-section no less than 10 mm
• characterized by lack of roughness
• without the slightest clearance between the magnet and steel
• under axial force vector (90-degree angle)
• at standard ambient temperature

Impact of factors on magnetic holding capacity in practice

In real-world applications, the actual holding force is determined by a number of factors, ranked from most significant:

• Clearance – the presence of foreign body (paint, tape, air) interrupts the magnetic circuit, which lowers capacity steeply (even by 50% at 0.5 mm).
• Pull-off angle – note that the magnet holds strongest perpendicularly. Under shear forces, the holding force drops drastically, often to levels of 20-30% of the nominal value.
• Substrate thickness – for full efficiency, the steel must be adequately massive. Paper-thin metal restricts the lifting capacity (the magnet "punches through" it).
• Plate material – low-carbon steel gives the best results. Alloy steels decrease magnetic permeability and holding force.
• Base smoothness – the more even the surface, the larger the contact zone and stronger the hold. Roughness creates an air distance.
• Temperature – heating the magnet results in weakening of force. It is worth remembering the thermal limit for a given model.

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under parallel forces the load capacity is reduced by as much as 75%. In addition, even a small distance {between} the magnet and the plate lowers the lifting capacity.