MW 20x5 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets.

Apart from their superior magnetic energy, neodymium magnets have these key benefits:

• They do not lose power, even during around ten years – the decrease in power is only ~1% (based on measurements),
• They retain their magnetic properties even under strong external field,
• By applying a lustrous layer of gold, the element acquires an aesthetic look,
• The surface of neodymium magnets generates a maximum magnetic field – this is one of their assets,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can work (depending on the shape) even at a temperature of 230°C or more...
• Thanks to flexibility in designing and the capacity to customize to specific needs,
• Versatile presence in modern technologies – they are utilized in mass storage devices, electric motors, diagnostic systems, as well as multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in tiny dimensions, which allows their use in miniature devices

Drawbacks and weaknesses of neodymium magnets: weaknesses and usage proposals

• Brittleness is one of their disadvantages. Upon strong impact they can break. We recommend keeping them in a strong case, which not only secures them against impacts but also raises their 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 advise using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• Limited ability of creating nuts in the magnet and complex shapes - recommended is cover - magnetic holder.
• Health risk to health – tiny shards of magnets pose a threat, if swallowed, which becomes key 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.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Magnetic strength at its maximum – what affects it?

The load parameter shown represents the maximum value, measured under optimal environment, namely:

• using a plate made of low-carbon steel, functioning as a magnetic yoke
• whose transverse dimension equals approx. 10 mm
• with a plane free of scratches
• under conditions of ideal adhesion (metal-to-metal)
• during pulling in a direction perpendicular to the mounting surface
• at temperature approx. 20 degrees Celsius

Lifting capacity in practice – influencing factors

It is worth knowing that the magnet holding will differ depending on elements below, starting with the most relevant:

• Space between magnet and steel – even a fraction of a millimeter of separation (caused e.g. by varnish or unevenness) diminishes the pulling force, often by half at just 0.5 mm.
• Force direction – declared lifting capacity refers to pulling vertically. When slipping, the magnet holds significantly lower power (often approx. 20-30% of nominal force).
• Element thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Material type – ideal substrate is high-permeability steel. Stainless steels may have worse magnetic properties.
• Smoothness – full contact is obtained only on polished steel. Any scratches and bumps create air cushions, reducing force.
• Heat – NdFeB sinters have a negative temperature coefficient. At higher temperatures they lose power, and in frost gain strength (up to a certain limit).

* Lifting capacity testing was carried out on plates with a smooth surface of optimal thickness, under perpendicular forces, in contrast under shearing force the holding force is lower. Moreover, even a small distance {between} the magnet’s surface and the plate reduces the holding force.