SM 32x375 [2xM8] / N42 - magnetic separator

Pros as well as cons of rare earth magnets.

Besides their exceptional pulling force, neodymium magnets offer the following advantages:

• They do not lose magnetism, even over nearly 10 years – the drop in lifting capacity is only ~1% (theoretically),
• Neodymium magnets prove to be extremely resistant to loss of magnetic properties caused by external field sources,
• A magnet with a shiny nickel surface has an effective appearance,
• The surface of neodymium magnets generates a powerful magnetic field – this is one of their assets,
• Thanks to resistance to high temperature, they are able to function (depending on the form) even at temperatures up to 230°C and higher...
• Thanks to flexibility in shaping and the ability to customize to complex applications,
• Key role in advanced technology sectors – they are used in mass storage devices, electromotive mechanisms, medical devices, and other advanced devices.
• Thanks to their power density, small magnets offer high operating force, with minimal size,

Cons of neodymium magnets: tips and applications.

• Brittleness is one of their disadvantages. Upon intense impact they can fracture. We recommend keeping them in a special holder, which not only protects them against impacts but also increases their durability
• NdFeB magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of power (a factor is the shape and 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
• When exposed to humidity, magnets usually rust. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• Limited ability of making threads in the magnet and complex forms - preferred is casing - magnetic holder.
• Possible danger resulting from small fragments of magnets pose a threat, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. Furthermore, small elements of these devices can be problematic in diagnostics medical in case of swallowing.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum lifting force for a neodymium magnet – what contributes to it?

The force parameter is a result of laboratory testing performed under specific, ideal conditions:

• with the contact of a yoke made of special test steel, ensuring maximum field concentration
• whose thickness reaches at least 10 mm
• characterized by even structure
• with total lack of distance (without impurities)
• for force acting at a right angle (pull-off, not shear)
• in temp. approx. 20°C

Lifting capacity in practice – influencing factors

It is worth knowing that the working load may be lower influenced by elements below, in order of importance:

• Gap (betwixt the magnet and the plate), since even a microscopic distance (e.g. 0.5 mm) can cause a decrease in lifting capacity by up to 50% (this also applies to paint, rust or debris).
• Direction of force – maximum parameter is obtained only during pulling at a 90° angle. The force required to slide of the magnet along the surface is usually many times lower (approx. 1/5 of the lifting capacity).
• Plate thickness – too thin sheet does not accept the full field, causing part of the power to be escaped into the air.
• Metal type – different alloys reacts the same. Alloy additives worsen the attraction effect.
• Smoothness – full contact is obtained only on polished steel. Rough texture reduce the real contact area, weakening the magnet.
• Temperature influence – hot environment reduces magnetic field. Too high temperature can permanently damage the magnet.

* Lifting capacity was determined using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, whereas under parallel forces the load capacity is reduced by as much as 75%. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the lifting capacity.