SM 18x300 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of rare earth magnets.

Besides their immense strength, neodymium magnets offer the following advantages:

• They have stable power, and over around 10 years their performance decreases symbolically – ~1% (in testing),
• Magnets very well protect themselves against demagnetization caused by ambient magnetic noise,
• The use of an elegant layer of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Magnetic induction on the surface of the magnet turns out to be extremely intense,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Thanks to versatility in designing and the capacity to adapt to unusual requirements,
• Huge importance in future technologies – they find application in mass storage devices, electric drive systems, diagnostic systems, as well as modern systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in tiny dimensions, which makes them useful in compact constructions

Disadvantages of neodymium magnets:

• Brittleness is one of their disadvantages. Upon intense impact they can fracture. We advise keeping them in a strong case, which not only protects them against impacts but also increases their durability
• 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
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material immune to moisture, in case of application outdoors
• We recommend cover - magnetic holder, due to difficulties in creating threads inside the magnet and complex shapes.
• Potential hazard resulting from small fragments of magnets can be dangerous, when accidentally swallowed, which is particularly important in the context of child safety. It is also worth noting that small components of these devices can disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which hinders application in large quantities

Optimal lifting capacity of a neodymium magnet – what affects it?

The force parameter is a theoretical maximum value performed under specific, ideal conditions:

• with the use of a sheet made of low-carbon steel, guaranteeing full magnetic saturation
• with a thickness of at least 10 mm
• characterized by smoothness
• without the slightest air gap between the magnet and steel
• under vertical force direction (90-degree angle)
• at conditions approx. 20°C

Practical aspects of lifting capacity – factors

Real force is affected by specific conditions, including (from priority):

• Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by varnish or dirt) drastically reduces the pulling force, often by half at just 0.5 mm.
• Pull-off angle – remember that the magnet holds strongest perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the nominal value.
• Element thickness – for full efficiency, the steel must be adequately massive. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Material type – the best choice is high-permeability steel. Cast iron may generate lower lifting capacity.
• Surface quality – the more even the surface, the better the adhesion and stronger the hold. Roughness acts like micro-gaps.
• Operating temperature – neodymium magnets have a negative temperature coefficient. When it is hot they lose power, and in frost they can be stronger (up to a certain limit).

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a slight gap {between} the magnet and the plate lowers the holding force.