SM 32x300 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their remarkable pulling force, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over nearly ten years their attraction force decreases symbolically – ~1% (according to theory),
• They show strong resistance to demagnetization from external magnetic fields,
• Because of the brilliant layer of gold, the component looks aesthetically refined,
• Magnetic induction on the surface of these magnets is impressively powerful,
• Thanks to their exceptional temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for fine forming and targeted design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Key role in cutting-edge sectors – they are utilized in computer drives, electromechanical systems, diagnostic apparatus as well as high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in compact dimensions, which makes them useful in compact constructions

Disadvantages of rare earth magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to physical collisions, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from damage and additionally increases its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent loss in performance (depending on shape). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of synthetic coating for outdoor use,
• Limited ability to create complex details in the magnet – the use of a external casing is recommended,
• Safety concern linked to microscopic shards may arise, when consumed by mistake, which is notable in the context of child safety. Furthermore, small elements from these magnets might hinder health screening after being swallowed,
• Due to the price of neodymium, their cost is relatively high,

Highest magnetic holding force – what affects it?

The given pulling force of the magnet represents the maximum force, determined in ideal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

What influences lifting capacity in practice

In practice, the holding capacity of a magnet is conditioned by the following aspects, arranged from the most important to the least relevant:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) can cause a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Lifting capacity testing was conducted on a smooth plate of optimal thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the lifting capacity is smaller. In addition, even a slight gap {between} the magnet and the plate reduces the lifting capacity.