SM 18x100 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have stable power, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• They are extremely resistant to demagnetization caused by external field interference,
• In other words, due to the shiny nickel coating, the magnet obtains an aesthetic appearance,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for tailored forming and personalized design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Important function in new technology industries – they serve a purpose in HDDs, electric motors, diagnostic apparatus and technologically developed systems,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a powerful impact. If the magnets are exposed to physical collisions, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage while also increases its overall durability,
• They lose magnetic force at extreme temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a moist environment – during outdoor use, we recommend using sealed magnets, such as those made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing complex structures directly in the magnet,
• Possible threat linked to microscopic shards may arise, when consumed by mistake, which is important in the protection of children. It should also be noted that miniature parts from these magnets can interfere with diagnostics once in the system,
• Due to the price of neodymium, their cost is above average,

Best holding force of the magnet in ideal parameters – what contributes to it?

The given holding capacity of the magnet means the highest holding force, calculated in the best circumstances, that is:

• with mild steel, used as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• with vertical force applied
• under standard ambient temperature

Key elements affecting lifting force

In practice, the holding capacity of a magnet is affected by the following aspects, in descending order of importance:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) causes 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 carried out on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the holding force is lower. Additionally, even a minimal clearance {between} the magnet’s surface and the plate decreases the holding force.