SM 25x325 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their strong holding force, neodymium magnets have these key benefits:

• Their magnetic field is durable, and after approximately ten years, it drops only by ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is among the best,
• In other words, due to the shiny nickel coating, the magnet obtains an stylish appearance,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• Thanks to their exceptional temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• Thanks to the possibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in different geometries, which increases their application range,
• Significant impact in modern technologies – they serve a purpose in hard drives, electric drives, clinical machines and sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of neodymium magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to physical collisions, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and additionally enhances its overall robustness,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on size). 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,
• They rust in a moist environment. For outdoor use, we recommend using encapsulated magnets, such as those made of rubber,
• Limited ability to create precision features in the magnet – the use of a mechanical support is recommended,
• Potential hazard related to magnet particles may arise, if ingested accidentally, which is notable in the protection of children. It should also be noted that tiny components from these products can interfere with diagnostics after being swallowed,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Detachment force of the magnet in optimal conditions – what affects it?

The given holding capacity of the magnet represents the highest holding force, measured in ideal conditions, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

What influences lifting capacity in practice

The lifting capacity of a magnet is determined by in practice the following factors, ordered from most important to least significant:

• Air gap between the magnet and the plate, since 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 a smooth plate of optimal thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the lifting capacity is smaller. In addition, even a small distance {between} the magnet’s surface and the plate decreases the load capacity.