SM 25x125 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• They have stable power, and over around 10 years their attraction force decreases symbolically – ~1% (in testing),
• They remain magnetized despite exposure to strong external fields,
• Because of the lustrous layer of silver, the component looks visually appealing,
• The outer field strength of the magnet shows elevated magnetic properties,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for custom shaping and adaptation to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Significant impact in advanced technical fields – they are utilized in computer drives, electric drives, clinical machines and sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to external force, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from damage , and at the same time enhances its overall strength,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on form). 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,
• Magnets exposed to damp air can oxidize. Therefore, for outdoor applications, we advise waterproof types made of non-metallic composites,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Health risk due to small fragments may arise, if ingested accidentally, which is important in the protection of children. It should also be noted that tiny components from these devices can interfere with diagnostics when ingested,
• Due to the price of neodymium, their cost is relatively high,

Maximum holding power of the magnet – what contributes to it?

The given lifting capacity of the magnet means the maximum lifting force, determined in a perfect environment, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Determinants of practical lifting force of a magnet

The lifting capacity of a magnet is determined by in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, as 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 was determined with the use of a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, however under attempts to slide the magnet the holding force is lower. Additionally, even a minimal clearance {between} the magnet and the plate lowers the holding force.