SM 25x275 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior power, neodymium magnets have these key benefits:

• They virtually do not lose strength, because even after ten years, the performance loss is only ~1% (based on calculations),
• They are very resistant to demagnetization caused by external field interference,
• In other words, due to the metallic silver coating, the magnet obtains an professional appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• The ability for precise shaping or adaptation to individual needs – neodymium magnets can be manufactured in many forms and dimensions, which extends the scope of their use cases,
• Significant impact in advanced technical fields – they are used in data storage devices, electric drives, medical equipment as well as other advanced devices,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are fragile when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and additionally reinforces its overall resistance,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). 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 wet environment. If exposed to rain, we recommend using moisture-resistant magnets, such as those made of non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is not feasible,
• Safety concern related to magnet particles may arise, in case of ingestion, which is significant in the protection of children. Additionally, tiny components from these devices have the potential to complicate medical imaging once in the system,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which may limit large-scale applications

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given pulling force of the magnet means the maximum force, calculated under optimal conditions, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

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, 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 was determined using a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a minimal clearance {between} the magnet’s surface and the plate lowers the load capacity.