SM 32x200 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They virtually do not lose power, because even after 10 years, the decline in efficiency is only ~1% (according to literature),
• They remain magnetized despite exposure to magnetic noise,
• By applying a shiny layer of gold, the element gains a modern look,
• The outer field strength of the magnet shows remarkable magnetic properties,
• With the right combination of compounds, they reach significant thermal stability, enabling operation at or above 230°C (depending on the design),
• With the option for fine forming and personalized design, these magnets can be produced in multiple shapes and sizes, greatly improving application potential,
• Significant impact in cutting-edge sectors – they are used in hard drives, electromechanical systems, diagnostic apparatus as well as technologically developed systems,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to shocks, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage and additionally increases its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent loss 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 – during outdoor use, we recommend using waterproof magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is not feasible,
• Possible threat related to magnet particles may arise, in case of ingestion, which is important in the family environments. Furthermore, miniature parts from these products have the potential to hinder health screening after being swallowed,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Highest magnetic holding force – what contributes to it?

The given strength of the magnet means the optimal strength, assessed in the best circumstances, specifically:

• with mild steel, serving as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Lifting capacity in practice – influencing factors

In practice, the holding capacity of a magnet is affected 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.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Moreover, even a small distance {between} the magnet’s surface and the plate decreases the lifting capacity.