SM 25x175 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their stability, 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 strong external fields,
• The use of a polished silver surface provides a smooth finish,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• With the right combination of materials, they reach increased thermal stability, enabling operation at or above 230°C (depending on the form),
• Thanks to the possibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which increases their usage potential,
• Important function in advanced technical fields – they serve a purpose in computer drives, electric motors, clinical machines as well as other advanced devices,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to shocks, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage while also enhances its overall durability,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a wet environment, especially when used outside, we recommend using encapsulated magnets, such as those made of polymer,
• Limited ability to create complex details in the magnet – the use of a external casing is recommended,
• Safety concern related to magnet particles may arise, when consumed by mistake, which is significant in the protection of children. Additionally, tiny components from these products can interfere with diagnostics if inside the body,
• Due to a complex production process, their cost is above average,

Maximum holding power of the magnet – what it depends on?

The given holding capacity of the magnet means the highest holding force, measured under optimal conditions, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• with vertical force applied
• under standard ambient temperature

Practical aspects of lifting capacity – factors

In practice, the holding capacity of a magnet is conditioned by these factors, 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.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet’s surface and the plate decreases the holding force.