SM 25x125 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional magnetic power, neodymium magnets offer the following advantages:

• They virtually do not lose strength, because even after 10 years, the decline in efficiency is only ~1% (in laboratory conditions),
• They show superior resistance to demagnetization from external magnetic fields,
• The use of a mirror-like silver surface provides a eye-catching finish,
• Magnetic induction on the surface of these magnets is notably high,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• Thanks to the flexibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which broadens their application range,
• Wide application in new technology industries – they are utilized in computer drives, electric drives, clinical machines or even high-tech tools,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to external force, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and additionally reinforces its overall robustness,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s profile). 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 moisture-resistant magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is difficult,
• Health risk linked to microscopic shards may arise, when consumed by mistake, which is significant in the context of child safety. It should also be noted that minuscule fragments from these magnets can interfere with diagnostics once in the system,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which may limit large-scale applications

Maximum lifting capacity of the magnet – what contributes to it?

The given lifting capacity of the magnet represents the maximum lifting force, calculated in a perfect environment, that is:

• with mild steel, used as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a refined outer layer
• with zero air gap
• in a perpendicular direction of force
• at room temperature

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is affected by these factors, arranged from the most important to the least relevant:

• 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.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet and the plate lowers the lifting capacity.