SM 32x500 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their stability, neodymium magnets are valued for these benefits:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (based on calculations),
• They are highly resistant to demagnetization caused by external field interference,
• Thanks to the shiny finish and nickel coating, they have an aesthetic appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for customized forming and targeted design, these magnets can be produced in various shapes and sizes, greatly improving design adaptation,
• Key role in modern technologies – they are used in hard drives, electric drives, diagnostic apparatus and other advanced devices,
• Compactness – despite their small size, they deliver powerful magnetism, 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 external force, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks and enhances its overall strength,
• They lose magnetic force at extreme temperatures. Most neodymium magnets experience permanent reduction in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to moisture can oxidize. Therefore, for outdoor applications, we suggest waterproof types made of rubber,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is restricted,
• Safety concern from tiny pieces may arise, when consumed by mistake, which is notable in the family environments. It should also be noted that tiny components from these magnets might interfere with diagnostics if inside the body,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which may limit large-scale applications

Maximum lifting force for a neodymium magnet – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, calculated under optimal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a smooth surface
• with zero air gap
• in a perpendicular direction of force
• under standard ambient temperature

What influences lifting capacity in practice

Practical lifting force is determined by elements, by priority:

• 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 measured with the use of a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, whereas under shearing force the load capacity is reduced by as much as 75%. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.