SM 32x250 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• They have constant strength, and over more than ten years their attraction force decreases symbolically – ~1% (according to theory),
• They show exceptional resistance to demagnetization from external field exposure,
• Thanks to the shiny finish and silver coating, they have an visually attractive appearance,
• Magnetic induction on the surface of these magnets is very strong,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• With the option for tailored forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Significant impact in cutting-edge sectors – they find application in HDDs, electric drives, medical equipment as well as high-tech tools,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of magnetic elements:

• They may fracture when subjected to a strong impact. If the magnets are exposed to physical collisions, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture and reinforces its overall durability,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on size). 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,
• Magnets exposed to damp air can degrade. Therefore, for outdoor applications, we advise waterproof types made of coated materials,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Possible threat related to magnet particles may arise, especially if swallowed, which is important in the health of young users. Moreover, tiny components from these assemblies might hinder health screening once in the system,
• Due to expensive raw materials, their cost is above average,

Highest magnetic holding force – what it depends on?

The given lifting capacity of the magnet corresponds to the maximum lifting force, calculated under optimal conditions, that is:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• 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 conditioned by the following aspects, in descending order of importance:

• 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 with the use of a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular detachment force, whereas under shearing force the holding force is lower. In addition, even a small distance {between} the magnet and the plate lowers the holding force.