BM 650x180x70 [4x M8] - magnetic beam

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their remarkable field intensity, neodymium magnets offer the following advantages:

• They do not lose their even during around 10 years – the reduction of strength is only ~1% (based on measurements),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• The use of a decorative silver surface provides a smooth finish,
• They have extremely strong magnetic induction on the surface of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to form),
• With the option for fine forming and targeted design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Important function in cutting-edge sectors – they are utilized in HDDs, electromechanical systems, diagnostic apparatus and other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to shocks, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage and enhances its overall durability,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on form). 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 damp environment – during outdoor use, we recommend using sealed magnets, such as those made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Possible threat linked to microscopic shards may arise, especially if swallowed, which is important in the protection of children. Furthermore, tiny components from these products might disrupt scanning once in the system,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which may limit large-scale applications

Maximum lifting capacity of the magnet – what it depends on?

The given strength of the magnet corresponds to the optimal strength, calculated in the best circumstances, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• of a thickness of at least 10 mm
• with a smooth surface
• with no separation
• with vertical force applied
• in normal thermal conditions

Practical lifting capacity: influencing factors

The lifting capacity of a magnet is influenced by in practice the following factors, according to their importance:

• Air gap between the magnet and the plate, as even a very small distance (e.g. 0.5 mm) can cause 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 testing was performed on plates with a smooth surface of optimal thickness, under perpendicular forces, however under parallel forces the load capacity is reduced by as much as fivefold. In addition, even a slight gap {between} the magnet and the plate decreases the lifting capacity.