BM 550x180x70 [4x M8] - magnetic beam

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They have unchanged lifting capacity, and over nearly ten years their performance decreases symbolically – ~1% (in testing),
• They show exceptional resistance to demagnetization from external field exposure,
• The use of a polished nickel surface provides a refined finish,
• The outer field strength of the magnet shows advanced magnetic properties,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• Thanks to the freedom in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their functional possibilities,
• Significant impact in cutting-edge sectors – they are used in hard drives, electromechanical systems, diagnostic apparatus as well as technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They may fracture when subjected to a powerful impact. If the magnets are exposed to shocks, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and increases its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent loss 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 moisture can oxidize. Therefore, for outdoor applications, we advise waterproof types made of plastic,
• Limited ability to create threads in the magnet – the use of a mechanical support is recommended,
• Safety concern linked to microscopic shards may arise, in case of ingestion, which is notable in the context of child safety. Moreover, tiny components from these magnets have the potential to disrupt scanning if inside the body,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which may limit large-scale applications

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given strength of the magnet corresponds to the optimal strength, assessed under optimal conditions, specifically:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Determinants of lifting force in real conditions

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

• 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.

* Lifting capacity was measured with the use of a polished steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, however under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.