MW 33x10 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their strength remains stable, and after around ten years, it drops only by ~1% (theoretically),
• They show strong resistance to demagnetization from external field exposure,
• The use of a decorative gold surface provides a eye-catching finish,
• They have exceptional magnetic induction on the surface of the magnet,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• With the option for tailored forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving design adaptation,
• Important function in cutting-edge sectors – they serve a purpose in data storage devices, electric motors, diagnostic apparatus or even technologically developed systems,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to physical collisions, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture and additionally enhances its overall resistance,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to humidity can corrode. Therefore, for outdoor applications, it's best to use waterproof types made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing fine shapes directly in the magnet,
• Potential hazard from tiny pieces may arise, when consumed by mistake, which is crucial in the protection of children. Moreover, miniature parts from these assemblies might complicate medical imaging after being swallowed,
• In cases of large-volume purchasing, neodymium magnet cost may not be economically viable,

Maximum lifting force for a neodymium magnet – what it depends on?

The given strength of the magnet means the optimal strength, calculated in the best circumstances, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a refined outer layer
• with no separation
• with vertical force applied
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet is determined by in practice the following factors, ordered from most important to least significant:

• 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.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the load capacity is reduced by as much as 75%. In addition, even a slight gap {between} the magnet and the plate reduces the load capacity.