UMC 42x7/4x9 / N38 - cylindrical magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their magnetism, even after around 10 years – the reduction of strength is only ~1% (according to tests),
• They protect against demagnetization induced by ambient magnetic influence remarkably well,
• By applying a bright layer of silver, the element gains a clean look,
• The outer field strength of the magnet shows elevated magnetic properties,
• 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 personalized design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Significant impact in cutting-edge sectors – they are used in hard drives, electromechanical systems, medical equipment as well as technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which makes them useful in small systems

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage and additionally increases its overall robustness,
• 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,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of rubber for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing threads directly in the magnet,
• Health risk from tiny pieces may arise, in case of ingestion, which is crucial in the context of child safety. It should also be noted that small elements from these assemblies might disrupt scanning if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, determined in the best circumstances, namely:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• at room temperature

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is conditioned by these factors, from crucial to less important:

• 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 was assessed with the use of a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, whereas under parallel forces the load capacity is reduced by as much as fivefold. Moreover, even a small distance {between} the magnet’s surface and the plate decreases the holding force.