MP 5x2.7/1.2x5 C / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their remarkable pulling force, neodymium magnets offer the following advantages:

• They virtually do not lose strength, because even after ten years, the performance loss is only ~1% (according to literature),
• They show exceptional resistance to demagnetization from external field exposure,
• By applying a shiny layer of silver, the element gains a modern look,
• They have exceptional magnetic induction on the surface of the magnet,
• Thanks to their high temperature resistance, they can operate (depending on the geometry) even at temperatures up to 230°C or more,
• The ability for custom shaping as well as customization to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which enhances their versatility in applications,
• Significant impact in cutting-edge sectors – they are used in HDDs, electric drives, healthcare devices and high-tech tools,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to external force, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture and additionally enhances its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening 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 common to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing holes directly in the magnet,
• Possible threat related to magnet particles may arise, if ingested accidentally, which is crucial in the protection of children. It should also be noted that tiny components from these devices can disrupt scanning after being swallowed,
• In cases of tight budgets, neodymium magnet cost may not be economically viable,

Maximum holding power of the magnet – what affects it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, determined in ideal conditions, specifically:

• with mild steel, used as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a polished side
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

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

• Air gap between the magnet and the plate, because 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 measured with the use of a polished steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, however under parallel forces the load capacity is reduced by as much as 75%. In addition, even a small distance {between} the magnet and the plate decreases the holding force.