MP 30x6x10 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They do not lose their strength approximately ten years – the reduction of lifting capacity is only ~1% (according to tests),
• They are extremely resistant to demagnetization caused by external magnetic fields,
• Thanks to the shiny finish and silver coating, they have an elegant appearance,
• They have very high magnetic induction on the surface of the magnet,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the form),
• The ability for custom shaping as well as customization to specific needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which extends the scope of their use cases,
• Wide application in advanced technical fields – they are utilized in computer drives, electric drives, diagnostic apparatus as well as high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in compact dimensions, which allows for use in compact constructions

Disadvantages of neodymium magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to external force, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture while also increases its overall durability,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent loss 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,
• Due to corrosion risk in humid conditions, it is advisable to use sealed magnets made of synthetic coating for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing complex structures directly in the magnet,
• Health risk linked to microscopic shards may arise, if ingested accidentally, which is significant in the protection of children. Moreover, miniature parts from these products might interfere with diagnostics if inside the body,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Detachment force of the magnet in optimal conditions – what affects it?

The given holding capacity of the magnet means the highest holding force, determined in the best circumstances, that is:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a smooth surface
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

Lifting capacity in practice – influencing factors

Practical lifting force is dependent on elements, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, as 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 checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet and the plate lowers the lifting capacity.