MPL 40x20x4x2[7/3.5] / N38 - lamellar magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional field intensity, neodymium magnets offer the following advantages:

• They virtually do not lose strength, because even after 10 years, the decline in efficiency is only ~1% (according to literature),
• They protect against demagnetization induced by external magnetic influence remarkably well,
• By applying a shiny layer of nickel, the element gains a sleek look,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• Thanks to the possibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which expands their functional possibilities,
• Wide application in new technology industries – they are used in HDDs, electric drives, diagnostic apparatus or even other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which allows for use in small systems

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to physical collisions, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture while also enhances its overall durability,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent deterioration 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,
• Magnets exposed to wet conditions can degrade. Therefore, for outdoor applications, we suggest waterproof types made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing threads directly in the magnet,
• Health risk linked to microscopic shards may arise, especially if swallowed, which is important in the health of young users. It should also be noted that miniature parts from these assemblies can complicate medical imaging when ingested,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Optimal lifting capacity of a neodymium magnet – what it depends on?

The given strength of the magnet represents the optimal strength, determined in ideal conditions, specifically:

• with the use of low-carbon steel plate acting as a magnetic yoke
• 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

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is conditioned by these factors, arranged from the most important to the least relevant:

• Air gap between the magnet and the plate, since 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 smooth steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, whereas under parallel forces the load capacity is reduced by as much as 75%. Moreover, even a small distance {between} the magnet and the plate decreases the load capacity.