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

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their magnetism, even after around 10 years – the loss of lifting capacity is only ~1% (theoretically),
• They show strong resistance to demagnetization from outside magnetic sources,
• By applying a shiny layer of silver, the element gains a sleek look,
• They possess intense magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• The ability for accurate shaping and adjustment to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which amplifies their functionality across industries,
• Wide application in modern technologies – they serve a purpose in computer drives, electric motors, clinical machines or even sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which makes them useful in miniature devices

Disadvantages of magnetic elements:

• They may fracture when subjected to a strong impact. If the magnets are exposed to shocks, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture and enhances its overall strength,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on height). 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 synthetic coating for outdoor use,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is restricted,
• Safety concern linked to microscopic shards may arise, if ingested accidentally, which is crucial in the protection of children. Additionally, minuscule fragments from these magnets can interfere with diagnostics 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 contributes to it?

The given pulling force of the magnet corresponds to the maximum force, measured in the best circumstances, namely:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Determinants of practical lifting force of a magnet

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

• 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 a perpendicular force was applied, whereas under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet’s surface and the plate decreases the load capacity.