MW 2x4 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their even over around 10 years – the decrease of power is only ~1% (based on measurements),
• They protect against demagnetization induced by surrounding magnetic influence effectively,
• By applying a bright layer of nickel, the element gains a modern look,
• Magnetic induction on the surface of these magnets is notably high,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• With the option for tailored forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving design adaptation,
• Significant impact in cutting-edge sectors – they find application in computer drives, electric drives, medical equipment or even other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which makes them useful in compact constructions

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to physical collisions, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time reinforces its overall robustness,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent decline 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,
• They rust in a damp environment – during outdoor use, we recommend using sealed magnets, such as those made of non-metallic materials,
• Limited ability to create precision features in the magnet – the use of a external casing is recommended,
• Possible threat related to magnet particles may arise, if ingested accidentally, which is notable in the family environments. Additionally, minuscule fragments from these magnets might interfere with diagnostics when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

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

The given holding capacity of the magnet corresponds to the highest holding force, measured under optimal conditions, namely:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• in a perpendicular direction of force
• in normal thermal conditions

Determinants of practical lifting force of a magnet

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• 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.

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Moreover, even a slight gap {between} the magnet and the plate lowers the lifting capacity.