MPL 20x8x4 / N38 - lamellar magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their immense magnetic power, neodymium magnets offer the following advantages:

• They do not lose their magnetism, even after nearly ten years – the loss of lifting capacity is only ~1% (based on measurements),
• Their ability to resist magnetic interference from external fields is notable,
• Thanks to the glossy finish and silver coating, they have an elegant appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• With the right combination of materials, they reach significant thermal stability, enabling operation at or above 230°C (depending on the structure),
• With the option for tailored forming and personalized design, these magnets can be produced in multiple shapes and sizes, greatly improving engineering flexibility,
• Significant impact in cutting-edge sectors – they are used in computer drives, electric drives, clinical machines and technologically developed systems,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of NdFeB magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to external force, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage and additionally reinforces its overall strength,
• High temperatures may significantly reduce the strength 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 humid environment – during outdoor use, we recommend using waterproof magnets, such as those made of plastic,
• Limited ability to create complex details in the magnet – the use of a housing is recommended,
• Health risk related to magnet particles may arise, especially if swallowed, which is crucial in the health of young users. Furthermore, minuscule fragments from these devices have the potential to hinder health screening after being swallowed,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Magnetic strength at its maximum – what affects it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, measured under optimal conditions, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• under standard ambient temperature

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet depends on in practice key elements, ordered from most important to least significant:

• 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 checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under shearing force the holding force is lower. In addition, even a slight gap {between} the magnet’s surface and the plate lowers the holding force.