UMP 79x50 [M8] GW - search holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their magnetism, even after nearly ten years – the decrease of lifting capacity is only ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is notable,
• Because of the lustrous layer of silver, the component looks aesthetically refined,
• They possess strong magnetic force measurable at the magnet’s surface,
• Thanks to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• Thanks to the flexibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which increases their functional possibilities,
• Important function in advanced technical fields – they are utilized in computer drives, electric motors, medical equipment along with sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in compact dimensions, which makes them useful in compact constructions

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to physical collisions, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage while also enhances its overall durability,
• High temperatures may significantly reduce the strength 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,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of synthetic coating for outdoor use,
• Limited ability to create internal holes in the magnet – the use of a external casing is recommended,
• Possible threat due to small fragments may arise, when consumed by mistake, which is crucial in the context of child safety. Additionally, tiny components from these magnets have the potential to complicate medical imaging if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum lifting force for a neodymium magnet – what contributes to it?

The given pulling force of the magnet means the maximum force, determined in the best circumstances, that is:

• with mild steel, serving as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Lifting capacity in practice – influencing factors

In practice, the holding capacity of a magnet is conditioned by the following aspects, in descending order of importance:

• 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.

* Lifting capacity was determined using a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular detachment force, however under shearing force the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.