SMZR 25x100 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their magnetism, even after approximately ten years – the loss of strength is only ~1% (based on measurements),
• They protect against demagnetization induced by ambient magnetic influence remarkably well,
• By applying a bright layer of gold, the element gains a modern look,
• They possess strong magnetic force measurable at the magnet’s surface,
• 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),
• The ability for custom shaping or adjustment to individual needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which extends the scope of their use cases,
• Significant impact in new technology industries – they find application in computer drives, electric motors, diagnostic apparatus as well as sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to mechanical hits, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture , and at the same time strengthens its overall resistance,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on shape). 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 damp air can degrade. Therefore, for outdoor applications, we recommend waterproof types made of non-metallic composites,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing threads directly in the magnet,
• Safety concern related to magnet particles may arise, when consumed by mistake, which is notable in the health of young users. It should also be noted that minuscule fragments from these assemblies may interfere with diagnostics once in the system,
• In cases of mass production, neodymium magnet cost may be a barrier,

Breakaway strength of the magnet in ideal conditions – what it depends on?

The given strength of the magnet represents the optimal strength, measured in the best circumstances, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with no separation
• with vertical force applied
• in normal thermal conditions

Practical aspects of lifting capacity – factors

In practice, the holding capacity of a magnet is conditioned by the following aspects, from crucial to less important:

• Air gap between the magnet and the plate, as 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.

* Lifting capacity testing was performed on a smooth plate of suitable thickness, under a perpendicular pulling force, in contrast under shearing force the holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate lowers the load capacity.