AM ucho [M12] - magnetic accessories

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• Their power is maintained, and after around 10 years, it drops only by ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is impressive,
• Because of the lustrous layer of nickel, the component looks visually appealing,
• They have extremely strong magnetic induction on the surface of the magnet,
• 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),
• Thanks to the freedom in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in different geometries, which increases their usage potential,
• Important function in modern technologies – they are used in hard drives, electric drives, clinical machines and other advanced devices,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They can break when subjected to a heavy impact. If the magnets are exposed to shocks, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall durability,
• They lose power at increased temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the form and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a damp environment. For outdoor use, we recommend using sealed magnets, such as those made of non-metallic materials,
• Limited ability to create internal holes in the magnet – the use of a mechanical support is recommended,
• Health risk from tiny pieces may arise, in case of ingestion, which is significant in the health of young users. It should also be noted that small elements from these magnets may interfere with diagnostics once in the system,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Magnetic strength at its maximum – what it depends on?

The given strength of the magnet represents the optimal strength, determined under optimal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Determinants of practical lifting force of a magnet

In practice, the holding capacity of a magnet is affected 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.

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. Moreover, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.