MW 8x10 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• Their magnetic field is durable, and after approximately 10 years, it drops only by ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is impressive,
• The use of a polished silver surface provides a refined finish,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to form),
• With the option for fine forming and targeted design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Significant impact in cutting-edge sectors – they are utilized in HDDs, rotating machines, diagnostic apparatus or even sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in tiny dimensions, which makes them ideal in miniature devices

Disadvantages of neodymium magnets:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to external force, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from cracks while also reinforces its overall robustness,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). 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. If exposed to rain, we recommend using sealed magnets, such as those made of non-metallic materials,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Safety concern linked to microscopic shards may arise, when consumed by mistake, which is important in the protection of children. Moreover, minuscule fragments from these magnets can disrupt scanning if inside the body,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Highest magnetic holding force – what affects it?

The given pulling force of the magnet corresponds to the maximum force, assessed under optimal conditions, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• in a perpendicular direction of force
• under standard ambient temperature

Practical aspects of lifting capacity – factors

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) 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 the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under shearing force the holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate reduces the lifting capacity.