MW 40x30 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• Their magnetic field remains stable, and after approximately 10 years, it drops only by ~1% (theoretically),
• They remain magnetized despite exposure to magnetic noise,
• Because of the reflective layer of gold, the component looks visually appealing,
• Magnetic induction on the surface of these magnets is notably high,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for precise shaping and customization to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Important function in new technology industries – they serve a purpose in data storage devices, rotating machines, diagnostic apparatus or even technologically developed systems,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to mechanical hits, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks and additionally increases its overall robustness,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent deterioration 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,
• Magnets exposed to damp air can rust. Therefore, for outdoor applications, we recommend waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing holes directly in the magnet,
• Safety concern linked to microscopic shards may arise, if ingested accidentally, which is significant in the family environments. Furthermore, small elements from these assemblies can hinder health screening if inside the body,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Best holding force of the magnet in ideal parameters – what affects it?

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

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with no separation
• in a perpendicular direction of force
• at room temperature

Practical lifting capacity: influencing factors

Practical lifting force is dependent on factors, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, since 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 carried out on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, however under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Moreover, even a small distance {between} the magnet’s surface and the plate reduces the load capacity.