MW 25x5 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their power remains stable, and after around 10 years, it drops only by ~1% (according to research),
• They show superior resistance to demagnetization from external magnetic fields,
• Thanks to the polished finish and gold coating, they have an aesthetic appearance,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• Thanks to their exceptional 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 diverse shapes and sizes, which broadens their functional possibilities,
• Key role in modern technologies – they find application in data storage devices, electromechanical systems, clinical machines as well as high-tech tools,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, with minimal size,

Disadvantages of neodymium magnets:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to shocks, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and additionally increases its overall durability,
• Magnets lose magnetic efficiency when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is common to use sealed magnets made of synthetic coating for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing holes directly in the magnet,
• Potential hazard linked to microscopic shards may arise, when consumed by mistake, which is important in the health of young users. It should also be noted that minuscule fragments from these magnets might complicate medical imaging after being swallowed,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Maximum holding power of the magnet – what contributes to it?

The given strength of the magnet means the optimal strength, calculated under optimal conditions, that is:

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

Key elements affecting lifting force

In practice, the holding capacity of a magnet is affected by these factors, from crucial to less important:

• Air gap between the magnet and the plate, because 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 by applying a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.