MW 5x10 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior magnetism, neodymium magnets have these key benefits:

• They virtually do not lose strength, because even after 10 years, the performance loss is only ~1% (in laboratory conditions),
• They show strong resistance to demagnetization from external field exposure,
• In other words, due to the shiny nickel coating, the magnet obtains an aesthetic appearance,
• The outer field strength of the magnet shows advanced magnetic properties,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• Thanks to the flexibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their application range,
• Important function in new technology industries – they are utilized in computer drives, electric motors, diagnostic apparatus along with sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to shocks, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage and reinforces its overall strength,
• High temperatures may significantly reduce the magnetic power 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 wet conditions can corrode. 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,
• Possible threat from tiny pieces may arise, especially if swallowed, which is significant in the family environments. Furthermore, small elements from these devices may interfere with diagnostics after being swallowed,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

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

The given lifting capacity of the magnet represents the maximum lifting force, calculated in a perfect environment, namely:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

Key elements affecting lifting force

The lifting capacity of a magnet depends on in practice the following factors, according to their importance:

• 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 was assessed by applying a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, in contrast under parallel forces the holding force is lower. Additionally, even a minimal clearance {between} the magnet’s surface and the plate reduces the holding force.