MP 15x7/3.5x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their magnetic capacity, neodymium magnets provide the following advantages:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (according to literature),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• Because of the brilliant layer of silver, the component looks high-end,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• Thanks to the flexibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which broadens their functional possibilities,
• Significant impact in modern technologies – they serve a purpose in data storage devices, electric motors, healthcare devices as well as sophisticated instruments,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage while also reinforces its overall durability,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on form). 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 moist environment – during outdoor use, we recommend using waterproof magnets, such as those made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing complex structures directly in the magnet,
• Potential hazard due to small fragments may arise, especially if swallowed, which is significant in the family environments. It should also be noted that minuscule fragments from these products can disrupt scanning after being swallowed,
• Due to expensive raw materials, their cost is above average,

Maximum magnetic pulling force – what affects it?

The given strength of the magnet corresponds to the optimal strength, measured in the best circumstances, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

Practical lifting force is dependent on elements, by priority:

• Air gap between the magnet and the plate, since 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 a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under shearing force the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.