MP 25x8x20 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• Their strength is durable, and after approximately 10 years, it drops only by ~1% (according to research),
• They show strong resistance to demagnetization from outside magnetic sources,
• By applying a shiny layer of nickel, the element gains a clean look,
• Magnetic induction on the surface of these magnets is impressively powerful,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for custom shaping and customization to custom needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Key role in modern technologies – they serve a purpose in computer drives, electromechanical systems, diagnostic apparatus as well as technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They are fragile 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 damage and reinforces its overall durability,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• 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 threads in the magnet – the use of a mechanical support is recommended,
• Potential hazard due to small fragments may arise, especially if swallowed, which is crucial in the context of child safety. Additionally, small elements from these magnets may disrupt scanning if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum holding power of the magnet – what it depends on?

The given holding capacity of the magnet represents the highest holding force, assessed under optimal conditions, namely:

• 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
• under perpendicular detachment force
• in normal thermal conditions

Lifting capacity in real conditions – factors

In practice, the holding capacity of a magnet is affected by these factors, 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 a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under shearing force the load capacity is reduced by as much as 5 times. Additionally, even a slight gap {between} the magnet and the plate lowers the lifting capacity.