SMZR 25x250 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their durability, neodymium magnets are valued for these benefits:

• They retain their full power for nearly ten years – the drop is just ~1% (according to analyses),
• They are extremely resistant to demagnetization caused by external field interference,
• By applying a reflective layer of nickel, the element gains a modern look,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the form),
• 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 usage potential,
• Wide application in cutting-edge sectors – they find application in computer drives, rotating machines, healthcare devices along with technologically developed systems,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to shocks, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage while also reinforces its overall robustness,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent loss 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 humidity can degrade. Therefore, for outdoor applications, we advise waterproof types made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Safety concern linked to microscopic shards may arise, especially if swallowed, which is significant in the health of young users. Furthermore, small elements from these devices may interfere with diagnostics after being swallowed,
• Due to the price of neodymium, their cost is above average,

Optimal lifting capacity of a neodymium magnet – what affects it?

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

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a polished side
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Key elements affecting lifting force

The lifting capacity of a magnet is determined by in practice key elements, ordered from most important to least 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.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the load capacity is reduced by as much as fivefold. Additionally, even a small distance {between} the magnet and the plate lowers the load capacity.