SM 32x375 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They virtually do not lose power, because even after ten years, the decline in efficiency is only ~1% (in laboratory conditions),
• They show superior resistance to demagnetization from outside magnetic sources,
• In other words, due to the metallic silver coating, the magnet obtains an aesthetic appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• Thanks to the flexibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in various configurations, which broadens their functional possibilities,
• Wide application in cutting-edge sectors – they are used in computer drives, electric motors, healthcare devices or even sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which makes them useful in small systems

Disadvantages of rare earth magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to shocks, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from damage and strengthens its overall strength,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent loss in performance (depending on size). 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,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of plastic for outdoor use,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is restricted,
• Safety concern from tiny pieces may arise, in case of ingestion, which is notable in the protection of children. It should also be noted that minuscule fragments from these magnets may hinder health screening once in the system,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, measured in the best circumstances, namely:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• in conditions of no clearance
• under perpendicular detachment force
• under standard ambient temperature

What influences lifting capacity in practice

In practice, the holding capacity of a magnet is affected by these factors, in descending order of 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 measured using a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, whereas under shearing force the holding force is lower. In addition, even a small distance {between} the magnet’s surface and the plate lowers the load capacity.