SM 18x250 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• Their magnetic field is durable, and after around ten years, it drops only by ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is impressive,
• In other words, due to the glossy nickel coating, the magnet obtains an stylish appearance,
• They have very high magnetic induction on the surface of the magnet,
• These magnets tolerate elevated 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 various configurations, which broadens their application range,
• Key role in cutting-edge sectors – they serve a purpose in hard drives, rotating machines, healthcare devices or even sophisticated instruments,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to shocks, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from damage , and at the same time enhances its overall robustness,
• They lose power at extreme temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the form and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a damp environment – during outdoor use, we recommend using moisture-resistant magnets, such as those made of plastic,
• Limited ability to create internal holes in the magnet – the use of a housing is recommended,
• Potential hazard due to small fragments may arise, if ingested accidentally, which is significant in the protection of children. It should also be noted that minuscule fragments from these assemblies have the potential to complicate medical imaging when ingested,
• Due to the price of neodymium, their cost is above average,

Maximum lifting capacity of the magnet – what it depends on?

The given pulling force of the magnet represents the maximum force, determined in ideal conditions, that is:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• with vertical force applied
• under standard ambient temperature

Practical aspects of lifting capacity – factors

The lifting capacity of a magnet is determined by in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, as 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 vertically applied force, however under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the lifting capacity.