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

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their notable holding force, neodymium magnets have these key benefits:

• They retain their full power for around ten years – the drop is just ~1% (in theory),
• They show strong resistance to demagnetization from external field exposure,
• Because of the brilliant layer of silver, the component looks aesthetically refined,
• The outer field strength of the magnet shows remarkable magnetic properties,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• With the option for tailored forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving design adaptation,
• Significant impact in cutting-edge sectors – they are utilized in hard drives, electromechanical systems, clinical machines along with sophisticated instruments,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are fragile when subjected to a strong impact. If the magnets are exposed to external force, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage and additionally increases its overall durability,
• They lose power at elevated temperatures. Most neodymium magnets experience permanent loss 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,
• Magnets exposed to wet conditions can degrade. Therefore, for outdoor applications, we suggest waterproof types made of coated materials,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is difficult,
• Potential hazard from tiny pieces may arise, when consumed by mistake, which is important in the context of child safety. Moreover, small elements from these products may disrupt scanning once in the system,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Best holding force of the magnet in ideal parameters – what it depends on?

The given holding capacity of the magnet means the highest holding force, determined in ideal conditions, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• in a perpendicular direction of force
• under standard ambient temperature

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is conditioned by these factors, from crucial to less important:

• 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.

* Lifting capacity testing was performed on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the load capacity is reduced by as much as fivefold. In addition, even a small distance {between} the magnet and the plate lowers the lifting capacity.