SM 25x300 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They virtually do not lose strength, because even after 10 years, the performance loss is only ~1% (in laboratory conditions),
• They remain magnetized despite exposure to magnetic noise,
• In other words, due to the glossy nickel coating, the magnet obtains an professional appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• Thanks to the freedom in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in various configurations, which expands their application range,
• Key role in advanced technical fields – they are utilized in data storage devices, electromechanical systems, clinical machines and sophisticated instruments,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to mechanical hits, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage and additionally enhances its overall strength,
• They lose strength at extreme temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of rubber for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing complex structures directly in the magnet,
• Possible threat linked to microscopic shards may arise, especially if swallowed, which is crucial in the family environments. Moreover, small elements from these assemblies can hinder health screening after being swallowed,
• 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 lifting capacity of the magnet corresponds to the maximum lifting force, measured in the best circumstances, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a polished side
• with zero air gap
• with vertical force applied
• under standard ambient temperature

Lifting capacity in real conditions – factors

The lifting capacity of a magnet depends on in practice the following factors, ordered from most important to least significant:

• 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 testing was carried out on a smooth plate of optimal thickness, under perpendicular forces, whereas under parallel forces the load capacity is reduced by as much as fivefold. In addition, even a slight gap {between} the magnet’s surface and the plate reduces the load capacity.