SM 25x350 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional strength, neodymium magnets offer the following advantages:

• They have constant strength, and over around 10 years their performance decreases symbolically – ~1% (according to theory),
• They are highly resistant to demagnetization caused by external field interference,
• In other words, due to the shiny nickel coating, the magnet obtains an stylish appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for tailored forming and targeted design, these magnets can be produced in various shapes and sizes, greatly improving design adaptation,
• Important function in cutting-edge sectors – they find application in hard drives, electromechanical systems, diagnostic apparatus along with other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to physical collisions, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage and additionally strengthens its overall resistance,
• They lose power at elevated temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the dimensions 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 recommend waterproof types made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing holes directly in the magnet,
• Potential hazard due to small fragments may arise, if ingested accidentally, which is important in the family environments. It should also be noted that tiny components from these magnets can complicate medical imaging when ingested,
• Due to expensive raw materials, their cost is above average,

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

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

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

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is affected by the following aspects, from crucial to less important:

• 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 assessed by applying a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, whereas under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Moreover, even a slight gap {between} the magnet and the plate reduces the load capacity.