SM 18x300 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their superior magnetism, neodymium magnets have these key benefits:

• They have constant strength, and over nearly 10 years their attraction force decreases symbolically – ~1% (in testing),
• They are highly resistant to demagnetization caused by external field interference,
• Because of the reflective layer of gold, the component looks visually appealing,
• Magnetic induction on the surface of these magnets is very strong,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the form),
• With the option for tailored forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Wide application in advanced technical fields – they are used in hard drives, electric drives, medical equipment or even sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which makes them useful in miniature devices

Disadvantages of NdFeB magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to shocks, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time reinforces its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent loss in performance (depending on height). 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,
• They rust in a humid environment, especially when used outside, we recommend using encapsulated magnets, such as those made of non-metallic materials,
• Limited ability to create precision features in the magnet – the use of a mechanical support is recommended,
• Health risk related to magnet particles may arise, especially if swallowed, which is significant in the protection of children. It should also be noted that miniature parts from these devices can complicate medical imaging after being swallowed,
• Due to the price of neodymium, their cost is considerably higher,

Maximum lifting force for a neodymium magnet – what affects it?

The given lifting capacity of the magnet represents the maximum lifting force, calculated under optimal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• under standard ambient temperature

Determinants of lifting force in real conditions

Practical lifting force is determined by elements, listed from the most critical to the less 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 conducted on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, however under shearing force the load capacity is reduced by as much as 75%. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.