SM 25x125 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have constant strength, and over more than ten years their performance decreases symbolically – ~1% (according to theory),
• They protect against demagnetization induced by ambient magnetic fields remarkably well,
• In other words, due to the shiny silver 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,
• With the option for tailored forming and personalized design, these magnets can be produced in various shapes and sizes, greatly improving design adaptation,
• Wide application in new technology industries – they find application in HDDs, electric motors, medical equipment along with sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which makes them ideal in compact constructions

Disadvantages of neodymium magnets:

• They are fragile 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 damage and enhances its overall robustness,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on shape). 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,
• Magnets exposed to humidity can corrode. Therefore, for outdoor applications, it's best to use waterproof types made of rubber,
• Limited ability to create internal holes in the magnet – the use of a housing is recommended,
• Possible threat related to magnet particles may arise, when consumed by mistake, which is crucial in the context of child safety. Moreover, miniature parts from these magnets can hinder health screening when ingested,
• In cases of large-volume purchasing, neodymium magnet cost may not be economically viable,

Best holding force of the magnet in ideal parameters – what contributes to it?

The given holding capacity of the magnet represents the highest holding force, assessed under optimal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a polished side
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Practical aspects of lifting capacity – factors

The lifting capacity of a magnet depends on in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, because 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 suitable thickness, under perpendicular forces, in contrast under shearing force the lifting capacity is smaller. In addition, even a slight gap {between} the magnet and the plate decreases the lifting capacity.