SM 32x275 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• They retain their full power for almost ten years – the drop is just ~1% (in theory),
• They show strong resistance to demagnetization from external field exposure,
• Because of the reflective layer of nickel, the component looks aesthetically refined,
• The outer field strength of the magnet shows advanced magnetic properties,
• Thanks to their enhanced temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• With the option for fine forming and targeted design, these magnets can be produced in multiple shapes and sizes, greatly improving design adaptation,
• Wide application in modern technologies – they find application in hard drives, electromechanical systems, diagnostic apparatus as well as sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which makes them useful in miniature devices

Disadvantages of NdFeB magnets:

• They can break when subjected to a heavy 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 fracture , and at the same time increases its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on size). 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 oxidize. Therefore, for outdoor applications, we recommend waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing complex structures directly in the magnet,
• Potential hazard from tiny pieces may arise, in case of ingestion, which is important in the context of child safety. It should also be noted that miniature parts from these magnets can interfere with diagnostics when ingested,
• In cases of tight budgets, neodymium magnet cost may not be economically viable,

Maximum lifting force for a neodymium magnet – what contributes to it?

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

• 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
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Determinants of practical lifting force of a magnet

Practical lifting force is dependent on factors, 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) 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.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, however under parallel forces the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate decreases the holding force.