SM 32x400 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They have constant strength, and over around 10 years their performance decreases symbolically – ~1% (according to theory),
• They remain magnetized despite exposure to magnetic surroundings,
• By applying a bright layer of silver, the element gains a modern look,
• They possess intense magnetic force measurable at the magnet’s surface,
• Thanks to their high temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• The ability for accurate shaping or adaptation to custom needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Key role in modern technologies – they serve a purpose in HDDs, rotating machines, medical equipment and technologically developed systems,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of neodymium magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to shocks, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from damage while also increases its overall durability,
• High temperatures may significantly reduce the strength of neodymium magnets. Typically, above 80°C, they experience permanent loss 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 rust. Therefore, for outdoor applications, we recommend waterproof types made of non-metallic composites,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Safety concern linked to microscopic shards may arise, if ingested accidentally, which is important in the context of child safety. Additionally, miniature parts from these devices can hinder health screening when ingested,
• In cases of tight budgets, neodymium magnet cost may be a barrier,

Maximum holding power of the magnet – what contributes to it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, assessed in a perfect environment, that is:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a polished side
• with no separation
• in a perpendicular direction of force
• in normal thermal conditions

Practical lifting capacity: influencing factors

Practical lifting force is determined by factors, by priority:

• 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.

* Holding force was tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under attempts to slide the magnet the holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate decreases the holding force.