SM 32x300 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their remarkable magnetic power, neodymium magnets offer the following advantages:

• They have stable power, and over more than ten years their performance decreases symbolically – ~1% (according to theory),
• Their ability to resist magnetic interference from external fields is notable,
• Because of the lustrous layer of silver, the component looks high-end,
• Magnetic induction on the surface of these magnets is notably high,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• With the option for customized forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Wide application in advanced technical fields – they find application in HDDs, electric motors, healthcare devices and technologically developed systems,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to external force, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture and additionally enhances its overall robustness,
• 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,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of plastic for outdoor use,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Potential hazard related to magnet particles may arise, especially if swallowed, which is important in the health of young users. Additionally, minuscule fragments from these products might disrupt scanning once in the system,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum holding power of the magnet – what it depends on?

The given pulling force of the magnet means the maximum force, determined in a perfect environment, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a smooth surface
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing factors

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

• Air gap between the magnet and the plate, since 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.

* Lifting capacity was assessed using a smooth steel plate of suitable thickness (min. 20 mm), under vertically applied force, in contrast under parallel forces the holding force is lower. In addition, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.