SM 32x150 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They retain their magnetic properties for almost ten years – the drop is just ~1% (based on simulations),
• Their ability to resist magnetic interference from external fields is notable,
• By applying a shiny layer of gold, the element gains a clean look,
• They possess strong magnetic force measurable at the magnet’s surface,
• Thanks to their high temperature resistance, they can operate (depending on the geometry) even at temperatures up to 230°C or more,
• Thanks to the freedom in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in various configurations, which broadens their usage potential,
• Wide application in cutting-edge sectors – they serve a purpose in data storage devices, electric drives, diagnostic apparatus and sophisticated instruments,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to physical collisions, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage while also strengthens its overall strength,
• High temperatures may significantly reduce the strength 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 wet conditions can rust. Therefore, for outdoor applications, it's best to use waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Possible threat due to small fragments may arise, in case of ingestion, which is important in the context of child safety. Moreover, tiny components from these assemblies may complicate medical imaging after being swallowed,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Detachment force of the magnet in optimal conditions – what affects it?

The given strength of the magnet represents the optimal strength, calculated in the best circumstances, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• in a perpendicular direction of force
• under standard ambient temperature

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is conditioned by the following aspects, from crucial to less important:

• Air gap between the magnet and the plate, because 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 tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under shearing force the load capacity is reduced by as much as fivefold. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.