SM 25x200 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their durability, neodymium magnets are valued for these benefits:

• They do not lose their magnetism, even after around ten years – the reduction of strength is only ~1% (based on measurements),
• They remain magnetized despite exposure to strong external fields,
• In other words, due to the shiny nickel coating, the magnet obtains an professional appearance,
• They have very high magnetic induction on the surface of the magnet,
• With the right combination of materials, they reach significant thermal stability, enabling operation at or above 230°C (depending on the structure),
• With the option for fine forming and personalized design, these magnets can be produced in multiple shapes and sizes, greatly improving application potential,
• Important function in new technology industries – they serve a purpose in HDDs, rotating machines, medical equipment and high-tech tools,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to physical collisions, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and strengthens its overall strength,
• They lose strength at elevated temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to moisture can rust. Therefore, for outdoor applications, we suggest waterproof types made of plastic,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is risky,
• Potential hazard related to magnet particles may arise, if ingested accidentally, which is crucial in the protection of children. Moreover, minuscule fragments from these devices may hinder health screening if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given strength of the magnet represents the optimal strength, calculated under optimal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is affected by these factors, arranged from the most important to the least relevant:

• 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 with the use of a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, however under shearing force the lifting capacity is smaller. In addition, even a small distance {between} the magnet and the plate decreases the load capacity.