SM 25x225 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their notable holding force, neodymium magnets have these key benefits:

• Their strength remains stable, and after around ten years, it drops only by ~1% (theoretically),
• They protect against demagnetization induced by ambient electromagnetic environments remarkably well,
• By applying a reflective layer of gold, the element gains a modern look,
• They possess intense magnetic force measurable at the magnet’s surface,
• 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 geometry),
• The ability for accurate shaping and adaptation to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Wide application in modern technologies – they are used in computer drives, electromechanical systems, healthcare devices and sophisticated instruments,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to mechanical hits, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall robustness,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is common to use sealed magnets made of rubber for outdoor use,
• Limited ability to create internal holes in the magnet – the use of a magnetic holder is recommended,
• Health risk linked to microscopic shards may arise, when consumed by mistake, which is notable in the health of young users. Additionally, tiny components from these devices might complicate medical imaging when ingested,
• Due to a complex production process, their cost is above average,

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

The given holding capacity of the magnet corresponds to the highest holding force, calculated under optimal conditions, namely:

• 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
• 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 conditioned 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.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the holding force.