SM 32x275 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They retain their magnetic properties for nearly 10 years – the drop is just ~1% (according to analyses),
• Their ability to resist magnetic interference from external fields is among the best,
• By applying a bright layer of silver, the element gains a clean look,
• They have very high magnetic induction on the surface of the magnet,
• With the right combination of materials, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the design),
• With the option for tailored forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Significant impact in advanced technical fields – they find application in HDDs, electric motors, diagnostic apparatus along with sophisticated instruments,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They can break when subjected to a heavy impact. If the magnets are exposed to external force, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks and additionally reinforces its overall strength,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s form). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to humidity can degrade. Therefore, for outdoor applications, we recommend waterproof types made of rubber,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is restricted,
• Potential hazard from tiny pieces may arise, in case of ingestion, which is important in the health of young users. Additionally, miniature parts from these devices might interfere with diagnostics after being swallowed,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Optimal lifting capacity of a neodymium magnet – what affects it?

The given pulling force of the magnet represents the maximum force, determined in ideal conditions, specifically:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with no separation
• in a perpendicular direction of force
• at room temperature

What influences lifting capacity in practice

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

• 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.

* Lifting capacity testing was carried out on a smooth plate of optimal thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Moreover, even a small distance {between} the magnet and the plate reduces the load capacity.