SM 32x175 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They have constant strength, and over around ten years their performance decreases symbolically – ~1% (in testing),
• They show strong resistance to demagnetization from external magnetic fields,
• The use of a decorative nickel surface provides a eye-catching finish,
• They have very high magnetic induction on the surface of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• The ability for precise shaping or adaptation to specific needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which extends the scope of their use cases,
• Important function in modern technologies – they are utilized in HDDs, rotating machines, clinical machines or even other advanced devices,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to external force, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture and additionally increases its overall resistance,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s profile). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to moisture can rust. Therefore, for outdoor applications, we recommend waterproof types made of coated materials,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing fine shapes directly in the magnet,
• Possible threat due to small fragments may arise, in case of ingestion, which is crucial in the protection of children. Furthermore, small elements from these magnets may disrupt scanning when ingested,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Highest magnetic holding force – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, calculated in the best circumstances, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing factors

Practical lifting force is determined by elements, by priority:

• Air gap between the magnet and the plate, as 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 measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet and the plate lowers the lifting capacity.