SM 18x125 [2xM5] / 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 strength approximately 10 years – the decrease of lifting capacity is only ~1% (theoretically),
• They protect against demagnetization induced by surrounding magnetic fields effectively,
• In other words, due to the shiny silver coating, the magnet obtains an professional appearance,
• They possess significant magnetic force measurable at the magnet’s surface,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• Thanks to the freedom in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in different geometries, which increases their functional possibilities,
• Wide application in cutting-edge sectors – they are utilized in hard drives, electromechanical systems, medical equipment along with technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which makes them useful in small systems

Disadvantages of NdFeB magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to shocks, it is suggested to place them 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 performance loss (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,
• Magnets exposed to humidity 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 threads directly in the magnet,
• Safety concern related to magnet particles may arise, if ingested accidentally, which is crucial in the family environments. Moreover, small elements from these devices might interfere with diagnostics when ingested,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Breakaway strength of the magnet in ideal conditions – what it depends on?

The given lifting capacity of the magnet represents the maximum lifting force, measured in ideal conditions, specifically:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• in conditions of no clearance
• in a perpendicular direction of force
• under standard ambient temperature

Lifting capacity in practice – influencing factors

Practical lifting force is dependent on factors, by priority:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) causes 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 a perpendicular force was applied, however under parallel forces the holding force is lower. In addition, even a small distance {between} the magnet and the plate lowers the lifting capacity.