SM 25x100 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their tremendous pulling force, neodymium magnets offer the following advantages:

• They have stable power, and over nearly ten years their performance decreases symbolically – ~1% (according to theory),
• They are highly resistant to demagnetization caused by external magnetic sources,
• By applying a reflective layer of silver, the element gains a sleek look,
• The outer field strength of the magnet shows advanced magnetic properties,
• Thanks to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for fine forming and targeted design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Important function in new technology industries – they find application in data storage devices, rotating machines, healthcare devices and sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to shocks, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture while also enhances its overall resistance,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Magnets exposed to damp air can corrode. 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,
• Safety concern from tiny pieces may arise, if ingested accidentally, which is crucial in the context of child safety. Additionally, small elements from these devices can disrupt scanning when ingested,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, assessed in the best circumstances, that is:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• in a perpendicular direction of force
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• 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.

* Lifting capacity was determined with the use of a polished steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, however under parallel forces the lifting capacity is smaller. Additionally, even a small distance {between} the magnet and the plate reduces the lifting capacity.