SM 25x325 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They do not lose their even over around ten years – the decrease of power is only ~1% (based on measurements),
• Their ability to resist magnetic interference from external fields is impressive,
• By applying a shiny layer of silver, the element gains a modern look,
• They possess strong magnetic force measurable at the magnet’s surface,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• With the option for fine forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Significant impact in modern technologies – they are utilized in data storage devices, rotating machines, medical equipment along with other advanced devices,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to shocks, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and enhances its overall robustness,
• Magnets lose field strength 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,
• Due to corrosion risk in humid conditions, it is advisable to use sealed magnets made of protective material for outdoor use,
• Limited ability to create internal holes in the magnet – the use of a mechanical support is recommended,
• Possible threat due to small fragments may arise, if ingested accidentally, which is significant in the context of child safety. It should also be noted that miniature parts from these magnets can interfere with diagnostics once in the system,
• In cases of tight budgets, neodymium magnet cost is a challenge,

Best holding force of the magnet in ideal parameters – what it depends on?

The given lifting capacity of the magnet means the maximum lifting force, determined in the best circumstances, that is:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• at room temperature

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is affected by the following aspects, from crucial to less important:

• Air gap between the magnet and the plate, because 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 testing was performed on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, whereas under shearing force the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.