SM 25x100 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of NdFeB magnets.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They do not lose magnetism, even over approximately ten years – the reduction in lifting capacity is only ~1% (based on measurements),
• They retain their magnetic properties even under close interference source,
• Thanks to the shiny finish, the coating of nickel, gold-plated, or silver-plated gives an elegant appearance,
• The surface of neodymium magnets generates a strong magnetic field – this is a key feature,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Possibility of detailed forming as well as adjusting to specific applications,
• Versatile presence in modern technologies – they find application in computer drives, brushless drives, diagnostic systems, and complex engineering applications.
• Thanks to efficiency per cm³, small magnets offer high operating force, in miniature format,

Cons of neodymium magnets: application proposals

• To avoid cracks under impact, we recommend using special steel housings. Such a solution protects the magnet and simultaneously increases its durability.
• Neodymium magnets decrease their force under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• When exposed to humidity, magnets usually rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• Due to limitations in producing nuts and complicated shapes in magnets, we propose using a housing - magnetic mechanism.
• Possible danger related to microscopic parts of magnets are risky, when accidentally swallowed, which becomes key in the context of child health protection. Furthermore, tiny parts of these devices are able to be problematic in diagnostics medical in case of swallowing.
• Due to complex production process, their price is higher than average,

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

The lifting capacity listed is a result of laboratory testing executed under standard conditions:

• on a block made of mild steel, effectively closing the magnetic flux
• with a cross-section minimum 10 mm
• characterized by smoothness
• without any clearance between the magnet and steel
• under axial force direction (90-degree angle)
• at conditions approx. 20°C

Lifting capacity in real conditions – factors

In real-world applications, the actual holding force results from several key aspects, presented from the most important:

• Space between magnet and steel – every millimeter of distance (caused e.g. by veneer or dirt) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Force direction – declared lifting capacity refers to detachment vertically. When slipping, the magnet exhibits much less (often approx. 20-30% of maximum force).
• Wall thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of generating force.
• Plate material – low-carbon steel gives the best results. Alloy admixtures lower magnetic permeability and holding force.
• Smoothness – ideal contact is obtained only on polished steel. Any scratches and bumps create air cushions, reducing force.
• Thermal environment – heating the magnet results in weakening of force. It is worth remembering the maximum operating temperature for a given model.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the lifting capacity is smaller. In addition, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.