SM 25x200 [2xM8] / N52 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

Apart from their superior holding force, neodymium magnets have these key benefits:

• Their power remains stable, and after around 10 years it drops only by ~1% (according to research),
• They have excellent resistance to magnetic field loss as a result of external magnetic sources,
• Thanks to the glossy finish, the plating of Ni-Cu-Ni, gold-plated, or silver-plated gives an professional appearance,
• The surface of neodymium magnets generates a intense magnetic field – this is one of their assets,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their form) at temperatures up to 230°C and above...
• Thanks to freedom in designing and the ability to customize to individual projects,
• Key role in innovative solutions – they are commonly used in HDD drives, electric motors, medical equipment, as well as other advanced devices.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Characteristics of disadvantages of neodymium magnets: weaknesses and usage proposals

• They are fragile upon too strong impacts. To avoid cracks, it is worth protecting magnets using a steel holder. Such protection not only protects the magnet but also improves its resistance to damage
• Neodymium magnets lose 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 stability even at temperatures up to 230°C
• They oxidize in a humid environment - during use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
• Limited possibility of creating threads in the magnet and complicated forms - preferred is cover - magnet mounting.
• Potential hazard to health – tiny shards of magnets are risky, when accidentally swallowed, which gains importance in the context of child health protection. Furthermore, tiny parts of these products can disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum holding power of the magnet – what affects it?

Holding force of 0 kg is a theoretical maximum value performed under standard conditions:

• on a base made of structural steel, optimally conducting the magnetic field
• possessing a massiveness of minimum 10 mm to avoid saturation
• with an ground contact surface
• with total lack of distance (without coatings)
• for force applied at a right angle (pull-off, not shear)
• in stable room temperature

What influences lifting capacity in practice

In real-world applications, the actual lifting capacity results from several key aspects, listed from the most important:

• Air gap (betwixt the magnet and the metal), because even a microscopic clearance (e.g. 0.5 mm) results in a decrease in lifting capacity by up to 50% (this also applies to varnish, rust or dirt).
• Angle of force application – highest force is available only during perpendicular pulling. The resistance to sliding of the magnet along the surface is usually several times smaller (approx. 1/5 of the lifting capacity).
• Plate thickness – too thin sheet does not close the flux, causing part of the flux to be escaped into the air.
• Steel type – low-carbon steel attracts best. Higher carbon content reduce magnetic properties and holding force.
• Surface finish – full contact is obtained only on smooth steel. Rough texture reduce the real contact area, reducing force.
• Thermal conditions – NdFeB sinters have a negative temperature coefficient. At higher temperatures they lose power, and in frost gain strength (up to a certain limit).

* Lifting capacity testing was carried out on a smooth plate of suitable thickness, under perpendicular forces, whereas under shearing force the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the lifting capacity.