SM 18x150 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of rare earth magnets.

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

• They do not lose magnetism, even over around ten years – the drop in lifting capacity is only ~1% (theoretically),
• Neodymium magnets remain extremely resistant to magnetic field loss caused by external field sources,
• In other words, due to the smooth finish of gold, the element is aesthetically pleasing,
• Magnets exhibit exceptionally strong magnetic induction on the active area,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Thanks to freedom in forming and the ability to adapt to individual projects,
• Universal use in advanced technology sectors – they are used in HDD drives, motor assemblies, precision medical tools, as well as modern systems.
• Thanks to their power density, small magnets offer high operating force, occupying minimum space,

Disadvantages of NdFeB magnets:

• To avoid cracks upon strong impacts, we recommend using special steel holders. Such a solution protects the magnet and simultaneously improves its durability.
• Neodymium magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• They oxidize in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited possibility of creating threads in the magnet and complex forms - preferred is casing - magnetic holder.
• Health risk to health – tiny shards of magnets can be dangerous, when accidentally swallowed, which gains importance in the context of child health protection. It is also worth noting that small components of these magnets can be problematic in diagnostics medical after entering the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum holding power of the magnet – what contributes to it?

Holding force of 0 kg is a theoretical maximum value executed under the following configuration:

• using a plate made of mild steel, serving as a magnetic yoke
• whose transverse dimension is min. 10 mm
• with a surface cleaned and smooth
• under conditions of ideal adhesion (metal-to-metal)
• under axial force direction (90-degree angle)
• in neutral thermal conditions

Practical aspects of lifting capacity – factors

In real-world applications, the real power results from a number of factors, ranked from the most important:

• Gap between magnet and steel – even a fraction of a millimeter of separation (caused e.g. by veneer or dirt) significantly weakens the pulling force, often by half at just 0.5 mm.
• Loading method – catalog parameter refers to pulling vertically. When slipping, the magnet exhibits significantly lower power (often approx. 20-30% of maximum force).
• Substrate thickness – for full efficiency, the steel must be adequately massive. Thin sheet restricts the attraction force (the magnet "punches through" it).
• Steel type – mild steel gives the best results. Alloy steels reduce magnetic permeability and lifting capacity.
• Surface finish – ideal contact is possible only on smooth steel. Any scratches and bumps create air cushions, weakening the magnet.
• Temperature influence – high temperature reduces magnetic field. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the load capacity is reduced by as much as fivefold. In addition, even a minimal clearance {between} the magnet’s surface and the plate reduces the holding force.