SM 18x225 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of NdFeB magnets.

Besides their exceptional strength, neodymium magnets offer the following advantages:

• They virtually do not lose power, because even after 10 years the performance loss is only ~1% (according to literature),
• Magnets very well resist against loss of magnetization caused by ambient magnetic noise,
• In other words, due to the glossy surface of nickel, the element becomes visually attractive,
• They are known for high magnetic induction at the operating surface, which affects their effectiveness,
• 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...
• Possibility of custom modeling and modifying to specific applications,
• Key role in future technologies – they find application in mass storage devices, motor assemblies, diagnostic systems, and industrial machines.
• Thanks to efficiency per cm³, small magnets offer high operating force, occupying minimum space,

Problematic aspects of neodymium magnets and proposals for their use:

• At very strong impacts they can crack, therefore we advise placing them in special holders. A metal housing provides additional protection against damage and increases the magnet's 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 and dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
• They rust in a humid environment - during use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited possibility of creating threads in the magnet and complicated forms - preferred is a housing - magnet mounting.
• Potential hazard related to microscopic parts of magnets can be dangerous, in case of ingestion, which is particularly important in the context of child safety. Furthermore, tiny parts of these magnets can be problematic in diagnostics medical after entering the body.
• Due to neodymium price, their price exceeds standard values,

Maximum holding power of the magnet – what affects it?

The lifting capacity listed is a measurement result conducted under the following configuration:

• using a base made of high-permeability steel, functioning as a magnetic yoke
• with a thickness no less than 10 mm
• with a plane free of scratches
• under conditions of no distance (surface-to-surface)
• during detachment in a direction vertical to the mounting surface
• in temp. approx. 20°C

Determinants of lifting force in real conditions

Effective lifting capacity is influenced by working environment parameters, mainly (from priority):

• Distance – existence of foreign body (rust, dirt, air) interrupts the magnetic circuit, which lowers power steeply (even by 50% at 0.5 mm).
• Direction of force – highest force is available only during perpendicular pulling. The resistance to sliding of the magnet along the surface is usually many times smaller (approx. 1/5 of the lifting capacity).
• Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal restricts the attraction force (the magnet "punches through" it).
• Chemical composition of the base – mild steel gives the best results. Higher carbon content lower magnetic properties and holding force.
• Base smoothness – the more even the surface, the better the adhesion and higher the lifting capacity. Roughness acts like micro-gaps.
• Heat – neodymium magnets have a negative temperature coefficient. When it is hot they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Lifting capacity was assessed with the use of a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, whereas under parallel forces the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.