SM 25x325 [2xM8] / N42 - magnetic separator

Strengths and weaknesses of NdFeB magnets.

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

• They have stable power, and over nearly 10 years their performance decreases symbolically – ~1% (according to theory),
• Neodymium magnets prove to be remarkably resistant to magnetic field loss caused by external magnetic fields,
• A magnet with a shiny silver surface has better aesthetics,
• The surface of neodymium magnets generates a unique magnetic field – this is a distinguishing feature,
• 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 adapt to unusual requirements,
• Fundamental importance in modern technologies – they find application in HDD drives, drive modules, medical devices, and modern systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in small dimensions, which enables their usage in miniature devices

Problematic aspects of neodymium magnets: weaknesses and usage proposals

• To avoid cracks upon strong impacts, we suggest using special steel housings. Such a solution protects the magnet and simultaneously improves its durability.
• NdFeB magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening 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 extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• Due to limitations in producing threads and complicated forms in magnets, we propose using cover - magnetic mechanism.
• Health risk resulting from small fragments of magnets can be dangerous, in case of ingestion, which becomes key in the aspect of protecting the youngest. Furthermore, small elements of these products are able to complicate diagnosis medical after entering the body.
• Due to complex production process, their price exceeds standard values,

Maximum holding power of the magnet – what affects it?

The force parameter is a theoretical maximum value performed under standard conditions:

• using a plate made of high-permeability steel, acting as a circuit closing element
• with a cross-section of at least 10 mm
• characterized by smoothness
• under conditions of ideal adhesion (surface-to-surface)
• for force acting at a right angle (pull-off, not shear)
• in stable room temperature

Determinants of lifting force in real conditions

In practice, the real power is determined by several key aspects, ranked from crucial:

• Distance (betwixt the magnet and the plate), because even a microscopic clearance (e.g. 0.5 mm) leads to a reduction in lifting capacity by up to 50% (this also applies to varnish, rust or debris).
• Force direction – note that the magnet holds strongest perpendicularly. Under sliding down, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Metal thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field penetrates through instead of converting into lifting capacity.
• Chemical composition of the base – low-carbon steel attracts best. Alloy steels reduce magnetic permeability and holding force.
• Surface quality – the smoother and more polished the surface, the larger the contact zone and stronger the hold. Roughness acts like micro-gaps.
• Thermal conditions – neodymium magnets have a sensitivity to temperature. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).

* Lifting capacity was measured using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, however under parallel forces the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet and the plate decreases the lifting capacity.