SM 18x100 [2xM5] / N42 - magnetic separator

Strengths as well as weaknesses of NdFeB magnets.

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

• They do not lose magnetism, even over approximately 10 years – the decrease in lifting capacity is only ~1% (based on measurements),
• Neodymium magnets remain extremely resistant to demagnetization caused by external magnetic fields,
• A magnet with a smooth silver surface is more attractive,
• The surface of neodymium magnets generates a concentrated magnetic field – this is one of their assets,
• Through (appropriate) combination of ingredients, they can achieve high thermal resistance, enabling operation at temperatures reaching 230°C and above...
• Possibility of individual machining and modifying to individual requirements,
• Key role in advanced technology sectors – they are commonly used in mass storage devices, electric motors, advanced medical instruments, as well as industrial machines.
• Thanks to their power density, small magnets offer high operating force, with minimal size,

What to avoid - cons of neodymium magnets and proposals for their use:

• 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 increases its resistance to damage
• Neodymium magnets decrease their power 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
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material immune to moisture, in case of application outdoors
• We recommend cover - magnetic holder, due to difficulties in creating nuts inside the magnet and complicated shapes.
• Health risk resulting from small fragments of magnets pose a threat, in case of ingestion, which gains importance in the aspect of protecting the youngest. It is also worth noting that small components of these devices can be problematic in diagnostics medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Magnetic strength at its maximum – what contributes to it?

The force parameter is a measurement result executed under specific, ideal conditions:

• on a plate made of structural steel, effectively closing the magnetic flux
• possessing a massiveness of min. 10 mm to ensure full flux closure
• characterized by lack of roughness
• without the slightest clearance between the magnet and steel
• under vertical application of breakaway force (90-degree angle)
• at conditions approx. 20°C

Impact of factors on magnetic holding capacity in practice

Bear in mind that the application force will differ depending on elements below, in order of importance:

• Clearance – the presence of any layer (rust, dirt, gap) interrupts the magnetic circuit, which lowers power steeply (even by 50% at 0.5 mm).
• Direction of force – maximum parameter is available only during pulling at a 90° angle. The shear force of the magnet along the plate is typically many times smaller (approx. 1/5 of the lifting capacity).
• Wall thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of generating force.
• Steel type – low-carbon steel gives the best results. Higher carbon content decrease magnetic permeability and holding force.
• Surface finish – full contact is possible only on smooth steel. Rough texture create air cushions, weakening the magnet.
• Thermal environment – heating the magnet results in weakening of induction. Check the thermal limit for a given model.

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under parallel forces the lifting capacity is smaller. In addition, even a small distance {between} the magnet’s surface and the plate lowers the lifting capacity.