SM 32x150 [2xM8] / N52 - magnetic separator

Strengths and weaknesses of neodymium magnets.

Besides their remarkable pulling force, neodymium magnets offer the following advantages:

• They do not lose magnetism, even during approximately 10 years – the drop in power is only ~1% (based on measurements),
• They are extremely resistant to demagnetization induced by presence of other magnetic fields,
• In other words, due to the reflective surface of nickel, the element looks attractive,
• They show high magnetic induction at the operating surface, making them more effective,
• Through (adequate) combination of ingredients, they can achieve high thermal resistance, enabling operation at temperatures approaching 230°C and above...
• Possibility of precise modeling and modifying to complex conditions,
• Universal use in electronics industry – they serve a role in HDD drives, brushless drives, advanced medical instruments, and industrial machines.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Problematic aspects of neodymium magnets and ways of using them

• To avoid cracks under impact, we suggest using special steel holders. Such a solution secures the magnet and simultaneously improves its durability.
• Neodymium magnets decrease their strength 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
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• We suggest a housing - magnetic mechanism, due to difficulties in creating nuts inside the magnet and complicated shapes.
• Potential hazard to health – tiny shards of magnets can be dangerous, if swallowed, which becomes key in the context of child health protection. Furthermore, tiny parts of these devices are able to complicate diagnosis medical in case of swallowing.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which hinders application in large quantities

Highest magnetic holding force – what affects it?

The declared magnet strength represents the peak performance, recorded under optimal environment, meaning:

• using a plate made of low-carbon steel, serving as a ideal flux conductor
• whose transverse dimension is min. 10 mm
• with an polished touching surface
• without the slightest insulating layer between the magnet and steel
• under vertical application of breakaway force (90-degree angle)
• at room temperature

Magnet lifting force in use – key factors

In practice, the actual holding force depends on a number of factors, presented from most significant:

• Gap between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by veneer or unevenness) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Direction of force – maximum parameter is reached only during pulling at a 90° angle. The force required to slide of the magnet along the plate is standardly many times lower (approx. 1/5 of the lifting capacity).
• Wall thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of generating force.
• Steel type – low-carbon steel gives the best results. Alloy admixtures reduce magnetic properties and lifting capacity.
• Plate texture – smooth surfaces guarantee perfect abutment, which improves force. Uneven metal reduce efficiency.
• Thermal factor – hot environment reduces magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the load capacity is reduced by as much as fivefold. Additionally, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.