SMZR 25x100 / N52 - magnetic separator with handle

Strengths and weaknesses of NdFeB magnets.

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

• They do not lose strength, even during around ten years – the decrease in power is only ~1% (theoretically),
• They are extremely resistant to demagnetization induced by presence of other magnetic fields,
• By using a lustrous coating of gold, the element presents an professional look,
• Magnets have extremely high magnetic induction on the outer side,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can function (depending on the shape) even at a temperature of 230°C or more...
• Thanks to modularity in designing and the capacity to modify to individual projects,
• Key role in modern technologies – they are used in HDD drives, electric drive systems, advanced medical instruments, and technologically advanced constructions.
• Relatively small size with high pulling force – neodymium magnets offer high power in tiny dimensions, which makes them useful in miniature devices

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

• To avoid cracks upon strong impacts, we recommend using special steel holders. Such a solution secures the magnet and simultaneously improves its durability.
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture, when using outdoors
• We recommend a housing - magnetic holder, due to difficulties in realizing threads inside the magnet and complicated shapes.
• Health risk related to microscopic parts of magnets pose a threat, in case of ingestion, which becomes key in the context of child safety. It is also worth noting that tiny parts of these magnets can disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum holding power of the magnet – what affects it?

The declared magnet strength represents the peak performance, recorded under ideal test conditions, namely:

• using a plate made of high-permeability steel, acting as a magnetic yoke
• possessing a thickness of minimum 10 mm to ensure full flux closure
• characterized by even structure
• under conditions of no distance (metal-to-metal)
• for force applied at a right angle (pull-off, not shear)
• at temperature room level

Lifting capacity in practice – influencing factors

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

• Distance (between the magnet and the plate), as even a very small distance (e.g. 0.5 mm) results in a decrease in force by up to 50% (this also applies to varnish, rust or dirt).
• Direction of force – highest force is available only during pulling at a 90° angle. The force required to slide of the magnet along the plate is usually several times lower (approx. 1/5 of the lifting capacity).
• Metal thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field passes through the material instead of converting into lifting capacity.
• Material composition – not every steel attracts identically. High carbon content weaken the interaction with the magnet.
• Plate texture – ground elements guarantee perfect abutment, which increases force. Rough surfaces reduce efficiency.
• Temperature influence – hot environment weakens magnetic field. Exceeding the limit temperature can permanently demagnetize the magnet.

* Lifting capacity testing was performed on a smooth plate of optimal thickness, under perpendicular forces, whereas under parallel forces the holding force is lower. Moreover, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.