SMZR 32x200 / N52 - magnetic separator with handle

Strengths and weaknesses of rare earth magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They do not lose strength, even after nearly ten years – the drop in power is only ~1% (based on measurements),
• They have excellent resistance to magnetic field loss when exposed to opposing magnetic fields,
• Thanks to the smooth finish, the surface of nickel, gold, or silver gives an elegant appearance,
• Magnets are characterized by extremely high magnetic induction on the active area,
• Thanks to resistance to high temperature, they can operate (depending on the form) even at temperatures up to 230°C and higher...
• Due to the option of precise molding and customization to custom projects, NdFeB magnets can be modeled in a wide range of geometric configurations, which expands the range of possible applications,
• Key role in electronics industry – they are commonly used in mass storage devices, drive modules, precision medical tools, as well as industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which enables their usage in compact constructions

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

• 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 demagnetize 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 recommend using waterproof magnets made of rubber, plastic or other material immune to moisture, when using outdoors
• Limited possibility of creating nuts in the magnet and complicated shapes - recommended is cover - magnet mounting.
• Health risk to health – tiny shards of magnets pose a threat, in case of ingestion, which is particularly important in the context of child safety. It is also worth noting that tiny parts of these devices can be problematic in diagnostics medical in case of swallowing.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum holding power of the magnet – what affects it?

The force parameter is a result of laboratory testing performed under the following configuration:

• using a sheet made of low-carbon steel, functioning as a ideal flux conductor
• possessing a thickness of at least 10 mm to avoid saturation
• with a plane cleaned and smooth
• with total lack of distance (no paint)
• during detachment in a direction vertical to the mounting surface
• in temp. approx. 20°C

Magnet lifting force in use – key factors

It is worth knowing that the magnet holding will differ subject to the following factors, in order of importance:

• Distance – the presence of any layer (rust, tape, air) acts as an insulator, which lowers capacity rapidly (even by 50% at 0.5 mm).
• Loading method – catalog parameter refers to pulling vertically. When applying parallel force, the magnet exhibits significantly lower power (typically approx. 20-30% of nominal force).
• Plate thickness – insufficiently thick steel does not close the flux, causing part of the flux to be escaped into the air.
• Plate material – mild steel gives the best results. Higher carbon content reduce magnetic permeability and lifting capacity.
• Surface finish – ideal contact is obtained only on smooth steel. Any scratches and bumps create air cushions, reducing force.
• Temperature – heating the magnet results in weakening of induction. It is worth remembering the thermal limit for a given model.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the lifting capacity is smaller. In addition, even a slight gap {between} the magnet’s surface and the plate lowers the load capacity.