SMZR 25x200 / N52 - magnetic separator with handle

Strengths as well as weaknesses of NdFeB magnets.

Besides their high retention, neodymium magnets are valued for these benefits:

• They do not lose strength, even after around ten years – the decrease in strength is only ~1% (based on measurements),
• Neodymium magnets are exceptionally resistant to magnetic field loss caused by external magnetic fields,
• A magnet with a shiny nickel surface looks better,
• The surface of neodymium magnets generates a concentrated 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...
• Possibility of accurate forming and adjusting to atypical applications,
• Versatile presence in electronics industry – they serve a role in mass storage devices, electric drive systems, medical devices, and multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in small dimensions, which makes them useful in miniature devices

Disadvantages of neodymium magnets:

• To avoid cracks upon strong impacts, we recommend using special steel housings. Such a solution protects the magnet and simultaneously increases 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 force. 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, when using outdoors
• We suggest cover - magnetic mechanism, due to difficulties in creating nuts inside the magnet and complicated shapes.
• Potential hazard resulting from small fragments of magnets pose a threat, in case of ingestion, which is particularly important in the context of child health protection. Furthermore, small elements of these products can disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Highest magnetic holding force – what contributes to it?

Magnet power is the result of a measurement for optimal configuration, assuming:

• using a plate made of low-carbon steel, functioning as a ideal flux conductor
• with a thickness of at least 10 mm
• with a plane cleaned and smooth
• under conditions of ideal adhesion (surface-to-surface)
• for force applied at a right angle (in the magnet axis)
• at temperature room level

Impact of factors on magnetic holding capacity in practice

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

• Distance (betwixt the magnet and the metal), since even a microscopic distance (e.g. 0.5 mm) results in a drastic drop in lifting capacity by up to 50% (this also applies to varnish, corrosion or dirt).
• Load vector – maximum parameter is obtained only during pulling at a 90° angle. The resistance to sliding of the magnet along the plate is usually many times lower (approx. 1/5 of the lifting capacity).
• Element thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Steel type – mild steel attracts best. Higher carbon content decrease magnetic permeability and lifting capacity.
• Base smoothness – the smoother and more polished the surface, the better the adhesion and higher the lifting capacity. Unevenness creates an air distance.
• Thermal factor – hot environment weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was checked on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet’s surface and the plate decreases the holding force.