SM 18x175 [2xM5] / N42 - magnetic separator

Strengths and weaknesses of neodymium magnets.

Apart from their consistent power, neodymium magnets have these key benefits:

• They do not lose magnetism, even after approximately ten years – the reduction in lifting capacity is only ~1% (based on measurements),
• Neodymium magnets are distinguished by highly resistant to demagnetization caused by external field sources,
• By applying a smooth coating of silver, the element gains an aesthetic look,
• Magnetic induction on the top side of the magnet remains extremely intense,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Possibility of individual shaping as well as optimizing to atypical requirements,
• Wide application in modern industrial fields – they are utilized in computer drives, electromotive mechanisms, precision medical tools, as well as multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer high power in compact dimensions, which allows their use in compact constructions

Problematic aspects of neodymium magnets and proposals for their use:

• They are fragile upon too strong impacts. To avoid cracks, it is worth protecting magnets in a protective case. Such protection not only protects the magnet but also improves its resistance to damage
• 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 stability even at temperatures up to 230°C
• Magnets exposed to a humid environment can corrode. Therefore while using outdoors, we suggest using waterproof magnets made of rubber, plastic or other material protecting against moisture
• Limited possibility of producing threads in the magnet and complex forms - preferred is casing - mounting mechanism.
• Possible danger related to microscopic parts of magnets pose a threat, when accidentally swallowed, which gains importance in the context of child safety. Furthermore, small elements of these products are able to 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

Optimal lifting capacity of a neodymium magnet – what affects it?

Magnet power was determined for ideal contact conditions, including:

• with the use of a sheet made of low-carbon steel, guaranteeing full magnetic saturation
• with a cross-section of at least 10 mm
• with an ideally smooth touching surface
• with direct contact (without paint)
• under perpendicular application of breakaway force (90-degree angle)
• at conditions approx. 20°C

Determinants of lifting force in real conditions

It is worth knowing that the magnet holding will differ depending on elements below, in order of importance:

• Gap (between the magnet and the plate), as even a microscopic clearance (e.g. 0.5 mm) can cause a decrease in force by up to 50% (this also applies to varnish, rust or debris).
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under shear forces, the holding force drops significantly, often to levels of 20-30% of the nominal value.
• 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 – different alloys attracts identically. High carbon content worsen the interaction with the magnet.
• Surface quality – the more even the surface, the larger the contact zone and stronger the hold. Roughness acts like micro-gaps.
• Thermal factor – hot environment weakens pulling force. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity testing was carried out on a smooth plate of optimal thickness, under a perpendicular pulling force, whereas under shearing force the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate lowers the lifting capacity.