MW 8x20 / N38 - cylindrical magnet

Advantages as well as disadvantages of rare earth magnets.

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

• They have unchanged lifting capacity, and over around 10 years their attraction force decreases symbolically – ~1% (according to theory),
• They show high resistance to demagnetization induced by external magnetic fields,
• By applying a decorative coating of nickel, the element has an professional look,
• The surface of neodymium magnets generates a powerful magnetic field – this is one of their assets,
• Through (adequate) combination of ingredients, they can achieve high thermal resistance, allowing for functioning at temperatures reaching 230°C and above...
• Thanks to versatility in constructing and the ability to adapt to unusual requirements,
• Wide application in modern industrial fields – they are commonly used in hard drives, electromotive mechanisms, medical equipment, also technologically advanced constructions.
• Thanks to concentrated force, small magnets offer high operating force, occupying minimum space,

Disadvantages of neodymium magnets:

• Brittleness is one of their disadvantages. Upon strong impact they can break. We advise keeping them in a strong case, which not only protects them against impacts but also raises their durability
• Neodymium magnets decrease their force 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 stability even at temperatures up to 230°C
• Magnets exposed to a humid environment can corrode. Therefore when using outdoors, we recommend using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• Due to limitations in realizing nuts and complex shapes in magnets, we recommend using a housing - magnetic mechanism.
• Possible danger to health – tiny shards of magnets pose a threat, when accidentally swallowed, which is particularly important in the context of child health protection. Furthermore, tiny parts of these products are able to be problematic in diagnostics medical when they are in the body.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum lifting capacity of the magnet – what contributes to it?

Information about lifting capacity is the result of a measurement for ideal contact conditions, including:

• on a base made of structural steel, perfectly concentrating the magnetic flux
• with a cross-section minimum 10 mm
• with a surface perfectly flat
• with total lack of distance (no coatings)
• during detachment in a direction perpendicular to the mounting surface
• at room temperature

Key elements affecting lifting force

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

• Clearance – the presence of any layer (paint, tape, gap) acts as an insulator, which reduces capacity steeply (even by 50% at 0.5 mm).
• Direction of force – highest force is obtained only during pulling at a 90° angle. The force required to slide of the magnet along the surface is usually several times lower (approx. 1/5 of the lifting capacity).
• Steel thickness – too thin steel does not close the flux, causing part of the power to be escaped to the other side.
• Chemical composition of the base – low-carbon steel attracts best. Higher carbon content reduce magnetic permeability and lifting capacity.
• Base smoothness – the smoother and more polished the plate, the larger the contact zone and stronger the hold. Unevenness creates an air distance.
• Thermal conditions – neodymium magnets have a negative temperature coefficient. When it is hot they are weaker, and in frost gain strength (up to a certain limit).

* Lifting capacity was determined by applying a smooth steel plate of suitable thickness (min. 20 mm), under vertically applied force, in contrast under parallel forces the load capacity is reduced by as much as fivefold. Additionally, even a minimal clearance {between} the magnet and the plate decreases the lifting capacity.