MW 8x20 / N38 - cylindrical magnet

Pros and cons of rare earth magnets.

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

• They virtually do not lose strength, because even after ten years the performance loss is only ~1% (according to literature),
• Neodymium magnets remain remarkably resistant to loss of magnetic properties caused by external field sources,
• A magnet with a shiny nickel surface is more attractive,
• Neodymium magnets create maximum magnetic induction on a contact point, which increases force concentration,
• 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 custom forming as well as modifying to atypical requirements,
• Universal use in innovative solutions – they serve a role in HDD drives, motor assemblies, precision medical tools, also technologically advanced constructions.
• Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which enables their usage in compact constructions

Disadvantages of neodymium magnets:

• They are prone to damage upon too strong impacts. To avoid cracks, it is worth protecting magnets in special housings. Such protection not only protects the magnet but also improves its resistance to damage
• We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• When exposed to humidity, magnets usually rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which prevent oxidation as well as corrosion.
• Limited ability of creating nuts in the magnet and complicated shapes - preferred is cover - magnetic holder.
• Potential hazard related to microscopic parts of magnets can be dangerous, in case of ingestion, which becomes key in the context of child safety. Furthermore, small elements of these products are able to disrupt the diagnostic process medical after entering the body.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum lifting force for a neodymium magnet – what affects it?

Holding force of 8.85 kg is a result of laboratory testing conducted under standard conditions:

• with the contact of a sheet made of special test steel, ensuring full magnetic saturation
• possessing a thickness of min. 10 mm to avoid saturation
• with an ideally smooth touching surface
• under conditions of gap-free contact (metal-to-metal)
• under axial force direction (90-degree angle)
• at conditions approx. 20°C

Determinants of lifting force in real conditions

In practice, the actual lifting capacity depends on a number of factors, ranked from crucial:

• Gap between surfaces – every millimeter of distance (caused e.g. by varnish or unevenness) significantly weakens the pulling force, often by half at just 0.5 mm.
• Angle of force application – highest force is reached only during pulling at a 90° angle. The resistance to sliding of the magnet along the surface is standardly several times lower (approx. 1/5 of the lifting capacity).
• Substrate thickness – for full efficiency, the steel must be adequately massive. Paper-thin metal limits the attraction force (the magnet "punches through" it).
• Material type – the best choice is pure iron steel. Cast iron may attract less.
• Surface structure – the smoother and more polished the plate, the better the adhesion and stronger the hold. Roughness acts like micro-gaps.
• Temperature influence – hot environment weakens magnetic field. Too high temperature can permanently damage the magnet.

* Lifting capacity was determined with the use of a smooth steel plate of suitable thickness (min. 20 mm), under vertically applied force, whereas under shearing force the load capacity is reduced by as much as 5 times. Moreover, even a slight gap {between} the magnet’s surface and the plate reduces the lifting capacity.