MW 8x20 / N38 - cylindrical magnet

Strengths and weaknesses of NdFeB magnets.

Besides their immense field intensity, neodymium magnets offer the following advantages:

• They retain magnetic properties for around 10 years – the loss is just ~1% (in theory),
• They maintain their magnetic properties even under strong external field,
• A magnet with a shiny silver surface has an effective appearance,
• Magnets have huge magnetic induction on the surface,
• Through (appropriate) combination of ingredients, they can achieve high thermal strength, allowing for action at temperatures reaching 230°C and above...
• Thanks to flexibility in shaping and the capacity to adapt to specific needs,
• Universal use in electronics industry – they are used in mass storage devices, motor assemblies, medical devices, and modern systems.
• Compactness – despite small sizes they provide effective action, making them ideal for precision applications

Drawbacks and weaknesses of neodymium magnets: application proposals

• At very strong impacts they can break, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• Neodymium magnets lose 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 durability even at temperatures up to 230°C
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• Limited ability of creating threads in the magnet and complex forms - preferred is casing - mounting mechanism.
• Health risk to health – tiny shards of magnets can be dangerous, if swallowed, which is particularly important in the context of child safety. Furthermore, tiny parts of these devices are able to be problematic in diagnostics medical in case of swallowing.
• 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?

The load parameter shown refers to the peak performance, measured under ideal test conditions, specifically:

• on a base made of mild steel, effectively closing the magnetic flux
• possessing a massiveness of at least 10 mm to avoid saturation
• characterized by lack of roughness
• under conditions of ideal adhesion (metal-to-metal)
• under vertical application of breakaway force (90-degree angle)
• at standard ambient temperature

Impact of factors on magnetic holding capacity in practice

Real force impacted by working environment parameters, mainly (from priority):

• Gap between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by veneer or unevenness) drastically reduces the pulling force, often by half at just 0.5 mm.
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Wall thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field penetrates through instead of converting into lifting capacity.
• Material composition – different alloys reacts the same. High carbon content weaken the attraction effect.
• Plate texture – smooth surfaces guarantee perfect abutment, which improves force. Rough surfaces weaken the grip.
• Heat – neodymium magnets have a negative temperature coefficient. At higher temperatures they are weaker, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity was assessed using a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular detachment force, in contrast under shearing force the load capacity is reduced by as much as 5 times. Moreover, even a minimal clearance {between} the magnet’s surface and the plate decreases the load capacity.