MP 12x8/4x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets.

Besides their immense pulling force, neodymium magnets offer the following advantages:

• They have constant strength, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• They do not lose their magnetic properties even under strong external field,
• A magnet with a shiny silver surface has better aesthetics,
• The surface of neodymium magnets generates a concentrated magnetic field – this is a distinguishing feature,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Possibility of exact machining and adjusting to concrete needs,
• Fundamental importance in high-tech industry – they are commonly used in hard drives, electric motors, medical devices, and modern systems.
• Relatively small size with high pulling force – neodymium magnets offer high power in compact dimensions, which enables their usage in miniature devices

What to avoid - cons of neodymium magnets: weaknesses and usage proposals

• To avoid cracks upon strong impacts, we suggest using special steel housings. Such a solution secures the magnet and simultaneously improves its durability.
• Neodymium magnets lose power when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of strength (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• We suggest a housing - magnetic holder, due to difficulties in realizing threads inside the magnet and complex shapes.
• Health risk related to microscopic parts of magnets pose a threat, when accidentally swallowed, which becomes key in the context of child safety. It is also worth noting that tiny parts of these magnets are able to be problematic in diagnostics medical when they are in the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Magnetic strength at its maximum – what affects it?

Holding force of 0.68 kg is a result of laboratory testing conducted under the following configuration:

• on a block made of structural steel, optimally conducting the magnetic field
• whose transverse dimension is min. 10 mm
• with an ground touching surface
• under conditions of gap-free contact (surface-to-surface)
• under perpendicular application of breakaway force (90-degree angle)
• in temp. approx. 20°C

What influences lifting capacity in practice

Effective lifting capacity impacted by specific conditions, mainly (from most important):

• Air gap (between the magnet and the metal), as even a tiny distance (e.g. 0.5 mm) can cause a decrease in lifting capacity by up to 50% (this also applies to paint, corrosion or debris).
• Loading method – declared lifting capacity refers to pulling vertically. When attempting to slide, the magnet holds significantly lower power (typically approx. 20-30% of maximum force).
• Plate thickness – too thin sheet does not close the flux, causing part of the flux to be wasted to the other side.
• Material type – the best choice is high-permeability steel. Cast iron may have worse magnetic properties.
• Surface structure – the more even the plate, the better the adhesion and higher the lifting capacity. Roughness creates an air distance.
• Temperature – temperature increase causes a temporary drop of force. It is worth remembering the thermal limit for a given model.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet and the plate decreases the holding force.