MP 25x13x4 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets.

Apart from their notable magnetism, neodymium magnets have these key benefits:

• They do not lose magnetism, even over around ten years – the reduction in strength is only ~1% (based on measurements),
• Neodymium magnets are characterized by exceptionally resistant to demagnetization caused by external interference,
• The use of an elegant finish of noble metals (nickel, gold, silver) causes the element to have aesthetics,
• The surface of neodymium magnets generates a concentrated magnetic field – this is one of their assets,
• Through (appropriate) combination of ingredients, they can achieve high thermal resistance, enabling action at temperatures reaching 230°C and above...
• Thanks to modularity in forming and the capacity to customize to complex applications,
• Versatile presence in high-tech industry – they find application in computer drives, electric drive systems, precision medical tools, as well as industrial machines.
• Compactness – despite small sizes they provide effective action, making them ideal for precision applications

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 increases its resistance to damage
• 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 stability even at temperatures up to 230°C
• Magnets exposed to a humid environment can corrode. Therefore during using outdoors, we recommend using waterproof magnets made of rubber, plastic or other material protecting against moisture
• We recommend cover - magnetic mount, due to difficulties in creating nuts inside the magnet and complex forms.
• Potential hazard to health – tiny shards of magnets can be dangerous, in case of ingestion, which is particularly important in the aspect of protecting the youngest. It is also worth noting that tiny parts of these devices 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

Highest magnetic holding force – what it depends on?

Holding force of 2.96 kg is a measurement result executed under standard conditions:

• using a plate made of mild steel, functioning as a ideal flux conductor
• possessing a thickness of minimum 10 mm to ensure full flux closure
• with an ground contact surface
• without the slightest clearance between the magnet and steel
• during detachment in a direction perpendicular to the plane
• at temperature approx. 20 degrees Celsius

Determinants of lifting force in real conditions

Please note that the working load will differ influenced by the following factors, starting with the most relevant:

• Gap (betwixt the magnet and the metal), since even a microscopic distance (e.g. 0.5 mm) results in a decrease in lifting capacity by up to 50% (this also applies to paint, corrosion or debris).
• Pull-off angle – remember that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, 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 generating force.
• Chemical composition of the base – low-carbon steel attracts best. Alloy admixtures lower magnetic permeability and lifting capacity.
• Plate texture – smooth surfaces ensure maximum contact, which improves field saturation. Uneven metal reduce efficiency.
• Temperature influence – high temperature weakens pulling force. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under shearing force the load capacity is reduced by as much as 75%. Additionally, even a minimal clearance {between} the magnet and the plate lowers the load capacity.