MP 15x7/3.5x3 / N38 - ring magnet

Pros as well as cons of neodymium magnets.

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

• They virtually do not lose strength, because even after ten years the decline in efficiency is only ~1% (based on calculations),
• Magnets perfectly protect themselves against loss of magnetization caused by foreign field sources,
• A magnet with a smooth gold surface looks better,
• The surface of neodymium magnets generates a strong magnetic field – this is a distinguishing feature,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• Considering the option of flexible shaping and adaptation to custom requirements, NdFeB magnets can be modeled in a broad palette of shapes and sizes, which amplifies use scope,
• Key role in future technologies – they find application in HDD drives, electric motors, medical equipment, and other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which enables their usage in miniature devices

Problematic aspects of neodymium magnets and proposals for their use:

• At very strong impacts they can break, therefore we advise placing them in special holders. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• Neodymium magnets demagnetize 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 advise using waterproof magnets made of rubber, plastic or other material resistant to moisture, when using outdoors
• Limited ability of making threads in the magnet and complex shapes - recommended is cover - magnet mounting.
• Possible danger to health – tiny shards of magnets pose a threat, if swallowed, which gains importance in the aspect of protecting the youngest. Furthermore, small components of these devices are able to be problematic in diagnostics medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Optimal lifting capacity of a neodymium magnet – what affects it?

The declared magnet strength represents the maximum value, recorded under laboratory conditions, namely:

• using a base made of low-carbon steel, functioning as a ideal flux conductor
• with a cross-section no less than 10 mm
• with a surface free of scratches
• under conditions of gap-free contact (metal-to-metal)
• during pulling in a direction vertical to the plane
• at ambient temperature room level

Practical aspects of lifting capacity – factors

Bear in mind that the application force may be lower subject to elements below, starting with the most relevant:

• Space between magnet and steel – even a fraction of a millimeter of separation (caused e.g. by veneer or unevenness) drastically reduces the pulling force, often by half at just 0.5 mm.
• Force direction – catalog parameter refers to detachment vertically. When applying parallel force, the magnet holds significantly lower power (typically approx. 20-30% of maximum force).
• Wall thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of generating force.
• Material composition – not every steel attracts identically. High carbon content worsen the interaction with the magnet.
• Surface quality – the smoother and more polished the surface, the larger the contact zone and higher the lifting capacity. Roughness acts like micro-gaps.
• Thermal factor – hot environment reduces pulling force. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet and the plate reduces the holding force.