MP 40x10.4/5.5x5 / N38 - ring magnet

Pros and cons of NdFeB magnets.

Besides their tremendous magnetic power, neodymium magnets offer the following advantages:

• They have stable power, and over nearly 10 years their performance decreases symbolically – ~1% (in testing),
• They have excellent resistance to magnetism drop when exposed to opposing magnetic fields,
• Thanks to the shimmering finish, the surface of Ni-Cu-Ni, gold, or silver-plated gives an clean appearance,
• Neodymium magnets achieve maximum magnetic induction on a their surface, which increases force concentration,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to flexibility in shaping and the ability to customize to individual projects,
• Huge importance in modern technologies – they find application in data components, brushless drives, precision medical tools, also modern systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in small dimensions, which enables their usage in miniature devices

Characteristics of disadvantages of neodymium magnets and proposals for their use:

• At strong impacts they can break, therefore we recommend placing them in steel cases. A metal housing provides additional protection against damage and increases the magnet's durability.
• We warn that neodymium magnets can lose their power at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• They oxidize in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Due to limitations in realizing threads and complex forms in magnets, we propose using a housing - magnetic mount.
• Potential hazard to health – tiny shards of magnets pose a threat, if swallowed, which gains importance in the context of child safety. Additionally, small components of these products are able to be problematic in diagnostics medical when they are in the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Highest magnetic holding force – what contributes to it?

Information about lifting capacity was determined for optimal configuration, including:

• on a block made of structural steel, perfectly concentrating the magnetic field
• possessing a thickness of minimum 10 mm to avoid saturation
• with an polished contact surface
• under conditions of gap-free contact (surface-to-surface)
• for force acting at a right angle (pull-off, not shear)
• at ambient temperature room level

Determinants of practical lifting force of a magnet

In real-world applications, the real power is determined by several key aspects, ranked from crucial:

• Gap (between the magnet and the plate), since even a microscopic clearance (e.g. 0.5 mm) leads to a drastic drop in lifting capacity by up to 50% (this also applies to varnish, rust or dirt).
• Load vector – maximum parameter is obtained only during perpendicular pulling. The shear force of the magnet along the plate is usually many times smaller (approx. 1/5 of the lifting capacity).
• Metal thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field penetrates through instead of generating force.
• Material composition – different alloys reacts the same. Alloy additives worsen the interaction with the magnet.
• Plate texture – ground elements guarantee perfect abutment, which increases field saturation. Uneven metal reduce efficiency.
• Thermal factor – high temperature weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.