MP 12x8/4x3 / N38 - ring magnet

Advantages as well as disadvantages of rare earth magnets.

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

• They virtually do not lose power, because even after 10 years the decline in efficiency is only ~1% (based on calculations),
• Neodymium magnets remain highly resistant to loss of magnetic properties caused by magnetic disturbances,
• Thanks to the metallic finish, the surface of Ni-Cu-Ni, gold, or silver gives an modern appearance,
• Magnets are distinguished by impressive magnetic induction on the active area,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
• Thanks to versatility in forming and the ability to modify to complex applications,
• Fundamental importance in advanced technology sectors – they are utilized in hard drives, motor assemblies, 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:

• To avoid cracks upon strong impacts, we recommend using special steel housings. Such a solution secures the magnet and simultaneously increases its durability.
• NdFeB magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of power (a factor is the shape and dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material immune to moisture, in case of application outdoors
• Due to limitations in creating threads and complicated forms in magnets, we propose using casing - magnetic mechanism.
• Potential hazard to health – tiny shards of magnets can be dangerous, in case of ingestion, which becomes key in the context of child safety. It is also worth noting that small components of these devices are able to be problematic in diagnostics medical in case of swallowing.
• Due to complex production process, their price is relatively high,

Best holding force of the magnet in ideal parameters – what affects it?

Holding force of 0.68 kg is a measurement result performed under standard conditions:

• using a sheet made of high-permeability steel, serving as a circuit closing element
• with a thickness no less than 10 mm
• with a plane cleaned and smooth
• with direct contact (no paint)
• for force applied at a right angle (in the magnet axis)
• at ambient temperature room level

Impact of factors on magnetic holding capacity in practice

In practice, the actual lifting capacity results from a number of factors, ranked from the most important:

• Distance – the presence of foreign body (paint, tape, air) acts as an insulator, which lowers capacity rapidly (even by 50% at 0.5 mm).
• Angle of force application – maximum parameter is reached only during perpendicular pulling. The shear force of the magnet along the surface is typically several times smaller (approx. 1/5 of the lifting capacity).
• Element thickness – to utilize 100% power, the steel must be sufficiently thick. Paper-thin metal restricts the lifting capacity (the magnet "punches through" it).
• Material composition – different alloys reacts the same. High carbon content weaken the interaction with the magnet.
• Plate texture – ground elements ensure maximum contact, which increases field saturation. Uneven metal weaken the grip.
• Thermal conditions – NdFeB sinters have a sensitivity to temperature. When it is hot they are weaker, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet and the plate reduces the holding force.