MW 8x20 / N38 - cylindrical magnet

Strengths as well as weaknesses of neodymium magnets.

Apart from their consistent power, neodymium magnets have these key benefits:

• Their magnetic field remains stable, and after around 10 years it drops only by ~1% (according to research),
• Magnets effectively resist against loss of magnetization caused by external fields,
• Thanks to the glossy finish, the coating of nickel, gold, or silver-plated gives an elegant appearance,
• Magnetic induction on the top side of the magnet is exceptional,
• Thanks to resistance to high temperature, they are able to function (depending on the form) even at temperatures up to 230°C and higher...
• Thanks to modularity in shaping and the ability to customize to complex applications,
• Key role in future technologies – they serve a role in HDD drives, electromotive mechanisms, advanced medical instruments, and complex engineering applications.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which enables their usage in miniature devices

Disadvantages of neodymium magnets:

• At very strong impacts they can break, therefore we advise placing them in strong housings. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• Neodymium magnets decrease their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• When exposed to humidity, magnets usually rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation and corrosion.
• Limited ability of making threads in the magnet and complex shapes - preferred is a housing - magnetic holder.
• Health risk related to microscopic parts of magnets can be dangerous, when accidentally swallowed, which becomes key in the context of child safety. It is also worth noting that small elements of these devices are able to disrupt the diagnostic process medical in case of swallowing.
• Due to expensive raw materials, their price is relatively high,

Highest magnetic holding force – what it depends on?

Information about lifting capacity was determined for ideal contact conditions, taking into account:

• using a base made of low-carbon steel, serving as a circuit closing element
• possessing a thickness of minimum 10 mm to avoid saturation
• with a surface perfectly flat
• under conditions of no distance (metal-to-metal)
• under axial force direction (90-degree angle)
• in stable room temperature

Determinants of lifting force in real conditions

Holding efficiency is affected by working environment parameters, such as (from most important):

• Distance (between the magnet and the plate), because even a very small clearance (e.g. 0.5 mm) can cause a drastic drop in force by up to 50% (this also applies to paint, corrosion or dirt).
• Direction of force – highest force is obtained only during perpendicular pulling. The shear force of the magnet along the surface is usually many times smaller (approx. 1/5 of the lifting capacity).
• Element thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet limits the attraction force (the magnet "punches through" it).
• Steel type – mild steel attracts best. Alloy steels decrease magnetic permeability and lifting capacity.
• Surface condition – smooth surfaces ensure maximum contact, which improves field saturation. Uneven metal reduce efficiency.
• Operating temperature – neodymium magnets have a negative temperature coefficient. At higher temperatures they lose power, and at low temperatures gain strength (up to a certain limit).

* Holding force was tested on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the holding force.