MP 5x2.7/1.2x5 S / N38 - ring magnet

Pros as well as cons of rare earth magnets.

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

• They have stable power, and over nearly ten years their attraction force decreases symbolically – ~1% (in testing),
• They do not lose their magnetic properties even under strong external field,
• The use of an elegant finish of noble metals (nickel, gold, silver) causes the element to present itself better,
• They feature high magnetic induction at the operating surface, which affects their effectiveness,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Thanks to flexibility in forming and the capacity to adapt to unusual requirements,
• Significant place in innovative solutions – they are used in mass storage devices, drive modules, medical devices, as well as technologically advanced constructions.
• Thanks to their power density, small magnets offer high operating force, in miniature format,

Cons of neodymium magnets and proposals for their use:

• To avoid cracks under impact, we recommend using special steel housings. Such a solution protects the magnet and simultaneously improves its durability.
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we recommend our specialized [AH] magnets, which work effectively even at 230°C.
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• Limited possibility of creating nuts in the magnet and complex shapes - preferred is a housing - magnetic holder.
• Possible danger related to microscopic parts of magnets can be dangerous, if swallowed, which is particularly important in the context of child safety. Furthermore, small elements of these products are able to disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum lifting capacity of the magnet – what contributes to it?

Breakaway force was defined for the most favorable conditions, including:

• with the use of a sheet made of special test steel, ensuring maximum field concentration
• whose transverse dimension reaches at least 10 mm
• with an ideally smooth contact surface
• with direct contact (without impurities)
• under vertical force direction (90-degree angle)
• in stable room temperature

Lifting capacity in practice – influencing factors

In real-world applications, the actual holding force is determined by several key aspects, listed from most significant:

• Gap (between the magnet and the plate), since even a microscopic distance (e.g. 0.5 mm) can cause a drastic drop in force by up to 50% (this also applies to paint, corrosion or dirt).
• Angle of force application – maximum parameter is obtained only during perpendicular pulling. The resistance to sliding of the magnet along the plate is usually several times smaller (approx. 1/5 of the lifting capacity).
• Base massiveness – too thin sheet does not accept the full field, causing part of the flux to be escaped into the air.
• Material composition – not every steel reacts the same. Alloy additives weaken the interaction with the magnet.
• Plate texture – smooth surfaces ensure maximum contact, which improves field saturation. Uneven metal weaken the grip.
• Thermal factor – hot environment weakens magnetic field. Too high temperature can permanently demagnetize the magnet.

* Lifting capacity was measured by applying a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, in contrast under shearing force the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the load capacity.