MW 15x4 / N38 - cylindrical magnet

Advantages as well as disadvantages of rare earth magnets.

Besides their magnetic performance, 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),
• They do not lose their magnetic properties even under external field action,
• The use of an aesthetic finish of noble metals (nickel, gold, silver) causes the element to have aesthetics,
• Magnets exhibit extremely high magnetic induction on the surface,
• Thanks to resistance to high temperature, they are capable of working (depending on the form) even at temperatures up to 230°C and higher...
• Thanks to flexibility in shaping and the ability to modify to unusual requirements,
• Key role in modern industrial fields – they are used in HDD drives, brushless drives, advanced medical instruments, as well as modern systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in small dimensions, which allows their use in compact constructions

Characteristics of disadvantages of neodymium magnets and ways of using them

• Brittleness is one of their disadvantages. Upon strong impact they can break. We recommend keeping them in a steel housing, which not only protects them against impacts but also increases their durability
• Neodymium magnets lose their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material resistant to moisture, when using outdoors
• Due to limitations in producing nuts and complicated forms in magnets, we recommend using cover - magnetic mount.
• Health risk resulting from small fragments of magnets pose a threat, in case of ingestion, which becomes key in the context of child safety. Furthermore, tiny parts of these products are able to complicate diagnosis medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Maximum lifting force for a neodymium magnet – what affects it?

Breakaway force is the result of a measurement for the most favorable conditions, assuming:

• on a base made of structural steel, perfectly concentrating the magnetic field
• whose thickness reaches at least 10 mm
• characterized by lack of roughness
• without the slightest air gap between the magnet and steel
• for force acting at a right angle (in the magnet axis)
• at ambient temperature room level

What influences lifting capacity in practice

Bear in mind that the magnet holding may be lower influenced by the following factors, in order of importance:

• Air gap (between the magnet and the metal), since even a tiny distance (e.g. 0.5 mm) results in a decrease in force by up to 50% (this also applies to paint, rust or dirt).
• Angle of force application – maximum parameter is available only during perpendicular pulling. The force required to slide of the magnet along the plate is standardly several 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. Higher carbon content reduce magnetic permeability and holding force.
• Smoothness – ideal contact is obtained only on polished steel. Any scratches and bumps create air cushions, weakening the magnet.
• Thermal factor – high temperature weakens pulling force. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity testing was conducted on plates with a smooth surface of suitable thickness, under perpendicular forces, whereas under parallel forces the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the holding force.