MW 8x20 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their superior magnetism, neodymium magnets have these key benefits:

• Their power remains stable, and after around ten years, it drops only by ~1% (according to research),
• They protect against demagnetization induced by ambient electromagnetic environments effectively,
• Because of the lustrous layer of silver, the component looks high-end,
• The outer field strength of the magnet shows advanced magnetic properties,
• With the right combination of magnetic alloys, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the design),
• Thanks to the possibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in various configurations, which increases their functional possibilities,
• Wide application in cutting-edge sectors – they are utilized in hard drives, electric motors, medical equipment along with other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which allows for use in small systems

Disadvantages of rare earth magnets:

• They are fragile when subjected to a powerful impact. If the magnets are exposed to external force, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks and additionally increases its overall resistance,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to moisture can rust. Therefore, for outdoor applications, we recommend waterproof types made of plastic,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is restricted,
• Health risk due to small fragments may arise, when consumed by mistake, which is notable in the health of young users. Additionally, tiny components from these products have the potential to interfere with diagnostics when ingested,
• Due to the price of neodymium, their cost is relatively high,

Maximum lifting capacity of the magnet – what affects it?

The given holding capacity of the magnet means the highest holding force, calculated in ideal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a polished side
• in conditions of no clearance
• under perpendicular detachment force
• under standard ambient temperature

Practical lifting capacity: influencing factors

The lifting capacity of a magnet is influenced by in practice key elements, ordered from most important to least significant:

• Air gap between the magnet and the plate, as even a very small distance (e.g. 0.5 mm) causes a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Lifting capacity testing was conducted on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, however under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.