MW 5x1 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional field intensity, neodymium magnets offer the following advantages:

• They have constant strength, and over around 10 years their performance decreases symbolically – ~1% (in testing),
• They remain magnetized despite exposure to magnetic surroundings,
• Because of the brilliant layer of nickel, the component looks aesthetically refined,
• The outer field strength of the magnet shows elevated magnetic properties,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to build),
• Thanks to the possibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in various configurations, which broadens their functional possibilities,
• Important function in modern technologies – they serve a purpose in HDDs, electric motors, healthcare devices and high-tech tools,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to physical collisions, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks while also enhances its overall resistance,
• They lose strength at elevated temperatures. Most neodymium magnets experience permanent reduction in strength when heated above 80°C (depending on the shape and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a humid environment, especially when used outside, we recommend using sealed magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is difficult,
• Health risk from tiny pieces may arise, if ingested accidentally, which is important in the family environments. It should also be noted that miniature parts from these magnets can disrupt scanning if inside the body,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Maximum holding power of the magnet – what affects it?

The given lifting capacity of the magnet means the maximum lifting force, determined under optimal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• under standard ambient temperature

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet is determined by in practice the following factors, according to their importance:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) can cause 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.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the load capacity is reduced by as much as 5 times. In addition, even a small distance {between} the magnet’s surface and the plate reduces the load capacity.