MW 14x10 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They do not lose their even over around 10 years – the decrease of strength is only ~1% (based on measurements),
• They protect against demagnetization induced by ambient electromagnetic environments remarkably well,
• The use of a mirror-like nickel surface provides a eye-catching finish,
• They have extremely strong magnetic induction on the surface of the magnet,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for precise shaping or adjustment to custom needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Wide application in modern technologies – they are used in hard drives, electromechanical systems, diagnostic apparatus and high-tech tools,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture , and at the same time reinforces its overall strength,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent reduction in strength when heated above 80°C (depending on the dimensions and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of rubber for outdoor use,
• Limited ability to create threads in the magnet – the use of a external casing is recommended,
• Possible threat linked to microscopic shards may arise, in case of ingestion, which is crucial in the family environments. Additionally, minuscule fragments from these assemblies may disrupt scanning if inside the body,
• Due to a complex production process, their cost is relatively high,

Optimal lifting capacity of a neodymium magnet – what affects it?

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

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a smooth surface
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Lifting capacity in practice – influencing factors

The lifting capacity of a magnet is influenced by in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, since 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.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under shearing force the load capacity is reduced by as much as 75%. Moreover, even a slight gap {between} the magnet and the plate lowers the lifting capacity.