MP 16x12x2 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their immense pulling force, neodymium magnets offer the following advantages:

• They have constant strength, and over nearly ten years their attraction force decreases symbolically – ~1% (in testing),
• They show exceptional resistance to demagnetization from outside magnetic sources,
• In other words, due to the shiny nickel coating, the magnet obtains an aesthetic appearance,
• The outer field strength of the magnet shows remarkable magnetic properties,
• Thanks to their exceptional temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for tailored forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Key role in advanced technical fields – they are used in hard drives, rotating machines, healthcare devices as well as sophisticated instruments,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They can break when subjected to a sudden 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 breakage , and at the same time strengthens its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on size). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of rubber for outdoor use,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is risky,
• Possible threat linked to microscopic shards may arise, when consumed by mistake, which is notable in the family environments. It should also be noted that small elements from these assemblies can complicate medical imaging after being swallowed,
• In cases of large-volume purchasing, neodymium magnet cost is a challenge,

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, calculated in the best circumstances, that is:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a polished side
• with no separation
• in a perpendicular direction of force
• under standard ambient temperature

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is affected by these factors, in descending order of 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 measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.