MP 5x2.7/1.2x5 C / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They have constant strength, and over around 10 years their attraction force decreases symbolically – ~1% (according to theory),
• They are highly resistant to demagnetization caused by external magnetic fields,
• In other words, due to the metallic gold coating, the magnet obtains an professional appearance,
• They have exceptional magnetic induction on the surface of the magnet,
• With the right combination of materials, they reach significant thermal stability, enabling operation at or above 230°C (depending on the form),
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their usage potential,
• Key role in cutting-edge sectors – they are used in computer drives, electric drives, diagnostic apparatus or even other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which allows for use in small systems

Disadvantages of neodymium magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to external force, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks and reinforces its overall strength,
• They lose magnetic force at elevated temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the form 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 oxidize. Therefore, for outdoor applications, we suggest waterproof types made of non-metallic composites,
• 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 important in the protection of children. It should also be noted that tiny components from these assemblies may complicate medical imaging if inside the body,
• In cases of large-volume purchasing, neodymium magnet cost is a challenge,

Maximum magnetic pulling force – what it depends on?

The given strength of the magnet corresponds to the optimal strength, measured under optimal conditions, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with no separation
• with vertical force applied
• under standard ambient temperature

Determinants of lifting force in real conditions

Practical lifting force is determined by factors, by priority:

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

* Lifting capacity was determined using a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular pulling force, however under shearing force the load capacity is reduced by as much as 5 times. Moreover, even a minimal clearance {between} the magnet and the plate reduces the holding force.