MW 80x30 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their stability, neodymium magnets are valued for these benefits:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (according to literature),
• They show superior resistance to demagnetization from external magnetic fields,
• Because of the reflective layer of gold, the component looks aesthetically refined,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to form),
• Thanks to the freedom in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in various configurations, which increases their application range,
• Important function in modern technologies – they are utilized in HDDs, rotating machines, clinical machines or even sophisticated instruments,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of NdFeB magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to external force, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and additionally strengthens its overall robustness,
• They lose field intensity at increased temperatures. Most neodymium magnets experience permanent degradation 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 humidity can rust. Therefore, for outdoor applications, we recommend waterproof types made of coated materials,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing complex structures directly in the magnet,
• Safety concern linked to microscopic shards may arise, in case of ingestion, which is notable in the protection of children. It should also be noted that miniature parts from these devices might complicate medical imaging once in the system,
• In cases of large-volume purchasing, neodymium magnet cost may be a barrier,

Detachment force of the magnet in optimal conditions – what it depends on?

The given strength of the magnet corresponds to the optimal strength, calculated in ideal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• at room temperature

Lifting capacity in real conditions – factors

Practical lifting force is dependent on elements, 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 measured using a polished steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, whereas under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet and the plate lowers the load capacity.