MPL 40x10x18 / N38 - lamellar magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their remarkable magnetic power, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• Their ability to resist magnetic interference from external fields is impressive,
• Because of the reflective layer of silver, the component looks aesthetically refined,
• They have exceptional magnetic induction on the surface of the magnet,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the structure),
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which increases their application range,
• Key role in new technology industries – they are used in hard drives, electromechanical systems, medical equipment or even sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to mechanical hits, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall resistance,
• They lose strength at high temperatures. Most neodymium magnets experience permanent reduction 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 damp air can degrade. Therefore, for outdoor applications, we suggest waterproof types made of rubber,
• Limited ability to create precision features in the magnet – the use of a external casing is recommended,
• Possible threat from tiny pieces may arise, when consumed by mistake, which is crucial in the context of child safety. Moreover, miniature parts from these assemblies have the potential to disrupt scanning when ingested,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Best holding force of the magnet in ideal parameters – what it depends on?

The given lifting capacity of the magnet represents the maximum lifting force, determined in a perfect environment, namely:

• 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 refined outer layer
• with no separation
• in a perpendicular direction of force
• at room temperature

Practical lifting capacity: influencing factors

The lifting capacity of a magnet depends on in practice the following factors, ordered from most important to least significant:

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

* Lifting capacity was measured by applying a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, however under parallel forces the lifting capacity is smaller. Additionally, even a small distance {between} the magnet’s surface and the plate lowers the lifting capacity.