BM 750x180x70 [4x M8] - magnetic beam

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their strong magnetism, neodymium magnets have these key benefits:

• They retain their attractive force for around ten years – the loss is just ~1% (according to analyses),
• They are very resistant to demagnetization caused by external magnetic sources,
• Thanks to the glossy finish and gold coating, they have an visually attractive appearance,
• They have very high magnetic induction on the surface of the magnet,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• The ability for custom shaping or adaptation to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Significant impact in advanced technical fields – they find application in computer drives, electric motors, medical equipment along with technologically developed systems,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a heavy 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 additionally reinforces its overall resistance,
• They lose strength 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,
• Due to corrosion risk in humid conditions, it is common to use sealed magnets made of protective material for outdoor use,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is not feasible,
• Health risk from tiny pieces may arise, when consumed by mistake, which is significant in the protection of children. Furthermore, tiny components from these assemblies have the potential to disrupt scanning after being swallowed,
• Due to expensive raw materials, their cost is above average,

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given strength of the magnet corresponds to the optimal strength, determined in the best circumstances, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is conditioned by the following aspects, arranged from the most important to the least relevant:

• 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.

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under perpendicular forces, however under parallel forces the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate decreases the holding force.