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Advantages and disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their magnetic field remains stable, and after approximately 10 years, it drops only by ~1% (theoretically),
• They remain magnetized despite exposure to magnetic surroundings,
• In other words, due to the metallic silver coating, the magnet obtains an aesthetic appearance,
• The outer field strength of the magnet shows advanced magnetic properties,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the structure),
• The ability for accurate shaping or adjustment to custom needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which extends the scope of their use cases,
• Important function in advanced technical fields – they are used in computer drives, electric drives, clinical machines or even technologically developed systems,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture and increases its overall resistance,
• They lose field intensity at elevated temperatures. Most neodymium magnets experience permanent reduction 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,
• They rust in a damp environment. If exposed to rain, we recommend using waterproof magnets, such as those made of polymer,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Potential hazard from tiny pieces may arise, especially if swallowed, which is important in the health of young users. Moreover, minuscule fragments from these assemblies can complicate medical imaging if inside the body,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

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

The given lifting capacity of the magnet represents the maximum lifting force, determined under optimal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a smooth surface
• with zero air gap
• with vertical force applied
• under standard ambient temperature

Practical aspects of lifting capacity – factors

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

• Air gap between the magnet and the plate, because 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 testing was performed on a smooth plate of optimal thickness, under perpendicular forces, whereas under parallel forces the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the lifting capacity.