MW 5x4 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their consistent power, neodymium magnets have these key benefits:

• They virtually do not lose strength, because even after 10 years, the decline in efficiency is only ~1% (in laboratory conditions),
• They show strong resistance to demagnetization from external magnetic fields,
• The use of a polished gold surface provides a refined finish,
• They possess strong magnetic force measurable at the magnet’s surface,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• 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 application range,
• Important function in new technology industries – they are utilized in HDDs, rotating machines, medical equipment along with other advanced devices,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of neodymium magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to mechanical hits, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture while also strengthens its overall resistance,
• They lose strength at extreme temperatures. Most neodymium magnets experience permanent reduction in strength when heated above 80°C (depending on the shape and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a wet environment. If exposed to rain, we recommend using waterproof magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is difficult,
• Health risk from tiny pieces may arise, when consumed by mistake, which is significant in the health of young users. It should also be noted that miniature parts from these products can interfere with diagnostics if inside the body,
• In cases of tight budgets, neodymium magnet cost may be a barrier,

Maximum holding power of the magnet – what affects it?

The given lifting capacity of the magnet represents the maximum lifting force, calculated in a perfect environment, that is:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• in a perpendicular direction of force
• at room temperature

Practical aspects of lifting capacity – factors

The lifting capacity of a magnet is influenced by in practice key elements, according to their importance:

• Air gap between the magnet and the plate, as 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 attempts to slide the magnet the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate decreases the lifting capacity.