MW 38x15 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• They do not lose their magnetism, even after approximately 10 years – the reduction of lifting capacity is only ~1% (based on measurements),
• They protect against demagnetization induced by external magnetic fields remarkably well,
• In other words, due to the glossy gold coating, the magnet obtains an professional appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for tailored forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving design adaptation,
• Important function in advanced technical fields – they serve a purpose in data storage devices, electric drives, diagnostic apparatus and sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which makes them useful in small systems

Disadvantages of rare earth magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to physical collisions, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage , and at the same time increases its overall resistance,
• High temperatures may significantly reduce the strength of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on size). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• They rust in a damp environment. If exposed to rain, we recommend using encapsulated magnets, such as those made of polymer,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing threads directly in the magnet,
• Possible threat linked to microscopic shards may arise, when consumed by mistake, which is notable in the context of child safety. Furthermore, miniature parts from these assemblies can disrupt scanning when ingested,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum holding power of the magnet – what it depends on?

The given holding capacity of the magnet represents the highest holding force, determined under optimal conditions, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• of a thickness of at least 10 mm
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• under standard ambient temperature

Lifting capacity in practice – influencing factors

The lifting capacity of a magnet is determined by in practice the following factors, according to their importance:

• 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 determined by applying a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular detachment force, whereas under shearing force the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate reduces the lifting capacity.