UMH 25x8x45 [M5] / N38 - magnetic holder with hook

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They do not lose their even over nearly 10 years – the reduction of lifting capacity is only ~1% (according to tests),
• They show strong resistance to demagnetization from external magnetic fields,
• In other words, due to the glossy nickel coating, the magnet obtains an professional appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the structure),
• The ability for accurate shaping and adjustment to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which enhances their versatility in applications,
• Key role in new technology industries – they find application in hard drives, electric drives, medical equipment and other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in tiny dimensions, which makes them useful in small systems

Disadvantages of rare earth magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to external force, it is advisable to use in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture and enhances its overall resistance,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of synthetic coating for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing threads directly in the magnet,
• Safety concern due to small fragments may arise, in case of ingestion, which is important in the family environments. Additionally, tiny components from these magnets have the potential to interfere with diagnostics after being swallowed,
• Due to a complex production process, their cost is considerably higher,

Magnetic strength at its maximum – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, calculated in the best circumstances, namely:

• 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
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Impact of factors on magnetic holding capacity in practice

Practical lifting force is determined by elements, listed from the most critical to the less 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 was determined with the use of a steel plate with a smooth surface of optimal thickness (min. 20 mm), under vertically applied force, however under attempts to slide the magnet the holding force is lower. In addition, even a slight gap {between} the magnet and the plate decreases the load capacity.