MW 8x10 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They do not lose their even over around 10 years – the decrease of lifting capacity is only ~1% (based on measurements),
• They are extremely resistant to demagnetization caused by external field interference,
• By applying a bright layer of nickel, the element gains a sleek look,
• They possess intense magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• Thanks to the flexibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in diverse shapes and sizes, which expands their application range,
• Wide application in cutting-edge sectors – they find application in data storage devices, electric drives, healthcare devices along with other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They are fragile when subjected to a sudden 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 damage and enhances its overall robustness,
• Magnets lose magnetic efficiency when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a humid environment. For outdoor use, we recommend using sealed magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is restricted,
• Safety concern linked to microscopic shards may arise, in case of ingestion, which is important in the family environments. Furthermore, small elements from these devices might interfere with diagnostics once in the system,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Maximum lifting force for a neodymium magnet – what contributes to it?

The given strength of the magnet corresponds to the optimal strength, measured in ideal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• with vertical force applied
• at room temperature

Lifting capacity in real conditions – factors

The lifting capacity of a magnet depends on 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.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under shearing force the lifting capacity is smaller. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the lifting capacity.