MW 20x18 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their immense pulling force, neodymium magnets offer the following advantages:

• They do not lose their strength around 10 years – the loss of lifting capacity is only ~1% (based on measurements),
• They remain magnetized despite exposure to magnetic surroundings,
• By applying a shiny layer of silver, the element gains a modern look,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• Thanks to the flexibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in various configurations, which expands their functional possibilities,
• Significant impact in new technology industries – they serve a purpose in data storage devices, electromechanical systems, medical equipment as well as sophisticated instruments,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to external force, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from damage and additionally reinforces its overall strength,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (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 wet environment – during outdoor use, we recommend using sealed magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Safety concern due to small fragments may arise, when consumed by mistake, which is notable in the family environments. Furthermore, tiny components from these assemblies might complicate medical imaging when ingested,
• In cases of tight budgets, neodymium magnet cost is a challenge,

Maximum lifting force for a neodymium magnet – what affects it?

The given lifting capacity of the magnet represents the maximum lifting force, assessed under optimal conditions, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• under perpendicular detachment force
• at room temperature

Key elements affecting lifting force

The lifting capacity of a magnet is influenced by in practice key elements, from primary to secondary:

• 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 measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under shearing force the holding force is lower. In addition, even a minimal clearance {between} the magnet and the plate decreases the load capacity.