MW 45x20 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their strength remains stable, and after around ten years, it drops only by ~1% (theoretically),
• They protect against demagnetization induced by external magnetic fields remarkably well,
• Because of the brilliant layer of gold, the component looks visually appealing,
• They have extremely strong magnetic induction on the surface of the magnet,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the structure),
• Thanks to the possibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their usage potential,
• Wide application in advanced technical fields – they are used in computer drives, rotating machines, clinical machines along with sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of magnetic elements:

• They can break when subjected to a strong impact. If the magnets are exposed to mechanical hits, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and additionally reinforces its overall resistance,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (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 damp environment – during outdoor use, we recommend using encapsulated magnets, such as those made of plastic,
• Limited ability to create complex details in the magnet – the use of a housing is recommended,
• Safety concern from tiny pieces may arise, if ingested accidentally, which is crucial in the protection of children. Additionally, tiny components from these magnets can interfere with diagnostics if inside the body,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Maximum holding power of the magnet – what contributes to it?

The given lifting capacity of the magnet means the maximum lifting force, determined in a perfect environment, specifically:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• in a perpendicular direction of force
• under standard ambient temperature

Key elements affecting lifting force

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• Air gap between the magnet and the plate, since 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 testing was conducted on a smooth plate of suitable thickness, under perpendicular forces, in contrast under parallel forces the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the lifting capacity.