AM ucho [M8] - magnetic accessories

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their pulling strength, neodymium magnets provide the following advantages:

• They do not lose their strength nearly ten years – the loss of strength is only ~1% (theoretically),
• They remain magnetized despite exposure to magnetic surroundings,
• Because of the reflective layer of silver, the component looks high-end,
• Magnetic induction on the surface of these magnets is impressively powerful,
• 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 magnetic form),
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which broadens their usage potential,
• Wide application in cutting-edge sectors – they serve a purpose in computer drives, rotating machines, clinical machines along with technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to external force, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks and reinforces its overall strength,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on height). 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, especially when used outside, we recommend using waterproof magnets, such as those made of rubber,
• Limited ability to create complex details in the magnet – the use of a housing is recommended,
• Possible threat from tiny pieces may arise, if ingested accidentally, which is significant in the context of child safety. It should also be noted that miniature parts from these devices have the potential to complicate medical imaging 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

Highest magnetic holding force – what contributes to it?

The given pulling force of the magnet corresponds to the maximum force, determined in ideal conditions, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

Lifting capacity in real conditions – factors

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) can cause 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 measured using a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, in contrast under shearing force the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet and the plate lowers the holding force.