UMT 12x20 white / N38 - board holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their consistent holding force, neodymium magnets have these key benefits:

• They retain their attractive force for nearly ten years – the loss is just ~1% (according to analyses),
• They remain magnetized despite exposure to magnetic surroundings,
• Because of the lustrous layer of silver, the component looks visually appealing,
• They have very high magnetic induction on the surface of the magnet,
• Thanks to their enhanced temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• The ability for custom shaping or adaptation to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which extends the scope of their use cases,
• Important function in new technology industries – they serve a purpose in HDDs, electric drives, healthcare devices as well as other advanced devices,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to mechanical hits, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture and additionally enhances its overall robustness,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on shape). 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,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of plastic for outdoor use,
• Limited ability to create threads in the magnet – the use of a magnetic holder is recommended,
• Safety concern due to small fragments may arise, when consumed by mistake, which is crucial in the context of child safety. Moreover, small elements 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 may limit large-scale applications

Maximum lifting capacity of the magnet – what affects it?

The given strength of the magnet means the optimal strength, assessed under optimal conditions, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a refined outer layer
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet is determined by in practice key elements, according to their 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.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the holding force is lower. In addition, even a small distance {between} the magnet’s surface and the plate lowers the holding force.