UMT 20x25 white / N38 - board holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior magnetic energy, neodymium magnets have these key benefits:

• They do not lose their even during nearly ten years – the reduction of power is only ~1% (theoretically),
• They remain magnetized despite exposure to strong external fields,
• By applying a bright layer of nickel, the element gains a sleek look,
• They exhibit extremely high levels of magnetic induction near the outer area 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),
• The ability for accurate shaping as well as adjustment to individual needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which enhances their versatility in applications,
• Significant impact in cutting-edge sectors – they are used in hard drives, rotating machines, diagnostic apparatus along with technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in small dimensions, which allows for use in compact constructions

Disadvantages of magnetic elements:

• They can break when subjected to a sudden impact. If the magnets are exposed to physical collisions, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks and additionally reinforces its overall strength,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (influenced by the magnet’s profile). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a moist environment. For outdoor use, we recommend using waterproof magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is restricted,
• Health risk due to small fragments may arise, if ingested accidentally, which is notable in the context of child safety. Furthermore, small elements from these assemblies may complicate medical imaging if inside the body,
• High unit cost – neodymium magnets are pricier 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 pulling force of the magnet corresponds to the maximum force, measured in a perfect environment, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with no separation
• in a perpendicular direction of force
• under standard ambient temperature

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) 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 performed on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, however under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.