UMN 410x44x15 / N52 - knife holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• Their power is durable, and after around ten years, it drops only by ~1% (theoretically),
• They show exceptional resistance to demagnetization from outside magnetic sources,
• By applying a bright layer of silver, the element gains a sleek look,
• They have very high magnetic induction on the surface of the magnet,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• The ability for precise shaping as well as adaptation to individual needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which extends the scope of their use cases,
• Key role in modern technologies – they find application in HDDs, electric motors, healthcare devices along with technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to physical collisions, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage and additionally increases its overall resistance,
• 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 form). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to damp air can oxidize. Therefore, for outdoor applications, we recommend waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing holes directly in the magnet,
• Safety concern due to small fragments may arise, when consumed by mistake, which is significant in the protection of children. Furthermore, miniature parts from these devices can disrupt scanning when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Highest magnetic holding force – what affects it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, determined under optimal conditions, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• under standard ambient temperature

Lifting capacity in real conditions – factors

Practical lifting force is determined by elements, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, as 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 plates with a smooth surface of optimal thickness, under perpendicular forces, however under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate lowers the lifting capacity.