UMS 32x10.5x5.5x8 / N38 - conical magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• Their strength is maintained, and after approximately 10 years, it drops only by ~1% (theoretically),
• They show strong resistance to demagnetization from external field exposure,
• Thanks to the glossy finish and silver coating, they have an elegant appearance,
• Magnetic induction on the surface of these magnets is very strong,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for accurate shaping or customization to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Wide application in cutting-edge sectors – they are used in hard drives, electric motors, healthcare devices as well as high-tech tools,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of neodymium magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to physical collisions, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and additionally increases its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent loss 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 humid environment. For outdoor use, we recommend using sealed magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is risky,
• Health risk linked to microscopic shards may arise, if ingested accidentally, which is crucial in the health of young users. Furthermore, miniature parts from these magnets have the potential to disrupt scanning if inside the body,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given strength of the magnet corresponds to the optimal strength, assessed under optimal conditions, specifically:

• 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
• under perpendicular detachment force
• at room temperature

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is affected by these factors, from crucial to less important:

• 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.

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the load capacity.