UMC 25x6/4x8 / N38 - cylindrical magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their stability, neodymium magnets are valued for these benefits:

• They virtually do not lose power, because even after ten years, the decline in efficiency is only ~1% (in laboratory conditions),
• They protect against demagnetization induced by external magnetic influence remarkably well,
• By applying a reflective layer of gold, the element gains a sleek look,
• The outer field strength of the magnet shows advanced magnetic properties,
• Thanks to their enhanced temperature resistance, they can operate (depending on the geometry) even at temperatures up to 230°C or more,
• Thanks to the possibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in various configurations, which broadens their application range,
• Key role in advanced technical fields – they are used in HDDs, electric drives, clinical machines along with sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of rare earth magnets:

• They can break when subjected to a strong 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 breakage while also reinforces its overall robustness,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of protective material for outdoor use,
• Limited ability to create internal holes in the magnet – the use of a mechanical support is recommended,
• Safety concern due to small fragments may arise, especially if swallowed, which is significant in the health of young users. Moreover, minuscule fragments from these assemblies might interfere with diagnostics when ingested,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum lifting force for a neodymium magnet – what affects it?

The given holding capacity of the magnet represents the highest holding force, assessed under optimal conditions, that is:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• at room temperature

Practical aspects of lifting capacity – factors

The lifting capacity of a magnet is influenced by in practice the following factors, ordered from most important to least significant:

• Air gap between the magnet and the plate, as 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 testing was performed on plates with a smooth surface of optimal thickness, under perpendicular forces, whereas under parallel forces the load capacity is reduced by as much as fivefold. Additionally, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.