UMS 36x10.5x6.5x8 / N38 - conical magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They virtually do not lose strength, because even after ten years, the decline in efficiency is only ~1% (according to literature),
• They are very resistant to demagnetization caused by external magnetic sources,
• By applying a shiny layer of nickel, the element gains a sleek look,
• They have extremely strong magnetic induction on the surface of the magnet,
• Thanks to their high temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which expands their application range,
• Wide application in new technology industries – they are used in HDDs, electric drives, medical equipment or even high-tech tools,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to physical collisions, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage and enhances its overall strength,
• High temperatures may significantly reduce the strength of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on size). 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 synthetic coating for outdoor use,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is risky,
• Potential hazard due to small fragments may arise, in case of ingestion, which is notable in the protection of children. Additionally, tiny components from these assemblies may disrupt scanning if inside the body,
• Due to a complex production process, their cost is considerably higher,

Magnetic strength at its maximum – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, assessed in ideal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• with vertical force applied
• in normal thermal conditions

What influences lifting capacity in practice

The lifting capacity of a magnet is determined by in practice key elements, 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) 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 carried out on plates with a smooth surface of optimal thickness, under perpendicular forces, in contrast under shearing force the load capacity is reduced by as much as 5 times. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the holding force.