UMC 32x11/3x8 / N38 - cylindrical magnetic holder

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They do not lose their even over nearly 10 years – the decrease of strength is only ~1% (according to tests),
• Their ability to resist magnetic interference from external fields is among the best,
• The use of a decorative silver surface provides a refined finish,
• They possess significant magnetic force measurable at the magnet’s surface,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• With the option for fine forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving design adaptation,
• Wide application in new technology industries – they serve a purpose in HDDs, rotating machines, clinical machines as well as sophisticated instruments,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, with minimal size,

Disadvantages of neodymium magnets:

• They can break 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 fracture and enhances its overall strength,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on form). 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 moist environment. If exposed to rain, we recommend using moisture-resistant magnets, such as those made of rubber,
• Limited ability to create threads in the magnet – the use of a magnetic holder is recommended,
• Safety concern from tiny pieces may arise, especially if swallowed, which is crucial in the protection of children. Moreover, minuscule fragments from these devices might complicate medical imaging once in the system,
• Due to the price of neodymium, their cost is above average,

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The given lifting capacity of the magnet represents the maximum lifting force, determined in ideal conditions, namely:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Determinants of practical lifting force of a magnet

Practical lifting force is determined by elements, by priority:

• Air gap between the magnet and the plate, because 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.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate reduces the load capacity.