UMC 42x7/4x9 / N38 - cylindrical magnetic holder

Pros as well as cons of rare earth magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They do not lose magnetism, even over nearly 10 years – the reduction in lifting capacity is only ~1% (theoretically),
• They feature excellent resistance to weakening of magnetic properties due to opposing magnetic fields,
• A magnet with a smooth silver surface is more attractive,
• Magnets exhibit excellent magnetic induction on the working surface,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can work (depending on the form) even at a temperature of 230°C or more...
• Possibility of accurate creating and adapting to atypical applications,
• Universal use in electronics industry – they are commonly used in HDD drives, electromotive mechanisms, medical devices, as well as other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which enables their usage in compact constructions

Disadvantages of neodymium magnets:

• They are fragile upon too strong impacts. To avoid cracks, it is worth protecting magnets using a steel holder. Such protection not only protects the magnet but also improves its resistance to damage
• Neodymium magnets decrease their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• They oxidize in a humid environment. For use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• Due to limitations in realizing threads and complicated forms in magnets, we propose using casing - magnetic holder.
• Potential hazard resulting from small fragments of magnets pose a threat, when accidentally swallowed, which gains importance in the context of child safety. Furthermore, tiny parts of these magnets can disrupt the diagnostic process medical in case of swallowing.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum magnetic pulling force – what it depends on?

Breakaway force is the result of a measurement for the most favorable conditions, including:

• on a base made of structural steel, optimally conducting the magnetic field
• possessing a massiveness of minimum 10 mm to avoid saturation
• with an ground touching surface
• with direct contact (without paint)
• during pulling in a direction vertical to the plane
• at temperature room level

Practical lifting capacity: influencing factors

Please note that the application force will differ depending on the following factors, in order of importance:

• Distance (between the magnet and the metal), because even a tiny distance (e.g. 0.5 mm) leads to a reduction in force by up to 50% (this also applies to varnish, corrosion or dirt).
• Loading method – catalog parameter refers to detachment vertically. When slipping, the magnet holds significantly lower power (often approx. 20-30% of nominal force).
• Steel thickness – too thin plate does not close the flux, causing part of the flux to be wasted into the air.
• Material type – ideal substrate is high-permeability steel. Hardened steels may have worse magnetic properties.
• Surface structure – the smoother and more polished the plate, the larger the contact zone and higher the lifting capacity. Unevenness creates an air distance.
• Heat – NdFeB sinters have a sensitivity to temperature. At higher temperatures they lose power, and in frost they can be stronger (up to a certain limit).

* Lifting capacity was measured with the use of a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular detachment force, however under parallel forces the holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.