UMH 20x7x35 [M4] / N38 - magnetic holder with hook

Advantages as well as disadvantages of neodymium magnets.

In addition to their pulling strength, neodymium magnets provide the following advantages:

• They have unchanged lifting capacity, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• Neodymium magnets prove to be remarkably resistant to loss of magnetic properties caused by external field sources,
• A magnet with a smooth silver surface is more attractive,
• Magnetic induction on the working layer of the magnet remains very high,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
• In view of the potential of precise molding and customization to custom projects, neodymium magnets can be manufactured in a variety of geometric configurations, which increases their versatility,
• Fundamental importance in future technologies – they find application in hard drives, drive modules, advanced medical instruments, also complex engineering applications.
• Thanks to concentrated force, small magnets offer high operating force, with minimal size,

Problematic aspects of neodymium magnets: weaknesses and usage proposals

• Brittleness is one of their disadvantages. Upon intense impact they can fracture. We recommend keeping them in a special holder, which not only secures them against impacts but also increases their durability
• Neodymium magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (a factor is the shape and dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which prevent oxidation as well as corrosion.
• Limited ability of producing nuts in the magnet and complicated forms - preferred is a housing - magnetic holder.
• Potential hazard related to microscopic parts of magnets pose a threat, if swallowed, which is particularly important in the context of child health protection. Additionally, tiny parts of these products can complicate diagnosis medical in case of swallowing.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which hinders application in large quantities

Maximum lifting force for a neodymium magnet – what contributes to it?

The load parameter shown concerns the maximum value, obtained under laboratory conditions, specifically:

• using a sheet made of low-carbon steel, acting as a magnetic yoke
• possessing a thickness of minimum 10 mm to avoid saturation
• with a surface free of scratches
• with direct contact (no impurities)
• for force applied at a right angle (pull-off, not shear)
• in stable room temperature

Practical lifting capacity: influencing factors

Please note that the magnet holding will differ subject to the following factors, starting with the most relevant:

• Gap between surfaces – every millimeter of separation (caused e.g. by varnish or unevenness) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Angle of force application – highest force is reached only during pulling at a 90° angle. The shear force of the magnet along the surface is typically many times smaller (approx. 1/5 of the lifting capacity).
• Wall thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field passes through the material instead of converting into lifting capacity.
• Chemical composition of the base – mild steel attracts best. Alloy steels lower magnetic permeability and lifting capacity.
• Plate texture – smooth surfaces guarantee perfect abutment, which increases field saturation. Uneven metal reduce efficiency.
• Thermal environment – heating the magnet causes a temporary drop of induction. Check the maximum operating temperature for a given model.

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, in contrast under shearing force the load capacity is reduced by as much as 5 times. Moreover, even a small distance {between} the magnet’s surface and the plate lowers the load capacity.