SM 32x450 [2xM8] / N52 - magnetic separator

Strengths as well as weaknesses of NdFeB magnets.

Besides their tremendous magnetic power, neodymium magnets offer the following advantages:

• They retain magnetic properties for around 10 years – the loss is just ~1% (according to analyses),
• Neodymium magnets remain exceptionally resistant to loss of magnetic properties caused by magnetic disturbances,
• The use of an metallic coating of noble metals (nickel, gold, silver) causes the element to look better,
• Magnets are characterized by very high magnetic induction on the working surface,
• Thanks to resistance to high temperature, they are able to function (depending on the shape) even at temperatures up to 230°C and higher...
• Possibility of detailed forming as well as adjusting to specific conditions,
• Huge importance in modern industrial fields – they serve a role in HDD drives, motor assemblies, medical devices, also technologically advanced constructions.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Cons of neodymium magnets and ways of using them

• At strong impacts they can break, therefore we advise placing them in special holders. A metal housing provides additional protection against damage and increases the magnet's durability.
• Neodymium magnets lose their force 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 durability even at temperatures up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material immune to moisture, when using outdoors
• Limited ability of creating nuts in the magnet and complex forms - preferred is casing - magnet mounting.
• Health risk related to microscopic parts of magnets can be dangerous, in case of ingestion, which is particularly important in the context of child health protection. Furthermore, tiny parts of these devices are able to disrupt the diagnostic process medical when they are in the body.
• Due to expensive raw materials, their price exceeds standard values,

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

The specified lifting capacity concerns the maximum value, obtained under laboratory conditions, specifically:

• using a sheet made of high-permeability steel, acting as a circuit closing element
• whose transverse dimension reaches at least 10 mm
• with a surface perfectly flat
• without any insulating layer between the magnet and steel
• during pulling in a direction perpendicular to the mounting surface
• at ambient temperature approx. 20 degrees Celsius

Determinants of practical lifting force of a magnet

In real-world applications, the real power is determined by many variables, listed from most significant:

• Space between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by varnish or unevenness) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Force direction – declared lifting capacity refers to pulling vertically. When applying parallel force, the magnet holds significantly lower power (typically approx. 20-30% of nominal force).
• Plate thickness – insufficiently thick sheet causes magnetic saturation, causing part of the power to be escaped into the air.
• Steel type – mild steel attracts best. Higher carbon content lower magnetic permeability and lifting capacity.
• Surface structure – the smoother and more polished the surface, the larger the contact zone and higher the lifting capacity. Roughness acts like micro-gaps.
• Heat – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and in frost they can be stronger (up to a certain limit).

* Holding force was measured 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. In addition, even a slight gap {between} the magnet and the plate lowers the lifting capacity.