SM 25x250 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

Apart from their consistent holding force, neodymium magnets have these key benefits:

• They have constant strength, and over nearly 10 years their performance decreases symbolically – ~1% (according to theory),
• They retain their magnetic properties even under strong external field,
• By covering with a decorative layer of silver, the element acquires an aesthetic look,
• They feature high magnetic induction at the operating surface, which increases their power,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
• Possibility of accurate machining as well as optimizing to specific conditions,
• Huge importance in advanced technology sectors – they serve a role in magnetic memories, motor assemblies, advanced medical instruments, as well as multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which makes them useful in small systems

What to avoid - cons of neodymium magnets and proposals for their use:

• Brittleness is one of their disadvantages. Upon intense impact they can fracture. We advise keeping them in a strong case, which not only protects them against impacts but also raises their durability
• NdFeB magnets demagnetize 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 very resistant to heat
• When exposed to humidity, magnets usually rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• Limited ability of making nuts in the magnet and complex forms - preferred is casing - magnetic holder.
• Health risk resulting from small fragments of magnets are risky, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. Furthermore, small elements of these devices can complicate diagnosis medical when they are in the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum holding power of the magnet – what it depends on?

Holding force of 0.00 kg is a result of laboratory testing conducted under the following configuration:

• with the use of a sheet made of special test steel, ensuring maximum field concentration
• possessing a thickness of minimum 10 mm to ensure full flux closure
• with a surface free of scratches
• without any clearance between the magnet and steel
• for force applied at a right angle (in the magnet axis)
• at ambient temperature room level

Key elements affecting lifting force

In real-world applications, the real power results from many variables, listed from the most important:

• Gap between surfaces – even a fraction of a millimeter of distance (caused e.g. by varnish or dirt) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Pull-off angle – remember that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the nominal value.
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet limits the attraction force (the magnet "punches through" it).
• Chemical composition of the base – mild steel attracts best. Alloy steels reduce magnetic permeability and lifting capacity.
• Surface finish – ideal contact is obtained only on smooth steel. Any scratches and bumps create air cushions, reducing force.
• Thermal environment – heating the magnet results in weakening of force. Check the maximum operating temperature for a given model.

* Lifting capacity testing was conducted on a smooth plate of optimal thickness, under a perpendicular pulling force, in contrast under parallel forces the load capacity is reduced by as much as 75%. Additionally, even a small distance {between} the magnet and the plate reduces the holding force.