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

Strengths and weaknesses of neodymium magnets.

Apart from their consistent magnetic energy, neodymium magnets have these key benefits:

• They do not lose strength, even during approximately 10 years – the decrease in lifting capacity is only ~1% (according to tests),
• They are extremely resistant to demagnetization induced by external magnetic fields,
• In other words, due to the reflective surface of gold, the element becomes visually attractive,
• They feature high magnetic induction at the operating surface, which increases their power,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Thanks to freedom in forming and the ability to adapt to complex applications,
• Key role in high-tech industry – they serve a role in hard drives, electric drive systems, advanced medical instruments, and modern systems.
• Thanks to concentrated force, small magnets offer high operating force, occupying minimum space,

Characteristics of disadvantages of neodymium magnets and ways of using them

• To avoid cracks under impact, we suggest using special steel housings. Such a solution secures the magnet and simultaneously improves its durability.
• When exposed to high temperature, neodymium magnets experience a drop in power. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size and shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They oxidize in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• We recommend casing - magnetic mount, due to difficulties in producing threads inside the magnet and complex shapes.
• Health risk to health – tiny shards of magnets are risky, when accidentally swallowed, which is particularly important in the context of child safety. Furthermore, small components of these magnets are able to disrupt the diagnostic process medical in case of swallowing.
• Due to neodymium price, their price is higher than average,

Optimal lifting capacity of a neodymium magnet – what affects it?

Breakaway force is the result of a measurement for optimal configuration, assuming:

• on a block made of mild steel, effectively closing the magnetic flux
• whose transverse dimension is min. 10 mm
• with an ideally smooth contact surface
• without the slightest clearance between the magnet and steel
• for force acting at a right angle (in the magnet axis)
• at temperature room level

Practical aspects of lifting capacity – factors

Bear in mind that the magnet holding will differ depending on the following factors, in order of importance:

• Gap between surfaces – even a fraction of a millimeter of separation (caused e.g. by veneer or dirt) diminishes the pulling force, often by half at just 0.5 mm.
• Direction of force – maximum parameter is reached only during pulling at a 90° angle. The force required to slide of the magnet along the surface is usually many times smaller (approx. 1/5 of the lifting capacity).
• Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal restricts the lifting capacity (the magnet "punches through" it).
• Plate material – low-carbon steel gives the best results. Alloy admixtures lower magnetic permeability and lifting capacity.
• Surface quality – the smoother and more polished the surface, the better the adhesion and stronger the hold. Roughness creates an air distance.
• Heat – NdFeB sinters have a sensitivity to temperature. When it is hot they lose power, and in frost gain strength (up to a certain limit).

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the load capacity.