SM 25x150 [2xM8] / N52 - magnetic separator

Pros as well as cons of rare earth magnets.

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

• They do not lose magnetism, even after approximately ten years – the decrease in power is only ~1% (according to tests),
• They retain their magnetic properties even under external field action,
• Thanks to the shimmering finish, the surface of nickel, gold-plated, or silver gives an elegant appearance,
• They feature high magnetic induction at the operating surface, making them more effective,
• Thanks to resistance to high temperature, they are able to function (depending on the shape) even at temperatures up to 230°C and higher...
• Thanks to versatility in constructing and the capacity to customize to client solutions,
• Versatile presence in advanced technology sectors – they serve a role in mass storage devices, electric motors, medical devices, as well as modern systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which makes them useful in compact constructions

Problematic aspects of neodymium magnets: weaknesses and usage proposals

• They are prone to damage upon heavy impacts. To avoid cracks, it is worth protecting magnets using a steel holder. Such protection not only protects the magnet but also increases its resistance to damage
• When exposed to high temperature, neodymium magnets experience a drop in strength. Often, when the temperature exceeds 80°C, their power decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They rust 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 nuts inside the magnet and complicated forms.
• Possible danger related to microscopic parts of magnets can be dangerous, when accidentally swallowed, which is particularly important in the aspect of protecting the youngest. Furthermore, small components of these products are able to be problematic in diagnostics medical in case of swallowing.
• With mass production the cost of neodymium magnets is a challenge,

Optimal lifting capacity of a neodymium magnet – what contributes to it?

Magnet power was determined for the most favorable conditions, including:

• on a plate made of mild steel, perfectly concentrating the magnetic field
• with a cross-section minimum 10 mm
• characterized by lack of roughness
• under conditions of no distance (surface-to-surface)
• for force applied at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Lifting capacity in real conditions – factors

Holding efficiency impacted by specific conditions, including (from most important):

• Distance (betwixt the magnet and the metal), because even a very small clearance (e.g. 0.5 mm) can cause a decrease in force by up to 50% (this also applies to varnish, rust or debris).
• Load vector – highest force is obtained only during pulling at a 90° angle. The force required to slide of the magnet along the surface is standardly many times lower (approx. 1/5 of the lifting capacity).
• Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of generating force.
• Material composition – different alloys reacts the same. Alloy additives worsen the interaction with the magnet.
• Base smoothness – the smoother and more polished the surface, the better the adhesion and higher the lifting capacity. Roughness creates an air distance.
• Operating temperature – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and in frost gain strength (up to a certain limit).

* Holding force was tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet and the plate reduces the load capacity.