SM 25x250 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of NdFeB magnets.

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

• They have constant strength, and over more than 10 years their attraction force decreases symbolically – ~1% (according to theory),
• They show high resistance to demagnetization induced by external disturbances,
• The use of an refined coating of noble metals (nickel, gold, silver) causes the element to have aesthetics,
• The surface of neodymium magnets generates a strong magnetic field – this is one of their assets,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• In view of the option of flexible molding and adaptation to specialized requirements, NdFeB magnets can be manufactured in a broad palette of geometric configurations, which increases their versatility,
• Versatile presence in future technologies – they find application in computer drives, drive modules, advanced medical instruments, as well as industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer high power in tiny dimensions, which allows their use in small systems

Disadvantages of neodymium magnets:

• At strong impacts they can crack, therefore we recommend placing them in special holders. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• Neodymium magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (a factor is the shape as well as 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
• Magnets exposed to a humid environment can corrode. Therefore when using outdoors, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture
• We suggest casing - magnetic mechanism, due to difficulties in producing nuts inside the magnet and complicated forms.
• Potential hazard related to microscopic parts of magnets pose a threat, in case of ingestion, which is particularly important in the aspect of protecting the youngest. Additionally, small elements of these devices can be problematic in diagnostics medical in case of swallowing.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which hinders application in large quantities

Maximum magnetic pulling force – what it depends on?

The declared magnet strength concerns the limit force, recorded under optimal environment, namely:

• with the application of a sheet made of special test steel, guaranteeing maximum field concentration
• with a thickness minimum 10 mm
• characterized by smoothness
• with direct contact (without coatings)
• for force applied at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Magnet lifting force in use – key factors

Bear in mind that the magnet holding may be lower influenced by elements below, starting with the most relevant:

• Air gap (between the magnet and the metal), since even a tiny clearance (e.g. 0.5 mm) leads to a drastic drop in lifting capacity by up to 50% (this also applies to paint, corrosion or dirt).
• Force direction – declared lifting capacity refers to detachment vertically. When slipping, the magnet holds significantly lower power (often approx. 20-30% of nominal force).
• Substrate thickness – to utilize 100% power, the steel must be sufficiently thick. Paper-thin metal restricts the attraction force (the magnet "punches through" it).
• Material type – the best choice is pure iron steel. Stainless steels may have worse magnetic properties.
• Surface structure – the smoother and more polished the surface, the better the adhesion and higher the lifting capacity. Unevenness creates an air distance.
• Heat – neodymium magnets have a sensitivity to temperature. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).

* Lifting capacity testing was carried out on a smooth plate of suitable thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.