SM 18x200 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of rare earth magnets.

Besides their immense field intensity, neodymium magnets offer the following advantages:

• They retain full power for nearly 10 years – the drop is just ~1% (according to analyses),
• Magnets very well protect themselves against demagnetization caused by ambient magnetic noise,
• The use of an refined layer of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• They are known for high magnetic induction at the operating surface, making them more effective,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to modularity in designing and the capacity to adapt to specific needs,
• Fundamental importance in modern industrial fields – they are utilized in mass storage devices, drive modules, precision medical tools, as well as complex engineering applications.
• Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which makes them useful in compact constructions

Problematic aspects of neodymium magnets: application proposals

• At very strong impacts they can break, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• When exposed to high temperature, neodymium magnets suffer 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
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation as well as corrosion.
• We suggest a housing - magnetic mechanism, due to difficulties in realizing threads inside the magnet and complex forms.
• Potential hazard to health – tiny shards of magnets pose a threat, in case of ingestion, which is particularly important in the context of child health protection. It is also worth noting that small components of these magnets can be problematic in diagnostics medical when they are in the body.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Best holding force of the magnet in ideal parameters – what affects it?

The declared magnet strength refers to the peak performance, obtained under optimal environment, namely:

• with the application of a sheet made of special test steel, guaranteeing full magnetic saturation
• with a thickness minimum 10 mm
• with an ideally smooth touching surface
• without any clearance between the magnet and steel
• for force acting at a right angle (pull-off, not shear)
• in stable room temperature

Determinants of lifting force in real conditions

During everyday use, the real power results from a number of factors, listed from the most important:

• Gap (between the magnet and the metal), because even a very small distance (e.g. 0.5 mm) leads to a drastic drop in force by up to 50% (this also applies to varnish, rust or debris).
• Force direction – note that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops significantly, often to levels of 20-30% of the nominal value.
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Material type – ideal substrate is pure iron steel. Hardened steels may attract less.
• Surface structure – the smoother and more polished the surface, the larger the contact zone and higher the lifting capacity. Unevenness creates an air distance.
• Thermal conditions – NdFeB sinters have a sensitivity to temperature. At higher temperatures they lose power, and in frost they can be stronger (up to a certain limit).

* Lifting capacity was measured using a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular detachment force, whereas under parallel forces the lifting capacity is smaller. Moreover, even a small distance {between} the magnet’s surface and the plate lowers the lifting capacity.