SM 18x275 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of rare earth magnets.

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

• Their power is maintained, and after approximately 10 years it decreases only by ~1% (according to research),
• Magnets perfectly resist against demagnetization caused by ambient magnetic noise,
• In other words, due to the metallic surface of gold, the element looks attractive,
• The surface of neodymium magnets generates a concentrated magnetic field – this is a key feature,
• Thanks to resistance to high temperature, they can operate (depending on the shape) even at temperatures up to 230°C and higher...
• Thanks to the ability of free shaping and adaptation to specialized requirements, NdFeB magnets can be produced in a broad palette of forms and dimensions, which makes them more universal,
• Significant place in future technologies – they find application in mass storage devices, electric drive systems, precision medical tools, as well as multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which allows their use in miniature devices

Disadvantages of neodymium magnets:

• They are fragile upon too strong impacts. To avoid cracks, it is worth securing magnets in a protective case. Such protection not only protects the magnet but also increases its resistance to damage
• Neodymium magnets lose their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• When exposed to humidity, magnets usually rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which prevent oxidation and corrosion.
• We suggest a housing - magnetic holder, due to difficulties in realizing threads inside the magnet and complex forms.
• Possible danger resulting from small fragments of magnets are risky, when accidentally swallowed, which becomes key in the aspect of protecting the youngest. Furthermore, small elements of these devices are able to be problematic in diagnostics medical after entering the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Magnetic strength at its maximum – what contributes to it?

Information about lifting capacity was determined for optimal configuration, taking into account:

• with the contact of a yoke made of special test steel, guaranteeing full magnetic saturation
• whose transverse dimension equals approx. 10 mm
• with a plane free of scratches
• without the slightest clearance between the magnet and steel
• during pulling in a direction perpendicular to the plane
• at temperature approx. 20 degrees Celsius

Practical aspects of lifting capacity – factors

In real-world applications, the real power depends on many variables, ranked from most significant:

• Gap (betwixt the magnet and the plate), because even a very small distance (e.g. 0.5 mm) can cause a drastic drop in lifting capacity by up to 50% (this also applies to varnish, rust or dirt).
• Force direction – note that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Steel thickness – insufficiently thick sheet does not accept the full field, causing part of the power to be wasted into the air.
• Material type – the best choice is high-permeability steel. Stainless steels may have worse magnetic properties.
• Surface quality – the smoother and more polished the plate, the better the adhesion and higher the lifting capacity. Unevenness creates an air distance.
• Thermal conditions – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and in frost they can be stronger (up to a certain limit).

* Lifting capacity was assessed using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular detachment force, in contrast under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet and the plate reduces the lifting capacity.