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

Pros as well as cons of neodymium magnets.

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

• They have constant strength, and over nearly ten years their attraction force decreases symbolically – ~1% (according to theory),
• They have excellent resistance to weakening of magnetic properties as a result of opposing magnetic fields,
• The use of an aesthetic coating of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Magnetic induction on the surface of the magnet is impressive,
• With the right combination of materials, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the form),
• Possibility of individual modeling as well as adjusting to precise requirements,
• Universal use in modern technologies – they serve a role in mass storage devices, electric motors, precision medical tools, as well as other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in small dimensions, which makes them useful in small systems

What to avoid - cons of neodymium magnets and proposals for their use:

• They are fragile upon too strong impacts. To avoid cracks, it is worth securing magnets in special housings. Such protection not only shields the magnet but also improves its resistance to damage
• Neodymium magnets lose their force 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 durability even at temperatures up to 230°C
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation and corrosion.
• Due to limitations in producing threads and complicated forms in magnets, we propose using a housing - magnetic mechanism.
• Health risk to health – tiny shards of magnets are risky, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. It is also worth noting that tiny parts of these devices can complicate diagnosis medical after entering the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum magnetic pulling force – what it depends on?

The force parameter is a result of laboratory testing performed under specific, ideal conditions:

• on a plate made of mild steel, effectively closing the magnetic field
• whose thickness equals approx. 10 mm
• with a surface cleaned and smooth
• under conditions of gap-free contact (metal-to-metal)
• for force applied at a right angle (pull-off, not shear)
• at temperature room level

Impact of factors on magnetic holding capacity in practice

During everyday use, the actual holding force results from many variables, presented from the most important:

• Distance (betwixt the magnet and the plate), as even a microscopic clearance (e.g. 0.5 mm) can cause a decrease in force by up to 50% (this also applies to paint, rust or dirt).
• Force direction – declared lifting capacity refers to pulling vertically. When attempting to slide, the magnet holds much less (often approx. 20-30% of nominal force).
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of converting into lifting capacity.
• Metal type – different alloys attracts identically. High carbon content weaken the attraction effect.
• Surface quality – the smoother and more polished the surface, the better the adhesion and higher the lifting capacity. Unevenness creates an air distance.
• Thermal environment – heating the magnet results in weakening of induction. It is worth remembering the thermal limit for a given model.

* Lifting capacity testing was performed on plates with a smooth surface of optimal thickness, under a perpendicular pulling force, in contrast under shearing force the lifting capacity is smaller. In addition, even a slight gap {between} the magnet and the plate decreases the load capacity.