SM 25x175 [2xM8] / N52 - magnetic separator

Pros and cons of rare earth magnets.

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

• They retain full power for almost ten years – the loss is just ~1% (according to analyses),
• They are noted for resistance to demagnetization induced by presence of other magnetic fields,
• In other words, due to the smooth finish of nickel, the element gains visual value,
• Magnetic induction on the working part of the magnet turns out to be exceptional,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their form) at temperatures up to 230°C and above...
• Thanks to modularity in forming and the ability to modify to complex applications,
• Universal use in high-tech industry – they are utilized in hard drives, electromotive mechanisms, medical equipment, and other advanced devices.
• Thanks to concentrated force, small magnets offer high operating force, in miniature format,

Disadvantages of neodymium magnets:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a steel housing, which not only protects them against impacts but also increases their durability
• We warn that neodymium magnets can lose their power at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• We recommend casing - magnetic mechanism, due to difficulties in realizing nuts inside the magnet and complex forms.
• Health risk resulting from small fragments of magnets can be dangerous, if swallowed, which gains importance in the context of child health protection. Furthermore, small components of these products are able to complicate diagnosis medical in case of swallowing.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which can limit application in large quantities

Detachment force of the magnet in optimal conditions – what affects it?

The specified lifting capacity concerns the maximum value, recorded under laboratory conditions, namely:

• on a plate made of mild steel, perfectly concentrating the magnetic field
• whose transverse dimension reaches at least 10 mm
• with a surface perfectly flat
• under conditions of no distance (surface-to-surface)
• during pulling in a direction vertical to the plane
• at temperature approx. 20 degrees Celsius

Practical lifting capacity: influencing factors

It is worth knowing that the application force may be lower subject to the following factors, starting with the most relevant:

• Clearance – the presence of any layer (paint, tape, gap) acts as an insulator, which reduces capacity steeply (even by 50% at 0.5 mm).
• Force direction – note that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Plate thickness – insufficiently thick sheet causes magnetic saturation, causing part of the flux to be escaped into the air.
• Steel grade – the best choice is high-permeability steel. Cast iron may attract less.
• Surface quality – the more even the surface, the larger the contact zone and higher the lifting capacity. Roughness creates an air distance.
• Thermal conditions – neodymium magnets have a negative temperature coefficient. When it is hot they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Moreover, even a slight gap {between} the magnet and the plate decreases the load capacity.