SM 32x125 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They virtually do not lose power, because even after 10 years the decline in efficiency is only ~1% (in laboratory conditions),
• Magnets effectively resist against loss of magnetization caused by foreign field sources,
• A magnet with a metallic nickel surface looks better,
• The surface of neodymium magnets generates a maximum magnetic field – this is a key feature,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and are able to act (depending on the shape) even at a temperature of 230°C or more...
• Thanks to versatility in designing and the capacity to customize to unusual requirements,
• Universal use in innovative solutions – they are utilized in HDD drives, electromotive mechanisms, medical equipment, as well as modern systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in tiny dimensions, which makes them useful in small systems

What to avoid - cons of neodymium magnets and ways of using them

• They are prone to damage upon heavy impacts. To avoid cracks, it is worth protecting magnets in a protective case. Such protection not only protects the magnet but also increases its resistance to damage
• When exposed to high temperature, neodymium magnets experience a drop in strength. Often, when the temperature exceeds 80°C, their power 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 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 as well as corrosion.
• We recommend a housing - magnetic mechanism, due to difficulties in producing nuts inside the magnet and complicated shapes.
• Health risk resulting from small fragments of magnets can be dangerous, if swallowed, which gains importance in the context of child safety. Additionally, small components of these devices are able to be problematic in diagnostics medical in case of swallowing.
• High unit price – neodymium magnets have a higher price 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 represents the peak performance, recorded under ideal test conditions, meaning:

• on a block made of structural steel, effectively closing the magnetic field
• whose thickness equals approx. 10 mm
• characterized by smoothness
• without any air gap between the magnet and steel
• for force applied at a right angle (pull-off, not shear)
• at ambient temperature approx. 20 degrees Celsius

Impact of factors on magnetic holding capacity in practice

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

• Gap between surfaces – even a fraction of a millimeter of separation (caused e.g. by veneer or unevenness) significantly weakens the pulling force, often by half at just 0.5 mm.
• Force direction – declared lifting capacity refers to pulling vertically. When attempting to slide, the magnet exhibits significantly lower power (typically 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 generating force.
• Steel type – low-carbon steel attracts best. Alloy admixtures lower magnetic permeability and holding force.
• Smoothness – full contact is obtained only on polished steel. Any scratches and bumps reduce the real contact area, reducing force.
• Operating temperature – neodymium magnets have a sensitivity to temperature. At higher temperatures they lose power, and in frost 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, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the lifting capacity.