SM 25x350 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• Their strength is maintained, and after around 10 years it drops only by ~1% (theoretically),
• Neodymium magnets prove to be exceptionally resistant to magnetic field loss caused by external interference,
• By using a lustrous coating of nickel, the element gains an nice look,
• The surface of neodymium magnets generates a concentrated magnetic field – this is a distinguishing feature,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can work (depending on the shape) even at a temperature of 230°C or more...
• Thanks to flexibility in forming and the ability to customize to specific needs,
• Wide application in electronics industry – they find application in HDD drives, electromotive mechanisms, medical devices, and other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in tiny dimensions, which makes them useful in small systems

Disadvantages of neodymium magnets:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can break. We recommend keeping them in a strong case, which not only secures them against impacts but also raises their durability
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• Magnets exposed to a humid environment can rust. Therefore while using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material resistant to moisture
• We recommend casing - magnetic mechanism, due to difficulties in creating threads inside the magnet and complicated forms.
• Potential hazard related to microscopic parts of magnets are risky, when accidentally swallowed, which becomes key in the context of child safety. Furthermore, tiny parts of these devices can disrupt the diagnostic process medical in case of swallowing.
• With mass production the cost of neodymium magnets is economically unviable,

Maximum magnetic pulling force – what contributes to it?

The lifting capacity listed is a theoretical maximum value executed under the following configuration:

• on a plate made of mild steel, optimally conducting the magnetic field
• whose transverse dimension equals approx. 10 mm
• characterized by lack of roughness
• without the slightest clearance between the magnet and steel
• for force applied at a right angle (in the magnet axis)
• in temp. approx. 20°C

Lifting capacity in practice – influencing factors

During everyday use, the actual holding force results from a number of factors, listed from the most important:

• Gap (betwixt the magnet and the metal), because even a microscopic clearance (e.g. 0.5 mm) can cause a decrease in lifting capacity by up to 50% (this also applies to varnish, corrosion or dirt).
• Force direction – declared lifting capacity refers to pulling vertically. When applying parallel force, the magnet exhibits much less (typically approx. 20-30% of maximum force).
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of generating force.
• Material type – ideal substrate is high-permeability steel. Cast iron may have worse magnetic properties.
• Surface structure – the more even the surface, the better the adhesion and higher the lifting capacity. Roughness creates an air distance.
• Thermal factor – hot environment weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity testing was conducted on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, in contrast under shearing force the holding force is lower. Additionally, even a small distance {between} the magnet and the plate decreases the holding force.