SM 25x350 [2xM8] / N52 - magnetic separator

Strengths and weaknesses of rare earth magnets.

In addition to their magnetic capacity, neodymium magnets provide the following advantages:

• Their power remains stable, and after approximately 10 years it decreases only by ~1% (theoretically),
• They do not lose their magnetic properties even under close interference source,
• The use of an elegant coating of noble metals (nickel, gold, silver) causes the element to look better,
• Magnets possess extremely high magnetic induction on the surface,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Due to the ability of free molding and customization to specialized requirements, NdFeB magnets can be modeled in a broad palette of shapes and sizes, which amplifies use scope,
• Wide application in modern industrial fields – they serve a role in HDD drives, drive modules, precision medical tools, and industrial machines.
• Thanks to concentrated force, small magnets offer high operating force, with minimal size,

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

• At strong impacts they can break, therefore we advise placing them in steel cases. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• Neodymium magnets decrease their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• Limited ability of producing threads in the magnet and complicated forms - preferred is cover - magnet mounting.
• Health risk related to microscopic parts of magnets are risky, in case of ingestion, which is particularly important in the aspect of protecting the youngest. It is also worth noting that small elements of these magnets are able to be problematic in diagnostics medical in case of swallowing.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum lifting capacity of the magnet – what affects it?

Information about lifting capacity was determined for the most favorable conditions, taking into account:

• using a sheet made of mild steel, serving as a magnetic yoke
• with a thickness of at least 10 mm
• with a plane free of scratches
• with direct contact (no impurities)
• under axial application of breakaway force (90-degree angle)
• at standard ambient temperature

Lifting capacity in practice – influencing factors

During everyday use, the actual holding force depends on several key aspects, ranked from crucial:

• Distance – the presence of foreign body (rust, tape, air) acts as an insulator, which reduces capacity rapidly (even by 50% at 0.5 mm).
• Force direction – note that the magnet holds strongest perpendicularly. Under shear forces, the holding force drops significantly, often to levels of 20-30% of the maximum value.
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of converting into lifting capacity.
• Steel grade – the best choice is pure iron steel. Hardened steels may have worse magnetic properties.
• Surface quality – the smoother and more polished the plate, the larger the contact zone and stronger the hold. Unevenness acts like micro-gaps.
• Temperature influence – high temperature reduces magnetic field. Too high temperature can permanently damage the magnet.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the load capacity is reduced by as much as 5 times. Additionally, even a minimal clearance {between} the magnet and the plate reduces the holding force.