SMZR 25x175 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior power, neodymium magnets have these key benefits:

• They have stable power, and over around 10 years their performance decreases symbolically – ~1% (according to theory),
• They show superior resistance to demagnetization from outside magnetic sources,
• Because of the lustrous layer of gold, the component looks aesthetically refined,
• They have exceptional magnetic induction on the surface of the magnet,
• Thanks to their high temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• The ability for precise shaping or adaptation to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Key role in cutting-edge sectors – they serve a purpose in hard drives, electric drives, clinical machines along with other advanced devices,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to external force, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks and additionally enhances its overall durability,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible performance loss (influenced by the magnet’s form). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is common to use sealed magnets made of rubber for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing fine shapes directly in the magnet,
• Safety concern linked to microscopic shards may arise, if ingested accidentally, which is important in the family environments. Furthermore, minuscule fragments from these magnets may complicate medical imaging after being swallowed,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Maximum holding power of the magnet – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, assessed under optimal conditions, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a smooth surface
• in conditions of no clearance
• under perpendicular detachment force
• at room temperature

Practical lifting capacity: influencing factors

Practical lifting force is dependent on elements, by priority:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) can cause a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Holding force was tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the holding force is lower. Additionally, even a minimal clearance {between} the magnet and the plate reduces the load capacity.