SM 32x225 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have unchanged lifting capacity, and over nearly 10 years their performance decreases symbolically – ~1% (in testing),
• Their ability to resist magnetic interference from external fields is impressive,
• The use of a polished nickel surface provides a refined finish,
• They possess significant magnetic force measurable at the magnet’s surface,
• Thanks to their exceptional temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• The ability for accurate shaping or adjustment to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Important function in modern technologies – they are used in data storage devices, rotating machines, clinical machines as well as other advanced devices,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of magnetic elements:

• They can break when subjected to a sudden impact. If the magnets are exposed to shocks, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage and additionally enhances its overall robustness,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to humidity can corrode. Therefore, for outdoor applications, we suggest waterproof types made of rubber,
• Limited ability to create internal holes in the magnet – the use of a external casing is recommended,
• Potential hazard linked to microscopic shards may arise, when consumed by mistake, which is important in the protection of children. Moreover, tiny components from these magnets might complicate medical imaging if inside the body,
• Due to expensive raw materials, their cost is above average,

Magnetic strength at its maximum – what it depends on?

The given pulling force of the magnet corresponds to the maximum force, assessed in a perfect environment, that is:

• with mild steel, serving as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• with vertical force applied
• at room temperature

Determinants of lifting force in real conditions

Practical lifting force is determined by elements, by priority:

• Air gap between the magnet and the plate, as even a very small distance (e.g. 0.5 mm) causes 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.

* Lifting capacity was measured with the use of a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, however under shearing force the lifting capacity is smaller. Moreover, even a small distance {between} the magnet and the plate reduces the holding force.