SMZR 25x200 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional field intensity, neodymium magnets offer the following advantages:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (in laboratory conditions),
• They show superior resistance to demagnetization from external magnetic fields,
• Thanks to the shiny finish and nickel coating, they have an aesthetic appearance,
• They possess significant magnetic force measurable at the magnet’s surface,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• The ability for accurate shaping or customization to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Important function in cutting-edge sectors – they are used in HDDs, electromechanical systems, medical equipment and sophisticated instruments,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of magnetic elements:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to shocks, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture , and at the same time increases its overall robustness,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on shape). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• They rust in a damp environment. If exposed to rain, we recommend using sealed magnets, such as those made of rubber,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Possible threat due to small fragments may arise, especially if swallowed, which is crucial in the context of child safety. Additionally, miniature parts from these magnets may interfere with diagnostics when ingested,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum magnetic pulling force – what it depends on?

The given pulling force of the magnet represents the maximum force, measured under optimal conditions, namely:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a smooth surface
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Lifting capacity in real conditions – factors

The lifting capacity of a magnet is influenced by in practice the following factors, according to their importance:

• Air gap between the magnet and the plate, because 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.

* Holding force was checked on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 75%. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.