SMZR 25x250 / N52 - magnetic separator with handle

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• Their power is maintained, and after around 10 years, it drops only by ~1% (according to research),
• They remain magnetized despite exposure to strong external fields,
• Because of the reflective layer of gold, the component looks visually appealing,
• They have exceptional magnetic induction on the surface of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to form),
• The ability for accurate shaping and customization to specific needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which amplifies their functionality across industries,
• Key role in cutting-edge sectors – they are used in hard drives, electromechanical systems, healthcare devices as well as other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which allows for use in compact constructions

Disadvantages of magnetic elements:

• They can break when subjected to a strong impact. If the magnets are exposed to shocks, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture while also 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 structure). 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 wise to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Health risk linked to microscopic shards may arise, in case of ingestion, which is notable in the protection of children. Additionally, tiny components from these magnets may hinder health screening once in the system,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which may limit large-scale applications

Magnetic strength at its maximum – what contributes to it?

The given pulling force of the magnet corresponds to the maximum force, measured in ideal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• at room temperature

Lifting capacity in real conditions – factors

The lifting capacity of a magnet is determined by in practice key elements, according to their importance:

• Air gap between the magnet and the plate, since 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 using a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, in contrast under parallel forces the load capacity is reduced by as much as 5 times. Additionally, even a slight gap {between} the magnet and the plate decreases the lifting capacity.