SM 32x475 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They do not lose their power around ten years – the reduction of power is only ~1% (according to tests),
• They protect against demagnetization induced by surrounding magnetic influence very well,
• The use of a polished gold surface provides a refined finish,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• With the right combination of compounds, they reach significant thermal stability, enabling operation at or above 230°C (depending on the form),
• With the option for fine forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Key role in new technology industries – they are used in computer drives, electric motors, healthcare devices along with technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which makes them useful in small systems

Disadvantages of neodymium magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to shocks, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from damage and strengthens its overall strength,
• Magnets lose magnetic efficiency when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (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,
• They rust in a moist environment – during outdoor use, we recommend using moisture-resistant magnets, such as those made of non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Potential hazard linked to microscopic shards may arise, if ingested accidentally, which is important in the health of young users. It should also be noted that miniature parts from these products might hinder health screening when ingested,
• In cases of tight budgets, neodymium magnet cost may be a barrier,

Best holding force of the magnet in ideal parameters – what it depends on?

The given holding capacity of the magnet corresponds to the highest holding force, calculated in the best circumstances, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a polished side
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

Practical lifting capacity: influencing factors

The lifting capacity of a magnet depends on in practice the following factors, ordered from most important to least significant:

• 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 optimal thickness (min. 20 mm), under perpendicular detachment force, in contrast under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet and the plate decreases the holding force.