SM 32x375 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They do not lose their power around 10 years – the loss of power is only ~1% (based on measurements),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• Thanks to the shiny finish and nickel coating, they have an elegant appearance,
• They have exceptional magnetic induction on the surface of the magnet,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the form),
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which broadens their functional possibilities,
• Wide application in modern technologies – they are used in hard drives, electromechanical systems, medical equipment as well as technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in small dimensions, which makes them useful in compact constructions

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to physical collisions, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage and increases its overall durability,
• Magnets lose magnetic efficiency when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (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,
• They rust in a moist environment. If exposed to rain, we recommend using encapsulated magnets, such as those made of polymer,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing complex structures directly in the magnet,
• Safety concern from tiny pieces may arise, in case of ingestion, which is crucial in the family environments. It should also be noted that small elements from these devices may interfere with diagnostics when ingested,
• In cases of tight budgets, neodymium magnet cost may be a barrier,

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given strength of the magnet represents the optimal strength, determined in the best circumstances, specifically:

• with mild steel, serving as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a polished side
• in conditions of no clearance
• with vertical force applied
• at room temperature

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is conditioned by the following aspects, from crucial to less important:

• 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 testing was carried out on a smooth plate of optimal thickness, under perpendicular forces, in contrast under attempts to slide the magnet the holding force is lower. In addition, even a slight gap {between} the magnet and the plate reduces the load capacity.