SM 25x225 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their tremendous strength, neodymium magnets offer the following advantages:

• They do not lose their power approximately ten years – the decrease of lifting capacity is only ~1% (according to tests),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• The use of a polished gold surface provides a smooth finish,
• They have very high magnetic induction on the surface of the magnet,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for tailored forming and targeted design, these magnets can be produced in multiple shapes and sizes, greatly improving application potential,
• Important function in cutting-edge sectors – they are used in HDDs, rotating machines, clinical machines and high-tech tools,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to mechanical hits, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture while also increases its overall resistance,
• 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,
• Magnets exposed to humidity can rust. Therefore, for outdoor applications, we advise waterproof types made of plastic,
• Limited ability to create complex details in the magnet – the use of a housing is recommended,
• Safety concern from tiny pieces may arise, if ingested accidentally, which is important in the context of child safety. Furthermore, small elements from these magnets can interfere with diagnostics when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Breakaway strength of the magnet in ideal conditions – what affects it?

The given holding capacity of the magnet means the highest holding force, determined in the best circumstances, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a refined outer layer
• with no separation
• in a perpendicular direction of force
• in normal thermal conditions

Key elements affecting lifting force

Practical lifting force is determined by elements, by priority:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) can cause 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 plates with a smooth surface of optimal thickness, under perpendicular forces, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate lowers the load capacity.