SM 25x250 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• Their magnetic field is durable, and after around 10 years, it drops only by ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is notable,
• Thanks to the glossy finish and silver coating, they have an aesthetic appearance,
• Magnetic induction on the surface of these magnets is very strong,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• Thanks to the freedom in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their application range,
• Wide application in modern technologies – they are used in computer drives, electric drives, medical equipment as well as technologically developed systems,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of neodymium magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to physical collisions, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage and additionally increases its overall robustness,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (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,
• They rust in a wet environment. For outdoor use, we recommend using sealed magnets, such as those made of polymer,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing holes directly in the magnet,
• Health risk linked to microscopic shards may arise, in case of ingestion, which is significant in the health of young users. It should also be noted that minuscule fragments from these products might disrupt scanning if inside the body,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Maximum lifting force for a neodymium magnet – what affects it?

The given lifting capacity of the magnet means the maximum lifting force, determined under optimal conditions, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• in a perpendicular direction of force
• at room temperature

Lifting capacity in practice – influencing factors

Practical lifting force is determined by elements, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, because 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 was determined using a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, however under parallel forces the holding force is lower. In addition, even a minimal clearance {between} the magnet and the plate decreases the load capacity.