SM 18x150 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their strong magnetism, neodymium magnets have these key benefits:

• They retain their magnetic properties for almost 10 years – the drop is just ~1% (based on simulations),
• They are extremely resistant to demagnetization caused by external magnetic fields,
• Because of the brilliant layer of silver, the component looks aesthetically refined,
• Magnetic induction on the surface of these magnets is notably high,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to form),
• The ability for accurate shaping as well as customization to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Significant impact in modern technologies – they find application in hard drives, rotating machines, healthcare devices as well as high-tech tools,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to physical collisions, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall resistance,
• They lose power at elevated temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a moist environment. If exposed to rain, we recommend using sealed magnets, such as those made of polymer,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing fine shapes directly in the magnet,
• Possible threat related to magnet particles may arise, in case of ingestion, which is crucial in the health of young users. It should also be noted that small elements from these assemblies can complicate medical imaging if inside the body,
• In cases of tight budgets, neodymium magnet cost may not be economically viable,

Maximum holding power of the magnet – what it depends on?

The given lifting capacity of the magnet represents the maximum lifting force, measured in the best circumstances, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• in a perpendicular direction of force
• under standard ambient temperature

What influences lifting capacity in practice

The lifting capacity of a magnet depends on in practice the following factors, according to their importance:

• 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 testing was conducted on a smooth plate of suitable thickness, under perpendicular forces, in contrast under shearing force the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.