SM 18x125 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have unchanged lifting capacity, and over more than 10 years their attraction force decreases symbolically – ~1% (in testing),
• They remain magnetized despite exposure to strong external fields,
• In other words, due to the metallic gold coating, the magnet obtains an professional appearance,
• They have extremely strong magnetic induction on the surface of the magnet,
• 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 magnetic form),
• The ability for precise shaping as well as adjustment to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Key role in cutting-edge sectors – they are utilized in computer drives, electric drives, medical equipment along with other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which allows for use in compact constructions

Disadvantages of neodymium magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to physical collisions, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from damage , and at the same time enhances its overall resistance,
• They lose magnetic force at extreme temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the shape and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of rubber for outdoor use,
• 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, when consumed by mistake, which is significant in the protection of children. Additionally, tiny components from these devices may disrupt scanning if inside the body,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Optimal lifting capacity of a neodymium magnet – what affects it?

The given strength of the magnet means the optimal strength, determined in the best circumstances, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Lifting capacity in practice – influencing factors

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

• 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 using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular pulling force, however under shearing force the lifting capacity is smaller. In addition, even a small distance {between} the magnet’s surface and the plate decreases the load capacity.