SM 18x100 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior power, neodymium magnets have these key benefits:

• Their magnetic field is durable, and after approximately ten years, it drops only by ~1% (according to research),
• They show exceptional resistance to demagnetization from external field exposure,
• Because of the brilliant layer of silver, the component looks high-end,
• They have extremely strong magnetic induction on the surface of the magnet,
• With the right combination of magnetic alloys, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the design),
• The ability for custom shaping as well as adaptation to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Important function in advanced technical fields – they are used in HDDs, rotating machines, clinical machines and high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in compact dimensions, which allows for use in miniature devices

Disadvantages of magnetic elements:

• They can break when subjected to a strong impact. If the magnets are exposed to mechanical hits, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time strengthens its overall robustness,
• They lose field intensity at extreme temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the form 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 advisable 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 restricted,
• Possible threat from tiny pieces may arise, in case of ingestion, which is crucial in the health of young users. Furthermore, miniature parts from these assemblies may complicate medical imaging after being swallowed,
• Due to expensive raw materials, their cost is considerably higher,

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

The given holding capacity of the magnet represents the highest holding force, calculated in ideal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• at room temperature

Practical lifting capacity: influencing factors

The lifting capacity of a magnet depends on in practice key elements, from primary to secondary:

• Air gap between the magnet and the plate, as 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.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the load capacity is reduced by as much as 75%. In addition, even a small distance {between} the magnet’s surface and the plate reduces the holding force.