SM 25x175 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their durability, neodymium magnets are valued for these benefits:

• Their power remains stable, and after approximately 10 years, it drops only by ~1% (according to research),
• Their ability to resist magnetic interference from external fields is notable,
• In other words, due to the shiny silver coating, the magnet obtains an aesthetic appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Thanks to their high temperature resistance, they can operate (depending on the geometry) even at temperatures up to 230°C or more,
• With the option for customized forming and targeted design, these magnets can be produced in multiple shapes and sizes, greatly improving engineering flexibility,
• Wide application in cutting-edge sectors – they are utilized in HDDs, rotating machines, medical equipment as well as sophisticated instruments,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to physical collisions, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and increases its overall durability,
• They lose field intensity 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,
• Magnets exposed to moisture can oxidize. Therefore, for outdoor applications, it's best to use waterproof types made of coated materials,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Health risk related to magnet particles may arise, in case of ingestion, which is significant in the family environments. Additionally, tiny components from these devices might disrupt scanning when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Highest magnetic holding force – what affects it?

The given holding capacity of the magnet means the highest holding force, assessed in ideal conditions, that is:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• at room temperature

What influences lifting capacity in practice

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

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

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the load capacity is reduced by as much as fivefold. In addition, even a minimal clearance {between} the magnet and the plate decreases the load capacity.