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

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They retain their full power for almost ten years – the drop is just ~1% (in theory),
• They are extremely resistant to demagnetization caused by external field interference,
• Thanks to the shiny finish and gold coating, they have an visually attractive appearance,
• They possess strong magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• With the option for tailored forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Wide application in new technology industries – they are utilized in data storage devices, rotating machines, diagnostic apparatus and high-tech tools,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to shocks, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage while also 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 shape 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 rubber,
• Limited ability to create internal holes in the magnet – the use of a external casing is recommended,
• Potential hazard linked to microscopic shards may arise, in case of ingestion, which is important in the health of young users. Furthermore, minuscule fragments from these products may disrupt scanning after being swallowed,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum lifting force for a neodymium magnet – what it depends on?

The given lifting capacity of the magnet means the maximum lifting force, determined in ideal conditions, specifically:

• with mild steel, serving as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Practical aspects of lifting capacity – factors

The lifting capacity of a magnet is determined by in practice the following factors, from primary to secondary:

• 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.

* Lifting capacity was determined with the use of a smooth steel plate of suitable thickness (min. 20 mm), under vertically applied force, however under attempts to slide the magnet the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the load capacity.