SM 32x350 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They retain their full power for nearly 10 years – the drop is just ~1% (according to analyses),
• Their ability to resist magnetic interference from external fields is impressive,
• Thanks to the glossy finish and nickel coating, they have an aesthetic appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• With the option for customized forming and precise design, these magnets can be produced in multiple shapes and sizes, greatly improving design adaptation,
• Wide application in advanced technical fields – they are used in computer drives, electric motors, clinical machines along with sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which allows for use in small systems

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to shocks, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage and additionally increases its overall durability,
• They lose magnetic force at high 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,
• Magnets exposed to humidity can corrode. Therefore, for outdoor applications, it's best to use waterproof types made of rubber,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is restricted,
• Potential hazard due to small fragments may arise, in case of ingestion, which is significant in the family environments. Furthermore, tiny components from these products have the potential to disrupt scanning when ingested,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Best holding force of the magnet in ideal parameters – what affects it?

The given holding capacity of the magnet represents the highest holding force, calculated under optimal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

Determinants of practical lifting force of a magnet

In practice, the holding capacity of a magnet is conditioned by the following aspects, in descending order of importance:

• 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 tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under parallel forces the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet and the plate lowers the holding force.