SM 32x150 [2xM8] / 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 constant strength, and over nearly ten years their attraction force decreases symbolically – ~1% (in testing),
• They show superior resistance to demagnetization from outside magnetic sources,
• By applying a shiny layer of gold, the element gains a modern look,
• The outer field strength of the magnet shows remarkable magnetic properties,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• Thanks to the freedom in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which broadens their usage potential,
• Significant impact in advanced technical fields – they are utilized in computer drives, electric drives, medical equipment and high-tech tools,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to mechanical hits, we recommend in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage and additionally increases its overall robustness,
• They lose strength at elevated temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the dimensions and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a humid environment, especially when used outside, we recommend using sealed magnets, such as those made of non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is restricted,
• Safety concern from tiny pieces may arise, if ingested accidentally, which is notable in the protection of children. Moreover, minuscule fragments from these assemblies can interfere with diagnostics when ingested,
• In cases of large-volume purchasing, neodymium magnet cost may be a barrier,

Detachment force of the magnet in optimal conditions – what it depends on?

The given lifting capacity of the magnet means the maximum lifting force, measured in a perfect environment, that is:

• using a steel plate with low carbon content, acting 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
• under standard ambient temperature

Lifting capacity in practice – influencing factors

Practical lifting force is determined by elements, listed from the most critical to the less significant:

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

* Lifting capacity testing was performed on plates with a smooth surface of optimal thickness, under perpendicular forces, in contrast under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet and the plate lowers the holding force.