SM 32x275 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their immense pulling force, neodymium magnets offer the following advantages:

• They have stable power, and over nearly 10 years their performance decreases symbolically – ~1% (in testing),
• Their ability to resist magnetic interference from external fields is impressive,
• By applying a shiny layer of gold, the element gains a sleek look,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• Thanks to their high temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• The ability for accurate shaping and adaptation to custom needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which enhances their versatility in applications,
• Important function in modern technologies – they find application in data storage devices, electric motors, clinical machines as well as sophisticated instruments,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to mechanical hits, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks while also reinforces its overall strength,
• They lose magnetic force at elevated temperatures. Most neodymium magnets experience permanent decline 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,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of synthetic coating for outdoor use,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Safety concern due to small fragments may arise, in case of ingestion, which is crucial in the context of child safety. Furthermore, miniature parts from these assemblies have the potential to disrupt scanning if inside the body,
• In cases of tight budgets, neodymium magnet cost may not be economically viable,

Highest magnetic holding force – what it depends on?

The given strength of the magnet corresponds to the optimal strength, calculated under optimal conditions, namely:

• with mild steel, serving as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a smooth surface
• in conditions of no clearance
• with vertical force applied
• under standard ambient temperature

What influences lifting capacity in practice

Practical lifting force is determined by elements, by priority:

• 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 tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the holding force is lower. In addition, even a slight gap {between} the magnet and the plate lowers the holding force.