SM 32x300 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They retain their attractive force for around ten years – the loss is just ~1% (based on simulations),
• They protect against demagnetization induced by surrounding magnetic influence very well,
• Thanks to the glossy finish and nickel coating, they have an visually attractive appearance,
• The outer field strength of the magnet shows advanced magnetic properties,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• The ability for accurate shaping or adaptation to custom needs – neodymium magnets can be manufactured in many forms and dimensions, which amplifies their functionality across industries,
• Significant impact in cutting-edge sectors – they find application in HDDs, electromechanical systems, diagnostic apparatus or even technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in compact dimensions, which makes them ideal in compact constructions

Disadvantages of neodymium magnets:

• They are fragile when subjected to a powerful impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks and additionally increases its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on form). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• They rust in a moist environment – during outdoor use, we recommend using encapsulated magnets, such as those made of rubber,
• Limited ability to create complex details in the magnet – the use of a magnetic holder is recommended,
• Potential hazard related to magnet particles may arise, in case of ingestion, which is important in the context of child safety. Additionally, minuscule fragments from these magnets may complicate medical imaging once in the system,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Breakaway strength of the magnet in ideal conditions – what it depends on?

The given lifting capacity of the magnet corresponds to the maximum lifting force, calculated in ideal conditions, namely:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• with no separation
• in a perpendicular direction of force
• under standard ambient temperature

Practical lifting capacity: 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, 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 checked on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under parallel forces the load capacity is reduced by as much as 5 times. In addition, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.