MW 29x10 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their exceptional magnetic power, neodymium magnets offer the following advantages:

• They do not lose their magnetism, even after nearly 10 years – the decrease of power is only ~1% (according to tests),
• They are very resistant to demagnetization caused by external field interference,
• Thanks to the shiny finish and nickel coating, they have an visually attractive appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• The ability for accurate shaping or customization to custom needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Important function in cutting-edge sectors – they are used in HDDs, rotating machines, clinical machines along with high-tech tools,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to external force, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time enhances its overall robustness,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent loss 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 damp environment. For outdoor use, we recommend using moisture-resistant magnets, such as those made of polymer,
• Limited ability to create complex details in the magnet – the use of a housing is recommended,
• Possible threat from tiny pieces may arise, if ingested accidentally, which is significant in the health of young users. Additionally, small elements from these assemblies can complicate medical imaging after being swallowed,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Magnetic strength at its maximum – what it depends on?

The given lifting capacity of the magnet corresponds to the maximum lifting force, measured in the best circumstances, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• under standard ambient temperature

Lifting capacity in real conditions – factors

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

• Air gap between the magnet and the plate, because 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 was determined by applying a steel plate with a smooth surface of optimal thickness (min. 20 mm), under vertically applied force, 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 decreases the load capacity.