MW 20x5 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their stability, neodymium magnets are valued for these benefits:

• They do not lose their magnetism, even after around 10 years – the decrease of power is only ~1% (based on measurements),
• They show strong resistance to demagnetization from outside magnetic sources,
• Thanks to the polished finish and silver coating, they have an elegant appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• Thanks to their high temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for customized forming and targeted design, these magnets can be produced in various shapes and sizes, greatly improving design adaptation,
• Key role in cutting-edge sectors – they are utilized in computer drives, electromechanical systems, healthcare devices and sophisticated instruments,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to shocks, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks and reinforces its overall strength,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s profile). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a wet environment. If exposed to rain, we recommend using moisture-resistant magnets, such as those made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing complex structures directly in the magnet,
• Safety concern due to small fragments may arise, especially if swallowed, which is notable in the context of child safety. Furthermore, minuscule fragments from these magnets have the potential to complicate medical imaging after being swallowed,
• In cases of large-volume purchasing, neodymium magnet cost may be a barrier,

Maximum lifting capacity of the magnet – what it depends on?

The given pulling force of the magnet corresponds to the maximum force, calculated under optimal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• with vertical force applied
• at room temperature

Lifting capacity in practice – influencing factors

Practical lifting force is dependent on factors, by priority:

• 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 assessed by applying a polished steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, whereas under shearing force the holding force is lower. In addition, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.