MW 20x2.5 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• They do not lose their power nearly 10 years – the loss of lifting capacity is only ~1% (according to tests),
• They are highly resistant to demagnetization caused by external magnetic fields,
• Thanks to the glossy finish and silver coating, they have an aesthetic appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• With the option for tailored forming and targeted design, these magnets can be produced in multiple shapes and sizes, greatly improving engineering flexibility,
• Important function in modern technologies – they are utilized in HDDs, electric drives, clinical machines as well as sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which makes them useful in small systems

Disadvantages of NdFeB magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and additionally enhances 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 structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to wet conditions can rust. Therefore, for outdoor applications, we suggest waterproof types made of coated materials,
• Limited ability to create threads in the magnet – the use of a magnetic holder is recommended,
• Safety concern related to magnet particles may arise, especially if swallowed, which is notable in the family environments. It should also be noted that small elements from these magnets have the potential to interfere with diagnostics if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what contributes to it?

The given pulling force of the magnet means the maximum force, calculated in the best circumstances, specifically:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing 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, as 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.

* Lifting capacity testing was performed on a smooth plate of suitable thickness, under a perpendicular pulling force, whereas under parallel forces the lifting capacity is smaller. In addition, even a small distance {between} the magnet and the plate reduces the lifting capacity.