MW 10x10 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They do not lose their power nearly ten years – the decrease of strength is only ~1% (according to tests),
• They show strong resistance to demagnetization from outside magnetic sources,
• Thanks to the glossy finish and nickel coating, they have an visually attractive appearance,
• They have very high magnetic induction on the surface of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• With the option for tailored forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Wide application in modern technologies – they are utilized in HDDs, electromechanical systems, clinical machines and other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in tiny dimensions, which makes them ideal in miniature devices

Disadvantages of NdFeB magnets:

• They can break when subjected to a heavy impact. If the magnets are exposed to shocks, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage , and at the same time reinforces its overall strength,
• They lose strength at high temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the form and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a damp environment, especially when used outside, we recommend using waterproof magnets, such as those made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing threads directly in the magnet,
• Possible threat linked to microscopic shards may arise, especially if swallowed, which is significant in the health of young users. Furthermore, small elements from these devices can interfere with diagnostics if inside the body,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Detachment force of the magnet in optimal conditions – what affects it?

The given strength of the magnet means the optimal strength, calculated in the best circumstances, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Determinants of lifting force in real conditions

The lifting capacity of a magnet is determined by in practice key elements, ordered from most important to least 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 a perpendicular force was applied, in contrast under shearing force the load capacity is reduced by as much as 5 times. Additionally, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.