MPL 30x15x2 / N38 - lamellar magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They retain their full power for around 10 years – the drop is just ~1% (in theory),
• Their ability to resist magnetic interference from external fields is notable,
• In other words, due to the shiny nickel coating, the magnet obtains an aesthetic appearance,
• They possess strong magnetic force measurable at the magnet’s surface,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• Thanks to the possibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in different geometries, which increases their functional possibilities,
• Important function in advanced technical fields – they are used in data storage devices, electric drives, medical equipment or even high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which makes them ideal in compact constructions

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to physical collisions, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and increases its overall resistance,
• They lose power at extreme temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the dimensions and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a moist environment. For outdoor use, we recommend using waterproof magnets, such as those made of polymer,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing fine shapes directly in the magnet,
• Possible threat from tiny pieces may arise, especially if swallowed, which is significant in the context of child safety. Additionally, small elements from these devices may complicate medical imaging once in the system,
• Due to expensive raw materials, their cost is relatively high,

Best holding force of the magnet in ideal parameters – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, assessed in the best circumstances, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a smooth surface
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is conditioned by the following aspects, in descending order of importance:

• Air gap between the magnet and the plate, since 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 conducted on a smooth plate of optimal thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. In addition, even a minimal clearance {between} the magnet and the plate reduces the load capacity.