MPL 25x10x3 / N38 - lamellar magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• Their magnetic field remains stable, and after approximately 10 years, it drops only by ~1% (according to research),
• They remain magnetized despite exposure to magnetic noise,
• In other words, due to the metallic silver coating, the magnet obtains an stylish appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Thanks to their exceptional temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• Thanks to the flexibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in diverse shapes and sizes, which increases their application range,
• Significant impact in modern technologies – they serve a purpose in data storage devices, electric motors, medical equipment and sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in compact dimensions, which makes them useful in miniature devices

Disadvantages of magnetic elements:

• They may fracture when subjected to a sudden 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 robustness,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on size). 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,
• Magnets exposed to damp air can corrode. Therefore, for outdoor applications, it's best to use waterproof types made of coated materials,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is restricted,
• Possible threat related to magnet particles may arise, when consumed by mistake, which is important in the family environments. Moreover, small elements from these magnets may disrupt scanning if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Optimal lifting capacity of a neodymium magnet – what affects it?

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

• with mild steel, used as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

Practical lifting force is dependent on elements, listed from the most critical to the less significant:

• 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.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the holding force is lower. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the lifting capacity.