BM 450x180x70 [4x M8] - magnetic beam

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (according to literature),
• They show superior resistance to demagnetization from external magnetic fields,
• By applying a reflective layer of silver, the element gains a sleek look,
• They possess strong magnetic force measurable at the magnet’s surface,
• With the right combination of compounds, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the structure),
• The ability for accurate shaping as well as adjustment to individual needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which extends the scope of their use cases,
• Significant impact in modern technologies – they are utilized in hard drives, rotating machines, medical equipment along with technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from damage and additionally strengthens its overall durability,
• They lose strength at elevated 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 humid environment. If exposed to rain, we recommend using sealed magnets, such as those made of non-metallic materials,
• Limited ability to create threads in the magnet – the use of a mechanical support is recommended,
• Potential hazard due to small fragments may arise, in case of ingestion, which is crucial in the context of child safety. Additionally, small elements from these magnets may complicate medical imaging when ingested,
• Due to a complex production process, their cost is considerably higher,

Maximum holding power of the magnet – what affects it?

The given strength of the magnet represents the optimal strength, determined in the best circumstances, that is:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• under standard ambient temperature

Lifting capacity in practice – influencing factors

In practice, the holding capacity of a magnet is affected by the following aspects, from crucial to less important:

• 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 checked on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the lifting capacity is smaller. Additionally, even a small distance {between} the magnet’s surface and the plate lowers the lifting capacity.