BM 380x180x70 [4x M8] - magnetic beam

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have constant strength, and over nearly 10 years their performance decreases symbolically – ~1% (in testing),
• Their ability to resist magnetic interference from external fields is impressive,
• In other words, due to the glossy gold coating, the magnet obtains an professional appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• 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 usage potential,
• Wide application in advanced technical fields – they are used in computer drives, electromechanical systems, diagnostic apparatus along with sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to mechanical hits, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time strengthens its overall durability,
• High temperatures may significantly reduce the magnetic power of neodymium magnets. Typically, above 80°C, they experience permanent loss 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,
• They rust in a wet environment, especially when used outside, we recommend using encapsulated magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is restricted,
• Health risk linked to microscopic shards may arise, if ingested accidentally, which is important in the protection of children. Furthermore, tiny components from these magnets may hinder health screening when ingested,
• Due to the price of neodymium, their cost is above average,

Maximum lifting capacity of the magnet – what affects it?

The given pulling force of the magnet corresponds to the maximum force, assessed in the best circumstances, namely:

• with mild steel, serving as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a polished side
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing factors

The lifting capacity of a magnet depends on in practice the following factors, ordered from most important to least 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 parallel forces the load capacity is reduced by as much as 5 times. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.