BM 650x180x70 [4x M8] - magnetic beam

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their pulling strength, neodymium magnets provide the following advantages:

• They virtually do not lose strength, because even after ten years, the performance loss is only ~1% (in laboratory conditions),
• They protect against demagnetization induced by ambient magnetic influence remarkably well,
• Because of the brilliant layer of nickel, the component looks aesthetically refined,
• They have exceptional magnetic induction on the surface of the magnet,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for customized forming and personalized design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Key role in new technology industries – they serve a purpose in computer drives, electromechanical systems, diagnostic apparatus and high-tech tools,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to external force, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture while also enhances its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). 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,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of plastic for outdoor use,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is not feasible,
• Possible threat linked to microscopic shards may arise, if ingested accidentally, which is important in the family environments. Moreover, small elements from these magnets may interfere with diagnostics after being swallowed,
• Due to the price of neodymium, their cost is considerably higher,

Maximum holding power of the magnet – what affects it?

The given pulling force of the magnet represents the maximum force, assessed in a perfect environment, namely:

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

Lifting capacity in practice – influencing factors

Practical lifting force is determined by elements, by priority:

• Air gap between the magnet and the plate, since 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.

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under perpendicular forces, in contrast under parallel forces the holding force is lower. In addition, even a minimal clearance {between} the magnet and the plate lowers the holding force.