MPL 40x40x15 / N38 - lamellar magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their magnetism, even after nearly 10 years – the loss of power is only ~1% (based on measurements),
• They remain magnetized despite exposure to magnetic noise,
• Because of the reflective layer of nickel, the component looks visually appealing,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• The ability for precise shaping and customization to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Wide application in modern technologies – they serve a purpose in hard drives, electric motors, clinical machines as well as high-tech tools,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to shocks, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage while also reinforces its overall strength,
• They lose strength at high temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of protective material for outdoor use,
• Limited ability to create threads in the magnet – the use of a magnetic holder is recommended,
• Potential hazard linked to microscopic shards may arise, when consumed by mistake, which is crucial in the context of child safety. It should also be noted that miniature parts from these assemblies may disrupt scanning after being swallowed,
• In cases of large-volume purchasing, neodymium magnet cost may be a barrier,

Maximum lifting capacity of the magnet – what it depends on?

The given holding capacity of the magnet represents the highest holding force, determined in ideal conditions, that is:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Practical lifting capacity: influencing factors

The lifting capacity of a magnet is determined by in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, as 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 performed on a smooth plate of optimal thickness, under a perpendicular pulling force, however under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a small distance {between} the magnet’s surface and the plate lowers the holding force.