MPL 40x18x10 SH / N38 - lamellar magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional field intensity, neodymium magnets offer the following advantages:

• They have stable power, and over more than 10 years their attraction force decreases symbolically – ~1% (in testing),
• They show exceptional resistance to demagnetization from outside magnetic sources,
• Because of the lustrous layer of silver, the component looks aesthetically refined,
• Magnetic induction on the surface of these magnets is very strong,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• Thanks to the possibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in various configurations, which broadens their functional possibilities,
• Key role in new technology industries – they are utilized in HDDs, rotating machines, healthcare devices as well as technologically developed systems,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of rare earth magnets:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to external force, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage while also strengthens its overall resistance,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing fine shapes directly in the magnet,
• Possible threat linked to microscopic shards may arise, especially if swallowed, which is important in the family environments. It should also be noted that miniature parts from these assemblies might disrupt scanning if inside the body,
• Due to a complex production process, their cost is above average,

Maximum lifting force for a neodymium magnet – what it depends on?

The given pulling force of the magnet represents the maximum force, assessed under optimal conditions, that is:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• in conditions of no clearance
• in a perpendicular direction of force
• at room temperature

Determinants of lifting force in real conditions

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) 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 was assessed using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under vertically applied force, however under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet and the plate lowers the load capacity.