SM 25x300 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their tremendous strength, neodymium magnets offer the following advantages:

• They have stable power, and over more than ten years their performance decreases symbolically – ~1% (according to theory),
• They remain magnetized despite exposure to magnetic surroundings,
• Thanks to the shiny finish and silver coating, they have an visually attractive appearance,
• They possess significant 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 magnetic form),
• The ability for custom shaping and adjustment to individual needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which amplifies their functionality across industries,
• Important function in advanced technical fields – they find application in HDDs, electromechanical systems, medical equipment along with sophisticated instruments,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to physical collisions, it is advisable to use in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture and additionally reinforces its overall durability,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible performance loss (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 advisable to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing holes directly in the magnet,
• Potential hazard from tiny pieces may arise, especially if swallowed, which is important in the family environments. Furthermore, miniature parts from these assemblies have the potential to interfere with diagnostics when ingested,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum lifting capacity of the magnet – what affects it?

The given strength of the magnet represents the optimal strength, determined in ideal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• under perpendicular detachment force
• at room temperature

Magnet lifting force in use – key factors

In practice, the holding capacity of a magnet is affected by these factors, arranged from the most important to the least relevant:

• Air gap between the magnet and the plate, because 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 lifting capacity is smaller. Additionally, even a small distance {between} the magnet and the plate reduces the holding force.