SM 25x250 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their high retention, neodymium magnets are valued for these benefits:

• They have stable power, and over more than 10 years their performance decreases symbolically – ~1% (according to theory),
• They protect against demagnetization induced by surrounding magnetic fields effectively,
• Because of the lustrous layer of gold, the component looks aesthetically refined,
• The outer field strength of the magnet shows remarkable magnetic properties,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• The ability for accurate shaping as well as customization to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which amplifies their functionality across industries,
• Wide application in cutting-edge sectors – they find application in computer drives, rotating machines, healthcare devices or even high-tech tools,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of magnetic elements:

• They can break when subjected to a strong impact. If the magnets are exposed to external force, 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 magnetic decay (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,
• They rust in a moist environment. For outdoor use, we recommend using moisture-resistant magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Health risk linked to microscopic shards may arise, if ingested accidentally, which is crucial in the health of young users. Additionally, minuscule fragments from these devices might complicate medical imaging after being swallowed,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The given holding capacity of the magnet represents the highest holding force, determined under optimal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• in a perpendicular direction of force
• at room temperature

Impact of factors on magnetic holding capacity in practice

Practical lifting force is determined by factors, 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 was determined with the use of a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, whereas under shearing force the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.