SMZR 25x250 / N52 - magnetic separator with handle

Advantages and disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their strength is maintained, and after approximately 10 years, it drops only by ~1% (theoretically),
• They protect against demagnetization induced by surrounding electromagnetic environments remarkably well,
• By applying a bright layer of silver, the element gains a clean look,
• Magnetic induction on the surface of these magnets is impressively powerful,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• Thanks to the possibility in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in various configurations, which broadens their usage potential,
• Important function in advanced technical fields – they are utilized in HDDs, electric drives, healthcare devices and other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to mechanical hits, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture while also increases its overall strength,
• 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 form). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to damp air can rust. Therefore, for outdoor applications, we suggest waterproof types made of plastic,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is difficult,
• Safety concern linked to microscopic shards may arise, if ingested accidentally, which is significant in the family environments. It should also be noted that minuscule fragments from these products can interfere with diagnostics when ingested,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what contributes to it?

The given holding capacity of the magnet represents the highest holding force, assessed in the best circumstances, that is:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is conditioned by these factors, from crucial to less important:

• Air gap between the magnet and the plate, as even a very small distance (e.g. 0.5 mm) causes 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.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas 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 reduces the load capacity.