SM 32x425 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their immense magnetic power, neodymium magnets offer the following advantages:

• Their power is durable, and after approximately 10 years, it drops only by ~1% (according to research),
• They protect against demagnetization induced by ambient electromagnetic environments effectively,
• Because of the reflective layer of gold, the component looks aesthetically refined,
• They possess significant magnetic force measurable at the magnet’s surface,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• With the option for fine forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Wide application in advanced technical fields – they are utilized in data storage devices, electromechanical systems, healthcare devices or even sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, with minimal size,

Disadvantages of magnetic elements:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to mechanical hits, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall strength,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (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 humidity can rust. Therefore, for outdoor applications, we recommend waterproof types made of rubber,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing fine shapes directly in the magnet,
• Safety concern from tiny pieces may arise, in case of ingestion, which is crucial in the health of young users. Furthermore, small elements from these magnets might complicate medical imaging once in the system,
• In cases of large-volume purchasing, neodymium magnet cost is a challenge,

Breakaway strength of the magnet in ideal conditions – what affects it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, measured in a perfect environment, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with zero air gap
• with vertical force applied
• at room temperature

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is conditioned 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) 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 measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the holding force is lower. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the holding force.