SM 32x375 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They have constant strength, and over nearly ten years their attraction force decreases symbolically – ~1% (in testing),
• They remain magnetized despite exposure to strong external fields,
• Thanks to the shiny finish and gold coating, they have an aesthetic appearance,
• The outer field strength of the magnet shows remarkable magnetic properties,
• With the right combination of materials, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the form),
• With the option for tailored forming and targeted design, these magnets can be produced in numerous shapes and sizes, greatly improving design adaptation,
• Key role in new technology industries – they find application in HDDs, electric motors, healthcare devices along with other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which allows for use in miniature devices

Disadvantages of neodymium magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to physical collisions, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks and additionally reinforces its overall strength,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a humid environment – during outdoor use, we recommend using sealed magnets, such as those made of polymer,
• Limited ability to create threads in the magnet – the use of a magnetic holder is recommended,
• Health risk due to small fragments may arise, in case of ingestion, which is important in the family environments. Additionally, tiny components from these devices can disrupt scanning if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Best holding force of the magnet in ideal parameters – what affects it?

The given lifting capacity of the magnet means the maximum lifting force, calculated in ideal conditions, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• at room temperature

Lifting capacity in real conditions – factors

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

• 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 measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the load capacity is reduced by as much as 75%. In addition, even a slight gap {between} the magnet and the plate lowers the lifting capacity.