SM 18x275 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They retain their attractive force for around 10 years – the drop is just ~1% (based on simulations),
• They remain magnetized despite exposure to magnetic surroundings,
• The use of a polished nickel surface provides a eye-catching finish,
• They possess strong magnetic force measurable at the magnet’s surface,
• With the right combination of compounds, they reach significant thermal stability, enabling operation at or above 230°C (depending on the structure),
• Thanks to the possibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which increases their application range,
• Wide application in modern technologies – they serve a purpose in data storage devices, electric drives, healthcare devices along with sophisticated instruments,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of magnetic elements:

• They can break when subjected to a sudden impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage , and at the same time increases its overall resistance,
• Magnets lose pulling force 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 wise to use sealed magnets made of plastic for outdoor use,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is difficult,
• Possible threat related to magnet particles may arise, when consumed by mistake, which is significant in the family environments. It should also be noted that minuscule fragments from these magnets can hinder health screening after being swallowed,
• In cases of tight budgets, neodymium magnet cost may be a barrier,

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

The given lifting capacity of the magnet represents the maximum lifting force, calculated in the best circumstances, that is:

• 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 no separation
• in a perpendicular direction of force
• in normal thermal conditions

Determinants of lifting force in real conditions

The lifting capacity of a magnet is influenced by in practice key elements, from primary to secondary:

• 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 was assessed with the use of a polished steel plate of suitable thickness (min. 20 mm), under vertically applied force, whereas under shearing force the holding force is lower. Additionally, even a minimal clearance {between} the magnet and the plate reduces the load capacity.