SMZR 32x175 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their consistent power, neodymium magnets have these key benefits:

• They virtually do not lose strength, because even after ten years, the performance loss is only ~1% (based on calculations),
• They remain magnetized despite exposure to strong external fields,
• In other words, due to the shiny gold coating, the magnet obtains an stylish appearance,
• They have very high magnetic induction on the surface of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• The ability for precise shaping and adjustment to custom needs – neodymium magnets can be manufactured in multiple variants of geometries, which enhances their versatility in applications,
• Important function in new technology industries – they serve a purpose in hard drives, electric motors, clinical machines or even technologically developed systems,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, with minimal size,

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a sudden 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 breakage and additionally increases 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 form). 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 common to use sealed magnets made of rubber for outdoor use,
• Limited ability to create internal holes in the magnet – the use of a housing is recommended,
• Potential hazard from tiny pieces may arise, if ingested accidentally, which is notable in the context of child safety. It should also be noted that minuscule fragments from these assemblies have the potential to interfere with diagnostics once in the system,
• In cases of tight budgets, neodymium magnet cost may not be economically viable,

Detachment force of the magnet in optimal conditions – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, calculated under optimal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Lifting capacity in real conditions – factors

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• Air gap between the magnet and the plate, since 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 a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Moreover, even a small distance {between} the magnet’s surface and the plate decreases the holding force.