SM 32x100 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They retain their magnetic properties for nearly 10 years – the loss is just ~1% (in theory),
• They protect against demagnetization induced by surrounding electromagnetic environments remarkably well,
• Thanks to the glossy finish and silver coating, they have an elegant appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Thanks to their exceptional temperature resistance, they can operate (depending on the geometry) even at temperatures up to 230°C or more,
• The ability for accurate shaping as well as customization to individual needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Significant impact in modern technologies – they serve a purpose in HDDs, electromechanical systems, healthcare devices or even other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to external force, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and increases its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Magnets exposed to wet conditions can oxidize. Therefore, for outdoor applications, it's best to use waterproof types made of non-metallic composites,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Health risk related to magnet particles may arise, especially if swallowed, which is crucial in the health of young users. It should also be noted that small elements from these devices may hinder health screening once in the system,
• Due to a complex production process, their cost is considerably higher,

Detachment force of the magnet in optimal conditions – what it depends on?

The given holding capacity of the magnet means the highest holding force, calculated in the best circumstances, 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
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing factors

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

• 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 measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under parallel forces the load capacity is reduced by as much as 75%. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the lifting capacity.