SM 25x250 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

Besides their tremendous strength, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over more than ten years their performance decreases symbolically – ~1% (according to theory),
• Neodymium magnets are extremely resistant to loss of magnetic properties caused by magnetic disturbances,
• A magnet with a shiny nickel surface has an effective appearance,
• Magnets have maximum magnetic induction on the outer side,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Thanks to modularity in constructing and the capacity to adapt to complex applications,
• Key role in modern industrial fields – they are used in mass storage devices, electric motors, medical devices, as well as other advanced devices.
• Compactness – despite small sizes they provide effective action, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• To avoid cracks upon strong impacts, we recommend using special steel holders. Such a solution secures the magnet and simultaneously improves its durability.
• When exposed to high temperature, neodymium magnets experience a drop in strength. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size and shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They oxidize in a humid environment. For use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
• Due to limitations in creating nuts and complex forms in magnets, we recommend using a housing - magnetic mount.
• Health risk to health – tiny shards of magnets can be dangerous, if swallowed, which becomes key in the context of child safety. It is also worth noting that small components of these devices can disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Optimal lifting capacity of a neodymium magnet – what contributes to it?

Magnet power was determined for ideal contact conditions, assuming:

• on a base made of mild steel, perfectly concentrating the magnetic field
• possessing a massiveness of min. 10 mm to avoid saturation
• with an ground touching surface
• with zero gap (without paint)
• under axial force direction (90-degree angle)
• at room temperature

Lifting capacity in real conditions – factors

Holding efficiency is affected by specific conditions, including (from priority):

• Gap (betwixt the magnet and the metal), because even a tiny clearance (e.g. 0.5 mm) can cause a reduction in lifting capacity by up to 50% (this also applies to paint, rust or debris).
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Element thickness – for full efficiency, the steel must be adequately massive. Thin sheet limits the lifting capacity (the magnet "punches through" it).
• Chemical composition of the base – low-carbon steel attracts best. Alloy steels decrease magnetic permeability and lifting capacity.
• Smoothness – ideal contact is possible only on smooth steel. Any scratches and bumps create air cushions, reducing force.
• Heat – neodymium magnets have a sensitivity to temperature. When it is hot they are weaker, and in frost gain strength (up to a certain limit).

* Holding force was tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet’s surface and the plate lowers the load capacity.