SM 25x200 [2xM8] / N42 - magnetic separator

Pros and cons of NdFeB magnets.

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

• They have constant strength, and over around 10 years their attraction force decreases symbolically – ~1% (in testing),
• They have excellent resistance to magnetic field loss due to external magnetic sources,
• A magnet with a metallic silver surface has an effective appearance,
• The surface of neodymium magnets generates a powerful magnetic field – this is a distinguishing feature,
• Through (appropriate) combination of ingredients, they can achieve high thermal resistance, enabling operation at temperatures reaching 230°C and above...
• Thanks to freedom in designing and the capacity to modify to client solutions,
• Significant place in advanced technology sectors – they serve a role in hard drives, brushless drives, diagnostic systems, and industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which allows their use in compact constructions

Problematic aspects of neodymium magnets and proposals for their use:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can break. We advise keeping them in a steel housing, which not only protects them against impacts but also raises their durability
• When exposed to high temperature, neodymium magnets experience a drop in strength. Often, when the temperature exceeds 80°C, their power 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 rust in a humid environment - during use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• Limited ability of producing threads in the magnet and complex shapes - preferred is casing - mounting mechanism.
• Potential hazard to health – tiny shards of magnets are risky, in case of ingestion, which gains importance in the aspect of protecting the youngest. Furthermore, small components of these magnets can complicate diagnosis medical after entering the body.
• Due to complex production process, their price is higher than average,

Maximum magnetic pulling force – what contributes to it?

Holding force of 0 kg is a measurement result executed under specific, ideal conditions:

• on a block made of structural steel, perfectly concentrating the magnetic field
• possessing a massiveness of min. 10 mm to avoid saturation
• with an ideally smooth touching surface
• with direct contact (no paint)
• during pulling in a direction perpendicular to the plane
• at standard ambient temperature

Determinants of practical lifting force of a magnet

Holding efficiency is influenced by specific conditions, such as (from priority):

• Gap (betwixt the magnet and the plate), because even a microscopic distance (e.g. 0.5 mm) leads to a drastic drop in lifting capacity by up to 50% (this also applies to varnish, rust or debris).
• Pull-off angle – note that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Wall thickness – thin material does not allow full use of the magnet. Magnetic flux passes through the material instead of generating force.
• Steel grade – the best choice is high-permeability steel. Stainless steels may generate lower lifting capacity.
• Plate texture – ground elements ensure maximum contact, which increases force. Uneven metal reduce efficiency.
• Heat – NdFeB sinters have a sensitivity to temperature. When it is hot they lose power, and in frost they can be stronger (up to a certain limit).

* Holding force was tested on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet’s surface and the plate decreases the lifting capacity.