SM 32x425 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of NdFeB magnets.

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

• Their strength is durable, and after approximately ten years it drops only by ~1% (according to research),
• They do not lose their magnetic properties even under external field action,
• In other words, due to the metallic finish of nickel, the element becomes visually attractive,
• The surface of neodymium magnets generates a intense magnetic field – this is one of their assets,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
• Thanks to flexibility in constructing and the capacity to modify to client solutions,
• Fundamental importance in modern technologies – they are commonly used in mass storage devices, motor assemblies, diagnostic systems, as well as multitasking production systems.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Drawbacks and weaknesses of neodymium magnets: weaknesses and usage proposals

• Brittleness is one of their disadvantages. Upon intense impact they can break. We advise keeping them in a special holder, which not only secures them against impacts but also raises their durability
• Neodymium magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• They oxidize in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited possibility of making nuts in the magnet and complicated shapes - preferred is casing - magnetic holder.
• Health risk to health – tiny shards of magnets can be dangerous, if swallowed, which gains importance in the aspect of protecting the youngest. Furthermore, small components of these magnets can be problematic in diagnostics medical after entering the body.
• Due to complex production process, their price is relatively high,

Highest magnetic holding force – what it depends on?

Information about lifting capacity was determined for the most favorable conditions, assuming:

• with the use of a yoke made of low-carbon steel, guaranteeing full magnetic saturation
• with a cross-section minimum 10 mm
• with an polished touching surface
• without the slightest insulating layer between the magnet and steel
• under axial force direction (90-degree angle)
• at room temperature

Key elements affecting lifting force

During everyday use, the actual lifting capacity is determined by a number of factors, ranked from most significant:

• Space between magnet and steel – every millimeter of distance (caused e.g. by varnish or dirt) significantly weakens the pulling force, often by half at just 0.5 mm.
• Angle of force application – maximum parameter is obtained only during pulling at a 90° angle. The shear force of the magnet along the surface is typically several times smaller (approx. 1/5 of the lifting capacity).
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet limits the lifting capacity (the magnet "punches through" it).
• Material type – the best choice is pure iron steel. Hardened steels may attract less.
• Surface finish – full contact is possible only on smooth steel. Rough texture reduce the real contact area, weakening the magnet.
• Heat – neodymium magnets have a negative temperature coefficient. When it is hot they lose power, and at low temperatures gain strength (up to a certain limit).

* Holding force was tested on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the holding force is lower. Moreover, even a small distance {between} the magnet and the plate lowers the lifting capacity.