SM 18x300 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of rare earth magnets.

Besides their tremendous pulling force, neodymium magnets offer the following advantages:

• They virtually do not lose power, because even after ten years the performance loss is only ~1% (according to literature),
• Magnets perfectly protect themselves against demagnetization caused by ambient magnetic noise,
• Thanks to the reflective finish, the coating of nickel, gold, or silver-plated gives an visually attractive appearance,
• They show high magnetic induction at the operating surface, which improves attraction properties,
• Through (appropriate) combination of ingredients, they can achieve high thermal resistance, allowing for functioning at temperatures reaching 230°C and above...
• Thanks to modularity in constructing and the ability to modify to individual projects,
• Huge importance in advanced technology sectors – they are utilized in HDD drives, drive modules, medical equipment, as well as industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which makes them useful in small systems

Disadvantages of neodymium magnets:

• They are fragile upon too strong impacts. To avoid cracks, it is worth protecting magnets in a protective case. Such protection not only shields the magnet but also increases its resistance to damage
• When exposed to high temperature, neodymium magnets experience a drop in force. 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
• Magnets exposed to a humid environment can rust. Therefore when using outdoors, we advise using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• Due to limitations in creating threads and complex shapes in magnets, we propose using casing - magnetic mechanism.
• Health risk related to microscopic parts of magnets are risky, when accidentally swallowed, which becomes key in the aspect of protecting the youngest. Additionally, small elements of these magnets can complicate diagnosis medical when they are in the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Best holding force of the magnet in ideal parameters – what contributes to it?

Information about lifting capacity is the result of a measurement for optimal configuration, including:

• using a sheet made of high-permeability steel, serving as a magnetic yoke
• possessing a thickness of minimum 10 mm to avoid saturation
• with an ideally smooth contact surface
• under conditions of no distance (metal-to-metal)
• for force applied at a right angle (pull-off, not shear)
• in neutral thermal conditions

Magnet lifting force in use – key factors

Bear in mind that the magnet holding will differ depending on elements below, in order of importance:

• Air gap (between the magnet and the plate), as even a very small distance (e.g. 0.5 mm) results in a reduction in lifting capacity by up to 50% (this also applies to varnish, corrosion or dirt).
• Force direction – note that the magnet has greatest strength perpendicularly. Under sliding down, the holding force drops drastically, often to levels of 20-30% of the maximum value.
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet limits the lifting capacity (the magnet "punches through" it).
• Metal type – different alloys reacts the same. Alloy additives worsen the interaction with the magnet.
• Surface structure – the smoother and more polished the surface, the larger the contact zone and stronger the hold. Unevenness acts like micro-gaps.
• Temperature influence – high temperature weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the load capacity is reduced by as much as 75%. In addition, even a minimal clearance {between} the magnet’s surface and the plate decreases the lifting capacity.