SM 32x500 [2xM8] / N42 - magnetic separator

Strengths and weaknesses of NdFeB magnets.

In addition to their magnetic capacity, neodymium magnets provide the following advantages:

• They do not lose magnetism, even over nearly 10 years – the drop in power is only ~1% (according to tests),
• They feature excellent resistance to magnetism drop due to external fields,
• By applying a reflective layer of gold, the element acquires an professional look,
• Magnetic induction on the top side of the magnet turns out to be impressive,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and are able to act (depending on the shape) even at a temperature of 230°C or more...
• Thanks to freedom in designing and the ability to customize to complex applications,
• Key role in innovative solutions – they are used in mass storage devices, brushless drives, precision medical tools, also complex engineering applications.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Drawbacks and weaknesses of neodymium magnets and proposals for their use:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a special holder, which not only secures them against impacts but also raises their durability
• NdFeB magnets lose power when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (a factor is the shape and dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
• When exposed to humidity, magnets usually rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation as well as corrosion.
• We recommend cover - magnetic mechanism, due to difficulties in producing threads inside the magnet and complex shapes.
• Health risk resulting from small fragments of magnets can be dangerous, when accidentally swallowed, which becomes key in the context of child health protection. It is also worth noting that tiny parts of these devices can complicate diagnosis medical after entering the body.
• With large orders the cost of neodymium magnets is economically unviable,

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

The specified lifting capacity concerns the maximum value, obtained under laboratory conditions, namely:

• on a plate made of structural steel, optimally conducting the magnetic field
• whose transverse dimension equals approx. 10 mm
• with an ideally smooth touching surface
• with direct contact (no impurities)
• during detachment in a direction perpendicular to the mounting surface
• at ambient temperature room level

Determinants of lifting force in real conditions

In practice, the actual holding force is determined by a number of factors, listed from the most important:

• Gap (between the magnet and the plate), because even a tiny clearance (e.g. 0.5 mm) can cause a reduction in force by up to 50% (this also applies to paint, rust or debris).
• Direction of force – highest force is reached only during perpendicular pulling. The shear force of the magnet along the surface is typically several times lower (approx. 1/5 of the lifting capacity).
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of converting into lifting capacity.
• Material composition – different alloys attracts identically. Alloy additives weaken the attraction effect.
• Surface condition – smooth surfaces ensure maximum contact, which increases force. Uneven metal weaken the grip.
• Thermal environment – heating the magnet results in weakening of induction. It is worth remembering the thermal limit for a given model.

* Lifting capacity was assessed by applying a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, in contrast under shearing force the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate lowers the load capacity.