SM 18x150 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets.

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

• Their magnetic field is maintained, and after around 10 years it decreases only by ~1% (theoretically),
• They possess excellent resistance to magnetism drop as a result of opposing magnetic fields,
• Thanks to the elegant finish, the plating of nickel, gold-plated, or silver-plated gives an elegant appearance,
• The surface of neodymium magnets generates a maximum magnetic field – this is one of their assets,
• Through (appropriate) combination of ingredients, they can achieve high thermal strength, allowing for functioning at temperatures approaching 230°C and above...
• Possibility of precise machining and optimizing to specific requirements,
• Significant place in modern industrial fields – they are used in mass storage devices, brushless drives, advanced medical instruments, as well as industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which enables their usage in compact constructions

What to avoid - cons of neodymium magnets and ways of using them

• Brittleness is one of their disadvantages. Upon intense impact they can break. We advise keeping them in a special holder, which not only protects them against impacts but also raises their durability
• NdFeB magnets demagnetize 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
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• Due to limitations in realizing threads and complicated forms in magnets, we propose using cover - magnetic mount.
• Health risk related to microscopic parts of magnets can be dangerous, when accidentally swallowed, which becomes key in the context of child safety. Additionally, small elements of these devices can be problematic in diagnostics 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

Maximum magnetic pulling force – what it depends on?

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

• using a base made of low-carbon steel, acting as a circuit closing element
• with a cross-section minimum 10 mm
• with an polished contact surface
• without any air gap between the magnet and steel
• during detachment in a direction vertical to the mounting surface
• at temperature approx. 20 degrees Celsius

Determinants of lifting force in real conditions

Bear in mind that the working load may be lower depending on the following factors, starting with the most relevant:

• Distance – the presence of foreign body (paint, dirt, gap) interrupts the magnetic circuit, which reduces power rapidly (even by 50% at 0.5 mm).
• Load vector – highest force is reached only during perpendicular pulling. The force required to slide of the magnet along the plate is typically several times lower (approx. 1/5 of the lifting capacity).
• Metal thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field passes through the material instead of generating force.
• Material composition – not every steel attracts identically. High carbon content worsen the attraction effect.
• Smoothness – full contact is possible only on smooth steel. Any scratches and bumps reduce the real contact area, reducing force.
• Thermal factor – high temperature weakens magnetic field. Too high temperature can permanently demagnetize the magnet.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under shearing force the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet and the plate reduces the load capacity.