SM 32x350 [2xM8] / N42 - magnetic separator

Pros and cons of rare earth magnets.

Apart from their superior magnetism, neodymium magnets have these key benefits:

• Their power remains stable, and after around ten years it decreases only by ~1% (theoretically),
• Magnets perfectly defend themselves against demagnetization caused by ambient magnetic noise,
• By covering with a decorative coating of nickel, the element has an nice look,
• Neodymium magnets achieve maximum magnetic induction on a small surface, which allows for strong attraction,
• Through (appropriate) combination of ingredients, they can achieve high thermal resistance, allowing for operation at temperatures approaching 230°C and above...
• Possibility of custom shaping as well as modifying to specific conditions,
• Key role in modern industrial fields – they are commonly used in mass storage devices, brushless drives, precision medical tools, as well as modern systems.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They are prone to damage upon too strong impacts. To avoid cracks, it is worth protecting magnets in special housings. Such protection not only shields the magnet but also improves its resistance to damage
• Neodymium magnets lose force 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 very 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 those in rubber or plastics, which secure oxidation and corrosion.
• Limited possibility of making threads in the magnet and complicated shapes - preferred is casing - magnetic holder.
• Potential hazard to health – tiny shards of magnets are risky, if swallowed, which becomes key in the context of child safety. Furthermore, small elements of these products are able to be problematic in diagnostics medical in case of swallowing.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which can limit application in large quantities

Optimal lifting capacity of a neodymium magnet – what it depends on?

Information about lifting capacity is the result of a measurement for the most favorable conditions, including:

• on a block made of structural steel, optimally conducting the magnetic flux
• whose thickness equals approx. 10 mm
• with a plane free of scratches
• without any air gap between the magnet and steel
• under axial force direction (90-degree angle)
• in stable room temperature

Determinants of lifting force in real conditions

In practice, the real power depends on a number of factors, listed from the most important:

• Gap between surfaces – every millimeter of separation (caused e.g. by varnish or unevenness) drastically reduces the pulling force, often by half at just 0.5 mm.
• Load vector – maximum parameter is reached only during pulling at a 90° angle. The force required to slide of the magnet along the plate is typically many times smaller (approx. 1/5 of the lifting capacity).
• Base massiveness – insufficiently thick sheet does not accept the full field, causing part of the power to be escaped to the other side.
• Steel grade – ideal substrate is pure iron steel. Cast iron may attract less.
• Smoothness – ideal contact is possible only on smooth steel. Rough texture reduce the real contact area, weakening the magnet.
• Temperature – heating the magnet results in weakening of induction. Check the thermal limit for a given model.

* Lifting capacity was determined using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under vertically applied force, in contrast under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet and the plate reduces the holding force.