SM 32x225 [2xM8] / N42 - magnetic separator

Pros and cons of rare earth magnets.

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

• Their magnetic field is maintained, and after approximately ten years it drops only by ~1% (according to research),
• They do not lose their magnetic properties even under strong external field,
• The use of an aesthetic layer of noble metals (nickel, gold, silver) causes the element to look better,
• Magnetic induction on the top side of the magnet turns out to be exceptional,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Possibility of individual modeling as well as modifying to atypical needs,
• Huge importance in future technologies – they are commonly used in HDD drives, electromotive mechanisms, medical equipment, as well as other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which enables their usage in small systems

Disadvantages of NdFeB magnets:

• At very strong impacts they can break, therefore we recommend placing them in special holders. A metal housing provides additional protection against damage and increases the magnet's durability.
• We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
• 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 prevent oxidation as well as corrosion.
• Due to limitations in realizing nuts and complex forms in magnets, we propose using cover - magnetic mechanism.
• Possible danger resulting from small fragments of magnets can be dangerous, in case of ingestion, which gains importance in the aspect of protecting the youngest. Additionally, small elements of these magnets are able to be problematic in diagnostics medical when they are in the body.
• With mass production the cost of neodymium magnets is economically unviable,

Magnetic strength at its maximum – what affects it?

Breakaway force was determined for optimal configuration, assuming:

• on a block made of structural steel, perfectly concentrating the magnetic field
• possessing a thickness of min. 10 mm to avoid saturation
• with a plane free of scratches
• without the slightest insulating layer between the magnet and steel
• for force acting at a right angle (in the magnet axis)
• at conditions approx. 20°C

Impact of factors on magnetic holding capacity in practice

It is worth knowing that the application force may be lower depending on elements below, in order of importance:

• Distance – the presence of foreign body (paint, dirt, air) interrupts the magnetic circuit, which reduces power rapidly (even by 50% at 0.5 mm).
• Angle of force application – highest force is reached only during perpendicular pulling. The force required to slide of the magnet along the plate is usually many times smaller (approx. 1/5 of the lifting capacity).
• Steel thickness – insufficiently thick sheet does not close the flux, causing part of the flux to be escaped to the other side.
• Material type – ideal substrate is high-permeability steel. Cast iron may attract less.
• Surface finish – full contact is possible only on polished steel. Rough texture create air cushions, weakening the magnet.
• Thermal conditions – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and in frost gain strength (up to a certain limit).

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the holding force is lower. In addition, even a slight gap {between} the magnet and the plate lowers the holding force.