SMZR 25x150 / N52 - magnetic separator with handle

Strengths as well as weaknesses of rare earth magnets.

Besides their tremendous magnetic power, neodymium magnets offer the following advantages:

• They virtually do not lose strength, because even after 10 years the decline in efficiency is only ~1% (in laboratory conditions),
• Neodymium magnets remain highly resistant to magnetic field loss caused by external interference,
• A magnet with a metallic nickel surface has an effective appearance,
• They feature high magnetic induction at the operating surface, which increases their power,
• Thanks to resistance to high temperature, they are capable of working (depending on the shape) even at temperatures up to 230°C and higher...
• Due to the possibility of accurate forming and adaptation to unique solutions, magnetic components can be produced in a variety of shapes and sizes, which amplifies use scope,
• Universal use in modern technologies – they are commonly used in HDD drives, brushless drives, advanced medical instruments, also multitasking production systems.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Cons of neodymium magnets and proposals for their use:

• At very strong impacts they can break, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage and increases the magnet's durability.
• NdFeB magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (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 extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material immune to moisture, when using outdoors
• Limited possibility of making threads in the magnet and complicated forms - preferred is a housing - magnet mounting.
• Possible danger resulting from small fragments of magnets are risky, if swallowed, which gains importance in the context of child health protection. Furthermore, small components of these products can disrupt the diagnostic process medical when they are in the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Detachment force of the magnet in optimal conditions – what contributes to it?

The lifting capacity listed is a theoretical maximum value performed under standard conditions:

• with the use of a sheet made of low-carbon steel, ensuring full magnetic saturation
• possessing a massiveness of min. 10 mm to ensure full flux closure
• characterized by lack of roughness
• under conditions of ideal adhesion (metal-to-metal)
• for force acting at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

What influences lifting capacity in practice

In real-world applications, the real power results from many variables, listed from most significant:

• Air gap (betwixt the magnet and the plate), because even a microscopic distance (e.g. 0.5 mm) results in a decrease in lifting capacity by up to 50% (this also applies to varnish, rust or dirt).
• Force direction – remember that the magnet holds strongest perpendicularly. Under sliding down, the capacity drops significantly, often to levels of 20-30% of the maximum value.
• Wall thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of generating force.
• Metal type – different alloys reacts the same. Alloy additives worsen the interaction with the magnet.
• Plate texture – ground elements guarantee perfect abutment, which increases field saturation. Uneven metal reduce efficiency.
• Heat – NdFeB sinters have a sensitivity to temperature. When it is hot they lose power, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity was measured using a smooth steel plate of suitable thickness (min. 20 mm), under vertically applied force, whereas under shearing force the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet and the plate reduces the holding force.