SM 25x225 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of rare earth magnets.

Besides their immense field intensity, neodymium magnets offer the following advantages:

• They have constant strength, and over around 10 years their performance decreases symbolically – ~1% (according to theory),
• Magnets perfectly protect themselves against loss of magnetization caused by foreign field sources,
• A magnet with a smooth nickel surface has better aesthetics,
• They are known for high magnetic induction at the operating surface, which affects their effectiveness,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can work (depending on the form) even at a temperature of 230°C or more...
• Thanks to freedom in shaping and the capacity to customize to client solutions,
• Huge importance in high-tech industry – they are utilized in magnetic memories, electric motors, medical devices, as well as modern systems.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• At strong impacts they can break, therefore we recommend placing them in special holders. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material immune to moisture, when using outdoors
• Limited possibility of making nuts in the magnet and complicated forms - preferred is cover - mounting mechanism.
• Possible danger related to microscopic parts of magnets can be dangerous, if swallowed, which gains importance in the context of child health protection. Additionally, tiny parts of these devices can complicate diagnosis medical when they are in the body.
• Due to complex production process, their price is relatively high,

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

The force parameter is a theoretical maximum value conducted under the following configuration:

• on a plate made of mild steel, effectively closing the magnetic field
• with a cross-section no less than 10 mm
• with an ground contact surface
• with direct contact (no paint)
• for force acting at a right angle (pull-off, not shear)
• in neutral thermal conditions

Determinants of practical lifting force of a magnet

In real-world applications, the actual lifting capacity is determined by many variables, listed from most significant:

• Air gap (between the magnet and the metal), since even a microscopic distance (e.g. 0.5 mm) leads to a drastic drop in force by up to 50% (this also applies to paint, corrosion or dirt).
• Force direction – note that the magnet has greatest strength perpendicularly. Under sliding down, the capacity drops significantly, often to levels of 20-30% of the nominal value.
• Steel thickness – insufficiently thick sheet does not accept the full field, causing part of the power to be escaped to the other side.
• Steel type – low-carbon steel gives the best results. Higher carbon content reduce magnetic properties and holding force.
• Surface quality – the smoother and more polished the plate, the better the adhesion and higher the lifting capacity. Roughness acts like micro-gaps.
• 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).

* Lifting capacity was measured using a steel plate with a smooth surface of suitable thickness (min. 20 mm), under vertically applied force, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 5 times. In addition, even a slight gap {between} the magnet and the plate lowers the load capacity.