SM 18x275 [2xM5] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets.

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

• They have constant strength, and over around 10 years their attraction force decreases symbolically – ~1% (according to theory),
• Magnets effectively defend themselves against demagnetization caused by ambient magnetic noise,
• A magnet with a metallic gold surface has better aesthetics,
• Neodymium magnets create maximum magnetic induction on a small surface, which allows for strong attraction,
• Through (adequate) combination of ingredients, they can achieve high thermal strength, enabling action at temperatures approaching 230°C and above...
• Thanks to versatility in forming and the ability to customize to unusual requirements,
• Fundamental importance in high-tech industry – they are utilized in computer drives, electromotive mechanisms, precision medical tools, also technologically advanced constructions.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Cons of neodymium magnets: application proposals

• Brittleness is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a special holder, which not only secures them against impacts but also increases their durability
• Neodymium magnets lose their force under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• They oxidize in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited possibility of making threads in the magnet and complex forms - preferred is a housing - mounting mechanism.
• Possible danger to health – tiny shards of magnets are risky, in case of ingestion, which becomes key in the context of child health protection. Furthermore, small elements of these devices can disrupt the diagnostic process medical after entering the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which hinders application in large quantities

Maximum magnetic pulling force – what affects it?

The lifting capacity listed is a measurement result executed under standard conditions:

• on a block made of structural steel, perfectly concentrating the magnetic field
• whose transverse dimension reaches at least 10 mm
• with a surface cleaned and smooth
• with direct contact (no impurities)
• during detachment in a direction vertical to the mounting surface
• at room temperature

Practical aspects of lifting capacity – factors

Real force impacted by specific conditions, mainly (from most important):

• Distance – the presence of any layer (paint, dirt, gap) acts as an insulator, which reduces power steeply (even by 50% at 0.5 mm).
• Pull-off angle – note that the magnet holds strongest perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the maximum value.
• Wall thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of converting into lifting capacity.
• Material composition – not every steel reacts the same. High carbon content weaken the attraction effect.
• Plate texture – smooth surfaces guarantee perfect abutment, which improves field saturation. Rough surfaces weaken the grip.
• Thermal factor – hot environment weakens pulling force. Too high temperature can permanently demagnetize the magnet.

* Lifting capacity testing was performed on plates with a smooth surface of suitable thickness, under perpendicular forces, in contrast under shearing force the holding force is lower. In addition, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.