SM 18x150 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets.

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

• They retain full power for around ten years – the drop is just ~1% (according to analyses),
• Magnets very well resist against loss of magnetization caused by foreign field sources,
• Thanks to the shiny finish, the plating of nickel, gold-plated, or silver-plated gives an modern appearance,
• Magnets possess maximum magnetic induction on the outer side,
• Through (appropriate) combination of ingredients, they can achieve high thermal resistance, allowing for operation at temperatures approaching 230°C and above...
• Thanks to versatility in forming and the ability to customize to complex applications,
• Key role in future technologies – they find application in HDD drives, motor assemblies, advanced medical instruments, and multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in tiny dimensions, which makes them useful in miniature devices

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can break. We recommend keeping them in a steel housing, which not only secures them against impacts but also increases their durability
• Neodymium magnets lose power when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (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 very resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• Limited possibility of creating threads in the magnet and complicated shapes - preferred is cover - magnetic holder.
• Possible danger to health – tiny shards of magnets can be dangerous, if swallowed, which becomes key in the context of child safety. Additionally, small elements of these devices can be problematic in diagnostics medical in case of swallowing.
• With budget limitations the cost of neodymium magnets is a challenge,

Detachment force of the magnet in optimal conditions – what it depends on?

Breakaway force is the result of a measurement for optimal configuration, including:

• with the use of a yoke made of low-carbon steel, guaranteeing full magnetic saturation
• with a thickness no less than 10 mm
• characterized by lack of roughness
• with direct contact (without paint)
• for force acting at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Determinants of practical lifting force of a magnet

In real-world applications, the actual holding force depends on several key aspects, ranked from crucial:

• Distance – existence of foreign body (paint, tape, air) acts as an insulator, which lowers capacity steeply (even by 50% at 0.5 mm).
• Loading method – declared lifting capacity refers to pulling vertically. When applying parallel force, the magnet holds significantly lower power (often approx. 20-30% of maximum force).
• Metal thickness – the thinner the sheet, the weaker the hold. Part of the magnetic field penetrates through instead of converting into lifting capacity.
• Steel type – low-carbon steel attracts best. Alloy steels lower magnetic permeability and holding force.
• Surface quality – the more even the surface, the better the adhesion and higher the lifting capacity. Unevenness acts like micro-gaps.
• Temperature influence – hot environment weakens pulling force. Exceeding the limit temperature can permanently demagnetize the magnet.

* Lifting capacity testing was carried out on a smooth plate of suitable thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the load capacity is reduced by as much as 75%. In addition, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.