SM 32x500 [2xM8] / N42 - magnetic separator

Pros and cons of rare earth magnets.

Besides their durability, neodymium magnets are valued for these benefits:

• They do not lose magnetism, even after approximately 10 years – the decrease in power is only ~1% (theoretically),
• Magnets effectively protect themselves against loss of magnetization caused by foreign field sources,
• A magnet with a shiny nickel surface has an effective appearance,
• Magnetic induction on the working part of the magnet remains extremely intense,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their form) at temperatures up to 230°C and above...
• Possibility of custom machining as well as adjusting to atypical needs,
• Significant place in advanced technology sectors – they find application in data components, electric drive systems, precision medical tools, and modern systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in small dimensions, which allows their use in compact constructions

Drawbacks and weaknesses of neodymium magnets and proposals for their use:

• Brittleness is one of their disadvantages. Upon intense impact they can break. We advise keeping them in a strong case, which not only secures them against impacts but also raises their durability
• Neodymium magnets decrease their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which prevent oxidation as well as corrosion.
• Limited possibility of creating nuts in the magnet and complex shapes - preferred is cover - magnet mounting.
• Health risk related to microscopic parts of magnets pose a threat, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. Furthermore, tiny parts of these devices are able to disrupt the diagnostic process medical in case of swallowing.
• Due to neodymium price, their price is higher than average,

Maximum lifting force for a neodymium magnet – what affects it?

Holding force of 0 kg is a theoretical maximum value conducted under the following configuration:

• with the contact of a yoke made of special test steel, guaranteeing full magnetic saturation
• possessing a massiveness of min. 10 mm to ensure full flux closure
• with an ground contact surface
• under conditions of ideal adhesion (metal-to-metal)
• during detachment in a direction perpendicular to the plane
• in neutral thermal conditions

What influences lifting capacity in practice

Real force is influenced by working environment parameters, such as (from priority):

• Distance – the presence of foreign body (rust, tape, air) acts as an insulator, which reduces capacity rapidly (even by 50% at 0.5 mm).
• Load vector – maximum parameter is obtained only during perpendicular pulling. The force required to slide of the magnet along the plate is usually many times lower (approx. 1/5 of the lifting capacity).
• Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal restricts the lifting capacity (the magnet "punches through" it).
• Metal type – not every steel attracts identically. High carbon content weaken the attraction effect.
• Surface structure – the more even the plate, the larger the contact zone and stronger the hold. Roughness creates an air distance.
• Thermal conditions – NdFeB sinters have a sensitivity to temperature. At higher temperatures they lose power, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity testing was performed on a smooth plate of optimal thickness, under a perpendicular pulling force, however under attempts to slide the magnet the holding force is lower. Additionally, even a slight gap {between} the magnet and the plate reduces the holding force.