SM 18x200 [2xM5] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

Apart from their notable power, neodymium magnets have these key benefits:

• They have constant strength, and over around 10 years their attraction force decreases symbolically – ~1% (in testing),
• They do not lose their magnetic properties even under external field action,
• In other words, due to the aesthetic layer of silver, the element gains visual value,
• Neodymium magnets achieve maximum magnetic induction on a small area, which allows for strong attraction,
• Through (adequate) combination of ingredients, they can achieve high thermal strength, enabling operation at temperatures approaching 230°C and above...
• Possibility of individual machining as well as optimizing to defined applications,
• Fundamental importance in future technologies – they are used in data components, brushless drives, medical devices, and multitasking production systems.
• Thanks to their power density, small magnets offer high operating force, occupying minimum space,

What to avoid - cons of neodymium magnets: weaknesses and usage proposals

• At 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.
• Neodymium magnets lose 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
• They rust in a humid environment - during use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• Due to limitations in producing threads and complicated shapes in magnets, we recommend using a housing - magnetic mechanism.
• Potential hazard resulting from small fragments of magnets are risky, in case of ingestion, which becomes key in the context of child safety. Furthermore, tiny parts of these magnets are able to be problematic in diagnostics medical after entering the body.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum magnetic pulling force – what affects it?

Breakaway force was determined for the most favorable conditions, including:

• on a plate made of mild steel, optimally conducting the magnetic field
• with a thickness of at least 10 mm
• characterized by smoothness
• without the slightest insulating layer between the magnet and steel
• under axial force vector (90-degree angle)
• in temp. approx. 20°C

Determinants of lifting force in real conditions

Effective lifting capacity is affected by working environment parameters, mainly (from most important):

• Clearance – the presence of any layer (paint, tape, gap) interrupts the magnetic circuit, which reduces capacity steeply (even by 50% at 0.5 mm).
• Force direction – note that the magnet has greatest strength perpendicularly. Under sliding down, the capacity drops drastically, 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 passes through the material instead of converting into lifting capacity.
• Material composition – different alloys reacts the same. High carbon content worsen the attraction effect.
• Surface finish – full contact is possible only on polished steel. Rough texture reduce the real contact area, weakening the magnet.
• Thermal conditions – NdFeB sinters have a sensitivity to temperature. At higher temperatures they lose power, and in frost they can be stronger (up to a certain limit).

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the load capacity is reduced by as much as 75%. Additionally, even a minimal clearance {between} the magnet and the plate decreases the holding force.