SM 25x100 [2xM8] / N42 - magnetic separator

Strengths and weaknesses of neodymium magnets.

In addition to their magnetic capacity, neodymium magnets provide the following advantages:

• They do not lose magnetism, even during nearly ten years – the reduction in lifting capacity is only ~1% (based on measurements),
• Neodymium magnets are highly resistant to loss of magnetic properties caused by external field sources,
• A magnet with a metallic silver surface has better aesthetics,
• The surface of neodymium magnets generates a powerful magnetic field – this is a key feature,
• Through (adequate) combination of ingredients, they can achieve high thermal strength, enabling operation at temperatures approaching 230°C and above...
• Thanks to freedom in constructing and the capacity to adapt to individual projects,
• Universal use in high-tech industry – they are commonly used in HDD drives, electric motors, diagnostic systems, also technologically advanced constructions.
• Compactness – despite small sizes they provide effective action, making them ideal for precision applications

Problematic aspects of neodymium magnets and proposals for their use:

• Brittleness is one of their disadvantages. Upon strong impact they can break. We advise keeping them in a steel housing, which not only protects them against impacts but also increases their durability
• Neodymium magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (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 extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• Due to limitations in producing threads and complicated shapes in magnets, we propose using cover - magnetic holder.
• Potential hazard to health – tiny shards of magnets can be dangerous, when accidentally swallowed, which becomes key in the context of child health protection. It is also worth noting that small elements of these devices are able to be problematic in diagnostics medical in case of swallowing.
• 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?

Information about lifting capacity was determined for the most favorable conditions, taking into account:

• with the application of a sheet made of special test steel, ensuring maximum field concentration
• possessing a thickness of min. 10 mm to ensure full flux closure
• with an ideally smooth touching surface
• under conditions of gap-free contact (metal-to-metal)
• for force applied at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Practical lifting capacity: influencing factors

During everyday use, the actual lifting capacity depends on several key aspects, listed from the most important:

• Distance (betwixt the magnet and the metal), since even a very small clearance (e.g. 0.5 mm) results in a drastic drop in lifting capacity by up to 50% (this also applies to varnish, corrosion or dirt).
• Loading method – catalog parameter refers to pulling vertically. When attempting to slide, the magnet holds much less (typically approx. 20-30% of nominal force).
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal restricts the lifting capacity (the magnet "punches through" it).
• Material composition – not every steel reacts the same. High carbon content weaken the attraction effect.
• Surface finish – full contact is possible only on polished steel. Any scratches and bumps create air cushions, reducing force.
• Temperature influence – high temperature reduces magnetic field. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under shearing force the load capacity is reduced by as much as fivefold. In addition, even a slight gap {between} the magnet and the plate decreases the lifting capacity.