SM 32x200 [2xM8] / N42 - magnetic separator

Strengths and weaknesses of rare earth magnets.

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

• They have unchanged lifting capacity, and over more than 10 years their attraction force decreases symbolically – ~1% (according to theory),
• Magnets perfectly defend themselves against demagnetization caused by external fields,
• A magnet with a smooth silver surface has better aesthetics,
• Neodymium magnets generate maximum magnetic induction on a contact point, which increases force concentration,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Possibility of exact machining as well as optimizing to specific applications,
• Fundamental importance in innovative solutions – they are utilized in HDD drives, electric drive systems, medical devices, also other advanced devices.
• Thanks to efficiency per cm³, small magnets offer high operating force, occupying minimum space,

Disadvantages of neodymium magnets:

• At strong impacts they can break, therefore we advise placing them in strong housings. A metal housing provides additional protection against damage and increases the magnet's durability.
• We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we recommend our specialized [AH] magnets, which work effectively even at 230°C.
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• We suggest casing - magnetic mechanism, due to difficulties in creating threads inside the magnet and complex shapes.
• Possible danger to health – tiny shards of magnets can be dangerous, when accidentally swallowed, which is particularly important in the aspect of protecting the youngest. It is also worth noting that tiny parts of these products can be problematic in diagnostics medical in case of swallowing.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which hinders application in large quantities

Maximum lifting capacity of the magnet – what it depends on?

The force parameter is a result of laboratory testing executed under standard conditions:

• on a block made of mild steel, optimally conducting the magnetic flux
• with a thickness of at least 10 mm
• with an ground contact surface
• without any air gap between the magnet and steel
• during pulling in a direction vertical to the plane
• at ambient temperature approx. 20 degrees Celsius

Practical lifting capacity: influencing factors

Bear in mind that the magnet holding will differ depending on elements below, starting with the most relevant:

• Air gap (between the magnet and the plate), because even a tiny distance (e.g. 0.5 mm) leads to a drastic drop in force by up to 50% (this also applies to paint, corrosion or debris).
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under sliding down, the capacity drops significantly, often to levels of 20-30% of the nominal value.
• Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux passes through the material instead of converting into lifting capacity.
• Plate material – mild steel gives the best results. Higher carbon content lower magnetic properties and lifting capacity.
• Smoothness – full contact is obtained only on smooth steel. Rough texture reduce the real contact area, reducing force.
• Operating temperature – neodymium magnets have a sensitivity to temperature. At higher temperatures they are weaker, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under perpendicular forces, in contrast under shearing force the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate reduces the load capacity.