SMZR 25x175 / N52 - magnetic separator with handle

Strengths as well as weaknesses of rare earth magnets.

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

• Their strength remains stable, and after approximately ten years it decreases only by ~1% (according to research),
• Neodymium magnets remain remarkably resistant to demagnetization caused by external field sources,
• The use of an elegant coating of noble metals (nickel, gold, silver) causes the element to have aesthetics,
• Magnets exhibit impressive magnetic induction on the working surface,
• Thanks to resistance to high temperature, they can operate (depending on the form) even at temperatures up to 230°C and higher...
• Thanks to modularity in constructing and the ability to customize to complex applications,
• Significant place in modern industrial fields – they are utilized in magnetic memories, drive modules, medical devices, and industrial machines.
• Thanks to efficiency per cm³, small magnets offer high operating force, with minimal size,

Disadvantages of NdFeB magnets:

• They are fragile upon too strong impacts. To avoid cracks, it is worth protecting magnets using a steel holder. Such protection not only protects the magnet but also increases its resistance to damage
• When exposed to high temperature, neodymium magnets experience a drop in force. Often, when the temperature exceeds 80°C, their power decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• Magnets exposed to a humid environment can corrode. Therefore during using outdoors, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture
• We recommend cover - magnetic mechanism, due to difficulties in producing threads inside the magnet and complicated forms.
• Potential hazard resulting from small fragments of magnets can be dangerous, if swallowed, which becomes key in the context of child safety. Furthermore, small elements of these products are able to disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which can limit application in large quantities

Magnetic strength at its maximum – what it depends on?

Magnet power is the result of a measurement for the most favorable conditions, assuming:

• using a plate made of mild steel, functioning as a circuit closing element
• possessing a thickness of at least 10 mm to avoid saturation
• with a plane perfectly flat
• with direct contact (without impurities)
• under vertical 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, including (from priority):

• Gap between surfaces – every millimeter of separation (caused e.g. by veneer or unevenness) diminishes the pulling force, often by half at just 0.5 mm.
• Load vector – highest force is reached only during pulling at a 90° angle. The shear force of the magnet along the surface is typically many times lower (approx. 1/5 of the lifting capacity).
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Steel grade – the best choice is high-permeability steel. Cast iron may attract less.
• Surface condition – ground elements ensure maximum contact, which increases force. Rough surfaces reduce efficiency.
• Thermal environment – heating the magnet results in weakening of force. Check the maximum operating temperature for a given model.

* Lifting capacity testing was performed on a smooth plate of optimal thickness, under perpendicular forces, however under attempts to slide the magnet the load capacity is reduced by as much as 75%. In addition, even a small distance {between} the magnet’s surface and the plate lowers the holding force.