SMZR 25x175 / N52 - magnetic separator with handle

Strengths and weaknesses of neodymium magnets.

Besides their immense pulling force, neodymium magnets offer the following advantages:

• They virtually do not lose strength, because even after ten years the decline in efficiency is only ~1% (in laboratory conditions),
• Neodymium magnets remain remarkably resistant to magnetic field loss caused by magnetic disturbances,
• The use of an aesthetic finish of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Magnets are characterized by maximum magnetic induction on the outer layer,
• Through (adequate) combination of ingredients, they can achieve high thermal strength, enabling operation at temperatures approaching 230°C and above...
• Thanks to the possibility of flexible shaping and adaptation to custom requirements, magnetic components can be produced in a wide range of geometric configurations, which increases their versatility,
• Fundamental importance in future technologies – they are utilized in mass storage devices, motor assemblies, diagnostic systems, and modern systems.
• Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which allows their use in miniature devices

Disadvantages of NdFeB magnets:

• Brittleness is one of their disadvantages. Upon strong impact they can fracture. We recommend keeping them in a steel housing, which not only protects them against impacts but also increases their durability
• Neodymium magnets lose their force under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• When exposed to humidity, magnets usually rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• We recommend a housing - magnetic holder, due to difficulties in producing threads inside the magnet and complex shapes.
• Health risk related to microscopic parts of magnets pose a threat, if swallowed, which gains importance in the context of child safety. Furthermore, small elements of these magnets can disrupt the diagnostic process medical after entering the body.
• With large orders the cost of neodymium magnets is a challenge,

Maximum magnetic pulling force – what affects it?

Magnet power was determined for optimal configuration, including:

• using a sheet made of high-permeability steel, serving as a circuit closing element
• with a thickness no less than 10 mm
• with an polished touching surface
• under conditions of ideal adhesion (metal-to-metal)
• during detachment in a direction perpendicular to the mounting surface
• at ambient temperature approx. 20 degrees Celsius

Determinants of practical lifting force of a magnet

It is worth knowing that the working load will differ influenced by elements below, starting with the most relevant:

• Gap between magnet and steel – even a fraction of a millimeter of separation (caused e.g. by veneer or unevenness) significantly weakens the magnet efficiency, often by half at just 0.5 mm.
• Force direction – note that the magnet holds strongest perpendicularly. Under sliding down, the capacity drops drastically, often to levels of 20-30% of the nominal value.
• Substrate thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet limits the attraction force (the magnet "punches through" it).
• Plate material – mild steel attracts best. Alloy steels decrease magnetic properties and holding force.
• Surface finish – ideal contact is obtained only on smooth steel. Rough texture create air cushions, reducing force.
• Temperature influence – high temperature weakens pulling force. 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, whereas under shearing force the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet and the plate decreases the holding force.