UMH 20x7x35 [M4] / N38 - magnetic holder with hook

Advantages as well as disadvantages of rare earth magnets.

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

• They virtually do not lose power, because even after ten years the performance loss is only ~1% (based on calculations),
• They are extremely resistant to demagnetization induced by external field influence,
• Thanks to the shimmering finish, the layer of Ni-Cu-Ni, gold-plated, or silver-plated gives an aesthetic appearance,
• Neodymium magnets create maximum magnetic induction on a small area, which allows for strong attraction,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to versatility in constructing and the capacity to adapt to unusual requirements,
• Fundamental importance in electronics industry – they find application in magnetic memories, brushless drives, medical equipment, also multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in small dimensions, which makes them useful in small systems

What to avoid - cons of neodymium magnets: application proposals

• To avoid cracks under impact, we recommend using special steel housings. Such a solution protects the magnet and simultaneously increases its durability.
• Neodymium magnets decrease their power 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
• Magnets exposed to a humid environment can rust. Therefore while using outdoors, we advise using waterproof magnets made of rubber, plastic or other material protecting against moisture
• Limited ability of producing threads in the magnet and complex shapes - preferred is casing - magnetic holder.
• Potential hazard resulting from small fragments of magnets can be dangerous, in case of ingestion, which gains importance in the context of child safety. Additionally, small elements of these devices can be problematic in diagnostics medical when they are in the body.
• Due to expensive raw materials, their price exceeds standard values,

Maximum lifting force for a neodymium magnet – what it depends on?

Information about lifting capacity was defined for optimal configuration, assuming:

• using a base made of mild steel, serving as a circuit closing element
• with a cross-section of at least 10 mm
• with a surface free of scratches
• with zero gap (no coatings)
• for force applied at a right angle (in the magnet axis)
• at temperature approx. 20 degrees Celsius

Impact of factors on magnetic holding capacity in practice

During everyday use, the real power is determined by several key aspects, presented from crucial:

• Gap between surfaces – every millimeter of distance (caused e.g. by veneer or unevenness) diminishes the pulling force, often by half at just 0.5 mm.
• Pull-off angle – remember that the magnet holds strongest perpendicularly. Under sliding down, the capacity drops drastically, often to levels of 20-30% of the nominal value.
• Wall thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of converting into lifting capacity.
• Material composition – different alloys reacts the same. Alloy additives worsen the interaction with the magnet.
• Surface structure – the smoother and more polished the surface, the better the adhesion and stronger the hold. Unevenness acts like micro-gaps.
• Operating temperature – neodymium magnets have a negative temperature coefficient. At higher temperatures they lose power, and in frost gain strength (up to a certain limit).

* Holding force was tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under shearing force the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the lifting capacity.