MW 40x8 / N38 - cylindrical magnet

Strengths as well as weaknesses of rare earth magnets.

Besides their remarkable field intensity, neodymium magnets offer 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 noted for resistance to demagnetization induced by external disturbances,
• Thanks to the elegant finish, the layer of Ni-Cu-Ni, gold, or silver-plated gives an elegant appearance,
• Magnetic induction on the top side of the magnet turns out to be maximum,
• Thanks to resistance to high temperature, they are able to function (depending on the shape) even at temperatures up to 230°C and higher...
• Considering the potential of flexible shaping and customization to individualized requirements, magnetic components can be created in a variety of forms and dimensions, which increases their versatility,
• Huge importance in high-tech industry – they are utilized in hard drives, brushless drives, precision medical tools, and modern systems.
• Thanks to their power density, small magnets offer high operating force, in miniature format,

Cons of neodymium magnets: weaknesses and usage proposals

• At strong impacts they can break, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage and increases the magnet's durability.
• Neodymium magnets decrease their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. 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. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• Limited ability of making threads in the magnet and complicated forms - recommended is cover - magnetic holder.
• Health risk resulting from small fragments of magnets are risky, if swallowed, which is particularly important in the context of child safety. It is also worth noting that small components of these products are able to disrupt the diagnostic process medical after entering the body.
• With large orders the cost of neodymium magnets can be a barrier,

Maximum holding power of the magnet – what affects it?

The load parameter shown represents the limit force, measured under optimal environment, namely:

• using a sheet made of high-permeability steel, serving as a magnetic yoke
• whose transverse dimension is min. 10 mm
• with a plane free of scratches
• with zero gap (no coatings)
• for force acting at a right angle (in the magnet axis)
• at temperature approx. 20 degrees Celsius

What influences lifting capacity in practice

During everyday use, the actual holding force depends on a number of factors, listed from the most important:

• Distance (between the magnet and the metal), as even a very small distance (e.g. 0.5 mm) results in a reduction in force by up to 50% (this also applies to varnish, rust or dirt).
• Direction of force – highest force is reached only during perpendicular pulling. The shear force of the magnet along the plate is usually many times lower (approx. 1/5 of the lifting capacity).
• Steel thickness – too thin steel causes magnetic saturation, causing part of the flux to be escaped to the other side.
• Chemical composition of the base – mild steel attracts best. Alloy admixtures lower magnetic properties and holding force.
• Surface condition – smooth surfaces guarantee perfect abutment, which improves field saturation. Rough surfaces weaken the grip.
• Temperature influence – hot environment reduces magnetic field. Too high temperature can permanently damage the magnet.

* Lifting capacity was assessed by applying a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, in contrast under parallel forces the holding force is lower. In addition, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.