Can NdFeB Absorb Objects 600 Times Its Own Weight? Not Exactly

Magnets can pick up heavy objects. It is said on the Internet that NdFeB magnets can pick up objects 600 times their own weight. Is this accurate? Is there a formula for calculating magnet attraction? Today, I will tell you about the “attractive force” of magnets.

In the application of magnets, magnetic flux or magnetic flux density is an important index to measure its performance (especially in motors), but in some application fields, such as magnetic separation, salvage, etc., magnetic flux is not an effective measure of sorting or The amount of adsorption effect, magnetic attraction is a more effective indicator.

NdFeB magnetic attraction value

Magnetic attraction refers to the weight of ferromagnetic substances that a magnet can absorb. It is affected by factors such as the performance, shape, size, and adsorption distance of the magnet. There is no mathematical formula that can calculate the attraction of a magnet, but we can use it The magnetic attraction measuring device is used to measure the magnetic attraction value (usually measuring the pulling force of the magnet and then converting it into weight), as shown in the figure below. The attraction force of the magnet will gradually decrease as the distance of the attracted object increases.

If you search for magnet suction calculations on the Internet, many websites will write “According to experience, the magnetic force of NdFeB magnets is 600 times their own weight (some also write 640 times)”. Is this experience correct? We will verify it through experiments. Just know.

The experiment selected sintered NdFeB N42 magnets of different shapes and sizes. The surface coatings are all nickel-copper-nickel, and they are all magnetized in the height direction. The maximum pulling force (N pole) of each magnet was measured and converted into adsorption weight. The result is as follows:

Magnetic attraction Of disc rod magnet

Magnetic attraction of block magnet

Can NdFeB Absorb Objects 600 Times Its Own Weight? Not Exactly

It is not difficult to find from the measurement results:

The ratio of the weight that can be picked up by magnets of different shapes and sizes to their own weight varies greatly, some are less than 200 times, some are more than 500 times, and some can reach more than 3000 times, so the 600 times written on the Internet is not completely correct

For cylinders or round cakes with the same diameter, the greater the height, the greater the weight that can be absorbed, and the suction is basically proportional to the height

For cylinders or round cakes (blue cells) of the same height, the larger the diameter, the greater the weight that can be sucked up, and the suction is basically proportional to the diameter

Cylinders or round cakes (yellow cells) with the same volume and weight have different diameters and heights, and the weight that can be picked up varies greatly. Generally, the longer the orientation direction of the magnet, the greater the suction force

Magnets with the same volume do not necessarily have the same attraction force. Depending on the shape, the attraction force may vary greatly; the reverse is also the same. Magnets that attract the same weight of ferromagnetic materials may have different shapes, volumes, and weights.

Regardless of the shape, the length of the orientation direction has the greatest effect on determining the suction force
The above is the suction test for the same brand of magnets, so what is the difference in suction between different brands of magnets, we will do a test later for comparison. Can NdFeB Absorb Objects 600 Times Its Own Weight? Not Exactly

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