magnetic field strength

Many customers may have a question: do magnets of the same performance and volume have the same suction force? It is said on the Internet that the suction force of NdFeB magnets is 640 times its own weight. Is this credible?   First of all, it should be made clear that magnets only have adsorption force on ferromagnetic materials. At room temperature, there are only three types of ferromagnetic materials, they're iron, cobalt, nickel, and their alloys. They have no adsorption force on non-ferromagnetic materials.   There are also many formulas on the Internet for calculating suction. The results of these formulas may not be accurate, but the trend is correct. The strength of the magnetic suction is related to the magnetic field strength and the adsorption area. The greater the magnetic field strength, the larger the adsorption area and the greater the suction.   The next question is, if the magnets are flat, cylindrical, or elongated, will they have the same suction force? If not, which one has the greatest suction force?       First of all, it is certain that the suction force is not the same. To determine which suction force is the greatest, we need to refer to the definition of the maximum magnetic energy product. When the working point of the magnet is near the maximum magnetic energy product, the magnet has the greatest work energy. The adsorption force of the magnet is also a manifestation of work, so the corresponding suction force is also the greatest. It should be noted here that the object to be sucked needs to be large enough to completely cover the size of the magnetic pole so that the material, size, shape, and other factors of the object to be sucked can be ignored.   How to judge whether the working point of the magnet is at the point of maximum magnetic energy product? When the magnet is in a state of direct adsorption with the material being adsorbed, its adsorption force is determined by the size of the air gap magnetic field and the adsorption area.    Taking a cylindrical magnet as an example, when H/D≈0.6, its center Pc≈1, and when it is near the working point of maximum magnetic energy product, the suction force is the largest. This is also in line with the rule that magnets are usually designed to be relatively flat as adsorbents. Taking the N35 D10*6mm magnet as an example, through FEA simulation, it can be calculated that the suction force of the adsorbed iron plate is about 27N, which almost reaches the maximum value of magnets of the same volume and is 780 times its own weight.   The above is only the adsorption state of a single pole of the magnet. If it is multi-pole magnetization, the suction force will be completely different. The suction force of multi-pole magnetization will be much greater than that of single-pole magnetization (under the premise of a small distance from the adsorbed object).     Why does the suction force of a magnet of the same volume change so much after being magnetized with multiple poles? The reason is that the adsorption area S remains unchanged, while the magnetic flux density B value through the adsorbed object increases a lot. From the magnetic force line diagram below, it can be seen that the density of magnetic force lines passing through the iron sheet of a multi-pole magnetized magnet is significantly increased. Taking the N35 D10*6mm magnet as an example, it is made into a bipolar magnetization. The suction force of the FEA simulation adsorbing the iron plate is about 1100 times its own weight.     Since the magnet is made into a multi-pole magnet, each pole is equivalent to a thinner and longer magnet. The specific size is related to the multi-pole magnetization method and the number of poles.