The magnitude of the magnet's suction force 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 force.
How do we determine whether the working point of the magnet is at the maximum magnetic energy product point? 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 the maximum magnetic energy product, the suction force is the largest. This also aligns with the rule that magnets are usually designed as relatively flat shapes as adsorption parts. Taking the N35 D10*6 magnet as an example, through FEA simulation, it can be calculated that the suction force of the adsorption iron plate is about 27N, which almost reaches the maximum value of magnets of the same volume, which is 780 times its weight.
Square magnets are similar to circular magnets. When directly adsorbed to the material being adsorbed, the center Pc≈1, that is, it is near the maximum magnetic energy product working point, and the suction force will reach the maximum value of the same volume magnet, such as 10*10*6.5 or 15*10*8.
Why does the suction force of a magnet of the same volume change so much after being made into multi-pole magnetization? The reason is that the adsorption area S remains unchanged, while the magnetic flux density B value through the adsorbed object increases a lot. The magnetic line diagram below shows that the density of magnetic lines passing through the iron sheet of a multi-pole magnetized magnet is significantly increased. Taking the N35 D10*6 magnet as an example, it is made into a bipolar magnetization. The suction force of the FEA simulation adsorption iron plate is about 1100 times its weight.
After the magnet is made into a multi-pole magnet, each pole is equivalent to a thinner magnet, and its Pc value has changed. It can no longer be calculated according to the Pc value of the overall size. Therefore, its optimal size is no longer H/D≈0.6, but a flatter magnet. The specific size is related to the multi-pole magnetization method and the number of poles.