The attractive force of magnets and magnetic attraction devices
For magnetic applications, everyone is very concerned about the magnetic attraction of magnets. The suction force of a magnet can be calculated (using a tension calculator), and the following formula can be used as a reference. However, it should be noted that the default conditions of the formula are very ideal, that is, the magnetic field distribution is very uniform, the magnetic permeability of the object being attracted is very high (weak magnetic materials such as 300 series stainless steel and other ferroalloys cannot be used), and the thickness and adsorption area are sufficient (increasing the thickness and area will not further increase the suction force, that is, without considering magnetic leakage). Even so, the calculated value can only be used as a reference and cannot be used for accurate calculation. F (N)=2 * S (m ²) * B (T) ²/μ 0, where S represents the adsorption area, B represents the air gap magnetic flux density, and μ 0 is the vacuum magnetic permeability (which is a constant, μ 0=4 π * 10-7).
How to increase the attraction of magnets? From the formula, we can see that the suction force of a magnet is directly proportional to the adsorption area and air gap magnetic flux density. It can be seen that increasing the adsorption area and improving the air gap magnetic flux density are the two main ways to increase the suction force of a magnet. 1. Increasing the adsorption area should at least cover the magnetic adsorption surface, and if conditions permit, the thickness of the adsorbed material can be increased.
When a magnet is attracted to an iron plate: the larger the adsorption area between the iron plate and the magnet, the greater the suction force between the magnets. When the adsorption area is equal to the area of the magnet, the trend of increasing suction force will gradually slow down. When the iron plate is large enough, increasing the area of the iron plate may not further increase the suction force; When the area of the iron plate is the same, increasing the thickness of the iron plate can enhance the suction force. When the iron plate is thicker, increasing the thickness of the iron plate will gradually flatten the increase in suction force until there is no further improvement.
2. Increasing the air gap magnetic flux density. When the adsorption area S remains constant, finding a way to increase the air gap magnetic flux density and reduce leakage magnetic flux is a more effective way to improve suction force. Multi pole magnetization can effectively reduce leakage magnetic flux.
From the magnetic field simulation diagram, we can see that after changing the magnet to bipolar magnetization, the leakage magnetic field is significantly reduced, and a large part of the magnetic field lines form a magnetic circuit loop inside the adsorbed iron sheet.
If the number of poles is further increased and a magnetic plate is added at the bottom of the magnet, the leakage magnetic flux will be further reduced and the suction force will be further increased.
The current trend in the design of magnetic components is to maximize the utilization of magnetic fields by designing multipole magnetic circuits or Halbeck magnetic circuits, or using materials with high magnetic permeability to guide the magnetic field as much as possible through the object being attracted, forming a magnetic circuit loop. Typical applications include: rubber magnetic sheets, designed for multi-stage magnetization, some with double-sided multipoles and some with single-sided multipoles. The magnetic performance of rubber magnets is very low, but through multipole magnetic circuit design, the magnetic field is densely distributed on the surface, resulting in minimal magnetic leakage during adsorption and producing good adsorption effect;
The design of magnetic attraction components cannot be separated from the consideration of adsorption spacing. The above mentioned are all based on direct contact adsorption. If the spacing changes, the suction force often changes greatly. The following figure shows several typical single magnet magnetic attraction devices, and multipole magnetic components follow a similar rule. The more poles there are, the greater the suction force at 0 spacing, but the more obvious the attenuation with increasing spacing.