How to increase the suction force of the magnet?
For the application of magnetic attraction, everyone pays great attention to the attraction force of the magnet. The suction force of a magnet can be calculated (pull force calculator), and the following formula can be used for reference, but it should be noted that the default conditions of the formula are very ideal, that is, the magnetic field distribution is very uniform, and the magnetic permeability of the attracted object is very high (weak magnetic materials such as 300 series stainless steel and some other ferroalloys are not applicable), the thickness and adsorption area are sufficient (the suction force will not be improved if the thickness and area are increased, that is, magnetic flux leakage is not considered), even so, the calculated value can only be used as For reference, not for exact calculations.
F(N)=2*S(m²)*B(T)²/μ0
Among them, S represents the adsorption area, B represents the air gap magnetic flux density, and μ0 is the vacuum permeability (a constant, μ0=4π*10-7).
From the formula, we can see that the suction force of a magnet is proportional to the adsorption area and the air gap magnetic flux density. It can be seen that increasing the adsorption area and increasing the air gap magnetic flux density are two ways to increase the suction force of a magnet.
1. Increase the adsorption area
The attracted object should at least be able to cover the magnet adsorption surface, and the thickness of the attracted object can be increased if conditions permit.
When a magnet attracts an iron plate:
The larger the adsorption area between the iron plate and the magnet, the greater the suction force between the magnet and the iron plate. When the adsorption area is equal to the area of the magnet, the tendency of the suction force to become larger will gradually slow down. When the iron plate is large enough, increase the suction force. The area of the iron plate may not improve the suction;
When the area of the iron plate is the same, when the thickness of the iron plate is thinner, increasing the thickness of the iron plate can increase the suction force; when the iron plate is thicker, increasing the thickness of the iron plate will gradually increase the suction force until there is no increase.
2. Increase the air gap flux density
When the adsorption area S is constant, finding ways to increase the air gap flux density and reduce the magnetic flux leakage will be a more effective way to increase the suction force, and the magnetic flux leakage can be effectively reduced by multi-pole magnetization.
From the magnetic field simulation diagram, we can see that after the magnet is changed to bipolar magnetization, the magnetic flux leakage is significantly reduced, and a large part of the magnetic force lines forms a magnetic circuit closed loop inside the adsorbed iron sheet.
If the number of poles is further increased, and a magnetic conductive sheet is added to the bottom of the magnet, the magnetic flux leakage will be further reduced, and the suction force will be further improved.
The current design trend of magnetic parts is to increase the utilization of the magnetic field as much as possible. Through the design of multi-pole magnetic circuit or Halbeck magnetic circuit, or through the guidance of some materials with high magnetic permeability, the magnetic field can pass through as much as possible. The suction object forms a magnetic circuit closed loop. Typical applications are:
The rubber magnetic sheet is designed for multi-level magnetization, some are double-sided multi-pole, and some are single-sided multi-pole. The magnet performance of the rubber magnet is very low, but after the multi-pole magnetic circuit design, the magnetic field is densely distributed on the surface. Magnetic flux leakage is very small during adsorption, resulting in better adsorption effect;
The magnetic device of the door suction, through the guidance of the magnetic guide sheet, makes the magnetic circuit almost form a circuit from the adsorbed object during adsorption, so that the utilization rate of the magnetic field is very high, and the intuitive experience is a small magnetic attraction , the suction force is huge when in direct contact.
The design of the magnetic attraction is inseparable from the consideration of the adsorption distance. The above-mentioned adsorption is based on direct contact. If the distance changes, the suction force often changes greatly. The following figure shows several typical single-magnet magnets. Devices and multi-pole magnetic components have a similar rule. The more the number of poles, the greater the suction force when the spacing is 0, but the suction force becomes weaker as the spacing increases.
