TWI832719B - Screening device and screening method - Google Patents

Abstract

A screening device includes a tank, a screening module, and an electromagnet. The screening module is in the tank and includes a screen mesh, a permanant magnet, and an induction component. The permanant magnet is fixed on a top surface or a bottom surface of the screen mesh. The induction component is fixed on an inner wall of the tank, and a bending portion of the induction component is below the permanant magnet. The electromagnet is disposed around the induction component and provides alternating magnetic fields. The electromagnet is configured to induce the induction component. Powders are sieved through magnetic vibration sieving, which could avoid problems such as surface oxidation of highly active metal powders or dust explosions.

Description

Screening device and screening method

The present disclosure relates to a screening device and a screening method, and in particular to a screening device and screening method for highly active metal powders.

The vacuum inert gas atomization process can produce high-quality metal powder. In recent years, as the demand for powders for additive manufacturing has increased, many companies have invested in the preparation of metal powder for additive manufacturing. Although the unit price of laminated powders is high, the market is therefore limited to the biomedical industry with high unit prices and small-scale sample preparation. Analyzing the reasons, in addition to the high price of metal powder, the slow process speed and the huge disparity between equipment investment and turnover have resulted in high overall costs and restricted industrial development.

Another very important use of high-quality metal powder is the powder metallurgy industry, including powder forging and powder injection molding. There is a complete industrial chain in China. The products are widely used in tool hardware, transportation tools and electronic components. In addition to metal powder A small part of it is prepared by water mist method and large gas atomization method, while most of the others rely on imports.

Metal powder screening technology has been widely used in various industries. Currently, powder screening through mechanical vibration or ultrasonic vibration has been developed. However, when screening highly active metal powders (such as aluminum powder or magnesium powder), there will be problems with surface oxidation. In addition, ultrasonic vibration screening machines attach piezoelectric materials to the surface of the screen to vibrate to achieve screening purposes. However, when the piezoelectric material is turned on, there will be electricity that causes the piezoelectric material to come into contact with the powder, causing sparks or It's possible a dust explosion. Therefore, how to avoid the above problems is a subject that needs improvement in the field of screening technology.

In order to solve the above problems and overcome the shortcomings of the existing technology, the present disclosure provides a screening device and a screening method, which can avoid surface oxidation of highly active metal powder by controlling the vibration frequency and vibration intensity of the screen with an alternating magnetic field. Or the ultrasonic vibrating screening machine may produce sparks or dust explosions due to contact between the piezoelectric material and the powder.

The screening device provided by at least one embodiment of the present invention includes a barrel, a first screening module and a first electromagnet. The first screening module is located in the barrel, where the first screening module includes a first screen, a first permanent magnet and a first magnetic sensing element. The first screen is fixed in the barrel, wherein the first screen includes a first upper surface and a first lower surface opposite to the first upper surface. The first permanent magnet is fixed on the first upper surface or the first lower surface of the first screen. The first magnetic sensing element is fixed on the inner wall of the barrel and is used to attract or repel the first permanent magnet. The first electromagnet is located around the first magnetically sensitive element and provides a first alternating magnetic field. The first electromagnet is configured to electromagnetically induce the first magnetically sensitive element, so that the first permanent magnet and the first screen mesh are in the axial direction of the barrel. Vibration occurs in the direction.

In at least one embodiment of the present invention, the screening device further includes a second permanent magnet, wherein the first screen mesh is sandwiched between the first permanent magnet and the second permanent magnet.

In at least one embodiment of the present invention, the screening device further includes a magnetic field supplier, wherein the magnetic field supplier is electrically connected to the first electromagnet to provide a first alternating magnetic field.

In at least one embodiment of the present invention, the first permanent magnet is fixed at the center of the first screen.

In at least one embodiment of the present invention, the screening device further includes a second screening module and a second electromagnet. The second screening module is located in the barrel and below the first screening module. The second screening module includes a second screen, a second permanent magnet and a second magnetic sensing element. The second screen is fixed in the barrel, wherein the second screen includes a second upper surface and a second lower surface opposite to the second upper surface. The second permanent magnet is fixed on the second upper surface or the second lower surface of the second screen. The second magnetic sensing element is fixed on the inner wall of the barrel and is used to attract or repel the second permanent magnet. The second electromagnet is located around the second magnetically sensitive element and provides a second alternating magnetic field. The second electromagnet is configured to electromagnetically induce the second magnetically sensitive element, so that the second permanent magnet and the second screen mesh are in the axial direction of the barrel. Vibration occurs in the direction.

The screening method provided by at least one embodiment of the present invention includes placing powder in a screening device as described above, so that the powder is screened to a target size.

In at least one embodiment of the present invention, the powder system is sieved in an inert environment.

In at least one embodiment of the present invention, the first electromagnet is electrically connected to the magnetic field supplier, and the vibration frequency and vibration intensity of the first permanent magnet and the first screen are adjusted through parameters of the magnetic field supplier.

In at least one embodiment of the present invention, the parameters include magnetic field frequency, magnetic field strength and magnetic field direction.

In at least one embodiment of the present invention, the screening method further includes adjusting the distance between the first magnetic sensing element and the first permanent magnet in the screening device.

The following disclosure provides many different implementations, or examples, for implementing various features of the present disclosure. Specific embodiments of components and arrangements are described below to simplify this disclosure. These are of course only examples and not intended to be limiting. For example, in the following description, the formation of the first feature above or on the second feature may include an embodiment in which the first feature and the second feature are in direct contact, or may include another embodiment. Features may be formed between the first feature and the second feature such that the first feature and the second feature may not be in direct contact. In addition, this disclosure may repeat reference numbers and/or text in different instances. The purpose of repetition is to simplify and clarify the description but not to define the relationship between the various embodiments and/or configurations discussed.

In addition, spatially relative terms such as "below", "below", "below", "above", "above" and other similar terms are used to facilitate the description of one element or feature in the figure and another. A relationship between a component or feature. Spatially relative terms cover not only the orientation depicted in the figures, but also other orientations of the device when in use or operation. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It will be understood that, although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of the embodiments. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

FIG. 1 is a schematic three-dimensional view of a cyclone dust collection device 10 according to an embodiment of the present disclosure. Referring to FIG. 1 , the cyclone dust collecting device 10 includes a feed pipe 11 , a cylindrical barrel 12 and a conical barrel 13 . The feed pipe 11 is located on one side of the cylindrical barrel 12 and is connected to the cylindrical barrel 12 . The conical barrel 13 is located below the cylindrical barrel 12 and connected to the cylindrical barrel 12 . The feed pipe 11 is the inlet of the dust-containing air flow. The dusty airflow contains powder, where the powder includes lighter particles (fine particles) and heavier coarse particles (coarse particles). The powder can be non-magnetic powder, ceramic powder or metal powder. The metal powder may be highly active metal powder such as aluminum powder or magnesium powder.

The cyclone dust collecting device 10 in Figure 1 also includes a screening device 14 and an air outlet pipe 15. The screening device 14 is located below the cone barrel 13 and connected to the cone barrel 13 . The air outlet pipe 15 is located at the center of the cylindrical barrel 12 and is connected to the cylindrical barrel 12 . The diameter of the air outlet pipe 15 is smaller than the diameter of the cylindrical barrel 12 . A part of the air outlet pipe 15 protrudes from the upper surface of the cylindrical barrel 12 along the axial direction A. The cylindrical barrel 12, the conical barrel 13, the screening device 14 and the air outlet pipe 15 are arranged along the same axis direction, that is, the cylindrical barrel 12, the conical barrel 13, the screening device 14 and the air outlet pipe 15 are coaxial.

When the dust-containing airflow enters the cylindrical barrel 12 along the tangential direction, the powder (including fine particles and coarse particles) in the dust-containing airflow spirals downward from the cylindrical barrel 12 toward the conical barrel 13 . The powder generates centrifugal force due to the rotation of the air flow. The air flow drag force (drag force) of the lighter particles is greater than the centrifugal force, causing the particles to move toward the upper feed pipe 11 and be discharged from one end of the air outlet pipe 15, while the heavier particles Since the drag force of the air flow is smaller than the centrifugal force, the coarse particles are thrown toward the inner wall of the conical barrel 13 . When the coarse particles contact the inner wall, they will lose inertial force, causing the coarse particles to slide downward into the screening device 14 due to the influence of gravity. In other words, the coarse particles herein are the source of powder for the screening device 14 .

FIG. 2 is an exploded view of the screening device 14 in FIG. 1 . Figure 3 is a schematic cross-sectional view of the screening device 14 in Figure 1 . 4A and 4B are partial enlarged views of the first screen 162 and the permanent magnets 164 and 165. Referring to FIG. 2 , the screening device 14 includes a barrel 150 , a first screening module 160 , a second screening module 170 , a first electromagnet 180 and a second electromagnet 190 .

Referring to Figure 3, the first screening module 160 is located in the barrel 150. The first screening module 160 includes a first screen 162, where the first screen 162 is coaxial with the barrel 150, as shown in Figures 2 and 3. The first screen 162 is fixed in the barrel 150 . For example, the first screen 162 can be fixed on the inner wall 150s of the barrel 150 by screw locking or welding.

Please refer to FIG. 3 , FIG. 4A and FIG. 4B at the same time. The first screening module 160 also includes a permanent magnet 164 and a permanent magnet 165 . The permanent magnet 164 and the permanent magnet 165 are arranged opposite to each other. In detail, the permanent magnet 165 is located directly below the permanent magnet 164 . The first screen 162 includes a first upper surface ts1 and a first lower surface bs1 opposite to the first upper surface ts1. The permanent magnet 164 is located on the first upper surface ts1 of the first screen 162 , and the permanent magnet 165 is located on the first lower surface bs1 of the first screen 162 . In other words, the first screen 162 is located between the permanent magnets 164 and 165. In more detail, due to the characteristics of opposite poles of the permanent magnets attracting each other, the permanent magnets 164 and 165 attract each other, so that the first screen 162 is sandwiched between the permanent magnets 164 and 165 . In some embodiments, permanent magnets 164 and 165 may include ferromagnetic or ferrite materials, such as iron, cobalt, or nickel.

In the embodiment of FIG. 3 , two permanent magnets, namely permanent magnets 164 and 165 , are fixed on both sides of the first screen 162 . However, in other embodiments, the first screening module 160 may have only one permanent magnet, namely the permanent magnet 164 or 165. In one embodiment, the permanent magnet 164 can be fixed on the first upper surface ts1 of the first screen 162 by gluing. In one embodiment, the permanent magnet 165 can be fixed on the first lower surface bs1 of the first screen 162 by gluing.

In the embodiment of FIG. 3 , the permanent magnets 164 and 165 are located in the center of the first screen 162 , that is, the permanent magnets 164 and 165 are coaxial with the first screen 162 . However, in other embodiments, the permanent magnets 164 and/or 165 may not be located at the center of the first screen 162. For example, the permanent magnets 164 and/or 165 may be disposed eccentrically on the first screen 162, or may be located close to the bucket. The inner wall of 150 is located at 150s.

Referring to FIG. 3 , the first screening module 160 also includes a first magnetic sensing element 166 . The first magnetic sensing element 166 is fixed on the inner wall 150s of the barrel 150 to generate an attraction or repulsion force with the permanent magnets 164 and/or 165 . In the embodiment of FIG. 3 , the first magnetically sensitive element 166 includes an extension portion 166 a and a bent portion 166 b connected to the extension portion 166 a. The bent portion 166b has an L-shaped cross section, and the first magnetic sensing element 166 has a similar J-shaped cross section. The extension portion 166 a extends parallel to the radial direction R, while one end of the bent portion 166 b extends parallel to the axial direction A, and the other end of the bent portion 166 b is located below the permanent magnets 164 and 165 . In some embodiments, bend 166b overlaps permanent magnets 164 and 165 when viewed parallel to axial direction A. Preferably, along the direction parallel to the axial direction A, the projected area of the permanent magnets 164 and 165 is no larger than the projected area of the other end of the bent portion 166b, and is completely covered by the projected area of the other end of the bent portion 166b. The extension part 166a is fixed on the inner wall 150s of the barrel 150. For example, the extension part 166a can be fixed on the inner wall 150s of the barrel 150 by screw locking or welding. It should be noted that regardless of whether the permanent magnets 164 and/or 165 are located at the center of the first screen 162, the bent portion 166b will be located below the permanent magnets 164 and 165.

Referring to FIG. 3 , the first electromagnet 180 of the screening device 14 is located outside the barrel 150 . It should be noted that the first electromagnet 180 is a movable component. The first electromagnet 180 is located around the first magnetic sensing element 166 and provides a first alternating magnetic field. In detail, the screening device 14 may include a magnetic field supplier (not shown), which is electrically connected to the first electromagnet 180 to provide a first alternating magnetic field. The first electromagnet 180 is configured to electromagnetically induce the first magnetic sensing element 166 . In some embodiments, first electromagnet 180 is a solid electromagnet. In some embodiments, the first electromagnet 180 may include ferromagnetic material or ferrite magnetic material, such as iron-based, cobalt-based, nickel-based and other metal materials. In some embodiments, the first magnetic sensing element 166 is composed of a paramagnetic material or a material with good magnetic permeability, such as iron-based, cobalt-based, nickel-based and other materials that can generate a magnetic field through electromagnetic induction.

Specifically, please refer to FIG. 3. When the first electromagnet 180 close to one end of the first magnetic sensitive element 166 has an N pole, the same magnetic pole will also be generated at one end of the first magnetic sensitive element 166 close to the first electromagnet 180. (ie N pole), so that one end of the bent portion 166b of the first magnetic sensitive element 166 generates a corresponding reverse magnetic pole (ie S pole). And because the first electromagnet 180 has an alternating magnetic field that changes with time, the end of the first electromagnet 180 also has a magnetic pole that changes with time, so that one end of the bent portion 166b of the first magnetic sensor element 166 also induces Magnetic poles changing over time. In this way, a time-varying force (magnetic force) of attraction of opposite poles and repulsion of like poles is generated between the bent portion 166b and the permanent magnets 164 and 165. Therefore, the permanent magnets 164 and 165 and the first screen 162 can cooperate with each other. Vibration is generated in the axial direction A of the barrel tank 150 to achieve the function of screening powder. In other words, one end of the first magnetically sensitive element 166 is affected by the alternating magnetic field of the first electromagnet 180, and a reverse magnetic field appears at the other end of the first magnetically sensitive element 166, attracting or repelling the permanent magnets 164 and 164 on the first screen 162. /or 165, causing the first screen 162 to vibrate up and down in the axial direction A.

The distance D1 between the bent portion 166b and the permanent magnet 165 can be adjusted according to the desired screening effect. When the distance D1 is smaller, the magnetic force of opposite poles attracting each other and like poles repelling each other is greater. It is worth noting that the present disclosure uses magnetic force to vibrate the first screen 162 to screen the powder. The first magnetic sensing element 166 does not contact the first screen 162 and the permanent magnets 164 and 165. Therefore, overshooting can be avoided. Sonic vibration screening machines may cause sparks or dust explosions due to contact between piezoelectric materials and powder.

Referring to FIG. 3 , the second screening module 170 is located in the barrel 150 and below the first screening module 160 . The second screening module 170 includes a second screen 172, permanent magnets 174 and 175, and a second magnetic sensing element 176. The second screen 172 is fixed in the barrel 150 , wherein the second screen 172 includes a second upper surface ts2 and a second lower surface bs2 opposite to the second upper surface ts2. The permanent magnet 174 is fixed on the second upper surface ts2 of the second screen 172, and the permanent magnet 175 is fixed on the second lower surface bs2 of the second screen 172. The second magnetic sensitive element 176 includes an extension portion 176a and a bent portion 176b connected to the extension portion 176a. The extension part 176a is fixed on the inner wall 150s of the barrel 150, and the bent part 176b is located below the permanent magnets 174 and 175. The distance D2 between the bent portion 176b and the permanent magnet 175 can be adjusted according to the desired screening effect.

Each component in the second screening module 170 and each component in the first screening module 160 have similar structures and materials, and will not be repeatedly discussed here. It should be noted that the mesh number of the first screen 162 is smaller than the mesh number of the second screen 172 .

It can be understood that, similar to the modified embodiment of the first screening module 160 , the second screening module 170 may have only one permanent magnet, that is, the permanent magnet 174 or 175 . In one embodiment, the permanent magnet 174 can be fixed on the second upper surface ts2 of the second screen 172 by gluing. In one embodiment, the permanent magnet 175 can be fixed on the second lower surface bs2 of the second screen 172 by gluing. In some embodiments, the permanent magnets 174 and/or 175 may not be located at the center of the second screen 172. For example, the permanent magnets 174 and/or 175 may be located close to the inner wall 150s of the bucket 150.

Referring to FIG. 3 , the second electromagnet 190 and the first electromagnet 180 have similar structures and materials. The second electromagnet 190 is located around the second magnetically sensitive element 176 and provides a second alternating magnetic field. The second electromagnet 190 is configured to electromagnetically induce the second magnetically sensitive element 176 so that the permanent magnets 174 and 175 cooperate with the second screen 172 Vibration is generated in the axial direction A of the barrel tank 150 .

It should be noted that two screening modules (ie, the first screening module 160 and the second screening module 170) are shown in the embodiments of Figures 2 and 3, but the number of screening modules is not the same. Not limited to this. In other words, the number of screening modules can be reduced or increased according to the screening requirements, for example, there can be one, three, four, five or more screening modules. When the number of screening modules is greater than two, the mesh numbers of the screens in the screening modules increase sequentially from top to bottom.

This disclosure also proposes a screening method, including the following steps. See Figure 3. The powder (ie, the coarse particles mentioned above) is placed in the screening device 14 so that the powder is screened to a target size, where the target size can be adjusted according to actual needs. In the embodiment of FIG. 3 , the first alternating magnetic field is provided by the first electromagnet 180 to electromagnetically induce the first magnetic sensing element 166 in the first screening module 160 , so that the permanent magnets 164 and/or 165 are connected to the first magnetic field. A screen 162 vibrates together in the axial direction A of the barrel 150 to perform the first screening, and then sieve the powder into a first screening powder and a second screening powder, wherein the first screening powder The sieved powder is located above the first screen 162 , and the second sieved powder is located below the first screen 162 . It can be understood that the particle size of the first sieved powder is larger than the particle size of the second sieved powder.

The first alternating magnetic field of the first electromagnet 180 can be generated by electrically connecting a magnetic field supplier (not shown), and the parameters of the magnetic field supplier are used to adjust the relationship between the permanent magnets 164 and/or 165 and the first The vibration frequency and vibration intensity of the screen 162. In some embodiments, parameters of the magnetic field provider include magnetic field frequency, magnetic field strength, and magnetic field direction. In some embodiments, the parameters of the magnetic field supplier can be adjusted according to the weight and particle size distribution of the powder. In some embodiments, the screening method further includes adjusting the distance between the first magnetic sensing element 166 and the permanent magnets 164 and/or 165 in the screening device 14 .

Still referring to FIG. 3 , after the first screening is performed, a second alternating magnetic field is provided by the second electromagnet 190 . The second magnetic sensing element 176 in the second screening module 170 is electromagnetically induced by the second alternating magnetic field, so that the permanent magnets 174 and/or 175 and the second screen 172 are aligned in the axial direction A of the barrel 150 Vibration is generated on the screen, and a second screening is performed to screen the second screening powder into a third screening powder and a fourth screening powder, wherein the third screening powder is located above the second screen 172 , the fourth sieved powder is located below the second screen 172 . It can be understood that the mesh number of the first screen 162 is smaller than the mesh number of the second screen 172 . The particle size of the first sieved powder is greater than the particle size of the third sieved powder, and the particle size of the third sieved powder is greater than the particle size of the fourth sieved powder. Different powder particle sizes are screened out through screens of different mesh sizes to facilitate the subsequent application of powder materials.

The second alternating magnetic field of the second electromagnet 190 can be generated by electrically connecting a magnetic field supplier (not shown), and the parameters of the magnetic field supplier are used to adjust the relationship between the permanent magnets 174 and/or 175 and the second The vibration frequency and vibration intensity of the screen 172. It should be noted that the magnetic field supplier electrically connected to the first electromagnet 180 and the magnetic field supplier of the second electromagnet 190 may be the same magnetic field supplier, or they may be independent magnetic field suppliers. By adjusting the parameters of the magnetic field supplier, excessive powder accumulation and blockage on the first screen 162 and the second screen 172 are avoided, thereby improving the screening efficiency. In addition, the first screening step and the second screening step can be performed simultaneously. In some embodiments, the screening method further includes adjusting the distance between the second magnetically sensitive element 176 and the permanent magnets 174 and/or 175 in the screening device 14 .

In some embodiments, the first screening and/or the second screening are performed in an inert environment. In some embodiments, after the powder is placed in the screening device 14, a closed area is formed in the screening device 14, and an inert gas is introduced into the closed area. The inert gas may be, for example, nitrogen or argon. When the powder is in an environment with inert gas, it can avoid surface oxidation of highly active metal powder (such as aluminum powder or magnesium powder) and maintain the purity of the powder. In other embodiments, when the powder has no concerns such as surface oxidation, the sieving step of the powder can also be performed in an open area (ie, atmospheric environment).

In summary, the screening device provided in this disclosure sieves powder through magnetic vibration sieving, which can avoid surface oxidation of highly active metal powder or ultrasonic vibration screening machine due to piezoelectric materials and powder. Sparks or dust explosions may occur due to physical contact.

The above summary of features of various embodiments allows those skilled in the art to better understand aspects of the present disclosure. Those skilled in the art should appreciate that the present disclosure may be readily used as a basis for designing or modifying other processes and structures that carry out the same purposes and/or achieve the same advantages of the embodiments described herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and various changes, substitutions and modifications may be made herein without departing from the spirit and scope of the disclosure. .

10: Cyclone dust collection device 11:Feeding pipe 12: Cylindrical barrel 13:Conical barrel 14:Screening device 15:Outlet duct 150:Bucket trough 150s:Inner wall 160: First screening module 162:First screen 164,165:Permanent magnet 166: The first magnetic element 166a:Extension 166b:Bending part 170: Second screening module 172:Second screen 174,175:Permanent magnet 176: Second magnetic element 176a:Extension 176b:Bending part 180:First electromagnet 190:Second electromagnet ts1: first upper surface ts2: second upper surface bs1: first lower surface bs2: second lower surface A: Axial direction R: radial direction D1,D2: spacing

Various aspects of the present disclosure are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be understood that, in accordance with standard practice in the industry, various features are not drawn to scale. Indeed, the dimensions of the various features may be arbitrarily increased or reduced for clarity. FIG. 1 is a schematic three-dimensional view of a cyclone dust collector device according to an embodiment of the present disclosure. Figure 2 is an exploded view of the screening device in Figure 1. Figure 3 is a schematic cross-sectional view of the screening device in Figure 1. Figures 4A and 4B are partial enlarged views of the screen and permanent magnets.

Domestic storage information (please note in order of storage institution, date and number) without Overseas storage information (please note in order of storage country, institution, date, and number) without

14:Screening device

150:Bucket trough

160: First screening module

162:First screen

164:Permanent magnet

166: The first magnetic element

170: Second screening module

172:Second screen

174:Permanent magnet

176: Second magnetic element

180:First electromagnet

190:Second electromagnet

Claims (10)

A screening device containing: a barrel trough; A first screening module is located in the barrel, wherein the first screening module includes: A first screen fixed in the barrel, wherein the first screen includes a first upper surface and a first lower surface opposite to the first upper surface; a first permanent magnet fixed on the first upper surface or the first lower surface of the first screen; and A first magnetically sensitive element is fixed on an inner wall of the barrel for attracting or repelling the first permanent magnet; and A first electromagnet is located around the first magnetically sensitive element and provides a first alternating magnetic field. The first electromagnet is configured to electromagnetically induce the first magnetically sensitive element, so that the first permanent magnet and the first screen The net jointly generates vibration in an axial direction of the barrel. The screening device as described in claim 1 further includes: A second permanent magnet, wherein the first mesh is sandwiched between the first permanent magnet and the second permanent magnet. The screening device as described in claim 1 further includes: A magnetic field supplier is electrically connected to the first electromagnet to provide the first alternating magnetic field. The screening device as claimed in claim 1, wherein the first permanent magnet is fixed at a center of the first screen. The screening device as described in claim 1 further includes: A second screening module is located in the barrel and below the first screening module, wherein the second screening module includes: A second screen fixed in the barrel, wherein the second screen includes a second upper surface and a second lower surface opposite to the second upper surface; a second permanent magnet fixed on the second upper surface or the second lower surface of the second screen; and a second magnetically sensitive element fixed on the inner wall of the barrel for attracting or repelling the second permanent magnet; and A second electromagnet is located around the second magnetically sensitive element and provides a second alternating magnetic field. The second electromagnet is configured to electromagnetically induce the second magnetically sensitive element, so that the second permanent magnet and the second screen The net jointly generates vibration in the axial direction of the barrel. A screening method consisting of: Place a powder in a screening device as described in any one of claims 1 to 5, so that the powder is screened to a target size. The screening method as described in claim 6, wherein the powder is screened in an inert environment. The screening method of claim 6, wherein the first electromagnet is electrically connected to a magnetic field supplier, and a vibration of the first permanent magnet and the first screen is adjusted through a parameter of the magnetic field supplier. frequency and vibration intensity. The screening method as claimed in claim 8, wherein the parameters include magnetic field frequency, magnetic field intensity and magnetic field direction. The screening method according to claim 6 further includes adjusting a distance between the first magnetic sensing element and the first permanent magnet in the screening device.

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