Additive manufacturing powder separation device and method based on acoustic method

Abstract

The invention discloses an additive manufacturing powder separation device and method based on an acoustic method, the additive manufacturing powder separation device comprises a vibrating screen and a plurality of stages of acoustic separation mechanisms which are sequentially arranged according to the separation sequence, the vibrating screen and the stages of acoustic separation mechanisms are connected in series through pipelines, and each acoustic separation mechanism is independently connected with a material barrel; and each acoustic separation mechanism comprises a hemispherical ultrasonic phased array, and a focusing sound field is formed by the circle center of the hemispherical ultrasonic phased array. By means of the synergistic effect of the vibrating screen and the ultrasonic phased array sound field, a multi-stage separation structure and an automatic control system are combined, efficient and accurate separation of metal powder with different particle sizes and densities is achieved, and compared with an existing acoustic separation device, the adopted acoustic separation device applies longitudinal force to powder particles through acoustic radiation force; and when powder is replaced for separation, the phase of the ultrasonic phased array does not need to be adjusted, operation is simpler, and the automation degree is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to an additive manufacturing powder separation device and method based on an acoustic method. Background Art

[0002] Additive manufacturing (3D printing) technology is widely used in fields such as aerospace, medical, and automotive. During the additive manufacturing process, metal or non-metal powders are used as raw materials and are melted by lasers or electron beams to form shapes. However, during the forming process, some powders are not completely melted, and these unused powders need to be recycled and reused. Since the powders may be contaminated or their particle sizes may change during use, direct recycling will affect the subsequent printing quality. Therefore, how to efficiently separate and screen reusable powders has become a key issue in the field of additive manufacturing.

[0003] Currently, there are various methods for separating mixed powders, including friction electrostatic separation, air flow separation, chemical separation, vibration separation, flotation method, magnetic separation method, etc. However, each of the above methods has its own limitations. Friction electrostatic separation utilizes the difference in the charged properties of different substances after friction electrification (such as positive and negative electricities or different amounts of charge), and is affected by different electrostatic forces in an electric field, thereby achieving separation. This method is greatly affected by the surface cleanliness, humidity, and shape of the material. Contaminants or moisture will interfere with the charging effect and is only applicable to materials with significant differences in dielectric constants. Air flow separation is based on the differences in the density, shape, and aerodynamic characteristics of particles, and separates light powders from heavy powders through air flow. Air flow separation has poor separation effects on overly fine particles, easily causes fine particles to be carried away by the air flow, and has high requirements for the density differences of different powders. Chemical separation utilizes chemical reagents to selectively react with target components (such as dissolution, precipitation, or flotation) to achieve separation. However, its reagent cost is high, it may produce toxic waste liquids, damage the original properties of the material, and the recovered products need subsequent treatment. The magnetic separation method utilizes the magnetic differences of materials (such as ferromagnetic, paramagnetic, or non-magnetic), and separates magnetic substances from non-magnetic substances by attracting them with a magnetic field. However, it cannot separate non-magnetic materials. The flotation method adsorbs hydrophobic particles through bubbles, causing them to float to the liquid surface, while hydrophilic particles sink. This method requires the addition of flotation reagents, has a high cost, may pollute the environment, and has low separation efficiency for fine particles.

[0004] Currently, existing acoustic separation devices use the acoustic radiation force to cancel out the gravity of target powder particles to achieve the separation effect. It is necessary to accurately calculate the mass of the target powder. When separating different powders, it is necessary to adjust the intensity and position of the acoustic radiation force generated by the phased array to perform separation, and the operation is complex and the technical requirements are high. Therefore, there is an urgent need for an additive manufacturing powder separation device and method based on an acoustic method to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide an additive manufacturing powder separation device and method based on an acoustic method, which can effectively solve the problems existing in the above-mentioned prior art.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: An additive manufacturing powder separation device based on an acoustic method, comprising a vibrating screen and several levels of acoustic separation mechanisms arranged in sequence according to the separation order, and the vibrating screen and each level of acoustic separation mechanism are connected in series through pipelines, and each of the acoustic separation mechanisms is independently connected to a material bucket; and

[0007] Each of the acoustic separation mechanisms includes a hemispherical ultrasonic phased array, and the centers of the hemispherical ultrasonic phased arrays form a focused sound field; the hemispherical ultrasonic phased arrays of each level of the acoustic separation mechanisms increase according to a threshold.

[0008] Preferably, the vibrating screen is equipped with a vibrating motor, and the vibrating motor is used to drive the vibrating screen to vibrate.

[0009] Preferably, the hemispherical ultrasonic phased array is mainly composed of a plurality of ultrasonic transducers, and the distance between the transducers is 5 mm, and the diameter of the focal point is 2 mm.

[0010] Preferably, it includes three levels of acoustic separation mechanisms, namely the first-level acoustic separation mechanism, the second-level acoustic separation mechanism and the third-level acoustic separation mechanism. The output end of the vibrating screen is communicated with the input end of the first-level acoustic separation mechanism through a pipeline. The output end of the first-level acoustic separation mechanism is respectively communicated with the corresponding material bucket and the input end of the second-level acoustic separation mechanism through independent pipelines. The output end of the second-level acoustic separation mechanism is respectively communicated with the corresponding material bucket and the input end of the third-level acoustic separation mechanism through independent pipelines; the output end of the third-level acoustic separation mechanism is communicated with two material buckets through two pipelines.

[0011] Preferably, the vibrating screen and each level of acoustic separation mechanism are equipped with independent mounting frames, and the mounting frames are spliced together.

[0012] Preferably, the vibrating screen and each level of acoustic separation mechanism are distributed from high to low according to the separation order.

[0013] The present invention also discloses an additive manufacturing powder separation method based on an acoustic method, comprising the following steps:

[0014] S1. The powder particles to be recycled enter the vibrating screen for pretreatment, and the powder passing through the vibrating screen enters the acoustic separation mechanism.

[0015] S2. In the acoustic separation mechanism, when passing through the sound field generated by the hemispherical ultrasonic phased array, the powder particles are affected by the acoustic radiation force, so that part of the powder directly enters the corresponding material bucket through the pipeline, and the other part of the powder enters the next level of acoustic separation mechanism;

[0016] S3. Repeat step S2 until the target powder is obtained from the Nth - level acoustic separation mechanism.

[0017] Preferably, the hemispherical ultrasonic phased - array center forms a focused sound field.

[0018] Preferably, in step S2, the powders are separated level by level by regulating the frequencies and sound pressures of the transducers at each level.

[0019] Beneficial effects: Through the synergistic effect of the vibrating screen and the ultrasonic phased - array sound field, combined with the multi - level separation structure and the automatic control system, the present invention realizes the efficient and precise separation of metal powders with different particle sizes and densities. Compared with the existing acoustic separation devices, the acoustic separation device adopted in the present invention applies a longitudinal force to the powder particles by using the acoustic radiation force, and does not need to adjust the phase of the ultrasonic phased - array when changing the powders for separation, with simpler operation and higher automation level. Description of the Drawings

[0020] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, but do not constitute a limitation to the present invention.

[0021] In the drawings:

[0022] Figure 1 is a schematic structural diagram of the additive - manufacturing powder separation device of the present invention;

[0023] Figure 2 is a front view of the additive - manufacturing powder separation device of the present invention;

[0024] Figure 3 is a schematic structural diagram of the acoustic separation mechanism of the present invention;

[0025] Figure 4 is a flowchart of the additive - manufacturing powder separation method of the present invention.

[0026] Reference numerals in the figures: 1, mounting frame; 2, vibrating screen; 21, vibrating motor; 22, feed hopper; 31, first - level acoustic separation mechanism; 32, second - level acoustic separation mechanism; 33, third - level acoustic separation mechanism; 41, first cylinder; 42, second cylinder; 43, third cylinder; 44, fourth cylinder; 5, pipeline; 6, ultrasonic phased - array; 7, partition; 81, first outlet; 82, second outlet; 9, universal wheel. Detailed Embodiments

[0027] In order to make the objectives and advantages of the present invention more clear and understandable, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe an additive manufacturing powder separation device and method based on an acoustic method of the present invention or several specific implementation manners, and does not strictly limit the scope of protection specifically claimed by the present invention.

[0028] Embodiment 1: An additive manufacturing powder separation device based on an acoustic method, including a vibrating screen 2 and several stages of acoustic separation mechanisms arranged in sequence according to the separation order, and the vibrating screen 2 and each stage of acoustic separation mechanism are connected in series through a pipeline 5, and each of the acoustic separation mechanisms is independently connected to a material bucket; and each of the acoustic separation mechanisms includes a hemispherical ultrasonic phased array 6, and the centers of the hemispherical ultrasonic phased arrays 6 form a focused sound field; the hemispherical ultrasonic phased arrays 6 of each stage of the acoustic separation mechanism increase according to a threshold value, and the hemispherical ultrasonic phased array 6 is mainly composed of a plurality of ultrasonic transducers.

[0029] As Figure 1 shown, in this embodiment, a three-stage acoustic separation mechanism is used and is arranged in the vertical direction as an example for illustration. The number of acoustic separation mechanisms can be reasonably set according to actual needs;

[0030] The vibrating screen 2 and each stage of acoustic separation mechanism are each equipped with an independent mounting frame 1, and the mounting frames 1 are spliced together. Refer to Figure 1 - Figure 2 shown, the mounting frame 1 is mainly used to position and install the vibrating screen 2 and the acoustic separation mechanism; the connecting rod members of the mounting frame 1 are positioned by right-angle angle codes and connected by bolts. With a modular design, it can be installed according to the actual separation stage requirements; universal wheels 9 are installed at the bottom of the mounting frame 1 to facilitate the movement of the device; an outer shell can be added outside the frame to further ensure the sealing performance and prevent impurities from entering the separation device and affecting the powder quality.

[0031] The vibrating screen 2 is at the uppermost part. The vibrating screen 2 is used to screen metal powders of different particle sizes. A horn-shaped feed hopper 22 is arranged on the vibrating screen 2. After the metal powder to be separated is put into the vibrating screen 2 through the feed hopper 22, the powder gathers on the vibrating screen 2 mesh along the flow channel. The vibrating screen 2 is equipped with a vibrating motor 21. When the vibrating motor 21 is turned on, the screen vibrates accordingly, enabling the powder smaller than the screen aperture to quickly pass through the screen, ensuring that the recovered powder meets the usage requirements;

[0032] Below the vibrating screen 2 is the first-stage acoustic separation mechanism 31. The sound radiation force is generated on the powder to be separated through the sound field generated by the ultrasonic phased array 6. Metal powders of different particle sizes and different densities are affected by different sound radiation forces, thereby realizing the separation of powders with different physical properties; As Figure 3As shown, the phased array is connected to the housing of the acoustic separation mechanism by bolts. Small holes are left on the acoustic separation mechanism to facilitate the connection of the phased array to the control board. Sealing requirements are imposed on the rest of the housing of the acoustic separation mechanism. The ultrasonic transducers of the ultrasonic phased array 6 adopt an adjustable frequency type. The ultrasonic phased array 6 consists of multiple ultrasonic transducers to form a hemispherical array, which is fixed to the housing of the separation cavity by bolts. The transducer spacing is 5 mm, and a focused sound field is formed at the center of the hemispherical phased array. The diameter of the focal point is 2 mm. The ultrasonic phased array 6 adopted is a hemispherical phased array. Compared with the existing planar phased array, the center of the hemispherical phased array is the focal point. All transducers only need to adjust the same frequency and do not need to adjust the phase. The control system is simpler. According to the beam angle of the transducer and the principle of acoustic wave attenuation, when the distance between the two sides is the same, the double-sided hemispherical ultrasonic transducer array will generate a stronger focused sound field at the focal point than the planar array, generate a greater acoustic radiation force, and have a better control effect;

[0033] After being screened by the first-stage acoustic separation mechanism 31, a part of the powder enters the cartridge connected thereto through the pipeline 5, that is, into the first cartridge 41, and the other part enters the second-stage acoustic separation mechanism 32 through the pipeline 5. Refer to Figure 3 As shown, at the bottom of the housing of the first-stage acoustic separation mechanism 31, it is divided into a first outlet 81 and a second outlet 82 by a partition plate 7. The first outlet 81 is connected to the first cartridge 41 through the pipeline 5, and the second outlet 82 is connected to the second-stage acoustic separation mechanism 32 through the pipeline 5. The second-stage acoustic separation mechanism 32 is similarly screened, so that a part of the powder enters the cartridge connected thereto through the pipeline 5, that is, into the second cartridge 42, and the other part enters the third-stage acoustic separation mechanism 33 through the pipeline 5; The third-stage acoustic separation mechanism 33 is similarly screened, so that a part of the powder enters a cartridge connected thereto through the pipeline 5, that is, into the third cartridge 43, and the other part of the powder enters another cartridge connected thereto through the pipeline 5, that is, into the fourth cartridge 44.

[0034] Embodiment 2: Refer to Figure 4 As shown, a method for separating additive manufacturing powder based on an acoustic method includes the following steps:

[0035] When recycling powder particles, the powder particles to be recycled first enter the vibrating screen 2. Under the action of the vibrating motor 21, the particles larger than the mesh aperture of the screen cannot pass through the screen and are separated out, and the particles smaller than the mesh aperture of the screen quickly pass through the screen and enter the next separation structure; This step preliminarily screens the powder particles, separating impurities and large particles in the powder. In addition, the particles adhered to each other under the action of vibration and impact are forcibly dispersed;

[0036] Next, the old powder particles pass through the first-stage acoustic separation mechanism 31. The powder to be separated is subjected to the acoustic radiation force when passing through the acoustic field generated by the ultrasonic phased array 6. The metal powders with different particle sizes and densities are subjected to different acoustic radiation forces, so that the powder particles enter different powder outlets. A part of the powder directly enters the first material barrel through the pipeline 5, and the other part of the powder enters the next-stage acoustic separation mechanism.

[0037] Then, the powder particles entering the second-stage acoustic separation mechanism 32 are again subjected to the acoustic radiation force of the ultrasonic phased array 6 sound field, and different powder particles enter different powder outlets. Part of the powder enters the corresponding material barrel through the pipeline 5, and the other part of the powder enters the next-stage acoustic separation mechanism.

[0038] Finally, the powder particles entering the third-stage acoustic separation mechanism 33 are separated again under the action of the ultrasonic phased array 6 sound field, and different powder particles enter different powder outlets and fall into corresponding different material barrels.

[0039] Combining the dual functions of mechanical screening by the vibrating screen 2 and acoustic field separation by the ultrasonic phased array 6, the vibrating screen 2 is used for pretreatment to screen out powders with obvious differences in particle size and forcibly disperse the bonded particles; the ultrasonic phased array 6 performs secondary fine separation of the powder through acoustic radiation force, and achieves precise sorting based on differences in physical properties such as density and particle size; the multi-stage series design optimizes the separation effect step by step, significantly improving the recovery rate and purity.

[0040] This embodiment takes a three-stage acoustic separation mechanism and takes the separation of mixed powder particles with a particle size of 20 to 100 um as an example:

[0041] Start the sonic generator, turn on the vibration motor 21, and put the metal powder in from the entrance. Under the action of vibration, the powder with a particle size smaller than the mesh aperture (particle size less than 100um) passes through the mesh and falls into the lower pipe 5 to quickly pass through the mesh. The powder with a particle size larger than the mesh aperture (particle size greater than 100um) cannot enter the next stage of separation. At the same time, the powder on the mesh is subjected to vibration shock, so that the powder particles that are bonded to each other are forced to disperse.

[0042] The powder particles falling into the pipe 5 enter the first-stage acoustic separation mechanism 31 under the action of gravity. The frequency of the ultrasonic transducer of the first acoustic separation device is 20 khz. Metal powders of different particle sizes and densities are subjected to different acoustic radiation forces. Under the action of the longitudinal acoustic radiation force, the falling path of the powder particles is offset. The falling powder particles are divided into two parts by the partition 7 in the shell of the acoustic separation mechanism. A part of the powder particles with a larger particle size (particle size is 70-100um) directly enters the first barrel through the pipe 5, and the other part of the powder particles (particle size is 20-70um) enters the second-stage acoustic separation mechanism 32 through the pipe 5, and the small-particle powder is separated.

[0043] The frequency adopted by the ultrasonic transducer of the second-stage acoustic separation mechanism 32 is 40 khz. The powder particles entering the second-stage acoustic separation mechanism 32 are affected by the acoustic radiation force of the sound field generated by the ultrasonic phased array 6, and the falling path of the powder particles is offset. The falling powder particles are divided into two parts by the partition 7 in the shell of the acoustic separation mechanism. The powder particles with a particle size of 50 to 70 um enter the second material barrel through the pipe 5, and the powder particles with a particle size of 20 to 50 um enter the third-stage acoustic separation mechanism 33 through the pipe 5.

[0044] The frequency of the ultrasonic transducer of the third-stage acoustic separation mechanism 33 is 80 khz. The powder particles entering the third-stage acoustic separation mechanism 33 are again subjected to the acoustic radiation force. Similarly, the falling path of the powder particles is offset. The powder particles with a particle size of 20 to 30 um enter the fourth barrel, and the remaining powder particles enter the third barrel.

[0045] In this embodiment, the volume of the barrel is 50L, and a pressure sensor is installed at the bottom. When the weight of the powder in the barrel reaches the set threshold, the sensor triggers an audible and visual alarm and stops the powder delivery.

[0046] Among them: According to the law of conservation of momentum of the sound field, the general expression of the sound radiation force can be derived as follows:

[0047] F=-∫∫ s <t>dA;

[0048] dA = ndA, where n is the unit normal vector of the object surface and A is the object surface, <t>It is called the average acoustic radiation stress tensor, and its specific expression is:

[0049]

[0050] Where p and v represent the sound pressure and particle velocity respectively, I represents the second-order unit tensor, ρ0 and c0 are the density of the fluid and the longitudinal wave sound speed respectively, and < > represents taking the time average of the physical quantity.

[0051] In this embodiment, the three-stage acoustic separation device can achieve step-by-step powder separation by regulating the frequency and sound pressure of each stage of transducer: when the powder passes through the focused sound field generated by the transducer, it will be affected by the acoustic radiation force. For powders with a particle size r < λ (the frequency of the sound wave output by the transducer is f, and the wavelength of the sound wave λ = c / f, where c is the sound speed), in the quasi-static field such as the focused sound field, the acoustic radiation force it receives can be:

[0052]

[0053] Where p0 is the sound pressure amplitude, ρ is the fluid density, c is the fluid sound speed, and ρ p is the powder density; therefore, for powders of the same type and different particle sizes, the larger the particle size, the greater the acoustic radiation force received; for powders of the same particle size and different types, the greater the density, the greater the acoustic radiation force received.

[0054] When separating powders of different particle sizes, the powder separation threshold can be controlled by adjusting the frequency and sound pressure. For example, when separating powders of 20 - 100 μm, if you want to finally obtain powders of 20 - 30 μm, you can separate powders of 20 - 70 μm and 70 - 100 μm in the first powder separation, powders of 20 - 50 μm and 50 - 70 μm in the second separation, and powders of 20 - 30 μm and 30 - 50 μm in the third separation. The specific implementation scheme is as follows:

[0055] During the separation process, the acoustic radiation force is regulated to separate the large-particle-size powders. The thresholds for the three times are 70 μm, 50 μm, and 30 μm respectively. That is, the critical condition for each stage of separation is that the acoustic radiation force received by the powders with the threshold particle size is equal to the sum of the gravity F G and the Stokes drag F f , that is:

[0056] F rad = F G + F f ;

[0057] F f ∝ -ρ p r 2 v;

[0058] Where v is the falling velocity of the powder, and thus it can be obtained:

[0059] Ar 3 f = Br 3 + Cr 2 ;

[0060] where A, B, and C are constants, it can be obtained that:

[0061]

[0062] where D and E are constants. Therefore, the frequencies of each level can increase with the threshold particle size. At the same time, since the sound pressure level will decrease when the sound wave frequency emitted by the transducer deviates from the center frequency, the input voltage can be appropriately increased to meet the requirements of the acoustic radiation force.

[0063] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. For those of ordinary skill in the art in this technical field, after learning the content recorded in the present invention, without departing from the principle of the present invention, several equivalent transformations and substitutions can still be made, and these equivalent transformations and substitutions should also be regarded as belonging to the protection scope of the present invention.< / t> < / t>

Claims

1. An additive manufacturing powder separation device based on an acoustic method, characterized in that: It comprises a vibrating screen and several levels of acoustic separation mechanisms which are arranged in sequence according to the separation order, and the vibrating screen and the acoustic separation mechanisms at each level are connected in series through pipelines, and each of the acoustic separation mechanisms is independently connected to a material barrel; and Each of the acoustic separation mechanisms comprises a hemispherical ultrasonic phased array, and the center of the hemispherical ultrasonic phased array forms a focused sound field; the hemispherical ultrasonic phased array of each level of the acoustic separation mechanism increases progressively according to a threshold value.

2. The device for separating powders for additive manufacturing based on acoustic method according to claim 1, characterized in that: The vibrating screen is equipped with a vibrating motor, and the vibrating motor is used to drive the vibrating screen to vibrate.

3. The device for separating powders for additive manufacturing based on acoustic method according to claim 1, characterized in that: The hemispherical ultrasonic phased array is mainly composed of a plurality of ultrasonic transducers, and the transducer spacing is 5 mm, and the focal point diameter is 2 mm.

4. The device for separating powders for additive manufacturing based on acoustic method according to claim 1, characterized in that: It includes three levels of acoustic separation mechanisms, namely a first-level acoustic separation mechanism, a second-level acoustic separation mechanism and a third-level acoustic separation mechanism. The output end of the vibration screen is connected with the input end of the first-level acoustic separation mechanism through a pipeline, the output end of the first-level acoustic separation mechanism is connected with the corresponding barrel and the input end of the second-level acoustic separation mechanism through independent pipelines, the output end of the second-level acoustic separation mechanism is connected with the corresponding barrel and the input end of the third-level acoustic separation mechanism through independent pipelines; the output end of the third-level acoustic separation mechanism is connected with two barrels through two pipelines.

5. The device for separating powders for additive manufacturing based on acoustic method according to claim 1, characterized in that: The vibrating screen and each level of acoustic separation mechanism are equipped with independent mounting frames, and the mounting frames are spliced ​​with each other.

6. The device for separating powders for additive manufacturing based on acoustic method according to claim 1, characterized in that: The vibrating screens and acoustic separation mechanisms at various levels are distributed from high to low in the separation order.

7. A method for separating powder in additive manufacturing based on acoustic method, characterized in that: The steps include: S1. The powder particles to be recycled enter the vibrating screen for pretreatment, and the powder passing through the vibrating screen enters the acoustic separation mechanism. S2. In the acoustic separation mechanism, when passing through the acoustic field generated by the hemispherical ultrasonic phased array, the powder particles are affected by the acoustic radiation force, so that part of the powder particles directly enter the corresponding material barrel through the pipeline, and the other part of the powder particles enter the next acoustic separation mechanism; S3. Repeat step S2 until the target powder is obtained from the Nth stage acoustic separation mechanism.

8. The method for separating powder in additive manufacturing based on acoustic method according to claim 7, characterized in that: The hemispherical ultrasonic phase-controlled center forms a focused sound field.

9. The method for separating powder in additive manufacturing based on acoustic method according to claim 8, characterized in that: The powder is separated step by step by adjusting the frequency and sound pressure of each level of transducer.

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