Method and device for in-situ regulation and control of initial blank density and density analysis method

Abstract

In order to overcome the defects in the prior art, the invention provides a method and a device for regulating and controlling the density of a primary blank in situ and a density analysis method, according to the density analysis method, the density of the primary blank is analyzed under the dual effects of in-situ vibration and negative pressure, and at the moment, the density of the primary blank is obtained through analysis of an analysis model. Based on the analysis model, a method for increasing the density of the initial blank can be obtained, so that the density of the initial blank is subjected to in-situ regulation and control by applying the vibration frequency, the in-situ vibration amplitude and the negative pressure. In addition, the invention provides a device for realizing in-situ regulation and control of the density of the initial blank, and the device determines the vibration frequency, the vibration amplitude and the negative pressure value based on the density analysis method and provides corresponding vibration and negative pressure environments for the powder bed in the printing process, so that the initial blank with the density close to the preset density is obtained.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically relating to a method, apparatus and density analysis method for in-situ control of the density of a preform. Background Technology

[0002] Binder jetting (BJ), a common two-step additive manufacturing process, works by first selectively bonding powder particles (such as polymers, ceramics, and metals) with an adhesive at room temperature to form a preform sample, which is then post-processed to form a functional component. The powder bed density in the BJ process determines the density of the preform, thus influencing the final density of the component.

[0003] Existing technologies for improving the density of preforms mainly focus on optimizing the powder spreading process or reducing the powder particle size to increase the density of the preform, but both of these methods have limitations: 1. The powder spreading process is affected by a variety of parameters. Traditional scraper-type and reverse roller-type powder spreading processes suffer from problems such as low powder bed packing density and low powder spreading efficiency. Although the packing density and smoothness of the powder bed can be improved by optimizing the scraper inclination angle and roller rotation mode, these methods are still limited by the fixed conditions of powder spreading speed and layer thickness, making it difficult to achieve higher density.

[0004] 2. When the powder particle size is too small, the cohesive forces between the particles (such as van der Waals forces, electrostatic interactions, hydrogen bonds, and capillary bridging) can be comparable to or even greater than gravity. However, due to the strong cohesive forces, fine powders have poor flowability and are therefore difficult to rearrange during the spreading process. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a method for analyzing the density of a billet. This method analyzes the density of a billet under the dual effects of in-situ vibration and negative pressure. The density of the billet under these conditions is obtained through analysis using Equation 1: Formula 1 in, For the initial billet density, For particle size coupling density, This is the process coupling constant. The amplitude of the in-situ vibration. The pressure value is a negative pressure value. The frequency of the in-situ vibration. The average particle size of the powder. The coefficient of friction of the powder is denoted as .

[0006] Furthermore, particle size coupling density We obtain the following from Equation 2: Formula 2 in, To correct the density, For multi-peak filling factor, This refers to the particle size distribution of the powder.

[0007] Furthermore, multi-peak fill factor We obtain the following from Equation 3: Formula 3 in, Let dc be the mass fraction of the i-th particle size powder, and dc be the critical agglomeration particle size. Let be the average particle size of the i-th particle size powder.

[0008] Furthermore, the critical agglomeration particle size dc is obtained through Equation 4: Formula 4 in, To correct the base value, Surface roughness.

[0009] Furthermore, the density was corrected. We obtain the following from Equation 5: Formula 5 in, This is an expression for the synergistic effect of vibration and negative pressure. This is the reference coefficient of friction for the powder. The sphericity of the powder particles.

[0010] Furthermore, the coefficient of friction of the powder We obtain the following from Equation 6: Formula Six in, K1 is the basic friction coefficient, k2 is the roughness influence coefficient, and k3 is the sphericity influence coefficient.

[0011] Furthermore, the expression for the synergistic effect of vibration and negative pressure. We obtain the following from Equation 7: Formula 7 in, This refers to the static bulk density of the powder, typically 40-50%. and The correlation coefficient of the powder. This is the initial reference pressure.

[0012] In addition, the present invention provides a method for in-situ control of the density of a blank, comprising: placing the powder bed in an in-situ vibration and negative pressure state during blank forming, and, based on the above-mentioned method for analyzing the density of the blank, adjusting the in-situ vibration frequency, the in-situ vibration amplitude and the negative pressure to in-situ control the density of the blank.

[0013] Furthermore, this invention also provides an in-situ control device for the density of a preform, comprising: a forming cylinder and a controller; a material-supporting mechanism is provided inside the forming cylinder, and a filter screen is provided at the top of the material-supporting mechanism, on which powder is placed; the bottom of the filter screen is connected to a negative pressure system via an air pipe; the material-supporting mechanism is fixedly connected to the vibrating end of a vibrator, and the vibrator is controlled to vibrate the material-supporting mechanism. An electrically controlled telescopic device is provided at the bottom of the forming cylinder to drive the forming cylinder to move up and down.

[0014] The controller receives control commands obtained from the analysis method based on the initial billet density described above. Based on the control commands, it controls the negative pressure system to form a corresponding negative pressure and controls the vibrator to drive the material support mechanism to vibrate with a corresponding amplitude and vibration frequency.

[0015] Furthermore, the material receiving mechanism consists of, from top to bottom, a filter screen, an upper piston plate, and a lower piston plate. The upper piston plate and the lower piston plate have interconnected airflow channels on their opposite sides. The mesh of the filter screen is connected to the airflow channel of the upper piston plate. The airflow channel of the lower piston plate is connected to the air inlet of the air pipe through an air pipe connector. The air outlet of the air pipe is connected to the negative pressure system. A control valve is provided on the air pipe.

[0016] The filter screen is pressed and installed on the top surface of the upper piston plate by the filter screen pressure plate; a primary sealing ring is provided between the upper piston plate and the lower piston plate at the connection position with the side wall of the forming cylinder.

[0017] The bottom of the forming cylinder is detachably and fixedly connected to the connecting plate through a secondary sealing ring; the bottom of the lower piston plate is provided with a support plate that snaps onto the vibrating end of the vibrator, and a buffer pad is provided between the bottom of the support plate and the top surface of the connecting plate.

[0018] The advantages of this invention are as follows: This invention proposes a method to increase the density of the billet by means of vibration and negative pressure environment, and provides a targeted analysis model of the density of the billet under vibration and negative pressure environment, which can realize effective in-situ adjustment of the density of the billet. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the in-situ regulating device for primary billet density of the present invention; Figure 2 This is a schematic diagram of the airflow channel of the present invention; Figure 3A SEM image of a preliminary blank prepared by the exemplary method of the present invention; Figure 4 SEM image of another roughing stock prepared by the example method of this invention; Figure 5 SEM image of a preform prepared using prior art as an example of the present invention; In the diagram: 1. Molding cylinder; 2. Filter screen pressure plate; 3. Filter screen; 4. Upper piston plate; 5. Lower piston plate; 6. Primary sealing ring; 7. Vibrator; 8. Air pipe connector; 9. Air pipe; 10. Control valve; 11. Buffer pad; 12. Connecting plate; 13. Secondary sealing ring; 14. Electrically controlled telescopic device; 15. Negative pressure system. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0021] Please note that the terms "above", "below", "left", "right", "top", "top", "bottom", "bottom", etc., used in this invention to describe positional relationships do not represent the absolute positional relationship between modules / components / assemblies / parts / components, but rather the relative positional relationship between modules / components / assemblies / parts / components.

[0022] This invention provides an exemplary method for analyzing the density of a billet. This method is used to analyze the density of a billet under the dual effects of in-situ vibration and negative pressure. The density of the billet under these conditions is obtained through analysis using Equation 1: Formula 1 in, For the initial billet density, For particle size coupling density, This is the process coupling constant. The amplitude of the in-situ vibration. The pressure value is a negative pressure value. The frequency of the in-situ vibration. The average particle size of the powder. The coefficient of friction of the powder is denoted as .

[0023] Compared to existing technologies, this invention proposes a method combining in-situ vibration and a negative pressure environment to adjust the density of the initial blank. The principle is as follows: When powder is initially added, the powder bed is loose and porous due to adhesion, friction, van der Waals forces, and electrostatic forces between powder particles, resulting in poor density of the initial blank. This invention, by incorporating mechanical vibration, creates micro-vortices and flow within the powder bed, allowing excess air to escape and significantly reducing adhesion and friction between particles, thus initially improving the density of the powder bed. Simultaneously, the generated negative pressure continues to act on the powder bed, and the suction force further breaks down the interparticle forces, causing them to align tightly. Ultimately, based on the dual effects of mechanical vibration and negative pressure, the density of the in-situ powder bed in the molding cylinder is effectively improved.

[0024] However, the addition of vibration and negative pressure complicates the analysis of powder bed density. Existing technologies lack applicable analytical models to clearly define the changes in powder bed density after the addition of vibration and negative pressure, making it even more difficult to determine the density of the resulting billet. Through research, the applicant has proposed an analytical model as shown in Equation 1. This model incorporates vibration amplitude, vibration frequency, and negative pressure as influencing factors on the density of the billet, enabling the analysis of the density of the billet after being affected by vibration and negative pressure under external conditions.

[0025] This invention provides an exemplary method for particle size coupling density. We obtain the following from Equation 2: Formula 2 in, To correct the density, For multi-peak filling factor, This refers to the particle size distribution of the powder.

[0026] Multi-peak fill factor We obtain the following from Equation 3: Formula 3 in, Let dc be the mass fraction of the i-th particle size powder, and dc be the critical agglomeration particle size. Let be the average particle size of the i-th particle size powder.

[0027] The critical agglomeration size dc is obtained through Equation 4: Formula 4 in, The baseline value is determined based on the average particle size and particle type. Surface roughness.

[0028] Because the particle size of powder is not uniform, but generally has a certain number of particles within a certain size range, for example: A powder bed with a particle size of 40 μm is constructed, wherein the particle size of the powder is approximately 38-42 μm (70%), 20-22 μm (20%), and 69-73 μm (10%). The different particle sizes and distributions affect the packing density; this coupling effect between particle size and distribution should be considered when performing packing density analysis. Therefore, this invention proposes a coupled packing density method. The analysis model was developed, and a multi-peak filling factor was introduced during the analysis process. Using the critical agglomeration particle size dc as the main correction factor, the particle size coupling model shown in Equation 2 is obtained.

[0029] Particle size coupling density It can also be obtained through a large number of experiments as needed. However, compared with the analytical model proposed in this invention, the method obtained through a large number of experiments has obvious limitations. It requires a large number of samples to be tested in a specific environment, which is not suitable for analysis in industrial production environments.

[0030] This invention provides, by way of example, a modified density. We obtain the following through Equation 5: Formula 5 in, This is an expression for the synergistic effect of vibration and negative pressure. This is the reference coefficient of friction for the powder. The sphericity of the powder particles.

[0031] In general, particle sphericity and friction coefficient are not considered when analyzing the density of stationary powder beds. This is mainly because the particles in a stationary powder bed hardly move, and the influence of sphericity and friction coefficient on density is negligible. However, because this invention incorporates vibration and negative pressure during the printing of the preform to improve density, the particles experience greater movement compared to the stationary state, and the spacing between particles is also smaller. Therefore, particle friction and sphericity become significant factors affecting the improvement of density. Accordingly, this invention proposes to introduce the friction coefficient... and shape factor An analytical model that modifies packing density, wherein... This is the reference coefficient of friction for the powder; for metal powder, the value is generally taken as 0.2.

[0032] Corrected density It can also be obtained through a large number of experiments as needed. However, compared with the analytical model proposed in this invention, the method obtained through a large number of experiments has obvious limitations. It requires a large number of samples to be tested in a specific environment, which is not suitable for analysis in industrial production environments.

[0033] This invention provides an exemplary expression for the synergistic effect of vibration and negative pressure. We obtain the following through Equation 7: Formula 7 in, This refers to the static bulk density of the powder, typically 40-50%. and The correlation coefficient of the powder. The initial reference pressure is introduced to avoid excessive negative pressure leading to voids in the powder bed; that is, when the negative pressure P is significantly greater than... When the vibration and negative pressure synergistic effect expression shows an exponential increase and exceeds the preset threshold, this process can indicate to the user that the negative pressure is too high.

[0034] Because this invention applies in-situ vibration and negative pressure to the powder bed, the density of the powder bed will inevitably change under the combined effect of these two forces. Existing technologies lack analytical models for this change, often requiring extensive experiments to determine the density changes of different materials under various conditions. This severely restricts the application of this invention in industrial production. Therefore, this invention proposes an analytical model for the synergistic effect of vibration and negative pressure, providing a reliable theoretical basis for analyzing the density changes of the powder bed under vibration and negative pressure conditions.

[0035] This invention provides an exemplary method for determining the coefficient of friction of a powder. Equation 6 yields: Formula Six in, The coefficient of friction is k1, where k1 is the roughness influence coefficient and k2 is the sphericity influence coefficient. Since this invention applies in-situ vibration and negative pressure to the powder bed, the sphericity and surface roughness of the powder significantly affect the mutual friction ability of the particles. Therefore, it is necessary to correct the coefficient of friction by combining the particle sphericity and surface roughness.

[0036] This invention provides an exemplary method for analyzing the density of a billet, which, by substituting the above-mentioned modified methods into Equation 1, yields: Formula 8 After simplification, we get: Formula Nine Among them, the comprehensive constant Process coupling constant C and material-related parameters α and β are experimentally calibrated based on the selected materials, which are mainly the inherent specific parameters of the target materials. In this way, the present invention provides a multi-scale analysis model of powder bed density that integrates coupled vibration energy, negative pressure adsorption, powder geometry and surface properties, and realizes the analysis under in-situ vibration and negative pressure conditions. This provides a methodological basis for the precise control of powder bed density under in-situ vibration and negative pressure conditions.

[0037] The present invention provides an exemplary method for in-situ controlling the density of a billet, comprising: placing the powder bed in an in-situ vibration and negative pressure state during billet forming, and, based on the above-mentioned method for analyzing the density of the billet, adjusting the in-situ vibration frequency, the in-situ vibration amplitude, and the negative pressure to in-situ control the density of the billet.

[0038] Since this invention provides an analytical model for analyzing the density of a powder bed under vibration and negative pressure conditions, a method for in-situ controlling the density of the initial billet can be obtained based on this model by adjusting the in-situ vibration frequency, in-situ vibration amplitude, and negative pressure.

[0039] This invention provides, by way of example, an apparatus for in-situ regulating the density of a billet, such as... Figure 1 As shown, the device includes: a molding cylinder 1 and a controller. The molding cylinder 1 has a material-supporting mechanism inside, and a filter screen 3 is located at the top of the material-supporting mechanism, on which powder is placed. The bottom of the filter screen 3 is connected to a negative pressure system 15 via an air pipe 9. The material-supporting mechanism is fixedly connected to the vibrating end of a vibrator 7, and the vibrator 7 is controlled to vibrate the material-supporting mechanism. The bottom of the molding cylinder 1 is equipped with an electrically controlled telescopic device 14 that drives the molding cylinder 1 to move up and down.

[0040] The controller receives control commands obtained from the analysis method based on the initial billet density described above. Based on the control commands, it controls the negative pressure system 15 to form a corresponding negative pressure and controls the vibrator 7 to drive the material support mechanism to vibrate with corresponding amplitude and frequency. The control commands can be control commands for the vibration equipment and negative pressure equipment obtained by external equipment or personnel based on the initial billet density analysis method described above, and input into the controller. The controller converts the control commands into corresponding amplitude, frequency, and air pressure control signals for the vibrator 7 and negative pressure system 15 and sends them to the vibrator 7 and negative pressure system 15. Alternatively, after the user inputs the target initial billet density, the controller analyzes the initial billet density to obtain the corresponding amplitude, frequency, and air pressure control signals for the vibrator 7 and negative pressure system 15 according to the initial billet density analysis method described above and sends them to the vibrator 7 and negative pressure system 15.

[0041] This device achieves in-situ vibration and negative pressure application to the powder bed during the initial printing process. The mechanical vibrator operates intermittently, and its high-frequency vibration creates micro-vortices and flow within the powder bed, allowing excess air to escape and significantly reducing interparticle adhesion and friction, thus initially improving the powder bed's density. The negative pressure system operates continuously, applying the negative pressure generated by the vibration to the powder bed. The suction force generated by the negative pressure further breaks down interparticle forces, causing them to clump together tightly. Based on the combined effects of mechanical vibration and negative pressure, the in-situ powder bed density within the forming cylinder is effectively improved.

[0042] Meanwhile, the vibration frequency and vibration amplitude of the vibrator 7 and the magnitude of the negative pressure of the negative pressure system 15 are obtained based on the analysis method of this invention. By adjusting the vibration frequency, vibration amplitude and negative pressure, the spacing between powder particles in the powder bed can be reduced in a controllable manner, thereby increasing the density of the powder bed in an adjustable and controllable manner, and further increasing the density of the initial blank in an adjustable and controllable manner.

[0043] Furthermore, prolonged operation of the negative pressure system 15 can cause clogging of the filter screen 3. In this case, the vibrator 7 not only compacts the particles but also causes them to flow and rearrange on the surface of the filter screen 3, reducing the time particles remain in a fixed position and significantly minimizing clogging. After operation, the negative pressure system 15 can be switched to positive pressure, using high-speed airflow to reverse-clean the airflow channel and filter screen 3, further reducing the likelihood of clogging.

[0044] According to one embodiment of the present invention, such as Figure 1 As shown, the material receiving mechanism consists of, from top to bottom, a filter screen 3, an upper piston plate 4, and a lower piston plate 5. The upper piston plate 4 and the lower piston plate 5 have interconnected airflow channels on their opposite sides. The mesh of the filter screen 3 is connected to the airflow channel of the upper piston plate 4. The airflow channel of the lower piston plate 5 is connected to the air inlet of the air pipe 9 through an air pipe connector 8. The air outlet of the air pipe 9 is connected to the negative pressure system 15. A control valve 10 is provided on the air pipe 9.

[0045] This configuration allows the airflow generated by the negative pressure system 15 to sequentially pass through the filter screen 3, upper piston plate 4, lower piston plate 5, and air pipe 9 into the negative pressure system 15. At this time, the airflow channels of the upper piston plate 4 and lower piston plate 5 are as follows: Figure 2 As shown, by using a wave-shaped or curved structure, the path of airflow can be changed, thereby reducing the formation of turbulence and eddies and allowing for a more uniform distribution of airflow.

[0046] According to one embodiment of the present invention, such as Figure 1As shown, the filter screen 3 is pressed and installed on the top surface of the upper piston plate 4 by the filter screen pressure plate 2; a primary sealing ring 6 is provided between the upper piston plate 4 and the lower piston plate 5 at the connection position with the side wall of the forming cylinder 1.

[0047] The present invention provides a downward pressure to the filter screen 3 through the filter screen pressure plate 2 and an upward support force to the filter screen 3 through the upper piston plate 4. The two form a clamping structure, which can fix the filter screen 3 more stably and prevent the filter screen 3 from sliding during vibration, thereby causing uncontrollable changes in the vibration frequency and vibration amplitude of the powder bed, which in turn affects the density of the powder bed.

[0048] The added primary sealing ring 6 can significantly improve the airtightness between the upper piston plate 4, the lower piston plate 5 and the molding cylinder 1, avoiding the problem that the negative pressure value cannot be accurately controlled due to air leakage, thus affecting the density of the powder bed.

[0049] According to one embodiment of the present invention, such as Figure 1 As shown, the bottom of the forming cylinder 1 is detachably and fixedly connected to the connecting plate 12 through a secondary sealing ring 13; the bottom of the lower piston plate 5 is provided with a support plate for snapping onto the vibration end of the vibrator 7, and a buffer pad 11 is provided between the bottom of the support plate and the top surface of the connecting plate 12.

[0050] The added secondary sealing ring 13 can significantly improve the airtightness between the connecting plate 12 and the molding cylinder 1, avoiding the problem that the negative pressure value cannot be accurately controlled due to air leakage, thereby affecting the density of the powder bed.

[0051] The added buffer pad 11 can change the collision between the bottom of the support plate and the top surface of the connecting plate 12 from a rigid collision to a flexible collision when the lower piston plate 5 is subjected to the vibration of the vibrator 7, thereby reducing the damage caused by the collision and improving the air seal.

[0052] The technical effects of the present invention will be further illustrated below with reference to specific embodiments.

[0053] Example 1 A method for preparing a rough billet, using the in-situ density control device of the present invention, such as... Figure 1 As shown, the device includes: a molding cylinder 1 and a controller. The molding cylinder 1 has a material-supporting mechanism inside, with a filter screen 3 at the top of the mechanism on which powder is placed. The bottom of the filter screen 3 is connected to a negative pressure system 15 via an air pipe 9. The material-supporting mechanism is fixedly connected to the vibrating end of a vibrator 7, which is controlled to vibrate the material-supporting mechanism. The bottom of the molding cylinder 1 is equipped with an electrically controlled telescopic device 14 that drives the molding cylinder 1 to move up and down. The electrically controlled telescopic device 14 can be an electric cylinder, depending on the needs.

[0054] The material receiving mechanism consists of, from top to bottom: a filter screen 3, an upper piston plate 4, and a lower piston plate 5. The upper piston plate 4 and the lower piston plate 5 have interconnected airflow channels on their opposite sides. The mesh of the filter screen 3 is connected to the airflow channel of the upper piston plate 4. The airflow channel of the lower piston plate 5 is connected to the air inlet of the air pipe 9 through an air pipe connector 8. The air outlet of the air pipe 9 is connected to the negative pressure system 15. A control valve 10 is provided on the air pipe 9.

[0055] The filter screen 3 is pressed and installed on the top surface of the upper piston plate 4 by the filter screen pressure plate 2; a primary sealing ring 6 is provided between the upper piston plate 4 and the lower piston plate 5 at the connection position with the side wall of the forming cylinder 1.

[0056] The bottom of the forming cylinder 1 is detachably and fixedly connected to the connecting plate 12 via a secondary sealing ring 13; the bottom of the lower piston plate 5 is provided with a support plate that snaps onto the vibration end of the vibrator 7, and a buffer pad 11 is provided between the bottom of the support plate and the top surface of the connecting plate 12.

[0057] AZ91D powder was spread on filter screen 3 to form a powder bed, with a preset initial compaction density of 0.45. Early test calibration determined the comprehensive constant of the AZ91D powder. 0.85, C=0.15 μm -1 MPa -1 f = 28kHz, α = 0.12, β = 0.05. At this point, based on: Formula Nine The safe and optimal operating ranges of the vibrator 7 and the negative pressure system 15 were determined, resulting in f = 28 kHz, A = 10 μm, and P = -0.08 MPa. At this point, the controller was input with f = 28 kHz, A = 10 μm, and P = -0.08 MPa. The controller then controlled the vibrator 7 to vibrate intermittently at f = 28 kHz and A = 10 μm, with an interval of 1 second. The controller also controlled the negative pressure system 15 to continuously provide a negative pressure of -0.08 MPa.

[0058] Based on the BJ process, printing on a powder bed yields results such as... Figure 3 The initial billet shown was tested using the Archimedes method, and its density was 0.47. The difference between the initial billet and the preset density of 0.45 is H = (0.47-0.45) / 0.45*100% = 4.44%.

[0059] Example 2 The remaining steps, methods, materials, and apparatus are consistent with those in Example 1, except that the initial blank density is preset to 0.55. At this point, based on Equation 9, f = 28 kHz, A = 12 μm, and P = -0.09 MPa are obtained. Based on the BJ process, the blank is printed on a powder bed as shown... Figure 4The initial billet shown was tested using the Archimedes method and found to have a density of 0.53. The difference between the initial billet and the preset density of 0.55 is H = (0.53 - 0.55) / 0.55 * 100% = -3.64%.

[0060] Comparative Example 1 A method for preparing a preform involves using traditional printing equipment to lay AZ91D powder on the printing surface to form a powder bed. Based on the BJ process, a preform is printed on the powder bed as shown in the image. Figure 5 The blank shown, measured by the Archimedes method, has a density of 0.42. Since traditional printing equipment cannot preset the density, the difference between this blank and the preset density cannot be examined.

[0061] visible: Traditional BJ process cannot adjust the initial blank density; it can only obtain the initial blank density based on the density of the powder bed that is naturally formed after the powder is laid, which easily leads to insufficient initial blank density.

[0062] This invention increases the density of the billet by applying external vibration and negative pressure, overcoming the problem of insufficient density of the billet in the traditional BJ process.

[0063] The analytical method based on this invention can make the density of the obtained billet very close to the preset density by controlling the amplitude, vibration frequency and negative pressure, thereby achieving adjustable control of the density of the billet with high control accuracy. The deviation between the density of the obtained billet and the preset density does not exceed 5%.

[0064] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for analyzing the density of a billet, characterized in that, The initial billet is subjected to both in-situ vibration and negative pressure. The density of the initial billet under these conditions is obtained through analysis using Equation 1: Formula 1 in, For the initial billet density, For particle size coupling density, This is the process coupling constant. The amplitude of the in-situ vibration. The pressure value is a negative pressure value. The frequency of the in-situ vibration. The average particle size of the powder. The coefficient of friction of the powder is denoted as .

2. The method for analyzing the density of the initial billet according to claim 1, characterized in that, Particle size coupling density We obtain the following from Equation 2: Formula 2 in, To correct the density, For multi-peak filling factor, This refers to the particle size distribution of the powder.

3. The method for analyzing the density of the initial billet according to claim 2, characterized in that, Multi-peak fill factor We obtain the following from Equation 3: Formula 3 in, Let i be the mass fraction of the powder with the i-th particle size. d c The critical agglomeration particle size, Let be the average particle size of the i-th particle size powder.

4. The method for analyzing the density of the initial billet according to claim 3, characterized in that, Critical Aggregation Size d c We obtain the following from Equation 4: Formula 4 in, To correct the base value, Surface roughness.

5. The method for analyzing the density of the initial billet according to claim 2, characterized in that, Corrected density We obtain the following from Equation 5: Formula 5 in, This is an expression for the synergistic effect of vibration and negative pressure. This is the reference coefficient of friction for the powder. The sphericity of the powder particles.

6. The analytical method for the density of the initial billet according to any one of claims 1 or 5, characterized in that, coefficient of friction of powder We obtain the following from Equation 6: Formula Six in, Based on the coefficient of friction, k 1 This is the roughness influence coefficient. k 2 This is the sphericity influence coefficient.

7. The method for analyzing the density of the initial billet according to claim 5, characterized in that, Expression of the synergistic effect of vibration and negative pressure We obtain the following from Equation 7: Formula 7 in, This refers to the static bulk density of the powder, typically 40-50%. and The correlation coefficient of the powder. This is the initial reference pressure.

8. A method for in-situ controlling the density of a preliminary billet, characterized in that, include: During the initial billet forming process, the powder bed is subjected to in-situ vibration and negative pressure. Based on the initial billet density analysis method described in any one of claims 1-7, the density of the initial billet is controlled in-situ by adjusting the in-situ vibration frequency, in-situ vibration amplitude, and negative pressure.

9. An apparatus for in-situ control of the density of a billet, characterized in that, include: The molding cylinder (1) and controller are provided. The molding cylinder (1) is provided with a material support mechanism. The top of the material support mechanism is provided with a filter screen (3) on which the powder is placed. The bottom of the filter screen (3) is connected to the negative pressure system (15) through an air pipe (9). The material support mechanism is fixedly connected to the vibrating end of the vibrator (7). The vibrator (7) is controlled to vibrate the material support mechanism. The bottom of the molding cylinder (1) is provided with an electrically controlled telescopic device (14) that drives the molding cylinder (1) to move up and down. The controller receives control commands obtained from the analysis of the initial billet density according to any one of claims 1-7, and controls the negative pressure system (15) to form a corresponding negative pressure and controls the vibrator (7) to drive the material support mechanism to vibrate with a corresponding amplitude and vibration frequency.

10. The apparatus for in-situ regulation of initial billet density according to claim 9, characterized in that, The material receiving mechanism consists of, from top to bottom, a filter screen (3), an upper piston plate (4), and a lower piston plate (5). The upper piston plate (4) and the lower piston plate (5) have interconnected airflow channels on opposite sides. The mesh of the filter screen (3) is connected to the airflow channel of the upper piston plate (4). The airflow channel of the lower piston plate (5) is connected to the air inlet of the air pipe (9) through an air pipe connector (8). The air outlet of the air pipe (9) is connected to the negative pressure system (15). The air pipe (9) is equipped with a control valve (10). The filter screen (3) is pressed and installed on the top surface of the upper piston plate (4) by the filter screen pressure plate (2); a primary sealing ring (6) is provided between the upper piston plate (4) and the lower piston plate (5) at the connection position with the side wall of the forming cylinder (1). The bottom of the forming cylinder (1) is detachably and fixedly connected to the connecting plate (12) through a secondary sealing ring (13); the bottom of the lower piston plate (5) is provided with a support plate for snapping onto the vibrating end of the vibrator (7), and a buffer pad (11) is provided between the bottom of the support plate and the top surface of the connecting plate (12).

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