Integrated supercritical foaming double-screw hydraulic precision injection molding system and method

Abstract

The invention relates to the technical field of high polymer material forming, and particularly discloses a double-screw hydraulic precision injection molding system and method integrating supercritical foaming. The double-screw plasticizing module comprises a motor body, a gearbox, a double-screw plasticizing unit, a mixing motor, an injection cylinder, a metering mixing unit, a nitrogen injection port and an injection nozzle; according to the double-screw plasticizing module, the mode that the motor body drives the double screws to rotate through the gearbox is adopted, the unique thread element combination is combined, efficient conveying, sufficient plasticizing and uniform mixing of materials are achieved, the stability of the materials in the conveying process is guaranteed through the deep groove conveying section, and the service life of the materials is prolonged. The helical tooth mixing block enhances the shearing and mixing effects of materials, the pressure reduction exhaust section effectively removes volatile gas and small molecular impurities in the materials, the purity and quality of melt are improved, a good foundation is laid for the subsequent foaming process, and foamed products with better performance can be prepared easily.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material forming, and particularly relates to a twin-screw hydraulic precision injection molding system and method integrated with supercritical foaming. Background Art

[0002] With the rapid development of modern industry, due to its excellent properties such as light weight, high strength, good corrosion resistance, etc., polymer materials have been widely used in many fields, especially in industries such as automobile manufacturing, high-end sports equipment, and electronic appliances. As a key link in realizing the manufacturing of polymer material products, polymer material forming technology is also constantly pursuing higher precision, better performance, and lower costs.

[0003] Among many polymer material forming methods, injection molding technology has become one of the most widely used forming methods due to its advantages such as high efficiency and the ability to mass-produce products with complex shapes. Through injection molding technology, polymer materials can be melted and injected into a mold, and after cooling and solidification, products with the required shapes can be obtained, meeting the requirements of different industries for the dimensional accuracy and appearance quality of products.

[0004] Traditional polymer material foaming molding technologies, such as the foaming method using chemical foaming agents, have many limitations. During the foaming process, the decomposition reaction of chemical foaming agents is difficult to precisely control, resulting in uneven weight distribution of foamed products. In some local areas, over-foaming may occur due to excessive decomposition of the foaming agent, causing the product weight to decrease too much; while in other areas, under-foaming may occur due to insufficient decomposition of the foaming agent, resulting in a heavier product weight. This phenomenon of uneven weight not only affects the overall performance of the product but may also cause problems such as stress concentration during the use of the product, reducing the service life of the product. Therefore, a twin-screw hydraulic precision injection molding system and method integrated with supercritical foaming are proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a twin-screw hydraulic precision injection molding system and method integrated with supercritical foaming to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A twin-screw hydraulic precision injection molding system integrated with supercritical foaming, comprising:

[0008] A twin-screw plasticizing module, the twin-screw plasticizing module includes a motor body, a gearbox, a twin-screw plasticizing unit, a mixing motor, an injection cylinder, a metering and mixing unit, a nitrogen injection port, and an injection nozzle. A twin-screw is arranged inside the twin-screw plasticizing unit, and a pin mixing section and a nitrogen injection interface are provided on the twin-screw of the twin-screw plasticizing module;

[0009] A supercritical fluid generation module, the supercritical fluid generation module includes a nitrogen booster pump and a heat exchanger, the pressure of the supercritical nitrogen output by the supercritical fluid generation module is ≥ 250 bar, and the temperature of the supercritical nitrogen output by the supercritical fluid generation module is 31.1 ± 0.5 °C;

[0010] A first injection unit and a second injection unit, both the first injection unit and the second injection unit include an independent closed-loop system composed of a hydraulic cylinder and a servo valve;

[0011] A laser interferometer for real-time monitoring of piston displacement;

[0012] A central controller, the central controller is used to execute the foaming control method;

[0013] A pressure relief valve, the pressure relief valve is connected to the central controller and is used to trigger pressure relief when the injection reaches 90% of the volume of the mold cavity.

[0014] Preferably, the screw element combination of the twin-screw plasticizing module includes:

[0015] A deep groove conveying section, the pitch of the deep groove conveying section is 1.5D;

[0016] An inclined tooth mixing block, the inclination angle of the inclined tooth mixing block is 45°;

[0017] A decompression exhaust section, the vacuum degree of the decompression exhaust section is ≤ -0.08 MPa.

[0018] Preferably, the hydraulic cylinder adopts a carbon fiber piston rod, and the axial stiffness of the carbon fiber piston rod is ≥ 200 GPa.

[0019] Preferably, the pressure relief valve is a high-frequency pulse valve, and the response time of the high-frequency pulse valve is ≤ 5 ms.

[0020] Through the setting of the above technical solutions, the twin-screw plasticizing module adopts the method of driving the twin-screw to rotate by the motor body 1 through the gearbox 2, combined with a unique screw element combination, including a deep groove conveying section with a pitch of 1.5D, an inclined tooth mixing block with an inclination angle of 45°, and a decompression exhaust section with a vacuum degree ≤ -0.08 MPa, realizing the efficient conveying, full plasticization and uniform mixing of the material. The deep groove conveying section ensures the stability of the material during the conveying process, the inclined tooth mixing block enhances the shearing and mixing effect of the material, and the decompression exhaust section effectively removes the volatile gases and small molecule impurities in the material, improving the purity and quality of the melt, laying a good foundation for the subsequent foaming process, and helping to prepare foamed products with better performance;

[0021] The pin mixing section and nitrogen injection interface provided on the twin-screw enable precise injection of supercritical nitrogen into the melt during the plasticization process, and through the rotational action of the twin-screw, uniform mixing of the supercritical nitrogen and the melt is achieved. By precisely controlling the solubility of the supercritical nitrogen in the melt to be 0.5% - 1.5% wt, the uniform distribution of bubbles during the foaming process can be ensured, thereby improving the mechanical properties, heat insulation properties, shock absorption properties, etc. of the foamed products;

[0022] Through the collaborative work of the nitrogen booster pump and the heat exchanger in the supercritical fluid generation module, the pressure and temperature of the output supercritical nitrogen can be precisely controlled, with its pressure ≥ 250 bar and the temperature stabilized at 31.1 ± 0.5 °C. This precise control ensures the stable performance of the supercritical nitrogen, provides a high-quality source of supercritical nitrogen for the twin-screw plasticization module, ensures a good mixing effect between the supercritical nitrogen and the melt, and is conducive to preparing foamed products with a uniform microporous structure.

[0023] A control method for twin-screw hydraulic precision injection molding integrated with supercritical foaming includes the following steps:

[0024] S1: Inject supercritical nitrogen into the twin-screw plasticization module through the nitrogen injection interface during the plasticization stage, and control the solubility of the supercritical nitrogen in the melt to be 0.5% - 1.5% wt;

[0025] S2: When the injection reaches 90% of the volume of the mold cavity, trigger the pressure relief valve for pressure relief, and the pressure relief rate of the pressure relief valve ≥ 50 bar / ms;

[0026] S3: Based on the feedback of the melt density, dynamically adjust the screw speed through the central controller, and the PID parameters are Kp = 0.8, Ki = 0.05, and Kd = 0.1.

[0027] Preferably, in the step S1, the pressure and temperature of the supercritical nitrogen are precisely controlled by the nitrogen booster pump and the heat exchanger in the supercritical fluid generation module.

[0028] Preferably, in the step S2, the piston displacement is monitored in real time by a laser interferometer, and the displacement data is fed back to the central controller. The central controller precisely controls the injection volume according to the displacement data, and triggers the pressure relief valve when the injection volume reaches 90% of the volume of the mold cavity.

[0029] Preferably, in the step S3, the melt density data is obtained in real time by a melt density sensor installed in the twin-screw plasticization module or the injection unit, and the data is fed back to the central controller, so that the central controller dynamically adjusts the screw speed according to the fed-back melt density data according to the PID parameters.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The twin-screw plasticizing module of the present invention adopts the method of driving the rotation of the twin screws by the motor body through a gearbox, combined with a unique combination of screw elements, including a deep-groove conveying section with a pitch of 1.5D, an inclined-tooth mixing block with an inclination angle of 45°, and a pressure-reducing exhaust section with a vacuum degree ≤ -0.08 MPa. It realizes the efficient conveying, full plasticization and uniform mixing of materials. The deep-groove conveying section ensures the stability of materials during the conveying process, the inclined-tooth mixing block enhances the shearing and mixing effects of materials, and the pressure-reducing exhaust section effectively removes volatile gases and small-molecule impurities in the materials, improving the purity and quality of the melt, laying a good foundation for the subsequent foaming process, and contributing to the preparation of foamed products with better performance;

[0032] At the same time, the pin mixing section and nitrogen injection interface provided on the twin screws enable the precise injection of supercritical nitrogen into the melt during the plasticization process, and through the rotation of the twin screws, the uniform mixing of supercritical nitrogen and the melt is achieved. By precisely controlling the solubility of supercritical nitrogen in the melt to be 0.5% - 1.5% wt, the uniform distribution of bubbles during the foaming process can be ensured, thereby improving the mechanical properties, heat insulation properties, shock absorption properties, etc. of the foamed products;

[0033] By the collaborative work of the nitrogen booster pump and the heat exchanger in the supercritical fluid generation module, the pressure and temperature of the output supercritical nitrogen can be precisely controlled, with the pressure ≥ 250 bar and the temperature stabilized at 31.1 ± 0.5 °C. This precise control ensures the stable performance of supercritical nitrogen, provides a high-quality source of supercritical nitrogen for the twin-screw plasticizing module, ensures a good mixing effect between supercritical nitrogen and the melt, and is conducive to the preparation of foamed products with a uniform microporous structure. Description of the Drawings

[0034] Figure 1 It is the structural diagram of the present invention.

[0035] In the figure: 1, motor body; 2, gearbox; 3, twin-screw plasticizing unit; 4, mixing motor; 5, injection cylinder; 6, metering and mixing unit; 7, nitrogen injection port; 8, injection nozzle. Detailed Embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] As Figure 1 shown, an integrated supercritical foaming twin-screw hydraulic precision injection molding system includes:

[0038] The twin-screw plasticizing module, the twin-screw plasticizing module includes a motor body 1, a gearbox 2, a twin-screw plasticizing unit 3, a mixing motor 4, an injection cylinder 5, a metering and mixing unit 6, a nitrogen injection port 7 and an injection nozzle 8. A twin-screw is arranged inside the twin-screw plasticizing unit 3, and a pin mixing section and a nitrogen injection interface are provided on the twin-screw of the twin-screw plasticizing module;

[0039] The supercritical fluid generation module, the supercritical fluid generation module includes a nitrogen booster pump and a heat exchanger. The supercritical nitrogen pressure output by the supercritical fluid generation module is ≥250 bar, and the supercritical nitrogen temperature output by the supercritical fluid generation module is 31.1 ± 0.5 °C;

[0040] The first injection unit and the second injection unit, both the first injection unit and the second injection unit include an independent closed-loop system composed of a hydraulic cylinder and a servo valve;

[0041] The laser interferometer is used to monitor the piston displacement in real time;

[0042] The central controller, the central controller is used to execute the foaming control method;

[0043] The pressure relief valve, the pressure relief valve is connected to the central controller and is used to trigger pressure relief when injecting glue to 90% of the volume of the mold cavity;

[0044] The present invention is further specifically described in detail. The screw element combination of the twin-screw plasticizing module includes:

[0045] The deep groove conveying section, the pitch of the deep groove conveying section is 1.5D;

[0046] The helical mixing block, the inclination angle of the helical mixing block is 45°;

[0047] The decompression and exhaust section, the vacuum degree of the decompression and exhaust section is ≤ -0.08 MPa.

[0048] The present invention is further specifically described in detail. The hydraulic cylinder adopts a carbon fiber piston rod, and the axial stiffness of the carbon fiber piston rod is ≥200 GPa; the pressure relief valve is a high-frequency pulse valve, and the response time of the high-frequency pulse valve is ≤ 5 ms;

[0049] As can be seen from the above, the motor body 1 drives the twin-screw in the twin-screw plasticizing unit 3 to rotate through the gearbox 2. The material enters the twin-screw plasticizing unit 3 from the feed port and is pushed forward along the screw groove under the rotation of the twin-screw. During the conveying process, the material is subjected to the shearing, extrusion and friction of the screw and is gradually melted and plasticized;

[0050] The pin mixing section and helical mixing blocks provided on the twin-screw further mix the material. The pin mixing section, through the relative movement between the pins and the screw, exerts strong shearing and stirring actions on the material, promoting the uniform mixing of the material. The helical mixing blocks are arranged at an inclination angle of 45°, which can change the flow direction and velocity distribution of the material, increase the relative movement and contact area between the materials, improve the mixing effect, and ensure the full dispersion and fusion of each component of the material;

[0051] During the plasticization process, through the nitrogen injection port 7 and the nitrogen injection interface on the twin-screw, the supercritical nitrogen provided by the supercritical fluid generation module is injected into the molten material. The supercritical nitrogen comes into full contact with the material in the melt. Due to the good solubility of the supercritical nitrogen, it can be evenly dispersed in the melt. At the same time, the rotational movement of the twin-screw further promotes the mixing of the supercritical nitrogen and the melt, making the solubility of the supercritical nitrogen in the melt reach 0.5% - 1.5% wt, preparing for the subsequent foaming process;

[0052] The material after mixing and supercritical nitrogen injection enters the decompression and exhaust section. The vacuum degree of the decompression and exhaust section is controlled at ≤ -0.08 MPa. In such a low-pressure environment, the volatile gases and small molecule impurities that may exist in the material will be extracted, thereby improving the purity of the melt and avoiding the adverse effects of these impurities on the quality of the product;

[0053] The well-plasticized melt is precisely metered through the metering and mixing unit 6 and then enters the injection cylinder 5. In the subsequent injection process, the injection cylinder 5 injects the melt into the mold cavity through the injection nozzle 8;

[0054] The supercritical fluid generation module is mainly composed of a nitrogen booster pump and a heat exchanger. The nitrogen booster pump boosts the nitrogen to make its pressure reach ≥ 250 bar to meet the pressure requirements of the supercritical state. The heat exchanger precisely controls the temperature of the boosted nitrogen, stabilizing the temperature of the supercritical nitrogen at 31.1 ± 0.5 °C. By precisely controlling the pressure and temperature of the nitrogen, the nitrogen reaches the supercritical state. This supercritical nitrogen has the diffusivity similar to that of a gas and the solubility similar to that of a liquid, and can better mix with the polymer material melt, providing a uniform gas source for the foaming process;

[0055] Both the first injection unit and the second injection unit consist of a hydraulic cylinder and a servo valve to form an independent closed-loop system. The hydraulic cylinder uses a carbon fiber piston rod with an axial stiffness ≥ 200 GPa. This high-stiffness piston rod can ensure the stability and accuracy of the hydraulic cylinder during movement, reduce the deformation of the piston rod, thereby improving the accuracy of the injection action. The servo valve precisely controls the oil inlet and oil return of the hydraulic cylinder according to the instructions of the central controller to achieve the precise movement of the hydraulic cylinder piston. During the injection process, the displacement of the piston is monitored in real time by a laser interferometer, and the displacement data is fed back to the central controller. The central controller precisely controls the injection volume according to the feedback displacement data to ensure the accurate volume of the injected melt;

[0056] The laser interferometer uses the interference principle of laser to monitor the displacement of the piston of the hydraulic cylinder in the injection unit in real time. The laser beam emitted by the laser interferometer irradiates the mirror on the surface of the piston, and the reflected light interferes with the reference light. By analyzing the change of the interference fringes, the displacement of the piston can be accurately calculated. The laser interferometer feeds back the monitored displacement data to the central controller in real time, providing a basis for the central controller to achieve precise injection control;

[0057] The central controller is the core control component of the entire system, responsible for executing the foaming control method. It receives information such as the piston displacement data from the laser interferometer and the melt density data from the melt density sensor, and controls each module according to these feedback information according to the preset control strategy;

[0058] The pressure relief valve is a high-frequency pulse valve with a response time ≤ 5 ms. The pressure relief valve is connected to the central controller. During the injection process, when the laser interferometer monitors that the injection volume reaches 90% of the cavity volume, the central controller will immediately send a trigger signal to the pressure relief valve. After receiving the signal, the pressure relief valve quickly opens for pressure relief, and the pressure relief rate ≥ 50 bar / ms. The rapid pressure relief process causes the pressure in the cavity to drop sharply, and the solubility of supercritical nitrogen in the melt decreases rapidly, so that it escapes from the melt to form bubbles, realizing the foaming process;

[0059] Through the setting of the above technical solutions, the twin-screw plasticizing module adopts the method of driving the twin-screw to rotate by the motor body 1 through the gearbox 2, combined with a unique combination of screw elements, including a deep groove conveying section with a pitch of 1.5D, a helical mixing block with an inclination angle of 45°, and a pressure reduction and exhaust section with a vacuum degree ≤ -0.08 MPa, realizing the efficient conveying, full plasticization and uniform mixing of materials. The deep groove conveying section ensures the stability of materials during the conveying process, the helical mixing block enhances the shearing and mixing effect of materials, and the pressure reduction and exhaust section effectively removes the volatile gases and small molecule impurities in the materials, improving the purity and quality of the melt, laying a good foundation for the subsequent foaming process, and helping to prepare foamed products with better performance;

[0060] The pin mixing section and nitrogen injection interface provided on the twin-screw enable the precise injection of supercritical nitrogen into the melt during the plasticization process. Through the rotation of the twin-screw, the uniform mixing of supercritical nitrogen and the melt is achieved. By precisely controlling the solubility of supercritical nitrogen in the melt to be 0.5% - 1.5% wt, the uniform distribution of bubbles during the foaming process can be ensured, thereby improving the mechanical properties, heat insulation properties, shock absorption properties, etc. of the foamed products;

[0061] Through the collaborative work of the nitrogen booster pump and the heat exchanger in the supercritical fluid generation module, the pressure and temperature of the output supercritical nitrogen can be precisely controlled, with the pressure ≥ 250 bar and the temperature stabilized at 31.1 ± 0.5 °C. This precise control ensures the stable performance of supercritical nitrogen, provides a high-quality source of supercritical nitrogen for the twin-screw plasticization module, ensures a good mixing effect between supercritical nitrogen and the melt, and is conducive to preparing foamed products with a uniform microporous structure.

[0062] A control method for twin-screw hydraulic precision injection molding integrated with supercritical foaming includes the following steps:

[0063] S1: Inject supercritical nitrogen into the twin-screw plasticization module through the nitrogen injection interface during the plasticization stage, and control the solubility of supercritical nitrogen in the melt to be 0.5% - 1.5% wt;

[0064] S2: When the injection reaches 90% of the cavity volume, trigger the pressure relief valve for pressure relief, and the pressure relief rate of the pressure relief valve ≥ 50 bar / ms;

[0065] S3: Based on the melt density feedback, dynamically adjust the screw speed through the central controller, with the PID parameters Kp = 0.8, Ki = 0.05, and Kd = 0.1.

[0066] The present invention is further specifically described in detail. In S1, the pressure and temperature of supercritical nitrogen are precisely controlled by the nitrogen booster pump and the heat exchanger in the supercritical fluid generation module; in S2, the piston displacement is monitored in real time through a laser interferometer, and the displacement data is fed back to the central controller. The central controller precisely controls the injection volume according to the displacement data, and triggers the pressure relief valve when the injection volume reaches 90% of the cavity volume; in S3, the melt density data is obtained in real time through the melt density sensor installed in the twin-screw plasticization module or the injection unit, and this data is fed back to the central controller, enabling the central controller to dynamically adjust the screw speed according to the feedback melt density data according to the PID parameters;

[0067] As described above, in the plasticization stage, the pressure and temperature of supercritical nitrogen are precisely controlled by the nitrogen booster pump and heat exchanger in the supercritical fluid generation module to ensure that the output supercritical nitrogen meets the requirements. Then, the supercritical nitrogen is injected into the twin-screw plasticization module through the nitrogen injection interface. The central controller controls the solubility of supercritical nitrogen in the melt to be 0.5% - 1.5% wt according to the preset process parameters. By precisely controlling the injection amount and injection conditions of supercritical nitrogen, the supercritical nitrogen can be evenly dissolved in the melt, providing a uniform gas distribution for the subsequent foaming process;

[0068] During the injection process, the laser interferometer monitors the displacement of the piston in real time and feeds the displacement data back to the central controller. The central controller calculates the current injection volume based on the displacement data and compares it with 90% of the volume of the mold cavity. When the injection volume reaches 90% of the mold cavity volume, the central controller immediately triggers the pressure relief valve to relieve pressure. This precise control method based on real-time displacement feedback can ensure the accuracy of the injection volume and avoid the impact of excessive or insufficient injection volume on the product quality;

[0069] During the foaming process, the melt density data is obtained in real time by the melt density sensor installed in the twin-screw plasticization module or injection unit and fed back to the central controller. Since the density of the melt changes with the formation and growth of bubbles during the foaming process, the central controller dynamically adjusts the screw speed according to the feedback melt density data according to the PID parameters (Kp = 0.8, Ki = 0.05, and Kd = 0.1). The proportional parameter Kp quickly adjusts the screw speed according to the current error (the difference between the set density and the actual density). The integral parameter Ki integrates the error to eliminate the steady-state error. The derivative parameter Kd predicts the change trend of the error according to the change rate of the error and adjusts the screw speed in advance, thereby achieving precise control of the melt density and ensuring the stability of the product quality.

[0070] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An integrated twin-screw hydraulic precision injection molding system with supercritical foaming, characterized in that, Comprising: A twin-screw plasticizing module, the twin-screw plasticizing module includes a motor body, a gearbox, a twin-screw plasticizing unit, a mixing motor, an injection cylinder, a metering and mixing unit, a nitrogen injection port and an injection nozzle. Inside the twin-screw plasticizing unit, there is a twin-screw. On the twin-screw of the twin-screw plasticizing module, there are a pin mixing section and a nitrogen injection interface; A supercritical fluid generating module, the supercritical fluid generating module includes a nitrogen booster pump and a heat exchanger. The supercritical nitrogen output by the supercritical fluid generating module has a pressure ≥ 250 bar, and the supercritical nitrogen output by the supercritical fluid generating module has a temperature of 31.1 ± 0.5 °C; A first injection unit and a second injection unit, both the first injection unit and the second injection unit include an independent closed-loop system composed of a hydraulic cylinder and a servo valve; A laser interferometer for real-time monitoring of piston displacement; A central controller, the central controller is used to execute the foaming control method; A pressure relief valve, the pressure relief valve is connected to the central controller and is used to trigger pressure relief when injecting glue to 90% of the volume of the mold cavity.

2. The integrated twin-screw hydraulic precision injection molding system with supercritical foaming according to claim 1, characterized in that: The screw element combination of the twin-screw plasticizing module includes: A deep groove conveying section, the pitch of the deep groove conveying section is 1.5D; An inclined tooth mixing block, the inclination angle of the inclined tooth mixing block is 45°; A pressure reduction and exhaust section, the vacuum degree of the pressure reduction and exhaust section ≤ -0.08 MPa.

3. The twin-screw hydraulic precision injection molding system integrated with supercritical foaming according to claim 1, wherein: The hydraulic cylinder uses a carbon fiber piston rod, and the axial stiffness of the carbon fiber piston rod ≥ 200 GPa.

4. An integrated supercritical foaming twin-screw hydraulic precision injection molding system according to claim 1, characterized in that: The pressure relief valve is a high-frequency pulse valve, and the response time of the high-frequency pulse valve ≤ 5 ms.

5. A control method for twin-screw hydraulic precision injection molding integrated with supercritical foaming, characterized in that, Including the following steps: S1: Inject supercritical nitrogen into the twin-screw plasticizing module through the nitrogen injection interface during the plasticizing stage, and control the solubility of the supercritical nitrogen in the melt to be 0.5% - 1.5% wt; S2: When injecting glue to 90% of the volume of the mold cavity, trigger the pressure relief valve to relieve pressure, and the pressure relief rate of the pressure relief valve ≥ 50 bar / ms; S3: Based on the melt density feedback, dynamically adjust the screw speed through the central controller, and the PID parameters are Kp = 0.8, Ki = 0.05, and Kd = 0.

1.

6. A control method for an integrated supercritical foaming twin-screw hydraulic precision injection molding according to claim 5, characterized in that: In the S1, the pressure and temperature of the supercritical nitrogen are precisely controlled by the nitrogen booster pump and the heat exchanger in the supercritical fluid generating module.

7. A control method for an integrated supercritical foaming twin-screw hydraulic precision injection molding according to claim 5, characterized in that: In the S2, the piston displacement is monitored in real time by the laser interferometer, and the displacement data is fed back to the central controller. The central controller precisely controls the injection volume according to the displacement data, and triggers the pressure relief valve when the injection volume reaches 90% of the volume of the mold cavity.

8. A control method for an integrated supercritical foaming twin-screw hydraulic precision injection molding according to claim 5, characterized in that: In the S3, the melt density data is obtained in real time through the melt density sensor installed in the twin-screw plasticizing module or the injection unit, and the data is fed back to the central controller, so that the central controller dynamically adjusts the screw speed according to the fed-back melt density data according to the PID parameters.

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