Injection viscosity real-time regulation method and system based on high-low frequency vibration coupling rheological model

Abstract

The present application relates to the technical field of high polymer material precision injection molding, and discloses an injection viscosity real-time regulation method and system based on a high-low frequency vibration coupling rheological model, which realizes online measurement and dynamic adjustment of polymer melt viscosity by simultaneously applying adjustable high-frequency and low-frequency vibration in the injection filling stage, combining an embedded rheological mathematical model and a real-time feedback control algorithm; the system adopts a multimode sensor to collect injection process parameters in real time, calculates viscosity based on the coupling rheological model and compares it with a target value, generates a control instruction by using a model predictive control or a PID+adaptive filtering control strategy, adjusts injection molding machine parameters and vibration device output, and forms a closed-loop regulation; the method effectively reduces melt viscosity, improves filling fluidity, reduces injection pressure and energy consumption, and improves the quality and molding efficiency of injection molded parts.

Description

Technical Field

[0001] This invention relates to the field of precision injection molding technology for polymer materials, specifically to a method and system for real-time control of injection molding viscosity based on a high- and low-frequency vibration coupled rheological model. Background Technology

[0002] Specialty engineering plastics such as polyphenylene sulfide (PPS) and polyetheretherketone (PEEK) are widely used in the manufacture of precision structural components in the automotive, electronics, and aerospace industries due to their excellent high-temperature resistance, corrosion resistance, and high mechanical properties. However, these materials typically have extremely high melt viscosity, and their fluidity deteriorates further after being filled with glass or carbon fibers. This leads to a series of problems during injection molding of microchannels or thin-walled structures, including incomplete filling, low weld line strength, high internal stress in the product, and difficulty in controlling dimensional accuracy.

[0003] Vibration-assisted injection molding technology is one of the effective means to improve the above-mentioned problems. Currently, this technology is mainly divided into two categories: one is high-frequency ultrasonic vibration-assisted molding, which uses vibrations at frequencies in the tens of hertz range and amplitudes in the micrometer range to promote the deentanglement of molecular chains through acoustic flow and local thermal effects, thereby reducing the apparent viscosity of the melt to a certain extent; the other is low-frequency mechanical vibration-assisted molding, which uses vibrations at frequencies in the tens of hertz range and amplitudes in the millimeters range to apply macroscopic periodic shearing to the melt, using the shear thinning effect to improve fluidity. However, both of these single-mode vibrations have inherent limitations. For high-frequency ultrasonic vibration, its energy decays extremely quickly in viscoelastic melts, and its effective range is limited to the near-field region, making it difficult to achieve global uniform control for large or complex cavities; at the same time, its activation ability for rigid molecular chains is limited, resulting in a bottleneck in viscosity reduction. For low-frequency mechanical vibration, although it can effectively reconstruct the macroscopic flow field, it is difficult to intervene in the molecular-scale chain segment movement, resulting in insufficient ability to reduce the intrinsic viscosity of the material; in addition, excessively high mechanical vibration parameters can cause severe fluctuations in the flow field, increasing equipment wear and process instability.

[0004] More importantly, existing vibration-assisted injection molding processes are mostly "open-loop" controlled, meaning vibration parameters are preset before production and kept constant during injection. This approach cannot handle real-time changes in melt viscosity caused by material batch differences, temperature fluctuations, and mold conditions, resulting in poor consistency in product quality across different production cycles or at different times within the same cycle, failing to meet the mass production requirements of high-reliability precision parts. Therefore, developing a method and system that can deeply integrate the advantages of high- and low-frequency vibrations and accurately control viscosity in real time based on the actual melt state is key to overcoming the bottleneck in precision molding technology for high-viscosity specialty engineering plastics. Summary of the Invention

[0005] To address the inherent limitations of existing technologies, such as the inability to adjust for the actual state of the melt due to the two single-mode vibrations, this invention provides a method and system for real-time control of injection molding viscosity based on a high- and low-frequency vibration coupled rheological model. The technical solution is as follows:

[0006] A method for real-time control of injection molding viscosity based on a high- and low-frequency vibration coupled rheological model includes the following steps:

[0007] Step 1: Real-time monitoring of process signals during the injection molding process, including injection speed, ultrasonic vibration parameters, mechanical vibration parameters, and melt pressure at at least two points in the mold runner;

[0008] Step 2: Input the injection speed, ultrasonic vibration parameters and mechanical vibration parameters into a preset high- and low-frequency vibration coupled rheological model to calculate the desired viscosity of the melt;

[0009] Step 3: Calculate the pressure difference based on the melt pressure at the at least two points, and obtain the actual viscosity characterization value of the melt based on the pressure difference; calculate the viscosity deviation between the actual viscosity characterization value and the expected viscosity.

[0010] Step 4: Based on the viscosity deviation, generate control commands for adjusting ultrasonic vibration parameters and / or mechanical vibration parameters;

[0011] Step 5: Adjust the composite vibration field acting on the polymer melt in real time according to the control command.

[0012] Furthermore, the high- and low-frequency vibration coupled rheological model is as follows:

[0013] ,

[0014] in, The desired melt dynamic viscosity; The energy density of ultrasonic vibration, and the ultrasonic frequency. and amplitude Related; The apparent shear rate is related to the injection speed and the flow channel geometry. , These are the mechanical vibration frequency and amplitude, respectively. For flow channel characteristic scale; These are the model parameters.

[0015] Furthermore, the formula for calculating the ultrasonic vibration energy density is as follows:

[0016] ,

[0017] in, For material density, The ultrasonic velocity in the material, The area affected by the ultrasound. is the sound absorption coefficient.

[0018] Furthermore, the formula for calculating the actual viscosity characterization value is as follows:

[0019] ,

[0020] in, This is the actual viscosity characterization value; The length of the narrow slit; The width of the narrow slit; The thickness of the narrow slit; The amount of polymer leaving the slit per unit time; The pressure difference between the two ends of the narrow slit.

[0021] Furthermore, the method employs a PID controller, a fuzzy controller, or a model predictive controller to generate control commands based on the viscosity deviation. These control commands include adjustments to the ultrasonic vibration parameters and the mechanical vibration parameters.

[0022] A real-time injection molding viscosity control system based on a high- and low-frequency vibration coupled rheological model, used in the above-described method, includes: a hopper, a screw, a first pressure sensor, an ultrasonic vibration block, an ultrasonic vibration device, a second pressure sensor, a mold body, a mold cavity, a mechanical vibration device, a mechanical vibration block, a flow channel, a barrel, a display and data acquisition module, and a central processing module.

[0023] The hopper is located at the top of the barrel and is used to store polymer particles to be processed. The screw is located inside the barrel and is used to transport, melt, and inject the polymer. The barrel is connected to the flow channel and is used to inject the polymer melt into the mold cavity. The first pressure sensor and the second pressure sensor are respectively located upstream and downstream of the flow channel and are used to detect the flow pressure of the polymer melt in real time. The ultrasonic vibration block and the mechanical vibration block are respectively located at the upper and lower ends of the flow channel wall and are respectively connected to the ultrasonic vibration device and the mechanical vibration device to apply high-frequency vibration and low-frequency vibration to the flowing polymer melt. The end of the flow channel is connected to the mold cavity. The mold cavity is located inside the mold body. The display and data acquisition module is connected to the first pressure sensor and the second pressure sensor and is used to record, display, and store the injection molding process parameters. The central processing module is connected to the ultrasonic vibration device, the mechanical vibration device, and the display and data acquisition module and is used to receive various detection signals and calculate the deviation between the target viscosity and the actual viscosity under the current working conditions based on a preset high- and low-frequency vibration coupled rheological model.

[0024] Furthermore, the ultrasonic vibration device includes an ultrasonic generator, an ultrasonic transducer, and an ultrasonic amplitude transformer; the ultrasonic generator is connected to the ultrasonic transducer and is used to generate high-frequency electrical signals; the ultrasonic transducer is connected to the ultrasonic amplitude transformer and is used to convert the electrical signals into mechanical vibrations; the ultrasonic amplitude transformer is connected to an ultrasonic vibration block and is used to amplify the vibration displacement.

[0025] Furthermore, the mechanical vibration device includes a driver and a transmission mechanism. The driver is connected to the transmission mechanism to provide power and generate periodic low-frequency vibration. The transmission mechanism is connected to the mechanical vibration block to transmit the vibration.

[0026] Furthermore, the central processing module is integrated into the injection molding machine controller or is a stand-alone industrial computer.

[0027] Beneficial effects

[0028] 1. This invention employs a composite vibration field combining high-frequency ultrasound and low-frequency mechanics to achieve synergistic activation of microscopic molecular chains and reconstruction of macroscopic flow field shearing. The viscosity reduction effect on high-viscosity, high-rigidity chain polymers such as PPS is superior to that of a single vibration mode, providing a wider process window for precision molding.

[0029] 2. Through closed-loop control of model prediction, online detection and feedback regulation, it can compensate for viscosity changes caused by material batch differences, temperature fluctuations and other factors in real time, ensuring the stability of melt viscosity and flow state during the filling stage, thereby significantly improving the dimensional accuracy, weight consistency and mechanical property uniformity of the product.

[0030] 3. This invention uses a coupled rheological model that reveals the physical mechanism as the core for prediction, which makes the control forward-looking and adaptive. Compared with simply relying on PID feedback, it has a faster response and smaller overshoot, and is especially suitable for fast and transient injection molding filling processes.

[0031] 4. The system of the present invention can be modularly integrated into existing precision injection molding machines. By modifying the runner or mold to apply vibration, it is not only applicable to PPS, but its model parameters can also be extended to vibration-assisted precision molding of other special engineering plastics or general plastics after calibration. Attached Figure Description

[0032] Figure 1 The flowchart shows a real-time control method for injection molding viscosity based on a high- and low-frequency vibration coupled rheological model.

[0033] Figure 2 This is a structural diagram of an injection molding viscosity real-time control system based on a high- and low-frequency vibration coupled rheological model.

[0034] Figure 3 A schematic diagram of the integrated structure of an ultrasonic vibration device and a mechanical vibration device;

[0035] Figure 4 A schematic diagram of the structure applied to the mold flow channel and the composite vibration field;

[0036] Figure 5 A schematic diagram illustrating the principle of flow channel pressure detection and viscosity characterization;

[0037] Figure 6 This is a schematic diagram of the pressure difference in the melt flow channel under different vibration modes.

[0038] The meanings of the labels in the figures are as follows: 1-Hopper, 2-Screw, 3-First pressure sensor, 4-Ultrasonic vibrating block, 5-Ultrasonic vibration device, 6-Second pressure sensor, 7-Mold body, 8-Mold cavity, 9-Mechanical vibration device, 10-Mechanical vibrating block, 11-Flow channel, 12-Barrel, 13-Display and data acquisition module, 14-Central processing module, 15-Ultrasonic amplitude transformer, 16-Ultrasonic transducer, 17-Ultrasonic generator, 18-Transmission mechanism, 19-Driver, 20-Polymer melt. Detailed Implementation

[0039] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0040] like Figure 1 As shown, the real-time injection molding viscosity control method based on a high- and low-frequency vibration coupled rheological model of the present invention includes the following steps:

[0041] Step S1: Real-time detection of process signals. During the injection molding process, the advance speed of the injection screw, the melt pressure signal at key points of the mold runner, and the parameters (frequency, amplitude) of the currently applied ultrasonic and mechanical vibrations are collected in real time.

[0042] Step S2: Calculation of desired viscosity based on coupled rheological model. Input the injection speed and current vibration parameters collected in step S1 into the preset high and low frequency vibration coupled rheological model to calculate the desired viscosity or model-predicted viscosity of the melt under the current process conditions in real time.

[0043] The high- and low-frequency vibration coupled rheological model is a generalized constitutive equation, and its expression is as follows:

[0044] ,

[0045] in, The model predicts the dynamic viscosity of the melt. The energy density of ultrasonic vibration. With ultrasonic frequency ,amplitude Related; The apparent shear rate is determined by the injection speed and the flow channel geometry. , These are the mechanical vibration frequency and amplitude, respectively. For flow channel characteristic scale; For material density, The ultrasonic velocity in the material, The area affected by the ultrasound. The sound absorption coefficient; These are the parameters for model fitting. The model is also coupled with ultrasonic energy. The softening effect on intrinsic material parameters and the effect of mechanical vibration on effective shear rate The augmentation effect.

[0046] Step S3: Actual viscosity detection and deviation generation. Based on the pressure sensor signals from two different locations on the flow channel collected in Step S1, the pressure difference is calculated. Based on the principle of the narrow-slit flow model, under stable process conditions, It is positively correlated with the apparent viscosity of the melt passing through this flow channel section. Through calibration curves or theoretical conversion, the real-time monitored... Converted to actual viscosity characterization values ​​that reflect melt flow resistance Calculate the deviation between the actual viscosity characterization value and the expected viscosity obtained in step S2. .

[0047] Step S4: Generation of vibration parameter control commands. The viscosity deviation obtained in step S3 is then used... Input controller (such as PID controller, fuzzy controller, etc.). The controller is based on the deviation. The magnitude and direction of the ultrasonic vibration are determined according to a preset control law, generating control commands for adjusting the ultrasonic vibration generator and the mechanical vibration actuator. These control commands include controls for the ultrasonic amplitude. ,frequency Mechanical vibration frequency ,amplitude The adjustment amount.

[0048] Step S5: Real-time adjustment of the composite vibration field. The ultrasonic vibration generator and the mechanical vibration actuator receive and execute the control commands generated in step S4, dynamically adjusting their outputs to change the composite vibration field parameters acting on the polymer melt in the mold flow channel, thereby achieving closed-loop regulation of the melt viscosity.

[0049] Repeat the above steps to achieve closed-loop dynamic control of the entire injection molding process.

[0050] like Figure 2As shown, the real-time injection molding viscosity control system based on a high- and low-frequency vibration coupled rheological model of the present invention includes: a hopper 1, a screw 2, a first pressure sensor 3, an ultrasonic vibration block 4, an ultrasonic vibration device 5, a second pressure sensor 6, a mold body 7, a mold cavity 8, a mechanical vibration device 9, a mechanical vibration block 10, a flow channel 11, a barrel 12, a display and data acquisition module 13, and a central processing module 14.

[0051] The hopper 1 is used to store polymer particles to be processed; the screw 2 is located inside the barrel 12 and is used to transport, melt and inject the polymer; the whole is connected to the flow channel 11 and is used to inject the polymer melt 20 into the mold cavity 8.

[0052] The ultrasonic vibration device 5 and the mechanical vibration device 9 are located near the flow channel 11 and are respectively connected to the ultrasonic vibration block 4 and the mechanical vibration block 10, which are used to apply high-frequency vibration and low-frequency vibration to the flowing polymer melt 20.

[0053] The first pressure sensor 3 and the second pressure sensor 6 are respectively located upstream and downstream of the vibration zone to detect the flow pressure of the polymer melt 20 in real time.

[0054] The central processing module 14 receives various detection signals and calculates the deviation between the target viscosity and the actual viscosity under the current operating conditions based on a preset high- and low-frequency vibration coupled rheological model. The controller can be a fuzzy controller, a model predictive controller (MPC), or a neural network adaptive controller to generate vibration parameter adjustment commands in real time according to the viscosity deviation.

[0055] The display and data acquisition module 13 is used to record, display and store injection molding process parameters.

[0056] like Figure 3 As shown, the ultrasonic vibration device 5 includes an ultrasonic generator 17, an ultrasonic transducer 16, and an ultrasonic amplitude transformer 15. The ultrasonic generator 17 is used to generate high-frequency electrical signals; the ultrasonic transducer 16 converts the electrical signals into mechanical vibrations; and the ultrasonic amplitude transformer 15 is used to amplify the vibration displacement and transmit it to the ultrasonic vibration block 4.

[0057] The mechanical vibration device 9 includes a driver 19 and a transmission mechanism 18. The driver 19 is used to provide power to generate periodic low-frequency vibration; the transmission mechanism 18 is used to transmit the vibration to the mechanical vibration block 10.

[0058] like Figure 4As shown, the ultrasonic vibrating block 4 and the mechanical vibrating block 10 are integrated on the upper and lower sides of the flow channel 11 wall, respectively. The ultrasonic vibration device 5 generates high-frequency vibrations in the range of 20~40kHz through the ultrasonic transducer 16, which are amplified by the ultrasonic amplitude transformer 15 and act on the wall of the flow channel 11, so that the flowing polymer melt 20 is subjected to periodic ultrasonic excitation. The mechanical vibration device 9 generates low-frequency mechanical vibrations in the range of 10~300Hz through an eccentric wheel, an electromagnetic exciter, or a servo drive mechanism. Among them, the high-frequency ultrasonic vibration is used to improve the motion state of the melt molecular chains, while the low-frequency mechanical vibration is used to enhance the overall flow shear, and the two together form a composite vibration field. Preferably, the ultrasonic amplitude range is 2~30μm, and the mechanical vibration amplitude range is 0.01~1mm.

[0059] like Figure 5 As shown, the first pressure sensor 3 and the second pressure sensor 6 are respectively disposed at both ends of the flow channel 11 region. When the polymer melt 20 flows through the narrow slit flow channel 11, its pressure loss corresponds to the apparent viscosity of the melt. According to the slit flow theory, the apparent viscosity of the melt can be established in combination with the flow channel width, thickness, and length parameters as follows:

[0060] ,

[0061] Where L is the slit length; w is the slit width; h is the slit thickness; Q is the polymer volumetric flow rate per unit time through the channel; and ΔP is the pressure difference between the two ends of the slit. In practical applications, the mapping relationship between the pressure difference and the actual viscosity can be established through experimental calibration, thereby enabling real-time online detection of melt viscosity.

[0062] like Figure 6 As shown, the curves of the change in melt flow channel pressure difference under different vibration modes are: Curve A represents the flow channel pressure difference when no vibration is applied; Curve B represents the pressure difference when only ultrasonic vibration is applied; Curve C represents the pressure difference when only mechanical vibration is applied; and Curve D represents the pressure difference when high and low frequency composite vibration is applied simultaneously.

[0063] The results show that under the combined vibration mode, the pressure difference in the melt channel is significantly reduced, indicating that the melt flow resistance is reduced and the apparent viscosity decreases.

[0064] Furthermore, compared to single ultrasonic vibration or single mechanical vibration, the composite vibration mode has a better viscosity reduction effect and a more stable flow state.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for real-time control of injection molding viscosity based on a high- and low-frequency vibration coupled rheological model, characterized in that, Includes the following steps: Step 1: Real-time monitoring of process signals during the injection molding process, including injection speed, ultrasonic vibration parameters, mechanical vibration parameters, and melt pressure at at least two points in the mold runner; Step 2: Input the injection speed, ultrasonic vibration parameters and mechanical vibration parameters into a preset high- and low-frequency vibration coupled rheological model to calculate the desired viscosity of the melt; Step 3: Calculate the pressure difference based on the melt pressure at the at least two points, and obtain the actual viscosity characterization value of the melt based on the pressure difference; Calculate the viscosity deviation between the actual viscosity characterization value and the expected viscosity; Step 4: Based on the viscosity deviation, generate control commands for adjusting ultrasonic vibration parameters and / or mechanical vibration parameters; Step 5: Adjust the composite vibration field acting on the polymer melt in real time according to the control command.

2. The real-time injection molding viscosity control method based on a high- and low-frequency vibration coupled rheological model as described in claim 1, characterized in that: The high- and low-frequency vibration coupled rheological model is as follows: ， in, The desired melt dynamic viscosity; The energy density of ultrasonic vibration, and the ultrasonic frequency. and amplitude Related; The apparent shear rate is related to the injection speed and the flow channel geometry. , These are the mechanical vibration frequency and amplitude, respectively. For flow channel characteristic scale; These are the model parameters.

3. The real-time injection molding viscosity control method based on a high- and low-frequency vibration coupled rheological model as described in claim 2, characterized in that: The formula for calculating the ultrasonic vibration energy density is as follows: ， in, For material density, The ultrasonic velocity in the material, The area affected by the ultrasound. is the sound absorption coefficient.

4. The real-time injection molding viscosity control method based on a high- and low-frequency vibration coupled rheological model as described in claim 1, characterized in that: The formula for calculating the actual viscosity characterization value is as follows: ， in, This is the actual viscosity characterization value; The length of the narrow slit; The width of the narrow slit; The thickness of the narrow slit; The amount of polymer leaving the slit per unit time; The pressure difference between the two ends of the narrow slit.

5. The real-time injection molding viscosity control method based on a high- and low-frequency vibration coupled rheological model as described in claim 1, characterized in that: The method employs a PID controller, a fuzzy controller, or a model predictive controller to generate control commands based on the viscosity deviation. These control commands include adjustments to the ultrasonic vibration parameters and the mechanical vibration parameters.

6. A real-time injection molding viscosity control system based on a high- and low-frequency vibration coupled rheological model, characterized in that, The method as described in any one of claims 1 to 5 includes: a hopper (1), a screw (2), a first pressure sensor (3), an ultrasonic vibration block (4), an ultrasonic vibration device (5), a second pressure sensor (6), a mold body (7), a mold cavity (8), a mechanical vibration device (9), a mechanical vibration block (10), a flow channel (11), a barrel (12), a display and data acquisition module (13), and a central processing module (14). The hopper (1) is located at the top of the barrel (12) and is used to store polymer particles to be processed; the screw (2) is located inside the barrel (12) and is used to transport, melt and inject the polymer; the barrel (12) is connected to the flow channel (11) and is used to inject the polymer melt (20) into the mold cavity (8); the first pressure sensor (3) and the second pressure sensor (6) are respectively located upstream and downstream of the flow channel (11) and are used to detect the flow pressure of the polymer melt (20) in real time; the ultrasonic vibration block (4) and the mechanical vibration block (10) are respectively located at the upper and lower ends of the wall of the flow channel (11) and are respectively connected to the ultrasonic vibration device (5) and the mechanical vibration device. The flow channel (11) is used to apply high-frequency and low-frequency vibrations to the flowing polymer melt (20); the end of the flow channel (11) is connected to the mold cavity (8); the mold cavity (8) is set inside the mold body (7); the display and data acquisition module (13) is connected to the first pressure sensor (3) and the second pressure sensor (6) for recording, displaying and storing injection molding process parameters; the central processing module (14) is connected to the ultrasonic vibration device (5), the mechanical vibration device (9) and the display and data acquisition module (13) for receiving various detection signals and calculating the deviation between the target viscosity and the actual viscosity under the current working condition based on the preset high and low frequency vibration coupled rheological model.

7. The real-time injection molding viscosity control system based on a high- and low-frequency vibration coupled rheological model as described in claim 6, characterized in that: The ultrasonic vibration device (5) includes an ultrasonic generator (17), an ultrasonic transducer (16), and an ultrasonic amplitude transformer (15); the ultrasonic generator (17) is connected to the ultrasonic transducer (16) and is used to generate high-frequency electrical signals; the ultrasonic transducer (16) is connected to the ultrasonic amplitude transformer (15) and is used to convert electrical signals into mechanical vibrations; the ultrasonic amplitude transformer (15) is connected to the ultrasonic vibration block (4) and is used to amplify the vibration displacement.

8. The real-time injection molding viscosity control system based on a high- and low-frequency vibration coupled rheological model as described in claim 6, characterized in that: The mechanical vibration device (9) includes a driver (19) and a transmission mechanism (18). The driver (19) is connected to the transmission mechanism (18) to provide power and generate periodic low-frequency vibration. The transmission mechanism (18) is connected to the mechanical vibration block (10) to transmit vibration.

9. The real-time injection molding viscosity control system based on a high- and low-frequency vibration coupled rheological model as described in claim 6, characterized in that: The central processing module (14) is integrated into the injection molding machine controller or is a stand-alone industrial computer.

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