Injection molding control method for automobile decorating part
By coordinating the control of injection pressure and cooling rate, identifying high-incidence areas of warpage, and setting differentiated cooling rate benchmark values, the problem of warpage deformation during the injection molding process of automotive trim parts was solved, achieving precise release of internal stress and uniform thermal shrinkage, and improving the stability of batch production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-02
- Publication Date
- 2026-03-31
AI Technical Summary
During the injection molding process, automotive trim parts warp due to uneven release of internal stress and excessive differences in thermal shrinkage. In existing technologies, pressure control and cooling control are independent of each other, which cannot effectively solve the warping problem.
By coordinating the control of injection pressure and cooling rate, high-risk warpage areas are identified, differentiated cooling rate benchmark values are set, and a linkage between injection pressure compensation value and cooling rate correction coefficient is established to achieve coordinated control of the entire injection, holding pressure, and cooling process.
This addresses the warping problem at its root, allowing for precise matching and release of internal stress, improving the uniformity of thermal shrinkage, and enhancing batch production stability.
Smart Images
Figure CN121756538A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of automotive parts injection molding technology, and more specifically, relates to an injection molding control method for automotive decorative parts. Background Technology
[0002] As a core component of automotive interiors, the molding quality of automotive trim parts directly affects the overall quality of the vehicle and the user experience. With the development of the automotive industry, consumers have placed higher demands on the appearance flatness, dimensional stability, and assembly precision of automotive trim parts, especially for complex structural trim parts (such as those with micro-textures, snap-fit connections, or uneven wall thickness), which are prone to quality problems such as warping, uneven shrinkage, and surface defects during injection molding. Summary of the Invention
[0003] The purpose of this invention is to provide an injection molding control method for automotive trim parts, which solves the quality problem of warping and deformation caused by uneven internal stress release and excessive thermal shrinkage by synergistically controlling injection pressure and cooling rate.
[0004] To achieve the above objectives, the technical solution adopted by the present invention is: to provide an injection molding control method for automotive decorative parts, comprising the following steps: S1. During the injection molding stage, collect flow state data of plastic melt in each molding area of the mold, calculate the injection pressure compensation value of each area, and mark the warping high-incidence areas where the injection pressure compensation value exceeds the preset compensation threshold. S2. Based on the molding requirements of automotive trim parts, preset the cooling rate benchmark value for each molding area of the mold, and set a differentiated cooling rate benchmark value that is different from the normal area for the warping high-incidence area marked S1. S3. Based on the injection pressure compensation value obtained in S1, calculate the cooling rate correction coefficient for high warpage areas and normal areas, and establish the linkage between the injection pressure compensation value and the cooling rate correction coefficient. S4. Adjust the coolant flow rate in each area of the mold according to the cooling rate correction coefficient to achieve linkage control between injection pressure compensation and cooling rate until the injection cooling stage is completed. S5. After injection molding, the warpage of the automotive trim parts is detected. If the warpage exceeds the preset acceptable range, the preset compensation threshold and the differential cooling rate benchmark value are corrected based on the warpage detection results.
[0005] In one possible implementation, step S1 specifically includes: S11. Deploy multi-type sensor arrays, including arranging pressure pulsation sensors, melt flow rate sensors and shear stress sensors in the injection cylinder, nozzle and each molding area of the mold of the injection molding machine. S12. After the injection stage is started, the pressure pulsation signal, melt flow rate data and shear stress distribution parameters are collected synchronously by the sensor array at a preset sampling frequency to form a data set of the flow state of each molding area. S13. Input the flow state dataset into the preset calculation model, calculate the flow resistance coefficient of each region, and then calculate the injection pressure compensation value of each region based on the flow resistance coefficient and the injection pressure reference value. S14. Compare the injection pressure compensation value of each region with the preset compensation threshold, mark the regions that exceed the threshold with high warping incidence, and generate a distribution map of high warping incidence regions.
[0006] In one possible implementation, before step S11, injection molding simulation software is used to perform melt flow and internal stress simulation analysis on the three-dimensional model of the automotive trim part, pre-identify potential high-risk warping areas, and formulate a sensor densification arrangement scheme based on the identification results.
[0007] In one possible implementation, step S3 specifically includes: S31. Determine the reference values for material viscosity, zone wall thickness, and injection pressure based on the characteristic parameters of the injection molding material; S32. Calculate the injection pressure compensation ratio based on the injection pressure compensation value, and calculate the material viscosity influence factor and regional wall thickness deviation rate by combining the real-time value of material viscosity and the measured value of wall thickness. S33. Introduce dynamic weighting factors and calculate the dynamic weighting factors of each region by weighting the material viscosity influence factor, the regional wall thickness deviation rate and the injection pressure compensation ratio. S34. Based on the dynamic weighting factor and the preset benchmark correction coefficient, calculate the cooling rate correction coefficient for each region and generate a correction coefficient allocation table.
[0008] In one possible implementation, the dynamic weighting factor is calculated using the following formula: ;in, As a dynamic weighting factor, , , For preset weighting coefficients, This is a factor affecting the viscosity of materials. This refers to the regional wall thickness deviation rate. This is the injection pressure compensation ratio.
[0009] In one possible implementation, the material viscosity influence factor =(Actual melt viscosity - Standard melt viscosity) / Standard melt viscosity. The actual melt viscosity is calculated based on the characteristic frequency components of the pressure pulsation signal during the injection stage, and the standard melt viscosity is the calibrated viscosity value of the injection molding material for automotive trim parts.
[0010] In one possible implementation, calculating the material viscosity influence factor in step S32 includes: S321. Extract the characteristic frequency components of the pressure pulsation signal during the injection stage, and calculate the real-time viscosity of the melt using the frequency-viscosity correlation formula. S322. Calculate the difference between the real-time viscosity of the melt and the reference viscosity value of the material, and then compare the difference with the reference viscosity value of the material to obtain the material viscosity influence factor.
[0011] In one possible implementation, step S4 specifically includes: S41. During the injection stage, the injection pressure is adjusted according to the injection pressure compensation value of S1, and the coolant flow rate is pre-adjusted according to the initial cooling rate correction coefficient to establish the initial linkage state of pressure-cooling. S42. When the injection molding process switches to the holding pressure stage, the holding pressure adjustment ratio is calculated in real time, and the cooling rate correction coefficient is adjusted synchronously according to the ratio. Then, the coolant flow rate is adjusted according to the adjusted coefficient. S43. After the pressure holding stage is completed, maintain the adjusted cooling rate correction coefficient and continue to adjust the coolant flow rate according to the preset cooling time until the melt is completely solidified.
[0012] In one possible implementation, adjusting the cooling rate correction coefficient in step S42 specifically includes: S421. Collect the real-time holding pressure during the holding stage, calculate the difference between the real-time holding pressure and the holding pressure reference value, and obtain the holding pressure adjustment amount. S422. Compare the pressure holding adjustment amount with the pressure holding reference value to obtain the pressure holding adjustment ratio; S423. Multiply the cooling rate correction coefficient by the pressure holding adjustment ratio to obtain the correction range. Then, add the cooling rate correction coefficient and the correction range together to obtain the fine-tuned cooling rate correction coefficient.
[0013] In one possible implementation, step S5 specifically includes: S51. After the injection molded part is demolded, the automotive trim part is scanned in full dimensions to extract the warpage data of each area and generate a warpage inspection report. S52. Compare the actual warpage in the warpage test report with the preset acceptable range, and screen out the unacceptable areas with excessive warpage and the corresponding warpage deviation values. S53. Based on the warpage deviation value of the non-conforming area, adjust the preset compensation threshold and the differential cooling rate benchmark value according to the preset correction ratio.
[0014] The beneficial effects of the injection molding control method for automotive trim parts provided by this invention are as follows: Compared with the prior art, the injection molding control method of this invention constructs a deep linkage system between injection pressure and cooling rate, fundamentally solving the core problem of warpage deformation. It breaks through the existing model where pressure control and cooling control are independent, forming a strong correlation between the pressure state during injection (reflected by the injection pressure compensation value) and the rate regulation during cooling: Based on the warpage region identification results in S1, S2 sets a differentiated cooling benchmark, S3 establishes a quantitative linkage relationship between the injection pressure compensation value and the cooling rate correction coefficient, and S4 translates this relationship into actual adjustments to the coolant flow rate. This allows the cooling rate regulation to accurately match the internal stress state of each molding area, effectively promoting internal stress release and balancing the thermal shrinkage rate, fundamentally solving the problem of warpage deformation in automotive trim parts caused by uneven internal stress and thermal shrinkage. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 A flowchart illustrating an injection molding control method for automotive decorative parts provided in an embodiment of the present invention. Detailed Implementation
[0017] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
[0018] Warpage is the most prominent and difficult-to-solve quality defect in the injection molding production of automotive trim parts. Essentially, warpage in automotive trim parts is caused by a disconnect in the control of process parameters during the injection-holding-cooling stages of the injection process: uneven distribution of internal stress formed by melt flow during the injection stage, failure of pressure compensation during the holding stage to adapt to the internal stress state, and in existing technologies, the pressure control of the injection molding machine and the cooling control of the mold are always independent of each other. Furthermore, the cooling stage does not employ differentiated temperature control for areas of concentrated internal stress, resulting in ineffective release of internal stress and further widening of the difference in melt thermal shrinkage rates, ultimately leading to product warpage.
[0019] In existing technologies, the injection molding control of automotive trim parts generally adopts an independent mode of "pressure control" and "cooling control": On the one hand, the pressure control system of the injection molding machine only focuses on the pressure adjustment during the injection and holding stages, and solves problems such as insufficient melt filling and shrinkage marks through preset pressure parameters or simple dynamic compensation, without considering the internal stress caused by uneven pressure distribution and its demand on the cooling stage; on the other hand, the cooling control system of the mold only presets a fixed cooling rate according to the static partitioning of the cavity and core, and achieves temperature control by adjusting the coolant flow rate, without relating it to the pressure changes during the injection and holding stages, and without differentiating the cooling for areas prone to internal stress.
[0020] This "pressure-cooling separation" control mode results in uneven internal stress formed during the injection and holding pressure stages, which cannot be effectively released through precise temperature control during the cooling stage. Simultaneously, the melt in different regions exhibits significant shrinkage differences due to the mismatch between cooling rates and internal stress states, ultimately leading to warping deformation of automotive trim parts. Based on this, the present invention provides an injection molding control method for automotive trim parts that addresses the warping deformation problem at its root by synergistically controlling injection pressure and cooling rate.
[0021] Please see Figure 1 The present invention will now describe an injection molding control method for automotive trim parts, which includes the following steps: S1. During the injection molding stage, collect the flow state data of the plastic melt in each molding area of the mold, calculate the injection pressure compensation value of each area, and mark the warping high-incidence areas where the injection pressure compensation value exceeds the preset compensation threshold.
[0022] This step is the targeted positioning link of the entire injection molding control method. Its core purpose is to identify the high-incidence warping areas with internal stress concentration during the injection molding process through accurate acquisition and quantitative calculation of the melt flow state. This provides clear control targets for subsequent differentiated cooling and linkage control, and solves the problems of relying on experience, omissions and mislabeling in the identification of warping areas in the existing technology.
[0023] In application, step S1 specifically includes the following steps: S10: Pre-identification and Sensor Densification. Before data collection, injection molding simulation software such as Moldflow is used to perform melt flow and internal stress simulation analysis on the 3D model of the automotive trim parts, pre-identify potential warping high-risk areas such as wall thickness transition areas and snap-fit connection areas, and formulate a sensor densification arrangement scheme accordingly; S11: Deploy multi-type sensor arrays. Deploy multi-type sensor arrays for pressure pulsation, melt flow rate, and shear stress in the injection cylinder, nozzle, and various molding areas of the injection molding machine. Areas with high potential warpage are arranged with a denser array, while regular areas are arranged in a standardized manner. S12: Flow state data acquisition. After the injection stage starts, the pressure pulsation signal, melt flow rate data and shear stress distribution parameters are synchronously acquired by the sensor array at a preset sampling frequency to form a flow state dataset for each molding area; S13: Calculation of injection pressure compensation value. Input the flow state dataset into the preset calculation model, calculate the flow resistance coefficient of each region, and then calculate the injection pressure compensation value of each region based on the flow resistance coefficient and the injection pressure reference value; S14: Warpage High-Incidence Area Marking. The injection pressure compensation value of each area is compared with the preset compensation threshold. Areas exceeding the threshold are marked with warpage high-incidence indicators, generating a warpage high-incidence area distribution map.
[0024] Step S1 employs a dual identification method of "simulation pre-identification" and "dynamic data verification," which can significantly improve the accuracy of identifying high-incidence warping areas and solve the problems of missed or incorrect labeling. At the same time, multiple types of sensors collect data synchronously, and combined with the quantitative calculation of the flow resistance coefficient, the error in the calculation of the injection pressure compensation value can be greatly reduced, ensuring that the compensation value is highly matched with the actual internal stress state. Furthermore, a visualized distribution map of high-incidence warping areas is generated, providing a clear basis for targeted control in subsequent steps, avoiding indiscriminate full-domain control, and improving control efficiency and accuracy.
[0025] S2. Based on the molding requirements of automotive trim parts, preset the cooling rate benchmark value for each molding area of the mold, and set a differentiated cooling rate benchmark value that is different from the normal area for the warping high-incidence area marked S1.
[0026] This step is the baseline parameter setting stage for the entire injection molding control method. Its purpose is to connect with the warpage high-risk area identification results from S1. Based on the material properties, structural characteristics, and molding requirements of the automotive trim part, appropriate cooling rate baseline values are set for both regular and warpage high-risk areas. This ensures the cooling rate matches the internal stress release requirements of each area, laying the foundation for subsequent linkage correction calculations. The parameter setting in this step is directly based on the warpage high-risk area distribution map from S1, while also considering the thermal shrinkage characteristics of the injection molding material and the wall thickness characteristics of the trim part, forming the basis for targeted cooling.
[0027] S3. Based on the injection pressure compensation value obtained in S1, calculate the cooling rate correction coefficient for high-incidence warpage areas and normal areas, and establish the linkage between the injection pressure compensation value and the cooling rate correction coefficient.
[0028] This step is a linkage calculation link in the entire injection molding control method. Its purpose is to establish a quantitative linkage relationship between the injection pressure compensation value and the cooling rate correction coefficient, and to transform the internal stress state during the injection stage (reflected by the injection pressure compensation value) into the basis for cooling rate correction, so as to achieve dynamic adaptation between pressure and cooling.
[0029] In application, step S3 specifically includes the following steps: S31: Reference Parameter Retrieval. Based on the characteristic parameters of the injection molding material, determine the reference values for material viscosity, zone wall thickness, and injection pressure; S32: Calculation of Quantitative Influence Factors. Based on the injection pressure compensation value, the injection pressure compensation ratio is calculated. Then, combining the real-time material viscosity value and the measured wall thickness value, the material viscosity influence factor is calculated. and regional wall thickness deviation rate Among them, the material viscosity influencing factor =(Actual melt viscosity - Standard melt viscosity) / Standard melt viscosity. The actual melt viscosity is calculated based on the characteristic frequency components of the pressure pulsation signal during the injection stage, and the standard melt viscosity is the calibrated viscosity value of the injection molding material for automotive trim parts. In this step, the calculation of the material viscosity influence factor includes: S321. Extract the characteristic frequency components of the pressure pulsation signal during the injection stage, and calculate the real-time viscosity of the melt using the frequency-viscosity correlation formula. S322. Calculate the difference between the real-time viscosity of the melt and the reference viscosity value of the material, and then compare the difference with the reference viscosity value of the material to obtain the material viscosity influence factor.
[0030] S33: Dynamic Weighting Factor Calculation. Introducing a dynamic weighting factor to account for the influence of material viscosity. Regional wall thickness deviation rate Compensation ratio with injection pressure Weighted calculations are performed to obtain the dynamic weighting factors for each region. ;in, , , The preset weighting coefficients are used to calculate the degree of influence of each factor on the cooling rate. S34: Calculation of cooling rate correction coefficient. Based on dynamic weighting factor. Based on the preset baseline correction coefficient, the cooling rate correction coefficient for each region is calculated, a correction coefficient allocation table is generated, and a one-to-one correspondence between the injection pressure compensation value and the cooling rate correction coefficient is established.
[0031] Step S3 establishes a quantitative linkage between the injection pressure compensation value and the cooling rate correction coefficient, enabling the adjustment of the cooling rate to accurately reflect the internal stress state during the injection stage, thus achieving dynamic adaptation between pressure and cooling. By introducing dynamic weighting factors and quantifying influencing factors such as material viscosity, wall thickness, and injection pressure, the correction coefficient calculation can be adapted to automotive trim parts of different materials and structures, improving the adaptability of the linkage control. Through standardized calculation steps, the calculation error of the cooling rate correction coefficient is greatly reduced, and the generated correction coefficient allocation table provides a clear and accurate basis for subsequent coolant flow rate adjustment, avoiding parameter deviations caused by empirical adjustments.
[0032] S4. Adjust the coolant flow rate in each area of the mold according to the cooling rate correction coefficient to achieve linkage control between injection pressure compensation and cooling rate until the injection cooling stage is completed.
[0033] This step is the implementation link of the linkage control of the entire injection molding control method. Its purpose is to transform the linkage calculation results of S3 into actual cooling control actions. By adjusting the coolant flow rate in each area of the mold, the linkage control of injection pressure compensation and cooling rate is implemented, covering the entire stages of injection, holding pressure and cooling, to achieve three-stage pressure-cooling coordinated control.
[0034] In application, step S4 specifically includes: S41: During the injection stage, the injection pressure is adjusted according to the injection pressure compensation value of S1, and the coolant flow rate is pre-adjusted according to the initial cooling rate correction coefficient calculated by S3 to establish the initial linkage state of pressure-cooling. S42: When the injection molding process switches to the holding pressure stage, the real-time holding pressure is collected, the holding pressure adjustment ratio is calculated in real time, the cooling rate correction coefficient is adjusted synchronously according to the ratio, and the coolant flow rate is adjusted according to the adjusted coefficient. In this step, adjusting the cooling rate correction factor specifically includes: S421. Collect the real-time holding pressure during the holding stage, calculate the difference between the real-time holding pressure and the holding pressure reference value, and obtain the holding pressure adjustment amount. S422. Compare the pressure holding adjustment amount with the pressure holding reference value to obtain the pressure holding adjustment ratio; S423. Multiply the cooling rate correction coefficient by the pressure holding adjustment ratio to obtain the correction range, and then add the cooling rate correction coefficient and the correction range to obtain the fine-tuned cooling rate correction coefficient. S43: After the pressure holding stage is completed, maintain the adjusted cooling rate correction coefficient and continue to adjust the coolant flow rate according to the preset cooling time until the melt is completely solidified.
[0035] Step S4 implements pressure-cooling linkage control, enabling precise matching of the internal stress state during the injection stage through adjustment of the cooling rate. This solves the problem of multi-stage parameter disconnection in existing technologies, making the melt flow, pressure replenishment, and solidification processes form an organic whole. Internal stress is significantly reduced, and the uniformity of thermal shrinkage is improved. Furthermore, the synchronous adjustment during the holding pressure stage allows the internal stress generated during the pressure replenishment process to be released in a timely manner through cooling regulation, avoiding warping deformation caused by the superposition of internal stress during the holding pressure stage, and further reducing the risk of warping.
[0036] S5. After injection molding, the warpage of the automotive trim parts is detected. If the warpage exceeds the preset acceptable range, the preset compensation threshold and the differential cooling rate benchmark value are corrected based on the warpage detection results.
[0037] This step is a closed-loop optimization link in the entire injection molding control method. Its purpose is to verify the effect of the preceding linkage control by detecting the warpage of the injection molded product, and to make targeted corrections to the core control parameters (preset compensation threshold, differentiated cooling rate benchmark value) based on the detection results, forming a closed-loop optimization system of "control-detection-correction-recontrol" so that the control parameters can continuously adapt to the production conditions and improve the stability of batch production.
[0038] In application, step S5 specifically includes: S51: Full-dimensional warpage inspection. After the injection molded part is demolded, a high-precision inspection device such as a 3D profilometer is used to perform a full-dimensional scan of the automotive trim part, extract the warpage data of each area, and generate a warpage inspection report; S52: Screening of Non-conforming Areas. Compare the actual warpage in the warpage test report with the preset acceptable range to screen out non-conforming areas with excessive warpage and their corresponding warpage deviation values; S53: Targeted Correction of Core Parameters. Based on the warpage deviation value of the non-conforming area, the preset compensation threshold and differentiated cooling rate benchmark value corresponding to the non-conforming area are specifically corrected according to the preset correction ratio, while the parameters of non-conforming areas remain unchanged.
[0039] Step S5 establishes a closed-loop optimized control system, enabling continuous correction and iterative optimization of control parameters based on actual production results. This solves the problem of "post-production detection without targeted correction" in existing technologies, improving the stability of batch production. In this step, full-size scanning detection is used, achieving 100% coverage of warpage detection and 100% accuracy in locating non-conforming areas, ensuring the comprehensiveness and precision of the detection results. By only correcting parameters for non-conforming areas, the mismatch problem caused by "one-size-fits-all" global parameter adjustments is avoided, ensuring that the corrected parameters are highly matched with the actual warpage problem.
[0040] Example (a) Target Groups The automotive door panel trim made of PP material (grade PP-H-T03) was selected as the implementation object. The product size is 1200mm×300mm×5mm, including 3 snap-fit connection areas and 2 wall thickness transition areas (wall thickness 2-5mm). The industry standard and process preset warpage acceptable range is ≤0.2mm.
[0041] (II) Equipment Preparation Injection molding machine: Haitian servo hydraulic injection molding machine; Sensing and detection equipment: high-frequency pressure pulsation sensor, melt flow rate sensor, shear stress sensor; 3D profilometer; Mold and cooling system: Automotive door panel mold with independent zoned cooling, each molding area is equipped with a high-frequency response coolant flow regulating valve; Auxiliary software and control system: Moldflow2025 injection molding simulation software; Siemens S7-1500 PLC control system (with built-in calculation model and process control program of this method).
[0042] (III) Calibration of materials and process parameters 1. Basic material parameters: Standard melt viscosity =1000Pa s, linear shrinkage rate 1.0%-2.5%; 2. Injection pressure reference: Injection pressure reference value =80MPa, pressure holding pressure reference value =64MPa (80% of the baseline injection pressure); 3. Cooling rate benchmark: Standard cooling rate value for normal areas =1.0℃ / s (corresponding to an initial coolant flow rate of 2.0L / min); Cooling rate benchmark for high-incidence warpage areas =0.8℃ / s (corresponding to an initial coolant flow rate of 1.6L / min). Due to higher internal stress in the snap-fit connection area, a slight adjustment is needed. =0.7℃ / s (corresponding to an initial coolant flow rate of 1.4L / min); 4. Calculate relevant parameters: The preset compensation threshold is 10% of the injection pressure baseline (i.e., 8 MPa); the preset weighting coefficient for the dynamic weighting factor. =0.4、 =0.3、 =0.3; Frequency-viscosity correlation formula ( This is the real-time viscosity of the melt, in Pa. s; f is the characteristic frequency of the pressure pulsation signal (in Hz); reference correction coefficient = 1.0; preset warpage correction ratio = 20%; 5. Process timing parameters: Sampling frequency of 10kHz during injection stage, holding pressure duration of 10s, and cooling duration of 25s.
[0043] Specific implementation steps Import the 3D model of the automotive door panel trim into Moldflow 2025, input the rheological properties of PP-H-T03 and the calibrated process parameters, and run the melt flow and internal stress simulation analysis. The simulation results show that there is stress concentration in the snap-fit connection area and the wall thickness transition area (internal stress in the snap-fit area ≥80MPa, wall thickness transition area ≥60MPa), which is pre-identified as a potential high-incidence area of warping.
[0044] Based on the pre-identification results, a sensor encryption scheme is formulated: one set of sensors is placed every 50 mm in areas with high potential warping, and one set of sensors is placed every 100 mm in normal areas.
[0045] According to the encryption scheme, pressure pulsation sensors and melt flow rate sensors are arranged in the injection cylinder and nozzle of the injection molding machine; pressure pulsation sensors, melt flow rate sensors and shear stress sensors are arranged in each forming area of the mold (snap-fitting area, wall thickness transition area and regular area). All sensors are connected to the data acquisition system to complete the array deployment.
[0046] Start the injection molding machine and set the injection process parameters: injection temperature 180-200℃, injection speed 50-80mm / s. After the injection stage starts, the sensor array synchronously collects the pressure pulsation signal, melt flow rate data and shear stress distribution parameters of each area at a sampling frequency of 10kHz, forming a flow state dataset of each molding area.
[0047] Input the flow state dataset into the PLC's built-in preset calculation model, first calculate the flow resistance coefficient of each region, and then follow the formula. ( This is the injection pressure compensation value. The region flow resistance coefficient, Using the reference flow resistance coefficient (valued at 1.0), the injection pressure compensation value was calculated, and the results are as follows: Snap-fit connection area: Flow resistance coefficient =1.15, =80×(1.15 / 1.0)-80=12MPa; Wall thickness transition zone: Flow resistance coefficient =1.10, =80×(1.10 / 1.0)-80=8MPa; Normal region: Flow resistance coefficient =1.02, =80×(1.02 / 1.0)-80=1.6MPa.
[0048] The injection pressure compensation value of each region is compared with the preset compensation threshold of 8 MPa. Regions exceeding or equal to the threshold are marked with high warpage incidence indicators, generating a distribution map of high warpage incidence areas: The snap-fit connection area (12MPa > 8MPa) and the wall thickness transition area (8MPa = 8MPa) are marked as areas prone to warping. Normal area (1.6MPa < 8MPa): This is the normal forming area.
[0049] Based on the molding requirements of automotive door panel trim parts (thermal shrinkage characteristics of PP material, stress state in each area), and combined with the marking results of high warpage areas, the cooling rate settings for each area were completed according to the preset cooling rate benchmark values, forming a standardized cooling rate benchmark value table, as shown below:
[0050] Taking the snap-fit connection area as a calculation example (the wall thickness transition area and the regular area are calculated using the same formula), a quantitative linkage between the injection pressure compensation value and the cooling rate correction coefficient is established.
[0051] From the characteristic parameters of PP-H-T03, the following was determined: Material viscosity reference value = 1000 Pa s, the baseline value of the area wall thickness is 3mm (the design wall thickness of the snap-fit connection area), and the baseline value of the injection pressure is 80MPa.
[0052] Calculate the quantitative impact factor 1. Injection pressure compensation ratio : ; 2. Factors affecting material viscosity : Extracting the characteristic frequency of the pressure pulsation signal in the snap-fit connection area =200Hz, substituting into the frequency-viscosity correlation formula, we obtain the real-time viscosity of the melt. 1200Pa s; According to the formula ,have to =(1200 (1000) / 1000 = 0.2; Area wall thickness deviation rate : The measured wall thickness of the snap-fit connection area is 3mm, according to the formula. = (Measured wall thickness - Reference wall thickness) / Reference wall thickness, ... =(3 3) / 3=0.
[0053] Calculate dynamic weighting factors : According to the formula Substituting the calibrated weighting coefficients and the calculated values above, we get: =0.4×0.2+0.3×0+0.3×15%=0.08+0+0.045=0.125.
[0054] Calculate the cooling rate correction factor According to the formula ,( This is a correction factor for the cooling rate. Using a base correction factor (valued at 1.0), the correction factor allocation table is generated, and the results are as follows:
[0055] The coolant flow rate in each area is adjusted according to the cooling rate correction coefficient, and the linkage control is performed in three stages: injection, pressure holding and cooling. Taking the snap-fit connection area as an example, all calculations are based on the previous calibration and calculation results to ensure that the parameters are synchronized and adapted.
[0056] 1. Adjust the injection pressure: Adjust the injection pressure in the snap-fit connection area to... + =80+12=92MPa; 2. Pre-adjust coolant flow rate: according to the formula ( This represents the actual coolant flow rate. Calculate the initial flow rate of the coolant to obtain the snap-fit connection area. =1.4×0.875=1.225L / min, establish the initial linkage state of pressure-cooling.
[0057] When the injection molding machine fills 95% of the mold cavity with melt, it automatically switches to the holding pressure stage, fine-tunes the cooling rate correction coefficient, and adjusts the flow rate simultaneously. Real-time pressure monitoring =70.4MPa, calculate the pressure holding adjustment. =70.4-64=6.4 MPa; Calculate the pressure holding adjustment ratio ; Calculate the correction range =0.875×10%=0.0875, the cooling rate correction factor after fine-tuning. =0.875 + 0.0875 = 0.9625; Synchronous adjustment of coolant flow rate =1.4×0.9625=1.3475L / min.
[0058] After the pressure holding stage lasts for 10 seconds, the injection molding process enters the cooling stage. The fine-tuned cooling rate correction coefficient is maintained and continuously adjusted according to the coolant flow rate of each area. The cooling time is 25 seconds until the melt is completely solidified, completing the entire pressure-cooling linkage control process.
[0059] After the injection molded part is demolded, the demolded automotive door panel trim part is placed in a 3D profilometer for full-size high-precision scanning, and warpage data of each molding area is extracted to generate a warpage detection report.
[0060] The actual warpage was compared with the preset acceptable range of ≤0.2mm to screen out unacceptable areas with excessive warpage and calculate the warpage deviation value (deviation value = actual warpage - upper limit of acceptable range). The test results are as follows:
[0061] In this test, the warpage in all areas did not exceed the standard, so there was no need to adjust the preset compensation threshold and the differential cooling rate benchmark value. If a certain area exceeded the standard (such as the actual warpage in the snap-fit connection area being 0.25mm), the preset compensation threshold for that area was adjusted from 8MPa to 9.6MPa, and the differential cooling rate benchmark value was adjusted from 0.7℃ / s to 0.56℃ / s, according to the preset correction ratio of 20%, thus achieving closed-loop optimization of parameters.
[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for controlling the injection molding of automotive decorative parts, characterized in that, Includes the following steps: S1. During the injection molding stage, collect flow state data of plastic melt in each molding area of the mold, calculate the injection pressure compensation value of each area, and mark the warping high-incidence areas where the injection pressure compensation value exceeds the preset compensation threshold. S2. Based on the molding requirements of automotive trim parts, preset the cooling rate benchmark value for each molding area of the mold, and set a differentiated cooling rate benchmark value that is different from the normal area for the warping high-incidence area marked S1. S3. Based on the injection pressure compensation value obtained in S1, calculate the cooling rate correction coefficient for high warpage areas and normal areas, and establish the linkage between the injection pressure compensation value and the cooling rate correction coefficient. S4. Adjust the coolant flow rate in each area of the mold according to the cooling rate correction coefficient to achieve linkage control between injection pressure compensation and cooling rate until the injection cooling stage is completed. S5. After injection molding, the warpage of the automotive trim parts is detected. If the warpage exceeds the preset acceptable range, the preset compensation threshold and the differential cooling rate benchmark value are corrected based on the warpage detection results.
2. The injection molding control method for automotive decorative parts as described in claim 1, characterized in that, Step S1 specifically includes: S11. Deploy multi-type sensor arrays, including arranging pressure pulsation sensors, melt flow rate sensors and shear stress sensors in the injection cylinder, nozzle and each molding area of the mold of the injection molding machine. S12. After the injection stage is started, the pressure pulsation signal, melt flow rate data and shear stress distribution parameters are collected synchronously by the sensor array at a preset sampling frequency to form a data set of the flow state of each molding area. S13. Input the flow state dataset into the preset calculation model, calculate the flow resistance coefficient of each region, and then calculate the injection pressure compensation value of each region based on the flow resistance coefficient and the injection pressure reference value. S14. Compare the injection pressure compensation value of each region with the preset compensation threshold, mark the regions that exceed the threshold with high warping incidence, and generate a distribution map of high warping incidence regions.
3. The injection molding control method for automotive decorative parts as described in claim 2, characterized in that, Before step S11, injection molding simulation software is used to perform melt flow and internal stress simulation analysis on the three-dimensional model of the automotive trim part, pre-identify potential high-risk warping areas, and formulate a sensor densification arrangement scheme based on the identification results.
4. The injection molding control method for automotive decorative parts as described in claim 1, characterized in that, Step S3 specifically includes: S31. Determine the reference values for material viscosity, zone wall thickness, and injection pressure based on the characteristic parameters of the injection molding material; S32. Calculate the injection pressure compensation ratio based on the injection pressure compensation value, and calculate the material viscosity influence factor and regional wall thickness deviation rate by combining the real-time value of material viscosity and the measured value of wall thickness. S33. Introduce dynamic weighting factors and calculate the dynamic weighting factors of each region by weighting the material viscosity influence factor, the regional wall thickness deviation rate and the injection pressure compensation ratio. S34. Based on the dynamic weighting factor and the preset benchmark correction coefficient, calculate the cooling rate correction coefficient for each region and generate a correction coefficient allocation table.
5. The injection molding control method for automotive decorative parts as described in claim 4, characterized in that, The formula for calculating the dynamic weighting factor is as follows: ;in, As a dynamic weighting factor, , , For preset weighting coefficients, This is a factor affecting the viscosity of materials. This refers to the regional wall thickness deviation rate. This is the injection pressure compensation ratio.
6. The injection molding control method for automotive decorative parts as described in claim 5, characterized in that, The material viscosity influence factor =(Actual melt viscosity - Standard melt viscosity) / Standard melt viscosity. The actual melt viscosity is calculated based on the characteristic frequency components of the pressure pulsation signal during the injection stage, and the standard melt viscosity is the calibrated viscosity value of the injection molding material for automotive trim parts.
7. The injection molding control method for automotive decorative parts as described in claim 4, characterized in that, In step S32, the calculation of the material viscosity influence factor includes: S321. Extract the characteristic frequency components of the pressure pulsation signal during the injection stage, and calculate the real-time viscosity of the melt using the frequency-viscosity correlation formula. S322. Calculate the difference between the real-time viscosity of the melt and the reference viscosity value of the material, and then compare the difference with the reference viscosity value of the material to obtain the material viscosity influence factor.
8. The injection molding control method for automotive decorative parts as described in claim 1, characterized in that, Step S4 specifically includes: S41. During the injection stage, the injection pressure is adjusted according to the injection pressure compensation value of S1, and the coolant flow rate is pre-adjusted according to the initial cooling rate correction coefficient to establish the initial linkage state of pressure-cooling. S42. When the injection molding process switches to the holding pressure stage, the holding pressure adjustment ratio is calculated in real time, and the cooling rate correction coefficient is adjusted synchronously according to the ratio. Then, the coolant flow rate is adjusted according to the adjusted coefficient. S43. After the pressure holding stage is completed, maintain the adjusted cooling rate correction coefficient and continue to adjust the coolant flow rate according to the preset cooling time until the melt is completely solidified.
9. The injection molding control method for automotive decorative parts as described in claim 8, characterized in that, In step S42, adjusting the cooling rate correction coefficient specifically includes: S421. Collect the real-time holding pressure during the holding stage, calculate the difference between the real-time holding pressure and the holding pressure reference value, and obtain the holding pressure adjustment amount. S422. Compare the pressure holding adjustment amount with the pressure holding reference value to obtain the pressure holding adjustment ratio; S423. Multiply the cooling rate correction coefficient by the pressure holding adjustment ratio to obtain the correction range. Then, add the cooling rate correction coefficient and the correction range together to obtain the fine-tuned cooling rate correction coefficient.
10. The injection molding control method for automotive decorative parts as described in claim 1, characterized in that, Step S5 specifically includes: S51. After the injection molded part is demolded, the automotive trim part is scanned in full dimensions to extract the warpage data of each area and generate a warpage inspection report. S52. Compare the actual warpage in the warpage test report with the preset acceptable range, and screen out the unacceptable areas with excessive warpage and the corresponding warpage deviation values. S53. Based on the warpage deviation value of the non-conforming area, adjust the preset compensation threshold and the differential cooling rate benchmark value according to the preset correction ratio.