Injection molding adaptive pack control method

Abstract

This application relates to an adaptive holding pressure control method for injection molding. The method includes: collecting geometric features of the injection molded part and real-time process data; calculating the skin safety time and gate freezing time of the effective pressure transmission path based on thermodynamic analysis, generating a set of process parameters including first and second holding pressures; during the holding pressure stage, utilizing the cooling time difference to sequentially perform staged adjustments for low-pressure shield anti-flash, flexible pressure increase, and high-pressure shrinkage compensation to prevent shrinkage marks; and after cooling, detecting the finished product quality and correcting the process parameters in a closed-loop manner. This application has the advantages of resolving the conflict between flash and shrinkage marks without complex mold modifications, and significantly improving the dimensional accuracy and production stability of injection molded parts.

Description

Technical Field

[0001] This application relates to the field of industrial automation control, and in particular to an adaptive pressure holding control method for injection molding. Background Technology

[0002] In the manufacturing of automotive injection molded parts, the product structure design often includes significant differences in wall thickness, leading to a persistent challenge in controlling flash and shrinkage marks during production. Thick-walled areas shrink considerably during cooling, requiring high holding pressure to continuously replenish the melt and maintain dimensional accuracy and surface smoothness. However, the injection mold cavity is typically a connected fluid system, and the high holding pressure applied to this system is simultaneously transmitted to thin-walled areas or the mold parting line. For these areas with lower flow resistance or higher sealing requirements, excessive pressure can easily exceed the clamping force, causing melt overflow and flash defects.

[0003] Existing injection molding process control methods mostly employ setting a constant holding pressure or using simple segmented holding pressure curves based on experience. This conventional control strategy struggles to address the conflicting molding requirements mentioned above. If the overall holding pressure is reduced to suppress flash, thick-walled areas often develop noticeable shrinkage marks or internal voids due to insufficient shrinkage compensation; conversely, if the pressure is increased to eliminate shrinkage marks, thin-walled areas are prone to flash due to pressure overload. While this problem can be mitigated by modifying the mold structure or adding complex mechanical control valves, this often comes with high manufacturing costs and long development cycles.

[0004] More critically, existing methods typically cannot accurately calculate and utilize the solidification time difference between the effective pressure transmission path and the thick-walled region in the injection molded part. Because the exact moment when the thin-walled channel establishes a solidification skin capable of withstanding high pressure cannot be accurately determined, the control system struggles to precisely segment and schedule pressure over time. This prevents process engineers from implementing a dynamic control strategy of first using low pressure to protect the thin wall and then using high pressure for strong shrinkage compensation, thus failing to effectively solve the problem of coexisting flash and shrinkage marks without altering the mold hardware. Summary of the Invention

[0005] To address the technical problem that existing injection molding processes struggle to simultaneously prevent flash in thin-walled areas and shrinkage in thick-walled areas when producing products with significant differences in wall thickness, resulting in low finished product yield, this application provides an adaptive pressure control method for injection molding.

[0006] This application provides an adaptive pressure holding control method for injection molding, which adopts the following technical solution: An adaptive pressure holding control method for injection molding includes: S1. Collect the geometric structural features of the injection molded part and the real-time process data of the injection molding process, and clean and structure the real-time process data to obtain a structured process dataset containing pressure time sequence curves and melt temperature; wherein, the geometric structural features at least characterize the thick-walled region, the thin-walled region and the effective pressure transmission path between the two in the injection molded part. S2. Based on the geometric parameters of the effective pressure transmission path and the structured process dataset, the time required for the effective pressure transmission path and the thick-walled region to reach the predetermined condensation state is calculated through thermodynamic analysis logic. This determines the key process time nodes and generates a process parameter set including a first holding pressure and a second holding pressure. The first holding pressure is a low pressure below the critical value for flash generation, and the second holding pressure is a high pressure to meet the feeding requirements of the thick-walled region. S3. During the holding pressure stage of the injection molding process, the holding pressure is output in stages based on the key process time nodes to adjust the mold cavity pressure, and the flash and shrinkage marks are controlled by utilizing the time difference between the melt solidification of the thick-walled region and the thin-walled region. S4. After the cooling stage of the injection molded part is completed, inspect the finished quality of the injection molded part, and reverse the critical process time node or the first holding pressure and the second holding pressure according to the defect type, and update the process parameter group for the next production cycle.

[0007] Optionally, S1 includes the following sub-steps: S11. Establish a digital model of the injection molded part, identify thick-walled and thin-walled regions, and calculate the ratio of flow length to wall thickness of the thick-walled and thin-walled regions; S12. Determine the flow channel connectivity from the gate to the thick-walled region, identify whether there are flow guiding structural features for assisting pressure transmission, and determine the geometric parameters of the effective pressure transmission path based on the identification results; S13. Real-time acquisition of melt temperature, holding pressure and screw position data, and the use of filtering algorithms to remove outliers and noise, generating the filtered pressure time-series curve and the melt temperature synchronized with the pressure time-series curve.

[0008] Optionally, step S2 includes the following sub-steps: S21. Based on the preset melt rheological parameters and the geometric features, calculate the maximum allowable pressure without flash as the first holding pressure, and calculate the minimum holding pressure to meet the feeding requirements of the thick-walled region as the second holding pressure. S22. Based on the melt temperature in the structured process dataset, and obtaining the geometric parameters of the effective pressure transmission path from the geometric structural features, and combining the second holding pressure and the preset material thermophysical parameters, calculate the skin safety time required for the effective pressure transmission path to form a skin that resists the second holding pressure, and the gate freezing time for the gate area to completely solidify. S23. Perform thermodynamic criterion verification to determine whether the gate freezing time is greater than the sum of the skin layer safety time and the preset safety margin; S24. If the verification passes, the skin safety time is defined as the pressure boosting start point, the gate freezing time is defined as the shrinkage compensation cutoff point, and the first holding pressure, the second holding pressure, and the key process time nodes are combined to generate the process parameter group; if the verification fails, a correction suggestion to adjust the process temperature or mold size is output, and an error is reported and the current molding cycle is terminated, wherein the key process time nodes include the pressure boosting start point and the shrinkage compensation cutoff point.

[0009] Optionally, S22 includes the following sub-steps: S221. Obtain the shear yield strength of the injection molding material at the current mold temperature from the preset material thermophysical parameters, establish the mechanical equilibrium equation between the shear stress generated by the second holding pressure and the shear yield strength, solve the equation to obtain the minimum wall thickness required for the effective pressure transmission path to not break, and define it as the critical skin thickness. S222. Based on the thermal diffusivity in the preset material thermal property parameters and the melt temperature, the cooling time required for the solidification front to advance from the mold wall to the critical skin thickness position is calculated using a one-dimensional unsteady thermal conduction equation, and the cooling time is defined as the skin safety time. S223. Based on the geometry and thermal conductivity of the gate region, calculate the time required for the average melt temperature of the gate region to drop to the no-flow temperature of the injection molding material, and define the time as the gate freezing time.

[0010] Optionally, step S3 includes the following sub-steps: S31. During the period from the start of the pressure holding to the time corresponding to the safe time of the skin layer, output the first pressure holding pressure and maintain it to keep the melt in contact with the mold wall and wait for the effective pressure transmission path to establish the condensed skin layer; S32. At the moment when the safe time of the skin layer is reached during the injection molding process, the output holding pressure is controlled according to the preset pressure rise rate, so that the cavity pressure linearly transitions from the first holding pressure to the second holding pressure, so as to avoid pressure shock damaging the condensed skin layer in the effective pressure transmission path; S33. Output the second holding pressure and maintain it, and use the window period when the gate area has not yet frozen to replenish the thick-walled area until the time corresponding to the gate freezing time is reached or the effective pressure transmission path is blocked.

[0011] Optionally, step S3 further includes the following sub-steps: S34. During the output of the second holding pressure, the axial movement speed of the injection molding machine screw is collected in real time; S35. If it is detected that the axial movement speed of the screw is lower than a preset micro-motion threshold during the process of maintaining the second pressure holding pressure, it is determined that the gate area or the effective pressure transmission path has been frozen in advance. S36. When it is determined that the gate area or the effective pressure transmission path has been frozen in advance, the output of the second holding pressure is immediately terminated and the cooling stage is entered. At the same time, the injection molded part in the current production cycle is marked as having internal shrinkage defects.

[0012] Optionally, a ramp control strategy is adopted in sub-step S32: The control system generates a pressure command that increases linearly with time based on a preset slope. The preset slope is less than the stress relaxation rate of the condensation layer within the effective pressure transmission path, so as to ensure that the condensation layer within the effective pressure transmission path remains intact during the pressure increase process.

[0013] Optionally, step S4 includes the following sub-steps: S41. Acquire the finished image of the injection molded part, detect the flash thickness at the parting surface position corresponding to the effective pressure transmission path, and the shrinkage depth of the surface of the thick-walled area; S42. If the burr thickness exceeds the preset first defect threshold, then in the next production cycle, the time margin is increased or the second holding pressure is reduced based on the skin safety time; S43. If the depth of the shrinkage mark exceeds the preset second defect threshold, the second holding pressure is increased in the next production cycle, or the mold temperature is adjusted when it is determined that the gate area is frozen in advance. S44. The corrected key process time nodes, the first holding pressure, and the second holding pressure are fed back to the structured process dataset to update the original process parameter settings, and the updated process parameter settings are used to guide the injection molding of the next production cycle.

[0014] In summary, this application includes at least one of the following beneficial technical effects: 1. This application calculates the time node for establishing the condensation skin by collecting real-time process data and combining it with geometric features for thermodynamic analysis. Based on this node, the holding pressure is adjusted in stages. A lower first holding pressure is output before skin formation to suppress flash, and a higher second holding pressure is output during the window period after skin formation to compensate for shrinkage in thick-walled areas. This control strategy utilizes the difference in condensation rates in different regions to effectively solve the technical contradiction between thin-walled overflow and thick-walled shrinkage marks without changing the mold structure, thereby improving the appearance quality and dimensional accuracy of the product.

[0015] 2. This application utilizes adaptive control at the software algorithm level to replace the traditional mechanical structure modification scheme. Compared to existing technologies that require the addition of mechanical valves or complex flow channel designs, this application can achieve the same process objectives simply by adjusting the pressure output timing through the injection molding machine's control system. This not only reduces the manufacturing and maintenance costs of the mold but also reduces the risk of production downtime due to wear or failure of mechanical parts, improving the equipment's versatility and production efficiency.

[0016] 3. This application introduces a closed-loop feedback mechanism based on finished product quality inspection. By detecting the flash thickness and shrinkage depth of the finished product after cooling, the system can reversely correct key process time points or pressure parameters. This mechanism enables the control system to automatically adapt to disturbances caused by raw material batch fluctuations, ambient temperature changes, or equipment performance drift, ensuring that process parameters are always in an optimal state, thereby guaranteeing the long-term stability of the injection molding production process and the consistency of product quality. Attached Figure Description

[0017] Figure 1 A flowchart illustrating an adaptive pressure holding control method for injection molding according to an embodiment of the present invention is shown. Detailed Implementation

[0018] The present application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the application and are not intended to limit the scope of the application.

[0019] In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the inventive concept. As part of this specification, some of the accompanying drawings of this disclosure are block diagrams illustrating structures and devices to avoid complicating the disclosed principles. For clarity, not all features of the actual embodiment need to be described. Furthermore, the language used in this disclosure has been primarily chosen for readability and instructional purposes and may not have been chosen to define or limit the subject matter of the invention, thus requiring the necessary claims to determine such inventive subject matter. References to “an embodiment” or “an embodiment” in this disclosure mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment, and multiple references to “an embodiment” or “an embodiment” should not be construed as necessarily referring to the same embodiment.

[0020] Unless explicitly defined, the terms “a,” “an,” and “the” are not intended to refer to a singular entity, but rather to include a general category whose specific examples can be used for illustration. Therefore, the use of the terms “a” or “an” can mean any number of at least one, including “a,” “one or more,” “at least one,” and “one or more.” The term “or” means any of the options and any combination of the options, including all options unless explicitly indicated that the options are mutually exclusive. The phrase “at least one of” when combined with a list of items refers to a single item in the list or any combination of items in the list. The phrase does not require all items listed unless explicitly defined as such.

[0021] This application discloses an adaptive pressure holding control method for injection molding, including S1-S4.

[0022] S1. Collect the geometric structural features of the injection molded part and the real-time process data of the injection molding process, and clean and structure the real-time process data to obtain a structured process dataset containing pressure time sequence curves and melt temperature; wherein, the geometric structural features at least characterize the thick-walled region, the thin-walled region and the effective pressure transmission path between the two in the injection molded part.

[0023] Firstly, the acquisition of geometric features and real-time process data for injection molded parts primarily relies on multi-source sensing systems and digital interfaces integrated into the injection molding production unit. Specifically, the geometric features of the injection molded parts can be directly obtained by importing the product's 3D CAD design files, or by using a high-precision 3D laser scanner to perform reverse engineering scanning of the sample to obtain point cloud data. This feature data accurately covers physical quantities such as the product's wall thickness distribution, flow length ratio, and volume-to-surface area ratio. Simultaneously, real-time process data during the injection molding process is synchronously acquired through pressure sensors installed at the injection molding machine nozzle, temperature sensors inside the mold cavity, and electronic rulers indicating the screw position. The acquired physical quantities include, but are not limited to, nozzle pressure, mold cavity pressure, melt temperature, screw feed speed, and screw axial position. These data collectively constitute a multi-dimensional vector flow describing the current molding state.

[0024] The geometric characteristics of injection molded parts directly determine the differences in thermodynamic distribution within the mold cavity after the melt fills. According to the principle of heat conduction, the cooling rate of the melt within the mold is inversely proportional to the square of the wall thickness. Therefore, areas with different wall thicknesses will exhibit drastically different thermal states within the same cooling time. Taking a typical injection molded part with reinforcing ribs and mounting bosses as an example, thin-walled areas located at the product edges or where the reinforcing ribs are located, due to their large surface area, dissipate heat rapidly and easily form a solidified layer. However, thick-walled areas located in the product center or where mounting bosses are used for screw fixing, due to heat accumulation and difficulty in dissipation, maintain a high-temperature flowing state in their core melt for a longer period. This non-uniformity leads to the subsequent discrepancies between flash and shrinkage marks. Raw sensor signals are often mixed with high-frequency noise generated by electromagnetic interference or mechanical vibration, and the data sampling frequencies of different sensors may be inconsistent. Data cleaning aims to remove outliers using filtering algorithms to restore the true process fluctuations. Structured processing aligns the independent pressure and temperature data in the time dimension with the screw position data in the spatial dimension to generate a time-series synchronized structured process dataset. The purpose of generating this dataset is to establish a real-time mapping relationship between pressure transmission and temperature change, providing accurate input variables for subsequent thermodynamic analysis and ensuring that the computational model can accurately capture the melt's response characteristics to pressure under specific temperature conditions at a given moment.

[0025] Thick-walled regions refer to the areas in the product design with the thickest walls, slowest cooling, and most prone to volume shrinkage and depressions. Thin-walled regions refer to the areas with thinner walls, fastest cooling, and prone to flash and overflow at the parting surface due to insufficient clamping force. The effective pressure transmission path refers to the fluid channel connecting the gate to the thick-walled regions. Physically, this path may traverse one or more thin-walled regions. During the holding pressure stage, the melt rheological state along the effective pressure transmission path evolves dynamically. As time progresses and the temperature decreases, the melt viscosity within this path gradually increases, and the solidified layer thickness continuously grows from the outside in. Once this path is completely frozen, even if the injection molding machine screw continues to apply pressure, the pressure cannot be transmitted to the thick-walled region at the end, leading to shrinkage compensation failure. Therefore, accurately characterizing the evolution of this path is crucial for achieving effective shrinkage compensation.

[0026] Optionally, S1 includes the following sub-steps S11-S13.

[0027] S11. Establish a digital model of the injection molded part, identify thick-walled and thin-walled regions, and calculate the ratio of flow length to wall thickness of the thick-walled and thin-walled regions.

[0028] S12. Determine the flow channel connectivity from the gate to the thick-walled region, identify whether there are flow guiding structural features for assisting pressure transmission, and determine the geometric parameters of the effective pressure transmission path based on the identification results.

[0029] S13. Real-time acquisition of melt temperature, holding pressure and screw position data, and the use of filtering algorithms to remove outliers and noise, generating the filtered pressure time-series curve and the melt temperature synchronized with the pressure time-series curve.

[0030] A digital model of the injection molded part is established, and thick-walled and thin-walled regions are identified through geometric topology analysis. The ratio of flow length to wall thickness for each region is calculated. This ratio quantifies the friction loss and heat dissipation rate of melt flow in process evaluation; a larger ratio indicates more difficult pressure transmission and faster cooling. Based on this, the connectivity of the runner from the gate to the thick-walled region is determined, and the presence of guiding structural features (such as locally thickened runners or reinforcing ribs) used to assist pressure transmission is identified. The system determines the geometric parameters of the effective pressure transmission path differently based on the identification results: if a guiding structure exists, its cross-sectional dimensions are used as the calculation benchmark; if not, the minimum wall thickness on the path is selected. Guiding structural features that assist pressure transmission can significantly prolong the melt flow time in the thin-walled region. Without the identification of such features, traditional injection molding processes often misjudge the freezing timing of the runner, leading to premature cessation of pressure holding before the runner is frozen, causing shrinkage marks, or continued pressure application after the runner has already frozen, resulting in overfilling and residual internal stress near the gate.

[0031] While acquiring basic geometric information, the system simultaneously obtains melt temperature, holding pressure, and screw position data in real time. Filtering algorithms (such as Kalman filtering or moving average) are used to remove outliers from the original signal, generating a smooth pressure time-series curve and melt temperature data synchronized with it. This time-series synchronization ensures that the pressure load and thermal state data accurately correspond when analyzing any time slice in subsequent analyses, avoiding input errors to the calculation model caused by data acquisition delays or asynchrony.

[0032] S2. Based on the geometric parameters of the effective pressure transmission path and the structured process dataset, the time required for the effective pressure transmission path and the thick-walled region to reach the predetermined condensation state is calculated through thermodynamic analysis logic. This determines the key process time nodes and generates a process parameter set including a first holding pressure and a second holding pressure. The first holding pressure is a low pressure below the critical value for flash generation, and the second holding pressure is a high pressure to meet the feeding requirements of the thick-walled region.

[0033] Thermodynamic analysis logic refers to constructing a mathematical model of melt cooling within a specific geometric space based on the unsteady-state heat conduction principle of polymer materials and the real-time melt temperature and mold wall temperature difference. The predetermined condensation state refers to the physical critical state during the melt's transition from molten fluid to semi-solid or solid state, where its viscosity increases to the point where it can no longer respond to external pressure transmission or a skin with specific mechanical strength forms on its surface. During the calculation, the system substitutes the geometric parameters of the effective pressure transmission path (such as wall thickness and hydraulic diameter) into the heat balance equation, and combines this with the initial melt temperature from the structured process dataset to calculate the time required from the melt contacting the mold wall to reaching this critical state.

[0034] This analytical logic quantifies the differences in cooling rates across different geometric regions by solving the heat conduction equations under varying boundary conditions. Taking the aforementioned thin-walled reinforcing rib and thick-walled mounting boss locations as examples, due to the significant differences in heat dissipation conditions, the model calculates the time it takes for the thin-walled flow channel section to completely freeze and the time it takes for the thick-walled cavity core to solidify, respectively. Typically, the thin-walled location, due to its lower thermal resistance, reaches a freezing state earlier than the thick-walled location. This calculation quantifies the difference in solidification time between the two, and this difference constitutes the effective operating range available for subsequent pressure regulation strategies.

[0035] The critical process time points are the pressure switching moments determined based on the aforementioned condensation time calculations. The predetermined condensation state precisely defines the optimal physical window for pressure holding intervention. Specifically, this is characterized by a solidified layer with a certain shear yield strength forming on the surface of the melt in contact with the mold wall, capable of resisting high internal pressure without cracking. However, at the same time, the transmission channels within the effective pressure transmission path are not yet fully closed, and the core melt still maintains fluidity to allow for mass transfer. Accurately capturing this intermediate state of solid-liquid coexistence allows the control system to complete the feeding of the far-end thick-walled region before the flow channel closes.

[0036] The generation of process parameter sets, including a first holding pressure and a second holding pressure, aims to address the mechanical contradictions at different stages of the molding process. The first holding pressure is set to a low pressure to prevent the mold parting surface from elastically deforming under the melt pressure in the early stages of holding pressure, thus preventing it from being stretched open and generating flash. The second holding pressure is set to a high pressure to overcome the internal stress caused by volume shrinkage in thick-walled areas in the later stages of holding pressure, pressing sufficient melt into the cavity to compensate for the depressions caused by shrinkage. This pressure setting strategy utilizes the time dimension to balance the two spatially mutually constraining physical phenomena of preventing overflow at the mold parting surface and overcoming volume shrinkage depressions in thick-walled areas.

[0037] Optionally, S2 includes the following sub-steps S21-S24.

[0038] S21. Based on the preset melt rheological parameters and the geometric characteristics, calculate the maximum allowable pressure without flash as the first holding pressure, and calculate the minimum holding pressure to meet the feeding requirements of the thick-walled region as the second holding pressure.

[0039] S22. Based on the melt temperature in the structured process dataset and the geometric parameters of the effective pressure transmission path obtained from the geometric structural features, and combined with the second holding pressure and the preset material thermophysical parameters, calculate the skin safety time required for the effective pressure transmission path to form a skin that resists the second holding pressure, and the gate freezing time for the gate area to completely solidify.

[0040] Based on melt rheological parameters and geometric characteristics, the system can define the numerical boundaries between the first and second holding pressures. The upper limit of the first holding pressure is limited by the mold clamping force and the sealing performance of the parting surface. When the total expansion force generated by the fluid pressure in the mold cavity in the projection area of ​​the parting surface approaches the rated clamping force of the clamping mechanism, even a small gap expansion will lead to overflow. Therefore, the first holding pressure is set to a value lower than this critical expansion pressure. Conversely, the lower limit of the second holding pressure depends on the PVT (pressure-specific volume-temperature) characteristics of the melt during cooling in thick-walled areas. Only when the local pressure is sufficient to offset the specific volume shrinkage caused by the temperature drop can vacuum bubbles or surface depressions be avoided. Therefore, the second holding pressure is set to a value higher than this minimum compensation requirement.

[0041] The skin safety time refers to the time required for the melt on the inner wall of the effective pressure transmission path to cool from the contact mold surface until its solidified layer thickness grows sufficient to withstand the shear stress and radial expansion force generated by the second holding pressure. The formation of a condensed skin with sufficient mechanical strength along the effective pressure transmission path is a prerequisite physical condition for applying high-pressure compensation. If a high second holding pressure is applied too early before the skin safety time is reached, the not-fully-hardened, weak skin will undergo plastic yielding or rupture under the action of internal hydrostatic pressure. This will cause secondary mold expansion deformation or stress cracking in the originally designed thin-walled runner, thereby compromising the geometric accuracy of the runner and potentially introducing new flash risks.

[0042] The gate freezing time is determined by the initial melt temperature, the geometric dimensions of the gate area (such as the runner radius or rectangular thickness), and the material's thermal properties (such as thermal diffusivity and specific heat capacity). Heat is continuously conducted to the mold through the gate wall, causing the melt temperature at the center of the gate cross-section to gradually decrease over time. When the average temperature on this cross-section drops below the material's no-flow temperature, the macroscopic flowability of the polymer chain segments is lost, forming a solid plug that blocks pressure transmission. This time point defines the effective lifespan of the entire holding pressure process, marking the physical severance of the mass transfer channels inside and outside the mold cavity. After this point, any pressure applied by the screw can no longer compensate for the shrinkage inside the mold cavity.

[0043] Optionally, S22 includes the following sub-steps S221-S223.

[0044] S221. Obtain the shear yield strength of the injection molding material at the current mold temperature from the preset material thermophysical parameters, establish a mechanical equilibrium equation between the shear stress generated by the second holding pressure and the shear yield strength, solve the equation to obtain the minimum wall thickness required for the effective pressure transmission path to not break, and define it as the critical skin thickness.

[0045] S222. Based on the thermal diffusivity in the preset material thermal property parameters and the melt temperature, the cooling time required for the solidification front to advance from the mold wall to the critical skin thickness position is calculated using a one-dimensional unsteady thermal conduction equation, and the cooling time is defined as the skin safety time.

[0046] S223. Based on the geometry and thermal conductivity of the gate region, calculate the time required for the average melt temperature of the gate region to drop to the no-flow temperature of the injection molding material, and define the time as the gate freezing time.

[0047] The critical skin thickness refers to the minimum physical thickness of the solid layer formed by the cooling and solidification of the melt on the inner wall of the effective pressure transmission path, which can withstand the shear stress generated by the second holding pressure without plastic yielding or fracturing. This thickness is determined by establishing a mechanical equilibrium equation between shear yield strength and the second holding pressure; its physical essence is to find a threshold for structural stability. This threshold represents the critical point at which the effective pressure transmission path transforms from a simple fluid channel into a pressure vessel capable of bearing high-pressure loads, ensuring that the subsequently applied high pressure only acts on the melt feeding within the cavity, without causing secondary deformation of the channel wall or the generation of flash. The one-dimensional unsteady-state heat conduction equation plays a crucial role in the computational logic by transforming spatial geometric constraints into temporal process control variables. Since the solidification front (i.e., the liquid-solid interface) continuously advances from the mold's cold wall towards the melt center over time, this equation establishes a nonlinear mapping relationship between time and thickness using the material's thermal diffusivity. Through this equation, the system can accurately calculate the specific cooling time required for the solidification front to advance to the aforementioned critical skin thickness position, thereby determining the skin safety time. For example, the skin safety time... The calculation formula is as follows:

[0048] in, Where α is the critical skin thickness and α is the thermal diffusivity of the material. The solidification temperature of the material. The surface temperature of the mold. The initial temperature of the melt. This is the inverse error function.

[0049] The gate freezing time is calculated independently because the gate area, as the only channel connecting the mold cavity and the injection molding machine's runner system, typically has the smallest geometry and the fastest cooling rate. The gate freezing time acts as the absolute physical boundary condition for mass transfer throughout the feeding process, i.e., the "feeding cutoff point." The cessation of flow temperature is determined based on the material's rheological test data, referring to the critical temperature at which the melt viscosity rises sharply to the point where macroscopic flow is no longer possible. Once the average temperature of the gate area drops below this temperature, it means the feeding channel has been physically cut off. The system calculates this freezing time based on the gate geometry. The formula is shown below:

[0050] Where R is the characteristic radius or half-thickness of the gate. The temperature at which the flow stops is determined. C is a geometric factor related to the shape of the gate cross section (for example, it is usually smaller for circular gates and larger for slot gates).

[0051] S23. Perform thermodynamic criterion verification to determine whether the gate freezing time is greater than the sum of the skin layer safety time and the preset safety margin.

[0052] S24. If the verification passes, the skin safety time is defined as the pressure boosting start point, the gate freezing time is defined as the shrinkage compensation cutoff point, and the first holding pressure, the second holding pressure, and the key process time nodes are combined to generate the process parameter group; if the verification fails, a correction suggestion to adjust the process temperature or mold size is output, and an error is reported and the current molding cycle is terminated, wherein the key process time nodes include the pressure boosting start point and the shrinkage compensation cutoff point.

[0053] The specific logic of thermodynamic criterion verification is to compare the relative relationship between the time lengths of two key characteristics. The inequality verification logic executed by the system is as follows: ,in This represents a pre-set safety margin. Behind this inequality lies the existence of an effective molding process window, meaning that after sufficient structural strength has been established through the effective pressure transmission path, and before the gate is completely frozen and closed, there must objectively be a period of operable time. Only when this condition is met does it mean that there is a physically "safe and effective" time period that allows the high-pressure melt to be transmitted to the depths of the mold cavity through the unfrozen gate, without causing cracking or overflow due to excessively thin runner walls.

[0054] If the verification passes, the pressure increase start point is directly defined as the skin safety time calculated above. This moment corresponds to the critical timing of the transition from a low-pressure maintenance state to a flexible pressure increase state during the pressure holding process, indicating that the system determines the flow channel structure has the pressure-bearing capacity. The feeding termination point is defined as the calculated gate freezing time. This moment corresponds to the end of the high-pressure feeding stage and the transition to the pure cooling stage, marking the physical end of the external pressure feeding effect. These two time points together define the effective lifespan of the second pressure holding pressure effect.

[0055] If the verification fails, it means there is a fundamental contradiction in the current mold structure design or process conditions. For example, the gate size may be too small, causing it to freeze before the skin layer is formed, or the effective pressure transmission path wall thickness may be too thin, resulting in the skin layer forming speed being much slower than the gate solidification speed. In this case, there is no physically safe time window for applying high pressure to compensate for shrinkage. Therefore, the system prohibits entering the subsequent pressure holding execution step S3 to prevent the injection molding machine from forcibly executing invalid or potentially damaging pressurization actions, and outputs correction suggestions such as increasing the mold temperature to delay gate freezing or increasing the gate cross-sectional size. This reflects the method's pre-feasibility warning mechanism, avoiding the material waste and equipment damage risks caused by blind trial-and-error production.

[0056] S3. During the holding pressure stage of the injection molding process, the holding pressure is output in stages based on the key process time nodes to adjust the mold cavity pressure, and the flash and shrinkage marks are controlled by utilizing the time difference of melt solidification between the thick-walled region and the thin-walled region.

[0057] The holding pressure stage in injection molding refers to the process where, after the mold cavity has been filled, the injection molding machine screw continues to maintain a certain positive thrust to continuously replenish the melt into the mold cavity, compensating for the volume loss caused by polymer cooling and shrinkage. The main task of this stage is to maintain the hydrostatic pressure within the mold cavity, ensuring the geometric accuracy, surface replicance, and internal density of the injection molded part. For injection molded parts with complex geometries, the traditional single-stage constant pressure holding strategy cannot meet molding requirements due to uneven cooling caused by uneven wall thickness. Using a single high pressure, while meeting the shrinkage compensation needs of thick-walled areas, can easily cause pressure overload in thin-walled areas, resulting in flash; using a single low pressure, while avoiding flash, cannot provide sufficient shrinkage compensation power to eliminate shrinkage marks in thick-walled areas.

[0058] The time difference in melt solidification between thick-walled and thin-walled regions refers to the physical phenomenon that, under the same cooling conditions, due to the difference in the ratio of heat capacity to heat dissipation area, the thin-walled region (i.e., the effective pressure transmission path) establishes a solid skin layer significantly faster than the core of the thick-walled region. The control logic transforms this physical time difference into a pressure switching opportunity. Utilizing the characteristic that the thin-walled region establishes structural strength before the thick-walled region, the pressure holding process is divided into a "skin layer establishment period" and a "strong compensating period" on the time axis. The system identifies the time window when the skin layer thickness in the thin-walled region reaches a critical value but the flow channel has not yet frozen, serving as the control boundary for allowing a pressure jump.

[0059] Phased adjustment refers to the control system no longer outputting constant pressure commands, but instead generating pressure waveforms that vary over time based on the aforementioned key process time nodes. Through this adjustment method, the system achieves staggered pressure distribution within the same cycle: in the initial holding phase, before a sufficient solidification layer has formed in the thin-walled region, the system outputs limited low pressure, primarily to maintain melt contact with the mold wall and prevent overflow; in the later holding phase, once a condensed skin capable of resisting high pressure has been established in the thin-walled region, the system rapidly increases the pressure to the level required for shrinkage compensation, utilizing the remaining window before the runner freezes to forcefully compact the still molten thick-walled regions. This sequential division of labor allows the two process objectives—suppressing flash and eliminating shrinkage marks—which have diametrically opposed pressure requirements, to be achieved simultaneously.

[0060] Optionally, S3 includes the following sub-steps S31-S36.

[0061] S31. During the period from the start of the pressure holding to the time corresponding to the safe time of the skin layer, output the first pressure holding pressure and maintain it to keep the melt in contact with the mold wall and wait for the effective pressure transmission path to establish the condensation skin layer.

[0062] S32. At the moment when the injection molding process reaches the safe time corresponding to the skin layer, the output holding pressure is controlled according to the preset pressure rise rate, so that the cavity pressure linearly transitions from the first holding pressure to the second holding pressure, so as to avoid pressure shock damaging the condensed skin layer in the effective pressure transmission path.

[0063] During the period from the start of the holding pressure to the safe time corresponding to the skin layer, the system outputs a low initial holding pressure. Its core function is to establish a structural foundation capable of withstanding high pressure. At this time, although the low pressure is insufficient to completely compensate for the volume shrinkage of the thick-walled region, it is sufficient to maintain close contact between the outer surface of the melt and the mold cavity wall, ensuring that the heat transfer process continues efficiently. During this stage, the melt within the effective pressure transmission path is in the critical period of skin layer growth. The solidified layer gradually thickens from the interface in contact with the cold mold wall towards the center of the flow channel, but it has not yet reached the mechanical strength required to withstand subsequent high-pressure compensation.

[0064] The low-pressure maintenance state must be strictly maintained until the calculated safe time for the skin layer is reached. If the low pressure is prematurely terminated and switched to high pressure before the skin layer thickness reaches the critical value, the not-yet-fully-solidified layer will crack or plastically yield under the action of internal hydrostatic pressure, causing unexpected secondary expansion of the flow channel cross-section, which in turn leads to overflow or stress cracking at the parting surface. When the injection molding process reaches the moment corresponding to the skin layer safe time, a linear transition rather than a step-like abrupt pressure change is adopted to eliminate the pressure shock caused by the instantaneous response of the hydraulic system. A step-like pressure change will generate stress waves similar to the water hammer effect inside the fluid. This transient impact load can easily exceed the strength limit of the newly formed solidified skin layer, leading to the generation of microcracks in the skin layer.

[0065] Optionally, a ramp control strategy is adopted in sub-step S32: The control system generates a pressure command that increases linearly with time based on a preset slope. The preset slope is less than the stress relaxation rate of the condensation layer within the effective pressure transmission path, so as to ensure that the condensation layer within the effective pressure transmission path remains intact during the pressure increase process.

[0066] Ramp control strategy refers to a control system that uses interpolation algorithms to transform a step change in the pressure setpoint into a series of continuous commands with small time increments. Polymer materials exhibit viscoelastic properties, and their stress relaxation rate reflects the ability of the material's molecular chains to dissipate internal stress through conformational rearrangement after being subjected to force. When the pressure rise rate is less than the material's stress relaxation rate, it means that the external load is applied slower than the molecular chain's adjustment speed. From a microrheological perspective, this matched loading rate allows the polymer chain segments in the condensed skin sufficient time to adapt to the new stress state through deentanglement and slippage, thus avoiding excessive accumulation of elastic potential energy and ensuring that the skin maintains structural integrity during pressure increase, preventing brittle fracture.

[0067] S33. Output the second holding pressure and maintain it, and use the window period when the gate area has not yet frozen to replenish the thick-walled area until the time corresponding to the gate freezing time is reached or the effective pressure transmission path is blocked.

[0068] S34. During the output of the second holding pressure, the axial movement speed of the injection molding machine screw is collected in real time.

[0069] S35. If it is detected that the axial movement speed of the screw is lower than a preset micro-motion threshold during the process of maintaining the second holding pressure, it is determined that the gate area or the effective pressure transmission path has been frozen in advance.

[0070] S36. When it is determined that the gate area or the effective pressure transmission path has been frozen in advance, the output of the second holding pressure is immediately terminated and the cooling stage is entered. At the same time, the injection molded part in the current production cycle is marked as having internal shrinkage defects.

[0071] In stage S33, the high-pressure output of the second holding pressure provides the driving potential energy needed to overcome the viscous resistance of the melt and the shrinkage stress in the thick-walled region, ensuring that the melt can be pressed deep into the cavity to fill the gaps left by cooling shrinkage. The window period is defined on the time axis as the interval between the end of the skin safety time and the arrival of the gate freezing time; this is the last period during which the mold cavity and the injection molding machine runner system maintain fluid communication. During this period, the flow status of the runner can be accurately determined by monitoring the axial movement speed of the screw. According to the law of conservation of mass, the axial advance speed of the screw is proportional to the volumetric flow rate of the melt injected into the mold cavity; as long as the screw continues to advance, it means that the melt is continuously entering the mold cavity for shrinkage compensation.

[0072] The micro-motion threshold is a near-zero speed extreme. When the monitored screw speed is below this threshold, it indicates that although the screw is under hydraulic thrust, it can no longer push the melt in front, meaning the physical channel has been completely blocked by solidified cold material. Once premature freezing is detected, the system immediately terminates the holding pressure and enters the cooling stage. This loss prevention mechanism avoids the injection molding machine from continuing to do useless work when the runner is blocked, preventing stress concentration or equipment damage near the gate due to overpressure. At the same time, the system automatically marks the product of this batch with internal shrinkage defects. This marking data is not only used for subsequent scrap sorting, but also serves as an important feedback signal input to the process database, informing the control algorithm that the current process parameters do not cover the entire shrinkage compensation process and need to be used as the basis for parameter correction in the next production cycle.

[0073] S4. After the cooling stage of the injection molded part is completed, inspect the finished quality of the injection molded part, and reverse the critical process time node or the first holding pressure and the second holding pressure according to the defect type, and update the process parameter group for the next production cycle.

[0074] The reason for selecting the end of the cooling phase for inspection is that by this time, the injection molded part has completed the entire thermal shrinkage process, and its geometry and surface morphology have reached a stable state. Polymer materials undergo non-linear volume shrinkage during the cooling process from a molten state to a solid state. If inspection is performed immediately after demolding, residual heat remains inside the product, and shrinkage is not yet complete; the depth of shrinkage marks or the degree of warpage may not be fully apparent. Data collected at this time cannot accurately reflect the final product's quality and is highly susceptible to misjudgment of defect levels. Only after the injection molded part has fully cooled and solidified can the surface data acquired by the vision inspection system or contour measuring instrument be accurate and reliable as a basis for quality assessment.

[0075] The reverse correction mechanism refers to a closed-loop logical process in which the control system infers deviations in process parameter settings based on the defect characteristics of the end product. The system has a pre-built causal mapping database between defect types and process parameters, constructed based on rheological principles. Specifically, when a flash defect is detected, the system maps it to an excessively high first holding pressure or insufficient skin safety time, because this indicates that an effective seal has not yet been formed at the mold parting surface or the clamping force has been breached. When a shrinkage mark defect is detected, the system maps it to an insufficient second holding pressure or insufficient compensation duration, because this indicates that the melt has failed to effectively compensate for volume shrinkage. This logical mapping allows the system to accurately pinpoint the specific process parameter causing the defect based on its specific defect characteristics.

[0076] Updating the process parameter set for the next production cycle demonstrates the method's adaptive adjustment capability in response to changes in the production environment. During continuous production, factors such as batch fluctuations in raw materials, diurnal variations in ambient temperature, and decreased efficiency due to scaling in the mold cooling water system can all cause a slow drift in actual molding conditions. By feeding back the quality data of the current mold cycle to the control model and correcting the parameters for the next cycle, the system achieves a dynamic optimization through iterative cycles. This mechanism automatically compensates for the cumulative errors caused by these disturbances, ensuring that the process window always adjusts to changes in actual production conditions, thereby maintaining consistent product quality in long-cycle unmanned production.

[0077] Optionally, S4 includes the following sub-steps S41-S44.

[0078] S41. Acquire the finished image of the injection molded part, detect the flash thickness at the parting surface position corresponding to the effective pressure transmission path, and the shrinkage depth of the surface of the thick-walled area.

[0079] S42. If the burr thickness exceeds the preset first defect threshold, then in the next production cycle, the time margin is increased or the second holding pressure is reduced based on the skin safety time.

[0080] S43. If the depth of the shrinkage mark exceeds the preset second defect threshold, the second holding pressure is increased in the next production cycle, or the mold temperature is adjusted when it is determined that the gate area is frozen prematurely.

[0081] S44. The corrected key process time nodes, the first holding pressure, and the second holding pressure are fed back to the structured process dataset to update the original process parameter settings, and the updated process parameter settings are used to guide the injection molding of the next production cycle.

[0082] The detection points need to be precisely located at the parting surface and the surface of the thick-walled area corresponding to the effective pressure transmission path because these two locations represent the upper mechanical limit and the lower shrinkage limit of the molding process window, respectively. The parting surface corresponding to the effective pressure transmission path is the area with the most direct pressure transmission and the least fluid resistance within the mold cavity. This area is most prone to exceeding the clamping force limit due to excessive local pressure, representing the process limit of the system in preventing overflow. On the other hand, the surface of the thick-walled area is where the most heat accumulates and the largest volume shrinkage occurs. This area is most prone to depressions due to insufficient shrinkage pressure or interruption of the shrinkage path, representing the process limit of the system's filler density.

[0083] To address flash defects, the physical principle behind extending the safety time of the skin layer lies in trading time for structural strength. This involves increasing the duration of low-pressure maintenance, allowing a thicker, cured skin layer to grow on the inner wall of the effective pressure transmission path. This thickened skin layer forms a rigid shell capable of resisting radial expansion forces, preventing subsequent high pressure from pushing open the mold parting surface. Reducing the second holding pressure directly decreases the hydrostatic pressure load acting on the mold cavity wall, ensuring that the total mold expansion force returns to within the elastic deformation allowable range of the injection molding machine's clamping mechanism, thereby eliminating the risk of flash.

[0084] To address shrinkage defects, the preferred strategy is to increase the second holding pressure. This is because, while the runner is still in a molten and connected state, increasing the pressure gradient directly increases the melt injection volume per unit time, effectively compensating for volume shrinkage. However, when the system determines that the gate area has frozen prematurely, it means that the feeding channel has been physically blocked by the solidified polymer. In this case, simply increasing the hydraulic power of the injection molding machine cannot achieve melt mass transfer. Therefore, it is necessary to adjust the mold temperature, slowing down the melt cooling rate by increasing the mold temperature, thus thermodynamically delaying the gate freezing moment and reopening an effective time window to allow the melt to pass through.

[0085] The corrected parameters are fed back to the structured process dataset, enabling the closed-loop control system to achieve memory iteration through data updates. This step involves more than just recording historical data; it uses the corrected key process time points and pressure parameters as new initial boundary conditions, inputting them into the control model for the next production cycle. This mechanism ensures that the next production cycle inherits the optimization results, allowing the control strategy to dynamically adapt to minor shifts in the production environment and preventing the same defects from recurring in continuous production.

[0086] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0087] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0088] 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method of injection molding adaptive pressure maintenance control, the method comprising: include: S1. Collect the geometric structural features of the injection molded part and the real-time process data of the injection molding process, and clean and structure the real-time process data to obtain a structured process dataset containing pressure time sequence curves and melt temperature; wherein, the geometric structural features at least characterize the thick-walled region, the thin-walled region and the effective pressure transmission path between the two in the injection molded part. S2. Based on the geometric parameters of the effective pressure transmission path and the structured process dataset, the time required for the effective pressure transmission path and the thick-walled region to reach the predetermined condensation state is calculated through thermodynamic analysis logic. This determines the key process time nodes and generates a process parameter set including a first holding pressure and a second holding pressure. The first holding pressure is a low pressure below the critical value for flash generation, and the second holding pressure is a high pressure to meet the feeding requirements of the thick-walled region. S3. During the holding pressure stage of the injection molding process, the holding pressure is output in stages based on the key process time nodes to adjust the mold cavity pressure, and the flash and shrinkage marks are controlled by utilizing the time difference between the melt solidification of the thick-walled region and the thin-walled region. S4. After the cooling stage of the injection molded part is completed, inspect the finished quality of the injection molded part, and reverse the critical process time node or the first holding pressure and the second holding pressure according to the defect type, and update the process parameter group for the next production cycle.

2. The adaptive pressure holding control method for injection molding according to claim 1, characterized in that, S1 includes the following sub-steps: S11. Establish a digital model of the injection molded part, identify thick-walled and thin-walled regions, and calculate the ratio of flow length to wall thickness of the thick-walled and thin-walled regions; S12. Determine the flow channel connectivity from the gate to the thick-walled region, identify whether there are flow guiding structural features for assisting pressure transmission, and determine the geometric parameters of the effective pressure transmission path based on the identification results; S13. Real-time acquisition of melt temperature, holding pressure and screw position data, and the use of filtering algorithms to remove outliers and noise, generating the filtered pressure time-series curve and the melt temperature synchronized with the pressure time-series curve.

3. The adaptive pressure holding control method for injection molding according to claim 1, characterized in that, S2 includes the following sub-steps: S21. Based on the preset melt rheological parameters and the geometric features, calculate the maximum allowable pressure without flash as the first holding pressure, and calculate the minimum holding pressure to meet the feeding requirements of the thick-walled region as the second holding pressure. S22. Based on the melt temperature in the structured process dataset, and obtaining the geometric parameters of the effective pressure transmission path from the geometric structural features, and combining the second holding pressure and the preset material thermophysical parameters, calculate the skin safety time required for the effective pressure transmission path to form a skin that resists the second holding pressure, and the gate freezing time for the gate area to completely solidify. S23. Perform thermodynamic criterion verification to determine whether the gate freezing time is greater than the sum of the skin layer safety time and the preset safety margin; S24. If the verification passes, the skin safety time is defined as the pressure increase start point, the gate freezing time is defined as the shrinkage compensation end point, and the first holding pressure, the second holding pressure, and the key process time nodes are combined to generate the process parameter group. If the verification fails, a correction suggestion to adjust the process temperature or mold size will be output, and an error will be reported and the current molding cycle will be terminated. The key process time nodes include the pressure boosting start point and the shrinkage compensation end point.

4. The adaptive pressure holding control method for injection molding according to claim 3, characterized in that, S22 includes the following sub-steps: S221. Obtain the shear yield strength of the injection molding material at the current mold temperature from the preset material thermophysical parameters, establish the mechanical equilibrium equation between the shear stress generated by the second holding pressure and the shear yield strength, solve the equation to obtain the minimum wall thickness required for the effective pressure transmission path to not break, and define it as the critical skin thickness. S222. Based on the thermal diffusivity in the preset material thermal property parameters and the melt temperature, the cooling time required for the solidification front to advance from the mold wall to the critical skin thickness position is calculated using a one-dimensional unsteady thermal conduction equation, and the cooling time is defined as the skin safety time. S223. Based on the geometry and thermal conductivity of the gate region, calculate the time required for the average melt temperature of the gate region to drop to the no-flow temperature of the injection molding material, and define the time as the gate freezing time.

5. The adaptive pressure holding control method for injection molding according to claim 3, characterized in that, S3 includes the following sub-steps: S31. During the period from the start of the pressure holding to the time corresponding to the safe time of the skin layer, output the first pressure holding pressure and maintain it to keep the melt in contact with the mold wall and wait for the effective pressure transmission path to establish the condensed skin layer; S32. At the moment when the safe time of the skin layer is reached during the injection molding process, the output holding pressure is controlled according to the preset pressure rise rate, so that the cavity pressure linearly transitions from the first holding pressure to the second holding pressure, so as to avoid pressure shock damaging the condensed skin layer in the effective pressure transmission path; S33. Output the second holding pressure and maintain it, and use the window period when the gate area has not yet frozen to replenish the thick-walled area until the time corresponding to the gate freezing time is reached or the effective pressure transmission path is blocked.

6. The adaptive pressure holding control method for injection molding according to claim 5, characterized in that, S3 further includes the following sub-steps: S34. During the output of the second holding pressure, the axial movement speed of the injection molding machine screw is collected in real time; S35. If it is detected that the axial movement speed of the screw is lower than a preset micro-motion threshold during the process of maintaining the second pressure holding pressure, it is determined that the gate area or the effective pressure transmission path has been frozen in advance. S36. When it is determined that the gate area or the effective pressure transmission path has been frozen in advance, the output of the second holding pressure is immediately terminated and the cooling stage is entered. At the same time, the injection molded part in the current production cycle is marked as having internal shrinkage defects.

7. The adaptive pressure holding control method for injection molding according to claim 5, characterized in that, The slope control strategy is adopted in sub-step S32: The control system generates a pressure command that increases linearly with time based on a preset slope. The preset slope is less than the stress relaxation rate of the condensation layer within the effective pressure transmission path, so as to ensure that the condensation layer within the effective pressure transmission path remains intact during the pressure increase process.

8. The adaptive pressure holding control method for injection molding according to claim 3, characterized in that, S4 includes the following sub-steps: S41. Acquire the finished image of the injection molded part, detect the flash thickness at the parting surface position corresponding to the effective pressure transmission path, and the shrinkage depth of the surface of the thick-walled area; S42. If the burr thickness exceeds the preset first defect threshold, then in the next production cycle, the time margin is increased or the second holding pressure is reduced based on the skin safety time; S43. If the depth of the shrinkage mark exceeds the preset second defect threshold, the second holding pressure is increased in the next production cycle, or the mold temperature is adjusted when it is determined that the gate area is frozen in advance. S44. The corrected key process time nodes, the first holding pressure, and the second holding pressure are fed back to the structured process dataset to update the original process parameter settings, and the updated process parameter settings are used to guide the injection molding of the next production cycle.

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