Injection molding process parameter initial setting method based on cavity pressure curve characteristic analysis

Abstract

The invention discloses an injection molding process parameter initial setting method based on cavity pressure curve characteristic analysis, and relates to the field of injection molding process parameter setting. According to the method, pressure curve data in a mold cavity and a product appearance detection result are collected in real time in the mold testing process, key feature point information including a pressure building starting point, a pressure sudden change point, a V / P switching inflection point, a pressure maintaining platform interval and a cooling end point is recognized, and association rules of technological parameters and quality defects are established; and key parameters such as injection speed, injection pressure, dwell pressure, dwell time, cooling time and the like are sequentially adjusted, so that systematic setting of initial process conditions is realized. The method has the advantages of being high in data driving performance, clear in debugging process, high in interpretability and the like, the injection molding parameter adjusting efficiency can be effectively improved, dependence on historical sample data or complex modeling is avoided, the method is suitable for mold testing scenes of products of different structures and multiple types, the mold testing period is short, the trial and error cost is low, and good engineering practicability and application and popularization value are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of injection molding, and particularly relates to a method for initially setting injection molding process parameters based on the analysis of cavity pressure curve characteristics. Background Art

[0002] Injection molding, as a representative molding process in the field of polymer material processing, its products are widely used in fields such as automotive parts, electronic products, and medical devices. The molding quality of injection molded products is jointly affected by multiple process parameters, including plasticizing temperature, material storage position, injection speed, injection pressure, V / P switching position, holding pressure, holding time, and cooling time. There are complex non-linear coupling relationships among these process parameters, and they have a direct impact on key indicators such as product weight, dimensional accuracy, warpage deformation, and surface quality.

[0003] In the actual production process, the setting of injection molding process parameters usually depends on the experience of on-site engineering and technical personnel. By repeatedly trial-molding, adjusting parameters, and observing the appearance quality results of the products, the process parameter window that meets the production requirements is gradually determined. However, the following main deficiencies exist in this process:

[0004] (1) The trial-molding and debugging process highly depends on personnel experience, lacks a systematic adjustment path and quantitative judgment standard, resulting in low debugging efficiency, long cycle, and high trial-and-error cost;

[0005] (2) The utilization degree of real-time data in the injection molding process during parameter setting is relatively low, and the process information contained in key process signals such as cavity pressure curves cannot be effectively extracted;

[0006] (3) Although some existing parameter recommendation methods based on simulation analysis or data modeling have certain guiding value, they usually do not integrate the real-time feedback process on the trial-molding site and rely strongly on large-scale historical data, resulting in problems such as poor generalization ability and insufficient engineering adaptability.

[0007] At the same time, the cavity pressure curve generated during the injection molding process, as a process signal that can directly reflect the dynamic characteristics of melt filling and the change of molding quality, existing research has shown that there is a high correlation between key feature points (such as the starting point of pressure building, the inflection point of V / P switching, etc.) in the pressure curve and quality indicators such as product defect types and dimensional deviations. However, the existing technology still lacks a systematic method that takes such feature points as the core and combines product quality inspection data to guide the optimization and setting of process parameters, making it difficult to achieve the unity of regularization, interpretability, and on-site practicability in the parameter adjustment process.

[0008] Therefore, there is an urgent need to propose a method that makes full use of the characteristic information of the cavity pressure curve, combines the results of the appearance quality inspection of the product, and scientifically guides the initial setting of process parameters in the trial mold stage, aiming to improve the injection molding process debugging efficiency, reduce the trial mold and error correction costs, and ensure the consistency of molding quality and production stability. Summary of the Invention

[0009] Aiming at the problems existing in the process of setting injection molding process parameters, such as relying on experience, low debugging efficiency, and insufficient utilization of process data, the present invention proposes an initial setting method of injection molding process parameters based on the analysis of cavity pressure curve characteristics, aiming to establish a scientific process for adjusting process parameters in the trial mold stage, using the characteristic data of the cavity pressure curve in the actual trial mold process to guide the setting of process parameters, reducing the trial mold and error correction costs, and improving the stability of molding quality and production debugging efficiency.

[0010] The core of the present invention is to collect the pressure curve data in the mold cavity during the trial mold process, and combine the results of the appearance quality inspection of the product to extract key characteristic points with engineering significance, such as the starting point of pressure build-up, pressure mutation point, V / P switching inflection point, etc. Based on the response patterns of these characteristic points, judge the rationality of the current process parameters, and guide the setting of key processes including injection speed, injection pressure, holding pressure parameters, cooling time, etc., and gradually construct an initial process parameter combination that meets the quality requirements. The method includes the following contents:

[0011] First, in combination with the injection molding product structure and raw material type, set a reasonable plasticizing temperature according to the supplier's recommended value. At the same time, according to parameters such as product weight, screw diameter, cushion length, and material density, use the following formula to calculate and set the material storage position:

[0012]

[0013] where L is the material storage position, L1 is the cushion length, M is the product weight, D is the screw diameter, and ρ is the material density. This calculation method can effectively avoid the problems of insufficient material storage or over-limited metering.

[0014] After completing the initial parameter setting, conduct the first trial mold with low-speed injection and no holding pressure. The system collects and analyzes the cavity pressure curve and screw displacement curve, identifies the pressure build-up point (L2) and pressure mutation point (L3), and calculates:

[0015] V / P conversion position L vp = L3 – L2

[0016] The first-stage injection conversion position L z = L - L2

[0017] For the setting of subsequent injection speed segmented control strategies.

[0018] The injection speed adopts a two-stage control strategy. The system defaults the first-stage speed to a fixed value, and the second stage starts from the maximum injection speed to gradually try out the mold, identifying whether there are peak fluctuations in the pressure curve. If a peak appears, the speed is decreased in 10% steps until the peak disappears. Subsequently, fine-tuning is continued in combination with product surface defects such as silver streaks or flow marks. Finally, the speed combination when there are no peaks and no defects is confirmed as the standard injection speed.

[0019] At the initial stage of setting the injection pressure, it adopts a decreasing method from high to low. After trying out the mold, observe whether the product shows overpressure characteristics such as sintering and jetting. The holding pressure increases from low to high. The system judges in real time whether a plateau area is established in the pressure curve and sets it in combination with the analysis of sink mark defects. The holding time gradually increases (in seconds as the step) after the holding pressure is set. By judging the dimensional integrity and warpage deformation of the product, a suitable holding time range is determined.

[0020] The cooling time increases by 1 second per round starting from 5 seconds. Judge the cooling sufficiency by whether the end point of the pressure curve returns to zero, and comprehensively judge in combination with the dimensional stability of the product to set the final cooling time.

[0021] Through the above steps, the initial setting of the key process parameters of injection molding including plasticizing temperature, material storage position, V / P switching position, injection speed, injection pressure, holding pressure, holding time, and cooling time is completed item by item. There is a logical path of sequential adjustment and gradual optimization among the parameters, and the parameter combination can be used for the final verification in the mold trial stage and the construction of the process window.

[0022] Preferably: The cavity pressure curve is collected by a pressure sensor embedded in the mold, and the sampling frequency of the sensor is not less than 100Hz to ensure the accurate identification and analysis of key feature points.

[0023] Further preferably: The method can be integrated through an edge computing module or an injection molding equipment control system to realize the real-time identification of the characteristics of the cavity pressure curve during the mold trial process and the output of parameter adjustment suggestions, and assist engineers to complete the process parameter setting decision through a human-machine interaction interface.

[0024] Compared with the prior art, the present invention has the following remarkable advantages in terms of method structure, parameter setting logic, and engineering adaptability:

[0025] 1. Establish a process setting mechanism based on process data to improve the scientificity and standardization of debugging. By collecting the cavity pressure curve in real time and identifying typical feature points, the present invention establishes a logical relationship between process parameters and product quality, getting rid of the traditional setting method that relies on experience and repeated trial and error, and realizing the scientific and structured injection molding parameter adjustment process.

[0026] 2. The parameter adjustment path is clear, the judgment basis is quantifiable, and it has high interpretability. The adjustment of process parameters is judged item by item according to the pressure curve response and appearance quality results, clarifying the action paths of parameters such as injection speed, V / P switching, and holding pressure on the molding quality, which is convenient for on-site engineering personnel to understand and apply.

[0027] 3. Improve the efficiency of mold trial and debugging, and reduce material waste and labor costs. The present invention closely combines each parameter setting process with the feedback of pressure characteristics, effectively reducing the number of mold trial rounds, shortening the debugging cycle, improving the quality consistency in the initial stage of molding, and significantly reducing the comprehensive production preparation cost.

[0028] 4. It has a wide range of applications and good potential for engineering promotion. The proposed method does not rely on historical sample data or complex modeling, is applicable to the mold trial scenarios of molds with different structures and various types of products, has good versatility and engineering reproducibility, and can be applied on a large scale in the injection molding industry.

[0029] In summary, the present invention provides a scientific, systematic, and efficient parameter adjustment path by constructing an initial setting method for injection molding process parameters based on the analysis of cavity pressure curve characteristics, significantly improving the debugging efficiency and quality control ability in the injection molding process, and having broad engineering practical value. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the present invention, the embodiments of the present invention are further described in conjunction with the drawings, where:

[0031] Figure 1 is a flowchart of an initial setting method for injection molding process parameters based on the analysis of cavity pressure curve characteristics provided by the present invention;

[0032] Figure 2 is a schematic diagram for determining the V / P switching position provided by the present invention;

[0033] Figure 3 is a schematic diagram of the relationship between the cavity pressure curve and the injection speed provided by the present invention;

[0034] Figure 4 is a schematic diagram of the relationship between the cavity pressure curve and the holding pressure provided by the present invention;

[0035] Figure 5 is a schematic diagram of the relationship between the cavity pressure curve and the holding time provided by the present invention;

[0036] Figure 6 is a schematic diagram of the relationship between the cavity pressure curve and the cooling time provided by the present invention. Detailed Embodiments

[0037] For the convenience of further understanding the technical solution of the present invention, the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments. This embodiment is only used to clarify the principle and implementation path of the present invention, and does not limit the protection scope of the present invention.

[0038] As Figure 1 shown, the present invention provides an initial setting method for injection molding process parameters based on the analysis of cavity pressure curve characteristics. This method identifies key process feature points through the cavity pressure curve data collected during the mold trial and the product appearance quality results, and adjusts the key injection molding process parameters based on the feature points and defect information to achieve a scientific and controllable parameter setting process, which is applicable to the mold trial and parameter adjustment link during the injection molding process.

[0039] In the embodiment described in the present invention, it is necessary to obtain the cavity pressure curve by arranging pressure sensors in the mold cavity at the mold trial site, and synchronously conduct product appearance detection, including manual or system detection of defect items such as short shot, flash, silver streaks, dimensional error, warpage, etc., as the feedback basis for subsequent parameter adjustment.

[0040] The process parameters involved in this method include: plasticizing temperature, screw position, V / P switching position, injection speed, injection pressure, holding pressure, holding time, cooling time, etc. The process setting process follows the principle of sequential adjustment and gradual verification, that is: after the current process parameters are set, they are used as the input basis for the next round of parameter adjustment until all parameters are set.

[0041] Before the mold trial, the plasticizing temperature is set according to the recommended range of the raw material supplier and on-site process experience; the screw position is calculated based on the cushion length of the injection molding machine, product weight, screw diameter, and material density. The formula is as follows:

[0042]

[0043] where L is the screw position, L1 is the cushion length, M is the product weight, D is the screw diameter, and ρ is the material density. Through this calculation method, a reasonable metering range can be preset to avoid filling failure caused by insufficient screw position.

[0044] After the plasticizing temperature and screw position are set, the actual parameter adjustment stage is entered. First, the V / P switching position is adjusted. The system performs the first round of mold trial under the conditions of default low-speed injection (about 20% of the maximum injection speed), no holding pressure, and no V / P switching. Combining the mutation point position of the cavity pressure curve and the screw position curve, the system automatically identifies the V / P switching inflection point. Specifically, as Figure 2 shown, the screw position at the mutation point is set as the V / P switching position, and at the same time, the screw position corresponding to the pressure build-up point is recorded as the switching position of the first-stage injection speed. Its expression is:

[0045] L vp= L3 – L2, L z = L - L2

[0046] Wherein, L vp represents the V / P conversion position, L3 represents the screw position when the pressure value changes suddenly, L2 represents the screw position when the pressure build-up point occurs, L represents the initial screw position, and L z represents the first-stage injection conversion position.

[0047] Subsequently, the injection speed is set. The injection speed is controlled in two stages: the first stage is a lower injection speed to ensure smooth filling, and the second stage is a high injection speed to improve the molding efficiency. During the trial molding process, keep the speed of the first stage unchanged, set the speed of the second stage as the maximum injection speed in the system, and execute the trial molding to collect the pressure curve, as Figure 3 shown. If a pressure spike appears, it indicates that the speed is too high. The injection speed of the second stage should be gradually reduced in a 10% decrement until the pressure curve spike disappears. At this time, it is set as the standard injection speed. Further observe the appearance of the product at this speed. If there are flow marks or silver streaks, reduce the speed again until there are no obvious defects, and finally set it as the optimized injection speed.

[0048] Next, adjust the three parameters of injection pressure, holding pressure, and holding time. Setting the injection pressure too low may result in not reaching the target speed, while setting it too high may damage the mold. Initially, adopt a strategy of gradually decreasing from high to low (decreasing by about 5% each time), and observe whether there are signs of burning or oversaturation on the product surface to comprehensively judge the optimal injection pressure.

[0049] The holding pressure is adjusted by trial molding from low to high, increasing by about 5% or 10% at each step. By detecting whether there is a sink mark on the product (as Figure 4 shown), decide whether to continue increasing the pressure. The appropriate holding pressure should be able to eliminate the sink mark while maintaining a good pressure platform.

[0050] The adjustment of the holding time is set according to the dimensional stability and shrinkage trend of the product. On the premise that the holding pressure has been optimized, gradually extend the holding time (as Figure 5 shown), and observe whether the product still has shrinkage or warping until the dimensions meet the requirements.

[0051] Finally, adjust the cooling time. Set the initial cooling time as 5 s, increase by 1 s for each round of trial molding, and the system identifies whether the end point of the cavity pressure curve stably returns to zero (as Figure 6 shown). When there is no residual pressure at the end of the pressure curve and the product dimensions are stable, the corresponding cooling time is the standard cooling time.

[0052] Through the item-by-item confirmation and feedback verification of the above process parameters, an initial injection molding process parameter scheme that conforms to the current mold structure and material conditions is formed. Subsequently, multiple rounds of debugging can be carried out based on this scheme to further expand the process window and improve production adaptability.

[0053] The method of the present invention has been applied and verified in the trial mold debugging of multiple typical products. The test results show that this method can effectively reduce the trial mold cycle, reduce the number of parameter adjustments, improve the molding stability and quality consistency, and has good engineering practicability and promotion prospects.

Claims

1. A method for initializing injection molding process parameters based on cavity pressure curve characteristic analysis, characterized in that: The steps include: (1) Combine the injection molding product structure and raw material type, set the plasticizing temperature according to the raw material supplier's recommended value, and calculate the material storage position based on material density, product weight, screw diameter and material pad length; (2) During the mold trial, low-speed injection, no pressure holding, and no V / P switching settings are performed, and the pressure curve in the mold cavity and the screw position curve are collected in real time to identify the pressure building starting point and the pressure mutation point, and calculate the first-stage injection speed conversion position and V / P switching position; (3) A two-stage injection speed setting strategy is adopted, where the first-stage speed is kept unchanged and the second-stage speed is gradually adjusted from high to low. The standard injection speed combination is determined by judging whether there are peaks in the pressure curve and whether there are defects such as silver streaks or flow marks on the surface of the product. (4) Based on the set injection speed, adjust the injection pressure from high to low, and judge whether the product has problems such as jetting and sintering, and set the appropriate injection pressure; (5) Adjust the holding pressure and holding time in sequence. The holding pressure is set from low to high and optimized by judging the establishment of the pressure curve platform and whether there are shrinkage marks on the product. The holding time is set by gradually extending it and combining the dimensional stability and warpage trend of the product. (6) After completing the above parameter settings, gradually increase the cooling time from the set initial value, and determine the final cooling time by judging whether the end of the cavity pressure curve returns to zero and combining the dimensional stability of the product; (7) Finally, the initial injection molding process parameter combination is formed and used for subsequent mold trial debugging and process window construction.

2. The method for initializing injection molding process parameters based on cavity pressure curve characteristic analysis according to claim 1, characterized in that: The V / P switching position and the first-stage injection speed conversion position are respectively obtained by the screw position difference between the pressure building point and the pressure mutation point.

3. The method for initializing injection molding process parameters based on cavity pressure curve characteristic analysis according to claim 1, characterized in that: The cavity pressure curve is collected by a pressure sensor embedded in the mold cavity, and the sensor sampling frequency is not less than 100 Hz to ensure the timeliness and accuracy of feature point recognition.

4. The method for initializing injection molding process parameters based on cavity pressure curve characteristic analysis according to claim 1, characterized in that: The injection speed adopts a two-stage control strategy. During the second stage of injection speed adjustment, the peak response of the pressure curve and the surface defects of the product are comprehensively judged to determine the optimal speed setting without peaks and silver streaks.

5. The method for initializing injection molding process parameters based on cavity pressure curve characteristic analysis according to claim 1, characterized in that: The method can be integrated into the injection molding equipment control system or edge computing module, and can present the characteristic points of the cavity pressure curve, analysis and judgment results, and recommended parameter adjustment suggestions in real time through the human-computer interaction interface, so as to assist on-site engineering and technical personnel in implementing injection molding process optimization.

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