A method and control device for controlling blow molding machines to reduce defect rates

Abstract

This invention relates to the field of blow molding air pressure control, specifically to a blow molding machine control method and device for reducing defect rates. The method obtains the temperature distribution consistency at the current moment based on the differences in temperature data between different contact points on the inner wall of the bottle mold at previous moments. It analyzes the air pressure in the blow molding machine's air path and the internal air pressure of the preform during the blow molding process to obtain a first blow molding progress index for the current moment. Based on the correlation between the changes in the preform's internal air pressure at previous moments and the extension speed of the tension rod, as well as the extension length and speed of the tension rod at the current moment, it obtains a second blow molding progress index for the current moment, thereby obtaining the current working progress parameters. Based on the current temperature distribution consistency and working progress parameters, the blowing air pressure of the blow molding machine is adjusted in real time. This invention can effectively control the blow molding air pressure and improve the quality of the finished product.

Description

Technical Field

[0001] This invention relates to the field of blow molding air pressure control, and specifically to a blow molding machine blow molding control method and control device for reducing defect rates. Background Technology

[0002] The working principle of a blow molding machine is to place a heated plastic preform into a mold and blow it into a bottle shape using compressed air. The blow molding process of a two-step blow molding machine includes stretching, pre-blowing, high-pressure blowing, and degassing. Problems in any of these steps can lead to the bottle's appearance, size, thickness, etc., not meeting standards, resulting in defective products.

[0003] In related technologies, blow molding machines are typically used to blow preforms according to a pre-set fixed air pressure value. However, since the preforms are heated before blowing, the material of the preforms will have a certain degree of fluidity during blowing. Existing methods, without considering the blowing progress and the state of the preforms, cannot effectively control the air pressure by setting a fixed air pressure value. This leads to problems such as uneven wall thickness of the preforms due to improper air pressure control, which affects product quality. Summary of the Invention

[0004] To address the technical problem that, without considering the blow molding progress and preform condition, a fixed air pressure value cannot be effectively controlled, leading to uneven wall thickness in the preform due to improper air pressure control, thus affecting product quality, the present invention aims to provide a blow molding machine control method and device for reducing defect rates. The specific technical solution adopted is as follows:

[0005] This invention proposes a blow molding machine control method to reduce defect rates, the method comprising:

[0006] The temperature data of different contact points on the inner wall of the bottle mold during the blow molding process can be obtained in real time, as well as the air pressure in the blow molding machine, the air pressure inside the preform, and the extension length and speed of the blow molding machine's tension rod.

[0007] The temperature distribution consistency at the current moment is obtained based on the differences in temperature data changes between each contact point at previous times.

[0008] Based on the differences in air pressure in the gas path and the internal air pressure of the preform at each time point before the current time, the difference in the internal air pressure of the preform between the current time and the previous time point, and the difference in air pressure in the gas path and the internal air pressure of the preform at the current time, a first blowing progress index for the current time is obtained; based on the correlation between the changes in the internal air pressure of the preform at each time point before the current time and the insertion speed of the tension rod, and the insertion length and insertion speed of the tension rod at the current time, a second blowing progress index for the current time is obtained; combining the first blowing progress index and the second blowing progress index, the work progress parameters for the current time are obtained;

[0009] Based on the temperature distribution consistency and the work progress parameters at the current moment, the blowing pressure of the blow molding machine is adjusted in real time.

[0010] Furthermore, obtaining the temperature distribution uniformity at the current moment includes:

[0011] The temperature data of each contact point at all times before the current time are fitted with a straight line, and the slope of the fitted line is taken as the rate of temperature change of each contact point at the current time.

[0012] The numerator is the rate of temperature change of each contact point at the current moment, and the denominator is the average rate of temperature change of all contact points at the current moment. The ratio is used as the temperature change deviation value of each contact point at the current moment.

[0013] The sequence of temperature data for each contact point at all times prior to the current time is taken as the temperature change sequence of each contact point at the current time.

[0014] Any two contact points are treated as a group of contact points. The temperature change sequence of the two contact points in each group at the current moment is input into the dynamic time warping algorithm, and the minimum cumulative distance is output as the temperature change difference of each group of contact points.

[0015] The temperature distribution consistency at the current moment is obtained based on the distribution of the temperature change deviation values ​​of all contact points at the current moment, and the distribution of the temperature change difference of all contact point groups.

[0016] Further, obtaining the temperature distribution consistency at the current moment based on the distribution of temperature change deviation values ​​of all contact points at the current moment and the distribution of temperature change differences of all contact point groups includes:

[0017] The dispersion of the temperature change deviation values ​​at all contact points at the current moment is analyzed to obtain the first temperature disorder at the current moment;

[0018] The dispersion of the temperature change difference among all contact point groups is analyzed to obtain the second temperature disorder at the current moment;

[0019] The temperature distribution consistency at the current moment is obtained by combining the first temperature disorder and the second temperature disorder and performing negative correlation normalization.

[0020] Furthermore, the first blow molding progress indicator for obtaining the current moment includes:

[0021] The sequence of air pressures in the gas path at all times before the current time is taken as the air pressure sequence of the blow molding machine at the current time, and the sequence of air pressures inside the preform at all times before the current time is taken as the air pressure sequence inside the preform at the current time.

[0022] The gas pressure sequence of the gas path and the gas pressure sequence inside the preform are input into the dynamic time warping algorithm, and the minimum cumulative distance of the output is negatively correlated to obtain the similarity of the gas pressure change at the current moment.

[0023] The difference between the gas pressure in the gas path and the gas pressure inside the preform at the current moment is used as the gas injection evaluation value at the current moment.

[0024] The absolute value of the difference between the current time and the adjacent previous time is used as the numerator, and the absolute value of the difference between the current time and the adjacent previous time is used as the denominator. The ratio is used as the rate of change of the gas pressure inside the preform at the current time.

[0025] By combining the similarity of the gas pressure change, the gas injection evaluation value, and the rate of gas pressure change, the first blow molding progress index at the current moment is obtained.

[0026] Furthermore, the step of combining the gas pressure change similarity, the gas injection evaluation value, and the gas pressure change rate to obtain the first blow molding progress index at the current moment includes:

[0027] The first blow molding progress index at the current moment is obtained by combining the similarity of the gas pressure change, the gas injection evaluation value, and the gas pressure change rate and then normalizing them.

[0028] Furthermore, the second blow molding progress indicator for obtaining the current moment includes:

[0029] Based on the calculation method of the gas pressure change rate inside the preform at the current moment, calculate the gas pressure change rate inside the preform at each moment before the current moment.

[0030] The sequence of the rate of change of the gas pressure inside the preform at all times before the current time is taken as the sequence of the rate of change of the gas pressure inside the preform at the current time, and the sequence of the insertion speed of the tension rod at all times before the current time is taken as the sequence of the insertion speed of the tension rod at the current time.

[0031] By performing a negative correlation mapping on the Pearson correlation coefficient between the gas pressure change rate sequence and the penetration velocity sequence, the first degree of bottle blowing completion at the current moment can be obtained;

[0032] By performing a negative correlation mapping on the insertion speed of the tension rod at the current moment, the second degree of bottle blowing completion at the current moment can be obtained;

[0033] The first blow molding completion degree, the second blow molding completion degree, and the extension length of the tension rod at the current moment are combined and normalized to obtain the second blow molding progress index at the current moment.

[0034] Furthermore, obtaining the work progress parameters at the current moment includes:

[0035] Using preset dynamic weight values, the first and second bottle blowing progress indicators at the current moment are weighted and summed to obtain the work progress parameters at the current moment.

[0036] Furthermore, the real-time adjustment of the blowing air pressure of the blow molding machine includes:

[0037] The pressure control coefficient at the current moment is obtained by combining the temperature distribution consistency and the work progress parameters and then normalizing them.

[0038] Based on the pressure control coefficient at the current moment, the reference pressure of the blow molding machine at the next moment is adjusted to obtain the actual blowing pressure of the blow molding machine at the next moment.

[0039] Furthermore, obtaining the actual blowing pressure of the blow molding machine at the next moment includes:

[0040] The sum of the current pressure control coefficient and the preset control factor is used as the current pressure adjustment weight value.

[0041] The product of the pressure adjustment weight value and the reference pressure of the blow molding machine at the next moment is used as the actual blowing pressure of the blow molding machine at the next moment.

[0042] The present invention also proposes a blow molding machine control device for reducing defect rate. The control device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements any of the steps of a blow molding machine control method for reducing defect rate.

[0043] The present invention has the following beneficial effects:

[0044] This invention analyzes the temperature changes at multiple contact points on the inner wall of the bottle mold during the blowing process of a blow molding machine for preforms. The obtained temperature distribution consistency reflects the temperature distribution of the preform at each contact point in real time, allowing for effective adjustment of the blowing pressure based on this consistency to ensure blow molding quality. Furthermore, by analyzing the air pressure in the blow molding machine's air path and the internal air pressure of the preform, combined with the insertion length and speed of the blow molding machine's tension rod, the blowing progress is analyzed. The obtained progress parameters reflect the completion level of the blowing process in real time. Therefore, based on the blowing pressure requirements at different stages, the blowing pressure of the blow molding machine can be effectively controlled in real time, reducing the defect rate and improving product quality. Attached Figure Description

[0045] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of a blow molding machine blow molding control method for reducing defect rates, provided as an embodiment of the present invention. Detailed Implementation

[0047] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a blow molding machine control method and control device for reducing defect rates according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] The following description, in conjunction with the accompanying drawings, details a specific scheme for a blow molding machine control method and control device for reducing defect rates provided by the present invention.

[0050] Please see Figure 1 The diagram illustrates a flowchart of a blow molding machine blow molding control method for reducing defect rates according to an embodiment of the present invention. The method includes:

[0051] Step S1: Real-time acquisition of temperature data at different contact points on the inner wall of the bottle mold during the blow molding process, and real-time acquisition of air pressure in the blow molding machine, air pressure inside the preform, and extension length and speed of the blow molding machine's tension rod.

[0052] Blow molding machines rely on blow molding technology to transform plastic raw materials into hollow containers to meet various packaging needs. Currently, two-step blow molding machines dominate the market, which involves first making preforms and then blowing them. This process typically uses environmentally friendly PET plastic as raw material. Blow molding machines are mainly divided into extrusion blow molding machines, injection blow molding machines, and special structure blow molding machines. Blow molding machines blow air through air channels to the preforms, thereby forming the final product.

[0053] During the operation of a blow molding machine, air pressure is the most fundamental working parameter. The magnitude and variation of air pressure affect the final effect of the preform. Specifically, when the air pressure is too low, the preform cannot expand fully and evenly at the initial stage, resulting in a blurred bottle outline and poor bottom forming (unclear bottom corners, uneven thickness). This makes material distribution difficult during high-pressure blow molding, easily causing thin spots, stress whitening, or bottle bottom eccentricity. On the other hand, when the air pressure is too high, it may cause excessive and rapid stretching and thinning of the preform in certain areas (especially areas with higher temperatures), or even blow-drying. It may also force the preform to be molded before it is fully stretched, resulting in stress concentration at the bottle shoulder and bottom or uneven wall thickness. Therefore, in order to avoid the problem of excessively high blow molding defect rate due to air pressure issues, this embodiment of the invention first uses an air pressure sensor to collect the air pressure in the blow molding machine's air path and the air pressure inside the preform in real time, and at the same time uses a pull rope displacement sensor to collect the extension length and extension speed of the blow molding machine's pull rod in real time.

[0054] In this embodiment of the invention, multiple contact points are evenly arranged on the inner wall of the bottle mold, and a temperature sensor is set at each contact point. When the blow molding machine blows air onto the preform, the preform expands and touches the inner wall of the mold, thereby touching the temperature sensor at each contact point. Then, the temperature sensor is used to collect the temperature data of each contact point in real time.

[0055] In one embodiment of the present invention, the data sampling frequency of each sensor is set to 100Hz. It should also be noted that different types of data have different dimensions. Therefore, the embodiments of the present invention also need to standardize the collected different types of data to eliminate the influence of dimensions. Data standardization is a technical means well known to those skilled in the art and will not be described in detail here.

[0056] Step S2: Based on the differences in temperature data changes between each contact point at previous times, obtain the temperature distribution consistency at the current moment.

[0057] Before pre-blowing, the preform is heated so that it can be initially stretched and inflated during pre-blowing to form a basic bottle shape, laying a good foundation for the final high-pressure shaping. During the pre-blowing process, the blow molding die, consisting of two halves, closes quickly, firmly clamping the neck of the preform in the neck insert of the die to ensure a seal. The main body of the preform hangs in the die cavity. The tension rod at the top of the die begins to move downward. The tip of the tension rod is precisely inserted into the mouth of the heated and softened preform and continues to move downward. When the tension rod descends to the predetermined position (near the bottom of the preform, but usually does not touch the bottom), low-pressure compressed air is injected into the preform through the inside of the tension rod or a separate pre-blowing needle channel. During this process, the heated and softened, candy-like preform is gently inflated in all directions, so that it initially contacts the inner wall of the die.

[0058] During the blow molding process after the preform contacts the mold, the temperature changes at different locations of the bottle exhibit distinct dynamic characteristics due to significant differences in geometry, material distribution, cooling conditions, and stress state. These differences directly affect the material crystallinity, shrinkage behavior, and final quality. Therefore, this embodiment of the invention first analyzes the differences in temperature data changes between contact points at various times prior to the current moment. The obtained temperature distribution consistency reflects the consistency of the overall temperature distribution of the preform at the current moment during the pre-blowing stage. The greater the temperature distribution consistency, the more the temperature level and distribution at each contact point of the preform meet the blow molding requirements at the current moment after contacting the mold. Conversely, the smaller the temperature distribution consistency, the more uneven the preform heating is, requiring dynamic adjustment of the air pressure injection strategy to reduce the blown air pressure and avoid deformation of the preform due to excessive air pressure. Subsequently, the blowing air pressure of the blow molding machine can be effectively controlled based on the temperature distribution consistency to improve the quality of the finished product. It should also be noted that this embodiment of the invention requires a sufficiently long time period prior to the current moment to allow for analysis of earlier moments in the time sequence.

[0059] Preferably, in one embodiment of the present invention, the method for obtaining the temperature distribution uniformity at the current moment specifically includes:

[0060] The temperature data of each contact point up to the current moment is fitted with a straight line, and the slope of the fitted line is used as the temperature change rate of each contact point at the current moment. The temperature change rate reflects the temperature data change characteristics of each contact point up to the current moment. In one embodiment of the present invention, the existing least squares method or other methods can be used to achieve the straight line fitting, which is not limited or described in detail here.

[0061] The numerator is the rate of temperature change at each contact point at the current moment, and the denominator is the average rate of temperature change at all contact points at the current moment. The ratio is used as the temperature change deviation value of each contact point at the current moment. The temperature change deviation value reflects the temperature change characteristics of each contact point relative to the overall temperature change characteristics of all contact points up to the current moment.

[0062] The sequence of temperature data for each contact point up to the current moment is used as the temperature change sequence for each contact point at the current moment. Any two contact points are grouped together, and the temperature change sequences of the two contact points in each group at the current moment are input into the dynamic time warping algorithm. The minimum cumulative distance is output as the temperature change difference of each contact point group. The greater the temperature change difference, the greater the difference in temperature change between any two contact points up to the current moment.

[0063] Furthermore, the temperature distribution consistency at the current moment can be obtained based on the distribution of temperature change deviation values ​​of all contact points at the current moment, as well as the distribution of temperature change differences of all contact point groups.

[0064] Preferably, in one embodiment of the present invention, the method for obtaining the temperature distribution uniformity at the current moment further includes:

[0065] The dispersion of temperature change deviation values ​​at all contact points at the current moment is analyzed to obtain the first temperature disorder at the current moment.

[0066] In an embodiment of the present invention, the standard deviation or variance of the temperature change deviation values ​​of all contact points at the current moment can be used as the first temperature disorder at the current moment to analyze the dispersion of the temperature change deviation values ​​of all contact points at the current moment. This is not limited here, and the same method can be used for subsequent analysis of the dispersion of the data, which will not be elaborated here.

[0067] The dispersion of temperature change differences among all contact point groups is analyzed to obtain the second temperature disorder at the current moment.

[0068] The smaller the first and second temperature disorder at the current moment, the more consistent the temperature distribution and changes at each contact point. Therefore, the first and second temperature disorder can be combined and normalized with a negative correlation to limit the calculation results to a range of values. Within the range, the consistency of temperature distribution at the current moment can be obtained.

[0069] In embodiments of the present invention, the sum or product of the first temperature disorder and the second temperature disorder can be calculated to achieve the integration of the two, which is not limited here. Furthermore, the same method can be used to integrate two or more data in subsequent steps.

[0070] In one embodiment of the present invention, the natural constant can be used. A negative exponential function with base is used to normalize the negative correlation. Furthermore, subsequent steps for normalizing the negative correlation can all use a function with the natural constant. The negative exponential function with base is processed.

[0071] As an example, in one embodiment of the present invention, the expression for the uniformity of temperature distribution at the current moment can be specifically as follows:

[0072]

[0073] in, This indicates the uniformity of temperature distribution at the current moment; This indicates the current temperature disorder level. This indicates the degree of second temperature disorder at the current moment; Represented by natural constant An exponential function with base 1 is used for normalization of negative correlations.

[0074] This concludes the analysis of temperature changes at each contact point.

[0075] Step S3: Based on the differences in air pressure in the gas path and the internal air pressure of the preform at previous times, the difference in internal air pressure of the preform between the current time and the previous time, and the difference in air pressure in the gas path and the internal air pressure of the preform at the current time, obtain the first blowing progress index for the current time; based on the correlation between the changes in internal air pressure of the preform at previous times and the insertion speed of the tension rod, and the insertion length and speed of the tension rod at the current time, obtain the second blowing progress index for the current time; combine the first blowing progress index and the second blowing progress index to obtain the work progress parameters for the current time.

[0076] During the blow molding process, the position and expansion of the preform in the mold affect the process, resulting in different working progresses. Different blowing progresses require different blowing air pressures, rather than keeping the air pressure constant. Therefore, this embodiment of the invention needs to analyze the blowing progress of the blow molding machine at the current moment.

[0077] During blow molding, the gas pressure in the blow molding machine's gas path and the gas pressure inside the preform directly reflect the current stage of the blow molding process. Specifically, the gas pressure in the blow molding machine's gas path mainly reflects the machine's gas supply status; excessively high or low pressure can lead to defects. The gas pressure inside the preform more directly reflects the preform's internal state and expansion progress, making it a core indicator for judging the blow molding stage. Combining both allows for a comprehensive quantification of the blow molding process. Therefore, based on the differences in gas path pressure and preform internal pressure at previous times, the difference in preform internal pressure between the current and previous times, and the difference in gas path pressure and preform internal pressure at the current moment, the first blow molding progress index for the current moment can be obtained. This accurately quantifies the blow molding progress as reflected in gas pressure. The larger the first blow molding progress index, the closer the preform blow molding process is to completion, indicating a higher degree of completion.

[0078] Preferably, in one embodiment of the present invention, the method for obtaining the first blow molding progress indicator at the current moment specifically includes:

[0079] The sequence of air pressure in the blowing machine at the current moment is formed by the air pressure in the air path of all moments before the current moment. The sequence of air pressure inside the preform at all moments before the current moment is formed by the air pressure inside the preform at the current moment. The air pressure sequence in the air path and the air pressure sequence inside the preform are input into the dynamic time warping algorithm, and the minimum cumulative distance of the output is negatively correlated to obtain the air pressure change similarity at the current moment. The greater the air pressure change similarity, the further back the blowing progress of the blowing machine is at this moment, and the closer the blowing progress is to the completion state.

[0080] The difference between the current gas pressure in the gas path and the gas pressure inside the preform is used as the gas injection evaluation value at the current moment. When the gas injection evaluation value is positive and larger, it indicates that the gas pressure injected into the gas path of the blow molding machine is greater than the gas pressure inside the preform, which in turn indicates that it is more likely to be in the high-pressure gas injection stage in the later stage of blow molding.

[0081] The absolute value of the difference between the current time and the previous time is used as the numerator, and the absolute value of the difference between the current time and the previous time is used as the denominator. The ratio is used as the rate of change of the gas pressure inside the preform at the current time. The greater the rate of change of the gas pressure, the faster the gas pressure inside the preform changes at the current time, which means that it is more likely to be in the high-pressure gas injection stage in the later stage of bottle blowing.

[0082] Furthermore, by combining the similarity of gas pressure changes, the gas injection evaluation value, and the rate of gas pressure change, the first blowing progress index at the current moment can be obtained.

[0083] Preferably, in one embodiment of the present invention, the method for obtaining the first blow molding progress index at the current moment further includes:

[0084] After synthesizing and normalizing the similarity of pressure changes, gas injection assessment values, and pressure change rates, the calculation results are limited to... Within the range, the first blow molding progress indicator at the current moment can be obtained.

[0085] As an example, in one embodiment of the present invention, the expression for the first blow molding progress index at the current moment can be specifically as follows:

[0086]

[0087] in, This indicates the first bottle blowing progress indicator at the current moment; This represents the minimum cumulative distance between the gas pressure sequence in the blow molding machine at the current moment and the gas pressure sequence inside the preform at the current moment; Indicates the similarity of air pressure changes at the current moment; This represents the current gas injection assessment value; This indicates the rate of change of gas pressure inside the preform at the current moment; This represents the activation function, used for normalization. This indicates the preset first adjustment parameter, used to prevent the denominator from being 0. The range of values ​​is In one embodiment of the present invention, the following is used: Set to 0.01, The specific values ​​can be set by the implementer according to the specific implementation scenario, and are not limited here.

[0088] It should be noted that negative correlation mapping can also be achieved through other basic mathematical operations in other embodiments of the present invention, which will not be elaborated here.

[0089] During the operation of a blow molding machine, factors such as the extension length and speed of the stretching rod are also involved. The extension length and speed of the stretching rod reflect the degree of stretching when the preform is stretched axially. Since the degree of stretching of the preform changes with the blow molding process, the extension length and speed of the stretching rod also reflect the phased progress characteristics of the blow molding process.

[0090] Specifically, during the pre-blowing process of the blow molding machine, the tension rod initially descends at a relatively high speed to approach the bottom of the mold during pre-blowing. As it approaches the bottom, the tension rod's speed gradually decreases to ensure uniformity across the preform. During this process, it's crucial to maintain efficient coupling between the tension rod's speed and the pressure changes within the preform; the correlation between these two factors is strong. This prevents stress concentration and deformation caused by "tensioning before blowing." As the blow molding progresses, once the tension rod is close to the bottom of the mold and most of the preform is in contact with it, high-pressure blow molding can begin to shape the preform. At this point, the controller closes the pre-blowing valve and instantly opens the main blow valve. High-pressure gas is injected through the independent main blow path, ensuring the preform fully conforms to the mold, achieving the desired shape. The details of the bottle bottom edges, label area, and other areas are finalized. During this process, the tension rod remains stationary at the bottom of the bottle to maintain axial tension and ensure uniform distribution of bottle material. After the main blowing is completed, the blowing process ends, the controller opens the exhaust valve to release the residual air pressure inside the bottle, and at the same time, the tension rod retracts upward to its original position to prepare for the next cycle. Therefore, this embodiment of the invention also needs to obtain the second blowing progress index at the current moment based on the correlation between the changes in the internal air pressure of the preform at previous moments and the extension speed of the tension rod, as well as the extension length and extension speed of the tension rod at the current moment. This allows for the quantification of the blowing progress reflected by the working state of the blowing machine. Similarly, the larger the second blowing progress index, the closer the blowing progress is to the completion state.

[0091] Preferably, in one embodiment of the present invention, the method for obtaining the second bottle blowing progress index at the current moment specifically includes:

[0092] Based on the calculation method of the pressure change rate inside the preform at the current moment, the pressure change rate inside the preform at each moment before the current moment is calculated. That is, for each moment before the current moment, the absolute value of the difference between the pressure inside the preform at each moment and the adjacent previous moment is used as the numerator, the absolute value of the difference between each moment and the adjacent previous moment is used as the denominator, and the ratio is used as the pressure change rate inside the preform at each moment.

[0093] In the early stages of blow molding, the bottom of the preform is gradually brought closer to the bottom of the mold using a stretching rod. During this process, gas is blown in to ensure the preform is in an expanded and stretched state, preventing the stretching and blowing expansion actions from being out of sync. Therefore, when the stretching rod extends and the blowing process occurs simultaneously, it indicates that the preform is in the early stages of blow molding. Thus, the sequence of gas pressure change rates inside the preform at all times before the current moment can be used as the gas pressure change rate sequence inside the preform at the current moment, and the sequence of the extension speed of the stretching rod at all times before the current moment can be used as the extension speed sequence of the stretching rod at the current moment. The stronger the correlation between the gas pressure change rate sequence and the extension speed sequence, the more likely the current moment is in the early stages of blow molding. Conversely, the weaker the correlation, the more likely the current moment is in the later stages of blow molding, and the closer it is to the end of blow molding. Therefore, a negative correlation mapping can be performed on the Pearson correlation coefficient between the gas pressure change rate sequence and the extension speed sequence to obtain the first degree of end of blow molding at the current moment.

[0094] The lower the insertion speed of the stretching rod and the longer its insertion length, the closer the stretching rod is to the bottom of the mold. This indicates that the current moment is more likely to be in the later stages of blow molding and closer to the end of the blowing process. A negative correlation is applied to the insertion speed of the stretching rod at the current moment to obtain the second degree of blow molding completion. The first degree of blow molding completion, the second degree of blow molding completion, and the insertion length of the stretching rod at the current moment are then combined and normalized to limit the calculation results to a range of values. Within the range, the second blow molding progress index at the current moment can be obtained.

[0095] As an example, in one embodiment of the present invention, the expression for the second bottle blowing progress index at the current moment can be specifically as follows:

[0096]

[0097] in, This indicates the second bottle blowing progress indicator at the current moment; The Pearson correlation coefficient represents the sequence of gas pressure change rates inside the preform at the current moment and the sequence of insertion velocity of the tension rod at the current moment. This indicates the degree of completion of the first bottle blowing operation at the current moment; This indicates the insertion speed of the tension rod at the current moment; This indicates the degree of completion of the second bottle blowing operation at the current moment; This indicates the extension length of the tension rod at the current moment; This represents the hyperbolic tangent function, used for normalization. Represented by natural constant An exponential function with a base of 0 is used for negative correlation mapping; This indicates a preset second adjustment parameter, used to prevent the denominator from being 0. The range of values ​​is In one embodiment of the present invention, the following is used: Set to 0.01, The specific values ​​can be set by the implementer according to the specific implementation scenario, and are not limited here.

[0098] The first and second blow molding progress indicators at the current moment reflect the current blow molding stage from different perspectives. This stage state is related to, but not entirely the same as, the pre-blowing and high-pressure blow molding in the two-step process. It further evaluates the blow molding process based on the air pressure and non-air pressure states at different times. However, because the pre-blowing and high-pressure blow molding stages of the blow molding machine are multi-physics coupled processes, a single parameter (such as relying solely on air pressure) may not accurately reflect the progress of the current stage. For example, in the early stage of pre-blowing, the descent of the tension rod and the injection of air pressure need to be synchronized. If only air pressure is monitored, it may overlook... Mechanical actions lag behind. During the high-pressure blow molding stage, the sudden increase in air pressure and valve switching need to be coordinated. Relying solely on mechanical parameters may not be able to capture sudden changes in air pressure. Therefore, multi-source parameter fusion is used, that is, a more complete stage characteristic description is constructed by combining air pressure and mechanical parameters. Thus, the work progress parameter at the current moment can be obtained by combining the first blow molding progress index and the second blow molding progress index. The larger the work progress parameter, the closer the blow molding progress is to the completion state at the current moment. Subsequently, the blowing air pressure of the blow molding machine can be controlled in real time by combining the temperature distribution consistency and work progress parameters at the current moment, thereby improving the blow molding effect and product quality.

[0099] Preferably, in one embodiment of the present invention, the method for obtaining the work progress parameter at the current moment specifically includes:

[0100] By using preset dynamic weight values, the first and second bottle blowing progress indicators at the current moment are weighted and summed to obtain the work progress parameters at the current moment.

[0101] As an example, in one embodiment of the present invention, the expression for the current work progress parameter can be specifically as follows:

[0102]

[0103] in, This indicates the current work progress parameters; This indicates the first bottle blowing progress indicator at the current moment; This indicates the second bottle blowing progress indicator at the current moment; This indicates a preset dynamic weight value, where, when This indicates that the current moment is in the early pre-blowing stage of bottle blowing, with a greater emphasis on mechanical coordination. Therefore, the second bottle blowing progress indicator should have a higher weight at this moment. At this time, it can be set... The range of values ​​is In one embodiment of the present invention, it can be Set to 0.3, no limit is specified here; when This indicates that the current moment is in the mid-to-late stage of pre-blowing, requiring a balance of air pressure and machinery. Therefore, the weights of the first and second blowing progress indicators should be equal. At this point, [the following can be added] Set to 0.5; when When the time indicates that the current moment is in the main blowing phase, which focuses more on air pressure drive, the first blowing progress indicator at this moment should have greater weight. At this time, it can be set to... The range of values ​​is In one embodiment of the present invention, it can be Set it to 0.7; no specific limit is imposed here.

[0104] By combining the first and second blowing progress indicators at the current moment, the accuracy of describing the working stage of the blowing machine is improved. This facilitates real-time control of the blowing pressure during the blowing process, avoiding problems such as deformation of the preform and uneven wall thickness caused by excessive or insufficient air pressure.

[0105] Step S4: Based on the temperature distribution consistency and work progress parameters at the current moment, adjust the blowing pressure of the blow molding machine in real time.

[0106] When adjusting the air pressure during the blowing process based on temperature and the working stage of the blowing machine, it is necessary to consider the synergistic relationship between the temperature of the preform and the current blowing progress of the blowing machine, so as to provide the appropriate air pressure at the appropriate temperature, thereby improving the blowing effect on the preform and reducing its defect rate. Therefore, the blowing air pressure of the blowing machine can be adjusted in real time based on the temperature distribution consistency and working progress parameters at the current moment.

[0107] Preferably, in one embodiment of the present invention, the method for real-time adjustment of the blowing air pressure of the blow molding machine specifically includes:

[0108] The pressure control coefficient for the current moment is obtained by combining and normalizing the temperature distribution consistency and work progress parameters.

[0109] As an example, in one embodiment of the present invention, the expression for the pressure control coefficient at the current moment can be specifically as follows:

[0110]

[0111] in, This represents the pressure control coefficient at the current moment; This indicates the uniformity of temperature distribution at the current moment; This indicates the current work progress parameters; This represents the hyperbolic tangent function, used for normalization.

[0112] Then, based on the air pressure control coefficient at the current moment, the reference air pressure of the blow molding machine at the next moment is adjusted to obtain the actual blowing air pressure of the blow molding machine at the next moment.

[0113] Preferably, in one embodiment of the present invention, the method for obtaining the actual blowing pressure of the blow molding machine at the next moment specifically includes:

[0114] The sum of the current air pressure control coefficient and the preset control factor is used as the current air pressure adjustment weight value. The product of the air pressure adjustment weight value and the reference air pressure of the blow molding machine at the next moment is used as the actual blowing air pressure of the blow molding machine at the next moment.

[0115] As an example, in one embodiment of the present invention, the expression for the actual blowing pressure of the blow molding machine at the next moment can be specifically as follows:

[0116]

[0117] in, This indicates the actual blowing pressure of the blow molding machine at the next moment; This represents the pressure control coefficient at the current moment; This represents a preset control factor, used to adjust the degree of control of the air pressure control coefficient according to demand. In one embodiment of the present invention, [the following is an example of this concept]. Set to 0.5; This indicates the reference air pressure of the blow molding machine at the next moment. This value is a known value. For example, the reference air pressure in the pre-blowing stage is usually 6~12 bar, and the reference air pressure in the high-pressure blow molding stage is usually 35~40 bar. Here, bar is a unit of pressure.

[0118] One embodiment of the present invention provides a blow molding machine control device for reducing defect rate. The control device includes a memory, a processor and a computer program, wherein the memory is used to store the corresponding computer program, the processor is used to run the corresponding computer program, and the computer program can implement the methods described in steps S1 to S4 when running in the processor.

[0119] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0120] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A blow molding machine blow molding control method for reducing defect rate, characterized in that, The method includes: The temperature data of different contact points on the inner wall of the bottle mold during the blow molding process can be obtained in real time, as well as the air pressure in the blow molding machine, the air pressure inside the preform, and the extension length and speed of the blow molding machine's tension rod. The temperature distribution consistency at the current moment is obtained based on the differences in temperature data changes between each contact point at previous times. Based on the differences in air pressure in the gas path and the internal air pressure of the preform at each time point before the current time, the difference in the internal air pressure of the preform between the current time and the previous time point, and the difference in air pressure in the gas path and the internal air pressure of the preform at the current time, a first blowing progress index for the current time is obtained; based on the correlation between the changes in the internal air pressure of the preform at each time point before the current time and the insertion speed of the tension rod, and the insertion length and insertion speed of the tension rod at the current time, a second blowing progress index for the current time is obtained; combining the first blowing progress index and the second blowing progress index, the work progress parameters for the current time are obtained; Based on the temperature distribution consistency and the work progress parameters at the current moment, the blowing air pressure of the blow molding machine is adjusted in real time. The process of obtaining the temperature distribution uniformity at the current moment includes: The temperature data of each contact point at all times before the current time are fitted with a straight line, and the slope of the fitted line is taken as the rate of temperature change of each contact point at the current time. The numerator is the rate of temperature change of each contact point at the current moment, and the denominator is the average rate of temperature change of all contact points at the current moment. The ratio is used as the temperature change deviation value of each contact point at the current moment. The sequence of temperature data for each contact point at all times prior to the current time is taken as the temperature change sequence of each contact point at the current time. Any two contact points are treated as a group of contact points. The temperature change sequence of the two contact points in each group at the current moment is input into the dynamic time warping algorithm, and the minimum cumulative distance is output as the temperature change difference of each group of contact points. The temperature distribution consistency at the current moment is obtained based on the distribution of the temperature change deviation values ​​of all contact points at the current moment, and the distribution of the temperature change difference of all contact point groups.

2. The blow molding control method for reducing defect rate in a blow molding machine according to claim 1, characterized in that, The step of obtaining the temperature distribution consistency at the current moment based on the distribution of temperature change deviation values ​​of all contact points at the current moment, and the distribution of temperature change difference of all contact point groups, includes: The dispersion of the temperature change deviation values ​​at all contact points at the current moment is analyzed to obtain the first temperature disorder at the current moment; The dispersion of the temperature change difference among all contact point groups is analyzed to obtain the second temperature disorder at the current moment; The temperature distribution consistency at the current moment is obtained by combining the first temperature disorder and the second temperature disorder and performing negative correlation normalization.

3. The blow molding control method for reducing defect rate in a blow molding machine according to claim 1, characterized in that, The first blow molding progress indicator for obtaining the current moment includes: The sequence of air pressures in the gas path at all times before the current time is taken as the air pressure sequence of the blow molding machine at the current time, and the sequence of air pressures inside the preform at all times before the current time is taken as the air pressure sequence inside the preform at the current time. The gas pressure sequence of the gas path and the gas pressure sequence inside the preform are input into the dynamic time warping algorithm, and the minimum cumulative distance of the output is negatively correlated to obtain the similarity of the gas pressure change at the current moment. The difference between the gas pressure in the gas path and the gas pressure inside the preform at the current moment is used as the gas injection evaluation value at the current moment. The absolute value of the difference between the current time and the adjacent previous time is used as the numerator, and the absolute value of the difference between the current time and the adjacent previous time is used as the denominator. The ratio is used as the rate of change of the gas pressure inside the preform at the current time. By combining the similarity of the gas pressure change, the gas injection evaluation value, and the rate of gas pressure change, the first blow molding progress index at the current moment is obtained.

4. The blow molding control method for reducing defect rate in a blow molding machine according to claim 3, characterized in that, The process of combining the similarity of the gas pressure changes, the gas injection evaluation value, and the rate of gas pressure change to obtain the first blowing progress index at the current moment includes: The first blow molding progress index at the current moment is obtained by combining the similarity of the gas pressure change, the gas injection evaluation value, and the gas pressure change rate and then normalizing them.

5. The blow molding control method for reducing defect rate in a blow molding machine according to claim 3, characterized in that, The second blow molding progress indicator for obtaining the current moment includes: Based on the calculation method of the gas pressure change rate inside the preform at the current moment, calculate the gas pressure change rate inside the preform at each moment before the current moment. The sequence of the rate of change of the gas pressure inside the preform at all times before the current time is taken as the sequence of the rate of change of the gas pressure inside the preform at the current time, and the sequence of the insertion speed of the tension rod at all times before the current time is taken as the sequence of the insertion speed of the tension rod at the current time. By performing a negative correlation mapping on the Pearson correlation coefficient between the gas pressure change rate sequence and the penetration velocity sequence, the first degree of bottle blowing completion at the current moment can be obtained; By performing a negative correlation mapping on the insertion speed of the tension rod at the current moment, the second degree of bottle blowing completion at the current moment can be obtained; The first blow molding completion degree, the second blow molding completion degree, and the extension length of the tension rod at the current moment are combined and normalized to obtain the second blow molding progress index at the current moment.

6. The blow molding control method for reducing defect rate in a blow molding machine according to claim 1, characterized in that, The parameters for obtaining the current work progress include: Using preset dynamic weight values, the first and second bottle blowing progress indicators at the current moment are weighted and summed to obtain the work progress parameters at the current moment.

7. The blow molding control method for reducing defect rate in a blow molding machine according to claim 1, characterized in that, The real-time adjustment of the blowing air pressure of the blow molding machine includes: The pressure control coefficient at the current moment is obtained by combining the temperature distribution consistency and the work progress parameters and then normalizing them. Based on the pressure control coefficient at the current moment, the reference pressure of the blow molding machine at the next moment is adjusted to obtain the actual blowing pressure of the blow molding machine at the next moment.

8. The blow molding control method for reducing defect rate in a blow molding machine according to claim 7, characterized in that, The actual blowing pressure of the blow molding machine at the next moment includes: The sum of the current pressure control coefficient and the preset control factor is used as the current pressure adjustment weight value. The product of the pressure adjustment weight value and the reference pressure of the blow molding machine at the next moment is used as the actual blowing pressure of the blow molding machine at the next moment.

9. A blow molding machine control device for reducing defect rates, the control device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 8.

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