A method and apparatus for controlling a hollow blow molding machine to improve blow molding uniformity

Abstract

This invention relates to the field of production control technology, specifically to a control method and equipment for a hollow blow molding machine to improve blow molding uniformity. The method includes: acquiring radial points in a radial region and determining the temperature value of these points during extrusion; determining the compression tendency index of the radial region based on the diameter distribution and contour complexity of the radial points; determining the degree of compression demand based on the temperature distribution corresponding to the radial region; determining the sag performance based on the radial length change of the extruded radial region; further determining the influence of preform deformation; obtaining the radial compression urgency by combining the compression demand and the preform deformation influence; and adjusting the radial compression force of the flexible ring of the blow molding machine in real time based on the radial compression urgency. This invention can improve the uniformity of preform wall thickness and enhance the control accuracy of blow molding uniformity by combining mold contour complexity analysis, thermoplastic temperature analysis, and sag influence analysis.

Description

Technical Field

[0001] This invention relates to the field of production control technology, specifically to a control method and equipment for a hollow blow molding machine that improves blow molding uniformity. Background Technology

[0002] Blow molding machines extrude semi-molten plastic preforms and inject compressed air into them to expand and conform them to the inner wall of the mold. After cooling, a hollow product is formed. Due to the complex mold profile and the fact that the initial extruded preform is a uniform cylindrical shape, direct blow molding can lead to significant differences in the degree of conformity between different areas of the preform and the mold. To improve blow molding uniformity, traditional methods use a PID module to control a flexible ring radial adjustment device at the extrusion die. This device adjusts the radial compression of the preform to different degrees using a preset radial control curve, ensuring a more uniform conformity between the preform and the inner wall of the mold during blow molding.

[0003] Traditional control methods based on preset radial control curves have the following drawbacks: the contours of different parts of the blow molding die vary greatly, and the thermal deformation tendency of the preform during extrusion changes dynamically with the extrusion precision, resulting in different optimal radial compression parameters required at different times; relying solely on preset fixed curves is difficult to adapt to actual dynamic needs, and the preform after extrusion may sag due to gravity before blow molding, while traditional methods do not consider the interference of this deformation on radial compression adjustment, further increasing analysis errors, resulting in poor blow molding uniformity and reducing the control precision of blow molding uniformity. Summary of the Invention

[0004] To address the technical problems of poor blow molding uniformity and insufficient control precision in related technologies, this invention provides a control method and equipment for improving blow molding uniformity in a hollow blow molding machine. The specific technical solution adopted is as follows:

[0005] This invention proposes a control method for hollow blow molding machines to improve blow molding uniformity, the method comprising:

[0006] Obtain the point cloud model of the mold for the product to be blow molded, divide the point cloud model into different radial layers evenly, determine the radial region that matches the real-time extruded preform with each radial layer, sample multiple radial points on average in each radial region, and determine the temperature value of the radial point during extrusion.

[0007] Based on the diameter distribution of the radial points corresponding to each radial region and the complexity of its own contour, the compression tendency index of the radial region is determined; combined with the temperature distribution and compression tendency index of different radial regions, the compression requirement of each radial region is determined.

[0008] During the extrusion process, the sagging performance of the radial region is determined based on the change in radial length of the extruded radial region at different sampling times; the deformation influence of the extruded radial region is determined based on the sagging performance of each extruded radial region.

[0009] The radial compression urgency is obtained by combining the compression requirement of each extruded radial region with the influence of preform deformation; the radial compression force of the flexible ring of the blow molding machine is adjusted in real time based on the radial compression urgency.

[0010] Furthermore, determining the compression tendency index of the radial region based on the diameter distribution corresponding to each radial region and the complexity of its own contour includes:

[0011] Determine the profile diameter of each radial point; based on the numerical distribution of the profile diameters of all radial points in all radial regions, determine the applicability of the preform in each radial region;

[0012] The negative number of the application degree of the preform is normalized and used as an indicator of application impact.

[0013] Calculate the numerical standard deviation of the profile diameter of all radial points in the same radial region, normalize the negative of the standard deviation, and use it as the profile stability coefficient.

[0014] The product of the profile stability coefficient of the radial region and the applied influence index is calculated as an index of the compression tendency of the radial region.

[0015] Further, determining the preform application degree of each radial region based on the numerical distribution of the profile diameters of all radial points in all radial regions includes:

[0016] Calculate the average of the profile diameters of all radial points in the same radial region, and use this as the region diameter of the radial region;

[0017] The average diameter of all radial regions is used as the analysis diameter;

[0018] Calculate the difference between the region diameter and the analysis diameter for each radial region, and normalize the difference as the applicability of the preform.

[0019] Furthermore, a temperature sensing module is configured at the die position of the blow molding machine to acquire the temperature value of each radial point in each radial region during extrusion. The degree of compression requirement for each radial region is determined by combining the temperature distribution and compression trend indicators of different radial regions during extrusion, including:

[0020] The average temperature of all radial points in the same radial region is taken as the region temperature.

[0021] The regional temperature is normalized by its maximum and minimum values ​​and used as a temperature influence index.

[0022] The product of the temperature influence index and the compression tendency index for each radial region is normalized and used as the compression demand level for that radial region.

[0023] Furthermore, based on the change in radial length of the extruded radial region at different sampling times, the sagging performance of the radial region is determined, including:

[0024] Within the time range of extrusion, different sampling times are evenly divided. For each extruded radial region, the radial length of the corresponding radial region that has been extruded at each sampling time is obtained.

[0025] The radial length difference between adjacent sampling times is used as the droop factor for the sampling period between adjacent sampling times;

[0026] The droop trend index is determined based on the change in the droop factor during the sampling period between adjacent sampling times.

[0027] The mean of the droop factor for all sampling periods in the extruded radial region is normalized and used as the droop analysis index.

[0028] Calculate the product of the sagging trend index and the sagging analysis index of the extruded radial region as the sagging performance of the radial region.

[0029] Furthermore, based on the numerical change of the droop factor during the sampling period between adjacent sampling times, droop trend indicators are determined, including:

[0030] A two-dimensional rectangular coordinate system is constructed with the sampling period as the x-axis and the droop factor as the y-axis. The coordinate points of the droop factor for each sampling period in the coordinate system are determined. Least squares line fitting is performed on all coordinate points to obtain the fitted line.

[0031] The normalized slope of the fitted line is determined as an indicator of the downward trend.

[0032] Furthermore, based on the sagging performance of each extruded radial region, the preform deformation influence of the extruded radial region is determined, including:

[0033] Calculate the average sagging performance of the same radial region from the initial sampling time to the current sampling time, and normalize it to obtain the deformation influence of the extruded radial region.

[0034] Furthermore, by combining the compression requirement of each extruded radial region with the influence of preform deformation, the radial compression urgency is obtained, including:

[0035] The negative number of the influence of embryo deformation was normalized and used as the first urgent indicator;

[0036] Different preset urgency weights are assigned to the degree of compression demand and the primary urgency index, and the weighted sums and normalization are performed to obtain the radial compression urgency.

[0037] Furthermore, the radial compression force of the flexible ring in the blow molding machine is adjusted in real time based on the urgency of radial compression, including:

[0038] The average radial compression urgency of all extruded radial regions at the current sampling time is used as the control index;

[0039] Determine the preset proportional gain coefficient adjustment range, and linearly map the real-time control index to the adjustment range to obtain the proportional control index;

[0040] The sum of the real-time proportional gain coefficient and the proportional adjustment index is used as the adjusted proportional gain value.

[0041] The proportional gain value is adjusted and used as the real-time proportional term for PID control.

[0042] On the other hand, a control device for a hollow blow molding machine that improves blow molding uniformity is also provided. The device includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the method as described in any of the foregoing claims.

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

[0044] In this embodiment of the invention, the contour performance of the blow-molded product mold is first analyzed. Based on the diameter of radial points in different vertical directions and the complexity of its own contour, a compression tendency index is determined. Combining the temperature distribution and the compression tendency index, the degree of compression requirement is determined, characterizing the required compression degree in the radial region during extrusion. The compression degree is adjusted by a flexible ring. Furthermore, the sagging performance during the preform extrusion process is analyzed to obtain the preform deformation influence. Combining the compression requirement and the preform deformation influence, the radial compression urgency is determined, enabling real-time control of the radial compression force of the blow molding machine's flexible ring. This invention can effectively analyze the contour complexity, thermoplasticity influence, and sagging performance of different molds, thereby reflecting these dimensions of analysis in the real-time preform extrusion process. Adjusting the blow molding machine's flexible ring achieves real-time radial compression force control, thereby improving the uniformity of the preform wall thickness and enhancing the control accuracy of blow molding uniformity. 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 control method for a hollow blow molding machine to improve blow molding uniformity, 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 the intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a hollow blow molding machine control method and equipment for improving blow molding uniformity 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 hollow blow molding machine control method to improve blow molding uniformity provided by the present invention.

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

[0051] S101: Obtain the point cloud model of the mold for the product to be blow-molded, divide the point cloud model into different radial layers evenly, determine the radial region that matches the real-time extruded preform with each radial layer, sample multiple radial points on average in each radial region, and determine the temperature value of the radial point during extrusion.

[0052] The hollow blow molding machine places the extruded plastic preform into a mold, closes the mold, and blows in compressed air to make the preform adhere tightly to the inner wall of the mold. After cooling and demolding, a hollow product is obtained.

[0053] During blow molding, the mold surface provides strong cooling, and the preform solidifies rapidly upon contact with the mold. In complex molds, the contact time between different parts varies significantly, leading to uneven wall thickness in the finished product. To address this, traditional methods use a PID module to control the compression of the flexible ring at the blow molding die, dynamically adjusting the die gap to alter the preform's wall thickness distribution (e.g., greater flexible ring compression results in a smaller die gap and increased wall thickness at the corresponding location). By pre-adjusting the preform contour, the preform can fit more evenly against the mold during blow molding, improving wall thickness uniformity.

[0054] This traditional method often relies on a preset radial control curve. The preform adjustment results obtained by this method have poor wall thickness uniformity after blow molding. Therefore, in this embodiment of the invention, the PID radial parameter control process of the blow molding machine is analyzed in detail in combination with the actual scenario to improve the product blow molding uniformity.

[0055] In this embodiment of the invention, it is necessary to first obtain a three-dimensional point cloud model of the mold, which records the position coordinate information of each point of the mold. Then, the axial height of the mold is divided into twenty regions.

[0056] It should be noted that the twenty regions in this embodiment are empirical values ​​obtained under typical hardware configurations and testing scenarios, intended to facilitate understanding of the invention. In practical applications, those skilled in the art can adjust the number of regions according to actual injection molding needs, which does not constitute a limitation of the invention.

[0057] For example, a cylindrical mold with a total height of 20cm can be divided into 20 radial layers, each with a height of 1cm.

[0058] Then, the radial layers of the mold are matched with the preform. The specific matching process can be combined with the blow molding matching of the mold in the blow molding machine. That is, the control module of the blow molding machine has the three-dimensional point cloud of each mold and the corresponding radial layer distribution. Then, it is mapped onto each preform according to the radial height to determine the radial area corresponding to different radial layers on each preform.

[0059] For example, if the preform before blow molding is 3cm, the preform is identified by point cloud analysis, and then it is divided into the same number of height regions as the radial layers. The height regions are matched one by one according to the arrangement order of the radial layers to obtain the radial regions.

[0060] Alternatively, in some other embodiments of the present invention, point cloud detection can be performed directly on the preform to determine the point cloud data of the preform, and then the point cloud model of the radial layer of the mold can be matched with the point cloud data model of the preform to determine the matching radial region.

[0061] Multiple radial points are sampled on average in each radial region. The number of radial points can be adjusted according to the actual detection situation. Each radial region can specifically include 10 radial points. It should be noted that these radial points are also sampling points at different radial heights. A radial region is a preform region within a height range, while a radial point represents a feature at the corresponding height. By performing a circumferential cut at the same height from each radial point, the cross-section of the preform at the height of that radial point can be obtained.

[0062] In this embodiment of the invention, a temperature sensing module can be configured at the die position of the blow molding machine to obtain the temperature value of each radial point in each radial region during extrusion.

[0063] The purpose of acquiring various types of data mentioned above is to provide a data foundation for the subsequent analysis process.

[0064] S102: Based on the diameter distribution of the radial points corresponding to each radial region and the complexity of its own contour, determine the compression tendency index of the radial region; combine the temperature distribution and compression tendency index corresponding to different radial regions to determine the compression requirement of each radial region.

[0065] Considering the differences in edge contours of different layers of the blow molding die, the compression requirements of the radial region of the preform will vary. For example, the more the contour of the radial region is relatively concentrated compared to other radial regions, the higher the compression requirement of the flexible ring in the radial region of the preform is, and vice versa. Therefore, this step first analyzes the contour performance of the die and analyzes the compression trend characteristics of each radial region.

[0066] The higher the compressibility of the flexible ring, the more the preform shrinks inward, and the amount of material used will decrease during the shrinking process of the preform.

[0067] Furthermore, in some embodiments of the present invention, the compression tendency index of the radial region is determined based on the diameter value distribution corresponding to each radial region and the complexity of its own contour, including: determining the contour diameter of each radial point; determining the mold application degree of each radial region based on the numerical distribution of the contour diameters of all radial points in all radial regions; normalizing the negative value of the mold application degree as an application influence index; calculating the numerical standard deviation of the contour diameters of all radial points in the same radial region, and normalizing the negative value of the standard deviation as a contour stability coefficient; and calculating the product of the contour stability coefficient and the application influence index of the radial region as a compression tendency index of the radial region.

[0068] In this process, taking the verticality of the mold as a reference, the radial height corresponding to each radial point in the mold is determined based on the matching situation. A horizontal sectional plane at the same radial height in the mold is then determined as the contour surface corresponding to the radial point. Finally, the diameter of the largest inscribed circle of the contour surface is taken as the contour diameter. In other embodiments of this invention, the smallest circumscribed circle can also be used for contour diameter analysis, depending on the actual mold condition and requirements.

[0069] First, blow-molded products often exhibit complex contours, meaning that different radial layers in the mold often have varying contour requirements. For example, if some radial layers are relatively concave, the overall material consumption during preform manufacturing is relatively low. Therefore, when compressing this radial region of the preform, a higher degree of compression can be applied, resulting in a narrower preform diameter. Specifically, this invention uses preform application degree to characterize the compression characteristics of the diameter.

[0070] Furthermore, in some embodiments of the present invention, determining the preform application degree of each radial region based on the numerical distribution of the profile diameters of all radial points in all radial regions includes: calculating the numerical mean of the profile diameters of all radial points in the same radial region as the region diameter of the radial region; using the mean of the region diameters of all radial regions as the analysis diameter; calculating the difference between the region diameter and the analysis diameter of each radial region, and normalizing the difference as the preform application degree.

[0071] In this embodiment of the invention, the contour diameters of all radial points in the same radial region are integrated, and the average value is directly calculated as the region diameter of the radial region. Then, the diameter features of all radial regions are integrated, and the average value of the region diameters of all radial regions is calculated as the analysis diameter.

[0072] Understandably, the larger the diameter of each region under the overall mold characteristics, the larger that part needs to be expanded, requiring more preform material to ensure uniform wall thickness after expansion. Therefore, the difference between the region diameter and the analysis diameter of each radial region is directly calculated and normalized to obtain the preform application degree. The preform application degree characterizes the degree of material application of the preform; the larger the value, the larger the contour diameter in the corresponding radial region, requiring more preform material and a smaller flexible ring compression to ensure a larger contour diameter.

[0073] In one embodiment of the present invention, the normalization process can specifically be, for example, maximum-minimum value normalization. Furthermore, subsequent normalization steps can all employ maximum-minimum value normalization. In other embodiments of the present invention, other normalization methods can be selected based on the specific range of the numerical values, which will not be elaborated further. The normalization process also serves to convert dimensional data into dimensionless data, facilitating subsequent calculations and analysis.

[0074] In this embodiment of the invention, to facilitate subsequent calculations and analysis, the negative value of the application degree of the preform is normalized and used as an application impact index. The larger the value of the application impact index, the greater the required flexible ring compression to ensure a larger profile diameter.

[0075] The application of influencing indicators to analyze the overall contour material demand level of a single radial region reveals that there may be situations where the overall material consumption levels of two radial regions are similar, but the interlayer subdivision contours exhibit different characteristics. This is because, under the same preform material consumption, the radial regions of the preform with more complex boundary contour changes may experience some smaller diameter areas reaching the mold contour first during subsequent blow molding, while some larger diameter areas reach the mold contour later. Consequently, the cooling time of the complex preform radial regions to the mold varies significantly. In such cases, the preform of the complex radial region should be subjected to lower compression during manufacturing, making the preform wider and advancing the overall wall adhesion time, thereby reducing the tendency for short-term wall adhesion differences between radial regions.

[0076] Therefore, this embodiment of the invention analyzes complex radial regions, calculates the numerical standard deviation of the profile diameter of all radial points in the same radial region, and normalizes the negative of the standard deviation as the profile stability coefficient.

[0077] The numerical standard deviation characterizes the contour complexity. The larger the standard deviation value, the more complex the contour changes within the vertical range corresponding to the radial region. To facilitate subsequent calculations, the negative of the standard deviation is normalized and used as the contour stability coefficient.

[0078] In summary, the product of the radial region's profile stability coefficient and the applied influence index is used as the compression tendency index for the radial region. Since a larger profile stability coefficient indicates a lower complexity of profile changes within the corresponding vertical range of the radial region, a larger flexible ring compression degree can be used to ensure uniformity. Conversely, a larger applied influence index indicates a greater need for flexible ring compression degree to ensure a larger profile diameter. Therefore, the two values ​​are directly multiplied to obtain the compression tendency index. A larger compression tendency index value indicates a higher degree of compression should be applied when adjusting the profile of the extruded preform.

[0079] The above analysis of preform compression demand from the perspective of blow molding die contour assumes that the preforms in each radial region have the same thermoplasticity during extrusion. However, in actual scenarios, due to the precision of the preform extrusion process, there are deviations in temperature difference between the radial regions, resulting in differences in thermoplasticity. The real-time extruded preform with stronger performance at relatively high temperatures has a faster rate of thermal expansion during blow molding and is more likely to adhere to the wall earlier. Therefore, a higher degree of compression needs to be applied to this part of the radial region during preform manufacturing to counteract the phenomenon of premature adhesion of the radial layer to the wall, thereby reducing the error in thermoplasticity analysis.

[0080] Furthermore, in some embodiments of the present invention, the degree of compression requirement for each radial region is determined by combining the temperature value distribution and compression trend index during extrusion in different radial regions, including: taking the average temperature value of all radial points in the same radial region as the region temperature; normalizing the region temperature by maximum and minimum values ​​as the temperature influence index; and normalizing the product of the temperature influence index and the compression trend index of each radial region as the degree of compression requirement for the radial region.

[0081] The higher the regional temperature, the stronger the high-temperature performance of the radial region. This indicates a faster rate of thermal expansion during blow molding and a greater tendency to adhere to the mold walls earlier. Therefore, a higher degree of compression needs to be applied to this radial region during preform manufacturing. Thus, the regional temperature is directly normalized to its maximum and minimum values ​​as a temperature influence index. Then, the product of the radial region's temperature influence index and compression tendency index is normalized to represent the compression demand level of the radial region. This index characterizes the compression demand characteristics obtained from multi-dimensional analysis under mold shape and extrusion temperature. A higher compression demand level corresponds to a greater compression force requirement for the radial region.

[0082] Of course, in other embodiments of the present invention, different demand weight values ​​can be assigned to the temperature influence index and the compression trend index according to their different impacts on the final result. For example, the demand weight value for the temperature influence index is 0.75, and the demand weight value for the compression trend index is 0.25. Then, the demand weight values ​​are weighted and summed, and normalized to obtain the degree of compression demand.

[0083] The specific numerical values ​​of the required weights given in the embodiments of this invention (such as 0.75, 0.25, etc.), as well as the weight values ​​subsequently assigned when analyzing a certain feature using two parameters, are all empirical values ​​obtained under typical hardware configurations and test scenarios, intended to facilitate understanding of this invention. In practical applications, those skilled in the art can adjust, calibrate, or optimize these parameters according to specific hardware performance, scenario complexity, and data characteristics, which does not constitute a limitation of this invention.

[0084] S103: During the extrusion process, the sagging performance of the radial region is determined based on the change in radial length of the extruded radial region at different sampling times; the deformation influence of the extruded radial region is determined based on the sagging performance of each extruded radial region.

[0085] The extrusion process in this embodiment of the invention is a preform extrusion process. By adjusting the extruded preform, the overall effect of the vacuum blow molding process is improved.

[0086] Considering that the preform will sag due to gravity after extrusion, the deformation behavior of different radial regions of the extruded preform may vary. For example, the lower radial region that has been extruded for a longer time will experience a longer period of sagging deformation, and the lower preform density may cause the sagging deformation to intensify. On the other hand, the radial region that has just been extruded is connected to more extruded radial regions below it and is more affected by gravity, which may also lead to stronger sagging deformation. In actual scenarios, it is not possible to control the extrusion based on a preset shape. Therefore, certain adjustments are required.

[0087] Furthermore, in some embodiments of the present invention, determining the sagging performance of a radial region based on the change in radial length of the extruded radial region at different sampling times includes: uniformly dividing different sampling times within the extrusion time range; for each extruded radial region, obtaining the radial length of the corresponding radial region at each sampling time; using the difference in radial length between adjacent sampling times as the sagging factor for the sampling period between adjacent sampling times; determining a sagging trend index based on the change in the value of the sagging factor for the sampling period between adjacent sampling times; normalizing the mean of the sagging factors for all sampling periods of the extruded radial region as a sagging analysis index; and calculating the product of the sagging trend index and the sagging analysis index of the extruded radial region as the sagging performance of the radial region.

[0088] The process involves determining the droop trend index based on the numerical change of the droop factor during the sampling period between adjacent sampling times. This includes: constructing a two-dimensional rectangular coordinate system with the sampling period as the abscissa and the droop factor as the ordinate; determining the coordinate points of the droop factor for each sampling period in the coordinate system; performing least-squares line fitting on all coordinate points to obtain a fitted line; and determining the normalized slope value of the fitted line as the droop trend index.

[0089] The sag performance refers to the degree of sag in the radial region after extrusion. Since the preform is extruded uniformly, the radial region can be divided according to the sampling time during the extrusion process. Different sampling times can be evenly divided within the extrusion time range for each extruded radial region. The specific sampling time can be determined at 1 second or 0.1 seconds, depending on the size of the blow-molded product and the overall blow molding time; there are no restrictions on this.

[0090] At each sampling moment, the radial vertical length from the lowest point of the corresponding radial region to that sampling moment is taken as the extruded radial length. Each sampling moment corresponds to a radial length. The difference in radial length between adjacent sampling moments represents the length of the preform extruded at adjacent sampling moments. This preform length will be elongated to different degrees with time and the extrusion process due to the influence of gravity and thermoplasticity. The higher the value, the more obvious the elongation and the greater the sag. Therefore, the difference in radial length is directly used as the sag factor for the sampling period between adjacent sampling moments.

[0091] Since the material is still affected by sagging after extrusion, a two-dimensional rectangular coordinate system is constructed with the sampling time period as the x-axis and the sagging factor as the y-axis for each sampling time period consisting of two adjacent sampling times. Then, least squares line fitting is performed to obtain a fitted line. The larger the slope of the fitted line, the longer the radial length is at adjacent sampling times, which means that a sagging effect has occurred and the greater the degree of sagging, the more the normalized value of the slope of the fitted line is used as the sagging trend indicator.

[0092] Meanwhile, the mean of the sag factor for all sampling periods in the extruded radial region is normalized and used as a sag analysis index, which also characterizes the degree of sag. The normalization of the mean of the sag factor is to eliminate the shape differences between different molds and preforms and retain the sag characteristics. Therefore, a standard maximum sag coefficient for a preform can be preset. Then, the ratio of the mean of the sag factor to the standard maximum sag coefficient is calculated to achieve normalization and remove the influence of dimensions.

[0093] The product of the droop trend index and the droop analysis index of the extruded radial region is calculated as the droop performance of the radial region. Since a larger droop trend index and droop analysis index indicate a more pronounced droop, the product of the droop trend index and the droop analysis index is directly calculated as the droop performance of the radial region.

[0094] The sagging deformation may differ between different radial regions. For example, the radial region at the end of the extrusion has been extruded earlier and has undergone a longer period of sagging deformation, resulting in a lower density due to stretching. This radial region may experience intensified sagging deformation. On the other hand, for radial regions that have been extruded recently, there are more adjacent preform radial regions below, which may also cause intensified deformation. Therefore, in order to ensure blow molding uniformity, it is necessary to apply appropriate compressive force to the radial regions of the preform that are being extruded in real time, so that their sagging deformation matches the deformation effect of each extruded radial region, thereby improving blow molding uniformity.

[0095] Furthermore, in some embodiments of the present invention, the determination of the preform deformation influence degree of the extruded radial region based on the sag performance degree of each extruded radial region includes: calculating the average sag performance degree of the same radial region from the initial sampling time to the current sampling time, and normalizing the result to obtain the preform deformation influence degree of the extruded radial region.

[0096] Understandably, at the first sampling moment after extrusion, the droop performance can be directly set to a value of 0. Then, a droop performance can be obtained at each sampling moment. The average droop performance from the initial sampling moment to the current sampling moment is calculated as the embryo deformation influence. The larger the value, the more obvious the embryo deformation influence.

[0097] S104: Combine the compression demand of each extruded radial region with the influence of preform deformation to obtain the radial compression urgency; adjust the radial compression force of the flexible ring of the blow molding machine in real time based on the radial compression urgency.

[0098] Furthermore, in some embodiments of the present invention, the radial compression urgency is obtained by combining the compression demand degree of each extruded radial region and the influence degree of preform deformation, including: normalizing the negative number of the preform deformation influence degree as a first urgency index; assigning different preset urgency weights to the compression demand degree and the first urgency index respectively, performing weighted summation and normalization to obtain the radial compression urgency.

[0099] The larger the value of the preform deformation influence degree, the more significant the influence of preform deformation. In this case, it is more necessary to reduce the compression effect so that the preform density in the real-time radial region is lower. This ensures that the sagging deformation rate of the preform in the radial region can match that of each extruded radial region, thereby improving blow molding uniformity. Therefore, in this embodiment of the invention, the negative number of the preform deformation influence degree is normalized as the first urgent indicator.

[0100] The compression demand level characterizes the index features of compression demand obtained from multi-dimensional analysis under die shape and extrusion temperature. The higher the value of the compression demand level, the greater the compression force required in the corresponding radial region. In this embodiment of the invention, different preset urgency weights are assigned to the compression demand level and the first urgency index, thereby achieving weighted analysis to obtain the radial compression urgency.

[0101] In this embodiment of the invention, the specific values ​​of the preset urgency weights are empirical values ​​obtained under typical hardware configurations and test scenarios, intended to facilitate understanding of the invention. In practical applications, those skilled in the art can adjust, calibrate, or optimize these parameters according to specific hardware performance, scenario complexity, and data characteristics, which does not constitute a limitation of the invention.

[0102] For example, the preset urgency weight for the degree of demand compression is 0.6, and the preset urgency weight for the first urgency index is 0.4. Therefore, the product of the degree of demand compression and 0.6 is calculated, and the product of the first urgency index and 0.4 is calculated. Then, the sum of the two product values ​​is normalized by the maximum and minimum values ​​to obtain the radial urgency of demand compression.

[0103] Furthermore, in some embodiments of the present invention, the real-time radial compression force of the flexible ring of the blow molding machine is controlled based on the radial compression urgency, including: taking the average of the radial compression urgency of all extruded radial regions at the current sampling time as the control index; determining a preset proportional gain coefficient adjustment range, linearly mapping the real-time control index to the adjustment range to obtain a proportional adjustment index; taking the sum of the real-time proportional gain coefficient and the proportional adjustment index as the adjusted proportional gain value; and using the adjusted proportional gain value as a real-time proportional term for PID control.

[0104] Each extruded radial region may have a different radial compression urgency, but all of them can affect the overall blow-molded product. In order to adjust the overall uniformity, it is necessary to adjust the extruded preform at the current sampling time. First, the average radial compression urgency of all extruded radial regions at the current sampling time is used as the control index to represent the overall compression urgency characteristics.

[0105] The preset proportional gain coefficient adjustment range is a preset adjustment range based on the PID control adjustment situation in the specific blow molding scenario. This adjustment range can be, for example, [-0.5, 0.5]. That is, the adjustment of the proportional term is selected within this range. Then, the real-time control index is linearly mapped to the adjustment range to obtain the proportional adjustment index. Since the real-time control index has a value range of [0, 1], the linear mapping within the adjustment range [-0.5, 0.5] requires subtracting 0.5 from the obtained control index value to obtain the proportional adjustment index, which is used to adjust the proportional term.

[0106] In this embodiment of the invention, linear mapping, that is, linearly mapping the real-time control index from the value range of [0,1] to the adjustment range, specifically uses standard linear mapping, that is, linear mapping of the maximum and minimum values, and its formula is: ;

[0107] In the formula, y represents the proportional adjustment index, x represents the control index, oldMin is the minimum value of the control index (0), oldMax is the maximum value of the control index (1), newMax is the maximum value of the control range (0.5), and newMin is the minimum value of the control range (-0.5). Thus, a standardized linear mapping is achieved.

[0108] It should be noted that in this embodiment of the invention, since the value range of the control index itself is [0,1], that is, the value of oldMax-oldMin itself is 1 and not 0, and when the control index has only one value, so that oldMax-oldMin is 0, linear mapping can be skipped and the proportional control index can be directly set to 0 to achieve control analysis.

[0109] After determining the proportional adjustment index value, the sum of the real-time proportional gain coefficient and the proportional adjustment index is used as the adjusted proportional gain value. Then, the adjusted proportional gain value is used as the real-time proportional term for PID control adjustment. When all the preforms have been extruded to the specified length (i.e., the entire mold can be blow-molded), the mold (usually a split mold) is driven by a hydraulic or pneumatic system to move from both sides towards the center until it is completely closed. At the same time as the mold closes, the cutter inside the mold (or the external cutter) cuts the preform from the extruder die, allowing the preform to fully enter the mold cavity. High-pressure compressed air (pressure approximately 0.5-2.0 MPa, depending on the product thickness and material) is introduced into the air inlet on the mold (usually located at the bottom or side of the mold), causing the preform to expand rapidly and adhere tightly to the inner wall of the mold cavity. After subsequent cooling, shaping, and trimming of the flash, the finished product is obtained.

[0110] In this embodiment of the invention, the contour performance of the blow-molded product mold is first analyzed. Based on the diameter of radial points in different vertical directions and the complexity of its own contour, a compression tendency index is determined. Combining the temperature distribution and the compression tendency index, the degree of compression requirement is determined, characterizing the required compression degree in the radial region during extrusion. The compression degree is adjusted by a flexible ring. Furthermore, the sagging performance during the preform extrusion process is analyzed to obtain the preform deformation influence. Combining the compression requirement and the preform deformation influence, the radial compression urgency is determined, enabling real-time control of the radial compression force of the blow molding machine's flexible ring. This invention can effectively analyze the contour complexity, thermoplasticity influence, and sagging performance of different molds, thereby reflecting these dimensions of analysis in the real-time preform extrusion process. Adjusting the blow molding machine's flexible ring achieves real-time radial compression force control, thereby improving the uniformity of the preform wall thickness and enhancing the control accuracy of blow molding uniformity.

[0111] On the other hand, a control device for a hollow blow molding machine that improves blow molding uniformity is also provided. The device includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the method as described in any of the foregoing claims.

[0112] 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.

[0113] 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 control method for a hollow blow molding machine to improve blow molding uniformity, characterized in that, The method includes: Obtain the point cloud model of the mold for the product to be blow molded, and divide the point cloud model into different radial layers evenly in the radial direction. Determine the radial region that matches the real-time extruded preform with each radial layer. The matching includes: mapping the radial layers of the mold onto each preform according to the radial height, and determining the radial region corresponding to each radial layer on each preform; or, performing point cloud detection on the preform, and matching the point cloud model of the radial layers of the mold with the point cloud data model of the preform to determine the matching radial region. Multiple radial points are sampled on average in each radial region to determine the temperature value at each radial point during extrusion; wherein, the temperature value is obtained by detecting the temperature of the melt in that radial region during preform extrusion through a temperature sensing module configured at the die position of the blow molding machine. Based on the diameter distribution of the radial points corresponding to each radial region and the complexity of its own contour, the compression tendency index of the radial region is determined; combined with the temperature distribution and compression tendency index of different radial regions, the compression requirement of each radial region is determined. During the extrusion process, the sagging performance of the radial region is determined based on the change in radial length of the extruded radial region at different sampling times; the deformation influence of the extruded radial region is determined based on the sagging performance of each extruded radial region. The radial compression urgency is obtained by combining the compression requirement of each extruded radial region with the influence of preform deformation; the radial compression force of the flexible ring of the blow molding machine is adjusted in real time based on the radial compression urgency.

2. The method for controlling a hollow blow molding machine to improve blow molding uniformity as described in claim 1, characterized in that, The determination of the compression tendency index of the radial region based on the diameter distribution and the complexity of its contour for each radial region includes: Determine the profile diameter of each radial point; based on the numerical distribution of the profile diameters of all radial points in all radial regions, determine the applicability of the preform in each radial region; The negative number of the application degree of the preform is normalized and used as an indicator of application impact. Calculate the numerical standard deviation of the profile diameter of all radial points in the same radial region, normalize the negative of the standard deviation, and use it as the profile stability coefficient. The product of the profile stability coefficient of the radial region and the applied influence index is calculated as an index of the compression tendency of the radial region.

3. The method for controlling a hollow blow molding machine to improve blow molding uniformity as described in claim 2, characterized in that, The determination of the preform applicability of each radial region based on the numerical distribution of the profile diameter of all radial points in all radial regions includes: Calculate the average of the profile diameters of all radial points in the same radial region, and use this as the region diameter of the radial region; The average diameter of all radial regions is used as the analysis diameter; Calculate the difference between the region diameter and the analysis diameter for each radial region, and normalize the difference as the applicability degree of the preform.

4. The method for controlling a hollow blow molding machine to improve blow molding uniformity as described in claim 2, characterized in that, A temperature sensing module is configured at the die position of the blow molding machine to acquire the temperature value of each radial point in each radial region during extrusion. The degree of compression requirement for each radial region is determined by combining the temperature distribution and compression trend indicators of different radial regions during extrusion, including: The average temperature of all radial points in the same radial region is taken as the region temperature. The regional temperature is normalized by its maximum and minimum values ​​and used as a temperature influence indicator. The product of the temperature influence index and the compression tendency index for each radial region is normalized and used as the compression demand level for that radial region.

5. The method for controlling a hollow blow molding machine to improve blow molding uniformity as described in claim 1, characterized in that, The sagging performance of the radial region is determined based on the change in radial length of the extruded radial region at different sampling times, including: Within the time range of extrusion, different sampling times are evenly divided. For each extruded radial region, the radial length of the corresponding radial region that has been extruded at each sampling time is obtained. The radial length difference between adjacent sampling times is used as the droop factor for the sampling period between adjacent sampling times; The droop trend index is determined based on the change in the droop factor during the sampling period between adjacent sampling times. The mean of the droop factor for all sampling periods in the extruded radial region is normalized and used as the droop analysis index. Calculate the product of the sagging trend index and the sagging analysis index of the extruded radial region as the sagging performance of the radial region.

6. The method for controlling a hollow blow molding machine to improve blow molding uniformity as described in claim 5, characterized in that, Based on the change in the droop factor value during the sampling period between adjacent sampling times, droop trend indicators are determined, including: A two-dimensional rectangular coordinate system is constructed with the sampling period as the x-axis and the droop factor as the y-axis. The coordinate points of the droop factor for each sampling period in the coordinate system are determined. Least squares line fitting is performed on all coordinate points to obtain the fitted line. The normalized slope of the fitted line is determined as an indicator of the downward trend.

7. The method for controlling a hollow blow molding machine to improve blow molding uniformity as described in claim 1, characterized in that, Based on the sagging performance of each extruded radial region, the preform deformation influence of the extruded radial region is determined, including: Calculate the average sagging performance of the same radial region from the initial sampling time to the current sampling time, and normalize it to obtain the deformation influence of the extruded radial region.

8. The control method for improving blow molding uniformity of a hollow blow molding machine as described in claim 1, characterized in that, Combining the compression requirement of each extruded radial region with the influence of preform deformation, the radial compression urgency is obtained, including: The negative number of the influence of embryo deformation was normalized and used as the first urgent indicator; Different preset urgency weights are assigned to the degree of compression demand and the primary urgency index, and the weighted sums and normalization are performed to obtain the radial compression urgency.

9. The control method for improving blow molding uniformity of a hollow blow molding machine as described in claim 1, characterized in that, The radial compression force of the flexible ring in the blow molding machine is adjusted in real time based on the radial compression urgency, including: The average radial compression urgency of all extruded radial regions at the current sampling time is used as the control index; Determine the preset proportional gain coefficient adjustment range, and linearly map the real-time control index to the adjustment range to obtain the proportional control index; The sum of the real-time proportional gain coefficient and the proportional adjustment index is used as the adjusted proportional gain value. The proportional gain value is adjusted and used as the real-time proportional term for PID control.

10. A control device for a hollow blow molding machine to improve blow molding uniformity, the device comprising a memory, a processor, and a computer program stored in the memory and running 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 9.

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