Method, system and device for controlling blow molding machine with uniform product wall thickness

Abstract

The invention relates to the technical field of blow molding machine control, in particular to a blow molding machine control method, system and device capable of achieving uniform product wall thickness. The method specifically comprises the steps that the thermoplastic sensitivity of each monitoring area of a tubular parison is calculated according to the thermal deformation condition and the temperature distribution condition of the tubular parison; determining a corresponding wall side area of each tubular parison monitoring area on the mold, and obtaining an air supply deviation demand degree of each wall side area on the basis of the thermoplastic sensitivity according to the molding contour demand degree expression of each wall side area of the mold and the pressure presentation effect of the wall side; the offset amplitude compensation value is obtained according to the distribution difference of the air supply offset demand degrees of all the wall side areas so as to adjust the proportional gain coefficient, then the PID controller is combined, the air supply outlet can be adjusted adaptively according to the blow molding demand of all the areas in the blow molding fine adjustment stage, and the blow molding precision is improved. And the problem of poor blow molding effect caused by the fact that the air supply outlet always adopts a vertical downward blow molding mode on the tubular parison in the traditional blow molding process is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of blow molding machine control, and in particular to a blow molding machine control method, system, and control device for achieving uniform product wall thickness. Background Art

[0002] A blow molding machine is a plastics processing machine. After spraying liquid plastic, the machine uses the airflow to blow the plastic into a mold cavity of a specific shape, thus creating a product. The blow molding machine's operating process is mainly divided into extrusion and blow molding. In the extrusion process, the thermoplastic raw material is ground and extruded by the screw in the barrel to form a tubular parison. This tubular parison is then blown vertically downward through the air supply port in the mold to form the blow-molded product.

[0003] During the process of blow molding of tubular preforms by traditional blow molding machines, the air outlet blows air in the vertical downward direction inside the mold. However, since the grinding process inside the barrel may not be compatible with the thermoplastic raw materials, there may be differences in the thermoplastic sensitivity of different positions of the tubular preform extruded by the barrel. At the same time, due to the different texture requirements at different contours of the target product, the traditional vertical downward air supply does not take into account the different molding requirements, which leads to the problem of poor uniform wall thickness of the blow-molded products formed by the vertical downward air supply. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a blow molding machine control method, system and control device with uniform product wall thickness. The technical solutions adopted are as follows: In a first aspect, an embodiment of the present application provides a method for controlling a blow molding machine to achieve uniform product wall thickness, the method comprising the following steps: Collect point cloud data of the tubular preform and the inner wall of the mold at each moment, as well as temperature data of each position of the tubular preform and pressure data of each position of the inner wall of the mold; At any moment, a 3D point cloud parison model and a 3D point cloud mold model are constructed; the parison model and the mold model are divided into regions in the same manner to obtain each parison monitoring region and each mold wall region; and the central axis of the parison model is obtained; The thermoplastic sensitivity of each parison monitoring area is calculated based on the distance from the corresponding central axis, the curvature of the upper and lower sections of each parison monitoring area, and the temperature difference between each parison monitoring area and other parison monitoring areas at the same time. Based on the inclination of the tangent plane at each point cloud data point on each mold wall area, as well as the distance from each point cloud data point to a preset reference surface, combined with the thermoplastic sensitivity of the parison monitoring area at the corresponding position on each mold wall area at the same moment, the wind pressure requirement index of each mold wall area is calculated; Based on the changes in historical pressure data at various locations on the mold inner wall corresponding to each mold wall area, combined with the air pressure demand index, an air supply offset requirement for each mold wall area is constructed; within each second segment of the preset fine-tuning phase, the offset trend direction and corresponding compensation offset amplitude for each second segment are determined based on the values ​​and position distribution of all the air supply offset requirements at the starting time; The proportional gain coefficient adjustment value of each second segment is obtained based on the compensation offset amplitude, and the air supply direction of each second segment is controlled in combination with the PID controller and the offset trend direction.

[0005] In one embodiment, the process of obtaining the central axis of the parison model is as follows: The geometric center of the parison model is expanded along the point cloud height coordinate direction to obtain the central axis of the parison model.

[0006] In one embodiment, the process of obtaining the thermoplastic sensitivity of each parison monitoring area is as follows: Calculate the mean of the distances from all point cloud data points in the current parison monitoring area to the corresponding central axis as the distance from the current parison monitoring area to the corresponding central axis, recorded as ; The maximum value of the distance from all the parison monitoring areas of the parison model to the corresponding central axis is recorded as ; Calculate the mean curvature of all point cloud data points on the top tube diameter cross-section curve segment and the bottom tube diameter cross-section curve segment corresponding to the current parison monitoring area as the curvature factor of the cross-section curve segment of the current parison monitoring area ; The deformation degree of the parison tube diameter in the current parison monitoring area is recorded as G, and the expression of G is: ; Calculate the mean of the temperature data at all positions in the parison model, which is recorded as the first mean; calculate the normalized value of the difference between the mean of the temperature data at all positions in the current parison monitoring area and the mean of the temperature data at all positions in the parison model, which is recorded as C; The thermoplastic sensitivity of the current parison monitoring area is calculated and recorded as Q. The expression of Q is: , where is the normalization function.

[0007] In one embodiment, the process of obtaining the wind pressure requirement index of each mold wall area is as follows: Obtaining angle data between a tangent plane at each point cloud data point on each mold wall side region and a preset reference surface; calculating the standard deviation of the angle data for all point cloud data points on each mold wall side region; calculating the sum of the distances from all point cloud data points on each mold wall side region to the preset reference surface; and using the normalized value of the product of the standard deviation and the sum as the molding profile requirement for each mold wall side region; The ratio of the molding profile requirement to the thermoplastic sensitivity of the parison monitoring area at the corresponding position of each mold wall area at the same moment is normalized to obtain the wind pressure requirement index of each mold wall area.

[0008] In one embodiment, the process of obtaining the air supply offset requirement of each mold wall area is as follows: In the current mold wall area, calculate the ratio of the number of positions where the pressure data is greater than 0 to the number of all positions, and use it as the area ratio factor of the current mold wall area. The duration of time when the pressure data at each position is greater than 0 is used as the wall adhesion time at each position. The average wall adhesion time of all positions where the pressure data is greater than 0 in the current mold wall area is calculated and recorded as the average wall adhesion time. ; Mark the wind pressure demand index of the current mold wall area as ; Calculate the air supply offset requirement for the current mold wall area , The expression is: , where is the normalization function.

[0009] In one embodiment, the process of obtaining the offset trend direction and the corresponding compensation offset amplitude of each second segment is as follows: The maximum air supply offset demand in the mold model at the beginning of the current second period is recorded as ,Will The corresponding mold wall side area is used as the target mold wall side area, and the direction in which the air supply port points to the center point of the target mold wall side area is used as the offset trend direction of each second segment; Calculate the average of the air supply offset requirements of all adjacent mold wall areas of the target mold wall area in the mold model; calculate the difference between the air supply offset requirement of the target mold wall area and the average value as the offset requirement adjustment value of the target mold wall area ; Calculate the compensation offset amplitude in the offset trend direction of the current second segment , The expression is: , where is the tanh function.

[0010] In one embodiment, the proportional gain coefficient adjustment value of each second segment is: the product of the compensation offset amplitude of each second segment and the preset initial proportional gain coefficient.

[0011] In one embodiment, the air supply direction is controlled by combining the PID controller and the offset trend direction, specifically: In each second segment, the adjustment value is used as a new proportional gain coefficient of the PID controller to rotate the air outlet in the direction of the corresponding offset trend, and the rotation angle of the air outlet is controlled by the control signal output by the PID controller.

[0012] In a second aspect, an embodiment of the present application further provides a blow molding machine control system for products with uniform wall thickness, wherein a computer program is stored in the system, and when the computer program is executed by a processor, the steps of the method described in the first aspect are implemented.

[0013] In a third aspect, an embodiment of the present application also provides a blow molding machine control device with uniform product wall thickness, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of the method described in the first aspect above when executing the computer program.

[0014] The embodiments of the present application have at least the following beneficial effects: This application first analyzes the thermal deformation and temperature distribution of the tubular parison formed in the extrusion process, constructs the thermoplastic sensitivity of each parison monitoring area, and evaluates the thermoplastic sensitivity of each monitoring area of ​​the tubular parison; constructs the molding contour requirement by the complexity of the mold, and combines the thermoplastic sensitivity to obtain the wind pressure requirement index of each mold wall area, further evaluates the wind force requirement of each area during the parison blow molding process, and then combines the mold wall pressure hysteresis performance in the blow molding stage to obtain the air supply offset requirement; by analyzing the differences in the air supply offset requirements of all areas, the wind pressure of each second is determined. The offset trend direction of the segment and the corresponding compensation offset amplitude are obtained, and the proportional gain coefficient adjustment value of each second segment is obtained based on the compensation offset amplitude. The air supply direction of each second segment is controlled in combination with the PID controller and the offset trend direction. The air supply port can be adaptively adjusted according to the blow molding requirements of each area in the blow molding fine-tuning stage, avoiding the problem of poor blow molding effect caused by the air supply port always adopting a vertical downward blowing mode for the tubular blank in the traditional blow molding process. In the fine-tuning stage, a certain offset compensation is made to the air supply offset amplitude, thereby optimizing the uniformity of product wall thickness and improving the control efficiency of the blow molding machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0016] Figure 1 A flowchart of a method for controlling a blow molding machine to achieve uniform product wall thickness according to an embodiment of the present application; Figure 2 Schematic diagram of the cross section of a tubular blank; Figure 3 The present invention is a flowchart of the steps of a blow molding machine control method for achieving uniform product wall thickness. DETAILED DESCRIPTION

[0017] To further illustrate the technical means and effectiveness of this application's objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a blow molding machine control method, system, and control device for achieving uniform product wall thickness, including its specific implementation, structure, features, and effectiveness. In the following description, references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0018] Unless defined otherwise, 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 application belongs.

[0019] The following describes in detail a method, system and control device for controlling a blow molding machine with uniform product wall thickness provided by the present application with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a flowchart of a method for controlling a blow molding machine for achieving uniform product wall thickness according to an embodiment of the present application, the method comprising the following steps: Step S1 : collecting point cloud data of the tubular preform and the inner wall of the mold at each moment, as well as temperature data of each position of the tubular preform and pressure data of each position of the inner wall of the mold.

[0021] The operation process of the blow molding machine is mainly divided into extrusion process and blow molding process. The extrusion process is completed in the barrel. The thermoplastic raw material is injected into the barrel feed port. The screw in the barrel combined with the high temperature distribution in the barrel makes the raw material be ground into a tubular parison in the barrel, and then transported to the mold from the discharge port. When the tubular parison reaches the blow molding length requirement, the mold is closed, and then the tubular parison is blow-molded by air supply from the air supply port above the mold.

[0022] During blow molding, the laser radar between the mold and the discharge port collects point cloud data of the tubular parison and the inner wall of the mold in real time. The thermal infrared detection equipment between the mold and the discharge port collects temperature data at all positions of the tubular parison in real time. The pressure sensor on the mold wall collects pressure data at all positions on the mold wall during the blow molding stage. It should be noted that when the tubular parison is not attached to the wall in the mold during the inflation process, the wall side pressure data is approximately zero. When it is attached to the wall, the wall side pressure data changes, thereby reflecting the pressure condition of the tubular parison in the mold.

[0023] All temperature data collected at each moment are normalized by the maximum-minimum method to avoid the influence of units and dimensions. In other embodiments of the present application, the implementer may also use other normalization methods to normalize the temperature data.

[0024] Step S2: at any moment, construct a 3D point cloud parison model and a 3D point cloud mold model; divide the parison model and the mold model into regions in the same manner to obtain each parison monitoring region and each mold wall region; and obtain the central axis of the parison model.

[0025] The blow molding machine grinds the thermoplastic raw materials into tubular parisons through the screw in the barrel and the internal high-temperature environment. The tubular parison is extruded vertically downward into the mold below for blowing. However, due to the differences in the physical properties of the raw materials themselves and the grinding accuracy, some raw materials are not ground sufficiently in the barrel, resulting in insufficient thermoplastic sensitivity of the corresponding areas of the produced tubular parisons. The difference in thermoplastic sensitivity of the tubular parisons determines the different requirements for blowing air pressure in subsequent areas. Therefore, the tubular parison is first divided into regions so that the thermoplastic sensitivity of each area on the tubular parison can be evaluated by analyzing the deformation of each area.

[0026] Specifically, when the length of the tubular parison extruded from the barrel reaches the mold closing requirement, a 3D point cloud model of the tubular parison is constructed using the 3D point cloud information collected at each moment, which is referred to as the 3D point cloud parison model. The construction of the 3D point cloud model is well known in the art, and the specific process will not be elaborated upon.

[0027] Similarly, a three-dimensional point cloud model of the inner wall of the mold is constructed using the three-dimensional point cloud information of the inner wall of the mold collected at each moment, which is recorded as a three-dimensional point cloud mold model.

[0028] At each moment, for the three-dimensional point cloud parison model, obtain the top tube diameter section and the bottom tube diameter section of the parison model, set n segmentation points on the top tube diameter section to divide the top tube diameter section into n segments on average; for any segmentation point on the top tube diameter section, find the coordinate point on the plane corresponding to the section that is closest to the two-dimensional coordinate of the segmentation point on the bottom tube diameter section, and use it as the segmentation point corresponding to the segmentation point on the bottom tube diameter section, and connect these two segmentation points to obtain a dividing line on the side wall of the parison model; further, obtain each dividing line on the side wall of the parison model, divide the side wall of the parison model into n monitoring areas, and record each monitoring area of ​​the parison model as each parison monitoring area. Preferably, in the embodiment of the present application, the value of n is set to 10. As other embodiments of the present application, the implementer can set the value of n according to actual conditions.

[0029] Similarly, for a 3D point cloud mold model, obtain the top and bottom cross-sections of the mold model. Connect n segmentation points on the top cross-section with corresponding segmentation points on the bottom cross-section to divide the sidewall surface of the mold model into n monitoring regions. Each monitoring region of the mold model is denoted as a mold wall region. For any mold wall region, calculate the 3D coordinate distance between the center point of that mold wall region and the center point of each parison monitoring region. The parison monitoring region with the closest center point is designated as the corresponding parison monitoring region for that mold wall region.

[0030] Furthermore, the geometric center of the parison model is obtained by using the centroid extraction technology, and the geometric center is expanded along the point cloud height coordinate direction to obtain the central axis of the parison model.

[0031] Step S3 , calculating the thermoplastic sensitivity of each parison monitoring area based on the distance from each parison monitoring area to the corresponding central axis, the curvature of the upper and lower sections of each parison monitoring area, and the temperature difference between each parison monitoring area and other parison monitoring areas at the same time.

[0032] For each area on the barrel extruded tubular parison, if the raw material corresponding to a certain area is sufficiently ground, the thermoplastic sensitivity of the area is higher, and the area is more likely to be thermally deformed. In contrast, it is more difficult for thermal deformation to occur in areas with lower thermoplastic sensitivity. Consequently, areas with relatively high thermoplastic sensitivity are more likely to experience convex deformation with steeper changes in contour curvature, while areas with relatively low thermoplastic sensitivity have more gradual changes in contour curvature. Figure 2 shown.

[0033] Therefore, (1) the distance between each point cloud data point in each parison monitoring area and the central axis of its parison model is obtained, recorded as the first distance; the average of the first distances of all point cloud data points in the parison monitoring area is used as the distance between the parison monitoring area and the central axis of its parison model. The calculation of the point-to-line distance is a well-known technique, and the specific process is not repeated here.

[0034] The maximum value of the distances from all the parison monitoring areas of the parison model to the corresponding central axis is obtained and recorded as the first maximum value.

[0035] The curvature of the cross-sectional coil at each point cloud data point on the top tube diameter section and the bottom tube diameter section of the parison model is calculated respectively; the average value of the curvature of all point cloud data points on the top tube diameter section curve segment and the bottom tube diameter section curve segment corresponding to each parison monitoring area is calculated as the curvature factor of the cross-sectional curve segment of each parison monitoring area.

[0036] Take any parison monitoring area as the current parison monitoring area. Taking the current parison monitoring area as an example, the parison diameter deformation degree of each parison monitoring area is expressed according to the above-analyzed tubular parison contour morphology. The expression is: Where, The deformation degree of the parison tube diameter in the current parison monitoring area; is the curvature factor of the cross-section curve segment in the current parison monitoring area; The distance between the current parison monitoring area and the central axis of its parison model; is the first maximum value of the parison model in the current parison monitoring area.

[0037] The higher the curvature level of the boundary curve segments corresponding to the cross sections at both ends of the current parison monitoring area of ​​the tubular parison, and the farther the parison monitoring area is from the corresponding central axis, the higher the possibility of convex thermal deformation occurring in the parison monitoring area.

[0038] (2) Furthermore, the higher the temperature of the monitoring area on the tubular parison, the higher the heat exchange efficiency of the high temperature environment in the barrel on the thermoplastic raw material. In theory, the thermoplastic sensitivity of this monitoring area should be higher, and the thermoplastic blowing effect is more likely to occur.

[0039] Based on the above analysis, the temperature high presentation coefficient of each parison monitoring area is calculated, specifically: Calculate the mean of the temperature data at all positions in the preform model and record it as the first mean; calculate the difference between the mean of the temperature data at all positions in each preform monitoring area and the first mean of its preform model as the temperature high presentation coefficient of each preform monitoring area; further, normalize the temperature high presentation coefficients of all preform monitoring areas to obtain the normalized value of the temperature high presentation coefficient of each preform monitoring area.

[0040] In the embodiment of the present application, the maximum normalization method is used to normalize the temperature high presentation coefficient. In other embodiments of the present application, the implementer may also use other normalization methods, such as the Z-Score algorithm, to normalize the temperature high presentation coefficient.

[0041] The higher the temperature level of the current parison monitoring area of ​​the tubular parison is compared with the overall level, the greater the possibility of high thermoplastic sensitivity of the monitoring area is.

[0042] Furthermore, the thermoplastic sensitivity of each parison monitoring area is calculated, and the expression is: Where Q is the thermoplastic sensitivity of the current parison monitoring area; G is the parison tube diameter deformation in the current parison monitoring area; C is the normalized value of the temperature-high presentation coefficient in the current parison monitoring area; The normalization function is a sigmoid function. In other embodiments of the present invention, the implementer may also use other normalization functions for normalization.

[0043] The deformation degree of the tubular parison tube diameter in the current monitoring area The higher the temperature, the higher the coefficient of The larger the value is, the stronger the thermoplastic sensitivity of the monitoring area is, and thus the greater the thermoplastic sensitivity of the current monitoring area of ​​the tubular blank is.

[0044] Step S4: Calculate the wind pressure requirement index for each mold wall area based on the degree of inclination of the tangent plane at each point cloud data point on each mold wall area, the distance from each point cloud data point to a preset reference surface, and the thermoplastic sensitivity of the parison monitoring area at the corresponding position of each mold wall area at the same moment.

[0045] After the mold is closed, the tubular parison produced by the barrel is blown by inputting air pressure into the mold through the air supply port on the top of the mold. Thermoplastic sensitivity is one of the factors affecting the air pressure demand, but it should also be analyzed in conjunction with the complex requirements of the inner wall of the mold.

[0046] The contour complexity of different wall areas of the mold may vary due to different design requirements. If the contour complexity of a certain wall area of ​​the mold is high, the wall area involved will be larger after the area is completely flat and unfolded, and higher wind pressure support will be required during inflation. Otherwise, the wall thickness of this wall area may be relatively too thick after the product is manufactured.

[0047] Therefore, based on the above analysis, the molding profile requirement of each mold wall area is calculated.

[0048] Specifically, for the three-dimensional point cloud mold model, the central axis of the mold model is determined using the same acquisition method as the central axis of the parison model. Furthermore, the geometric center of each mold wall side region of the mold model is obtained, and a perpendicular line is drawn through the geometric center to the central axis of the mold model. A plane perpendicular to the perpendicular line through the central axis is used as a reference plane for each mold wall side region. Obtain the tangent plane at each point cloud data point on each mold wall side area, calculate the angle data between the tangent plane and the corresponding reference surface; calculate the standard deviation of the angle data for all point cloud data points on each mold wall side area The process of obtaining the tangent plane of a point on the surface and the process of calculating the angle between two planes are both well-known technologies, and the specific processes will not be repeated here.

[0049] Calculate the distance between each point cloud data point on each mold wall side area and the corresponding reference surface, which is recorded as the second distance; calculate the sum of the second distances of all point cloud data points on each mold wall side area; Based on the above analysis, any mold wall area is taken as the current mold wall area. Taking the current mold wall area as an example, the molding contour requirement of each mold wall area is calculated. The expression is: Where, The current molding contour requirement of the mold wall area; is the standard deviation of the angle data of all point cloud data points on the current mold wall side area; A is the sum of the second distances of all point cloud data points on the current mold wall side area; As a normalization function, this application uses the sigmoid function for normalization.

[0050] The greater the difference in angles between the tangent planes at each point on the wall side area, the more tortuous the wall side profile is, which means that more wall side area is involved. In this case, a greater wind pressure should be compensated for the wall side area. At the same time, the greater the distance from each point on the wall side area to the reference surface, the farther the wall side area is from the reference surface, and the greater the loss in the process of wind pressure transmission to the wall side, which further indicates that a greater wind pressure should be compensated for the wall side area at this time.

[0051] Furthermore, for a single wall area on the mold, if the thermoplastic sensitivity of the wall area in the corresponding monitoring area in the parison model is smaller, it means that the wall area requires higher wind pressure compensation to achieve the same thermoplastic effect as other areas. At the same time, the plastic contour requirement of the wall area is The higher the value, the higher the wind pressure compensation requirement of the wall area. Therefore, the wind pressure requirement index of the current mold wall area is calculated as follows: Where, It is the wind pressure demand index of the current mold wall area; The current molding contour requirement of the mold wall area; The thermoplastic sensitivity of the parison monitoring area corresponding to the current mold wall area; ] is a normalization function, and the present application adopts a sigmoid function for normalization. As other embodiments of the present application, the implementer may also adopt other normalization functions for normalization.

[0052] Step S5, based on the changes in historical pressure data of each position on the inner wall surface of the mold corresponding to each mold wall side area, combined with the wind pressure demand index, construct the air supply offset demand degree of each mold wall side area; in each second segment of the preset fine-tuning stage, determine the offset trend direction and corresponding compensation offset amplitude of each second segment based on the numerical value and position distribution of all the air supply offset demands at the starting time.

[0053] (1) A fine-tuning stage is set during the blow molding process. In the embodiment of the present application, the fine-tuning stage is entered when the area of ​​the parison adhering to the wall accounts for 70% of the total area of ​​the inner wall of the mold. Before the fine-tuning stage, the air outlet is always in a normal vertical downward blowing state. After entering the fine-tuning stage, it is converted to a fine-tuning state in which the air outlet is adjustable. In other embodiments of the present application, the implementer can set the start time of the fine-tuning stage according to actual conditions.

[0054] The process of obtaining the parison wall-adhering area is as follows: calculate the pressure data of all positions on the inner wall of the mold at any moment, and the ratio of the number of positions with the same pressure data greater than 0 to the number of all positions is used as the parison wall-adhering area at that moment.

[0055] At the initial moment of the fine-tuning stage, part of the tubular preform in the mold may have already adhered to the wall, while part may not. The part that has already adhered to the wall also has a priority in terms of wall adhesion time. If the wall adhesion time is longer, the wall thickness of this part of the tubular preform area will be thinner than that of other areas. In order to improve the uniformity of the overall wall thickness of the product, a greater compensating air pressure needs to be applied to the areas that are late attached to the wall or not attached to the wall. The pressure hysteresis can reflect the wall adhesion hysteresis performance. Therefore, the pressure hysteresis performance is analyzed based on the air pressure demand index to obtain the air supply offset demand of the wall side area in the fine-tuning stage.

[0056] Specifically, at any moment, the ratio of the number of positions in each mold wall side area where the pressure data is greater than 0 to the number of all positions in the mold wall side area is calculated as the area ratio factor of each mold wall side area at that moment; in the historical pressure data of each position, the moment when the pressure data starts to be greater than 0 is obtained as the starting moment of wall adhesion for each position, and the time from the starting moment of wall adhesion for each position to the current moment is used as the wall adhesion time of each position at the current moment, and the average wall adhesion time of all positions where the pressure data is greater than 0 in each mold wall side area at the current moment is calculated and recorded as the average wall adhesion time.

[0057] Furthermore, the air supply offset requirement of each mold wall area is calculated using the following expression: Where, is the air supply offset requirement of the current mold wall area; V is the area ratio factor of the current mold wall area; is the average duration of adhesion to the wall of the current mold wall area; It is the wind pressure demand index of the current mold wall area; ] is a normalization function, and the present application adopts a sigmoid function for normalization. As other embodiments of the present application, the implementer may also adopt other normalization functions for normalization.

[0058] The shorter the wall-adhering time of the wall-adhering area inside the current mold wall side area and the smaller the proportion of the wall-adhering area in the total area, the slower the wall-adhering performance of this wall side area. If the wind pressure demand index of this wall side area is greater at the same time, it further indicates that the compensatory wind pressure demand performance of this mold wall side area during the fine-tuning stage is higher.

[0059] (2) In a single second segment of the fine-tuning phase, the mold wall area corresponding to the maximum air supply offset demand of all mold wall areas in the mold model at the start time is selected as the target mold wall area at the start time, and the direction of the air supply port pointing to the center point of the target mold wall area is used as the offset trend direction of the air supply port in this second segment. In this second segment, the air supply port is offset in the offset trend direction. The closer the air pressure direction of the air supply port is to the wall side with high demand, the higher the beneficial air pressure compensated at the wall side. The duration of the single second segment is 1 second.

[0060] Then, the specific deviation amplitude of the air supply pressure in the deviation trend direction is analyzed. When the air supply pressure deflects to a certain side in the mold, all wall areas of the mold on that side will be compensated by the wind pressure. Therefore, it is necessary not only to analyze the wall area with the highest wind pressure demand index, but also to combine the performance of the adjacent wall areas. That is, if the wind pressure demand index level of the adjacent wall area is relatively low, the deviation amplitude can be appropriately adjusted down.

[0061] Therefore, the specific compensation offset amplitude of the air outlet in the offset trend direction within a single second period during the fine-tuning stage is calculated as follows: The a number of mold wall regions closest to the target mold wall region in the mold model are defined as neighboring mold wall regions of the target mold wall region; an average of the air supply offset requirements of all neighboring mold wall regions of the target mold wall region is calculated, recorded as a second mean; and a difference between the air supply offset requirement of the target mold wall region and the second mean is calculated as an adjustment amount for the offset requirement of the target mold wall region. Calculate the compensation offset amplitude of the air outlet in the direction of the mold's inward offset in a single second segment during the fine-tuning phase. The expression is: Where, The compensation offset amplitude in the offset trend direction of the current second segment; The maximum value of the air supply offset demand at the start of the current second segment; The offset adjustment required for the target mold wall area at the start of the current second segment; is the tanh function.

[0062] The higher the air supply offset requirement of the wall side area in the offset trend direction, and the smaller the difference in air supply offset requirement between other wall side areas on the offset side and the wall side area, the larger the compensation offset amplitude can be applied to the offset trend direction of the second segment.

[0063] Step S6: obtaining a proportional gain coefficient adjustment value for each second segment based on the compensation offset amplitude, and controlling the air supply direction for each second segment in combination with a PID controller and the offset trend direction.

[0064] First, in the embodiment of the present application, the value of the initial proportional gain coefficient is set to 10. As other embodiments of the present application, the implementer can set the initial proportional gain coefficient according to the actual situation. Then, the product of the compensation offset amplitude of each second segment and the initial proportional gain coefficient is used as the proportional gain coefficient adjustment value of each second segment, and the adjustment value is re-input into the PID control chip as the new proportional gain coefficient of the PID controller; then, the control signal output by the PID controller is used to control the angle of rotation of the air outlet of each second segment, wherein the rotation direction of the air outlet is the offset trend direction of the air outlet of each second segment.

[0065] The parameters of the PID controller are dynamically updated during the continuous blow molding monitoring process to ensure the stability of the control of the uniformity of the product wall thickness during the processing.

[0066] A flowchart of a blow molding machine control method for uniform product wall thickness is shown below: Figure 3 shown.

[0067] Based on the same inventive concept as the above method, an embodiment of the present application also provides a blow molding machine control system for products with uniform wall thickness, wherein a computer program is stored in the system, and when the computer program is executed by the processor, the steps of any one of the above-mentioned methods for controlling a blow molding machine for products with uniform wall thickness are implemented.

[0068] Based on the same inventive concept as the above method, an embodiment of the present application also provides a blow molding machine control device with uniform product wall thickness, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned methods for controlling a blow molding machine with uniform product wall thickness are implemented.

[0069] In summary, the embodiment of the present application provides a method for controlling a blow molding machine with uniform product wall thickness, by analyzing the thermal deformation and temperature distribution of the tubular parison formed in the extrusion process, constructing the thermoplastic sensitivity of each parison monitoring area, and evaluating the thermoplastic sensitivity of each monitoring area of ​​the tubular parison; constructing the molding contour requirement by the complexity of the mold, combining the thermoplastic sensitivity, obtaining the wind pressure requirement index of each mold wall area, further evaluating the wind force requirement of each area during the parison blow molding process, and then combining the mold wall pressure hysteresis performance in the blow molding stage to obtain the air supply offset requirement; by analyzing the air supply of all areas The difference in the degree of offset demand determines the offset trend direction and the corresponding compensation offset amplitude of each second segment, and the proportional gain coefficient adjustment value of each second segment is obtained based on the compensation offset amplitude. The air supply direction of each second segment is controlled in combination with the PID controller and the offset trend direction; the air supply port can be adaptively adjusted according to the blow molding requirements of each area in the blow molding fine-tuning stage, avoiding the problem of poor blow molding effect caused by the air supply port always adopting a vertical downward blowing mode for the tubular parison in the traditional blow molding process. In the fine-tuning stage, a certain offset compensation is performed on the air supply offset amplitude, thereby optimizing the uniformity of product wall thickness and improving the control efficiency of the blow molding machine.

[0070] It should be noted that the order in which the embodiments of the present application are presented is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the above descriptions are of specific embodiments of the present application. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0071] The various embodiments in this application are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0072] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for controlling a blow molding machine to achieve uniform product wall thickness, characterized in that: The method comprises the following steps: Collect point cloud data of the tubular preform and the inner wall of the mold at each moment, as well as temperature data of each position of the tubular preform and pressure data of each position of the inner wall of the mold; At any moment, a 3D point cloud parison model and a 3D point cloud mold model are constructed; the parison model and the mold model are divided into regions in the same manner to obtain each parison monitoring region and each mold wall region; and the central axis of the parison model is obtained; The thermoplastic sensitivity of each parison monitoring area is calculated based on the distance from the corresponding central axis, the curvature of the upper and lower sections of each parison monitoring area, and the temperature difference between each parison monitoring area and other parison monitoring areas at the same time. Based on the inclination of the tangent plane at each point cloud data point on each mold wall area, as well as the distance from each point cloud data point to a preset reference surface, combined with the thermoplastic sensitivity of the parison monitoring area at the corresponding position on each mold wall area at the same moment, the wind pressure requirement index of each mold wall area is calculated; Based on the changes in historical pressure data at various locations on the mold inner wall corresponding to each mold wall area, combined with the air pressure demand index, an air supply offset requirement for each mold wall area is constructed; within each second segment of the preset fine-tuning phase, the offset trend direction and corresponding compensation offset amplitude for each second segment are determined based on the values ​​and position distribution of all the air supply offset requirements at the starting time; The proportional gain coefficient adjustment value of each second segment is obtained based on the compensation offset amplitude, and the air supply direction of each second segment is controlled in combination with the PID controller and the offset trend direction.

2. A method for controlling a blow molding machine with uniform product wall thickness according to claim 1, characterized in that: The process of obtaining the central axis of the parison model is as follows: The geometric center of the parison model is expanded along the point cloud height coordinate direction to obtain the central axis of the parison model.

3. A method for controlling a blow molding machine with uniform product wall thickness according to claim 1, characterized in that: The process of obtaining the thermoplastic sensitivity of each parison monitoring area is as follows: Calculate the mean of the distances from all point cloud data points in the current parison monitoring area to the corresponding central axis as the distance from the current parison monitoring area to the corresponding central axis, recorded as ; The maximum distance from all the parison monitoring areas of the parison model to the corresponding central axis is recorded as ; Calculate the mean curvature of all point cloud data points on the top tube diameter cross-section curve segment and the bottom tube diameter cross-section curve segment corresponding to the current parison monitoring area as the curvature factor of the cross-section curve segment of the current parison monitoring area ; The deformation degree of the parison tube diameter in the current parison monitoring area is recorded as G, and the expression of G is: ; Calculate the mean of the temperature data at all positions in the parison model, and record it as the first mean; Calculate the normalized value of the difference between the mean of the temperature data of all positions in the current parison monitoring area and the mean of the temperature data of all positions in its parison model, and record it as C; The thermoplastic sensitivity of the current parison monitoring area is calculated and recorded as Q. The expression of Q is: , where is the normalization function.

4. A method for controlling a blow molding machine with uniform product wall thickness according to claim 1, characterized in that: The process of obtaining the wind pressure demand index of each mold wall area is as follows: Obtaining angle data between a tangent plane at each point cloud data point on each mold wall side region and a preset reference plane; calculating the standard deviation of the angle data for all point cloud data points on each mold wall side region; Calculating the sum of the distances from all point cloud data points on each mold wall side area to a preset reference surface; and using the normalized value of the product of the standard deviation and the sum as the molding contour requirement of each mold wall side area; The ratio of the molding profile requirement to the thermoplastic sensitivity of the parison monitoring area at the corresponding position of each mold wall area at the same moment is normalized to obtain the wind pressure requirement index of each mold wall area.

5. A method for controlling a blow molding machine with uniform product wall thickness according to claim 1, characterized in that: The process of obtaining the air supply deviation requirement of each mold wall area is as follows: In the current mold wall area, calculate the ratio of the number of positions where the pressure data is greater than 0 to the number of all positions, and use it as the area ratio factor of the current mold wall area. The duration of time when the pressure data at each position is greater than 0 is used as the wall adhesion time at each position. The average wall adhesion time of all positions where the pressure data is greater than 0 in the current mold wall area is calculated and recorded as the average wall adhesion time. ; Mark the wind pressure demand index of the current mold wall area as ; Calculate the current air supply offset requirement for the mold wall area , The expression is: , where is the normalization function.

6. A method for controlling a blow molding machine with uniform product wall thickness according to claim 1, characterized in that: The process of obtaining the offset trend direction and the corresponding compensation offset amplitude of each second segment is as follows: The maximum air supply offset demand in the mold model at the beginning of the current second period is recorded as ,Will The corresponding mold wall side area is used as the target mold wall side area, and the direction in which the air supply port points to the center point of the target mold wall side area is used as the offset trend direction of each second segment; Calculate an average of the air supply offset requirements of all adjacent mold wall side areas of the target mold wall side area in the mold model; Calculate the difference between the air supply offset requirement of the target mold wall area and the average value as the offset requirement adjustment amount of the target mold wall area ; Calculate the compensation offset amplitude in the offset trend direction of the current second segment , The expression is: , where is the tanh function.

7. A method for controlling a blow molding machine with uniform product wall thickness as claimed in claim 1, characterized in that: The proportional gain coefficient adjustment value of each second segment is: the product of the compensation offset amplitude of each second segment and the preset initial proportional gain coefficient.

8. A method for controlling a blow molding machine with uniform product wall thickness as claimed in claim 1, characterized in that: The air supply direction is controlled by combining the PID controller and the offset trend direction, specifically: In each second segment, the adjustment value is used as a new proportional gain coefficient of the PID controller to rotate the air outlet in the direction of the corresponding offset trend, and the rotation angle of the air outlet is controlled by the control signal output by the PID controller.

9. A blow molding machine control system for uniform product wall thickness, wherein a computer program is stored in the system, characterized in that: When the computer program is executed by a processor, the steps of a method for controlling a blow molding machine for achieving uniform product wall thickness as described in any one of claims 1 to 8 are implemented.

10. A blow molding machine control device for uniform product wall thickness, 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, the steps of the method for controlling a blow molding machine with uniform product wall thickness as described in any one of claims 1 to 8 are implemented.

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