A method, system and control device for controlling a blow molding machine to produce a product with uniform wall thickness

Abstract

The application relates to the technical field of blow molding machine control, in particular to a blow molding machine control method, system and device for uniform product wall thickness, which specifically comprises the following steps: calculating the thermoplastic sensitivity of each monitoring area of a tubular parison by the hot deformation and temperature distribution of the tubular parison, determining the corresponding wall side area of each monitoring area of the tubular parison on a mold, and obtaining the air supply offset requirement degree of each wall side area on the basis of the thermoplastic sensitivity, the molding profile requirement degree performance of each wall side area of the mold and the pressure presentation effect of the wall side, obtaining an offset amplitude compensation value according to the distribution difference of the air supply offset requirement degree of each wall side area, adjusting the proportional gain coefficient, and then combining a PID controller to adaptively adjust the air supply port according to the blow molding requirement of each area in the blow molding fine adjustment stage, so that the problem that the blow molding effect is poor due to the fact that the air supply port always adopts a vertical downward blow molding mode for the tubular parison in the traditional blow molding process is solved.

Description

TECHNICAL FIELD

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

[0002] A blow molding machine is a plastic processing machine. After liquid plastic is sprayed out, the wind force blown out by the machine is used to blow the plastic body to a certain shape of a mold cavity to form a product. The operation process of the blow molding machine mainly includes an extrusion process and a blow molding process. The thermoplastic raw material is ground and extruded by a screw in a barrel in the extrusion process to form a tubular parison, and then the tubular parison is vertically downward blown in the mold through a blow port to form a blow molding product.

[0003] In the process of blow molding of the traditional blow molding machine, the blow port blows vertically downward along the vertical downward direction in the mold. However, since the grinding process in the barrel may not be suitable for the thermoplastic raw material, the thermoplastic sensitivity may be different at different positions of the tubular parison extruded by the barrel. In addition, since the texture requirements of the target product are different at different positions, the different molding requirements are not considered in the traditional vertical downward blowing, thereby causing the problem of poor uniformity of the wall thickness of the blow molding product formed by the vertical downward blowing. SUMMARY

[0004] To solve the above technical problems, the purpose of the present application is to provide a blow molding machine control method, system and device for uniform product wall thickness, and the technical solution is as follows:

[0005] In the first aspect, the application provides a blow molding machine control method for uniform product wall thickness, which comprises the following steps:

[0006] Collecting point cloud data of the tubular parison and the inner wall surface of the mold at each moment, and temperature data of each position of the tubular parison and pressure data of each position of the inner wall surface of the mold;

[0007] At any moment, a three-dimensional point cloud parison model and a three-dimensional point cloud mold model are constructed; the parison model and the mold model are divided into regions in the same way to obtain each parison monitoring region and each mold wall region; and the center axis of the parison model is obtained;

[0008] Based on the distance from each parison monitoring region to the corresponding center axis and the bending degree of the upper and lower cross sections of each parison monitoring region, and in combination with the temperature difference between each parison monitoring region and other parison monitoring regions at the same moment, the thermoplastic sensitivity of each parison monitoring region is calculated.

[0009] The wind pressure demand index of each mold wall side region is calculated based on the inclination degree of the tangent plane at each point cloud data point on the region and the distance from each point cloud data point to a preset reference surface, and the thermoplastic sensitivity of the corresponding position of the parison monitoring region of each mold wall side region at the same time;

[0010] Based on the change of the historical pressure data of each position on the corresponding inner wall surface of each mold wall side region, and in combination with the wind pressure demand index, the air supply offset demand degree of each mold wall side region is constructed; in each second segment of the preset fine adjustment stage, the offset trend direction and the corresponding compensation offset amplitude of each second segment are determined based on the numerical value and position distribution of all the air supply offset demand degrees at the starting time;

[0011] Based on the compensation offset amplitude, the proportional gain coefficient adjustment value of each second segment is obtained, and in combination with the PID controller and the offset trend direction, the air supply direction control of each second segment is performed.

[0012] In one embodiment, the process of obtaining the center axis of the parison model is as follows:

[0013] The geometric center of the parison model is extended along the point cloud height coordinate direction to obtain the center axis of the parison model.

[0014] In one embodiment, the process of obtaining the thermoplastic sensitivity of each parison monitoring region is as follows:

[0015] The average distance of all point cloud data points in the current parison monitoring region to the corresponding center axis is calculated as the distance of the current parison monitoring region to the corresponding center axis, denoted as The maximum distance of all parison monitoring regions of the parison model to the corresponding center axis is denoted as The average curvature of all point cloud data points on the corresponding top pipe diameter cross-sectional curve segment and bottom pipe diameter cross-sectional curve segment of the current parison monitoring region is calculated as the cross-sectional curve segment curvature factor of the current parison monitoring region, denoted as The parison pipe diameter deformation degree of the current parison monitoring region is denoted as G, and the expression of G is: ;

[0016] The average value of all temperature data in the parison model is calculated and denoted as the first average value; the normalized value of the difference between the average value of all temperature data in the current parison monitoring region and the average value of all temperature data in the parison model is calculated and denoted as C;

[0017] The thermoplastic sensitivity of the current parison monitoring region is calculated and denoted as Q, and the expression of Q is: , wherein is a normalization function.

[0018] In one embodiment, the process of obtaining the air pressure demand index of each mold wall side region is as follows:

[0019] Obtaining the included angle data between the tangent plane at each point cloud data point on each mold wall side region and the preset reference surface; calculating the standard deviation of the included angle data of 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 taking the normalized value of the product of the standard deviation and the sum as the molding profile demand degree of each mold wall side region.

[0020] Normalizing the ratio of the molding profile demand degree and the heat plasticity sensitivity of the corresponding position of the parison monitoring region at the same time to obtain the air pressure demand index of each mold wall side region.

[0021] In one embodiment, the process of obtaining the air supply offset demand degree of each mold wall side region is as follows:

[0022] In the current mold wall side region, the ratio of the number of positions with pressure data greater than 0 to the total number of positions is calculated as the area proportion factor of the current mold wall side region. The length of time when the pressure data of each position is greater than 0 is taken as the wall sticking time of each position, and the average wall sticking time of all positions with pressure data greater than 0 in the current mold wall side region is calculated and denoted as wall sticking average time. The air pressure demand index of the current mold wall side region is denoted as The air supply offset demand degree of the current mold wall side region is calculated as , The expression is as follows: , wherein is a normalization function.

[0023] In one embodiment, the process of obtaining the offset trend direction and the corresponding compensation offset amplitude of each second segment is as follows:

[0024] The maximum value of the air supply offset demand degree in the mold model at the start time of the current second segment is denoted as , and the corresponding mold wall side region is taken as the target mold wall side region. The direction of the air supply port pointing to the center point of the target mold wall side region is taken as the offset trend direction of each second segment.

[0025] The average value of the air supply offset demand degrees of all adjacent mold wall side regions of the target mold wall side region in the mold model is calculated. The difference between the air supply offset demand degree of the target mold wall side region and the average value is taken as the offset demand degree adjustment amount of the target mold wall side region.

[0026] The compensation offset amplitude in the offset trend direction of the current second segment is calculated , The expression is: , wherein, is a tanh function.

[0027] 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 a preset initial proportional gain coefficient.

[0028] In one embodiment, the air supply direction control is performed in combination with the PID controller and the offset trend direction, specifically:

[0029] In each second segment, the adjustment value is taken as a new proportional gain coefficient of the PID controller, the air supply outlet is rotated to the corresponding offset trend direction, and the rotation angle of the air supply outlet is controlled by the control signal output by the PID controller.

[0030] In a second aspect, the embodiments of the present application further provide a product wall thickness uniformity blow molding machine control system, wherein a computer program is stored in the system, and the computer program is executed by a processor to implement the steps of the method in the first aspect.

[0031] In a third aspect, the embodiments of the present application further provide a product wall thickness uniformity blow molding machine control device, which comprises a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of the method in the first aspect when executing the computer program.

[0032] The embodiments of the present application have at least the following beneficial effects:

[0033] The application firstly analyzes the heat deformation and temperature distribution of the tubular parison formed by the extrusion process, constructs the heat plasticity sensitivity of each parison monitoring area, evaluates the heat plasticity sensitivity of each monitoring area of the tubular parison, constructs the plastic profile requirement degree through the complexity of the mold, obtains the air pressure requirement index of each mold wall side area in combination with the heat plasticity sensitivity, further evaluates the air requirement required by each area in the parison blowing process, and then obtains the air supply offset requirement degree in combination with the mold wall side pressure lag performance in the blowing stage; the offset trend direction and the corresponding compensation offset amplitude of each second segment are determined by analyzing the difference of the air supply offset requirement degree of all areas, the proportional gain coefficient adjustment value of each second segment is obtained based on the compensation offset amplitude, and the air supply direction control of each second segment is performed in combination with the PID controller and the offset trend direction; the air supply port can be adjusted according to the blowing requirement of each area in the blowing fine-tuning stage, so as to avoid the problem that the blowing effect is poor due to the vertical downward blowing mode of the air supply port to the tubular parison in the traditional blowing process, and the air supply offset amplitude is offset compensated in the fine-tuning stage, so as to optimize the product wall thickness uniformity and improve the control efficiency of the blowing machine. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 A step flow chart of a product wall thickness uniformity blowing machine control method provided by an embodiment of the present application;

[0036] Figure 2 A schematic diagram of a tubular parison cross section;

[0037] Figure 3 A step block diagram of a product wall thickness uniformity blowing machine control method. DETAILED DESCRIPTION

[0038] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the specific implementation, structure, features and effects of the product wall thickness uniformity blowing machine control method, system and control device according to the present application are described in detail as follows in combination with the drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0039] 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 application belongs.

[0040] The application provides a product wall thickness uniform blow molding machine control method, system and control device.

[0041] Please refer to Figure 1 , which shows a product wall thickness uniform blow molding machine control method provided by an embodiment of the application, which comprises the following steps:

[0042] Step S1, collect point cloud data of the tubular parison and the inner wall surface of the mold at each time, and temperature data of each position of the tubular parison and pressure data of each position of the inner wall surface of the mold.

[0043] The blow molding machine operation process mainly includes an extrusion process and a blow molding process. The extrusion process is completed in a barrel. The thermoplastic raw material is injected into the feeding port of the barrel. The screw in the barrel combines the high temperature distribution in the barrel to grind the raw material into a tubular parison, which is then transported to the mold through the discharge port. When the tubular parison reaches the required blow molding length, the mold is closed, and then the tubular parison is blown by the air supply port above the mold.

[0044] During blow molding, the point cloud data of the tubular parison and the point cloud data of the inner wall surface of the mold are collected in real time by the laser radar between the mold and the discharge port; the temperature data of each position of the tubular parison is collected in real time by the thermal infrared detection device between the mold and the discharge port; the pressure data of each position of the mold wall side during the blow molding stage is collected in real time by the pressure sensor on the mold wall side.

[0045] It should be noted that when the tubular parison is not in contact with the mold during the blow molding process, the wall side pressure data is approximately zero. When the tubular parison is in contact with the mold, the wall side pressure data changes, thereby reflecting the pressure condition of the tubular parison in the mold.

[0046] All temperature data collected at each time is normalized by the maximum-minimum value method to avoid the influence of units and dimensions. In other embodiments of the application, the implementer can also use other normalization methods to normalize the temperature data.

[0047] Step S2, at any time, construct a three-dimensional point cloud parison model and a three-dimensional point cloud mold model; divide the parison model and the mold model in the same way to obtain each parison monitoring area and each mold wall side area; obtain the center axis of the parison model.

[0048] The blow molding machine grinds the thermoplastic raw material into a tubular parison through the screw in the barrel and the high temperature environment inside. The tubular parison is extruded vertically downward into the lower mold for blowing. Due to the difference in physical properties of the raw material itself and the grinding accuracy, the grinding sufficiency of part of the raw material in the barrel is insufficient, which leads to the insufficient thermoplastic sensitivity of the corresponding area of the tubular parison in production. The difference in thermoplastic sensitivity of the tubular parison determines the different requirements for blowing air pressure in the subsequent areas. Therefore, the tubular parison is first divided into regions, so as to evaluate the thermoplastic sensitivity of each region on the tubular parison by analyzing the deformation of each region.

[0049] Specifically, when the length of the tubular parison extruded by the barrel reaches the mold closing requirement, a three-dimensional point cloud model of the tubular parison is constructed by collecting three-dimensional point cloud information of the tubular parison at each time, which is denoted as a three-dimensional point cloud parison model. The construction of the three-dimensional point cloud model is a known technology, and the specific process will not be described again.

[0050] Similarly, a three-dimensional point cloud model of the inner wall surface of the mold is constructed by collecting three-dimensional point cloud information of the inner wall surface of the mold at each time, which is denoted as a three-dimensional point cloud mold model.

[0051] At each time, for the three-dimensional point cloud parison model, the top pipe diameter section and the bottom pipe diameter section of the parison model are obtained, and the top pipe diameter section is evenly divided into n segments by setting n segment points on the top pipe diameter section. For any segment point on the top pipe diameter section, find the coordinate point on the two-dimensional coordinate plane of the corresponding section surface that is closest to the two-dimensional coordinate of the segment point on the bottom pipe diameter section, as the corresponding segment point of the segment point on the bottom pipe diameter section, and connect the two segment points to obtain a division line of the side wall surface of the parison model. Further, the side wall surface of the parison model is divided into n monitoring regions by obtaining each division line of the side wall surface of the parison model, and each monitoring region of the parison model is denoted as each parison monitoring region. 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 the actual situation.

[0052] Similarly, for the three-dimensional point cloud mold model, the top section and the bottom section of the mold model are obtained, and the side wall surface of the mold model is also divided into n monitoring regions by connecting the n segment points on the top section with the corresponding segment points on the bottom section. Each monitoring region of the mold model is denoted as each mold wall side region. For any mold wall side region, the distance between the three-dimensional coordinates of the center point of the mold wall side region and the center point of each parison monitoring region is calculated, and the parison monitoring region with the closest center point distance is taken as the corresponding parison monitoring region of the mold wall side region.

[0053] Further, the geometric center of the parison model is obtained by the centroid extraction technology, and the geometric center is expanded along the point cloud height coordinate direction to obtain the center axis of the parison model.

[0054] Step S3, based on the distance of each parison monitoring area to the corresponding center axis, and the bending degree of the upper and lower sections of each parison monitoring area, combined with the temperature difference of each parison monitoring area and other parison monitoring areas at the same time, the heat plasticity sensitivity of each parison monitoring area is calculated.

[0055] For each region on the extruded tubular parison of the barrel, if the corresponding raw material of a region is more fully ground, the heat plasticity sensitivity of the region is higher, and the heat deformation of the region is more likely to occur. The heat deformation in the region with lower heat plasticity sensitivity is more difficult, and the profile curvature change of the region with relatively high heat plasticity sensitivity is more likely to occur. The profile curvature change of the region with relatively low heat plasticity sensitivity is more moderate. As shown in Figure 2 .

[0056] Therefore, (1) the distance of each point cloud data point in each parison monitoring area to the center axis of its parison model is obtained, which is denoted as the first distance; the average of the first distances of all point cloud data points in the parison monitoring area is taken as the distance of the parison monitoring area to the center axis of its parison model. Wherein. The calculation of the distance from a point to a line is a known technology, and the specific process will not be repeated.

[0057] The maximum value of the distance of all parison monitoring areas of the parison model to the corresponding center axis is obtained, which is denoted as the first maximum value.

[0058] The curvature of the cross-sectional coil at each point cloud data point on the top pipe diameter section and the bottom pipe diameter section of the parison model is calculated respectively; the average of the curvatures of all point cloud data points on the top pipe diameter section curve segment and the bottom pipe diameter section curve segment corresponding to each parison monitoring area is taken as the cross-sectional curve segment curvature factor of each parison monitoring area.

[0059] Any one parison monitoring area is taken as the current parison monitoring area. Taking the current parison monitoring area as an example, the parison pipe diameter deformation degree of each parison monitoring area is expressed according to the profile shape of the tubular parison analyzed above, and the expression is:

[0060]

[0061] In the formula, is the parison pipe diameter deformation degree of the current parison monitoring area; is the cross-sectional curve segment curvature factor of the current parison monitoring area; is the distance of the current parison monitoring area to the center axis of its parison model; is the first maximum value of the parison model where the current parison monitoring area is located.

[0062] The higher the curvature level of the corresponding boundary curve segment of the cross section of the current parison monitoring area of the tubular parison is, and the farther the parison monitoring area is from the corresponding central axis, the higher the possibility of the parison monitoring area to occur convex folding thermal deformation is.

[0063] (2) Further, the higher the temperature of the monitoring area on the tubular parison is, the higher the heat exchange efficiency of the high-temperature environment in the barrel on the thermoplastic raw material is, and the higher the thermoplastic sensitivity of the monitoring area theoretically should be at this time, and the thermoplastic blow molding effect is more likely to occur.

[0064] Based on the above analysis, the temperature high presentation coefficient of each parison monitoring area is calculated, which is specifically:

[0065] The mean value of the temperature data of all positions in the parison model is calculated, denoted as the first mean value; the difference between the mean value of the temperature data of all positions in each parison monitoring area and the first mean value of the parison model thereof is calculated as the temperature high presentation coefficient of each parison monitoring area; further, the temperature high presentation coefficients of all parison monitoring areas are normalized to obtain the normalized value of the temperature high presentation coefficient of each parison monitoring area.

[0066] In the embodiments of the present application, the maximum value normalization method is used to normalize the temperature high presentation coefficient. In other embodiments of the present application, the implementer can also use other normalization methods, such as Z-Score algorithm, to normalize the temperature high presentation coefficient.

[0067] The higher the temperature level of the current parison monitoring area of the tubular parison is compared to the whole, the greater the possibility of high thermoplastic sensitivity of the monitoring area is.

[0068] Further, the thermoplastic sensitivity of each parison monitoring area is calculated, and the expression is:

[0069]

[0070] In the formula, Q is the thermoplastic sensitivity of the current parison monitoring area; G is the parison pipe diameter deformation degree of the current parison monitoring area; C is the normalized value of the temperature high presentation coefficient of the current parison monitoring area; is a normalization function, and the normalization function used in the present application is a sigmoid function. As other embodiments of the present application, the implementer can also use other normalization functions for normalization.

[0071] The parison pipe diameter deformation degree of the current monitoring area of the tubular parison The higher the curvature level of the corresponding boundary curve segment of the cross section of the current parison monitoring area of the tubular parison is, and the farther the parison monitoring area is from the corresponding central axis, the higher the possibility of the parison monitoring area to occur convex folding thermal deformation is. The higher the temperature high presentation coefficient is, the stronger the thermoplastic sensitivity of the monitoring area is, and the greater the thermoplastic sensitivity of the current monitoring area of the tubular parison is.

[0072] Step S4, based on the degree of inclination of the tangent plane at each point cloud data point on each mold wall side region, and the distance of each point cloud data point on the mold wall side region to the preset reference surface, and the thermoplastic sensitivity of the corresponding position of the mold wall side region at the same time, the wind pressure demand index of each mold wall side region is calculated.

[0073] The tubular parison generated by the barrel is inputted with wind pressure into the mold interior through the air supply port at the top of the mold after the mold is closed, so as to perform blow molding processing on the parison, and the thermoplastic sensitivity is one of the influencing factors of the wind pressure demand, but at the same time, it should be analyzed in coordination with the complex demand of the inner wall surface of the mold.

[0074] The profile complexity of different wall side regions of the mold may be different due to different design requirements. If the profile complexity of a certain mold wall side region is high, the wall surface area involved after the complete flat development of this part of the region is more, and higher wind pressure support is required during blow molding, otherwise the wall thickness of this part of the wall side region after the product is made may be relatively thick.

[0075] Therefore, based on the above analysis, the molding profile demand degree of each mold wall side region is calculated.

[0076] Specifically, for a three-dimensional point cloud mold model, the center axis of the mold model is determined by using the same acquisition method as the center axis of the parison model. Further, the geometric center of each mold wall side region of the mold model is obtained. A perpendicular line is drawn through the geometric center to the center axis of the mold model, and a plane perpendicular to the perpendicular line is drawn through the center axis as the reference surface of each mold wall side region.

[0077] The tangent plane of each point cloud data point on each mold wall side region is obtained, and the included angle data between the tangent plane and the corresponding reference surface is calculated. The standard deviation of the included angle data of all point cloud data points on each mold wall side region is calculated. The tangent plane of a point on a curved surface is obtained, and the calculation process of the included angle between two planes is known, and the specific process is not described again.

[0078] The distance from each point cloud data point on each mold wall side region to the corresponding reference surface is calculated, which is denoted as the second distance. The sum of the second distances of all point cloud data points on each mold wall side region is calculated.

[0079] Based on the above analysis, any mold wall side region is taken as the current mold wall side region. Taking the current mold wall side region as an example, the molding profile demand degree of each mold wall side region is calculated, and the expression is:

[0080]

[0081] In the formula, is the molding profile demand degree of the current mold wall side region. is the standard deviation of the included angle data of all point cloud data points on the current mold wall side area; A is the sum value of the second distance of all point cloud data points on the current mold wall side area; is a normalization function, and the sigmoid function is used for normalization in the present application.

[0082] The greater the difference between the tangent planes of each point on the wall side area, the more tortuous the wall side profile, the more wall side area involved, and the greater the wind pressure compensation for the wall side area at this time. Meanwhile, the greater the distance of each point on the wall side area to the reference surface, the farther the wall side area from the reference surface, the greater the loss in the process of wind pressure conduction to the wall side, and the greater the wind pressure compensation for the wall side area at this time.

[0083] Further, for a single wall side area on the mold, the smaller the thermoplastic sensitivity of the wall side area to the corresponding monitoring area in the parison model, the higher the wind pressure compensation required for the wall side area to achieve the same thermoplastic effect as other areas. Meanwhile, the higher the plastic profile requirement of the wall side area , the higher the wind pressure compensation requirement of the wall side area, so the wind pressure demand index of the current mold wall side area is calculated, and the expression is:

[0084]

[0085] In the formula, is the wind pressure demand index of the current mold wall side area; is the plastic profile requirement of the current mold wall side area; is the thermoplastic sensitivity of the corresponding parison monitoring area of the current mold wall side area; is a normalization function, and the sigmoid function is used for normalization in the present application. As other embodiments of the present application, implementers can also use other normalization functions for normalization.

[0086] Step S5, based on the change of the historical pressure data of each position on the inner wall surface of the mold corresponding to each mold wall side area, and combining the wind pressure demand index, the air supply offset demand degree of each mold wall side area is constructed; in each second segment of the preset fine adjustment stage, the offset trend direction and the corresponding compensation offset amplitude of each second segment are determined based on the numerical value and position distribution of all the air supply offset demand degrees at the starting time.

[0087] (1) Set a fine adjustment stage in the blowing process. In the embodiments of the present application, when the area of the parison adhering to the wall accounts for 70% of the total area of the inner wall of the mold, the fine adjustment stage is entered. Before the fine adjustment stage, the air supply port is always in the normal vertical downward blowing state, and after entering the fine adjustment stage, the air supply port is switched to the fine adjustment state. In other embodiments of the present application, the implementer can set the starting time of the fine adjustment stage according to the actual situation.

[0088] The area of the parison adhering to the wall is obtained by calculating the pressure data of all positions on the inner wall of the mold at any time, and the ratio of the number of positions with the same pressure data greater than 0 to the total number of positions is taken as the area of the parison adhering to the wall at that time.

[0089] For the initial time of the fine adjustment stage, part of the tubular parison in the mold may have adhered to the wall, part may not have adhered to the wall, and the part that has adhered to the wall also has a priority in the adhesion time. Therefore, the longer the adhesion time, the thinner the wall thickness of the region of the tubular parison compared to other regions. In order to improve the uniformity of the overall wall thickness of the product, a greater compensation air pressure needs to be applied to the region that adheres to the wall later or not at all. The pressure lag can reflect the adhesion lag, so the air supply offset demand of the wall side region in the fine adjustment stage is obtained by analyzing the pressure lag based on the air pressure demand index.

[0090] Specifically, at any time, the ratio of the number of positions with pressure data greater than 0 in each mold wall side region to the total number of positions in the mold wall side region is calculated as the area ratio factor of each mold wall side region at that time. In the historical pressure data of each position, the time when the pressure data starts to be greater than 0 is taken as the adhesion starting time of each position, and the length of time from the adhesion starting time of each position to the current time is taken as the adhesion length of each position at the current time. The average adhesion length of all positions with pressure data greater than 0 in each mold wall side region at the current time is calculated and denoted as the average adhesion length.

[0091] Further, the air supply offset demand of each mold wall side region is calculated, and the expression is:

[0092]

[0093] In the formula, is the air supply offset demand of the current mold wall side region; V is the area ratio factor of the current mold wall side region; is the average adhesion length of the current mold wall side region; is the air pressure demand index of the current mold wall side region; is a normalization function, and in this case, the sigmoid function is used for normalization. As other embodiments of the present application, the implementer can also use other normalization functions for normalization.

[0094] The shorter the wall-sticking duration of the wall-side region inside the current mold wall side region and the smaller the total area ratio of the wall-sticked region, the more lagging the wall-sticking performance of the wall-side region is. If the wind pressure demand index of the wall-side region is larger, the compensation wind pressure demand performance of the fine adjustment stage for the mold wall-side region is higher.

[0095] (2) In a single second segment in the fine adjustment stage, the mold wall-side region corresponding to the maximum value of the air supply offset demand degree of all mold wall-side regions in the mold model at the starting time is selected as the target mold wall-side region at the starting time. The direction of the air supply port pointing to the center point of the target mold wall-side region is taken as the offset trend direction of the air supply port in the second segment. In the second segment, the air supply port is offset to the offset trend direction, so that the wind pressure direction of the air supply port is closer to the wall-side with high demand degree, and the wall-side receives higher compensation wind pressure. The length of the single second segment is 1 second.

[0096] Further, the specific offset amplitude of the offset trend direction of the air supply wind pressure is analyzed. When the air supply wind pressure is offset to a certain side in the mold, all wall-side regions of the side of the mold will receive wind pressure compensation. Therefore, not only the wall-side region with the highest wind pressure demand index needs to be analyzed, but also the adjacent wall-side region needs to be considered. If the adjacent wall-side region has a relatively low wind pressure demand index, the offset amplitude can be appropriately reduced.

[0097] Therefore, the specific compensation offset amplitude of the air supply port in the offset trend direction in a single second segment in the fine adjustment stage is calculated as follows:

[0098] The a nearest mold wall-side regions adjacent to the target mold wall-side region in the mold model are taken as the adjacent mold wall-side regions of the target mold wall-side region. The average value of the air supply offset demand degrees of all adjacent mold wall-side regions of the target mold wall-side region is calculated and denoted as the second average value. The difference between the air supply offset demand degree of the target mold wall-side region and the second average value is taken as the offset demand degree adjustment amount of the target mold wall-side region.

[0099] The compensation offset amplitude of the air supply port in the offset trend direction in the mold in a single second segment in the fine adjustment stage is calculated as follows:

[0100]

[0101] In the formula, is the compensation offset amplitude in the offset trend direction of the current second segment; is the maximum value of the air supply offset demand degree at the starting time of the current second segment; is the offset demand degree adjustment amount of the target mold wall-side region at the starting time of the current second segment; is the tanh function.

[0102] The higher the offset demand degree of the wall side area of the offset trend direction, and the smaller the difference between the offset demand degree of the wall side area of the offset side and that of the wall side area, the greater the compensation offset amplitude applied to the offset trend direction of the second segment.

[0103] In step S6, the proportional gain coefficient adjustment value of each second segment is obtained based on the compensation offset amplitude, and the PID controller and the offset trend direction are combined to control the air supply direction of each second segment.

[0104] 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 taken as the proportional gain coefficient adjustment value of each second segment, and the adjustment value is 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 the rotation direction of the air supply port of each second segment, wherein the rotation direction of the air supply port is the offset trend direction of the air supply port of each second segment.

[0105] The parameters of the PID controller are dynamically updated during the continuous blow molding monitoring process to ensure the stability of the product wall thickness uniformity control during the processing process.

[0106] A step block diagram of a product wall thickness uniformity blow molding machine control method is shown in Figure 3 .

[0107] Based on the same inventive concept as the above method, the embodiment of the present application also provides a product wall thickness uniformity blow molding machine control system, which stores a computer program, and the computer program is executed by a processor to realize the steps of any one of the above product wall thickness uniformity blow molding machine control methods.

[0108] Based on the same inventive concept as the above method, the embodiment of the present application also provides a product wall thickness uniformity blow molding machine control device, which includes a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor executes the computer program to realize the steps of any one of the above product wall thickness uniformity blow molding machine control methods.

[0109] In summary, the product wall thickness uniformity blow molding machine control method provided by the embodiments of the present application analyzes the heat deformation and temperature distribution of the tubular parison formed in the extrusion process, constructs the heat plastic sensitivity of each parison monitoring area, and evaluates the heat plastic sensitivity of each monitoring area of the tubular parison; constructs the molding profile requirement degree according to the complexity of the mold, obtains the air pressure requirement index of each mold wall side area in combination with the heat plastic sensitivity, further evaluates the air requirement of each area in the parison blow molding process, and then obtains the air supply offset requirement degree in combination with the mold wall side pressure lag performance in the blow molding stage; determines the offset trend direction and the corresponding compensation offset amplitude of each second segment by analyzing the difference of the air supply offset requirement degree of all areas, obtains the proportional gain coefficient adjustment value of each second segment based on the compensation offset amplitude, controls the air supply direction of each second segment in combination with the PID controller and the offset trend direction; can adjust the air supply port according to the blow molding requirement of each area in the blow molding fine tuning stage, avoids the problem that the air supply port always adopts the vertical downward blow molding mode for the tubular parison in the traditional blow molding process, resulting in poor blow molding effect, and through a certain offset compensation of the air supply offset amplitude in the fine tuning stage, optimizes the product wall thickness uniformity, and improves the control efficiency of the blow molding machine.

[0110] It should be noted that the above-mentioned sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. And the above describes the specific embodiments of the present application. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0111] Each of the embodiments in the present application is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other. Each embodiment focuses on the difference from other embodiments.

[0112] The above only describes the preferred embodiments of the present application, and does not limit the present application. Any modification, equivalent replacement, improvement, etc. made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A blow molding machine control method for producing products with uniform wall thickness, characterized in that, The method includes the following steps: Collect point cloud data of the tubular preform and the inner wall of the mold at various times, as well as temperature data of the tubular preform at various locations and pressure data of the inner wall of the mold at various locations; At any given moment, construct a 3D point cloud billet model and a 3D point cloud mold model; divide the billet model and mold model into regions in the same way to obtain the monitoring areas of each billet and the side wall areas of each mold; obtain the central axis of the billet model. Based on the distance from the monitoring area of ​​each preform to the corresponding central axis, and the curvature of the upper and lower sections of the monitoring area of ​​each preform, combined with the temperature difference between the monitoring area of ​​each preform and the monitoring areas of other preforms at the same time, the thermoplastic sensitivity of the monitoring area of ​​each preform is calculated. Based on the degree of inclination of the tangent plane at each point cloud data point on each mold wall side area, and the distance of each point cloud data point to the preset reference surface, combined with the thermoplastic sensitivity of the preform monitoring area at the corresponding position at the same moment in each mold wall side area, the wind pressure demand index of each mold wall side area is calculated. Based on the changes in historical pressure data at various locations on the inner wall of the mold corresponding to each mold side area, and in conjunction with the air pressure demand index, the air supply offset demand degree for each mold side area is constructed; within each second segment of the preset fine-tuning stage, the offset trend direction and corresponding compensation offset amplitude for each second segment are determined based on the values ​​and location distribution of all the air supply offset demand degrees at the start time. Based on the compensation offset amplitude, the proportional gain coefficient adjustment value for each second segment is obtained, and combined with the PID controller and the offset trend direction, the air supply direction control for each second segment is performed. The process for obtaining the thermoplastic sensitivity of each preform monitoring area is as follows: The average distance from all point cloud data points in the current billet monitoring area to the corresponding central axis is calculated as the distance from the current billet monitoring area to the corresponding central axis, denoted as . The maximum distance from all monitored areas of the blank model to the corresponding central axis is denoted as . Calculate the mean curvature of all point cloud data points on the top and bottom pipe diameter cross-sectional curve segments corresponding to the current billet monitoring area, and use this as the curvature factor of the cross-sectional curve segment in the current billet monitoring area. Let G be the deformation degree of the billet tube diameter in the current billet monitoring area. The expression for G is: ; Calculate the mean of temperature data at all locations in the billet model, and denote it as the first mean; calculate the normalized value of the difference between the mean of temperature data at all locations in the current billet monitoring area and the mean of temperature data at all locations in the billet model, and denote it as C; The thermoplastic sensitivity of the current preform monitoring area is calculated and denoted as Q. The expression for Q is: In the formula, This is the normalization function; The process for obtaining the wind pressure demand index for each mold wall side area is as follows: Obtain the angle data between the tangent plane and the preset reference plane at each point cloud data point on each mold wall side region; calculate the standard deviation of the angle data of all point cloud data points on each mold wall side region; calculate the sum of the distances of all point cloud data points on each mold wall side region to the preset reference plane; and use the normalized value of the product of the standard deviation and the sum as the plastic profile requirement of each mold wall side region. The ratio of the required plastic profile to the thermoplastic sensitivity of the preform monitoring area at the corresponding position at the same moment in each mold wall area is normalized to obtain the wind pressure requirement index of each mold wall area. The process for obtaining the air supply offset requirement of each mold wall side area is as follows: In the current mold wall region, the ratio of the number of locations with calculated pressure data greater than 0 to the total number of locations is used as the area proportion factor for the current mold wall region. The duration for which pressure data at each location is greater than 0 is taken as the wall adhesion duration at each location. The average wall adhesion duration is calculated for all locations in the current mold wall region where pressure data is greater than 0, and recorded as the average wall adhesion duration. The current air pressure requirement in the mold wall area is marked as... ; Calculate the current air supply offset requirement in the mold wall area. , The expression is: In the formula, This is the normalization function; The process for obtaining the offset trend direction and corresponding compensation offset magnitude for each second segment is as follows: The maximum air supply offset requirement in the mold model at the start of the current second segment is denoted as... ,Will The corresponding mold wall area is taken as the target mold wall area, and the direction of the air outlet pointing to the center point of the target mold wall area is taken as the offset direction of each second segment. Calculate the average air supply offset demand of all adjacent mold wall regions in the target mold wall region of the mold model; calculate the difference between the air supply offset demand of the target mold wall region and the average value, and use it as the adjustment amount of the offset demand of the target mold wall region. ; Calculate the compensation offset magnitude in the offset trend direction of the current second segment. , The expression is: In the formula, This refers to the tanh function.

2. The blow molding machine control method for achieving uniform product wall thickness as described in claim 1, characterized in that, The process of obtaining the central axis of the blank model is as follows: The central axis of the billet model is obtained by extending the geometric center of the billet model along the point cloud height coordinate direction.

3. The blow molding machine control method for achieving uniform product wall thickness as described in claim 1, characterized in that, The adjustment value of the proportional gain coefficient for each second segment is the product of the compensation offset amplitude of each second segment and the preset initial proportional gain coefficient.

4. The blow molding machine control method for achieving uniform product wall thickness as described in claim 1, characterized in that, The air supply direction control, which combines the PID controller and the offset tendency direction, is specifically as follows: Within each second segment, the adjustment value is used as the new proportional gain coefficient of the PID controller, and the air outlet is rotated in the corresponding offset direction. The rotation angle of the air outlet is controlled by the control signal output by the PID controller.

5. A blow molding machine control system for products with uniform wall thickness, wherein the system stores a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the blow molding machine control method for uniform product wall thickness as described in any one of claims 1-4.

6. A blow molding machine control device for producing products with uniform 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, it implements the steps of the blow molding machine control method for uniform product wall thickness as described in any one of claims 1-4.

Images