A method and system for controlling the injection molding of a junction box plastic housing

Abstract

This application relates to the field of injection molding control technology, specifically to a method and system for controlling the injection molding of a junction box plastic housing. The method includes: acquiring the injection speed of the injection molding machine and the temperatures at the front, middle, and rear positions of the barrel during the injection molding process of the junction box plastic housing; acquiring the temperature flow deviation of the barrel at various times and the melt flow fluctuation of the barrel; combining this with the average level of the preset initial temperature values ​​at all positions of the barrel to obtain the temperature interference adjustment coefficient of the injection molding machine's injection rate; and then acquiring the target injection rate of the injection molding machine at the current time to adjust the injection rate of the injection molding machine during the injection molding process of the junction box plastic housing. This application improves the production quality stability of the junction box plastic housing.

Description

Technical Field

[0001] This application relates to the field of injection molding control technology, specifically to an injection molding control method and system for a junction box plastic housing. Background Technology

[0002] The junction box for electricity metering is an indispensable component in electricity metering devices. During the production process, it is necessary to precisely control the temperature, pressure and speed of the injection molding machine to ensure that the polycarbonate material flows evenly and fully fills the mold during the injection molding process, thereby ensuring the dimensional accuracy and structural integrity of the junction box.

[0003] The injection rate of an injection molding machine determines the product quality of the junction box plastic casing. Currently, most methods adjust the injection rate using a PID controller with preset values. However, plastic granules are geometrically structured objects, and their spacing inside the barrel is uneven, resulting in uneven temperature of the molten plastic within the barrel. Traditional methods fail to fully consider the impact of the same injection rate on injection molding at different temperatures, making it difficult to precisely control the injection rate during production. This leads to unstable product quality and problems such as underfilling, surface defects, and dimensional inaccuracies. Summary of the Invention

[0004] To address the aforementioned technical problems, the purpose of this application is to provide a method and system for controlling the injection molding of a junction box plastic housing. The specific technical solution adopted is as follows:

[0005] This application provides a method for controlling the injection molding of a junction box plastic housing, including the following steps:

[0006] To obtain the injection speed of the injection molding machine and the temperature at the front, middle and rear positions of the barrel during the injection molding process of the junction box plastic body;

[0007] Analyze the temperature deviation at different locations in the barrel at various times, as well as the temperature differences between different locations in the barrel, to obtain the temperature flow deviation of the barrel at various times.

[0008] Based on the degree of synchronous correlation between the temperature flow deviation of the barrel at each moment and the temperature change trend at each moment, and combined with the degree of temperature change fluctuation at each moment, the melt flow fluctuation of the barrel is obtained.

[0009] Based on the melt flow fluctuation of the barrel and the temperature deviation at various locations in the barrel, combined with the average level of the preset initial temperature values ​​at all locations in the barrel, the temperature interference adjustment coefficient of the injection rate of the injection molding machine is obtained.

[0010] By using the temperature interference adjustment coefficient of the injection rate of the injection molding machine, the target injection rate of the injection molding machine at the current moment is obtained, so as to adjust the injection rate of the injection molding machine during the injection molding process of the junction box plastic body.

[0011] Preferably, the method for obtaining the temperature flow deviation of the barrel at various times is as follows:

[0012] ;

[0013] Where, This represents the temperature and flow deviation of the barrel at time i. This represents the average distance between each temperature in the temperature flow vector at time i and the fitted straight line. This represents the temperature difference between the front and middle parts of the barrel at time i. This represents the temperature difference between the middle and rear parts of the barrel at time i.

[0014] Preferably, the temperatures at the front, middle, and rear of the barrel at each moment are arranged in the order of rear, middle, and front of the barrel position to obtain the temperature flow vector at each moment. The temperature flow vector is then fitted with a straight line to obtain the fitting straight line of the barrel at each moment.

[0015] Preferably, the method for obtaining the melt flow fluctuation of the barrel is as follows:

[0016] In the formula, This indicates the ripple rate of the melt flow in the barrel. This represents the number of elements in the fitted slope sequence. This represents the j-th element in the fitted slope sequence. This represents the dispersion of all elements in the difference sequence. The slope represents the preset standard change, and || indicates the sign of the absolute value. This represents the normalization function.

[0017] Preferably, the slope of the fitted line of the temperature flow vector at each time moment and the temperature flow deviation at each time moment are arranged in time sequence to obtain the fitted slope sequence and the temperature flow deviation sequence, respectively. The two sequences are normalized, and the difference at the same position in the two normalized sequences is used to form the difference sequence.

[0018] Preferably, the method for obtaining the temperature interference adjustment coefficient of the injection rate of the injection molding machine is as follows:

[0019] In the formula, The temperature interference adjustment coefficient represents the injection rate of the injection molding machine. This indicates the ripple rate of the melt flow in the barrel. This represents the average of the preset initial temperature values ​​at all locations on the barrel. This indicates the temperature deviation value in the barrel.

[0020] Preferably, the melt temperature sequence at each position of the barrel is extracted, and the difference between the preset initial temperature value at each position of the barrel and all elements in the melt temperature sequence at the corresponding position of the barrel is calculated. The average of all calculated differences is taken as the temperature deviation value in the barrel.

[0021] Preferably, the temperatures collected at each position of the barrel are normalized, and the normalized temperature data are arranged in chronological order to obtain the melt temperature sequence at each position of the barrel.

[0022] Preferably, the method for obtaining the target injection rate of the injection molding machine at the current moment is as follows:

[0023] In the formula, This represents the target injection rate of the injection molding machine at the current moment, where v represents the current injection rate of the injection molding machine. This is the temperature interference adjustment coefficient for the injection rate of the injection molding machine.

[0024] This application embodiment also provides an injection molding control system for a junction box plastic housing, 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, it implements the steps of the injection molding control method for a junction box plastic housing described above.

[0025] As can be seen from the above, the injection molding control method and system for a junction box plastic housing provided in this application have at least the following beneficial effects:

[0026] This application solves the problems of insufficient filling, surface defects and dimensional accuracy deviation caused by temperature fluctuations in the barrel by accurately calculating the temperature interference adjustment coefficient of the injection rate and dynamically adjusting the injection rate of the injection molding machine based on this coefficient. This can improve the production quality stability of the junction box plastic box and ensure the high quality and consistency of the product.

[0027] This application achieves precise control of the injection rate, avoiding excessive or insufficient melt shear heat caused by excessively high or low injection rates, thereby reducing unnecessary energy waste. At the same time, stable injection rate and temperature control help extend the service life of the injection molding machine, reduce equipment maintenance costs, and further optimize energy utilization efficiency in the production process. Attached Figure Description

[0028] 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.

[0029] Figure 1 A flowchart illustrating the steps of an injection molding control method for a junction box plastic housing provided in this application. Detailed Implementation

[0030] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of an injection molding control method and system for a junction box plastic housing proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0031] Unless otherwise specified and limited, terms such as “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the article or device that includes said element. Furthermore, the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. 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 pertains.

[0032] The following description, in conjunction with the accompanying drawings, details the specific scheme of the injection molding control method and system for a junction box plastic body provided in this application.

[0033] Please see Figure 1 The diagram illustrates a flowchart of the injection molding control method for a junction box plastic housing according to an embodiment of this application, including the following steps:

[0034] Step 1: Obtain the injection speed of the injection molding machine and the temperature at the front, middle and rear positions of the barrel during the injection molding process of the junction box plastic body.

[0035] In this embodiment, temperature sensors are evenly installed at three positions—front, middle, and rear—within the barrel. The temperature at the front, middle, and rear of the barrel is collected, and the injection speed of the injection molding machine is collected using a flow rate sensor. The data acquisition time is 1 minute, and the data acquisition frequency is 10 Hz.

[0036] To avoid the influence of environmental noise on the collected data, in this embodiment, the temperature data collected at each position of the barrel and the injection rate of the injection molding machine are normalized. After denoising the data using mean filtering, the normalized and denoised data are arranged in chronological order of collection time, denoised as the melt temperature sequence at the front of the barrel, the melt temperature sequence at the middle of the barrel, the melt temperature sequence at the rear of the barrel, and the injection speed sequence. The mean filtering and normalization processes are well-known techniques, and the specific calculation steps are not detailed here. This embodiment uses exponential normalization. It should be noted that the preset temperature ranges for the front, middle, and rear of the barrel are 250°C - 310°C, 240°C - 280°C, and 230°C - 250°C, respectively. In this embodiment, the preset initial temperatures at the front, middle, and rear positions of the barrel are 280°C, 260°C, and 240°C, respectively.

[0037] Step 2: Analyze the temperature deviation at different positions of the barrel at each time point, as well as the temperature difference between different positions of the barrel, to obtain the temperature flow deviation of the barrel at each time point.

[0038] For the production of plastic junction box bodies, firstly, dried plastic granules are added to a hopper. The plastic is heated and melted in a barrel. Then, a rotating screw stirs the molten material to ensure uniform plasticization. The screw then retracts, pushing the melt into the mold cavity for rapid filling. Therefore, the barrel temperature should typically increase gradually from the rear to the front to ensure the plastic maintains good flowability as it enters the nozzle. Consequently, the temperature within the barrel is not uniformly distributed; rather, it is higher closer to the nozzle.

[0039] Temperature data at different locations within the barrel at the same time are extracted. The temperatures at the front, middle, and back of the barrel at each moment are arranged in the order of back, middle, and front to obtain the temperature flow vector at each moment, which is used to characterize the temperature change in the barrel at each moment. For the temperature at different locations in the barrel at the same time, it should gradually increase from back to front. At the same time, the more similar the temperature increase at different moments, the higher the stability of the melt flow inside the injection molding machine barrel.

[0040] Therefore, the temperature flow vector in the barrel at each moment is used as input for linear least squares fitting to obtain the fitted line and its slope at each moment. The distance between each element of the temperature flow vector and the corresponding fitted line is also obtained to characterize the temperature flow state in the barrel at each moment. The calculation of linear least squares is a well-known technique, and the specific calculation process will not be elaborated here. Thus, the temperature flow deviation in the barrel at each moment is calculated:

[0041] ;

[0042] In the formula, This represents the temperature and flow deviation of the barrel at time i. This represents the average distance between each temperature in the temperature flow vector at time i and the fitted straight line. This represents the temperature difference between the front and middle parts of the barrel at time i, which is the difference between the third and second elements in the temperature flow vector. This represents the temperature difference between the middle and rear parts of the barrel at time i, which is the difference between the second element and the first element in the temperature flow vector.

[0043] The greater the temperature difference between the front, middle, and rear parts of the barrel, the more unbalanced the temperature distribution of the molten plastic inside the barrel, and the greater the fluctuation between its temperature data. This results in a greater deviation between the temperature in the temperature flow vector and the fitted curve at that moment. At the same time, the temperature difference between different positions also increases, resulting in a greater temperature flow deviation at that moment. This indicates a greater difference in the temperature change of the material in the barrel, requiring adjustment of the injection rate of the injection molding machine to improve the production quality of the junction box plastic body.

[0044] Step 3: Based on the degree of synchronous correlation between the temperature flow deviation of the barrel at each moment and the temperature change trend at each moment, and combined with the degree of temperature change fluctuation at each moment, obtain the melt flow fluctuation of the barrel.

[0045] Furthermore, in this embodiment, the calculated temperature flow deviations are arranged in chronological order according to their corresponding moments to obtain a temperature flow deviation sequence. The slopes of the fitted lines of the temperature flow vectors at different moments are then arranged in chronological order to obtain a fitted slope sequence.

[0046] When the temperature inside the barrel increases uniformly from back to front, it indicates that the injection molding machine melts the material relatively evenly, allowing the plastic granules to flow effectively. This maintains a state where the flowability of the molten plastic is weaker at the rear of the barrel and stronger at the front, contributing to a stable melt flow during injection. In this case, the differences in temperature flow deviations at different times are small, and the temperature differences at different locations at different times are also small. This means that the slopes of the fitted lines for the temperature flow vectors at different times differ little. Furthermore, the more synchronized the slopes of the fitted lines are with the temperature flow deviations at different times, the more balanced the internal state of the barrel is.

[0047] To eliminate the influence of dimensions, a normalization function is used to normalize the temperature flow deviation sequence and the fitted slope sequence respectively. In this embodiment, maximum-minimum value normalization is used. Furthermore, the difference sequence between the two normalized sequences is calculated to characterize the synchronicity between the two sequences. The smaller the difference between the elements in the difference sequence, the higher the stability of the melt inside the barrel. The calculation of maximum-minimum value normalization and the difference sequence are both well-known techniques, and the specific calculation steps will not be elaborated here. Therefore, the melt flow fluctuation in the barrel is calculated as follows:

[0048] ;

[0049] Where, This indicates the ripple rate of the melt flow in the barrel. This represents the number of elements in the fitted slope sequence. This represents the j-th element in the fitted slope sequence. This represents the dispersion of all elements in the difference sequence. Dispersion includes variance, standard deviation, coefficient of variation, and coefficient of variation. In this embodiment, variance is used as the formula for calculating dispersion. This represents the preset standard slope. Ideally, the temperature difference between the first and middle sections should be the same as the temperature difference between the middle and last sections. Therefore, in this example, the standard slope 'a' is set to 1. || indicates the absolute value sign. The normalization function is represented by the exponential normalization function used in this embodiment. The specific calculation of the exponential normalization function is a well-known technique and will not be described in detail in this embodiment.

[0050] When there are significant temperature variations at different locations within the injection molding machine barrel, the slope of the fitted linear trend of melt temperature at different locations at the same time will deviate from the standard slope. This reduces the synchronicity between the temperature flow deviation and the data slope at different times, leading to increased dispersion of elements in the difference sequence between the normalized temperature flow deviation sequence and the fitted slope sequence. This results in larger values ​​for the melt flow fluctuation in the barrel, indicating poorer melt flow stability. Therefore, it is necessary to reduce the injection speed of the injection molding machine to decrease the shear heat of the plastic melt within the barrel, ensuring a smooth and flawless surface of the injection-molded junction box and guaranteeing product quality.

[0051] Step 4: Based on the melt flow fluctuation of the barrel and the temperature deviation at various locations in the barrel, and combined with the average level of the preset initial temperature values ​​at all locations in the barrel, obtain the temperature interference adjustment coefficient for the injection rate of the injection molding machine.

[0052] Regarding the temperature of the molten plastic in the barrel, the greater the temperature exceeds the preset value, the stronger the fluidity of the molten plastic, leading to uneven cooling rates within the mold cavity and resulting in unstable product dimensional accuracy. Reducing the injection speed can decrease the shear heat of the melt within the barrel, ensuring that the temperature of the molten plastic injected into the mold remains stable. Therefore, based on the melt flow fluctuation in the barrel and the degree of temperature deviation at various locations within the barrel, combined with the average level of the preset initial temperature values ​​at all locations within the barrel, the temperature interference adjustment coefficient for the injection rate of the injection molding machine is calculated.

[0053] ;

[0054] In the formula, The temperature interference adjustment coefficient represents the injection rate of the injection molding machine. This indicates the ripple rate of the melt flow in the barrel. This represents the average of the preset initial temperature values ​​at all locations on the barrel. The temperature deviation value in the barrel is represented by the following: In this embodiment, the difference between the preset initial temperature value at each position of the barrel and all elements in the melt temperature sequence at the corresponding position of the barrel is calculated, and the average of all calculated differences is taken as the temperature deviation value in the barrel, which is used to characterize the direction and magnitude of the temperature deviation at each position of the barrel.

[0055] The more unstable the plastic melt in the barrel is, the greater the difference between the current position and the preset temperature, resulting in a larger value of the melt flow fluctuation in the barrel. In addition, the larger the temperature deviation between the current temperature and the preset temperature, the larger the absolute value of the temperature interference adjustment coefficient of the injection rate of the injection molding machine. This results in a larger adjustment ratio of the injection rate of the injection molding machine, in order to reduce the impact of temperature fluctuation on product quality, thereby ensuring the stability of the injection molding process and the high quality of the product.

[0056] Step 5: Obtain the target injection rate of the injection molding machine at the current moment by using the temperature interference adjustment coefficient of the injection rate, so as to adjust the injection rate of the injection molding machine during the injection molding process of the junction box plastic body.

[0057] For the temperature interference adjustment coefficient of the injection rate of the injection molding machine calculated in the above steps, when it is greater than or equal to 0, it indicates that the temperature inside the injection molding machine barrel is lower than the preset target. Therefore, it is necessary to increase the injection rate to increase the shear heat of the plastic melt in the barrel, raise the temperature of the plastic melt in the barrel, increase the viscosity of the melt, and reduce incomplete filling or surface defects caused by excessive cooling. Conversely, the opposite is also true. Therefore, in this embodiment, the target injection rate of the injection molding machine at the current moment is calculated using the temperature interference adjustment coefficient.

[0058] In the formula, This represents the target injection rate of the injection molding machine at the current moment, where v represents the current injection rate of the injection molding machine. This is the temperature interference adjustment coefficient for the injection rate of the injection molding machine.

[0059] Furthermore, in this embodiment, the calculated target injection rate of the injection molding machine at the current moment is input into the PID controller as the injection rate during the injection molding process of the junction box plastic body. The PID controller obtains its output signal based on the error between the current injection rate and the target injection rate, and adjusts the current injection rate of the injection molding machine through the output signal. This allows the injection machine to dynamically adjust the injection rate, reduce product defects, optimize the filling effect, and thus improve production efficiency and product quality. It should be noted that the specific process of the PID controller adjusting according to the error is well-known to those skilled in the art, and this embodiment does not impose any special limitations on it, nor will it be described in detail.

[0060] Based on the same inventive concept as the above method, this application embodiment also provides an injection molding control system for a junction box plastic housing, 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, it implements the steps of any of the above-described injection molding control methods for a junction box plastic housing.

[0061] It is understood that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0062] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0063] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Any equivalent structural or procedural transformations made based on the description and drawings of this application, or direct or indirect applications in other related technical fields, are similarly included within the protection scope of this application.

Claims

1. A method for controlling the injection molding of a junction box plastic housing, characterized in that, Includes the following steps: To obtain the injection speed of the injection molding machine and the temperature at the front, middle and rear positions of the barrel during the injection molding process of the junction box plastic body; Analyze the temperature deviation at different locations in the barrel at various times, as well as the temperature differences between different locations in the barrel, to obtain the temperature flow deviation of the barrel at various times. Based on the degree of synchronous correlation between the temperature flow deviation of the barrel at each moment and the temperature change trend at each moment, and combined with the degree of temperature change fluctuation at each moment, the melt flow fluctuation of the barrel is obtained. Based on the melt flow fluctuation of the barrel and the temperature deviation at various locations in the barrel, combined with the average level of the preset initial temperature values ​​at all locations in the barrel, the temperature interference adjustment coefficient of the injection rate of the injection molding machine is obtained. By using the temperature interference adjustment coefficient of the injection rate of the injection molding machine, the target injection rate of the injection molding machine at the current moment is obtained, so as to adjust the injection rate of the injection molding machine during the injection molding process of the junction box plastic body.

2. The injection molding control method for a junction box plastic housing as described in claim 1, characterized in that, The method for obtaining the temperature flow deviation of the barrel at various times is as follows: ； In the formula, This represents the temperature and flow deviation of the barrel at time i. This represents the average distance between each temperature in the temperature flow vector at time i and the fitted straight line. This represents the temperature difference between the front and middle parts of the barrel at time i. This represents the temperature difference between the middle and rear parts of the barrel at time i.

3. The injection molding control method for a junction box plastic housing as described in claim 2, characterized in that, The temperatures at the front, middle, and rear of the barrel at each time point are arranged in the order of rear, middle, and front of the barrel position to obtain the temperature flow vector at each time point. The temperature flow vector is then fitted with a straight line to obtain the fitted straight line of the barrel at each time point.

4. The injection molding control method for a junction box plastic housing as described in claim 3, characterized in that, The method for obtaining the melt flow fluctuation of the barrel is as follows: In the formula, This indicates the ripple rate of the melt flow in the barrel. This represents the number of elements in the fitted slope sequence. This represents the j-th element in the fitted slope sequence. This represents the dispersion of all elements in the difference sequence. The slope represents the preset standard change, and || indicates the sign of the absolute value. This represents the normalization function.

5. The injection molding control method for a junction box plastic housing as described in claim 4, characterized in that, The slope of the fitted line of the temperature flow vector at each time point and the temperature flow deviation at each time point are arranged in time sequence to obtain the fitted slope sequence and the temperature flow deviation sequence, respectively. The two sequences are normalized, and the difference at the same position in the two normalized sequences is used to form the difference sequence.

6. The injection molding control method for a junction box plastic housing as described in claim 1, characterized in that, The method for obtaining the temperature interference adjustment coefficient of the injection rate of the injection molding machine is as follows: In the formula, The temperature interference adjustment coefficient represents the injection rate of the injection molding machine. This indicates the ripple rate of the melt flow in the barrel. This represents the average of the preset initial temperature values ​​at all locations on the barrel. This indicates the temperature deviation value in the barrel.

7. The injection molding control method for a junction box plastic housing as described in claim 6, characterized in that, Extract the melt temperature sequence at each position of the barrel, calculate the difference between the preset initial temperature value at each position of the barrel and all elements in the melt temperature sequence at the corresponding position of the barrel, and take the average of all calculated differences as the temperature deviation value in the barrel.

8. The injection molding control method for a junction box plastic housing as described in claim 7, characterized in that, The temperatures collected at each location in the barrel were normalized, and the normalized temperature data were arranged in chronological order to obtain the melt temperature sequence at each location in the barrel.

9. The injection molding control method for a junction box plastic housing as described in claim 1, characterized in that, The method for obtaining the target injection rate of the injection molding machine at the current moment is as follows: In the formula, This represents the target injection rate of the injection molding machine at the current moment, where v represents the current injection rate of the injection molding machine. This is the temperature interference adjustment coefficient for the injection rate of the injection molding machine.

10. A control system for injection molding a junction box plastic housing, 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 injection molding control method for a junction box plastic housing as described in any one of claims 1-9.

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