Cooling adjusting method, device and system applied to plastic injection mold

Abstract

The invention relates to the technical field of plastic injection mold cooling, in particular to a cooling adjusting method, device and system applied to a plastic injection mold. The method comprises the steps that infrared thermal images of a cooling loop of the plastic injection mold at all collection moments are obtained, the difference of the cooling water temperature between the inlet end and the outlet end of the cooling loop at all the collection moments and the cooling water flow speed of the inlet end are obtained; obtaining a first flow velocity influence value and a second flow velocity influence value at each acquisition moment; comprehensively analyzing the upper limit and the lower limit of the flow velocity of the cooling water when the plastic injection mold is cooled, the first flow velocity influence value and the second flow velocity influence value, and determining the flow velocity adjustment value of the cooling water at each collection moment; and adjusting the flow velocity of the cooling water at the current acquisition moment based on the flow velocity adjustment value and the flow velocity of the cooling water at the current acquisition moment. The cooling device aims at improving the cooling effect on the plastic injection mold.

Description

Technical Field

[0001] The present application relates to the technical field of cooling plastic injection molds, and in particular to a cooling and regulating method, device and system for plastic injection molds. Background Art

[0002] In the process of recycling plastic waste, plastic injection molds can reprocess recycled plastic waste into new plastic products. This reprocessing not only helps to improve the utilization rate of plastic waste and reduce the demand for new materials, but also promotes the green development of the plastics industry and reduces environmental pollution.

[0003] During the processing of plastic injection molds, the cooling system of the plastic injection mold is crucial to the entire injection molding process. The flow rate of cooling water in the cooling system directly affects the cooling effect of the plastic injection mold. Too high a flow rate will cause uneven cooling of the plastic injection mold, resulting in defects such as warping and deformation of the plastic products in the plastic injection mold. Too low a flow rate will prolong the cooling time of the plastic injection mold. However, the flow rate of cooling water is usually set manually, which makes it impossible to adjust the cooling water flow rate in a timely and accurate manner according to the actual situation during the cooling process, thereby reducing the cooling effect. Summary of the invention

[0004] In view of the above, it is necessary to provide a cooling adjustment method, device and system for plastic injection molds, which improves the cooling effect of plastic injection molds compared with traditional cooling adjustment methods for plastic injection molds:

[0005] In a first aspect, an embodiment of the present application provides a cooling adjustment method for a plastic injection mold, the method comprising the following steps:

[0006] Obtaining infrared thermal images of a cooling circuit of a plastic injection mold at each acquisition time, obtaining a difference in cooling water temperature between an inlet end and an outlet end of the cooling circuit at each acquisition time, recorded as a temperature difference, and a cooling water flow rate at the inlet end;

[0007] Based on the distribution of the temperature values ​​of the pixel points in each infrared thermal image, the mold pixel points in each infrared thermal image are obtained;

[0008] Analyze the change trend of the temperature value of the mold pixel point in the infrared thermal image at all acquisition moments, the change trend of the temperature difference, and the difference of the temperature value of the mold pixel point between each acquisition moment and its adjacent acquisition moment, and the difference of the temperature difference, to determine the degree of temperature drop and temperature rise at each acquisition moment;

[0009] Based on the temperature drop degree and the temperature rise degree, obtaining a first flow velocity impact value at each collection time;

[0010] Extracting each connected domain of the mold pixel points in each infrared thermal image, and determining the mold temperature uniformity at each acquisition time based on the fluctuation degree and distribution range of the temperature values ​​of all pixel points in all the connected domains in each infrared thermal image;

[0011] Determine the second flow rate impact value at each sampling moment by combining the trend change degree of the mold temperature uniformity at all sampling moments and the mold temperature uniformity;

[0012] Comprehensively analyzing the upper limit and lower limit of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value, to determine the flow rate adjustment value of the cooling water at each collection time;

[0013] The flow rate of the cooling water at the current collection time is adjusted based on the flow rate adjustment value.

[0014] In one embodiment, the process of acquiring the pixel points of the mold is as follows:

[0015] Obtain the segmentation threshold of the temperature values ​​of all pixels in each infrared thermal image;

[0016] The pixels in each infrared thermal image whose temperature value is greater than the segmentation threshold are regarded as mold pixels.

[0017] In one embodiment, the process of determining the temperature drop degree and the temperature rise degree is as follows:

[0018] The average of the temperature values ​​of all the mold pixel points in the infrared thermal image at each acquisition time is used as the mold surface temperature at each acquisition time; and the first-order difference sequence of the mold surface temperature at all acquisition times is obtained;

[0019] Get the absolute value of the slope of the fitted line for all data points in the first-order difference sequence;

[0020] The difference in mold surface temperature between each sampling moment and its adjacent previous sampling moment is recorded as the surface temperature difference;

[0021] The normalized value of the product of the absolute value and the surface temperature difference is used as the temperature drop degree at each acquisition time;

[0022] The absolute value of the difference in cooling water temperature between the inlet and outlet at each sampling moment is recorded as the cooling water temperature difference;

[0023] The same calculation method as the temperature drop degree at each sampling moment is adopted, and the mold surface temperature is replaced by the cooling water temperature difference to calculate the temperature rise degree at each sampling moment.

[0024] In one embodiment, the expression of the first flow velocity influence value is:

[0025] Where S1(n) represents the first flow velocity impact value at the nth acquisition moment; They respectively represent the degree of temperature drop and the degree of temperature rise at the nth acquisition moment; norm() represents the normalization function; α represents a preset value greater than 0.

[0026] In one embodiment, the process of determining the mold temperature uniformity is:

[0027] Based on the discrete degree and range of the temperature values ​​of all pixels in each connected domain, the temperature uniformity of each connected domain is determined;

[0028] Calculate the average temperature uniformity of all connected domains corresponding to each acquisition moment;

[0029] Calculate the temperature range of all mold pixel points in the infrared thermal image at each acquisition time, and record it as the temperature range;

[0030] The mold temperature uniformity is positively correlated with the average value, and negatively correlated with the temperature extreme difference.

[0031] In one embodiment, the process of determining the second flow velocity influence value is as follows:

[0032] Each acquisition time and its mold temperature uniformity are respectively composed into two-dimensional data points, which are recorded as two-dimensional temperature data points;

[0033] The expression of the second flow velocity influence value at each acquisition time is:

[0034] S2(n) represents the second flow velocity impact value at the nth acquisition moment; k represents the slope of the fitting line of all two-dimensional temperature data points; U n It indicates the mold temperature uniformity at the nth acquisition moment; ε indicates a preset value greater than 0; norm() indicates a normalization function; exp() indicates an exponential function with a natural constant as the base.

[0035] In one embodiment, the expression of the flow rate adjustment value is:

[0036] Wherein, V(n) represents the flow rate adjustment value of cooling water at the nth collection moment; v1 and v2 represent the maximum and minimum flow rates of cooling water when cooling the plastic injection mold, respectively; S1(n) and S2(n) represent the first flow rate influence value and the second flow rate influence value at the nth collection moment, respectively; σ represents a preset value greater than 0; norm() represents the normalization function.

[0037] In one embodiment, the method for adjusting the flow rate of cooling water at the current collection time based on the flow rate adjustment value is:

[0038] The flow rate adjustment value and flow rate of the cooling water at the current collection moment are input into the PID controller, and a control signal of the cooling water flow rate is output to adjust the flow rate of the cooling water to the flow rate adjustment value.

[0039] In a second aspect, an embodiment of the present application further provides a cooling and regulating device for a plastic injection mold, the device comprising:

[0040] A cooling process related information acquisition module is used to acquire an infrared thermal image of a cooling circuit of a plastic injection mold at each acquisition time, and to acquire the difference in cooling water temperature between an inlet end and an outlet end of the cooling circuit at each acquisition time, recorded as a temperature difference, and a cooling water flow rate at the inlet end;

[0041] The cooling process related information analysis module is used to obtain the mold pixel points in each infrared thermal image based on the distribution of the temperature values ​​of the pixel points in each infrared thermal image;

[0042] Calculate the average level of the temperature values ​​of all the mold pixel points in each infrared thermal image, and determine the degree of temperature drop and temperature rise at each acquisition moment based on the average level at all acquisition moments, the degree of trend change of the temperature difference, and the difference between the average level and the temperature difference at each acquisition moment and its adjacent acquisition moment;

[0043] Based on the temperature drop degree and the temperature rise degree, obtaining a first flow velocity impact value at each collection time;

[0044] Extracting each connected domain of the mold pixel points in each infrared thermal image, and determining the mold temperature uniformity at each acquisition time based on the fluctuation degree and distribution range of the temperature values ​​of all pixel points in all the connected domains in each infrared thermal image;

[0045] Determine the second flow rate impact value at each sampling moment by combining the trend change degree of the mold temperature uniformity at all sampling moments and the mold temperature uniformity;

[0046] Comprehensively analyzing the upper limit and lower limit of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value, to determine the flow rate adjustment value of the cooling water at each collection time;

[0047] The cooling water flow rate regulating module is used to regulate the flow rate of the cooling water at the current collection time based on the flow rate adjustment value and the flow rate of the cooling water at the current collection time.

[0048] In a third aspect, an embodiment of the present application also provides a cooling and regulating system for a plastic injection mold, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned cooling and regulating methods for a plastic injection mold are implemented.

[0049] This application has at least the following beneficial effects:

[0050] The present application comprehensively analyzes the increase in cooling water temperature and the decrease in mold surface temperature, determines the first flow rate impact value, reflects the cooling efficiency of cooling water on the plastic injection mold, comprehensively considers the influence of cooling water flow rate on cooling water temperature and plastic injection mold surface temperature, and improves the accuracy of analyzing cooling water flow rate on cooling efficiency of plastic injection mold;

[0051] Furthermore, the second flow rate influence value is determined by the uniformity of the surface temperature distribution of the plastic injection mold and the change trend of the uniformity, thereby improving the accuracy of analyzing the influence of the cooling water flow rate on the distribution uniformity of the surface temperature of the plastic injection mold;

[0052] Furthermore, the flow rate adjustment value is determined in combination with the first flow rate influence value and the second flow rate influence value, and the cooling water flow rate is adjusted using a PID controller based on the flow rate adjustment value. The influence of the cooling water flow rate on the cooling efficiency of the plastic injection mold and the distribution uniformity of the mold surface temperature is fully considered, and the cooling water flow rate is adjusted more accurately, thereby improving the accuracy of controlling the temperature of the plastic injection mold and avoiding the problem in the traditional method that the cooling water flow rate cannot achieve the expected cooling effect, thereby shortening the production cycle of plastic products and improving the quality of plastic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. 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 paying any creative work.

[0054] Figure 1 A flowchart of the steps of a cooling adjustment method for a plastic injection mold provided in one embodiment of the present application;

[0055] Figure 2 The figure is a flow chart for determining the degree of temperature drop;

[0056] Figure 3 is a schematic diagram of a process for determining a first flow velocity influence value;

[0057] Figure 4 This is a schematic diagram of the process for determining the mold temperature uniformity;

[0058] Figure 5 Schematic diagram of the process for obtaining flow rate adjustment value. DETAILED DESCRIPTION

[0059] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. It should be understood that, unless otherwise specified, " / " means or.

[0061] It should also be noted that the terms "first" and "second" in the present application are used to distinguish similar objects rather than to describe a specific order or sequence.

[0062] The specific scheme of the cooling and regulating method, device and system for plastic injection molds provided by the present application is described in detail below with reference to the accompanying drawings.

[0063] See also Figure 1 , which shows a flowchart of a cooling adjustment method for a plastic injection mold provided by an embodiment of the present application, the method comprising the following steps:

[0064] Step 1, obtain infrared thermal images of the cooling circuit of the plastic injection mold at each acquisition time, obtain the difference in cooling water temperature between the inlet and outlet ends of the cooling circuit at each acquisition time, recorded as the temperature difference, and the cooling water flow rate at the inlet end.

[0065] The recycled plastic waste is sorted to ensure that plastics of the same type are concentrated for pre-processing, which includes cleaning, drying, and crushing into particles so that the plastic waste can be processed by the injection molding machine.

[0066] The pretreated plastic particles are added into the injection molding machine from the feed funnel, heated to melt the plastic particles, and injected into the plastic injection mold through the nozzle of the injection molding machine. When the plastic injection mold is filled, the cooling system of the plastic injection mold is turned on. At this time, an infrared thermal imaging camera is used to capture images facing the cooling circuit of the plastic injection mold.

[0067] In this embodiment, the image acquisition duration and time interval are 10 seconds and 1 second respectively. The values ​​of the acquisition duration and time interval are preset manually and can be set by the implementer. This application does not impose any special restrictions.

[0068] Each infrared thermal image collected is subjected to denoising processing to reduce the influence of noise in the image on the subsequent processing process, and each infrared thermal image after denoising is subjected to grayscale processing. The grayscale value of each pixel in the infrared thermal image is recorded as the temperature value of each pixel, wherein the grayscale processing is a well-known technology and will not be described in detail in this application.

[0069] In this embodiment, a Gaussian filtering method is used to denoise the infrared thermal image. As other implementation methods, on the basis of being able to denoise the infrared thermal image, the implementer may use other existing technologies to denoise the infrared thermal image, such as a median filtering method, a mean filtering method, etc., and this application does not impose any special restrictions.

[0070] At each collection moment, the temperature sensor is used to collect the cooling water temperature at the inlet and outlet ends of the cooling circuit of the plastic injection mold, and the flow rate sensor is used to collect the cooling water flow rate at the inlet end of the cooling circuit of the plastic injection mold.

[0071] Step 2, comprehensively analyzing the increase in cooling water temperature and the decrease in mold surface temperature to determine the first flow rate impact value.

[0072] When cooling the plastic injection mold, the main function of the cooling water in the cooling circuit is to quickly take away the heat of the plastic melt absorbed by the plastic injection mold. The slower the cooling water flow rate, the lower the efficiency of taking away heat, causing the mold surface temperature to drop slower, thereby extending the cooling time of the plastic injection mold; the smaller the difference in cooling water temperature between the inlet and outlet ends of the cooling circuit, the lower the cooling efficiency of the cooling water on the plastic injection mold, and the cooling water flow rate should be increased to facilitate rapid cooling of the plastic injection mold, thereby increasing the molding speed of plastic waste products in the plastic injection mold.

[0073] Step 2.1, based on the distribution of the temperature values ​​of the pixel points in each infrared thermal image, obtain the mold pixel points in each infrared thermal image.

[0074] Based on the above analysis, taking the infrared thermal image An at the nth acquisition moment as an example, since the cooling water pipe in the cooling circuit of the plastic injection mold will cover a part of the surface of the plastic injection mold, and the surface of the plastic injection mold has a higher temperature than the cooling water in the cooling circuit, the threshold segmentation algorithm is used to obtain the segmentation threshold of the temperature value of all pixels in the infrared thermal image An, and the pixels in the infrared thermal image An with temperature values ​​greater than the segmentation threshold are taken as mold pixels, and all mold pixels in the infrared thermal image An are combined into a mold pixel set Jn, which is used to characterize the set composed of all pixels in the infrared thermal image An belonging to the plastic injection mold area.

[0075] In this embodiment, the Otsu threshold algorithm is used to obtain the segmentation threshold. As other implementation methods, on the basis of being able to obtain the segmentation threshold, the implementer may adopt other existing technologies to obtain the segmentation threshold, such as a global threshold segmentation algorithm, an iterative threshold segmentation algorithm, etc., and this application does not impose any special restrictions.

[0076] Step 2.2, respectively analyze the change trend of the temperature value of the mold pixel point in the infrared thermal image at all acquisition moments, the change trend of the temperature difference, and the difference in the temperature value of the mold pixel point between each acquisition moment and its adjacent acquisition moment, and the difference in the temperature difference, to determine the degree of temperature drop and temperature rise at each acquisition moment.

[0077] The average temperature value of all pixels in the mold pixel set Jn is taken as the mold surface temperature at the nth acquisition moment; the absolute value of the difference in cooling water temperature between the inlet and outlet ends at the nth acquisition moment is recorded as the cooling water temperature difference at the nth acquisition moment.

[0078] The mold surface temperatures at all acquisition moments are arranged in time series to form a mold surface temperature sequence, and a first-order difference sequence of the mold surface temperature sequence is obtained to characterize the change in the surface temperature change rate of the plastic injection mold at each acquisition moment over time. The acquisition of the first-order difference sequence is a well-known technology and will not be repeated in this application.

[0079] The serial number of the data in the first-order difference sequence is used as the horizontal coordinate, and the data is used as the vertical coordinate. The data in the first-order difference sequence and its serial number are composed into two-dimensional data points, which are recorded as two-dimensional difference data points. A straight line is fitted to all the two-dimensional difference data points to obtain the absolute value of the slope of the fitting line. Since the surface temperature of the plastic injection mold usually does not rise during the cooling process, the absolute value of the slope of the fitting line can be used to characterize the changing trend of the instantaneous decrease rate of the mold surface temperature over time during all image acquisition periods.

[0080] In this embodiment, the least squares straight line fitting method is used to obtain the fitting straight line. As other implementation methods, based on the fitting straight line of the data points that can be obtained, the implementer can use other existing technologies to obtain the fitting straight line, such as linear regression analysis, weighted least squares method, etc., and this application does not make any special restrictions.

[0081] Based on the difference in mold surface temperature between each acquisition moment and its adjacent acquisition moment, and the slope of the fitted straight line of the two-dimensional differential data points, the temperature drop degree at each acquisition moment is determined, which is used to characterize the degree of decrease in mold surface temperature after the cooling water absorbs heat at each acquisition moment. The expression is:

[0082] In the formula, represents the temperature drop at the nth acquisition moment; b represents the absolute value of the slope of the fitting line of all two-dimensional differential data points; t n-1,n It represents the difference of mold surface temperature between the n-1th and nth acquisition moments; norm() is the normalization function. Since there is insufficient data when calculating the temperature drop at the first acquisition moment, the temperature drop at the first acquisition moment is not calculated.

[0083] In this embodiment, the difference between the mold surface temperatures is the absolute value of the difference. As other implementation methods, based on the measurable difference between the mold surface temperatures, the implementer may adopt other calculation methods, such as ratio, square of the difference, etc., and this application does not impose any special restrictions.

[0084] It should be noted that: during all image acquisitions, when the instantaneous drop rate of the mold surface temperature shows an increasing trend, the greater the absolute value of the slope of the fitting straight line; and when the instantaneous drop rate of the mold surface temperature at the nth acquisition moment is greater, that is, the greater the absolute value of the difference in the mold surface temperature between the nth acquisition moment and the previous acquisition moment, the greater the degree of drop in the mold surface temperature after the cooling water absorbs heat at the nth acquisition moment, that is, the greater the degree of temperature drop at the nth acquisition moment. The schematic diagram of the process for determining the degree of temperature drop is shown in the figure. Figure 2 shown.

[0085] The cooling water temperature differences at all sampling moments are arranged in time series to form a cooling water temperature difference sequence, and the first-order difference sequence of the cooling water temperature difference sequence is obtained to characterize the change in temperature change rate of the cooling water in the cooling circuit at each sampling moment after absorbing the temperature of the surface of the plastic injection mold.

[0086] With the serial number of the data in the first-order difference sequence of the cooling water temperature difference sequence as the horizontal coordinate and the data as the vertical coordinate, the data and their serial numbers in the first-order difference sequence of the cooling water temperature difference sequence are combined into two-dimensional data points, which are recorded as temperature difference data points. The absolute value of the slope of the fitting straight line of the temperature difference data point can be used to characterize the changing trend of the instantaneous rising rate of the cooling water temperature over time during all image acquisition periods.

[0087] The absolute value of the difference in cooling water temperature between each acquisition moment and the previous acquisition moment is calculated and recorded as the temperature difference. The normalized value of the product of the absolute value of the slope corresponding to the temperature difference data point and the temperature difference is used as the temperature rise degree at each acquisition moment. In particular, since there is insufficient data when calculating the temperature rise degree at the first acquisition moment, the temperature rise degree at the first acquisition moment is not calculated.

[0088] In this embodiment, the Min-Max normalization method is used to normalize the product of the absolute value of the slope corresponding to the temperature difference data point and the temperature difference. As other implementation methods, on the basis of being able to normalize the product of the absolute value of the slope corresponding to the temperature difference data point and the temperature difference, the implementer may use other existing technologies for normalization, such as the Z-Score normalization method, the decimal calibration normalization method, etc., and this application does not impose any special restrictions.

[0089] It should be noted that: during all image acquisition periods, when the instantaneous rise rate of the cooling water temperature shows an increasing trend, the absolute value of the slope of the fitting straight line is larger; and the larger the instantaneous rise rate of the cooling water temperature at the nth acquisition moment, that is, the larger the absolute value of the difference in cooling water temperature between the nth acquisition moment and the previous adjacent acquisition moment, then at the nth acquisition moment, the cooling water in the cooling circuit absorbs the temperature of the surface of the plastic injection mold, and the greater the degree of temperature rise, that is, the greater the degree of temperature rise at the nth acquisition moment.

[0090] Step 2.3, based on the temperature drop degree and the temperature rise degree, obtain the first flow velocity impact value at each collection time.

[0091] Furthermore, based on the degree of temperature drop and temperature rise at each acquisition moment, the first flow rate impact value at each acquisition moment is obtained, which is used to characterize the cooling efficiency of the cooling water on the plastic injection mold at each acquisition moment. The impact of the cooling water flow rate is expressed as follows:

[0092] Where S1(n) represents the first flow velocity impact value at the nth acquisition moment; Respectively represent the temperature drop and temperature rise at the nth acquisition moment; norm() represents the normalization function; α represents a value greater than 0, the purpose of which is to avoid the denominator being 0. The value of α is preset by humans and can be set by the implementer. In this embodiment, the value of α is 0.01. In particular, since there is insufficient data when calculating the first flow velocity influence value at the first acquisition moment, the first flow velocity influence value at the first acquisition moment is not calculated.

[0093] It should be noted that: at the nth acquisition moment, the smaller the degree of decrease of the mold surface temperature after the cooling water absorbs heat, that is, the smaller the value of the temperature drop, and the smaller the degree of increase of the cooling water in the cooling circuit after absorbing the temperature of the plastic injection mold surface, that is, the smaller the value of the temperature rise, then the cooling efficiency of the cooling water in the cooling circuit for the plastic injection mold is lower, and the cooling water flow rate should be increased at this time, that is, the greater the value of the first flow rate influence value. The flow chart for determining the first flow rate influence value is as follows: Figure 3 shown.

[0094] Step 3, determining the second flow rate influence value by the uniformity of the surface temperature distribution of the plastic injection mold and the variation trend of the uniformity.

[0095] Although the increase in the cooling water flow rate in the cooling circuit will enhance the turbulence between the fluids in the cooling water, thereby increasing the heat exchange efficiency of the cooling water, and further improving the cooling efficiency of the cooling water on the mold surface temperature, the increase in the cooling water flow rate will lead to increased friction between the fluid and the heat exchange surface, which may cause local overheating of the heat exchange surface. The higher the cooling water flow rate, the more likely it is to cause uneven mold surface temperature. Uneven mold surface temperature will cause plastic waste products in plastic injection molds to easily produce defects such as warping and deformation, resulting in a decrease in the qualified rate of plastic waste products, thereby reducing the recycling rate of plastic waste.

[0096] Step 3.1, extracting each connected domain of the mold pixel points in each infrared thermal image, and determining the mold temperature uniformity at each acquisition time based on the fluctuation degree and distribution range of the temperature values ​​of all pixel points in all the connected domains in each infrared thermal image.

[0097] Based on the above analysis, since the cooling water pipes on the surface of the plastic injection mold will divide the surface of the plastic injection mold into multiple areas, the connected domains of all mold pixels in the infrared thermal image An are extracted to obtain each connected domain, and each connected domain corresponds to an area on the surface of the plastic injection mold. The extraction of connected domains is a well-known technology and will not be repeated in this application.

[0098] Based on the fluctuation degree and distribution range of the temperature values ​​of all pixels in each connected domain, the temperature uniformity of each connected domain is determined to characterize the uniformity of the temperature distribution of the surface area of ​​the plastic injection mold corresponding to each connected domain. The expression is:

[0099] In the formula, Represents the mth connected domain in the infrared thermal image An at the nth acquisition time The temperature uniformity of The discrete degree and range of the temperature values ​​of all pixels in the ; β represents a preset value greater than 0, the purpose of which is to avoid the denominator being 0. The value of β is preset manually and can be set by the implementer. In this embodiment, the value of β is 0.01.

[0100] In this embodiment, the degree of dispersion is the standard deviation. As other implementation methods, on the basis of being able to measure the degree of unevenness of temperature values, the implementer may use other existing statistics for measurement, such as variance, coefficient of variation, etc., and this application does not impose any special restrictions.

[0101] It should be noted that: connected domain The closer the temperatures of the corresponding locations on the surface of the plastic injection mold are, the smaller c1 is, and the connected domain The smaller the temperature range in the corresponding plastic injection mold surface area, the smaller c2 is, and the connected domain The more uniform the temperature distribution in the corresponding plastic injection mold surface area, the more connected the domain The greater the temperature uniformity.

[0102] Furthermore, based on the distribution of the temperature uniformity of all connected domains in the infrared thermal images at each acquisition time and the distribution range of the temperature values ​​of the pixels in the mold pixel set, the mold temperature uniformity at each acquisition time is determined to characterize the uniformity of the temperature distribution of the entire mold surface at each acquisition time. The expression is:

[0103] Where U n It represents the mold temperature uniformity at the nth acquisition moment; E1 represents the mean of the temperature uniformity of all connected domains in the infrared thermal image An; E2 represents the range of the temperature values ​​of all pixels in the mold pixel set JN; γ represents a preset value greater than 0, the purpose of which is to avoid the denominator being 0. The value of γ is preset manually and can be set by the implementer. In this embodiment, the value of γ is 0.01.

[0104] It should be noted that: at the nth acquisition moment, the more uniform the temperature distribution of each area on the surface of the plastic injection mold, the larger E1 is, and the smaller the extreme difference of the mold surface temperature is, the smaller E2 is, the more uniform the temperature distribution of the entire mold surface is, and the greater the mold temperature uniformity at the nth acquisition moment is. The schematic diagram of the mold temperature uniformity determination process is as follows Figure 4 shown.

[0105] Step 3.2, combining the trend change degree of the mold temperature uniformity at all sampling moments and the mold temperature uniformity, determining the second flow rate influence value at each sampling moment.

[0106] The acquisition time and mold temperature uniformity are used as the horizontal and vertical coordinates respectively. Each acquisition time and its mold temperature uniformity are composed of two-dimensional data points, which are recorded as two-dimensional temperature data points. A straight line is fitted to the temperature data points. The slope of the fitting line is used to characterize the change trend of the uniformity of the temperature distribution on the entire mold surface over time during all image acquisition periods.

[0107] Furthermore, based on the slope of the fitting straight line of the two-dimensional temperature data points and the mold temperature uniformity at each acquisition time, the second flow rate impact value at each acquisition time is determined to characterize the impact of the uneven temperature distribution of the entire mold surface on the cooling water flow rate at each acquisition time. The expression is:

[0108] S2(n) represents the second flow velocity impact value at the nth acquisition moment; k represents the slope of the fitting line of all two-dimensional temperature data points; U n It represents the mold temperature uniformity at the nth acquisition moment; ε represents a preset value greater than 0, the purpose of which is to avoid the denominator being 0. The value of ε is preset manually and can be set by the implementer. In this embodiment, the value of ε is 0.01; norm() represents a normalization function; exp() represents an exponential function with a natural constant as the base.

[0109] It should be noted that during all image acquisition periods, the more obvious the downward trend of the uniformity of the temperature distribution on the entire mold surface is, the smaller exp(k) is; and at the nth acquisition moment, the more uneven the temperature distribution on the entire mold surface is, the smaller U n The smaller it is, the more the cooling water flow rate should be reduced at the nth collection moment to reduce the unevenness of the mold surface temperature distribution, and the greater the value of the second flow rate influence value at the nth collection moment.

[0110] Step 4, comprehensively analyzing the upper limit and lower limit of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value, to determine the flow rate adjustment value of the cooling water at each collection time.

[0111] Furthermore, based on the maximum and minimum values ​​of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value at each collection time, the flow rate adjustment value of the cooling water at each collection time is determined to characterize the adjustment result of the cooling water flow rate at each collection time, and the expression is:

[0112] Wherein, V(n) represents the flow rate adjustment value of cooling water at the nth acquisition moment; v1 and v2 represent the maximum and minimum flow rates of cooling water when cooling the plastic injection mold, respectively; S1(n) and S2(n) represent the first flow rate influence value and the second flow rate influence value, respectively, at the nth acquisition moment; σ represents a value preset to be greater than 0, in order to avoid the denominator being 0. The value of σ is preset manually and can be set by the implementer. In this embodiment, the value of σ is 0.01; norm() represents the normalization function. In which, since there is insufficient data when calculating the flow rate adjustment value at the first acquisition moment, the flow rate adjustment value at the first acquisition moment is not calculated.

[0113] It should be noted that: at the nth collection moment, the larger S1(n) is, the more the cooling water flow rate should be increased to improve the cooling efficiency of the cooling water in the cooling circuit on the plastic injection mold. The larger the adjustment result of the cooling water flow rate should be, that is, V(n) should be larger; and the larger S2(n) is, the more the cooling water flow rate should be reduced to reduce the possibility of defects such as warping and deformation of plastic waste products in the plastic injection mold due to the uneven distribution of the surface temperature of the plastic injection mold. The smaller the adjustment result of the cooling water flow rate should be, that is, V(n) should be smaller. The flow rate adjustment value acquisition process diagram is shown in the figure. Figure 5 shown.

[0114] Step 5: Adjust the flow rate of the cooling water at the current collection time based on the flow rate adjustment value.

[0115] The flow rate adjustment value and flow rate of the cooling water at the current collection moment are input into the PID controller, and a control signal of the cooling water flow rate is output to adjust the flow rate of the cooling water to the flow rate adjustment value, wherein the flow rate adjustment value of the cooling water at the current collection moment is used as the target value of the PID controller, and the PID controller adjusts the flow rate of the cooling water at the current collection moment by the difference between the flow rate adjustment value and the flow rate of the cooling water at the current collection moment.

[0116] Based on the same inventive concept as the above method, the embodiment of the present application also provides a cooling and regulating device applied to a plastic injection mold, comprising:

[0117] A cooling process related information acquisition module is used to acquire an infrared thermal image of a cooling circuit of a plastic injection mold at each acquisition time, and to acquire the difference in cooling water temperature between an inlet end and an outlet end of the cooling circuit at each acquisition time, recorded as a temperature difference, and a cooling water flow rate at the inlet end;

[0118] The cooling process related information analysis module is used to obtain the mold pixel points in each infrared thermal image based on the distribution of the temperature values ​​of the pixel points in each infrared thermal image;

[0119] Calculate the average level of the temperature values ​​of all the mold pixel points in each infrared thermal image, and determine the degree of temperature drop and temperature rise at each acquisition moment based on the average level at all acquisition moments, the degree of trend change of the temperature difference, and the difference between the average level and the temperature difference at each acquisition moment and its adjacent acquisition moment;

[0120] Based on the temperature drop degree and the temperature rise degree, obtaining a first flow velocity impact value at each collection time;

[0121] Extracting each connected domain of the mold pixel points in each infrared thermal image, and determining the mold temperature uniformity at each acquisition time based on the fluctuation degree and distribution range of the temperature values ​​of all pixel points in all the connected domains in each infrared thermal image;

[0122] Determine the second flow rate impact value at each sampling moment by combining the trend change degree of the mold temperature uniformity at all sampling moments and the mold temperature uniformity;

[0123] Comprehensively analyzing the upper limit and lower limit of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value, to determine the flow rate adjustment value of the cooling water at each collection time;

[0124] The cooling water flow rate regulating module is used to regulate the flow rate of the cooling water at the current collection time based on the flow rate adjustment value and the flow rate of the cooling water at the current collection time.

[0125] Based on the same inventive concept as the above method, an embodiment of the present application also provides a cooling and adjustment system for plastic injection molds, 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 cooling and adjustment methods for plastic injection molds are implemented.

[0126] In summary, the present application comprehensively analyzes the increase in cooling water temperature and the decrease in mold surface temperature, determines the first flow rate influence value, reflects the cooling efficiency of cooling water on the plastic injection mold, comprehensively considers the influence of cooling water flow rate on cooling water temperature and plastic injection mold surface temperature, and improves the accuracy of analyzing cooling water flow rate on cooling efficiency of plastic injection mold;

[0127] Furthermore, the second flow rate influence value is determined by the uniformity of the surface temperature distribution of the plastic injection mold and the change trend of the uniformity, thereby improving the accuracy of analyzing the influence of the cooling water flow rate on the distribution uniformity of the surface temperature of the plastic injection mold;

[0128] Furthermore, the flow rate adjustment value is determined in combination with the first flow rate influence value and the second flow rate influence value, and the cooling water flow rate is adjusted using a PID controller based on the flow rate adjustment value. The influence of the cooling water flow rate on the cooling efficiency of the plastic injection mold and the distribution uniformity of the mold surface temperature is fully considered, and the cooling water flow rate is adjusted more accurately, thereby improving the accuracy of controlling the temperature of the plastic injection mold and avoiding the problem in the traditional method that the cooling water flow rate cannot achieve the expected cooling effect, thereby shortening the production cycle of plastic products and improving the quality of plastic products.

[0129] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and the block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0130] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the basic features of the present application. Therefore, no matter from which point of view, the above embodiments of the present application should be regarded as exemplary and non-restrictive.

Claims

1. A cooling and regulating method for a plastic injection mold, characterized in that: The method comprises the following steps: Obtaining infrared thermal images of a cooling circuit of a plastic injection mold at each acquisition time, obtaining a difference in cooling water temperature between an inlet end and an outlet end of the cooling circuit at each acquisition time, recorded as a temperature difference, and a cooling water flow rate at the inlet end; Based on the distribution of the temperature values ​​of the pixel points in each infrared thermal image, the mold pixel points in each infrared thermal image are obtained; Analyze the change trend of the temperature value of the mold pixel point in the infrared thermal image at all acquisition moments, the change trend of the temperature difference, and the difference of the temperature value of the mold pixel point between each acquisition moment and its adjacent acquisition moment, and the difference of the temperature difference, to determine the degree of temperature drop and temperature rise at each acquisition moment; Based on the temperature drop degree and the temperature rise degree, obtaining a first flow velocity impact value at each collection time; Extracting each connected domain of the mold pixel points in each infrared thermal image, and determining the mold temperature uniformity at each acquisition time based on the fluctuation degree and distribution range of the temperature values ​​of all pixel points in all the connected domains in each infrared thermal image; Determine the second flow rate impact value at each sampling moment by combining the trend change degree of the mold temperature uniformity at all sampling moments and the mold temperature uniformity; Comprehensively analyzing the upper limit and lower limit of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value, to determine the flow rate adjustment value of the cooling water at each collection time; The flow rate of the cooling water at the current collection time is adjusted based on the flow rate adjustment value.

2. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The process of obtaining the pixel points of the mold is as follows: Obtain the segmentation threshold of the temperature values ​​of all pixels in each infrared thermal image; The pixels in each infrared thermal image whose temperature value is greater than the segmentation threshold are regarded as mold pixels.

3. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The process of determining the temperature drop degree and the temperature rise degree is as follows: The average of the temperature values ​​of all the mold pixel points in the infrared thermal image at each acquisition time is used as the mold surface temperature at each acquisition time; and the first-order difference sequence of the mold surface temperature at all acquisition times is obtained; Get the absolute value of the slope of the fitted line for all data points in the first-order difference sequence; The difference in mold surface temperature between each sampling moment and its adjacent previous sampling moment is recorded as the surface temperature difference; The normalized value of the product of the absolute value and the surface temperature difference is used as the temperature drop degree at each acquisition time; The absolute value of the difference in cooling water temperature between the inlet and outlet at each sampling moment is recorded as the cooling water temperature difference; The same calculation method as the temperature drop degree at each sampling moment is adopted, and the mold surface temperature is replaced by the cooling water temperature difference to calculate the temperature rise degree at each sampling moment.

4. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The expression of the first flow velocity influence value is: Where S1(n) represents the first flow velocity impact value at the nth acquisition moment; They respectively represent the degree of temperature drop and the degree of temperature rise at the nth acquisition moment; norm() represents the normalization function; α represents a preset value greater than 0.

5. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The process of determining the mold temperature uniformity is as follows: Based on the discrete degree and range of the temperature values ​​of all pixels in each connected domain, the temperature uniformity of each connected domain is determined; Calculate the average temperature uniformity of all connected domains corresponding to each acquisition moment; Calculate the temperature range of all mold pixel points in the infrared thermal image at each acquisition time, and record it as the temperature range; The mold temperature uniformity is positively correlated with the average value, and negatively correlated with the temperature extreme difference.

6. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The process of determining the second flow velocity influence value is as follows: Each acquisition moment and its mold temperature uniformity are respectively composed into two-dimensional data points, which are recorded as two-dimensional temperature data points; The expression of the second flow velocity influence value at each acquisition time is: S2(n) represents the second flow velocity impact value at the nth acquisition moment; k represents the slope of the fitting line of all two-dimensional temperature data points; U n It indicates the mold temperature uniformity at the nth acquisition moment; ε indicates a preset value greater than 0; norm() indicates a normalization function; exp() indicates an exponential function with a natural constant as the base.

7. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The expression of the flow rate adjustment value is: Wherein, V(n) represents the flow rate adjustment value of cooling water at the nth collection moment; v1 and v2 represent the maximum and minimum flow rates of cooling water when cooling the plastic injection mold, respectively; S1(n) and S2(n) represent the first flow rate influence value and the second flow rate influence value at the nth collection moment, respectively; σ represents a preset value greater than 0; norm() represents the normalization function.

8. The cooling and regulating method for plastic injection mold according to claim 1, characterized in that: The method for adjusting the flow rate of cooling water at the current collection time based on the flow rate adjustment value is: The flow rate adjustment value and flow rate of the cooling water at the current collection moment are input into the PID controller, and a control signal of the cooling water flow rate is output to adjust the flow rate of the cooling water to the flow rate adjustment value.

9. A cooling and regulating device for a plastic injection mold, characterized in that: The device comprises: A cooling process related information acquisition module is used to acquire an infrared thermal image of a cooling circuit of a plastic injection mold at each acquisition time, and to acquire the difference in cooling water temperature between an inlet end and an outlet end of the cooling circuit at each acquisition time, recorded as a temperature difference, and a cooling water flow rate at the inlet end; The cooling process related information analysis module is used to obtain the mold pixel points in each infrared thermal image based on the distribution of the temperature values ​​of the pixel points in each infrared thermal image; Calculate the average level of the temperature values ​​of all the mold pixel points in each infrared thermal image, and determine the degree of temperature drop and temperature rise at each acquisition moment based on the average level at all acquisition moments, the degree of trend change of the temperature difference, and the difference between the average level and the temperature difference at each acquisition moment and its adjacent acquisition moment; Based on the temperature drop degree and the temperature rise degree, obtaining a first flow velocity impact value at each collection time; Extracting each connected domain of the mold pixel points in each infrared thermal image, and determining the mold temperature uniformity at each acquisition time based on the fluctuation degree and distribution range of the temperature values ​​of all pixel points in all the connected domains in each infrared thermal image; Determine the second flow rate impact value at each sampling moment by combining the trend change degree of the mold temperature uniformity at all sampling moments and the mold temperature uniformity; Comprehensively analyzing the upper limit and lower limit of the cooling water flow rate when cooling the plastic injection mold, as well as the first flow rate influence value and the second flow rate influence value, to determine the flow rate adjustment value of the cooling water at each collection time; The cooling water flow rate regulating module is used to regulate the flow rate of the cooling water at the current collection time based on the flow rate adjustment value and the flow rate of the cooling water at the current collection time.

10. A cooling and regulating system for a plastic injection mold, 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 cooling adjustment method applied to a plastic injection mold as described in any one of claims 1 to 8 are implemented.

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