Cooling device for blow molds and cooling control method thereof

Abstract

This invention relates to the field of plastic molding technology, specifically to a cooling device and cooling control method for blow molding dies. The method includes: acquiring the inlet and outlet temperatures of the cooling circuit of the blow molding die; determining the current process stage of the blow molding process cycle using outlet temperature change information or inlet / outlet temperature change information; determining the current set inlet / outlet temperature difference for the current process stage based on the previous set inlet / outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage; determining the temperature difference adjustment error between the current actual inlet / outlet temperature difference and the current set inlet / outlet temperature difference; and calculating and outputting a signal in real time using a PID controller based on the temperature difference adjustment error to adjust the flow rate of the cooling medium in the cooling circuit. Through the technical solution of this invention, precise closed-loop control of the mold cooling intensity is achieved, thereby significantly improving the finished product quality of plastic products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic forming, in particular to a cooling device for blow molding mold and a cooling control method thereof. BACKGROUND

[0002] Blow molding is a plastic processing technology (such as plastic bottles, plastic barrels, etc.) in which a heated and softened plastic parison is inflated by blowing air into it, so that it adheres to the mold cavity and is cooled and shaped into a product. The mold is a tool for shaping plastic and other materials into a specific shape. To ensure the quality and consistency of plastic products, the plastic must be uniformly and rapidly cooled from the molten state to the glass or crystalline state. If the cooling is uneven, it will cause the products to shrink unevenly, resulting in defects such as warping, deformation, residual stress, etc., affecting the dimensional stability and mechanical strength. Therefore, precise cooling control is the key to ensuring the quality consistency of each mold product.

[0003] Generally, a PID (Proportional-Integral-Derivative) controller is used to dynamically adjust the cooling water flow in the blow molding mold cooling control according to the temperature difference between the inlet and outlet of the cooling device. The system monitors and calculates the actual temperature difference in real time, compares it with the preset target temperature difference by the PID controller, and obtains the error value. If the actual temperature difference is too large, it means that the water flow is insufficient and the heat dissipation is not timely, so the controller will increase the opening degree of the regulating valve or the speed of the water pump to increase the flow. If the actual temperature difference is too small, it means that the flow is too large and the heat exchange is not sufficient, so the controller will reduce the output to reduce the flow, achieving energy saving. Through this continuous feedback adjustment, the system can accurately stabilize the actual temperature difference around the target value, thereby optimizing the energy efficiency while ensuring the cooling effect.

[0004] In the prior art, the blow molding process has a significant periodicity. In a forming cycle, the mold goes through stages such as closing, blow molding and pressure maintaining, cooling and solidification, and opening and taking out. When the high-temperature parison enters the mold cavity and the mold is closed, the mold thermal load increases instantaneously, causing the outlet temperature of the cooling circuit to rise sharply, and the actual temperature difference is much higher than the set value of the PID controller. The controller will determine this as a serious deviation and output a large control signal to drive the water valve to nearly full open or the water pump to nearly full speed. As the cooling progresses, the heat released by the plastic melt gradually decreases, and the target temperature difference should naturally fall. By the time the mold is opened and the product is taken out, the mold thermal load is almost zero, the outlet temperature quickly drops to a temperature close to that of the inlet, and the temperature difference approaches zero. At this time, the PID controller will determine that the cooling is excessive and greatly reduce the output, causing the valve to nearly close or the water pump speed to drop sharply. This dramatic fluctuation in thermal load caused by the periodicity of the process makes the traditional PID control system continuously respond to large disturbances, making it difficult to stabilize and resulting in poor quality of plastic products. SUMMARY

[0005] To address the technical problem of poor quality plastic products under traditional PID cooling control caused by severe fluctuations in heat load due to the cyclical nature of blow molding processes, this invention aims to provide a cooling device and cooling control method for blow molding molds. The specific technical solution adopted is as follows:

[0006] This invention provides a cooling control method for blow molding dies, the method comprising:

[0007] Obtain the inlet and outlet temperatures of the cooling circuit of the blow molding die, and use the outlet temperature change information or the inlet and outlet temperature change information to determine the current process stage of the blow molding process cycle.

[0008] Based on the previous set inlet and outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage, determine the current set inlet and outlet temperature difference of the current process stage.

[0009] Determine the temperature difference adjustment error between the current actual inlet and outlet temperature difference and the current set inlet and outlet temperature difference, and use the PID controller to calculate the output signal in real time based on the temperature difference adjustment error to adjust the flow rate of the cooling medium in the cooling circuit.

[0010] The current process stages include the mold closing and blowing stage, the pressure holding and cooling stage, the mold opening and part removal stage, and the pre-mold closing preparation stage.

[0011] Furthermore, the current process stage of the blow molding process cycle is determined using information on outlet temperature changes, including:

[0012] Determine the outlet temperature difference between the current moment and the previous adjacent moment in the blow molding process cycle;

[0013] If the normalized outlet temperature difference is greater than the first preset threshold, the current process stage of the blow molding process cycle is determined to be the mold closing and blowing stage.

[0014] Furthermore, based on the previously set inlet / outlet temperature difference of the previous process stage and the temperature change characteristics of the current process stage, the current set inlet / outlet temperature difference of the current process stage is determined, including:

[0015] The current set inlet and outlet temperature difference for the mold closing and blowing stages is determined by using the set inlet and outlet temperature difference during the pre-mold closing preparation stage and the outlet temperature difference between the mold closing and blowing stages.

[0016] Furthermore, the current process stage of the blow molding process cycle is determined using inlet and outlet temperature change information, including:

[0017] Determine the current inlet and outlet temperature difference at the current moment after the start of the mold closing and blowing stages, and the previous inlet and outlet temperature difference at the previous adjacent moment;

[0018] The probability that the current process stage is the pressure holding and cooling stage can be determined by using the current inlet and outlet temperature difference and the previous inlet and outlet temperature difference.

[0019] If the probability of the holding and cooling stage is greater than the second preset threshold, the current process stage of the blow molding process cycle is determined to be the holding and cooling stage.

[0020] Furthermore, based on the previously set inlet and outlet temperature difference of the previous process stage, the current set inlet and outlet temperature difference of the current process stage is determined, including:

[0021] Determine the temperature difference between the set inlet / outlet temperature difference at the end of the mold closing and blowing stages and the standard steady-state inlet / outlet temperature difference;

[0022] Determine the duration of the pressure holding and cooling phase from its start to the current moment, and use the temperature difference and the duration of the phase to determine the current set inlet and outlet temperature difference for the pressure holding and cooling phase.

[0023] Furthermore, the current process stage of the blow molding process cycle is determined using information on outlet temperature changes, including:

[0024] Determine the outlet temperature difference between the current moment after the start of the pressure holding and cooling phase and the previous adjacent moment;

[0025] If the normalized outlet temperature difference is greater than the third preset threshold, the current process stage of the blow molding process cycle is determined to be the mold opening and part removal stage.

[0026] Furthermore, based on the temperature change characteristics of the current process stage, the current set inlet and outlet temperature difference for the current process stage is determined, including:

[0027] Determine the current actual inlet and outlet temperature difference after the start of the mold opening and part removal stages. If the current actual inlet and outlet temperature difference is less than the preset temperature threshold, set the preset minimum inlet and outlet temperature difference to the current set inlet and outlet temperature difference for the mold opening and part removal stages.

[0028] Furthermore, the current process stage of the blow molding process cycle is determined using information on outlet temperature changes, including:

[0029] Determine the degree of temperature dispersion of the outlet from the start of the mold opening and part removal stage to the current time, and use the degree of temperature dispersion of the outlet to determine the possibility that the current process stage is the preparatory stage before mold closing.

[0030] If the probability of the pre-mold closing preparation stage is greater than the fourth preset threshold, the current process stage of the blow molding process cycle is determined to be the pre-mold closing preparation stage.

[0031] Furthermore, based on the temperature change characteristics of the current process stage, the current set inlet and outlet temperature difference for the current process stage is determined, including:

[0032] If the dispersion of the outlet temperature during the pre-mold closing preparation stage is less than a preset dispersion threshold, the preset maximum inlet and outlet temperature difference is set as the current set inlet and outlet temperature difference during the pre-mold closing preparation stage.

[0033] The present invention also provides a cooling device for blow molding molds, the device being used to implement the cooling control method for blow molding molds as described in any of the preceding claims; the device comprising:

[0034] The temperature monitoring module is used to acquire the inlet and outlet temperatures of the cooling circuit of the blow molding die, and to determine the current process stage of the blow molding process cycle using the outlet temperature change information or the inlet and outlet temperature change information.

[0035] The parameter adjustment module is used to determine the current set inlet and outlet temperature difference of the current process stage based on the previous set inlet and outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage; determine the temperature difference adjustment error between the current actual inlet and outlet temperature difference and the current set inlet and outlet temperature difference; and calculate the output signal in real time through the PID controller based on the temperature difference adjustment error to adjust the flow rate of the cooling medium in the cooling circuit.

[0036] The current process stages include the mold closing and blowing stage, the pressure holding and cooling stage, the mold opening and part removal stage, and the pre-mold closing preparation stage.

[0037] The present invention has the following beneficial effects:

[0038] This invention fully analyzes and utilizes the phased characteristics of the blow molding process cycle, dynamically adjusts the target temperature difference setpoint of the PID controller (the target temperature difference refers to the inlet and outlet temperature difference of the cooling circuit), and then, based on the set dynamic target temperature difference, the PID controller calculates the output signal in real time, adjusts the flow rate of the cooling medium, and realizes precise closed-loop control of the mold cooling intensity, thereby significantly improving the finished product quality of plastic products.

[0039] Specifically, the core of this invention is to dynamically adjust the target temperature difference setpoint of the PID controller based on the four stages of the blow molding process cycle. The first stage of the blow molding cycle is the mold closing and blowing stage. Because heat rushes in instantly during mold closing and blowing, the outlet temperature rises sharply. Based on this, the start time of the mold closing and blowing stage can be identified. Since this stage requires high-intensity cooling, the target temperature difference should be fine-tuned based on the intensity of the initial thermal shock. The second stage of the blow molding cycle is the pressure holding and main cooling stage. After the high-intensity thermal shock, the temperature rise rate decreases significantly. Based on this, the start time of the pressure holding and main cooling stage can be identified. Then, the target temperature difference should smoothly decrease from the initial high value to the standard value at steady production as cooling progresses. The third stage of the blow molding cycle is the mold opening and part removal stage. Since the heat load disappears after mold opening, the outlet temperature drops rapidly. Based on this, the start time of the mold opening and part removal stage can be identified. Since no cooling is required in this stage, the target temperature difference can be set to an extremely low value to minimize flow and save energy. The fourth stage of the blow molding process cycle is the pre-mold closing preparation stage. This stage first identifies the start time of the pre-mold closing preparation based on time. Then, before the start of the next cycle, to prepare for increased cooling capacity, the target temperature difference is set to the maximum temperature difference. Finally, the above process is repeated, continuously and dynamically adjusting the target temperature difference setpoint of the PID controller within the blow molding process cycle. Attached Figure Description

[0040] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A flowchart illustrating the steps of a cooling control method for blow molding dies according to an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of a cooling control method for blow molding dies provided in one embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the hardware operating environment of the cooling control equipment for blow molding molds involved in the embodiments of the present invention;

[0044] Figure 4 This is a schematic diagram of the frame structure of a cooling device for blow molding molds according to an embodiment of the present invention. Detailed Implementation

[0045] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a cooling control method for blow molding dies proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0047] The specific solution of a cooling control method for blow molding dies provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0048] Example 1:

[0049] For a cooling control method for blow molding dies provided by this invention, please refer to [link / reference]. Figure 1 The diagram illustrates a flowchart of a cooling control method for blow molding dies provided in an embodiment of the present invention.

[0050] The cooling control method for the blow molding die includes:

[0051] Step S1: Obtain the inlet and outlet temperatures of the cooling circuit of the blow molding die, and use the outlet temperature change information or the inlet and outlet temperature change information to determine the current process stage of the blow molding process cycle; wherein, the current process stage includes the mold closing and blowing stage, the pressure holding and cooling stage, the mold opening and part removal stage, and the pre-mold closing preparation stage.

[0052] Step S2: Determine the current set inlet and outlet temperature difference of the current process stage based on the previous set inlet and outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage.

[0053] In this embodiment, firstly, a cooling device for the blow molding die (hereinafter referred to as "the die") is configured: a drilled cooling channel can be used, in which cooling channels are drilled in the longitudinal and transverse directions inside the die wall. The diameter of the channel is, for example, 15 mm, and for large dies, it can reach 30 mm. The distance between the cooling channel of the cooling circuit and the surface of the cavity should be consistent, which is 1-2 times the diameter of the channel, and the center distance between two adjacent channels should be 3-5 times the diameter of the channel to ensure uniform cooling.

[0054] A Resistance Temperature Detector (RTD) is installed at both the inlet and outlet of the cooling circuit to collect temperature data at fixed intervals (e.g., 10 milliseconds). This data is used to monitor the inlet and outlet temperatures of the cooling medium (usually water), specifically the inlet (water) temperature and outlet (water) temperature. The temperature change curve at the outlet of the cooling device is shown in the figure below. Figure 2 As shown, Figure 2 This is a schematic diagram of the temperature change curve at the outlet of the cooling device in the blow molding process. Real-time data transmission is achieved through PLC (Programmable Logic Controller) system communication.

[0055] In one embodiment, step S1, which uses outlet temperature change information to determine the current process stage of the blow molding process cycle, includes:

[0056] Determine the outlet temperature difference between the current moment and the previous adjacent moment in the blow molding process cycle;

[0057] If the normalized outlet temperature difference is greater than the first preset threshold, the current process stage of the blow molding process cycle is determined to be the mold closing and blowing stage.

[0058] In this embodiment, before mold closing, the mold is in an unloaded or low-load state, and the cooling system only needs to remove the residual heat of the mold body, resulting in a stable and low outlet temperature. Once the mold closing action is completed, the high-temperature preform (typically exceeding 160°C) is sealed within the mold cavity and immediately inflated, and the large amount of heat it contains is instantly and violently transferred to the cooling channel walls through the mold steel body. This causes the cooling medium flowing through the channels to be rapidly heated, resulting in a sudden increase in temperature readings at the outlet.

[0059] Based on the above description, the following formula can be constructed to represent the probability that the t-th moment (as the current moment) in the blow molding process cycle is the start moment of the mold closing and blowing stage:

[0060]

[0061] Formula explanation: Where, This indicates the probability that the t-th moment in the blow molding process cycle is the start of the mold closing and blow-up phase. This represents the maximum and minimum value normalization function (compared to all moments of the previous blow molding process cycle, and when there is no previous blow molding process cycle, the minimum and maximum values ​​can also be preset according to the actual blow molding scenario, such as 0℃-80℃, to achieve maximum and minimum value normalization analysis). This represents the temperature at the outlet at time t in the blow molding process cycle. This represents the temperature at the outlet at time t-1 of the blow molding process cycle; the difference between the two is the outlet temperature difference.

[0062] When the probability mentioned above is greater than 0.9 (the first preset threshold, which can be adjusted according to the actual situation), it can be identified as the start of the mold closing and blowing stage. .

[0063] Based on the above embodiments, in one embodiment, step S2, determining the current set inlet and outlet temperature difference of the current process stage based on the previous set inlet and outlet temperature difference of the previous process stage and the temperature change characteristics of the current process stage, includes:

[0064] The current set inlet and outlet temperature difference for the mold closing and blowing stages is determined by using the set inlet and outlet temperature difference during the pre-mold closing preparation stage and the outlet temperature difference between the mold closing and blowing stages.

[0065] In this embodiment, during the mold closing and blowing stage, a fixed initial target temperature difference (the target temperature difference refers to the inlet and outlet temperature difference, as explained above) is set based on typical operating conditions. However, in actual production, the temperature of the parison may fluctuate: if the parison temperature in this cycle is higher than usual, it releases more heat, leading to an abnormally rapid temperature rise rate. In this case, if the target temperature difference remains fixed, the PID controller will consider the fixed initial target temperature difference to be sufficiently high, and its output flow may be insufficient to cope with this additional thermal shock, resulting in insufficient initial cooling and affecting product quality.

[0066] Conversely, if the target temperature difference is set based on a fixed value (the fourth stage of the previous cycle, i.e., the preparatory stage before mold closing),... (See subsequent embodiments for details). By adding a term proportional to the initial temperature rise rate, the system gains adaptive capability. Specifically, when an abnormally high initial temperature rise rate is detected, a higher target temperature difference is calculated using the gain coefficient k. This is equivalent to actively commanding the PID controller to provide stronger cooling capacity (greater flow rate) than usual at the moment of strongest thermal shock, suppressing the additional heat load in advance, thereby effectively smoothing out fluctuations and ensuring the consistency of product cooling quality. Therefore, the following formula can be constructed to represent the target temperature difference value of the PID controller set at time t (referring to the current time, which will not be elaborated further) during the mold closing and blowing stages:

[0067]

[0068] Formula explanation: Where, This represents the target temperature difference value set by the PID controller at time t during the mold closing and blowing stages (the current set inlet and outlet temperature difference during the mold closing and blowing stages). This represents the target temperature difference set in the fourth stage of the previous cycle; k represents a small gain coefficient (set manually, such as 0.1). This represents the temperature at the outlet at time t in the blow molding process cycle. This represents the temperature at the outlet at time t-1 of the blow molding process cycle; the difference between the two is the outlet temperature difference.

[0069] It should be noted that this may occur during the first run or when data from the previous period cannot be retrieved for any reason. Choose a preset initial reference temperature difference, such as 15°C.

[0070] The specific values ​​given in the embodiments of this invention (such as the gain coefficient of 0.1, and subsequent time constants, standard steady-state inlet and outlet temperature differences, preset minimum inlet and outlet temperature differences, and preset maximum inlet and outlet temperature differences, etc.) are all empirical values ​​obtained under typical hardware configurations and test scenarios, intended to facilitate understanding of this invention. In practical applications, those skilled in the art can adjust, calibrate, or optimize these parameters according to specific hardware performance, scenario complexity, and data characteristics, which does not constitute a limitation of this invention.

[0071] In one embodiment, step S1, which uses inlet and outlet temperature change information to determine the current process stage of the blow molding process cycle, includes:

[0072] Determine the current inlet and outlet temperature difference at the current moment after the start of the mold closing and blowing stages, and the previous inlet and outlet temperature difference at the previous adjacent moment;

[0073] The probability that the current process stage is the pressure holding and cooling stage can be determined by using the current inlet and outlet temperature difference and the previous inlet and outlet temperature difference.

[0074] If the probability of the holding and cooling stage is greater than the second preset threshold, the current process stage of the blow molding process cycle is determined to be the holding and cooling stage.

[0075] In this embodiment, during the mold closing and blow-up stages, heat is introduced instantaneously in the form of an "impact," resulting in an extremely high temperature rise rate. Once the preform is completely flush with the mold cavity and the blow-up pressure stabilizes, the essence of the process shifts from "rapid molding" to "steady-state heat dissipation." At this point, the plastic begins to solidify and release heat of crystallization or latent heat, and the heat flow changes from intense convection to a relatively gentle conduction process. Therefore, the amount of heat introduced into the mold per unit time is significantly reduced, inevitably leading to a sharp decrease in the temperature rise rate of the cooling water.

[0076] This change is reflected in the data as the first derivative (i.e., the slope) of the temperature difference-time curve rapidly drops from a large positive value to near zero, or even turns negative (the temperature difference begins to decrease). By detecting whether the rate of temperature rise decreases and stabilizes, the system can accurately determine the end of the high-intensity thermal shock. This signifies that production has entered the main stage of pressure holding and cooling, characterized by continuous and stable heat dissipation. Therefore, the following formula can be constructed to represent the probability that time t after the start of the mold closing and blowing stage in the blow molding process cycle is the start of the main stage of pressure holding and cooling:

[0077]

[0078] Formula explanation: Where, This indicates the probability that the t-th moment after the start of the mold closing and blowing stage in the blow molding process cycle is the start of the main stage of holding pressure and cooling; exp represents an exponential function with the natural constant e as the base. This represents the temperature at the outlet at time t after the start of the mold closing and inflation stages in the blow molding process. This represents the temperature at the inlet at time t after the mold closing and blowing stages of the blow molding process begin. The difference between the two is the current inlet and outlet temperature difference. This indicates the temperature at the outlet at time t-1 after the start of the mold closing and blowing stage in the blow molding process. This indicates the temperature of the inlet at time t-1 after the start of the mold closing and blowing stages in the blow molding process. The difference between the two is the previous inlet and outlet temperature difference. Indicates taking the absolute value; This represents the division-by-zero parameter, a safety value set to prevent the denominator from being 0. Its specific value can be 0.1, and its corresponding dimensions are... same.

[0079] When the probability mentioned above is greater than 0.9 (the second preset threshold, which can be adjusted), it can be identified as the start of the main pressure holding and cooling phase. .

[0080] Based on the above embodiments, in one embodiment, step S2, determining the current set inlet and outlet temperature difference of the current process stage based on the previous set inlet and outlet temperature difference of the previous process stage, includes:

[0081] Determine the temperature difference between the set inlet / outlet temperature difference at the end of the mold closing and blowing stages and the standard steady-state inlet / outlet temperature difference;

[0082] Determine the duration of the pressure holding and cooling phase from its start to the current moment, and use the temperature difference and the duration of the phase to determine the current set inlet and outlet temperature difference for the pressure holding and cooling phase.

[0083] In this embodiment, during the initial stage of the pressure holding and cooling phase, the plastic is still at a relatively high temperature. Although the heat load is not as high as at the moment of blowing, it is still substantial. If the target temperature difference is set to a low steady-state value at this time, the PID controller will prematurely reduce the cooling flow rate, resulting in insufficient cooling capacity and potentially causing localized overheating or uneven shrinkage of the product. Conversely, if a high target temperature difference is maintained throughout the process, in the later stages of cooling, when the heat of the plastic has significantly decreased, it will result in excessive cooling capacity, wasting energy and potentially causing "overcooling," thus affecting the production schedule.

[0084] Therefore, by employing a smoothly decreasing exponential decay target curve, the command control system maintains strong cooling capacity in the initial cooling phase, and then gradually and smoothly reduces the cooling intensity as the heat of the plastic naturally decreases. This "flexible" control avoids drastic fluctuations in flow rate and system state, ensuring the uniformity and stability of mold heat dissipation, which is key to achieving high-quality, high-efficiency cooling.

[0085] Based on the above description, the following formula can be constructed to represent the target temperature difference value of the PID controller set at time t during the main pressure holding and cooling phases:

[0086]

[0087] Formula explanation: Where, This represents the target temperature difference value of the PID controller set at time t during the main pressure holding and cooling phase (currently set inlet and outlet temperature difference). This represents the standard steady-state target temperature difference (standard steady-state inlet and outlet temperature difference, preset value, such as 5℃). Indicates the end time of mold closing and blow molding stages in the blow molding process cycle. The set target temperature difference value, the difference between the two refers to the aforementioned temperature difference value; exp represents an exponential function with base e; The value of t represents the start time of the main pressure holding and cooling phase, and t represents the t-th moment of the main pressure holding and cooling phase. The difference between the two values ​​refers to the aforementioned runtime. This represents a small adjustment factor, such as 0.1.

[0088] Where t and T(II) are the times when the blow molding process cycle begins, in seconds; τ is the exponentially decaying time constant, in seconds, whose value can be calibrated experimentally, and is usually 1 / 3 to 1 / 5 of the estimated total time of the holding and cooling stages, for example, 3 seconds.

[0089] In one embodiment, step S1, which uses outlet temperature change information to determine the current process stage of the blow molding process cycle, includes:

[0090] Determine the outlet temperature difference between the current moment after the start of the pressure holding and cooling phase and the previous adjacent moment;

[0091] If the normalized outlet temperature difference is greater than the third preset threshold, the current process stage of the blow molding process cycle is determined to be the mold opening and part removal stage.

[0092] In this embodiment, during the pressure-holding and cooling stage, the mold continuously absorbs heat from the plastic product, and the cooling water maintains a relatively stable temperature rise. Once the mold is opened and the product is removed, the contact between the mold and the main heat source (the plastic product) is instantly severed, and the heat load drops sharply to almost zero. However, the cooling water circulation does not stop; it continues to flow through the mold channels, but at this point, it can only carry away the limited residual heat stored in the mold body. This causes the outlet water temperature to lose continuous heat input, and its temperature will show a rapid downward trend as heat is continuously carried away.

[0093] The "inflection point" of this temperature curve—the transition from slow decay to rapid decline—clearly marks the completion of the mold opening process. Therefore, by monitoring whether the rate of temperature change exceeds a negative threshold, it is highly reliable to determine that the production cycle has entered the no-load mold opening and part removal stage. Thus, the following formula can be constructed to represent the probability that the t-th moment after the start of the main pressure holding and cooling stage of the blow molding process cycle is the start of the mold opening and part removal stage:

[0094]

[0095] Formula explanation: Where, represents the probability that the t-th moment after the start of the main stage of holding pressure and cooling in the blow molding process cycle is the start of the mold opening and part removal stage; f represents the maximum and minimum value normalization function; This indicates the temperature at the outlet at time t-1 after the start of the main stage of pressure holding and cooling in the blow molding process. This represents the temperature at the outlet at time t after the start of the main stage of pressure holding and cooling in the blow molding process. The difference between the two is the outlet temperature difference between the pressure holding and cooling stages.

[0096] When the probability mentioned above is greater than 0.9 (the third preset threshold, which can be adjusted), it can be identified as the start time of the mold opening and part removal stage. .

[0097] Based on the above embodiments, in one embodiment, step S2, determining the current set inlet and outlet temperature difference of the current process stage based on the temperature change characteristics of the current process stage, includes:

[0098] Determine the current actual inlet and outlet temperature difference after the start of the mold opening and part removal stages. If the current actual inlet and outlet temperature difference is less than the preset temperature threshold, set the preset minimum inlet and outlet temperature difference to the current set inlet and outlet temperature difference for the mold opening and part removal stages.

[0099] In this embodiment, after the mold opening and part removal stages begin, there are no more products inside the mold, and the heat load has completely disappeared. If the set target temperature difference is still maintained at a high level, the PID controller will continue to "mistakenly" believe that the cooling is insufficient, thereby commanding the water pump and valves to maintain high power operation in pursuit of an unattainable target (because there is no heat input, the actual temperature difference will inevitably approach zero), which will result in a huge waste of electrical energy.

[0100] Therefore, based on the above-mentioned actual inlet and outlet temperature difference should be close to zero, the corresponding preset temperature threshold can be set to 1℃ (which can be adjusted). When the actual inlet and outlet temperature difference is less than the preset temperature threshold, the target value can be set as the actual inlet and outlet temperature difference; or the preset minimum value (preset minimum inlet and outlet temperature difference) can be used. For example, a value of 0 or other values ​​between 0 and 1°C is set as the current inlet and outlet temperature difference during the mold opening and part removal stages. This is equivalent to issuing a clear "sleep" command to the PID controller. The PID controller will then reduce the cooling water flow rate to the minimum level necessary to maintain pipeline circulation and prevent freezing. This not only significantly reduces pump energy consumption but also avoids extreme movements of the regulating valve and pump actuator between "fully open" and "fully closed," effectively reducing mechanical wear and extending equipment life.

[0101] In one embodiment, step S1, which uses outlet temperature change information to determine the current process stage of the blow molding process cycle, includes:

[0102] Determine the degree of temperature dispersion of the outlet from the start of the mold opening and part removal stage to the current time, and use the degree of temperature dispersion of the outlet to determine the possibility that the current process stage is the preparatory stage before mold closing.

[0103] If the probability of the pre-mold closing preparation stage is greater than the fourth preset threshold, the current process stage of the blow molding process cycle is determined to be the pre-mold closing preparation stage.

[0104] In this embodiment, at the initial stage of the mold opening and part removal phase, the outlet temperature drops rapidly from a high value. When it reaches its lowest point and remains at this level for a period of time, it means that the residual heat stored in the mold body has been largely removed, and the system enters a thermodynamically stable state: the heat removed by the cooling water is nearly balanced with the heat dissipated from the mold to the environment, and the temperature no longer changes significantly. This stable state of "sustained minimum" is a clear signal that the mold opening and part removal operation has ended, and the mold is "thermally prepared" for the next production cycle. Therefore, the following formula can be constructed to represent the probability that time t after the start of the mold opening and part removal phase in the blow molding process cycle is the start time of the pre-mold closing preparation phase:

[0105]

[0106] Formula explanation: Where, This indicates the probability that the t-th moment after the start of the mold opening and part removal stage in the blow molding process cycle is the start of the preparatory stage before mold closing; exp represents an exponential function with base e; s represents the variance (the variance calculated using the outlet temperature data of the t-th moment after the start of the mold opening and part removal stage and N consecutive moments before it, where N is a preset window size, such as 50). This represents the temperature of the outlet at time t after the start of the mold opening and part removal stage in the blow molding process. This indicates the temperature of the outlet at time t-1 after the start of the mold opening and part removal stage in the blow molding process.

[0107] When the probability mentioned above is greater than 0.9 (the fourth preset threshold, which can be adjusted), it can be identified as the start time of the preparatory stage before mold closing. .

[0108] Based on the above embodiments, in one embodiment, step S2, determining the current set inlet and outlet temperature difference of the current process stage based on the temperature change characteristics of the current process stage, includes:

[0109] If the dispersion of the outlet temperature during the pre-mold closing preparation stage is less than a preset dispersion threshold, the preset maximum inlet and outlet temperature difference is set as the current set inlet and outlet temperature difference during the pre-mold closing preparation stage.

[0110] If the system maintains a minimum flow rate to save energy during the mold opening and part removal stages, the PID controller only comes out of its "sleep" state when heat rushes in and causes a temperature spike at the moment of mold closing. It then commands the valve to slowly increase from its minimum opening, resulting in significant control lag. During this lag, the mold may overheat due to insufficient initial cooling, affecting the quality of the first product.

[0111] If the dispersion (variance) of the outlet temperature during the mold opening and part removal stages is less than a preset dispersion threshold (e.g., 0.1), the current stage is considered the pre-mold closing preparation stage. Therefore, in the pre-mold closing preparation stage, the current target value is set in advance to the preset maximum temperature difference (preset maximum inlet and outlet temperature difference). (Set according to actual conditions, such as 20℃), which is equivalent to preparing the cooling system in advance before the heat bursts. The PID controller will immediately respond to this command, increasing the cooling water flow in advance, so that the mold channels are filled with high-speed flowing cooling medium. When the heat load actually hits after the mold closes, the system is "ready for battle" and can immediately and effectively remove heat, thereby smoothing the temperature fluctuation curve, weakening the peak of the initial thermal shock, achieving more stable and precise cooling control, and ensuring the consistency of product quality throughout the cycle.

[0112] Step S3: Determine the temperature difference adjustment error between the current actual inlet and outlet temperature difference and the current set inlet and outlet temperature difference; Based on the temperature difference adjustment error, the PID controller calculates the output signal in real time to adjust the flow rate of the cooling medium in the cooling circuit.

[0113] Using the above embodiments as the core control process, in the PLC's cyclic scanning task, the system will execute a "monitor-judgment-update" process once in each extremely short control cycle, thereby ensuring that the target set value of the PID controller can be kept synchronized with the dynamic process state of the mold in real time.

[0114] When a complete production cycle ends, the system's internal status flags will automatically reset, preparing to recognize the "mold closing start" signal for the next cycle, thereby enabling uninterrupted and adaptive dynamic adjustments to subsequent cycles.

[0115] The above steps have dynamically adjusted the target temperature difference setpoint of the PID controller in real time according to the phased characteristics of the blow molding process cycle. Next, the system will continuously collect the actual temperature difference and compare it with the set dynamic target temperature difference (the current set inlet and outlet temperature difference at each stage) to obtain the instantaneous error (temperature difference adjustment error). Subsequently, the PID control algorithm starts working, and its output signal u(t) is determined by the proportional, integral, and derivative terms.

[0116] This output signal u(t) will correspondingly adjust the opening of the proportional valve on the pipeline or change the speed of the variable frequency water pump, thereby directly controlling the flow rate of the cooling medium. When the actual temperature difference is lower than the target setting, the controller increases the output and increases the flow rate to enhance cooling; when the actual temperature difference is higher than the target setting, it decreases the output and reduces the flow rate to save energy. Through such continuous and minute feedback adjustment, a complete closed loop is formed, enabling the actual temperature difference to quickly and smoothly track the dynamically changing target value, ultimately achieving precise and adaptive control of the mold cooling intensity.

[0117] This invention fully analyzes and utilizes the phased characteristics of the blow molding process cycle, dynamically adjusts the target temperature difference setpoint of the PID controller (the target temperature difference refers to the inlet and outlet temperature difference of the cooling circuit), and then, based on the set dynamic target temperature difference, the PID controller calculates the output signal in real time, adjusts the flow rate of the cooling medium, and realizes precise closed-loop control of the mold cooling intensity, thereby significantly improving the finished product quality of plastic products.

[0118] Example 2:

[0119] This invention also proposes a cooling control device for blow molding molds. The device can be a programmable logic controller, a computer, a server, or a combination of multiple devices for data analysis and computation.

[0120] like Figure 3 As shown,Figure 3 This is a schematic diagram of the hardware operating environment of the cooling control equipment for blow molding molds involved in the embodiments of the present invention.

[0121] like Figure 3 As shown, the cooling control device for blow molding molds may include: a processor 1001, such as a CPU; a network interface 1004; a user interface 1003; a memory 1005; and a communication bus 1002. The communication bus 1002 is used to establish communication between these components. The user interface 1003 may include a display or an input unit such as a control panel; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001. The memory 1005, as a computer storage medium, may include a cooling control program for blow molding molds.

[0122] Those skilled in the art will understand that Figure 3 The hardware structure shown does not constitute a limitation on the device and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0123] Continue to refer to Figure 3 , Figure 3 The memory 1005, which is a computer-readable storage medium, may include an operating device, a user interface module, a network communication module, and a cooling control program for blow molding dies.

[0124] exist Figure 3 In this embodiment, the network communication module is mainly used to connect to the server and can communicate with the server for data; while the processor 1001 can call the cooling control program for blow molding stored in the memory 1005 and execute the steps in the above embodiments.

[0125] Based on the hardware structure of the cooling control device for blow molding dies described above, various embodiments of the cooling control method for blow molding dies of the present invention are implemented.

[0126] In addition, the present invention also provides a cooling device for blow molding molds, please refer to... Figure 4 The cooling device for the blow molding die includes:

[0127] Temperature monitoring module A10 is used to acquire the inlet and outlet temperatures of the cooling circuit of the blow molding die, and to determine the current process stage of the blow molding process cycle using the outlet temperature change information or the inlet and outlet temperature change information.

[0128] The parameter adjustment module A20 is used to determine the current set inlet and outlet temperature difference of the current process stage based on the previous set inlet and outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage; determine the temperature difference adjustment error between the current actual inlet and outlet temperature difference and the current set inlet and outlet temperature difference; and calculate the output signal in real time through the PID controller based on the temperature difference adjustment error to adjust the flow rate of the cooling medium in the cooling circuit.

[0129] Furthermore, the temperature monitoring module A10 is also used for:

[0130] Determine the outlet temperature difference between the current moment and the previous adjacent moment in the blow molding process cycle;

[0131] If the normalized outlet temperature difference is greater than the first preset threshold, the current process stage of the blow molding process cycle is determined to be the mold closing and blowing stage.

[0132] Furthermore, the parameter adjustment module A20 is also used for:

[0133] The current set inlet and outlet temperature difference for the mold closing and blowing stages is determined by using the set inlet and outlet temperature difference during the pre-mold closing preparation stage and the outlet temperature difference between the mold closing and blowing stages.

[0134] Furthermore, the temperature monitoring module A10 is also used for:

[0135] Determine the current inlet and outlet temperature difference at the current moment after the start of the mold closing and blowing stages, and the previous inlet and outlet temperature difference at the previous adjacent moment;

[0136] The probability that the current process stage is the pressure holding and cooling stage can be determined by using the current inlet and outlet temperature difference and the previous inlet and outlet temperature difference.

[0137] If the probability of the holding and cooling stage is greater than the second preset threshold, the current process stage of the blow molding process cycle is determined to be the holding and cooling stage.

[0138] Furthermore, the parameter adjustment module A20 is also used for:

[0139] Determine the temperature difference between the set inlet / outlet temperature difference at the end of the mold closing and blowing stages and the standard steady-state inlet / outlet temperature difference;

[0140] Determine the duration of the pressure holding and cooling phase from its start to the current moment, and use the temperature difference and the duration of the phase to determine the current set inlet and outlet temperature difference for the pressure holding and cooling phase.

[0141] Furthermore, the temperature monitoring module A10 is also used for:

[0142] Determine the outlet temperature difference between the current moment after the start of the pressure holding and cooling phase and the previous adjacent moment;

[0143] If the normalized outlet temperature difference is greater than the third preset threshold, the current process stage of the blow molding process cycle is determined to be the mold opening and part removal stage.

[0144] Furthermore, the parameter adjustment module A20 is also used for:

[0145] Determine the current actual inlet and outlet temperature difference after the start of the mold opening and part removal stages. If the current actual inlet and outlet temperature difference is less than the preset temperature threshold, set the preset minimum inlet and outlet temperature difference to the current set inlet and outlet temperature difference for the mold opening and part removal stages.

[0146] Furthermore, the temperature monitoring module A10 is also used for:

[0147] Determine the degree of temperature dispersion of the outlet from the start of the mold opening and part removal stage to the current time, and use the degree of temperature dispersion of the outlet to determine the possibility that the current process stage is the preparatory stage before mold closing.

[0148] If the probability of the pre-mold closing preparation stage is greater than the fourth preset threshold, the current process stage of the blow molding process cycle is determined to be the pre-mold closing preparation stage.

[0149] Furthermore, the parameter adjustment module A20 is also used for:

[0150] If the dispersion of the outlet temperature during the pre-mold closing preparation stage is less than a preset dispersion threshold, the preset maximum inlet and outlet temperature difference is set as the current set inlet and outlet temperature difference during the pre-mold closing preparation stage.

[0151] The specific implementation of the cooling device for blow molding molds of the present invention is basically the same as the embodiments of the cooling control method for blow molding molds described above, and will not be repeated here.

[0152] Furthermore, the present invention also provides a computer-readable storage medium. The computer-readable storage medium of the present invention stores a cooling control program for a blow molding die, wherein, when executed by a processor, the cooling control program for a blow molding die implements the steps of the cooling control method for a blow molding die as described above.

[0153] The method implemented when the cooling control program for blow molding molds is executed can be referred to in various embodiments of the cooling control method for blow molding molds of the present invention, and will not be repeated here.

[0154] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0155] 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.

[0156] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0157] The above description is only a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. All equivalent structural / method transformations made under the inventive concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A cooling control method for blow molding dies, characterized in that, The cooling control method for blow molding dies includes the following steps: Obtain the inlet and outlet temperatures of the cooling circuit of the blow molding die, and use the outlet temperature change information or the inlet and outlet temperature change information to determine the current process stage of the blow molding process cycle. Based on the previous set inlet and outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage, determine the current set inlet and outlet temperature difference of the current process stage. Determine the temperature difference adjustment error between the current actual inlet and outlet temperature difference and the current set inlet and outlet temperature difference, and use the PID controller to calculate the output signal in real time based on the temperature difference adjustment error to adjust the flow rate of the cooling medium in the cooling circuit. The current process stages include the mold closing and blowing stage, the pressure holding and cooling stage, the mold opening and part removal stage, and the pre-mold closing preparation stage. Among these, determining the current process stage of the blow molding process cycle using information on outlet temperature changes includes: Determine the outlet temperature difference between the current moment and the previous adjacent moment in the blow molding process cycle; If the normalized outlet temperature difference is greater than the first preset threshold, the current process stage of the blow molding process cycle is determined to be the mold closing and blowing stage. The current process stage of the blow molding cycle is determined using inlet and outlet temperature change information, including: Determine the current inlet and outlet temperature difference at the current moment after the start of the mold closing and blowing stages, and the previous inlet and outlet temperature difference at the previous adjacent moment; The probability that the current process stage is the pressure holding and cooling stage can be determined by using the current inlet and outlet temperature difference and the previous inlet and outlet temperature difference. If the probability of the holding and cooling stage is greater than the second preset threshold, the current process stage of the blow molding process cycle is determined to be the holding and cooling stage. The current process stage of the blow molding cycle is determined using information on outlet temperature changes, including: Determine the outlet temperature difference between the current moment after the start of the pressure holding and cooling phase and the previous adjacent moment; If the normalized outlet temperature difference is greater than the third preset threshold, the current process stage of the blow molding process cycle is determined to be the mold opening and part removal stage. The current process stage of the blow molding cycle is determined using information on outlet temperature changes, including: Determine the degree of temperature dispersion of the outlet from the start of the mold opening and part removal stage to the current time, and use the degree of temperature dispersion of the outlet to determine the possibility that the current process stage is the preparatory stage before mold closing. If the probability of the pre-mold closing preparation stage is greater than the fourth preset threshold, the current process stage of the blow molding process cycle is determined to be the pre-mold closing preparation stage.

2. The cooling control method for blow molding dies according to claim 1, characterized in that, Based on the previously set inlet and outlet temperature difference of the previous process stage and the temperature change characteristics of the current process stage, the current set inlet and outlet temperature difference of the current process stage is determined, including: The current set inlet and outlet temperature difference for the mold closing and blowing stages is determined by using the set inlet and outlet temperature difference during the pre-mold closing preparation stage and the outlet temperature difference between the mold closing and blowing stages.

3. The cooling control method for blow molding dies according to claim 1, characterized in that, Based on the previously set inlet and outlet temperature difference of the previous process stage, determine the current set inlet and outlet temperature difference of the current process stage, including: Determine the temperature difference between the set inlet / outlet temperature difference at the end of the mold closing and blowing stages and the standard steady-state inlet / outlet temperature difference; Determine the duration of the pressure holding and cooling phase from its start to the current moment, and use the temperature difference and the duration of the phase to determine the current set inlet and outlet temperature difference for the pressure holding and cooling phase.

4. The cooling control method for blow molding dies according to claim 1, characterized in that, Based on the temperature change characteristics of the current process stage, determine the current set inlet and outlet temperature difference for the current process stage, including: Determine the current actual inlet and outlet temperature difference after the start of the mold opening and part removal stages. If the current actual inlet and outlet temperature difference is less than the preset temperature threshold, set the preset minimum inlet and outlet temperature difference to the current set inlet and outlet temperature difference for the mold opening and part removal stages.

5. The cooling control method for blow molding dies according to claim 1, characterized in that, Based on the temperature change characteristics of the current process stage, determine the current set inlet and outlet temperature difference for the current process stage, including: If the dispersion of the outlet temperature during the pre-mold closing preparation stage is less than a preset dispersion threshold, the preset maximum inlet and outlet temperature difference is set as the current set inlet and outlet temperature difference during the pre-mold closing preparation stage.

6. A cooling device for blow molding molds, characterized in that, The apparatus is used to implement the cooling control method for blow molding dies as described in any one of claims 1 to 5; the apparatus includes: The temperature monitoring module is used to acquire the inlet and outlet temperatures of the cooling circuit of the blow molding die, and to determine the current process stage of the blow molding process cycle using the outlet temperature change information or the inlet and outlet temperature change information. The parameter adjustment module is used to determine the current set inlet and outlet temperature difference of the current process stage based on the previous set inlet and outlet temperature difference of the previous process stage and / or the temperature change characteristics of the current process stage; determine the temperature difference adjustment error between the current actual inlet and outlet temperature difference and the current set inlet and outlet temperature difference; and calculate the output signal in real time through the PID controller based on the temperature difference adjustment error to adjust the flow rate of the cooling medium in the cooling circuit. The current process stages include the mold closing and blowing stage, the pressure holding and cooling stage, the mold opening and part removal stage, and the pre-mold closing preparation stage.

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