An adaptive digital control system for a safety shoe forming process

Abstract

The application relates to the technical field of injection molding process control, and discloses a self-adaptive digital control system for a safety shoe forming process, which comprises a main controller and a metering pump group, a proportional control valve, a displacement sensor and a pressure sensor connected with the main controller. In view of the problems that the fluid impact during injection causes the metal components in the mold to be deviated and the flow control causes the raw material proportioning to be unbalanced, when the absolute value of the displacement change rate of the metal components is greater than or equal to a threshold value, the main controller controls the proportional control valve to reduce the opening degree for short-time flow reduction; during the flow reduction, the two metering pumps are respectively subjected to differentiated speed feed-forward compensation according to the pipeline pressure deviation; and the initial opening degree of the valve is restored after the flow recovery condition is met. The application prevents the metal components from being deviated through self-adaptive flow reduction, and the feed-forward compensation is used to offset the displacement deviation caused by the back pressure fluctuation, so that the proportioning balance of the two-component raw materials is maintained, and the physical performance and the production efficiency of the finished products are ensured.

Description

Technical Field

[0001] This invention relates to the field of injection molding process control technology, specifically to an adaptive digital control system for the molding process of safety shoes. Background Technology

[0002] In the manufacturing process of safety shoes, a two-component polyurethane injection molding process is widely used. Before injection molding, metal components such as the anti-impact steel toe cap are usually pre-positioned in the mold cavity. After injection molding begins, the fluid formed by mixing the two-component raw materials is injected into the mold. During this process, the fluid front edge contacts and impacts the pre-positioned metal components. Because the set flow rate is usually high, the impact force generated by the fluid can easily cause the metal components to deviate from their initial position, resulting in the structural dimensions of the finished product exceeding standard tolerances and producing scrap.

[0003] To mitigate the risk of displacement due to fluid impact, a common process adjustment method is to reduce the flow rate setpoint throughout the injection molding process. This increases the molding cycle time for individual products, leading to a decrease in the overall processing efficiency of the production line. Some process improvements attempt to slow down the flow rate midway through injection by controlling valves. However, in a two-component feeding system, changing the valve opening can cause fluctuations in the fluid pressure in the upstream pipeline. Because the two components used in polyurethane foam have different physical properties, their volumetric compression response to pressure changes differs. When pipeline pressure changes, this difference in physical properties causes deviations in the actual output displacement of the two-component metering pumps, thereby disrupting the original material mixing ratio. Imbalance in the two-component raw material ratio directly affects the subsequent cross-linking and foaming reaction of the polyurethane, resulting in quality defects such as localized density abnormalities or substandard mechanical strength in the molded shoe sole. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an adaptive digital control system for the molding process of safety shoes. This system solves the problem that in the two-component injection molding process of safety shoes, the fluid injected into the mold will impact the pre-placed metal components inside the mold, causing the metal components to shift. Although constant low flow rate injection can reduce the impact, it will also reduce production efficiency.

[0005] To address the above problems, the present invention provides the following technical solution: The first aspect of the present invention provides an adaptive digital control system for a safety shoe molding process, including a main controller, and a metering pump group, a proportional control valve, a displacement sensor and a pressure sensor respectively communicatively connected to the main controller; the metering pump group includes a first metering pump for conveying a first component raw material and a second metering pump for conveying a second component raw material, and the proportional control valve is disposed on a pipeline downstream of the metering pump group; The main controller is configured to perform the following operations: After injection molding starts, the real-time displacement signal of the metal component inside the mold collected by the displacement sensor is acquired, and the displacement change rate of the metal component is calculated. When the displacement change rate is greater than the preset displacement change rate threshold, a flow reduction control signal is output to the proportional control valve to reduce the valve opening and enter the flow reduction control stage to reduce the impact force of the fluid on the metal component. During the flow reduction control phase, the pressure signal of the upstream pipeline of the proportional control valve collected by the pressure sensor is acquired to calculate the pressure deviation, and the first metering pump and the second metering pump are subjected to speed feedforward compensation control according to the pressure deviation. When the system status is detected to meet the preset flow recovery conditions, a recovery control signal is output to the proportional control valve to restore it to the initial valve opening at the start of injection molding.

[0006] This invention uses displacement sensors to monitor the displacement changes of metal components within the mold in real time. When fluid impact causes abnormal displacement, a flow reduction operation is performed, avoiding efficiency losses caused by low-speed injection molding throughout the process. Simultaneously, to address pipeline back pressure fluctuations caused by valve throttling, the system introduces a pressure deviation feedforward compensation mechanism. This mechanism synchronously and differentially adjusts the rotation speed of different component metering pumps based on pressure changes to offset displacement deviations caused by pressure fluctuations and maintain the balanced ratio of the two-component raw materials.

[0007] The pressure response characteristics refer to the comprehensive response characteristics of the first component raw material, the second component raw material, and their corresponding metering pumps and feeding channels on the actual output displacement under pipeline pressure changes. The pressure response characteristics may include the difference in volumetric compressibility between the first and second component raw materials, the pressure-actual displacement response relationship at different pressure operating points, and the response characteristics of the volumetric efficiency of the first and second metering pumps as back pressure changes.

[0008] In a specific implementation, the actual output displacement of each component feeding channel at different pressure operating points can be pre-calibrated, and the first pressure-speed compensation coefficient and the second pressure-speed compensation coefficient can be determined accordingly. This enables the main controller to perform differentiated speed feedforward compensation for the first metering pump and the second metering pump based on the pressure deviation.

[0009] Furthermore, the system also includes an ultrasonic sensor that is communicatively connected to the main controller. The ultrasonic sensor is coaxially disposed with the displacement sensor on the non-forming side of the mold and is used to emit ultrasonic waves into the inner cavity of the mold and receive the reflected echo energy signal.

[0010] Furthermore, the main controller is also configured to perform a reference calibration operation before executing the injection molding start: After the mold is closed and before the raw material is injected, the initial distance data collected by the displacement sensor is acquired and stored as the equivalent displacement zero-position reference of the metal component.

[0011] Furthermore, the specific logic for the main controller to output a current reduction control signal to the proportional control valve is as follows: The current reduction control voltage is calculated based on the preset initial driving voltage, displacement change rate threshold and proportional gain coefficient. The current reduction control voltage is equal to the initial drive voltage minus the voltage adjustment amount; Wherein, the voltage regulation amount is equal to the difference between the absolute value of the displacement change rate in the current cycle and the displacement change rate threshold, multiplied by the proportional gain coefficient; The main controller sends the current reduction control voltage as the current reduction control signal to the proportional control valve.

[0012] Furthermore, the specific logic of the main controller performing speed feedforward compensation control on the first metering pump and the second metering pump based on the pressure deviation includes: The difference between the current pipeline pressure and the steady-state reference pressure upstream of the proportional control valve is calculated as the pressure deviation. A first pressure-speed compensation coefficient corresponding to the first component raw material and a second pressure-speed compensation coefficient corresponding to the second component raw material are preset; the values ​​of the first pressure-speed compensation coefficient and the second pressure-speed compensation coefficient are not equal, and their ratio is determined based on the difference in volume compressibility between the first component raw material and the second component raw material. The pressure deviation is multiplied by the first pressure-speed compensation coefficient and the second pressure-speed compensation coefficient respectively to calculate the first speed compensation amount and the second speed compensation amount. The first speed compensation amount is added to the current target speed of the first metering pump, and the second speed compensation amount is added to the current target speed of the second metering pump.

[0013] Furthermore, the preset traffic recovery conditions set in the main controller include a first condition and a second condition that must be met simultaneously: The first condition is: the displacement change rate continues to decrease and is less than a preset displacement change rate noise threshold; The second condition is: the ultrasonic echo attenuation rate calculated based on the ultrasonic echo reference and real-time echo energy integral value corresponding to the target detection area is greater than or equal to the preset ultrasonic echo attenuation threshold, which is used to determine that the fluid has covered the metal component and formed a buffer protective layer.

[0014] Furthermore, the ultrasonic echo attenuation rate is calculated as follows: during the benchmark calibration process before injection molding starts, the initial echo energy integral value is obtained when the mold is a cavity; during the injection molding process, the real-time echo energy integral value of the current cycle is obtained; the ultrasonic echo attenuation rate is equal to the difference between the initial echo energy integral value and the real-time echo energy integral value, divided by the initial echo energy integral value.

[0015] Furthermore, the main controller outputs a recovery control signal to the proportional control valve in the following manner: using a preset voltage recovery slope parameter, the control voltage of the proportional control valve is linearly increased from the current voltage value in the current reduction control stage over time until it is restored to the initial drive voltage corresponding to the initial valve opening at the start of injection molding.

[0016] Furthermore, the main controller is also configured to perform volumetric closed-loop termination control during the injection molding process: According to a fixed sampling control cycle, the actual feedback speed of the first metering pump and the actual feedback speed of the second metering pump are acquired in real time. By combining the equivalent single-cycle displacement parameters of the first metering pump and the equivalent single-cycle displacement parameters of the second metering pump, the volume of fluid injected in each sampling control cycle is integrated and accumulated to obtain the cumulative injection volume; When the cumulative injection volume is greater than or equal to the set target injection volume, a shut-off signal is output to the proportional control valve, and the metering pump group is controlled to stop.

[0017] Furthermore, the metal component is a steel toe cap pre-placed at the toe position of the mold, the displacement sensor is a non-contact electromagnetic eddy current displacement sensor; the first component raw material is isocyanate, the second component raw material is polyol, and the injection molding is a two-component polyurethane continuous injection molding.

[0018] A second aspect of the present invention provides an adaptive digital control method for a safety shoe molding process, applied to the digital control system described in the first aspect above, the control method comprising the following steps: After injection molding starts, the real-time displacement signal of the metal components inside the mold is acquired and the displacement change rate is calculated. When the displacement change rate is greater than the preset displacement change rate threshold, a flow reduction control signal is output to the proportional control valve to reduce the valve opening and enter the flow reduction control stage. During the flow reduction control phase, the pressure signal from the upstream pipeline is acquired to calculate the pressure deviation, and the first metering pump and the second metering pump are controlled by speed feedforward compensation based on the pressure deviation. When the system status meets the preset flow recovery conditions, a recovery control signal is output to the proportional control valve to restore it to the initial valve opening at the start of injection molding.

[0019] This invention provides an adaptive digital control system for the molding process of safety shoes. It has the following beneficial effects: 1. This invention uses a displacement sensor to monitor the displacement rate of metal components within the mold in real time, and outputs a flow reduction control signal to the proportional control valve when the displacement exceeds a preset threshold, thereby temporarily reducing the valve opening. This control method can reduce the flow rate to prevent metal component misalignment when there is a risk of fluid impact, thus maintaining the original flow rate in the absence of impact risk, thereby ensuring normal production efficiency while guaranteeing product molding quality.

[0020] 2. This invention introduces a pressure deviation feedforward compensation mechanism in the flow reduction control stage. The pressure deviation is calculated based on the pipeline pressure signal, and differentiated speed compensation is applied to the first and second metering pumps based on the differences in the compressibility characteristics of the two component raw materials. This method offsets the impact of pipeline back pressure fluctuations caused by the proportional control valve's throttling on the actual fluid discharge, maintaining the mixing ratio balance of the two component raw materials, thereby ensuring the physical properties of the finished polyurethane product.

[0021] 3. This invention combines the ultrasonic echo attenuation rate and displacement change rate as flow recovery conditions, and uses an ultrasonic sensor to detect whether the fluid inside the mold has covered the metal component. This design can control the proportional control valve to return to its initial opening only after confirming that a fluid buffer protective layer has formed outside the metal component, preventing secondary fluid impact caused by premature restoration of the original flow rate, and improving the stability of injection molding process control. Attached Figure Description

[0022] Figure 1 This is a structural diagram of the control system according to an embodiment of the present invention; Figure 2 This is a flowchart of the adaptive digital control method according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the initial state calibration principle of an embodiment of the present invention; Figure 4 This is a timing diagram of dual-parameter parallel high-frequency sampling according to an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the transient current reduction control principle of an embodiment of the present invention; Figure 6 This is a schematic diagram of the feedforward compensation control principle according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the adaptive flow recovery control principle according to an embodiment of the present invention; Figure 8 This is a timing diagram of closed-loop termination and pressure holding curing control in an embodiment of the present invention; Figure 9 The following is a scene anti-collision response action diagram according to an embodiment of the present invention; wherein, (a) is a diagram for monitoring the dynamic displacement trend of the steel head; and (b) is a diagram for the adaptive flow reduction control response of the proportional control valve. Figure 10 This is a diagram of the rotational speed compensation action in the experimental group of this invention; Figure 11 This is a box plot comparing the finished product quality of the experimental and control groups in this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] See attached document Figure 1 The present invention provides an adaptive digital control system for the molding process of safety shoes. The control system includes a main controller, a communication bus, a proportional control valve, a metering pump group, a mixing head, and a sensor array.

[0025] The main controller establishes communication connections with the proportional control valve and the metering pump group via the communication bus. The main controller sends control commands to the proportional control valve and the metering pump group via the communication bus, and receives operating status data fed back by the proportional control valve and the metering pump group.

[0026] The metering pump set includes a first metering pump and a second metering pump. Therefore, in this specification, the A-component pump can be considered a specific embodiment of the first metering pump, and the B-component pump can be considered a specific embodiment of the second metering pump; correspondingly, component A corresponds to the first component raw material, and component B corresponds to the second component raw material. In this embodiment, the first metering pump is the A-component pump, used to transport the first component raw material, i.e., component A raw material; the second metering pump is the B-component pump, used to transport the second component raw material, i.e., component B raw material. The output ends of the A-component pump and the B-component pump are respectively connected to a mixing head, allowing the A-component raw material and the B-component raw material to enter the mixing head for mixing and output.

[0027] A pressure detection assembly is installed inside the mixing head. The pressure detection assembly includes a first pressure transmitter and a second pressure transmitter. Both the first and second pressure transmitters can be specific implementations of pressure sensors; wherein, the pressure sensor used to collect the pressure signal of the upstream pipeline of the proportional control valve can be the first pressure transmitter.

[0028] The first pressure transmitter is located upstream of the proportional control valve and is connected to the internal flow channel of the mixing head. The first pressure transmitter is used to detect pressure fluctuations transmitted upstream during the throttling process of the proportional control valve.

[0029] The second pressure transmitter is located downstream of the proportional control valve; alternatively, it is located in a pressure-holding channel that remains pressure-connected to the mold cavity even after the proportional control valve is closed. The second pressure transmitter is used to detect static pressure changes during the mold-closing, pressure-holding, and curing monitoring stage.

[0030] The signal output terminals of both the first and second pressure transmitters are connected to the main controller via a communication bus.

[0031] The proportional control valve is located at the injection outlet of the mixing head and is used to regulate the flow rate of the mixed fluid into the mold cavity.

[0032] The control system works in conjunction with the mold. The mold has an inner cavity for containing fluid, and the metal component to be covered is placed in the inner cavity.

[0033] A sensor array is embedded in the non-molded side of the mold. The sensor array includes multiple sensor units distributed at preset intervals. Each sensor unit includes an eddy current coil for non-contact electromagnetic eddy current displacement detection and a piezoelectric wafer for ultrasonic wave transmission and echo reception. The eddy current coil and its corresponding excitation, impedance detection, and signal conversion circuits together constitute the detection channel of the displacement sensor; the piezoelectric wafer and its corresponding excitation and echo receiving circuits together constitute the detection channel of the ultrasonic sensor. The eddy current coil and the piezoelectric wafer are coaxially arranged.

[0034] Specifically, the eddy current coils are arranged in a ring, with a piezoelectric wafer positioned in the center of the eddy current coils, and the eddy current coils surrounding the piezoelectric wafer. This arrangement allows the same sensor unit to acquire eddy current detection signals related to the position of the metal component and ultrasonic echo signals related to the state of the internal cavity medium within adjacent detection areas.

[0035] The arrangement of the sensor array on the mold is determined based on the pre-positioning area of ​​the metal component within the mold cavity. In the embodiment where the metal component is a steel head for impact protection, at least some sensor units are positioned corresponding to the pre-positioning area of ​​the steel head, thus establishing a predetermined spatial correspondence between the effective detection area of ​​the corresponding sensor unit and the area where the steel head is located, its adjacent area, or the characteristic area where the medium state changes after the fluid front reaches the steel head.

[0036] The spatial correspondence can be predetermined during mold design or sensor array installation, based on the pre-positioned coordinates of the anti-smashing steel head, the mold cavity structure, and the expected fluid filling path, and stored in the main controller. The main controller then determines the mold cavity region corresponding to the detection results of each sensor unit.

[0037] The sensor array has a detection end face on the side facing the inner cavity. A non-ferromagnetic metal substrate of a predetermined thickness is maintained between the detection end face and the inner cavity. The non-ferromagnetic metal substrate forms part of the mold, so that the sensor array is not directly exposed to the inner cavity, nor is the molded surface of the inner cavity damaged.

[0038] The material and thickness of the non-ferromagnetic metal substrate are determined based on the alternating excitation frequency of the eddy current coil, the ultrasonic center frequency of the piezoelectric wafer, and the structural strength requirements of the mold. This configuration allows the alternating magnetic field generated by the eddy current coil to be coupled to the surface of the metal component via the non-ferromagnetic metal substrate, and enables the piezoelectric wafer to receive ultrasonic echoes from the interface between the mold substrate and the inner cavity medium.

[0039] The sensor array is disposed on the non-molding side of the mold. In this embodiment, the sensor array is specifically embedded in the non-molding side substrate of the mold, thereby forming a non-penetrating embedded sensing structure. "Disposed on the non-molding side of the mold" includes embodiments in which the sensor is disposed on the surface of the non-molding side, in a mounting groove, or embedded in the non-molding side substrate, as long as the sensor can perform displacement detection and ultrasonic detection through the mold substrate toward the corresponding detection area of ​​the inner cavity. The signal output terminals of the sensor array are connected to the high-speed sampling interface of the main controller to input the eddy current detection signals and ultrasonic echo signals collected by each sensor unit into the main controller.

[0040] See attached document Figure 2 The present invention provides an adaptive digital control method for the molding process of safety shoes. The method can be executed by the aforementioned control system and includes the following steps.

[0041] S10, before the mold is closed and the mixing head performs the injection action, the main controller performs pre-injection reference calibration on the sensor array.

[0042] Pre-injection calibration should include at least obtaining the overall eddy current displacement zero-point reference. And obtain the zero-position reference of the unit eddy current displacement when including multiple sensor units. And to obtain the overall ultrasound echo reference And acquire the ultrasonic echo reference of each unit when including multiple sensor units. .

[0043] S20, after the injection action is started, the main controller controls the proportional control valve to open at the initial set opening degree to form the initial set flow rate; at the same time, the main controller controls the metering pump group to output component A raw material and component B raw material at the initial target speed.

[0044] During the process of filling the mold cavity with the mixed fluid, the main controller performs synchronous sampling of displacement signals and ultrasonic echo signals. The displacement signal is used to reflect the change in distance between the metal component and the sensor array, while the ultrasonic echo signal is used to reflect the change in the state of the medium inside the cavity.

[0045] S30, the main controller calculates the displacement rate of the metal component during the injection process. and the rate of change of displacement The absolute value and the threshold of the rate of change of displacement Compare them.

[0046] When the rate of change of displacement When the absolute value of the current reaches the preset judgment condition, the main controller outputs a current reduction control voltage to the proportional control valve, thereby reducing the opening of the proportional control valve and performing short-term current reduction control.

[0047] S40, the main controller reads the upstream pressure fluctuation data fed back by the first pressure transmitter within the same control cycle or adjacent control cycles of the output current reduction control voltage.

[0048] Pressure fluctuation data and flow reduction control actions have corresponding time stamps. Based on this pressure fluctuation data, the main controller outputs a speed feedforward compensation command to the metering pump group to correct the target speeds of component pumps A and B respectively, in order to compensate for the different effects of back pressure fluctuations on the actual output displacement of component pumps A and B.

[0049] S50, while the proportional control valve maintains the reduced flow state, the main controller continuously acquires the displacement change rate. and ultrasonic echo attenuation rate .

[0050] When the displacement stability condition is met, and the ultrasonic echo attenuation rate is... When the fluid coverage condition is met, the main controller controls the proportional control valve to gradually restore the flow rate from the reduced flow state to the initial set flow rate.

[0051] The displacement stability condition is used to characterize that the metal component does not exhibit a continuous displacement trend; the fluid coverage determination condition is used to characterize that the fluid has covered the detection area corresponding to the sensor array.

[0052] The flow recovery condition is used to characterize that the risk of fluid shock that would cause the metal component to continue to shift position has been reduced. In one embodiment, the satisfaction of the flow recovery condition can be determined at least based on the displacement change state of the metal component; in embodiments where it is necessary to further improve the reliability of the recovery timing judgment, a joint judgment can be made by combining detection information that reflects the fluid arrival state or coverage state, in addition to the displacement stabilization condition being met.

[0053] This embodiment uses the simultaneous satisfaction of displacement stability condition and ultrasonic echo coverage judgment condition to determine the timing of flow recovery. Thus, after confirming that the metal component does not show a continuous displacement trend and that the fluid has reached the corresponding detection area, the flow recovery control of the proportional control valve is executed.

[0054] S60, when the cumulative injection volume of the metering pump group reaches the target set value, the main controller closes the proportional control valve and controls the metering pump group to stop output.

[0055] Subsequently, the control system enters the mold closing pressure holding and curing monitoring stage, where the main controller monitors the relevant pressure status of the mold cavity until the subsequent mold opening conditions are met.

[0056] See attached document Figure 3 During the pre-injection calibration process, the main controller outputs an alternating excitation current of a set frequency to the eddy current coils in the sensor array. The set frequency is determined based on the material conductivity, relative permeability, and preset wall thickness of the non-ferromagnetic metal matrix of the mold.

[0057] An alternating excitation current generates an alternating magnetic field around the eddy current coil. The set frequency can be selected in the range of several kilohertz to tens of kilohertz, so that the alternating magnetic field can still couple to the surface of the metal component after being attenuated by the non-ferromagnetic metal substrate.

[0058] When determining the specific excitation frequency, the candidate excitation frequency range can be determined first based on the non-ferromagnetic metal material used in the mold detection area and the actual detection wall thickness. Then, after the sensor array is assembled, the detection effectiveness can be verified using standard metal parts.

[0059] Specifically, a standard metal component with the same or similar electromagnetic response characteristics as the metal component under test is placed at multiple known distances, and the output signal of the eddy current detection channel is recorded under different candidate excitation frequencies. Based on the monotonicity, sensitivity, and repeatability of the output signal as a function of the standard distance, the actual operating frequency is determined from the candidate excitation frequency range.

[0060] After determining the operating frequency, the standard metal component is positioned at multiple known distances, and the detection voltage or equivalent impedance response corresponding to each distance is recorded to establish a calibration relationship between the detection output and the equivalent physical distance. This calibration relationship can be stored in the main controller in the form of a calibration curve, piecewise function, lookup table, or fitting function.

[0061] Before the actual injection control begins, the main controller uses the calibration relationship to convert the output signal of the eddy current detection channel into the equivalent physical distance between the metal component and the sensor detection end face.

[0062] When an alternating magnetic field is applied to the surface of a metal component, it induces closed eddy currents on the surface. These eddy currents generate a secondary magnetic field, which acts in the opposite direction on the eddy current coil, causing a change in the equivalent impedance of the eddy current coil. The change in the equivalent impedance of the eddy current coil varies depending on the distance between the metal component and the eddy current coil; generally, the closer the two are, the stronger the induced eddy current, and the greater the corresponding change in equivalent impedance.

[0063] The detection circuit within the main controller detects the change in the equivalent impedance of the eddy current coil and converts this impedance change into a corresponding DC voltage signal. The main controller, in conjunction with a pre-established eddy current displacement calibration relationship, compensates for the background response and signal attenuation caused by the non-ferromagnetic metal substrate.

[0064] At this stage, the mold is in a closed state, and the metal component is in a pre-positioned state. The main controller continuously samples the DC voltage signal for a preset number of sampling periods and calculates the arithmetic mean of the sampled values. Subsequently, based on the eddy current displacement calibration relationship of the partition wall, the main controller converts this average value into the equivalent physical distance from the surface of the metal component to the end face of the eddy current coil, and stores this equivalent physical distance as the overall eddy current displacement zero-position reference. .

[0065] When the sensor array includes multiple sensor units, the main controller performs the above-mentioned eddy current calibration process on each sensor unit, and acquires and stores the zero-position reference of the unit eddy current displacement of each sensor unit. To form an array of eddy current zero-position reference tables.

[0066] The eddy current displacement calibration relationship can be established after the system assembly is completed. During the establishment, multiple known distances can be formed between the metal component or equivalent standard component and the eddy current coil using standard metal parts or standard gap blocks, and the voltage value output by the detection circuit at each known distance can be recorded, thereby obtaining the correspondence between the voltage value and the equivalent physical distance.

[0067] The impedance-to-voltage conversion and detection circuit corresponding to the eddy current coil can be implemented using existing eddy current displacement detection circuits. This part of the circuit is used to output a voltage signal corresponding to the change in the coil's equivalent impedance, and its specific circuit form can be selected according to the number of channels in the sensor array, the sampling frequency, and the anti-interference requirements.

[0068] Complete the overall eddy current displacement zero-position reference and the zero-position reference of the unit eddy current displacement After acquiring the data, the main controller outputs excitation pulses to the piezoelectric crystal in the sensor array. The piezoelectric crystal is bonded and fixed to the non-ferromagnetic metal substrate of the mold through a temperature-resistant acoustic coupling layer, and an electrically insulating layer is set on the electrode side of the piezoelectric crystal to allow the ultrasonic pulses generated by the piezoelectric crystal to couple into the substrate of the mold while avoiding electrical short circuit between the excitation pulse and the mold.

[0069] The piezoelectric crystal generates mechanical vibration under the action of an excitation pulse and emits ultrasonic detection pulses into the mold. The center frequency of the ultrasonic detection pulse can be selected in the megahertz range to meet the echo detection resolution requirements in the mold wall thickness direction. The ultrasonic detection pulse propagates within the non-ferromagnetic metal matrix of the mold and reaches the interface between the non-ferromagnetic metal matrix and the medium inside the cavity.

[0070] Before the injection process, the inner cavity contains air. There is a significant difference in acoustic impedance between the non-ferromagnetic metal substrate of the mold and the air medium. When the ultrasonic detection pulse reaches this interface, most of the energy is reflected at the solid-gas interface.

[0071] The reflected ultrasonic echo returns to the piezoelectric crystal. The piezoelectric crystal receives the ultrasonic echo and converts it into an echo voltage signal. The main controller acquires this echo voltage signal and calculates the overall ultrasonic echo reference when the cavity is in an air-medium state by integrating the echo energy. .

[0072] The calculation formula is as follows: ; In the formula, As the overall ultrasonic echo reference; The reflected echo voltage signal received by the piezoelectric crystal during the integration time The instantaneous value at that point; and These are the start and end times of the ultrasonic echo signal receiving window set by the main 0.

[0073] Among them, the start time of the ultrasonic echo signal receiving window Configured to avoid the ringing interference zone of the piezoelectric crystal's initial excitation pulse, the termination time... The main attenuation range of the first reflected echo from the solid-gas interface; and It can be determined based on the longitudinal wave velocity of the ultrasonic wave in the non-ferromagnetic metal matrix of the mold, and the actual wall thickness from the location of the piezoelectric wafer to the interface.

[0074] The main controller will calculate the overall ultrasonic echo reference. It is stored in an internal register and serves as a reference for determining the state of the fluid interface during subsequent injection processes.

[0075] When the sensor array includes multiple sensor units, the main controller performs the aforementioned ultrasonic calibration process on the piezoelectric wafer in each sensor unit, and acquires and stores the unit ultrasonic echo reference corresponding to each sensor unit. To form an array of ultrasonic echo reference tables.

[0076] See attached document Figure 4 During continuous injection, the main controller maintains the eddy current coil in an alternating excitation state and demodulates the equivalent impedance signal fed back by the eddy current coil through a detection circuit. The main controller operates according to a preset control cycle. The equivalent impedance signal is read cyclically, and the equivalent physical distance at the current moment is calculated based on the aforementioned eddy current displacement calibration relationship of the partition wall.

[0077] When the sensor array includes multiple sensor units, the main controller reads the feedback signal of the eddy current coil corresponding to each sensor unit and maps it to obtain the equivalent physical distance of each sensor unit. The main controller is based on the equivalent physical distance of multiple units. The current equivalent physical distance is determined by the maximum change value, the average value, or the fused value after outlier removal. .

[0078] The main controller can also adjust the current equivalent physical distance. With the overall eddy displacement zero reference The difference between them is used to calculate the relative displacement of the metal components. When the sensor array includes multiple sensor units, the main controller can calculate the relative displacement of the metal components based on the equivalent physical distance between each sensor unit. With the corresponding element eddy current displacement zero reference The difference between them is used to calculate the relative displacement at each detection position.

[0079] The fusion method for multiple sensor units can be preset within the same molding batch or mold specification and kept consistent during the injection process to avoid unstable control judgment caused by switching between different fusion rules.

[0080] In the initial stage of fluid entry into the internal cavity, the metal components may experience positional changes due to fluid impact. This positional change may initially manifest as a small displacement, but the distance change per unit time is significant. To promptly identify this trend, the main controller determines the current equivalent physical distance based on the current control cycle. Equivalent physical distance from the previous control cycle Calculate the overall displacement change rate of the metal component. The calculation formula is as follows: ; In the formula, This represents the transient global displacement rate of change at the current moment; This represents the equivalent physical distance obtained from electromagnetic sampling at the current moment. This is the equivalent physical distance from the previous control cycle; It is a fixed control cycle.

[0081] When the sensor array includes multiple sensor units, the main controller can calculate the displacement change rate of each sensor unit separately. and the displacement change rate of multiple units The maximum absolute value, average value, or the result after filtering and fusion is taken as the overall displacement change rate. Participate in subsequent control and determination.

[0082] Control cycle It can be configured to milliseconds. For example, The value can be selected from 1ms to 5ms. This value is used to balance capturing the position change trend and suppressing high-frequency noise in differential calculation.

[0083] The main controller acquires the overall displacement change rate. Within the same control cycle or adjacent control cycles, the piezoelectric crystal is driven to emit ultrasonic detection pulses by means of the clock synchronization function of the communication bus, and the reflected echo voltage signal received by the piezoelectric crystal is collected.

[0084] During the period when the piezoelectric crystal emits ultrasonic detection pulses, the main controller can perform short-term shielding, sample-and-hold, or digital filtering on the sampling channel of the eddy current coil to reduce the interference of the excitation pulse on the eddy current detection signal.

[0085] The main controller performs echo energy integration on the reflected echo voltage signal to obtain the comprehensive ultrasound reflected echo energy corresponding to the current injection time t. The calculation formula is as follows: Control cycle Typically configured in millisecond increments, for example, within the range of 1ms to 5ms. This value needs to strike a balance between capturing transient dynamic changes and suppressing differential high-frequency noise. The calculation formula is as follows: ; In the formula, For the current macro injection moment The combined ultrasonic reflected echo energy; This represents the instantaneous value of the reflected echo voltage signal within the receiving window; For the microscopic integral time variable within the receiving window; and These are the start and end times of the ultrasonic echo signal receiving window set by the main controller. Start time and the end time The basis for setting and the physical meaning are consistent with the initial state calibration process.

[0086] When the sensor array includes multiple sensor units, the main controller acquires the reflected echo voltage signal received by the piezoelectric crystal in each sensor unit, and calculates the ultrasonic reflected echo energy of each sensor unit. .

[0087] In one basic implementation, the flow recovery condition may include at least a displacement stability condition determined based on the displacement change rate. Specifically, when the absolute value of the displacement change rate of the metal component is less than or equal to a preset displacement change rate noise threshold for a continuous preset time period, the main controller determines that the metal component does not exhibit a continuous displacement trend and determines that the flow recovery condition is met.

[0088] In a further embodiment, the flow recovery condition can also be determined by combining the cumulative displacement of the metal component, the pressure fluctuation state upstream of the proportional control valve, or the preset waiting time, so as to avoid premature flow recovery due to instantaneous noise.

[0089] In a preferred embodiment equipped with an ultrasonic sensor, the flow recovery condition may further include a fluid coverage determination condition, that is, on the basis that the displacement stability condition is met, it is also determined whether the ultrasonic echo attenuation rate reaches a preset ultrasonic echo attenuation threshold, so as to confirm that the fluid has covered the metal component and formed a buffer protective layer.

[0090] The main controller will have the overall displacement change rate corresponding to the time stamp. and combined ultrasonic reflected echo energy The data is stored in an internal buffer queue to form a displacement-ultrasonic sampling data set for subsequent flow reduction control and flow recovery control.

[0091] When the sensor array includes multiple sensor units, the main controller will control the displacement rate of each sensor unit. and unit ultrasonic reflected echo energy The data is stored according to the sensor unit number and time stamp to form an array displacement-ultrasonic sampling data group.

[0092] Based on the current equivalent physical distance or overall displacement change rate During processing, the main controller can employ moving average filtering, low-pass filtering, or amplitude limiting filtering to reduce environmental electromagnetic interference and the amplifying effect of differential calculation on noise. When the filtered data is used for subsequent threshold comparisons, it should correspond to the unfiltered data using the same time stamp or the time stamp of an adjacent control cycle.

[0093] See attached document Figure 5 The main controller reads the pre-stored displacement change rate threshold. Displacement change rate threshold Based on the mass of the metal component, the assembly tolerance of the mold cavity, and the dynamic viscosity of the input fluid, this setting is used to limit the range of allowable displacement change rates of the metal component under injection impact.

[0094] In this embodiment, the proportional control valve is a voltage-controlled proportional valve, and the current-reducing control signal output by the main controller to the proportional control valve is specifically a current-reducing control voltage. It is understood that in other embodiments, the current-reducing control signal may also be a current control signal, a digital opening control command, or other control signals capable of adjusting the opening of the proportional control valve.

[0095] The main controller will calculate the overall displacement change rate in real time during each control cycle. absolute value With the threshold of displacement change rate Compare them.

[0096] when Less than At this time, the main controller determines that there is no displacement change trend that requires flow reduction in the current injection process, and maintains the initial set opening of the proportional control valve.

[0097] when Greater than or equal to At that time, the main controller determines that the metal component has a tendency to deviate from the reference position and triggers short-term current reduction control.

[0098] During short-time current reduction control, the main controller generates a current reduction control voltage output to the proportional control valve drive circuit based on the difference between the displacement change rate and the threshold value. Current reduction control voltage It can be calculated using the following formula: ; In the formula, The current reduction control voltage issued to the proportional control valve during the current control cycle; The initial drive voltage is used to maintain the initial set flow rate of the proportional control valve. The preset proportional gain coefficient, This represents the excess value of the displacement change rate.

[0099] The above calculation formula is in Greater than or equal to Execute at time; when Less than At this time, the main controller maintains the initial drive voltage. Proportional gain coefficient This can be achieved through trial molding and calibration, enabling the proportional control valve's opening change to reduce injection flow while avoiding pressure fluctuations caused by excessively rapid opening changes.

[0100] According to the above calculation formula, the larger the difference in the rate of displacement change, the greater the current reduction control voltage. Relative to the initial drive voltage The greater the reduction in the value, the smaller the opening of the proportional control valve will be.

[0101] To avoid reducing the current control voltage The voltage is too low, causing the proportional control valve to suddenly close, and the main controller to reduce the current control voltage. Perform lower limit processing. When the calculated current reduction control voltage... Below the minimum holding voltage At that time, the main controller limits the actual control voltage output to the proportional control valve to . .

[0102] Minimum holding voltage The minimum holding opening of the proportional control valve. This minimum holding opening is used to maintain the basic flow state from the mixing head to the inner cavity, and to avoid pressure surges in the pipeline caused by the proportional control valve closing rapidly.

[0103] The proportional control valve receives the reduced current control voltage output from the main controller. Subsequently, the valve core moves with the change in driving voltage, reducing the flow cross-sectional area of ​​the proportional control valve. After the flow cross-sectional area of ​​the proportional control valve decreases, the flow rate and velocity of the fluid output from the mixing head to the inner cavity decrease.

[0104] As a result, the fluid entering the inner cavity changes from an initial high flow rate injection state to a low flow rate injection state, thereby reducing the local impact pressure of the fluid front end acting on the surface of the metal component and limiting the metal component from continuing to shift position.

[0105] See attached document Figure 6 When the proportional control valve reduces the flow cross-sectional area according to the aforementioned control process, the local flow resistance at the injection outlet of the mixing head increases, causing a back pressure fluctuation to form upstream of the proportional control valve. This back pressure fluctuation affects the output terminals of the A-component pump and the B-component pump.

[0106] Because the bulk modulus of raw materials A and B differs, and the volumetric efficiency of the A and B pumps is differently sensitive to changes in back pressure, the actual output displacement of the A and B pumps may decrease to varying degrees when the back pressure increases. Without compensation, the mixing ratio of raw materials A and B will deviate from the set ratio.

[0107] Therefore, the A-component pump and the B-component pump employ independent pressure-speed compensation coefficients. These compensation coefficients are initially set based on the difference in volumetric compressibility between the A-component and B-component raw materials, and further corrected by incorporating the actual pressure-displacement response calibration results of the corresponding metering pumps and feeding channels under different pressure conditions. This ensures that the relative magnitudes of the two compensation coefficients correspond to the different sensitivities of the two component feeding systems to pressure changes.

[0108] For example, when a certain component raw material produces a larger equivalent compression under the same pressure increment, or when the actual output displacement of its corresponding metering pump decreases more as the back pressure increases, a larger pressure-speed compensation coefficient can be set for the corresponding metering pump so that it can obtain a larger speed compensation under the same pressure deviation.

[0109] The main controller reads the upstream pressure value of the proportional control valve fed back by the first pressure transmitter via the communication bus. And combined with the system steady-state reference pressure Calculate the pressure deviation at the current moment. : ; Among them, the system steady-state reference pressure The average value is obtained by sampling the internal pressure of the mixing head on the upstream side of the proportional control valve during a preset time period before the main controller triggers the short-term flow reduction control.

[0110] To avoid frequent speed corrections of the metering pump caused by the inherent noise of the pressure sensor, the main controller is set with a pressure dead zone threshold. .when Less than At that time, the main controller will display the current pressure deviation. Set to zero; when Greater than or equal to At that time, the main controller uses the pressure deviation for subsequent speed compensation calculations.

[0111] During the short-term flow reduction control of the proportional control valve, the main controller first corrects the basic target speed of the metering pump group according to the flow reduction target of the proportional control valve, so that the basic output flow of the metering pump group is adapted to the current opening of the proportional control valve.

[0112] Based on this, the main controller determines the pressure deviation. Generate a speed feedforward compensation command for the metering pump set. This speed feedforward compensation command is used to correct the different effects of back pressure fluctuations on the volumetric efficiency of component A and component B pumps, in order to maintain the mixing ratio of component A and component B raw materials; this compensation command is not used to restore the total output flow rate to the flow rate before the flow reduction.

[0113] The main controller has pre-stored pressure-speed compensation coefficients corresponding to component pump A and component pump B, respectively. , .

[0114] The pressure-speed compensation coefficients of the A-component pump and the B-component pump can be obtained through pre-calibration. In one calibration implementation, the feed channels corresponding to the A-component and B-component raw materials are operated at multiple preset pressure operating points, and the actual output displacement corresponding to each pressure operating point is recorded under the same or corresponding target speed conditions. Using the steady-state reference pressure before short-term flow reduction control as a benchmark, the pressure deviation at each pressure operating point is calculated, and the speed correction required to compensate for the actual output displacement deviation is determined, thereby establishing the correspondence between the pressure deviation and the speed correction.

[0115] When using linear feedforward compensation, the calibration data between pressure deviation and speed correction can be linearly fitted, and the proportional coefficients of the corresponding fitting relationship can be determined as the pressure-speed compensation coefficients for component pump A and component pump B, respectively. When the pressure response exhibits obvious nonlinear characteristics, compensation coefficients can be set separately for different pressure ranges, or a lookup table correspondence between pressure deviation and speed compensation can be established.

[0116] The main controller is based on the pressure deviation. Calculate the speed compensation for component pump A and component pump B respectively: ; ; In the formula, This represents the speed compensation amount for component pump A at the current moment; This is the speed compensation amount for component B pump at the current moment; The pressure-speed compensation coefficient for component A pump; This is the pressure-speed compensation coefficient for the B component pump.

[0117] The pressure-speed compensation coefficients of the component A pump and the component B pump can have different values. This difference reflects the different displacement responses of the component A feeding system and the component B feeding system under varying pressure conditions. These different displacement responses can include the effects of the differences in the volumetric compressibility characteristics of the component A and component B raw materials, as well as the different effects of the corresponding metering pump's volumetric efficiency changing with back pressure.

[0118] The main controller adds the speed compensation amount to the current target speed of the corresponding metering pump to obtain the compensated target speed. Specifically, during the flow reduction control phase, the current target speed is the flow reduction target speed corrected based on the current flow reduction target of the proportional control valve. Specifically, the compensated target speed of component pump A is determined by its flow reduction target speed and... The superposition yields the compensated target speed of component B pump, which is determined by its reduced flow target speed and... The result is obtained by superposition.

[0119] Before issuing the compensated target speed, the main controller performs speed limiting. If the compensated target speed is higher than the corresponding motor's rated maximum speed, the main controller will limit the issued speed to that rated maximum speed.

[0120] Meanwhile, the main controller constrains the target speed after compensation based on the upper limit of the pressure of the mixing head and the upper limit of the total output flow allowed under the reduced flow state, so as to avoid overload of the metering pump group, overpressure of the pipeline, or weakening of the reduced flow effect of the proportional control valve due to excessive compensation.

[0121] After the amplitude limiting process, the main controller sends the compensated target speed to the driver of the metering pump group via the communication bus. The A component pump and the B component pump operate according to the updated target speed, correcting their actual output displacement per unit time, thereby maintaining the set mixing ratio of the A component raw material and the B component raw material during the flow reduction control process.

[0122] See attached document Figure 7 During the period when the proportional control valve maintains the reduced flow state, the main controller continuously reads the overall displacement change rate calculated in the current control cycle. To avoid misjudgments caused by environmental electromagnetic interference and detection circuit noise, the main controller does not use... Instead of using zero as the criterion for determining whether a metal component is stationary, the overall rate of displacement change is considered. absolute value Noise threshold for displacement change rate The displacement rate of change noise threshold in this specification is used to characterize the range of displacement rate of change fluctuation caused by detection noise, environmental interference, and differential calculation in a steady state, and corresponds to the displacement rate of change noise threshold in the flow recovery condition.

[0123] Displacement change rate noise threshold The displacement change rate noise peak-to-peak value can be determined based on the distance conversion and differential calculation of the eddy current coil output signal when the mold is closed and not injected.

[0124] when Less than or equal to And this state is maintained continuously for a preset waiting time. At that time, the main controller determined that the metal component did not show a continuous displacement trend, confirming that the displacement stability condition was met.

[0125] The main controller also reads the current moment's composite ultrasonic reflected echo energy. And call the overall ultrasound echo baseline obtained from the pre-injection baseline calibration. When the sensor array includes multiple sensor units, the main controller reads the ultrasonic reflection echo energy of each sensor unit. And call the ultrasonic echo reference of the unit corresponding to the sensor unit with the same number. .

[0126] As the fluid gradually enters the inner cavity and covers the inner wall area of ​​the mold corresponding to the sensor array, the acoustic interface between the non-ferromagnetic metal substrate of the mold and the medium inside the cavity changes from a solid-gas interface to a solid-liquid interface. Due to the difference in acoustic impedance between the fluid and air, the interface reflection conditions change, and the reflected echo energy received by the piezoelectric crystal decreases accordingly.

[0127] The main controller is based on the overall ultrasonic echo reference. and current comprehensive ultrasonic reflected echo energy Calculate the ultrasonic echo attenuation rate : ; Before performing the above calculations, the main controller first determines the overall ultrasonic echo reference. Is it effective? If Less than the preset effective lower limit threshold If the main controller determines that the pre-injection ultrasound baseline calibration is invalid, it will stop executing the current flow recovery judgment and output an ultrasound baseline abnormality alarm signal; if Greater than or equal to Then the main controller performs the ultrasonic echo attenuation rate calculation.

[0128] In the formula, The current moment represents the overall ultrasonic echo attenuation rate; The baseline for the overall ultrasound echo obtained when no fluid was injected into the cavity; This represents the combined ultrasonic reflected echo energy collected at the current moment.

[0129] When the sensor array includes multiple sensor units, the ultrasonic echo attenuation rate of the i-th sensor unit is... It can be calculated using the following formula: ; in, The ultrasonic echo reference obtained by the i-th sensor unit during the pre-injection reference calibration is... Let be the unit ultrasonic reflected echo energy collected by the i-th sensor unit at the current moment.

[0130] The main controller will calculate the overall ultrasonic echo attenuation rate. Compared with the preset ultrasonic echo attenuation threshold Comparison. When Greater than or equal to At this point, the main controller determines that the fluid has covered the detection area of ​​the corresponding sensor unit. For sensor units that have a spatial correspondence with the pre-positioning area of ​​the metal component, when their comprehensive ultrasonic echo attenuation rate reaches the preset ultrasonic echo attenuation threshold, it indicates that the acoustic interface of the corresponding detection area has changed from the solid-gas interface before injection to the acoustic interface involving fluid, thus indicating that the fluid has entered the corresponding detection area.

[0131] By combining the predetermined spatial correspondence between the sensor unit detection area and the pre-positioning area of ​​the metal component, the main controller can further determine that the fluid has reached the area where the metal component is located. For the anti-smashing steel head, when one or more sensor units located in its pre-positioning area or adjacent area meet the coverage determination condition, the main controller determines that the fluid has reached the area where the anti-smashing steel head is located, and forms a fluid coverage area on at least part of the outer surface of the anti-smashing steel head. The setting position of the sensor unit is determined according to the pre-positioning position of the metal component in the mold cavity, so that the detection area corresponding to at least one sensor unit is located in the area where the metal component is located or in the characteristic area where the fluid forms a coverage layer after reaching the metal component. When the ultrasonic echo attenuation rate of the detection area reaches the preset ultrasonic echo attenuation threshold, it indicates that the acoustic interface of the detection area has changed from the solid-gas interface before injection to the solid-liquid interface. This indicates that the fluid has reached the area where the metal component is located and covers the metal component, thereby forming a fluid buffer layer on the outside of the metal component to reduce the direct impact of subsequent fluid.

[0132] When the sensor array includes multiple sensor units, the main controller compares the ultrasonic echo attenuation rate of each sensor unit. With ultrasound echo attenuation threshold The system determines whether the detection area corresponding to the sensor array has been covered by fluid based on the number of sensor units that reach the threshold. In one embodiment, multiple sensor units corresponding to a pre-positioned area of ​​the metal component can be set as a coverage determination sensor group. When the number of sensor units in the coverage determination sensor group that reach the ultrasonic echo attenuation threshold is not less than a preset number M, the fluid coverage condition is determined to be met. In another embodiment, it is also possible to require all designated sensor units located in areas corresponding to different positions of the metal component to reach the ultrasonic echo attenuation threshold. Specifically, the number of sensor units reaching the threshold can be set to be not less than a preset number M, or all sensor units can be set to reach the threshold, as the fluid coverage determination condition.

[0133] Ultrasonic echo attenuation threshold A preliminary setting can be made based on the acoustic impedance relationship between the non-ferromagnetic metal substrate of the mold and the injected fluid, and trial calibration can be performed in conjunction with the mold material, injected fluid type, operating temperature, and sensor array embedding depth. In one embodiment, It can be set within the range of 15% to 30%.

[0134] In one mold calibration implementation, firstly, with the mold closed and the cavity empty without fluid injection, multiple ultrasonic echo samples are taken from the corresponding sensor unit to obtain the statistical range of ultrasonic echo energy in the empty cavity state; then, after confirming that the fluid has stably covered the target detection area, multiple ultrasonic echo samples are taken to obtain the statistical range of ultrasonic echo energy in the fluid-covered state.

[0135] The ultrasonic echo attenuation threshold is determined based on the ultrasonic echo attenuation rate distribution corresponding to the cavity state and the fluid coverage state, enabling the two states to be distinguished under preset reliability requirements. For different mold materials, mold wall thicknesses, raw material types, or operating temperatures, corresponding ultrasonic echo attenuation threshold parameter tables can be established, and the corresponding parameters can be called according to the current molding process.

[0136] The main controller jointly determines the displacement stability condition and the fluid coverage determination condition. The main controller only triggers the flow recovery condition when both the displacement stability condition and the fluid coverage determination condition are met.

[0137] The above-mentioned joint judgment uses eddy current displacement detection and ultrasonic echo detection to determine the recovery time, which can reduce the probability of false triggering caused by local bubbles, mechanical vibration or fluctuations of a single detection signal.

[0138] Based on the above joint judgment, after the displacement state of the metal component has stabilized and the presence of fluid medium is confirmed in the detection area corresponding to the area where the metal component is located, flow recovery control is then executed, thereby reducing the risk of the metal component being subjected to secondary transient impact during the flow recovery process.

[0139] The fluid buffer or fluid coating layer in this specification refers to the fluid medium region that has reached the area where the metal component is located before the proportional control valve recovers to a larger opening, and is situated between the subsequent high-speed fluid flow path and the surface of the metal component. The fluid coating layer does not require a fixed thickness or fixed geometric boundaries; its function is to ensure that the fluid entering this region during subsequent flow recovery first undergoes momentum exchange with the existing fluid medium, thereby reducing the transient impact of the high-speed fluid directly acting on the surface of the metal component.

[0140] Once the flow recovery condition is met, the main controller stops outputting the current reduction control voltage and enters ramp recovery control. To avoid secondary fluid impact caused by sudden changes in the proportional control valve spool opening, the main controller generates a gradual recovery voltage according to preset voltage recovery slope parameters. .

[0141] Gradual recovery voltage It can be calculated using the following formula: ; In the formula, The current gradual recovery voltage output to the proportional control valve; This is the sustaining control voltage corresponding to the proportional control valve when the flow recovery condition is met; t represents the start time of the recovery action; t represents the current time. This is the voltage recovery slope parameter; The initial drive voltage corresponding to the initial set flow rate of the proportional control valve.

[0142] In discrete control processes, the main controller can also operate according to the control cycle. Increase the output voltage cycle by cycle: ; When the gradual recovery voltage achieve At this time, the main controller stops increasing the output voltage and maintains the control voltage of the proportional control valve at a certain value. ; This is the recovery control voltage output to the proportional control valve in the previous control cycle; For the first The recovery control voltage is output to the proportional control valve in each control cycle. Under the action of gradually increasing the flow cross-sectional area, the flow rate of the fluid entering the inner cavity gradually recovers to the initial set flow rate; This indicates taking the smaller of the two values ​​within the parentheses; This is the preset voltage recovery slope parameter.

[0143] See attached document Figure 8 During injection, the proportional control valve may enter a reduced flow state according to the aforementioned control process, and the metering pump unit may also perform speed feedforward compensation based on pressure deviation. Therefore, the input flow rate of the mixed fluid is not always maintained at a fixed theoretical flow rate. If the injection volume is calculated simply by multiplying the set flow rate by the injection time, volumetric measurement errors are likely to occur.

[0144] Based on this, the main controller uses discrete accumulation calculation to obtain the cumulative injection volume from the start of the injection action to the current time t, according to the actual feedback rotation speeds of component pumps A and B. The calculation formula is as follows: ; In the formula, From the start of the injection action to the current moment The cumulative injection volume of fluid; This refers to the sequence number of the discrete control cycle; This represents the current cumulative total number of control cycles; and The first The actual feedback speeds of component pump A and component pump B are read in real time via the communication bus within each control cycle. and These are the equivalent single-cycle displacement parameters for component pump A and component pump B, respectively. Their values ​​are determined by the mechanical geometric parameters of the metering pump and the pre-calibrated volumetric efficiency; and the corresponding volumetric efficiency correction value can be called according to the current pressure range. It is a fixed control cycle.

[0145] when and When the unit is revolutions per minute (rpm), the main controller can first convert it to revolutions per second (rpm) before participating in the above calculations; alternatively, the unit conversion factor can be incorporated. and In order to ensure the cumulative injection volume The units are consistent.

[0146] and The volumetric efficiency can be determined based on the mechanical geometry parameters of the metering pump and the pre-calibrated volumetric efficiency. The main controller can also retrieve the corresponding volumetric efficiency correction value based on the current pressure range. and Corrections were made to improve the accuracy of the cumulative injection volume calculation.

[0147] The main controller will accumulate the injection volume. With the preset target injection volume Compare. Target injection volume. The volume is determined based on the remaining fillable volume of the mold cavity after the metal components are placed.

[0148] To compensate for the compression of the polyurethane molding material in the high-pressure pipeline and the volume shrinkage during the curing process, the target injection volume is... It can be set to 1.02 to 1.05 times the remaining fillable volume.

[0149] when If the main controller determines that the mold filling is not complete, it will maintain the current injection state.

[0150] when When the main controller determines that the single injection volume has reached the target, it triggers the shutdown logic.

[0151] To prevent continuous material output from the equipment due to pipe rupture, sensor communication failure, or metering anomalies, the main controller is also set with a maximum safe injection time. Once the injection is initiated, the main controller starts timing.

[0152] If the cumulative injection time reaches The cumulative injection volume Still smaller than the target injection volume If the main controller triggers the injection stop control, it will output an injection timeout alarm signal.

[0153] Maximum safe injection time It can be set to 1.2 times the theoretical time required for the system to fill the mold cavity at the lowest design flow rate.

[0154] Within the same control cycle or adjacent control cycles when the cumulative injection volume is confirmed to be within the target range, the main controller outputs a shut-off control voltage to the drive circuit of the proportional control valve, causing the proportional control valve to close. At the same time, the main controller sends a speed zeroing command to the driver of the metering pump group, causing the A component pump and the B component pump to stop outputting.

[0155] After the proportional control valve is closed, the fluid supply path from the mixing head to the mold cavity is cut off, and the metering pump unit stops operating simultaneously. Thus, the single injection operation ends.

[0156] After the injection is completed, the main controller enters the mold closing, pressure holding, and curing monitoring stage. At this time, the mold remains closed and locked, and the inner cavity and the channels that maintain pressure communication with it form a nearly closed cavity.

[0157] During the closed-mold pressure holding and curing monitoring stage, the main controller starts the curing timer and continuously reads the pressure value fed back by the second pressure transmitter while maintaining pressure communication between the second pressure transmitter and the inner cavity. .

[0158] During the cross-linking and curing process, polyurethane molding materials may undergo volume shrinkage, causing the static pressure in the inner cavity and its pressure-connected areas to gradually decrease. The main controller can adjust the pressure value based on feedback from the second pressure transmitter. Calculate the static pressure drop rate : ; When the static pressure drop rate When the pressure changes are within the preset allowable range, the main controller determines that the pressure changes during the curing process are within the normal range; The pressure value collected in the previous control cycle; It is a fixed control cycle.

[0159] when greater than the preset pressure drop rate threshold If the pressure drop exceeds the preset pressure drop threshold within a preset time, the main controller determines that the mold may have a sealing failure or a risk of leakage of molding material, and records the corresponding abnormal information.

[0160] The abnormal information may include the time of the abnormality and the pressure value of the second pressure transmitter. Static pressure drop rate Cumulative injection volume And the current molding cycle number, for future traceability.

[0161] When the cumulative time of the curing timer reaches the preset cross-linking curing cycle and no abnormal pressure is detected that prohibits mold opening, the main controller determines that the current molding cycle has ended and outputs a mold opening permission signal, waiting for the subsequent demolding operation.

[0162] To verify the technical effectiveness of this system in a real safety shoe production scenario, we conducted a comparative verification of groups A and B on a PU injection molding production line in a shoe factory.

[0163] Control group (traditional process): Open-loop timed and quantitative injection was used, with the valve opening and pump speed fixed throughout the process.

[0164] Experimental group (the present invention): Enable dual-parameter detection, adaptive current reduction and anti-collision, and speed feedforward compensation functions.

[0165] Test sample: 100 pairs of safety shoes with embedded anti-smashing steel toe caps produced continuously in each group.

[0166] During the experiment, the background industrial control computer synchronously captured multi-dimensional operating data of the control system and output corresponding process verification graphs and statistical charts.

[0167] Dynamic response verification during the experiment (combined with) Figure 9 , Figure 10 ): To analyze the actual behavior of the system in this invention at the moment of encountering "fluid impact," we retrieved millisecond-level high-frequency sampling data from a typical single injection cycle in the experimental group, generating... Figure 9 (Scene anti-collision response animation).

[0168] exist Figure 9 The upper-middle subplot records the "dynamic displacement trend" of the steel cap. As can be seen, a sharp pulse change occurs on the curve the instant the fluid comes into contact with the steel cap, indicating that the steel cap is being pushed backward by the strong water hammer effect.

[0169] The lower subplot records the "proportional control valve control voltage". At the same moment the upper pulse appears, the lower voltage curve shows a cliff-like "step drop" (analog quantity down), then remains low, and finally shows a gentle slope upward.

[0170] exist Figure 10 (Using a dual Y-axis mapping structure): The solid curve (mapped to the Y-axis on the left) shows the upstream "pipeline pressure fluctuation" during valve clamping, with a clear "high pressure peak" lasting for tens of milliseconds.

[0171] The two dashed lines (mapped to the right Y-axis) represent the "speed compensation amounts" automatically issued by the system to pumps A and B, respectively. It can be clearly seen that the pump representing the softer material B experiences a significantly greater increase in speed than the pump representing material A; and the overall envelope of these two speed compensation curves perfectly matches the high-pressure peak of the solid line.

[0172] The graphs demonstrate that the system did not intervene blindly, but rather, based on the real-time pressure buildup and the different pressure characteristics of the two materials, it intelligently adjusted the speed of different pumps, thus maintaining a perfect 1:1 ratio.

[0173] Batch finished product quality statistical verification (combined) Figure 11 (with statistical tables) After completing the production of 100 pairs of samples and allowing them to fully solidify, the quality inspection department conducted a comprehensive measurement of the "final offset of the steel toe cap" and the "physical yield of the PU sole" of all finished products.

[0174] The final offset of the steel cap was determined based on the designed positioning position before injection molding. The actual position of the steel cap after molding was measured, and the maximum positional deviation between the actual position and the designed position was calculated. In the same batch of control tests, the control group and the experimental group used the same measurement benchmark, measurement position, and judgment method to ensure the comparability of the data between the two groups.

[0175] For the statistics of deviation error rate, when the final offset of the steel head is greater than the preset safety tolerance of 1.5mm, it is recorded as a deviation error sample; the deviation error rate is the percentage of the number of deviation error samples to the total number of samples in the corresponding test group.

[0176] For the most critical issue of the offset of the anti-smashing steel cap, we visualized and rendered 100 discrete measurement data points from two sets of samples, generating... Figure 11 (Comparison box plot of finished product quality).

[0177] exist Figure 11 Box plot of classification: The control group (traditional process) has an extremely wide distribution of boxes, with very long upper and lower quartiles, and a group of outliers (abnormal values) at the top that pierce the horizontal red line representing the "1.5mm safety tolerance".

[0178] The test box (the present invention) was extremely compressed, becoming very flat and pressed tightly against the bottom of the coordinate axis, with no data lines touching the 1.5mm safety red line.

[0179] The diagrams visually demonstrate that this invention has absolute dominance over process consistency in mass production.

[0180] The actual mixing ratio error of components A and B is determined based on the actual output of component A and component B raw materials within the same injection cycle. The actual output can be calculated based on the actual feedback speed of the calibrated metering pump, the equivalent single-cycle displacement parameters, and the volumetric efficiency correction value for the corresponding pressure range, or verified through independent mass or volume testing methods.

[0181] Using the target mixing ratio set in the process as a benchmark, the deviation of the actual mixing ratio from the target mixing ratio was calculated, and the maximum deviation range within a single molding cycle or during batch testing was statistically analyzed. The same mixing ratio error calculation method was used for both the control and experimental groups.

[0182] Based on the above graphs, the final quantitative statistical results are shown in the table below: Finished steel cap misalignment rate 8.0% (greater than tolerance 1.5mm) 0.0% Average maximum dynamic displacement of steel head 1.85mm 0.21mm Error in the actual mixing ratio of materials A and B Maximum drift ±4.2% Stable within ±0.6% Yield of physical properties of polyurethane shoe soles 92.5% 99.8% Experiments have fully demonstrated that the present invention not only successfully solved the industry problem of "injection impact causing displacement of inserts" in the context of safety shoe upper molding, but also resolved the chain reaction of "proportion imbalance" caused by flow control through ingenious algorithms, achieving a substantial leap in product yield and automated process.

[0183] The yield rate of physical properties of polyurethane shoe soles was statistically analyzed according to unified quality inspection rules. For each test group, samples were tested according to the pre-set physical property test items and qualification criteria for polyurethane shoe soles; when all specified test items of the corresponding sample met the qualification criteria, it was recorded as a physically qualified sample. The yield rate of physical properties is the percentage of qualified samples out of the total number of valid test samples in the corresponding test group.

[0184] The control group and the experimental group used the same material system, mold specifications, curing conditions and testing methods to reduce the impact of non-control factors on the comparison of results.

[0185] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An adaptive digital control system for a safety shoe molding process, characterized in that, It includes a main controller, and a metering pump set, a proportional control valve, a displacement sensor, and a pressure sensor, which are respectively communicatively connected to the main controller; the metering pump set includes a first metering pump for conveying a first component raw material and a second metering pump for conveying a second component raw material, and the proportional control valve is located on a pipeline downstream of the metering pump set; The main controller is configured to perform the following operations: After injection molding starts, the real-time displacement signal of the metal component inside the mold collected by the displacement sensor is acquired, and the displacement change rate of the metal component is calculated. When the absolute value of the displacement change rate is greater than or equal to the preset displacement change rate threshold, a flow reduction control signal is output to the proportional control valve to reduce the valve opening and enter the flow reduction control stage to reduce the impact force of the fluid on the metal component. During the flow reduction control phase, the pressure signal of the upstream pipeline of the proportional control valve collected by the pressure sensor is acquired to calculate the pressure deviation. Based on the pressure deviation and the pressure response characteristics corresponding to the first component raw material and the second component raw material respectively, the corresponding speed compensation amount is determined, and the speed feedforward compensation control is performed on the first metering pump and the second metering pump respectively. The pressure response characteristics refer to the comprehensive response characteristics of the first component raw material, the second component raw material and their corresponding metering pumps or feeding channels on the actual output displacement under the condition of pipeline pressure change. The pressure response characteristics include at least the difference in volume compressibility between the first component raw material and the second component raw material, the pressure-displacement response characteristics at different pressure operating points, and the response characteristics of the volumetric efficiency of the first metering pump and the second metering pump as the back pressure changes. When the system state determined at least based on the displacement change rate is detected to meet the preset flow recovery condition, a recovery control signal is output to the proportional control valve so that the proportional control valve is restored to the initial valve opening at the start of injection molding. The system also includes at least one ultrasonic sensor that is communicatively connected to the main controller. The ultrasonic sensor and the corresponding displacement sensor are coaxially arranged on the non-forming side of the mold. The ultrasonic sensor is used to emit ultrasonic waves toward the inner cavity of the mold and receive the reflected echo energy signal. The preset traffic recovery conditions set in the main controller include a first condition and a second condition that must be met simultaneously: The first condition is that the absolute value of the displacement change rate is less than or equal to the preset displacement change rate noise threshold for a continuous preset time period. The second condition is: the real-time echo energy signal received by the ultrasonic sensor relative to the ultrasonic echo attenuation rate of the cavity reference state is greater than the preset ultrasonic echo attenuation threshold, which is used to determine that the fluid has covered the metal component to form a buffer protective layer.

2. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, Before initiating the injection molding process, the main controller is also configured to perform a benchmark calibration operation: After the mold is closed and before the raw material is injected, the initial distance data collected by the displacement sensor is acquired and stored as the equivalent displacement zero-position reference of the metal component.

3. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, The specific logic for the main controller to output a current reduction control signal to the proportional control valve is as follows: The current reduction control voltage is calculated based on the preset initial driving voltage, displacement change rate threshold and proportional gain coefficient. The current reduction control voltage is equal to the initial drive voltage minus the voltage adjustment amount; Wherein, the voltage regulation amount is equal to the difference between the absolute value of the displacement change rate in the current cycle and the displacement change rate threshold, multiplied by the proportional gain coefficient; The main controller sends the current reduction control voltage as the current reduction control signal to the proportional control valve.

4. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, The specific logic of the main controller performing speed feedforward compensation control on the first metering pump and the second metering pump based on the pressure deviation includes: The difference between the current pipeline pressure and the steady-state reference pressure upstream of the proportional control valve is calculated as the pressure deviation. A first pressure-speed compensation coefficient corresponding to the first component raw material and a second pressure-speed compensation coefficient corresponding to the second component raw material are preset; the values ​​of the first pressure-speed compensation coefficient and the second pressure-speed compensation coefficient are not equal, and the difference in their values ​​is determined based on the pressure response characteristics corresponding to the first component raw material and the second component raw material respectively; the pressure response characteristics include at least one of the following: volume compressibility difference, pressure-actual displacement response relationship, and response characteristics of metering pump volumetric efficiency as a function of back pressure. The pressure deviation is multiplied by the first pressure-speed compensation coefficient and the second pressure-speed compensation coefficient respectively to calculate the first speed compensation amount and the second speed compensation amount. The first speed compensation amount is added to the current target speed of the first metering pump to obtain the compensated target speed of the first metering pump; the second speed compensation amount is added to the current target speed of the second metering pump to obtain the compensated target speed of the second metering pump.

5. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, The ultrasonic echo attenuation rate is calculated as follows: during the reference calibration process before injection molding starts, the initial echo energy integral value corresponding to the target detection channel is obtained within the preset ultrasonic echo receiving window when the mold is in a cavity state, and it is used as the ultrasonic echo reference corresponding to the target detection area; during injection molding, the real-time echo energy integral value of the target detection channel in the current cycle is obtained within the same ultrasonic echo receiving window. The ultrasonic echo attenuation rate is equal to the difference between the initial echo energy integral value and the real-time echo energy integral value, divided by the initial echo energy integral value. Wherein, when the target detection channel is an overall fusion detection channel, the ultrasonic echo reference is an overall ultrasonic echo reference; when the target detection channel is a detection channel corresponding to a sensor unit, the ultrasonic echo reference is a unit ultrasonic echo reference.

6. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, The main controller outputs a recovery control signal to the proportional control valve in the following manner: using a preset voltage recovery slope parameter, the control voltage of the proportional control valve is linearly increased from the current voltage value in the current reduction control stage over time until it is restored to the initial drive voltage corresponding to the initial valve opening at the start of injection molding.

7. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, The main controller is also configured to perform volume closed-loop termination control during the injection molding process: According to a fixed sampling control cycle, the actual feedback speed of the first metering pump and the actual feedback speed of the second metering pump are acquired in real time. By combining the equivalent single-cycle displacement parameters of the first metering pump and the equivalent single-cycle displacement parameters of the second metering pump, the volume of fluid injected in each sampling control cycle is integrated and accumulated to obtain the cumulative injection volume; When the cumulative injection volume is greater than or equal to the set target injection volume, a shut-off signal is output to the proportional control valve, and the metering pump group is controlled to stop.

8. The adaptive digital control system for the safety shoe molding process according to claim 1, characterized in that, The metal component is a steel toe cap pre-placed at the toe position of the mold, and the displacement sensor is a non-contact electromagnetic eddy current displacement sensor; the first component raw material is isocyanate, the second component raw material is polyol, and the injection molding is a two-component polyurethane continuous injection molding.

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