A method and system for controlling the spraying of plastic parts

Abstract

The present application relates to the technical field of spray automation control, and particularly relates to a plastic part spraying control method and system. The method comprises the following steps: in response to a feeding event after detecting that the temperature of a curing furnace reaches a preset target temperature; obtaining physical parameters related to the feeding event, and obtaining a current measured temperature of the curing furnace; based on the physical parameters, calculating a first power value for feedforward compensation of thermal disturbance caused by the feeding event; based on the first power value, the current measured temperature and the preset target temperature, determining a total compensation power for the curing furnace; and generating and outputting a heating control instruction corresponding to the total compensation power. The present application compensates the power during the feeding stage through feedforward compensation and real-time regulation, avoids passive adjustment lag after temperature sudden drop, and maintains stable furnace temperature during feeding.

Description

Technical Field

[0001] This invention relates to the field of automated spraying control technology, and in particular to a method and system for controlling the spraying of plastic parts. Background Technology

[0002] Plastic coating is a processing method that uses specific techniques to form decorative and functional coatings on the surface of polymer materials. It is commonly used in the production of high-end consumer electronics products such as mobile phone casings. This process, by uniformly adhering the coating to the workpiece surface and then curing it, gives the product excellent appearance and performance, and is a key step in enhancing the added value of the product.

[0003] Controlling the plastic parts spraying process is a core prerequisite for ensuring product quality stability. Among these processes, the stability of the topcoat curing stage directly determines the final performance of the coating, including whether key indicators such as adhesion, hardness, and abrasion resistance meet design standards. Currently, the industry mainstream uses continuous production lines, sending the sprayed workpieces into a curing oven for heating and curing, maintaining a stable temperature environment to ensure the coating is fully cured.

[0004] However, this continuous feeding mode presents a technical challenge: when a large number of cold workpieces at room temperature are continuously fed into a curing oven that has reached the set process temperature, the cold workpieces will quickly absorb heat from the oven, and the opening of the feed port will cause heat to dissipate, resulting in a sharp drop in the oven temperature in a short period of time, forming a significant temperature drop range.

[0005] Currently, the industry generally adopts a strategy of waiting for the temperature to recover, which means pausing the process timing until the furnace temperature rises back to the set range. This severely slows down the production cycle and reduces equipment utilization. More seriously, the first batch of workpieces that fail to cure at the standard process temperature are prone to quality defects such as soft paint film and insufficient adhesion, resulting in a decrease in product yield. Summary of the Invention

[0006] To address the technical problem in the production of plastic parts spray coating curing where a large number of room temperature cold workpieces continuously enter the curing oven and the feed inlet is opened, causing a sudden drop in oven temperature, which slows down production and causes workpiece quality defects, this invention provides solutions in the following aspects.

[0007] In a first aspect, the present invention provides a method for controlling the spraying of plastic parts, the method comprising the steps of:

[0008] After detecting that the temperature of the curing oven has reached the preset target temperature, a feeding event is responded to; at least one physical parameter related to the feeding event is acquired, and the current measured temperature of the curing oven is acquired; based on the at least one physical parameter, a first power value for feedforward compensation of the thermal disturbance caused by the feeding event is calculated; based on the first power value, the current measured temperature and the preset target temperature, the total compensation power for the curing oven is determined; and a heating control command corresponding to the total compensation power is generated and output.

[0009] This invention addresses the problem of sudden temperature drops in the oven caused by cold workpiece feeding and opening during the curing of plastic parts. It compensates for power fluctuations during the feeding stage through feedforward compensation and real-time control: once the oven temperature reaches the target, and a feeding event is detected, the thermal disturbance feedforward compensation power is immediately calculated based on physical parameters such as workpiece quantity and opening size. Simultaneously, the total compensation power is dynamically adjusted based on the current measured temperature and the target temperature difference, ensuring that heating commands respond to thermal disturbances in real time. This mechanism effectively avoids the passive adjustment lag after a sudden temperature drop in traditional control methods, maintaining a stable oven temperature during the feeding process. This solves the problem of prolonged curing cycles due to insufficient temperature, accelerating production, and reduces quality defects such as paint sagging and insufficient adhesion caused by temperature fluctuations, significantly improving product qualification rate and production stability.

[0010] Preferably, generating and outputting the heating control command corresponding to the total compensation power includes: predicting the predicted temperature at a future time point based on the total compensation power and the current measured temperature, and in combination with a preset power-temperature conversion coefficient; correcting the total compensation power according to the comparison result between the predicted temperature and the preset temperature range to obtain the final compensation power; and generating and outputting the heating control command based on the final compensation power.

[0011] This invention further improves temperature control accuracy and stability through a predictive correction mechanism. Based on the total compensation power, current temperature, and power-temperature conversion coefficient, it predicts future temperatures and anticipates the impact of thermal disturbances. Then, it corrects the power based on the deviation between the predicted temperature and the preset range, dynamically adapting to changes within the furnace. This process effectively suppresses temperature fluctuations, avoids the lag-induced overshoot or undershoot of traditional control methods, and allows the furnace temperature to more accurately match process requirements, reducing curing defects caused by temperature runaway.

[0012] Preferably, the step of predicting the predicted temperature at a future time point based on the total compensation power and the current measured temperature, combined with a preset power-temperature conversion coefficient, includes: calculating the ratio of a preset prediction time step to the heating inertia time constant characterizing the thermodynamic properties of the curing oven, taking the negative value of the exponential function, subtracting the exponential function value from 1 to obtain the heating inertia coefficient; multiplying the preset power-temperature conversion coefficient by the total compensation power, and then multiplying by the heating inertia coefficient to obtain the temperature change; and using the sum of the current measured temperature and the temperature change as the predicted temperature at a future time point.

[0013] This invention utilizes an exponential term to dynamically reflect the impact of thermal inertia on temperature changes, enabling quantitative prediction of future temperatures. This allows the system to anticipate temperature trends under disturbances such as feeding, providing a basis for subsequent power adjustments. It enhances the forward-looking nature of temperature control from the source, reduces temperature fluctuations caused by thermal inertia lag, and makes furnace temperature regulation more aligned with the dynamic needs of continuous feeding scenarios.

[0014] Preferably, the step of correcting the total compensation power includes: when the predicted temperature is higher than the upper limit of the preset temperature range, adjusting the total compensation power downward using an over-temperature correction coefficient less than 1 and inversely proportional to the difference between the predicted temperature and the upper limit; and when the predicted temperature is lower than the lower limit of the preset temperature range, adjusting the total compensation power upward using an under-temperature correction coefficient greater than 1 and proportional to the difference between the predicted temperature and the lower limit.

[0015] Preferably, determining the total compensation power for the curing oven includes: adding the first power value to the feedback power value to obtain the total compensation power for the curing oven; wherein the feedback power value is proportional to the difference between the current measured temperature and the preset target temperature.

[0016] Preferably, the physical parameters include at least one of the following: the quantity of material to be processed entering the curing oven per unit time, the opening status parameters of the curing oven, and the conveying speed of the material to be processed.

[0017] Preferably, the calculation of the first power value for feedforward compensation of the thermal disturbance caused by the feeding event includes: superimposing at least two physical models: a model for characterizing the endothermic effect caused by the material to be processed entering the curing oven; a model for characterizing the heat dissipation effect caused by the opening of the curing oven; and a model for characterizing the heat transfer effect caused by the material conveying system.

[0018] This invention calculates the first power value of feedforward compensation by superimposing three physical models: material heat absorption, furnace opening heat dissipation, and conveying system heat transfer, thereby achieving comprehensive and accurate quantification of thermal disturbances in the feed. The superposition of these three models upgrades feedforward compensation from a single dimension to multi-factor synergy, comprehensively capturing complex thermal disturbances in the feeding stage and avoiding the omission of some heat losses by a single model.

[0019] Preferably, the model for characterizing the endothermic effect caused by the material entering the curing oven includes: multiplying the endothermic power coefficient of a single material by the quantity of material entering the curing oven at the current moment, and recording it as the material endothermic power component; the model for characterizing the heat dissipation effect caused by the opening of the curing oven includes: calculating the difference between the measured temperature of the curing oven at the current moment and the ambient temperature, and then multiplying it by the heat dissipation coefficient per unit area of ​​the curing oven and the opening area at the current moment to obtain the heat dissipation power component of the oven body; the model for characterizing the heat transfer effect caused by the material conveying system includes: calculating the difference between the measured temperature of the curing oven at the current moment and the initial temperature of the material to be treated, and then multiplying it by the heat transfer coefficient per unit velocity of the material to be treated and the conveying speed at the current moment to obtain the material heat transfer power component.

[0020] This invention's first power value formula precisely models the heat absorption of materials, heat dissipation from the furnace body, and heat transfer of materials, comprehensively covering the thermal disturbance factors caused by cold workpiece feeding and openings. By quantifying the impact of different physical quantities on power compensation through parameters such as the heat absorption power coefficient of a single material, the heat dissipation coefficient per unit area, and the heat transfer coefficient per unit velocity, it achieves a precise breakdown and feedforward compensation calculation of thermal disturbances during the feeding stage. This enables the system to specifically pre-compensate for heat loss caused by cold workpiece input and heat dissipation from openings, suppressing sudden drops in furnace temperature at the source. This lays the foundation for precise control of the subsequent total compensation power, ensuring stable furnace temperature during continuous feeding and helping to improve the curing quality and production efficiency of plastic parts.

[0021] Preferably, the heating control command includes: sub-control commands for multiple preset zones set along the material conveying direction in the curing oven; the method further includes decomposing the total compensation power into sub-power values ​​corresponding to each preset zone according to a non-uniform distribution strategy, wherein the weight of the sub-power value allocated to the inlet zone is higher than the weight allocated to other zones.

[0022] In a second aspect, the present invention provides a plastic part spraying control system, which includes a memory and a processor. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, a plastic part spraying control method according to the first aspect of the present invention is implemented.

[0023] By adopting the above technical solution, a plastic part spraying control method of the first aspect of the present invention is generated into a computer program and stored in a memory so that it can be loaded and executed by a processor, thereby creating a terminal device based on the memory and the processor for convenient use.

[0024] The beneficial effects of this invention are as follows: This invention constructs a dynamic thermal balance model to accurately predict heat loss caused by material feeding and implements real-time millisecond-level compensation to curb temperature drop at its source. In terms of production efficiency, it achieves a continuous production mode of curing immediately upon feeding, eliminating the waiting period for reheating in traditional control and accelerating the production pace. Regarding product quality, it stabilizes the curing temperature fluctuation range, ensuring all workpieces are cured under consistent process conditions, reducing defects such as paint drips and insufficient adhesion, and improving yield and consistency of paint film performance. In terms of energy consumption control, it avoids repeated heating after large temperature fluctuations, improving energy utilization efficiency. Regarding system adaptability, it adapts to different thermal inertia heating equipment through parameter tuning and relies on a zoned control strategy to cope with complex spatial thermal field distributions, comprehensively optimizing the plastic parts curing production process. Attached Figure Description

[0025] Figure 1 A flowchart of a plastic part spraying control method provided in an embodiment of the present invention;

[0026] Figure 2 This is a structural block diagram of a plastic part spraying control system provided in an embodiment of the present invention. Detailed Implementation

[0027] The first aspect of this invention provides a method for controlling the spraying of plastic parts, such as... Figure 1 As shown, the method includes steps S100-S400:

[0028] Step S100: After detecting that the temperature of the curing oven has reached the preset target temperature, respond to the feeding event.

[0029] It should be noted that the core function of this step is to clarify the activation conditions and triggering timing of the control method, laying the foundation for subsequent targeted suppression of severe thermal disturbances during the feeding stage. In industrial production, curing equipment is not always operating at full load. If complex control logic is used throughout the entire process, it will result in redundant consumption of computing resources. Therefore, dynamic compensation control logic is applied only during the feeding stage, when thermal disturbances are most severe, while conventional PID control is used when the equipment is unloaded or in a steady-state insulation state. This avoids unnecessary waste of computing power and improves the accuracy of temperature fluctuation suppression through strategy focus.

[0030] Specifically, during the production preparation phase, the control system first executes an unloaded heating program. The system's built-in temperature sensor module continuously collects real-time temperature signals from the curing chamber and transmits them to the control unit for analysis. When the control unit determines that the real-time temperature has reached the preset target temperature and has been stably maintained within a very small tolerance range for the set duration, the feeding conditions are met. The system then automatically prepares to switch from steady-state heat preservation mode to dynamic compensation mode, triggering the control algorithm used to counteract feeding temperature disturbances.

[0031] At this point, the system has completed preparations for a seamless transition from conventional steady-state control to dynamic control.

[0032] Step S200: Obtain at least one physical parameter related to the feeding event and obtain the current measured temperature of the curing oven. Based on the at least one physical parameter, calculate a first power value for feedforward compensation of the thermal disturbance caused by the feeding event.

[0033] It should be noted that this step is the core technical link in realizing the transition from sensing to prediction in this invention. Unlike traditional control methods that passively wait for temperature changes, this invention actively quantifies the source of disturbances.

[0034] Based on this, physical parameters characterizing the intensity of feed disturbances are acquired and immediately substituted into a preset physical model for calculation, forming an inseparable continuous sensing-modeling process. The purpose of this step is to transform complex multi-source physical disturbance events into a single power compensation value that can be directly used for control in real time, thereby achieving true feedforward control and fundamentally overcoming the inherent hysteresis of feedback control.

[0035] Specifically, within a control cycle, for example, per second, the control system... The interface collects a set of physical parameters from various sensors on the production line. These physical parameters include: the amount of material entering per unit time obtained by machine vision or photoelectric sensors, the real-time opening area obtained by displacement sensors, and the material conveying speed obtained by reading data from servo encoders.

[0036] Within the same control cycle, the system uses these real-time data as input variables, substitutes them into a preset multivariate physical model, and calculates the first power value. This physical model is constructed by superimposing multiple independent physical effects. Its core logic is: when constructing the calculation formula, it ensures that every physical process that has a significant impact on thermal equilibrium is independently quantified and included in the total compensation.

[0037] Based on the above logic, curing oven The power loss at time t, i.e., the first power value, satisfies the following relationship:

[0038] ;

[0039] in, It is a curing oven The first power value at time 1. It is the heat absorption power coefficient of a single material to be processed. yes The amount of material to be processed entering the curing oven at any given time. It is the heat dissipation coefficient per unit area of ​​the curing oven. It is a curing oven The opening area at time [time] It is a curing oven The actual measured temperature at any given time. It is the ambient temperature. It is the heat transfer coefficient per unit velocity of the material to be processed. yes The conveying speed of materials to be processed at all times. It is the initial temperature of the material to be processed.

[0040] In this formula, It is a model used to characterize the endothermic effect caused by the material entering the curing oven, using the unit material endothermic coefficient. and The product of the quantities of materials to be processed entering the curing oven at any given time quantifies the heat absorbed by the cold materials when they enter the oven, directly reflecting the degree to which the cold workpiece consumes oven temperature. The model used to characterize the heat dissipation effect caused by the opening of the curing oven is based on the opening area of ​​the oven body, the temperature difference between the inside and outside of the oven, and the heat dissipation coefficient per unit area. The amount of heat lost from the furnace to the environment when the feed inlet is opened is calculated, reflecting the heat loss caused by the opening of the curing furnace. The larger the opening area of ​​the furnace body, the greater the power loss. By material conveying speed Furnace charge temperature difference and heat transfer coefficient per unit velocity It characterizes the heat exchange between the material and the furnace environment during the conveying process, and reflects the dynamic impact of the conveying process on the furnace temperature. The greater the temperature difference of the furnace charge, the greater the power loss.

[0041] This invention quantifies and superimposes three core thermal disturbances during the feeding process—material heat absorption, opening heat dissipation, and conveying heat—to form a first power value that can be directly used for control. Through this multi-factor decomposition and synthesis modeling approach, a precise characterization of complex thermal disturbances is achieved. This allows the control system to calculate the required compensation power in advance based on real-time parameters, providing accurate adjustment basis for feedforward control. This quickly offsets temperature fluctuations, avoids the lag problem of traditional feedback control, and ensures stable curing oven temperature.

[0042] It should be added that, regarding , , The value of is calculated using experimental methods, or it can be calculated based on theoretical calculations or historical experience. The experimental method will be used as an example here.

[0043] For heat dissipation coefficient per unit area When the curing oven is unloaded, set a stable oven temperature that is higher than the ambient temperature. Measure the opening area of ​​the curing oven. Simultaneously record ambient temperature The amount of heat lost through the opening per unit time is measured using equipment such as a heat flow meter. According to the formula Calculate the heat dissipation coefficient per unit area To improve accuracy, the furnace temperature can be varied multiple times and the experiment repeated to obtain a more accurate average value.

[0044] For the heat transfer coefficient per unit velocity of the material to be processed By placing materials inside the curing oven and setting the conveyor belt to different speeds... The system is run and its temperature changes at different speeds, as well as the temperature changes inside the furnace, are recorded. Other conditions, such as heating power and ambient temperature, are kept relatively stable. By analyzing the relationship between material temperature change and conveyor belt speed, and combining this with heat transfer principles, a model is fitted. The value. For example, a value containing... The heat transfer model was obtained, and the experimental data were fitted and solved using data processing methods such as the least squares method.

[0045] The endothermic power coefficient of a single material to be processed By placing in the curing oven One material to be processed, record the initial temperature inside the furnace. Then with stable power Heating for a period of time Then, the temperature change of the material during this period was recorded simultaneously. and changes in furnace temperature According to the law of conservation of energy, the total heat absorbed by the material satisfies the following relationship: Simultaneously measure the mass of the material. Specific heat capacity Combined with thermodynamic formulas It can be calculated By combining the two formulas, we can deduce the result. .

[0046] also, The unit is Therefore, the unit of the result for each term in this formula is... To maintain consistency. , The unit is , The unit is The product of the two is approximately equal to the sum of the products. The result is ,and The units are standardized. For , The unit is , The unit is , The unit is After multiplying the three and I was invited there, and the result was... ,and The units are standardized. For , The unit is , The unit is , The unit is After multiplying the three and I was invited there, and the result was... ,and The units are unified.

[0047] At this point, the feedforward compensation calculation was completed, and the first power value was obtained.

[0048] Step S300: Based on the first power value, the current measured temperature, and the preset target temperature, determine the total compensation power for the curing oven.

[0049] It should be noted that physical models are rarely absolutely accurate in practical applications. This is because simplifications or approximations of complex factors are inevitable during modeling, leading to deviations between the model and actual operating conditions. If only feedforward control is relied upon, as it is an open-loop system, it cannot correct the inherent errors of the model itself, nor can it cope with subtle disturbances not considered by the model. Over long-term operation, these uncorrected deviations and disturbances may gradually accumulate, affecting the stability of the control performance.

[0050] Based on this, this invention introduces feedback control as a dynamic calibration mechanism. Feedforward control pre-compensates for predictable thermal disturbances, while feedback control monitors the deviation between the actual temperature and the target value in real time, dynamically correcting model errors and unmodeled disturbances. The two form a synergistic and complementary closed-loop control system. This combined control strategy leverages the rapid response advantage of feedforward control while utilizing the calibration function of feedback control to ensure the stability of control accuracy during long-term operation, effectively addressing various anticipated and sudden temperature fluctuations.

[0051] Specifically, the total compensation power is determined by adding the first power value of the feedforward compensation to the feedback power value, and the total compensation power satisfies the following relationship:

[0052] ;

[0053] in, yes Total compensation power of the curing oven It is a curing oven The first power value at time 1. It is a curing oven The actual measured temperature at any given time. This is the preset target temperature of the curing oven. It is the temperature feedback proportionality coefficient.

[0054] In this formula, the curing oven The first power value at time t is used for compensation This feature compensates for heat loss caused by multiple factors, including heat absorption by materials, heat dissipation from the curing furnace opening, and heat conduction by cold materials, thus preventing a significant drop in furnace temperature. This is a temperature error feedback term, used for proportional response control of the difference between the measured temperature inside the furnace and the set target temperature. If there is a large temperature deviation, this term can immediately generate corresponding power compensation to maintain the temperature within the set range. Within the range of high-precision fluctuations.

[0055] In addition, it should be noted that, The range of values ​​is It can be adjusted according to the equipment's thermal inertia and response speed parameters, or set according to requirements.

[0056] With curing oven volume For example, the maximum heating power of this curing oven is It has a relatively large thermal inertia. When the workpiece is a thin plastic shell, for example, a single workpiece weighs... The feed rate is per minute When the furnace temperature is disturbed, the recovery rate is relatively slow. To obtain a larger value, for example When producing large-sized, thick-walled plastic parts, the weight of a single workpiece is... The feed rate was reduced to per minute. During this process, the temperature fluctuations inside the furnace are more gradual, but the amplitude of each individual disturbance is larger. Therefore, it is necessary to reduce the temperature. to .

[0057] At this point, the total compensation power of the curing oven was obtained.

[0058] Step S400: Generate and output heating control commands corresponding to the total compensation power.

[0059] It should be noted that directly converting the acquired total compensation power into heating commands is only a basic solution. To achieve more precise control, two key physical factors need to be considered: first, the curing oven has a response delay, i.e., thermal inertia, and directly outputting high power can easily cause the temperature to exceed the target value; second, the spatial distribution of thermal disturbances within the curing oven is not uniform. Therefore, this invention considers proactively addressing the delay characteristics of the curing oven through predictive correction in the time dimension, and simultaneously adjusting the heating amount according to the differences in thermal disturbances in different areas of the oven through intelligent spatial allocation, ultimately obtaining optimized control commands. These will be explained in detail below.

[0060] Predictive corrections in the time dimension are used to proactively address the delayed characteristics of the curing oven. It's important to note that even if the total compensation power of the curing oven is calculated in real-time every second during the feeding process, the actual oven temperature response will be significantly delayed due to the lag in heat release. In this situation, simply relying on the current total compensation power of the curing oven for heating control can easily lead to two problems: first, insufficient heating, meaning heating has started but the temperature continues to drop, due to the lag in power compensation; second, overheating, meaning the oven temperature has already risen, but the compensation power continues to be applied, causing the temperature to exceed the set value.

[0061] Based on this, this step further introduces thermodynamic response modeling on the basis of the original power compensation model. By constructing a temperature prediction model, it can determine in advance whether the current power output will cause the future temperature to deviate from the target value, and then perform targeted power limiting or enhancement regulation to ultimately achieve predictive control.

[0062] Specifically, in existing technologies, heating systems are often modeled as first-order linear systems. This invention adopts this concept and constructs the heating system of the curing oven as a first-order linear system:

[0063] ;

[0064] Therefore, the differential equation of the heating system is constructed and solved to obtain:

[0065] ;

[0066] in, It is the heating inertia time constant that characterizes the thermodynamic properties of the curing oven. It is the first derivative of temperature with respect to time. yes Predicted temperature at any time It is a curing oven Total compensation power at any time, It is the preset power-temperature conversion factor. yes Predicted temperature at any time This is the preset prediction time step. The specific solution process is existing technology and will not be elaborated here.

[0067] Based on this, a curing oven is introduced. The measured temperature at a given time point yields the predicted temperature of the curing oven at future time points, satisfying the following relationship:

[0068] ;

[0069] in, It is a curing oven Predicted temperature at any time It is a curing oven The actual measured temperature at any given time. It is a curing oven Total compensation power at any time, It is the preset power-temperature conversion factor. It is the heating inertia time constant that characterizes the thermodynamic properties of the curing oven. It is the preset prediction time step.

[0070] In this formula, Describes the prediction time step This refers to the proportion of the power effect due to thermal inertia. Because the curing oven has thermal inertia, the temperature will not respond instantly to a power change. This index reflects the cumulative effect of the compensating power on temperature over time. The closer The closer the temperature change is to the steady-state change that the compensation power can theoretically bring; if much smaller Therefore, the temperature change is relatively limited. The total compensation power is converted into a temperature change, establishing a quantitative correlation between power input and temperature response, so that the effect of compensation power can be predicted and controlled in the form of temperature change.

[0071] This formula, based on the current measured temperature and total compensation power, combined with the curing oven's thermal inertia and other characteristics, enables the prediction of future oven temperatures. By predicting the temperature, it can be determined in advance whether the total compensation power will cause the oven temperature to deviate from the target value, thus providing support for subsequent control decisions: if the predicted temperature will be lower than the target, the compensation power can be increased in advance; if the predicted temperature will exceed the target, the power can be limited or reduced in advance. This achieves predictive control, alleviates temperature fluctuations caused by curing oven response delays and thermal inertia, improves the accuracy and stability of curing oven temperature control, and allows the oven temperature to be maintained more stably within the target range.

[0072] It should be added that, regarding and The value of is calculated using experimental methods, or it can be calculated based on theoretical calculations or historical experience. The experimental method will be used as an example here.

[0073] For power temperature conversion coefficient With the curing oven unloaded and the environment stable, a stable initial temperature is set. This is typically the ambient temperature. After turning on the heating system, input a stable and known power value. The compensation power is used to continuously heat for a period of time. Afterwards, for example, after 1 hour, record the end time. Temperature. According to the formula Calculated To improve To ensure accuracy, the input power can be changed multiple times and the experiment repeated to obtain the average value.

[0074] The heating inertia time constant, which characterizes the thermodynamic properties of the curing oven. A step-change compensation power is applied to the curing oven, i.e., the power instantaneously changes from one value to another, and the temperature-time curve is plotted. Since the thermal response of the curing oven conforms to the characteristics of a first-order linear system, the temperature change follows an exponentially approaching steady-state law. Its theoretical model is as follows:

[0075] ;

[0076] in, The steady-state temperature of the curing oven. This is the initial temperature of the curing oven. yes Predicted temperature at any time It is the first The moment, that is, the current moment. Heating inertia time constant used to characterize the thermodynamic properties of curing ovens.

[0077] A custom exponential model is used to fit the curve using a curve fitting tool. Fitting tools such as Origin and MATLAB can be used. The experimentally measured temperature-time data is substituted into the model to obtain the fitting result. This ensures the optimal match between the theoretical curve and the experimental data; this value is the heating inertia time constant of the curing oven.

[0078] It should be noted that the predicted temperature for future times was obtained above. Based on this predicted temperature, the power at the current time can be corrected to ensure that the future temperature remains within a preset range, avoiding overheating or underheating. The corrected compensation power satisfies the following relationship:

[0079] ;

[0080] in, It is a curing oven The corrected compensation power at any given time. It is a curing oven Total compensation power at any time, It is a curing oven Predicted temperature at any time It is the upper limit of the preset temperature range. It is the lower limit of the preset temperature range. It is a curing oven Over-temperature correction factor at all times It is a curing oven Timing undertemperature correction factor.

[0081] In this formula, When an over-temperature warning is issued, use [the appropriate method]. Reduce the total compensation power to prevent the temperature from continuing to rise and avoid product defects caused by the actual temperature exceeding the upper limit, such as over-curing of plastics or scorching of coatings. At this time, a low temperature warning should be issued, and at this time... Increase the total compensation power to replenish heat in advance and avoid insufficient curing due to the actual temperature dropping below the lower limit, such as insufficient glue drying or poor coating adhesion. Within the normal temperature range, maintain the original power, reduce unnecessary adjustments, and maintain system stability.

[0082] It should be noted that the preset temperature range is set specifically according to the process requirements of different workpieces. Taking the UV curing of a transparent plastic back cover for a mobile phone as an example, the preset target temperature is... The allowable fluctuation range is The corresponding preset temperature range is In other words , .

[0083] It should be noted that, regarding the acquisition of the over-temperature correction factor, if the predicted temperature is higher than the upper limit of the preset temperature range, in order to suppress the total compensation power and avoid future over-temperature, the over-temperature correction factor needs to be less than 1.

[0084] Based on this Satisfying the relation:

[0085] ;

[0086] in, It is a curing oven Over-temperature correction factor at all times It is a maximum value function. It is a preset over-temperature correction coefficient, used to limit the lower limit of power adjustment and avoid undercompensation due to excessive suppression. It can be set to 0.6 or adjusted according to needs. The over-temperature penalty coefficient can be set to... Within this range, it is possible to avoid overly aggressive corrections that could cause new problems, and to make power adjustments more stable. It is a curing oven Predicted temperature at any time It is the upper limit of the preset temperature range. It is the preset target temperature of the curing oven.

[0087] It should also be noted that, regarding the acquisition of the undertemperature correction coefficient, if the predicted temperature is lower than the lower limit of the preset temperature range, the total compensation power should be increased to avoid insufficient temperature in the future. Therefore, the undertemperature correction coefficient needs to be greater than 1.

[0088] Based on this Satisfying the relation:

[0089] ;

[0090] in, It is a curing oven Over-temperature correction factor at all times It is a minimum value function. This is a preset undertemperature correction factor, used to limit the upper limit of power adjustment and avoid excessive power enhancement leading to overheating. It can be set to 1.5 or adjusted according to needs. The undertemperature compensation coefficient can be set to [value missing]. Within this range, it is possible to avoid overly aggressive corrections that could cause new problems, and to make power adjustments more stable. It is a curing oven Predicted temperature at any time It is the lower limit of the preset temperature range. It is the preset target temperature of the curing oven.

[0091] The previous section explained how to anticipate and address the delay characteristics of the curing oven through time-based prediction and correction. Next, we will discuss the heating power allocation strategy from a spatial perspective.

[0092] It should be noted that in traditional curing oven control systems, all heaters are driven and regulated with a uniform power, without considering the uneven temperature distribution within the oven. Especially during the feeding stage, a large number of cold workpieces enter from the inlet, absorbing heat from the surrounding environment and causing a significant drop in temperature in the inlet area. Traditional control systems cannot accurately identify the distribution of thermal disturbances and cannot flexibly adjust the heater power according to actual temperature changes. This results in a severe instantaneous temperature drop in the inlet area, affecting the curing effect of the workpieces. At the same time, the outlet area may experience overheating due to heat accumulation, which is also detrimental to the normal curing of the workpieces.

[0093] Specifically, this invention implements zoned control of the curing oven: the oven cavity is divided into three independent heating zones along the conveying direction: an inlet zone, a central zone, and an outlet zone. Each zone is equipped with an independent heating module and a temperature sensor array, allowing for the allocation of different heating powers to each zone. In other words, when applying compensation power, precise heating is achieved by assigning different weights to each zone. The weight values ​​can be set by the implementers according to requirements. This invention takes into account the characteristics of each area: the inlet zone, due to concentrated cold disturbances, requires priority compensation, and its weight is set to [value missing]. The central region prioritizes maintaining steady state, ensuring thermal stability and uniformity, with a weight set to [value missing]. To avoid heat buildup in the export area, the weight is set to... .

[0094] The method of the present invention has completed a full control cycle and outputs a set of highly intelligent heating control commands that have been time-predicted and space-optimized, thereby enabling the temperature of the curing chamber to be accurately maintained within the target range even under severe feeding disturbances.

[0095] The second aspect of this embodiment provides a plastic part spraying control system, such as... Figure 2 As shown, the plastic part spraying control system includes a memory and a processor. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the plastic part spraying control method of the first aspect of the present invention is implemented.

[0096] The plastic parts spraying control system also includes other components well known to those skilled in the art, such as communication buses and communication interfaces, the settings and functions of which are known in the art and will not be described in detail here.

[0097] In this invention, the aforementioned memory can be any tangible medium containing or storing a program that can be used or combined with an instruction execution system, apparatus, or device. For example, a computer-readable storage medium can be any suitable magnetic or magneto-optical storage medium, such as resistive random access memory (DRAM), dynamic random access memory (DRAM), static random access memory (SRAM), enhanced dynamic random access memory (DRAM), high-bandwidth memory, hybrid memory cube, etc., or any other medium that can be used to store desired information and can be accessed by an application, module, or both. Any such computer storage medium can be part of a device or accessible to or connected to a device.

[0098] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the spraying of plastic parts, characterized in that, Including the following steps: After detecting that the temperature of the curing oven has reached the preset target temperature, a feeding event is triggered; Acquire at least one physical parameter related to the feeding event and acquire the current measured temperature of the curing oven. Based on the at least one physical parameter, calculate a first power value for feedforward compensation of the thermal disturbance caused by the feeding event, including: superimposing at least two physical models: a model characterizing the endothermic effect caused by the material entering the curing oven; a model characterizing the heat dissipation effect caused by the opening of the curing oven; and a model characterizing the heat transfer effect caused by the material conveying system. Based on the first power value, the current measured temperature, and the preset target temperature, the total compensation power for the curing oven is determined; Generating and outputting a heating control command corresponding to the total compensation power includes: predicting the predicted temperature at a future time point based on the total compensation power and the current measured temperature, and in combination with a preset power-temperature conversion coefficient; correcting the total compensation power based on the comparison result between the predicted temperature and the preset temperature range to obtain the final compensation power; and generating and outputting a heating control command based on the final compensation power. The predicted temperature at a future time point includes: calculating the ratio of a preset predicted time step to the heating inertia time constant characterizing the thermodynamic properties of the curing oven, taking the negative value of the exponential function, subtracting the exponential function value from 1 to obtain the heating inertia coefficient; multiplying the preset power-temperature conversion coefficient by the total compensation power, and then multiplying by the heating inertia coefficient to obtain the temperature change; and using the sum of the current measured temperature and the temperature change as the predicted temperature at the future time point. The total compensation power is corrected, including: When the predicted temperature is higher than the upper limit of the preset temperature range, the total compensation power is adjusted downward by an over-temperature correction coefficient less than 1 and inversely proportional to the difference between the predicted temperature and the upper limit. When the predicted temperature is lower than the lower limit of the preset temperature range, the total compensation power is adjusted upward by an under-temperature correction coefficient greater than 1 and proportional to the difference between the predicted temperature and the lower limit.

2. The method for controlling the spraying of plastic parts according to claim 1, characterized in that, Determining the total compensation power for the curing oven includes: The first power value is added to the feedback power value to obtain the total compensation power of the curing oven; The feedback power value is proportional to the difference between the current measured temperature and the preset target temperature.

3. The method for controlling the spraying of plastic parts according to claim 1, characterized in that, The physical parameters include at least one of the following: the quantity of material to be processed entering the curing oven per unit time, the opening status parameters of the curing oven, and the conveying speed of the material to be processed.

4. The method for controlling the spraying of plastic parts according to claim 1, characterized in that, The model used to characterize the endothermic effect caused by the entry of the material to be processed into the curing oven includes: the product of the endothermic power coefficient of a single material to be processed and the number of materials to be processed entering the curing oven at the current moment is recorded as the material endothermic power component. The model used to characterize the heat dissipation effect caused by the opening of the curing oven is as follows: calculate the difference between the measured temperature of the curing oven at the current moment and the ambient temperature, and then multiply it by the heat dissipation coefficient per unit area of ​​the curing oven and the opening area at the current moment to obtain the heat dissipation power component of the oven body. The model used to characterize the heat transfer effect caused by the material conveying system is as follows: the difference between the measured temperature of the curing oven at the current moment and the initial temperature of the material to be processed is calculated, and then multiplied by the heat transfer coefficient per unit velocity of the material to be processed and the conveying speed at the current moment to obtain the heat transfer power component of the material.

5. The method for controlling the spraying of plastic parts according to claim 1, characterized in that, The heating control command includes: For the sub-control commands of multiple preset zones set along the material conveying direction in the curing oven, the method further includes decomposing the total compensation power into sub-power values ​​corresponding to each preset zone according to a non-uniform distribution strategy, wherein the weight of the sub-power value allocated to the inlet zone is higher than the weight allocated to other zones.

6. A plastic parts spray coating control system, characterized in that, The plastic part spraying control system includes a processor and a memory. The memory stores computer program instructions, which, when executed by the processor, implement a plastic part spraying control method according to any one of claims 1-5.

Images