A method for coordinating control of gravure squeegee pressure and ink amount

Abstract

The application discloses a concave printing doctor blade pressure and ink amount coordination control method, relates to the technical field of gravure printing, and comprises the following steps: step one: viscosity reference value η0, pressure reference value P0, flow reference value Q0 and density reference value D0 are obtained by calculating the average value of each parameter in 360 groups of data; and viscosity fluctuation amplitude characteristic value σ and viscosity change rate characteristic value Δη are obtained by analyzing viscosity data; through double condition quantitative judgment of the viscosity fluctuation amplitude characteristic value σ and the change rate characteristic value Δη, automatic detection can be realized when an abnormality just occurs, and coordinated adjustment of pressure and flow can be completed within a few seconds, so that the generation of a large amount of waste products is effectively prevented; through calibration of a pressure adjustment coefficient, an optimal viscosity, a flow adjustment coefficient and a pressure-flow coupling factor, linear automatic compensation of pressure according to viscosity, quadratic automatic compensation of flow according to viscosity deviation and coupling compensation of flow to pressure change are realized.

Description

Technical Field

[0001] This invention belongs to the field of gravure printing technology, specifically a method for coordinating and controlling the pressure of the gravure squeegee and the amount of ink. Background Technology

[0002] Gravure printing is a high-precision and high-efficiency printing method that is widely used for printing on substrates such as plastic film, paper, and metal foil. It occupies an important position in industries such as packaging, decoration, and electronics, and its printing quality directly affects the appearance quality of products.

[0003] However, existing technologies for controlling ink density stability during gravure printing typically rely on manual adjustments based on operator experience, often using a single parameter adjustment method. This involves either adjusting the doctor blade pressure or the ink flow rate separately. However, ink viscosity can dynamically change due to factors such as solvent evaporation and variations in ambient temperature and humidity, making single-parameter adjustment insufficient for precisely controlling ink density stability. Therefore, this paper proposes a method for coordinated control of gravure doctor blade pressure and ink volume. Summary of the Invention

[0004] The purpose of this invention is to provide a method for coordinating and controlling the pressure of a gravure printing squeegee and the amount of ink, so as to solve the problems mentioned in the background art.

[0005] A method for coordinating and controlling the pressure of a gravure printing doctor blade and the amount of ink includes: Step 1: During the first 30 minutes after the printing press has been running stably, data is collected every 5 seconds as a sampling period, and 360 sets of viscosity, pressure, flow rate and density are continuously recorded. By calculating the average value of each parameter in the 360 ​​sets of data, the viscosity reference value η0, pressure reference value P0, flow rate reference value Q0 and density reference value D0 are obtained. By analyzing the viscosity data, the viscosity fluctuation amplitude characteristic value σ and the viscosity change rate characteristic value Δη are obtained. Step 2: Fix the printing speed of the gravure printing machine to 80 meters per minute and the ink flow rate to the reference value Q0. Adjust the ink viscosity to multiple different levels. For each viscosity level, adjust the doctor blade cylinder pressure to stabilize the ink density within the target range of 1.40 to 1.44. Record the corresponding doctor blade pressure values. Select the pressure corresponding to the reference viscosity as the reference point to calculate the viscosity and pressure changes of other data. With the viscosity change as the abscissa and the pressure change as the ordinate, use the least squares method to perform linear fitting on the data pair of viscosity and pressure changes to obtain the pressure adjustment coefficient Kp. Then, establish a pressure control formula that the required pressure is equal to the algebraic sum of the products of the pressure reference value P0, the pressure adjustment coefficient Kp, and the difference between the current viscosity η and the viscosity reference value η0. Step 3: Fix the printing speed and adjust the doctor blade pressure to 80 meters per minute. Adjust the ink supply flow rate for multiple viscosity levels to keep the ink density stable and record the corresponding flow rate values. Find the viscosity value corresponding to the lowest flow rate requirement as the optimal viscosity ηb. Define the difference between the current viscosity and the optimal viscosity as the viscosity deviation. Use a quadratic function model to fit and obtain the flow rate adjustment coefficient Kq. Then establish a basic flow rate control formula where the required flow rate is equal to the algebraic sum of the products of the flow rate reference value Q0, the flow rate adjustment coefficient Kq, and the square of the viscosity deviation. Step 4: Fix the printing speed and keep the viscosity constant at the optimal viscosity ηb. Manually change the doctor blade pressure to multiple levels and adjust the ink supply flow to keep the ink density stable. Use the least squares method to perform linear fitting on the data of pressure change and flow deviation to obtain the pressure-flow coupling factor Kpq. Then, establish a complete flow control formula that is equal to the algebraic sum of the product of the flow reference value Q0, the flow adjustment coefficient Kq and the square of the viscosity deviation, and the algebraic sum of the product of the pressure-flow coupling factor Kpq and the difference between the current pressure P and the pressure reference value P0. Step 5: Collect viscosity, pressure, flow rate, and density data every 5 seconds to calculate the viscosity change rate. Identify any viscosity anomalies. When viscosity fluctuates abnormally, activate the coordination control program. Calculate the target pressure based on the pressure control formula and adjust the doctor blade pressure. Calculate the target flow rate based on the complete flow control formula and adjust the ink supply flow rate. After waiting for one density measurement cycle, check the ink density deviation. Fine-tune the flow rate or issue an alarm based on the deviation.

[0006] As a further aspect of the present invention, the specific method for obtaining the viscosity fluctuation amplitude characteristic value σ is as follows: The 360 ​​sets of viscosity data were divided into 6 time periods. The standard deviation of the viscosity data in each time period was calculated, and the average of the 6 standard deviations was used as the characteristic value σ of viscosity fluctuation amplitude.

[0007] As a further aspect of the present invention, the specific method for obtaining the viscosity change rate characteristic value Δη is as follows: Calculate the difference between the average viscosity values ​​of two adjacent time periods in the six time periods, and take the average of the absolute values ​​of the five differences as the characteristic value Δη of the viscosity change rate.

[0008] As a further aspect of the present invention, the specific method for obtaining the pressure adjustment coefficient Kp is as follows: The numerator is obtained by multiplying the number of data points by the sum of the products of all horizontal coordinates and their corresponding vertical coordinates, and then subtracting the sum of the products of all horizontal coordinates and their corresponding vertical coordinates. The denominator is obtained by multiplying the number of data points by the sum of the squares of all horizontal coordinates and then subtracting the square of the sum of the squares of all horizontal coordinates. The numerator is then divided by the denominator to obtain the pressure adjustment coefficient Kp.

[0009] As a further aspect of the present invention, the specific method for obtaining the flow adjustment coefficient Kq is as follows: The sum of the products of the squares of the viscosity deviations and the corresponding changes in flow rate in multiple sets of data is divided by the sum of the fourth power of the viscosity deviations, and the result is used as the flow rate adjustment coefficient Kq.

[0010] As a further aspect of the present invention, the specific method for obtaining the pressure-flow coupling factor Kpq is as follows: Under the condition that the ink viscosity is constant at ηb, the pressure is changed, and multiple sets of pressure-flow data are converted into a correspondence between pressure change and flow deviation. Linear fitting is performed with pressure change as the abscissa and flow deviation as the ordinate, and the slope of the fitted line is obtained as Kpq.

[0011] As a further aspect of the present invention, the specific method for judging viscosity anomalies is as follows: When the absolute value of viscosity deviating from the baseline value is greater than 3 times the fluctuation characteristic value σ and the viscosity change rate is greater than 2 times the rate characteristic value Δη, it is judged as viscosity anomaly.

[0012] As a further aspect of the present invention, the specific method for calculating the viscosity change rate is as follows: The viscosity change rate is calculated by dividing the absolute value of the difference between the viscosity value in the current sampling period and the viscosity value in the previous sampling period by 5 seconds.

[0013] As a further aspect of the present invention, the specific method for fine-tuning the flow rate or issuing an alarm based on the deviation is as follows: After a density measurement is completed every 30 seconds, if the absolute value of the ink density deviation is less than or equal to 0.02, the current flow rate remains unchanged; if the absolute value of the density deviation is between 0.02 and 0.05, the flow rate adjustment is set to the density deviation value multiplied by 5 liters per hour for fine adjustment; if the absolute value of the density deviation is greater than 0.05, an alarm signal is issued to prompt the operator to intervene.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention, through dual-condition quantitative judgment of viscosity fluctuation amplitude characteristic value σ and change rate characteristic value Δη, can automatically detect anomalies as soon as they occur and complete the coordinated adjustment of pressure and flow rate within seconds, effectively preventing the generation of large quantities of defective products. By calibrating the pressure adjustment coefficient, optimal viscosity, flow rate adjustment coefficient, and pressure-flow rate coupling factor, the originally vague empirical relationship between viscosity, pressure, and flow rate is transformed into a precise mathematical relationship. This achieves linear automatic compensation of pressure based on viscosity, secondary automatic compensation of flow rate based on viscosity deviation, and coupled compensation of flow rate to pressure changes, eliminating the subjectivity and inaccuracy of manual adjustment. Attached Figure Description

[0015] Figure 1This is a schematic diagram of the method framework structure of the present invention. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0017] Example 1: Please refer to Figure 1 This application provides a method for coordinated control of gravure printing blade pressure and ink volume, including: Step 1: During the first 30 minutes after the printing press has been running stably, data is collected every 5 seconds as a sampling cycle, and 360 sets of viscosity, pressure, flow rate and density are continuously recorded. The 360 ​​sets of viscosity, pressure, flow rate and density are analyzed to obtain the viscosity reference value η0, pressure reference value P0, flow rate reference value Q0 and density reference value D0. The first 30 minutes after the printing press is turned on and running stably are designated as the high-confidence period. During this 30-minute period, data is collected at a sampling cycle of 5 seconds. The 30 minutes contain a total of 360 sampling cycles, and 360 sets of complete data are continuously recorded. Each set of data includes four parameters: viscosity, pressure, flow rate, and density at the current moment. Analyzing these 360 ​​sets of data, we obtained the average values ​​of viscosity, pressure, flow rate, and density, which were respectively labeled as viscosity reference value η0, pressure reference value P0, flow rate reference value Q0, and density reference value D0. These four reference values ​​represent the normal operating status under the current printing conditions. The 360 ​​sets of viscosity data were evenly divided into 6 time periods in chronological order. Each time period contained 60 sets of data corresponding to a duration of 5 minutes. The 6 time periods were labeled as Time Period 1, Time Period 2, Time Period 3, Time Period 4, Time Period 5, and Time Period 6. For the 60 sets of viscosity data in each time period, the mean and standard deviation of that time period were calculated. The standard deviation was calculated by first calculating the difference between each value and the mean, then squaring the differences, summing them up, dividing by the number of data points (60), and finally taking the square root of the result. The standard deviation reflects the magnitude of the viscosity fluctuation within that time period. Six standard deviations were calculated for each of the 6 time periods. The average of these 6 standard deviations was labeled as the viscosity fluctuation amplitude characteristic value σ. This parameter quantifies the natural fluctuation amplitude of viscosity in the initial stable stage.

[0018] The viscosity average value for each time period is calculated to obtain the average value for 6 time periods. The difference between the average values ​​of two adjacent time periods is calculated to obtain 5 viscosity change values. The absolute values ​​of these 5 change values ​​are taken and averaged to obtain the viscosity change rate characteristic value Δη. This parameter quantifies the rate of viscosity change over time in the initial steady stage. These two viscosity fluctuation characteristic parameters, fluctuation σ and rate Δη, not only describe the current viscosity value, but more importantly, they describe the dynamic change characteristics of viscosity. The system obtains the initial printing speed V0, width W, target ink volume MM, cell ink capacity L, and ink density D. An online vibratory viscosity sensor is installed 100 mm from the bottom of the ink trough sidewall. This sensor's measurement range is set to 10 to 500 centipoise, covering the commonly used viscosity range of solvent-based gravure inks, and the sampling frequency is set to collect viscosity data every 2 seconds. A pressure sensor is installed on the doctor blade cylinder air inlet pipe, with a measurement range of 0 to 1 MPa and a sampling frequency of 10 pressure data acquisitions per second. An electromagnetic flow meter is installed on the ink supply pipe, with a measurement range of 0 to 300 liters per hour and a sampling frequency of once per second for flow rate data acquisition. An online spectrophotometer is installed 150 mm behind the printing unit, at a distance from the substrate surface. This device is driven by a servo motor to reciprocate along the printing width direction, with 7 fixed measurement points set along the width direction. A complete scan is completed every 30 seconds, and the arithmetic mean of the 7 measurement points is output as the current ink density value.

[0019] The printing speed V0 is read from the printing press speed sensor. The printing width W is a fixed mechanical parameter of the printing press. The target ink transfer volume MM is set by the process engineer according to the requirements of the printed material. The ink capacity L of the printing roller cell is obtained through theoretical calculation based on the geometric parameters such as the screen line count and cell depth of the printing roller. The ink density ρmo is obtained through actual measurement using a densitometer.

[0020] By using two parameters, σ and Δη, the fluctuation amplitude and rate of change of viscosity are quantified, transforming the judgment of anomalies from a vague qualitative assessment to a clear quantitative standard. This avoids misjudging normal fluctuations as anomalies, leading to excessive intervention, and also avoids misjudging abnormal changes as normal, leading to slow response. This provides a scientific and reliable monitoring basis for the entire control system.

[0021] Step 2: Fix the printing speed and ink flow rate of the gravure printing machine, and adjust the viscosity from the baseline value of 58 centipoise to five different viscosity levels: 40 centipoise, 50 centipoise, 60 centipoise, 70 centipoise, and 80 centipoise. For each viscosity level, adjust the pressure value of the doctor blade cylinder to keep the printed ink density between 1.40 and 1.44. Once the ink density stabilizes within this range, record the doctor blade pressure value at this time to obtain five sets of viscosity and pressure data pairs. Analyze these data to obtain the pressure adjustment coefficient Kp. Similarly, obtain the flow rate adjustment coefficient Kq and the optimal viscosity ηb. The printing speed of the gravure printing machine is fixed at 80 meters per minute and kept constant. The ink flow rate is fixed at the flow rate reference value Q0 and kept constant. Here, the viscosity of the ink is artificially adjusted by adding solvent to the ink or by heating to promote solvent evaporation, and the viscosity is adjusted from the reference value to five different viscosity levels. For each viscosity level, the pressure of the doctor blade cylinder was adjusted to maintain the printed ink density between 1.40 and 1.44. Once the ink density stabilized within this range, the doctor blade pressure was recorded. Stability was determined by a density fluctuation of no more than 0.01 over three consecutive minutes. Five sets of viscosity and pressure data were obtained. Using viscosity change as the x-axis and pressure change as the y-axis, a least squares method was used to linearly fit these five data points. The principle of the least squares method is to minimize the sum of the squared vertical distances between the fitted line and each data point. The slope was calculated by... The numerator is calculated by multiplying the quantity by the sum of the products of all x-coordinates and y-coordinates, and subtracting the sum of the products of all x-coordinates and y-coordinates. The denominator is calculated by multiplying the quantity by the sum of the squares of all x-coordinates and subtracting the square of the sum of the squares of all x-coordinates. The slope is equal to the numerator divided by the denominator. The slope of the fitted line is obtained by calculation and is marked as the pressure adjustment coefficient Kp. When the pressure adjustment coefficient is negative, it means that the pressure needs to be reduced when the viscosity increases and increased when the viscosity decreases. When the pressure adjustment coefficient is positive, it means that the pressure needs to be increased when the viscosity increases and decreased when the viscosity decreases.

[0022] By analyzing five sets of viscosity and pressure data, the pressure adjustment coefficient Kp is obtained. Then, the formula for calculating the required scraper pressure P when the current viscosity is η is obtained. The required pressure is equal to the algebraic sum of the products of the pressure reference value P0, the pressure adjustment coefficient Kp, and the difference between the current viscosity η and the viscosity reference value η0.

[0023] Under fixed printing speed and ink flow rate conditions, the ink viscosity was manually adjusted to multiple different levels. The optimal doctor blade pressure required to maintain the target ink density at each viscosity level was tested. The least squares method was used to linearly fit the data of viscosity change and pressure change, establishing a quantitative relationship model between viscosity and pressure and obtaining the pressure adjustment coefficient Kp. The positive and negative values ​​of the pressure adjustment coefficient Kp clearly indicate the direction of pressure adjustment. A negative value indicates that the pressure needs to be reduced when the viscosity increases, and a positive value indicates that the pressure needs to be increased when the viscosity increases. This realizes the intelligent control function of actively adjusting the pressure according to the viscosity change, eliminating the lag and inaccuracy of traditional manual adjustment.

[0024] Step 3: Obtain the optimal viscosity ηb and flow rate adjustment coefficient Kq by analyzing the viscosity and flow rate data; The printing speed of the gravure printing machine was fixed at 80 meters per minute and kept constant. The doctor blade pressure was adjusted according to the viscosity based on the relationship established in Part 2. That is, each viscosity level corresponds to its matching pressure value. For each viscosity level, the ink supply flow rate was adjusted to keep the ink density within the range of ±0.02 of the baseline value of 1.42. The stable flow rate value corresponding to each viscosity level was recorded to obtain 5 sets of viscosity and flow rate data pairs. Analyzing these five sets of viscosity and flow rate data, the viscosity value corresponding to the lowest flow rate demand is identified and marked as the optimal viscosity ηb. The current viscosity η minus the optimal viscosity ηb is taken as the viscosity deviation Δη. When the viscosity deviates from the optimal value, whether it is too high or too low, it will lead to an increase in flow rate demand. Therefore, the flow rate adjustment is proportional to the square of the viscosity deviation. Multiple sets of data are converted into data pairs of viscosity deviation and flow rate change. A quadratic function model is used for fitting. The flow rate change is set to equal the flow rate adjustment coefficient Kq multiplied by the square of the viscosity deviation. Multiple sets of data are substituted into the quadratic function model for fitting. The specific fitting method is to calculate the flow rate adjustment coefficient Kq using the least squares method. The calculation method is to divide the sum of the products of the square of the viscosity deviation and the flow rate change in multiple sets of data by the sum of the fourth power of the viscosity deviation. By analyzing five sets of viscosity and flow rate data, the optimal viscosity ηb and flow rate adjustment coefficient Kq are obtained. Then, the basic flow rate control formula is established as follows: the required flow rate is equal to the algebraic sum of the products of the flow rate reference value Q0, the flow rate adjustment coefficient Kq, and the square of the difference between the current viscosity η and the optimal viscosity ηb. Under the condition of fixed printing speed and adjustment of doctor blade pressure according to the relationship established in step two, the ink flow rate required to maintain the target ink density was tested at multiple viscosity levels. Through analysis, it was found that the flow rate demand showed a change pattern of first decreasing and then increasing. The optimal viscosity ηb corresponding to the lowest flow rate demand was determined. This viscosity point represents the best balance between ink flowability and transfer efficiency. A quadratic function flow rate adjustment model based on the square of viscosity deviation was established to obtain the flow rate adjustment coefficient Kq, realizing precise compensation control of flow rate with viscosity deviation.

[0025] Step 4: Obtain the pressure-flow coupling factor Kpq by analyzing the relationship between pressure change and flow deviation; In actual printing, changes in doctor blade pressure not only affect the ink scraping effect but also directly impact the amount of residual ink on the printing plate. Increased pressure enhances the doctor blade's scraping action on the plate, leading to a decrease in the amount of ink transferred to the substrate; conversely, decreased pressure increases the amount of residual ink on the plate. To maintain stable ink density, the ink flow rate must be adjusted accordingly. The printing speed of the gravure printing press is kept constant, and the ink viscosity is stably controlled at the optimal viscosity ηb. This viscosity is maintained by adding new ink or solvent to the ink tank. Based on this, multiple pressure levels are artificially adjusted to test the coupling relationship. For each pressure level, the ink flow rate is adjusted to keep the ink density within the target range. The stability criterion is that the density fluctuation does not exceed a certain range within 3 consecutive minutes. For pressures exceeding 0.01, the ink flow rate required to maintain the target density at each pressure level was recorded, resulting in multiple pressure-flow data pairs. Analysis of these data revealed a linear increase in flow rate demand with increasing pressure. The data was then converted into pressure change and flow rate deviation data pairs, where pressure change equals the current pressure minus the pressure baseline value P0, and flow rate deviation equals the current flow rate minus the flow baseline value Q0. Using pressure change as the x-axis and flow rate deviation as the y-axis, a least squares method was used to linearly fit these data points. The slope of the fitted line was calculated, and the pressure-flow coupling factor Kpq was defined as the amount of flow rate adjustment required for every 1 MPa change in pressure, expressed in liters per hour per MPa. By measuring the flow rate deviation and corresponding pressure change under multiple operating conditions, the pressure-flow coupling factor Kpq was calculated as the flow rate deviation divided by the pressure change; the slope of the fitted line was then denoted as the pressure-flow coupling factor Kpq.

[0026] By analyzing multiple sets of data pairs on pressure changes and flow deviations, the pressure-flow coupling factor Kpq is obtained. Furthermore, by analyzing the relationship between pressure changes and flow deviations, the pressure-flow coupling factor Kpq is obtained, leading to the complete formula for calculating the required ink supply flow rate Q when the current viscosity is η. The required flow rate is equal to the algebraic sum of the flow baseline value Q0 and the flow base adjustment amount, plus the algebraic sum of the flow coupling adjustment amount. The flow base adjustment amount is equal to the flow adjustment coefficient Kq multiplied by the square of the difference between the current viscosity η and the optimal viscosity ηb. The flow coupling adjustment amount is equal to the positive pressure-flow coupling factor Kpq multiplied by the difference between the current pressure P and the pressure baseline value P0. In other words, the complete flow control formula is: the required flow rate Q equals the flow baseline value Q0 plus the flow adjustment coefficient Kq multiplied by the square of the difference between the current viscosity η and the optimal viscosity ηb, plus the pressure-flow coupling factor Kpq multiplied by the difference between the current pressure P and the pressure baseline value P0.

[0027] Under the conditions of fixed printing speed and keeping the ink viscosity constant at the optimal viscosity, the ink flow rate required to maintain the target ink density at each pressure level was tested by manually changing the doctor blade pressure to multiple levels. A linear relationship model between pressure change and flow rate deviation was established, and the pressure-flow rate coupling factor Kpq was obtained. This coupling factor quantifies the magnitude of the flow rate adjustment required when the pressure changes by 1 MPa. It solves the technical problem of requiring synchronous flow rate compensation for changes in residual ink on the printing plate after adjusting the pressure alone, realizes coordinated control of pressure and flow rate, and eliminates the side effects of pressure adjustment on ink volume.

[0028] Step 5: Every 5 seconds is a control cycle. Real-time data are collected on the current ink viscosity η, doctor blade pressure P, ink flow rate Q, and ink density D. The viscosity change rate is calculated as the absolute value of the difference between the current viscosity and the viscosity of the previous cycle divided by 5 seconds. When abnormal viscosity fluctuations are detected, i.e., when the absolute value of the viscosity deviation from the baseline value is greater than 3 times the fluctuation characteristic value σ and the viscosity change rate is greater than 2 times the rate characteristic value Δη, the coordinated control program is started. Every 5 seconds constitutes a control cycle. The current ink viscosity η, doctor blade pressure P, ink flow rate Q, and ink density D are collected in real time. The viscosity change rate is calculated by dividing the absolute value of the difference between the current viscosity and the viscosity of the previous cycle by 5 seconds. When abnormal viscosity fluctuations are detected, i.e., when the absolute value of the viscosity deviation from the reference value is greater than 3 times the fluctuation characteristic value σ and the viscosity change rate is greater than 2 times the rate characteristic value Δη, the coordinated control program is activated.

[0029] First, the target scraper pressure P is calculated according to the pressure control formula. The target pressure is equal to the algebraic sum of the products of P0 and Kp and the difference between the current viscosity η and the viscosity reference value η0. The pressure is then adjusted to the target value by controlling the electric proportional valve of the scraper cylinder.

[0030] Two to three control cycles after pressure adjustment, the target ink supply flow rate Q is calculated according to the flow control formula. The target is equal to the algebraic sum of the product of Q0 and the flow adjustment coefficient Kq and the square of the difference between the current viscosity η and the optimal viscosity ηbest, and then the algebraic sum of the product of the pressure-flow coupling factor Kpq and the difference between the current pressure P and the pressure reference value P0. The flow rate is adjusted to the target value by controlling the speed of the frequency converter of the ink supply pump. After waiting 30 seconds to complete one density measurement cycle, check the ink density deviation. If the absolute value of the density deviation is less than or equal to 0.02, the control effect is good and the data acquisition step is returned to continue monitoring. If the absolute value of the density deviation is between 0.02 and 0.05, the flow rate is finely adjusted to be equal to the density deviation multiplied by 5 liters per hour. If the absolute value of the density deviation is greater than 0.05, an alarm signal is issued to prompt the operator to intervene.

[0031] A real-time coordinated control system was established, employing a 5-second control cycle for data acquisition and control judgment. Based on the viscosity fluctuation characteristic parameters σ and Δη obtained in step one, an abnormal fluctuation identification mechanism was established. When the absolute value of viscosity deviation from the benchmark value is greater than 3 times σ and the viscosity change rate is greater than 2 times Δη, the coordinated control program is activated. A hierarchical control strategy is adopted to first adjust the doctor blade pressure according to the pressure control formula. After the pressure adjustment is completed, the ink supply flow rate is adjusted according to the flow control formula 2 to 3 control cycles later, avoiding control oscillations caused by synchronous parameter changes. A density closed-loop feedback mechanism is used to verify and fine-tune the control effect in real time, ensuring that the ink density remains stable within the target range.

[0032] It achieves proactive pressure adjustment based on viscosity changes and dual compensation of flow rate considering both viscosity deviation and pressure changes, ensuring that ink density remains stable within the target range, effectively improving the automation control level and product quality stability of the gravure printing process.

[0033] By using dual-condition quantitative judgment of viscosity fluctuation amplitude characteristic value σ and change rate characteristic value Δη, anomalies can be automatically detected as soon as they occur, and pressure and flow rate can be coordinated and adjusted within seconds, effectively preventing the generation of large quantities of defective products. A complete mathematical model was established by calibrating key parameters such as the pressure adjustment coefficient Kp, optimal viscosity ηb, flow rate adjustment coefficient Kq, and pressure-flow coupling factor Kpq, realizing the transformation from experience-based adjustment to scientific control and eliminating the subjectivity and inaccuracy of manual adjustment. A pressure-flow coupling compensation mechanism was established; when viscosity changes, pressure is actively adjusted according to a linear relationship, and flow rate is double-compensated according to a quadratic function relationship and coupling relationship, ensuring that ink density remains stable within the target range. A graded control strategy of adjusting pressure first and then flow rate avoids control oscillations caused by synchronous parameter changes, improving system stability and reducing control response time to less than 60 seconds. Through density measurement feedback and fine-tuning optimization mechanisms, real-time verification and precise adjustment of control effects are achieved, improving print quality. This replaces the traditional manual experience-based adjustment mode, reduces operator dependence, significantly reduces the defect rate, and improves production efficiency and the level of automation control in the printing process.

[0034] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters and thresholds in the formulas are set by those skilled in the art according to the actual situation.

[0035] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for coordinating and controlling the pressure of a gravure printing blade and the amount of ink, characterized in that, include: Step 1: During the first 30 minutes after the printing press has been running stably, data is collected every 5 seconds as a sampling period, and 360 sets of viscosity, pressure, flow rate and density are continuously recorded. By calculating the average value of each parameter in the 360 ​​sets of data, the viscosity reference value η0, pressure reference value P0, flow rate reference value Q0 and density reference value D0 are obtained. By analyzing the viscosity data, the viscosity fluctuation amplitude characteristic value σ and the viscosity change rate characteristic value Δη are obtained. Step 2: Fix the printing speed of the gravure printing machine to 80 meters per minute and the ink flow rate to the reference value Q0. Adjust the ink viscosity to multiple different levels. For each viscosity level, adjust the doctor blade cylinder pressure to stabilize the ink density within the target range of 1.40 to 1.

44. Record the corresponding doctor blade pressure values. Select the pressure corresponding to the reference viscosity as the reference point to calculate the viscosity and pressure changes of other data. With the viscosity change as the abscissa and the pressure change as the ordinate, use the least squares method to perform linear fitting on the data pair of viscosity and pressure changes to obtain the pressure adjustment coefficient Kp. Then, establish a pressure control formula that the required pressure is equal to the algebraic sum of the products of the pressure reference value P0, the pressure adjustment coefficient Kp, and the difference between the current viscosity η and the viscosity reference value η0. Step 3: Fix the printing speed and adjust the doctor blade pressure to 80 meters per minute. Adjust the ink supply flow rate for multiple viscosity levels to keep the ink density stable and record the corresponding flow rate values. Find the viscosity value corresponding to the lowest flow rate requirement as the optimal viscosity ηb. Define the difference between the current viscosity and the optimal viscosity as the viscosity deviation. Use a quadratic function model to fit and obtain the flow rate adjustment coefficient Kq. Then establish a basic flow rate control formula where the required flow rate is equal to the algebraic sum of the products of the flow rate reference value Q0, the flow rate adjustment coefficient Kq, and the square of the viscosity deviation. Step 4: Fix the printing speed and keep the viscosity constant at the optimal viscosity ηb. Manually change the doctor blade pressure to multiple levels and adjust the ink supply flow to keep the ink density stable. Use the least squares method to perform linear fitting on the data of pressure change and flow deviation to obtain the pressure-flow coupling factor Kpq. Then, establish a complete flow control formula that is equal to the algebraic sum of the product of the flow reference value Q0, the flow adjustment coefficient Kq and the square of the viscosity deviation, and the algebraic sum of the product of the pressure-flow coupling factor Kpq and the difference between the current pressure P and the pressure reference value P0. Step 5: Collect viscosity, pressure, flow rate, and density data every 5 seconds to calculate the viscosity change rate. Identify any viscosity anomalies. When viscosity fluctuates abnormally, activate the coordination control program. Calculate the target pressure based on the pressure control formula and adjust the doctor blade pressure. Calculate the target flow rate based on the complete flow control formula and adjust the ink supply flow rate. After waiting for one density measurement cycle, check the ink density deviation. Fine-tune the flow rate or issue an alarm based on the deviation.

2. The method for coordinating and controlling the pressure of a gravure printing blade and the amount of ink according to claim 1, characterized in that, The specific method for obtaining the viscosity fluctuation amplitude characteristic value σ is as follows: The 360 ​​sets of viscosity data were divided into 6 time periods. The standard deviation of the viscosity data in each time period was calculated, and the average of the 6 standard deviations was used as the characteristic value σ of viscosity fluctuation amplitude.

3. The method for coordinating and controlling the pressure and ink volume of a gravure printing doctor blade according to claim 1, characterized in that, The specific method for obtaining the viscosity change rate characteristic value Δη is as follows: Calculate the difference between the average viscosity values ​​of two adjacent time periods in the six time periods, and take the average of the absolute values ​​of the five differences as the characteristic value Δη of the viscosity change rate.

4. The method for coordinating and controlling the pressure and ink volume of a gravure printing doctor blade according to claim 1, characterized in that, The specific method for obtaining the pressure adjustment coefficient Kp is as follows: The numerator is obtained by multiplying the number of data points by the sum of the products of all horizontal coordinates and their corresponding vertical coordinates, and then subtracting the sum of the products of all horizontal coordinates and their corresponding vertical coordinates. The denominator is obtained by multiplying the number of data points by the sum of the squares of all horizontal coordinates and then subtracting the square of the sum of the squares of all horizontal coordinates. The numerator is then divided by the denominator to obtain the pressure adjustment coefficient Kp.

5. The method for coordinating and controlling the pressure of a gravure printing blade and the amount of ink according to claim 1, characterized in that, The specific method for obtaining the flow adjustment coefficient Kq is as follows: The sum of the products of the squares of the viscosity deviations and the corresponding changes in flow rate in multiple sets of data is divided by the sum of the fourth power of the viscosity deviations, and the result is used as the flow rate adjustment coefficient Kq.

6. The method for coordinating and controlling the pressure and ink volume of a gravure printing blade according to claim 1, characterized in that, The specific method for obtaining the pressure-flow coupling factor Kpq is as follows: Under the condition that the ink viscosity is constant at ηb, the pressure is changed, and multiple sets of pressure-flow data are converted into a correspondence between pressure change and flow deviation. Linear fitting is performed with pressure change as the abscissa and flow deviation as the ordinate, and the slope of the fitted line is obtained as Kpq.

7. The method for coordinating and controlling the pressure of a gravure printing blade and the amount of ink according to claim 6, characterized in that, The specific method for judging viscosity anomalies is as follows: When the absolute value of viscosity deviating from the baseline value is greater than 3 times the fluctuation characteristic value σ and the viscosity change rate is greater than 2 times the rate characteristic value Δη, it is judged as viscosity anomaly.

8. The method for coordinating and controlling the pressure of a gravure printing blade and the amount of ink according to claim 7, characterized in that, The specific calculation method for viscosity change rate is as follows: The viscosity change rate is calculated by dividing the absolute value of the difference between the viscosity value in the current sampling period and the viscosity value in the previous sampling period by 5 seconds.

9. The method for coordinating and controlling the pressure and ink volume of a gravure printing doctor blade according to claim 1, characterized in that, The specific methods for fine-tuning the flow rate or issuing an alarm based on the deviation are as follows: After a density measurement is completed every 30 seconds, if the absolute value of the ink density deviation is less than or equal to 0.02, the current flow rate remains unchanged; if the absolute value of the density deviation is between 0.02 and 0.05, the flow rate adjustment is set to the density deviation value multiplied by 5 liters per hour for fine adjustment; if the absolute value of the density deviation is greater than 0.05, an alarm signal is issued to prompt the operator to intervene.

Images