Electric gravure color reproduction quality inspection and control
2018-04-15 08:00:38
Electric Carving Intaglio Color Restoration Quality Inspection and Control In the printing industry, after a long period of practice, people realized that only in the entire printing process, data management, quantitative control of printing quality can adapt to the rapid development of the current printing technology needs. At present, it has long been widely used in offset printing to control printing and plate making (stencil printing). The test signal bar, test strips and control strips are used in raw cotton samples and formal printing to detect color marks or control on blank prints. Bar, etc., through the test instruments and charts, the scientific quantitative control of the field density, dot gain, neutral gray, tone, print uniformity, resolution, and clarity of four-color printing. The method of printing data from plate-to-plate printing is adopted, and a large number of actual data are collected by Cheng Cheng. A series of best data is selected as the basis for process implementation and quality management. This has played a significant role in offset color management and control.
However, in gravure color printing, especially in electric engraving and gravure printing, there is no continuous and complete quantitative control system during the entire process from platemaking to printing. In printing, most of the time, the operator will use colored manuscripts, The gravure proofs of the plate-making factory are compared with the printing factory, relying on the subjective visual evaluation to evaluate the color reproduction of the plate. There are many drawbacks to this approach. One is that gravure pre-proofing of the plate-making factory is the same as the formal printing of the printing factory, and there is a big difference in the process. As far as the current situation of proofing technology is concerned, it is difficult to simulate the effect of formal printing. It is difficult to determine the color reproduction quality of the printed samples. It is still necessary to print on the machine; the second is the proofing conditions of the plate making factory and the printing of the printing house. Large differences in terms may require longer printing and debugging time to catch up with or approach the gravure proofing effect of the plate making plant, resulting in a greater waste of printed materials. Third, it is impossible to do volume analysis for the restoration of color tonality. The increase in dot gain can not be detected. Fourth, the surface wear of the printing plate can not be tracked and detected during the printing process. The change of dot value can not be used to transfer the ink on the printing plate. The fifth is the serial printing plate and reprinting. Edition cannot effectively control and manage the consistency of printing effects. Therefore, the gravure printing should also be like the offset color control, in the blank of the printing, for example, directly under the mark line, or elsewhere, placing test blocks or test strips without affecting the printing patterns and print registration. To detect and control color reproduction during the entire plate making and printing process. This article attempts to propose the addition of test strips in the detection and control of color reproduction of electric carvings and gravure, so that it can be standardized and standardized, and it is hoped that it can be discussed together with peers of the concave printing factory and the plate making factory.
In fact, a very strict quality control system has been established at the gravure platemaking and printing plants. However, the printing plant is not very clear about the plate making process of the plate making plant. The printing plant of the plate making plant also lacks the printing process. Necessary understanding and understanding. Therefore, color detection and control of gravure color printing is a common research topic for platemaking plants and printing plants. The reduction control of color printing runs through the entire process of plate making and printing. Both parties should strengthen mutual understanding and cooperation to ensure that color control can go from platemaking to printing. Continuity of printing, not only tie the gravure proofing to connect the plate to print the entire process, concave must carry the necessary color control information.
I. Determination and Control of Printing Characteristic Curve After the gravure printing plate of the electric engraving gravure printing plate is screened, the mesh type, and the electronic engraving are level curves, the engraving value of the halftone dot is determined, and the ink content of each step of the ashtray on the printing plate is determined. Down. In other words, under certain printing conditions, the printing properties of the plate cylinder are also determined at the same time. We know that in the mathematics surface service standard system, any two points can determine a straight line, that is, to determine a curve, at least three or more points. Therefore, usually when we measure the printing characteristic curve, considering that we can not place more test blocks or color marks on the plate cylinder, we usually place 4-5 step scales and measure the density value of each step on the ladder scale. It is possible to approximate and delineate the printing characteristics of the printing plate. For example, 5%, 25%, 50%, 75%, 100%, etc. 5 step scales can be set on each color plate cylinder.
Printing plants and plate-making plants can work out the printing densities of these five official printings, as well as the density values ​​of the proofing machine. The formulation of the printing network of the plate making plants is very important. The engraving process parameters must be printed by the printing house. Based on the results, it is necessary to meet the printing factory's characteristics. The engraving process parameters of the electric engraving machine need to be calibrated with the printing samples to be determined. In other words, the tone reduction of color is based on the final result of the printing factory. In the process of printing and proofing, by detecting the density value of each level of the step scale, and comparing with the standard value, we can know whether the printing property of the printing plate is normal or not. We can also judge whether the printing plate and plate proofing are qualified or not. Whether the separation is accurate, whether the gravure conversion matches, and so on.
Second, the measurement of the ruler's dot value The engraving of the ruler on the printing plate is normal. It can directly reflect the normality of the restoring of the color tone. Only the value of the dot of each ladder is slow and normal, so as to ensure that the correct printing conditions are correct. The color tone reduction. The electro engraving operator and quality management personnel of the plate-making factory can detect the dot value of each level of the step scale and determine whether the engraving value of the printing plate dot is normal. Because the engraving characteristics of the engraving head of the electric engraving machine can be described by a linear curve, as long as the engraving values ​​of two points are defined, it is possible to determine the engraving characteristic curve of the engraving head of the electric engraving machine. Therefore, in the process of electronic engraving platemaking, it is possible to preliminarily test the values ​​of the highlight and darkened halftone dots. After these two values ​​are determined, the engraving characteristics of the engraving head of the electric engraving machine can be determined. However, the engraving value of the engraving head of the electric engraving machine will become smaller, the ink content will decrease, and the tone reduction will be deviated. With a ruler, you can monitor the wear of the engraving needle. For example, in the case of Nanhai City's platemaking center in a calendar calendar, it was found that the magenta plate was not well transferred and the sample was color-reversed when it was notched. However, the trial carving values ​​of the magenta plate were normal. Found that the engraving needle wear.
If there is a ruler in the plate, the problem of engraving pin abrasion can be easily found by checking the screen engraving values ​​of the middle steps of the ladder. Most printing companies in Rui are not equipped with dot network measurement protocols, they cannot detect the dot engraving of the printing plate, follow the surface condition of the printing plate in the printing process, and quantitatively analyze the changes in the dot network due to wear. Therefore, in order to control the color tone reduction, the printing factory should not only be equipped with a density meter, but also should be equipped with a dot meter. With density meters and dot-measuring machines, quality control and inspection of plates can be performed. Through the data analysis of the print and print foot print data of the printing factory, it is also possible to repeatedly calibrate the carving process of the engraving factory and select the best electric carving process parameters.
Third, the determination of small outlets in the high-light area The determination of the small spots in the high-light areas of various colors is the focus of platemaking. Human vision reflects most of the perception of high-level images, which can also be reflected in the print characteristic curve. The appropriateness of the development of small outlets in high light areas directly affects the restoration of medium and high-profile levels. If the value of the high light value is set to a low value, in the printing, pixels in the high-light portion of the image are lost, and although the ink concentration may be increased, the density of the dark tone may be too large to cause color cast. If the high light value is set high, it is also likely to cause changes in the image tone, resulting in loss of dark tone levels. Therefore, the small dot value of the highlight area should be matched with the dark tone dot value so as to avoid the problem of high or low tone in the printing. The 5% dot value in the five-step ladder can detect whether the highlight dot engraving value is normal. In the formal printing of the printing factory, if the highlight transfer is not normal, it is necessary to use a dot-measuring device first to check whether the high-light dot value of the printing plate is normal.
Fourth, the standardization of gravure printing is very important because it directly affects the quality of the proofs. It is closely related to the solidity of the outlets, the clearness of the level, and the fluctuation of neutral gray. For example, if the printing dots increase by 10%, then the dark tone dots of the color version are 100%-10%=90%. If the printing dots increase by 20%, the dark tone dots of each color can only extend to 80%, and the printing dots increase. The more it is, the more shaded outlets of various colors are compressed, the darker and more severe. In addition, in the printing process, as long as the first color is printed, the color balance relationship of the three primary colors is determined, and then the density of the overprinted color does not match the previous color density, the neutral gray will fluctuate, and the printed matter will be biased. color. Therefore, in the proofing and printing, the density of the ink and the dark density must be clearly defined. Of course, the hue of the ink used by the platemaking and printing plants must be the same or very close, and the substrates should be the same. In short, the printing conditions should be as close as possible.
Simply controlling the tone reduction of primary colors is not enough for color control. If the printing position of the printing plate permits, a neutral gray test unit and a two-color tricolor superimposition unit for detecting the color superimposition effect should be added in the test block, and the control of the color reproduction is further improved.
In short, through the measurement and control of the density and the dot of the five-step ladder, as well as the control of the neutral and overprinting, the color reproduction of the gravure plate can be ensured. After the plate quality is stable, the five-step ladder can be reduced to three steps, for example, 20%, 50%, and 100%. By monitoring the density and dot value of the 3 step scale, it is also possible to control the plate quality and gravure proofs. The location can be set aside for other test blocks, adding more reference and control information to the print.
However, in gravure color printing, especially in electric engraving and gravure printing, there is no continuous and complete quantitative control system during the entire process from platemaking to printing. In printing, most of the time, the operator will use colored manuscripts, The gravure proofs of the plate-making factory are compared with the printing factory, relying on the subjective visual evaluation to evaluate the color reproduction of the plate. There are many drawbacks to this approach. One is that gravure pre-proofing of the plate-making factory is the same as the formal printing of the printing factory, and there is a big difference in the process. As far as the current situation of proofing technology is concerned, it is difficult to simulate the effect of formal printing. It is difficult to determine the color reproduction quality of the printed samples. It is still necessary to print on the machine; the second is the proofing conditions of the plate making factory and the printing of the printing house. Large differences in terms may require longer printing and debugging time to catch up with or approach the gravure proofing effect of the plate making plant, resulting in a greater waste of printed materials. Third, it is impossible to do volume analysis for the restoration of color tonality. The increase in dot gain can not be detected. Fourth, the surface wear of the printing plate can not be tracked and detected during the printing process. The change of dot value can not be used to transfer the ink on the printing plate. The fifth is the serial printing plate and reprinting. Edition cannot effectively control and manage the consistency of printing effects. Therefore, the gravure printing should also be like the offset color control, in the blank of the printing, for example, directly under the mark line, or elsewhere, placing test blocks or test strips without affecting the printing patterns and print registration. To detect and control color reproduction during the entire plate making and printing process. This article attempts to propose the addition of test strips in the detection and control of color reproduction of electric carvings and gravure, so that it can be standardized and standardized, and it is hoped that it can be discussed together with peers of the concave printing factory and the plate making factory.
In fact, a very strict quality control system has been established at the gravure platemaking and printing plants. However, the printing plant is not very clear about the plate making process of the plate making plant. The printing plant of the plate making plant also lacks the printing process. Necessary understanding and understanding. Therefore, color detection and control of gravure color printing is a common research topic for platemaking plants and printing plants. The reduction control of color printing runs through the entire process of plate making and printing. Both parties should strengthen mutual understanding and cooperation to ensure that color control can go from platemaking to printing. Continuity of printing, not only tie the gravure proofing to connect the plate to print the entire process, concave must carry the necessary color control information.
I. Determination and Control of Printing Characteristic Curve After the gravure printing plate of the electric engraving gravure printing plate is screened, the mesh type, and the electronic engraving are level curves, the engraving value of the halftone dot is determined, and the ink content of each step of the ashtray on the printing plate is determined. Down. In other words, under certain printing conditions, the printing properties of the plate cylinder are also determined at the same time. We know that in the mathematics surface service standard system, any two points can determine a straight line, that is, to determine a curve, at least three or more points. Therefore, usually when we measure the printing characteristic curve, considering that we can not place more test blocks or color marks on the plate cylinder, we usually place 4-5 step scales and measure the density value of each step on the ladder scale. It is possible to approximate and delineate the printing characteristics of the printing plate. For example, 5%, 25%, 50%, 75%, 100%, etc. 5 step scales can be set on each color plate cylinder.
Printing plants and plate-making plants can work out the printing densities of these five official printings, as well as the density values ​​of the proofing machine. The formulation of the printing network of the plate making plants is very important. The engraving process parameters must be printed by the printing house. Based on the results, it is necessary to meet the printing factory's characteristics. The engraving process parameters of the electric engraving machine need to be calibrated with the printing samples to be determined. In other words, the tone reduction of color is based on the final result of the printing factory. In the process of printing and proofing, by detecting the density value of each level of the step scale, and comparing with the standard value, we can know whether the printing property of the printing plate is normal or not. We can also judge whether the printing plate and plate proofing are qualified or not. Whether the separation is accurate, whether the gravure conversion matches, and so on.
Second, the measurement of the ruler's dot value The engraving of the ruler on the printing plate is normal. It can directly reflect the normality of the restoring of the color tone. Only the value of the dot of each ladder is slow and normal, so as to ensure that the correct printing conditions are correct. The color tone reduction. The electro engraving operator and quality management personnel of the plate-making factory can detect the dot value of each level of the step scale and determine whether the engraving value of the printing plate dot is normal. Because the engraving characteristics of the engraving head of the electric engraving machine can be described by a linear curve, as long as the engraving values ​​of two points are defined, it is possible to determine the engraving characteristic curve of the engraving head of the electric engraving machine. Therefore, in the process of electronic engraving platemaking, it is possible to preliminarily test the values ​​of the highlight and darkened halftone dots. After these two values ​​are determined, the engraving characteristics of the engraving head of the electric engraving machine can be determined. However, the engraving value of the engraving head of the electric engraving machine will become smaller, the ink content will decrease, and the tone reduction will be deviated. With a ruler, you can monitor the wear of the engraving needle. For example, in the case of Nanhai City's platemaking center in a calendar calendar, it was found that the magenta plate was not well transferred and the sample was color-reversed when it was notched. However, the trial carving values ​​of the magenta plate were normal. Found that the engraving needle wear.
If there is a ruler in the plate, the problem of engraving pin abrasion can be easily found by checking the screen engraving values ​​of the middle steps of the ladder. Most printing companies in Rui are not equipped with dot network measurement protocols, they cannot detect the dot engraving of the printing plate, follow the surface condition of the printing plate in the printing process, and quantitatively analyze the changes in the dot network due to wear. Therefore, in order to control the color tone reduction, the printing factory should not only be equipped with a density meter, but also should be equipped with a dot meter. With density meters and dot-measuring machines, quality control and inspection of plates can be performed. Through the data analysis of the print and print foot print data of the printing factory, it is also possible to repeatedly calibrate the carving process of the engraving factory and select the best electric carving process parameters.
Third, the determination of small outlets in the high-light area The determination of the small spots in the high-light areas of various colors is the focus of platemaking. Human vision reflects most of the perception of high-level images, which can also be reflected in the print characteristic curve. The appropriateness of the development of small outlets in high light areas directly affects the restoration of medium and high-profile levels. If the value of the high light value is set to a low value, in the printing, pixels in the high-light portion of the image are lost, and although the ink concentration may be increased, the density of the dark tone may be too large to cause color cast. If the high light value is set high, it is also likely to cause changes in the image tone, resulting in loss of dark tone levels. Therefore, the small dot value of the highlight area should be matched with the dark tone dot value so as to avoid the problem of high or low tone in the printing. The 5% dot value in the five-step ladder can detect whether the highlight dot engraving value is normal. In the formal printing of the printing factory, if the highlight transfer is not normal, it is necessary to use a dot-measuring device first to check whether the high-light dot value of the printing plate is normal.
Fourth, the standardization of gravure printing is very important because it directly affects the quality of the proofs. It is closely related to the solidity of the outlets, the clearness of the level, and the fluctuation of neutral gray. For example, if the printing dots increase by 10%, then the dark tone dots of the color version are 100%-10%=90%. If the printing dots increase by 20%, the dark tone dots of each color can only extend to 80%, and the printing dots increase. The more it is, the more shaded outlets of various colors are compressed, the darker and more severe. In addition, in the printing process, as long as the first color is printed, the color balance relationship of the three primary colors is determined, and then the density of the overprinted color does not match the previous color density, the neutral gray will fluctuate, and the printed matter will be biased. color. Therefore, in the proofing and printing, the density of the ink and the dark density must be clearly defined. Of course, the hue of the ink used by the platemaking and printing plants must be the same or very close, and the substrates should be the same. In short, the printing conditions should be as close as possible.
Simply controlling the tone reduction of primary colors is not enough for color control. If the printing position of the printing plate permits, a neutral gray test unit and a two-color tricolor superimposition unit for detecting the color superimposition effect should be added in the test block, and the control of the color reproduction is further improved.
In short, through the measurement and control of the density and the dot of the five-step ladder, as well as the control of the neutral and overprinting, the color reproduction of the gravure plate can be ensured. After the plate quality is stable, the five-step ladder can be reduced to three steps, for example, 20%, 50%, and 100%. By monitoring the density and dot value of the 3 step scale, it is also possible to control the plate quality and gravure proofs. The location can be set aside for other test blocks, adding more reference and control information to the print.