- Detail

The amount of ink in the process of ink transfer means that the amount of ink in printing is related to the area of the plate surface or the surface of the substrate. Generally, the amount of ink in printing can be expressed by the weight of ink per unit area, that is, g/m2; It can also be expressed by the volume of ink per unit area, i.e. ml/m2; Through calculation, the ink layer thickness can also be used（ μ m) To express. The amount of ink on the printing plate before printing is called the amount of ink on the printing plate, which is represented by X; The amount of ink transferred to the surface of paper or other printing materials after printing is called the transferred ink amount, which is represented by y. x. The unit of y can be g/m2, or it can be used μ M

the ratio of transferred ink volume y to printing plate ink volume x, expressed in percentage, is called ink transfer rate, which is recorded as F, that is,

f= (y/x) × 100%... (1)

the ratio of the transferred ink amount y to the remaining ink amount X-Y on the printing plate after printing is called the ink transfer coefficient, which is recorded as e, that is,

e=y/(X-Y)... (2)

the transferred ink amount y is related to the printing plate ink amount x, that is, y is a function of X. Therefore, the ink transfer rate f and the ink transfer coefficient e are also functions of the printing plate ink volume X. If the analytical relationship between Y and X is known (or a set of data of X and Y is measured), and taking x as the abscissa and y, F, e as the ordinate respectively, Y-X, F-X, E-X curves can be made (or fitted); They are called ink transfer volume curve, ink transfer rate curve and ink transfer coefficient curve respectively

the influence of printing materials on the ink transfer rate f is obvious. Take coated paper and paper as examples, their ink transfer rate curves are shown in Figure 4. The two curves obtained under the same experimental conditions are quite different: the surface of coated paper is smooth and the absorption is poor. With the increase of printing plate ink volume x, the ink transfer rate initially increases rapidly, and then decreases rapidly after reaching the maximum value, and the convex peak of the curve is obvious; The surface of the paper is rough and the absorption is good. With the increase of X, the increase is slow, and the decrease is slow after reaching the maximum value. The curve shape is gentle, and the convex peak is not obvious

1. using ink preset parameters, we must eliminate interference conditions and determine the uncertain factors to the greatest extent. For example, determine the ink bucket capacity, such as the ink volume height, the temperature and humidity of the environment, the pH value of the fountain solution, the type of ink, paper and plate, the running speed of the machine, the condition of the machine, etc

among the above conditions, the condition control of the machine is the most difficult, so it is necessary to maintain the machine regularly, and a test is carried out after each maintenance. Of course, this test can sometimes be combined with actual production for inspection

2. Test the performance of current printing equipment when the printing conditions are determined. There are two main parameters to test this performance. On the one hand, it is to establish the functional relationship between the inking state of each ink area and the amount of ink required for JDF process to output graphic information. On the other hand, it is necessary to test the stability of printing under this working state. The functional relationship between the inking state of each ink area and the amount of ink required for the output of graphic and text information of JDF process can be effective only when the working state is stable. Otherwise, the measurement error will be caused by the influence of factors such as the residual ink in the last ink path before the test is started

to judge the rolling friction of printing quality, it is necessary to measure the field density, point increase rate, gray balance, printing contrast, whether the density of each ink area is uniform, etc. However, the judgment of printing stability requires sampling inspection of multiple samples, so as to evaluate through CP and CPK values. CP represents the stability of the printing process, that is, the fluctuation between the upper limit USL and the lower limit LSL. Through the density sampling measurement of multiple samples, the variance with the standard value is calculated, and the curve representing the printing stability is drawn (as shown in Figure 5). The CP value is calculated by the formula CP = (usl-lsl)/6s. Table 1 reflects the stability data of long and short printing

cpk = min[(USL mean)/3s, (mean LSL)/3s]

in this formula, mean represents the measured actual printing density. Generally speaking, the CP and CPK values of short printing are higher than those of long printing. CPK greater than 1.33 indicates good stability; CPK between 1 and 1.33 indicates acceptable; If it is lower than 1.0, the printing stability is not very good

3. According to the test of the printing working state results and the analysis of the printing output characteristics, the relationship between the parameter variables of ink transfer volume information such as ink, inkzonecalculationparams and inkzoneprofile output by JDF and the ink volume control state is established, and the relationship function library is established to provide the basis for realizing the best control of the printing working state and the ink preset

after mastering the above debugging methods, we can not only apply the ink volume control information of the mechanical testing equipment for testing the spring tension and compression experiment on the printing equipment that supports CIP3, but also apply the data on the equipment that previously did not support CIP3 function, so as to achieve a stable working state in the shortest ink regulation time

reprinted from: Guangdong Printing

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