JP7519866B2 - Ink key opening adjustment system for printing presses - Google Patents

Description

The present invention relates to an ink key opening adjustment system for a printing press.

In conventional printing machines, before printing, the openings of multiple ink keys on an ink fountain are set (preset) according to the image to be printed. The opening of each ink key is set using the image area ratio in the area of each ink key of the image to be printed and a pre-stored conversion curve that indicates the correlation between the image area ratio and the opening of the ink key. In ink key areas where the color tone (particularly the print density) of the printed matter is inappropriate when printing with the set opening of the ink key, the opening of the ink key is adjusted to match the color tone to the target value.

Furthermore, in conventional printing machines, information on the ink key opening and the image area ratio of the ink key area when the color tone of the printed matter matches the target value (when printing the OK sheet) can be obtained, and a new conversion curve can be created based on that information. The new conversion curve created in this way is more suitable, and if used in subsequent printing, it is said that the color tone will match more quickly (see, for example, Patent Document 1).

However, in image areas with a low image area ratio within a print image, due to various factors, the color tone of the print image may not match even if it is preset using the new conversion curve. In particular, if the print density exceeds the allowable range in an image area with a low image area ratio, a large amount of paper is required to reduce the print density to the allowable range by printing, resulting in the inconvenience of a significant increase in paper waste.

Patent No. 4395287

The present invention has been made to solve these problems, and its purpose is to provide an ink key opening adjustment system for a printing press that can prevent excessive print density in image areas with low image area ratios and reduce the occurrence of paper waste.

To achieve the above object, the ink key opening adjustment system of the printing machine according to the present invention is characterized by comprising: a data acquisition means for acquiring opening data of ink keys corresponding to a low image area ratio, which is an image area ratio set in an image region into which a print image is divided, when printing an OK sheet, the ink keys corresponding to a low image area ratio that is lower than a predetermined value; a correlation derivation means for deriving a correlation between the low image area ratio and the ink key opening based on the ink key opening data acquired by the data acquisition means; and a correction means for correcting the correlation derived by the correlation derivation means by multiplying the correlation by a coefficient that reduces the ink key opening.

According to the above configuration, the correlation derived by the correlation derivation means is corrected by multiplying it by a coefficient that reduces the ink key opening, thereby making it possible to reduce the ink key opening corresponding to an image area in the printing press where a low image area ratio is set. Therefore, in a printing press in which the ink key opening is adjusted using the system of the present invention, the print density value in an image area where a low image area ratio is set can be set to a value lower than the target value, and printing to reduce the print density value can be suppressed.

In addition, in the ink key opening adjustment system for a printing press according to the present invention, the coefficient may be set for each divided area into which the image area ratio is divided into small areas each having a predetermined range of values, and the coefficient may be set to be larger as the image area ratio of the divided area increases.

As described above, by setting a coefficient for each divided area into which the image area ratio is divided into small parts for each value in a predetermined range, and setting the coefficient so that it is larger as the image area ratio of the divided area increases, it is possible to further reduce the deviation in density difference between the print density value and the target value in image areas with low image area ratios.

The ink amount correction method for a printing machine according to the present invention is characterized by comprising a data acquisition step of acquiring ink key opening data during OK sheet printing for ink keys corresponding to image areas with low image area ratios in which the image area ratios set in the image areas into which a print image is divided are lower than a predetermined value, a correlation derivation step of deriving a correlation between the low image area ratios and the ink key openings based on the ink key opening data acquired in the data acquisition step, and a correction step of multiplying the correlation derived by the correlation derivation means by a coefficient that reduces the ink key openings.

According to the above configuration, the correlation derived in the correlation derivation step is corrected by multiplying it by a coefficient that reduces the ink key opening, thereby making it possible to reduce the ink key opening corresponding to an image area in the printing press where a low image area ratio is set. Therefore, in a printing press in which the ink key opening is adjusted using the system of the present invention, the print density value in an image area where a low image area ratio is set can be set to a value lower than the target value, and printing to reduce the print density value can be suppressed.

According to the present invention, by correcting the correlation derived by the correlation derivation means by multiplying it by a coefficient that reduces the ink key opening, it is possible to prevent the print density value from exceeding the limit in an image area with a low image area ratio. This makes it possible to provide an ink key opening adjustment system for a printing press that can reduce the occurrence of paper waste even in printed matter that has an image area with a low image area ratio.

FIG. 2 is a schematic side view of an ink supply section of a printing press. 3 shows a main flowchart for correcting the ink amount of a printing press. 13 is a sub-flowchart showing the creation of a second curve. 13 is a sub-flowchart showing a second curve creation post-processing. 11 is a graph showing ink key openings plotted using an approximation curve obtained by the least squares method. 11 is a graph showing ink key openings plotted using points of a base curve in a section where plots are lacking. 13 is a graph showing ink key openings in which plots are insufficient and plotted without using points from the original curve. FIG. 2 is a control block diagram according to the present invention.

Below, we will explain the ink key opening adjustment system for a printing press according to one embodiment of the present invention with reference to the drawings.

Figure 1 shows the ink supply section installed inside the printing unit that performs printing in a printing press.

In Fig. 1, the ink fountain roller 1, which is supplied with ink from an ink fountain, rotates counterclockwise in the figure and supplies ink to a group of multiple ink rollers 3 located downstream via an ink call roller 2. The ink call roller 2, which is not shown in detail, reciprocates so that it can come into contact with and separate from the ink fountain roller 1 and the traverse roller 4. That is, when the ink call roller 2 is in contact with the ink fountain roller 1, the ink call roller 2 is separated from the traverse roller 4. This reciprocating motion is also called the ink call operation, and the more ink is called, the more ink is supplied to the group of ink rollers 3. In addition, the ink key K of the ink fountain slides in the direction of the arrow S to come into contact with and separate from the ink fountain roller 1, and the more the ink key K is separated from the ink fountain roller 1, the larger the opening of the ink key K becomes, and a large amount of ink is supplied onto the ink fountain roller 1. Each ink key K is moved by the drive of an ink key drive motor (not shown). In addition, a water fountain 5 that contains dampening water is provided in the water section located below the ink roller group 3, and the dampening water in the water fountain 5 can be supplied to the printing plate (not shown) wrapped around the plate cylinder 7 via a water fountain roller 6.

The ink keys K are arranged in a row in the axial direction of the ink fountain roller 1 (see FIG. 1), i.e., in the width direction of the printing press (printed material) (direction perpendicular to the conveying direction). The distance (opening) of the ink keys K from the ink fountain roller 1 is determined for each ink key according to the amount of ink required based on the print image. The print image has a plurality of image areas divided into a plurality of areas corresponding to each of the ink keys K arranged in the width direction of the printing press. An image area ratio is set for each image area, and in the present invention, the opening data of the ink keys K corresponding to the low image area ratio in the image area in which a low image area ratio lower than a predetermined area ratio is set among the image area ratios is acquired by the data acquisition means 8 described later.

Then, before printing, the opening of the ink keys K in the ink fountain is set (preset) according to the image to be printed. The opening of each ink key K is set using the image area ratio in the area of each ink key K of the image to be printed and a conversion curve (original curve) that indicates the relationship between the image area ratio and the opening of the ink keys K that is stored in advance. When printing with the opening of the ink keys K that has been set, the color tone (particularly the print density) of the printed matter is measured by an in-line or offline measuring means. In the area of the ink keys K where the color tone (particularly the print density) of the printed matter is inappropriate, the opening of the ink keys K is adjusted to match the color tone to the target value (the central value of the tolerance range or its vicinity).

When the color tone of the printed matter matches the target value (when printing the OK sheet), information on the opening degree of the ink key K and the image area ratio of the ink key K area is obtained, and a new curve, the first curve, is created based on this information.

Even if printing is performed by presetting based on the first curve, various factors may cause the color tone of the printed image to not match in image areas with low image area ratios. In particular, if the print density exceeds the allowable range in an image area with a low image area ratio, a large amount of paper is required to reduce the print density to within the allowable range by printing, resulting in a large increase in paper waste. Therefore, in the present invention, a new second curve is created to improve accuracy in image areas with low image area ratios.

In order to create the second curve, the printer is provided with three means as shown in FIG. 8. That is, the printer is provided with a data acquisition means 8 for acquiring the opening data of the ink keys K corresponding to the image area with a low image area ratio, which is lower than a predetermined value, during printing of the OK sheet, a correlation derivation means 9 for deriving the correlation between the low image area ratio and the opening of the ink keys K based on the opening data of the ink keys K acquired by the data acquisition means 8, and a correction means 10 for correcting the correlation derived by the correlation derivation means 9 by multiplying it by a coefficient that reduces the opening of the ink keys K. The correlation indicates the change in the value of the opening of the ink keys K when the value of the low image area ratio gradually increases. This correlation is shown in a line graph as shown in FIG. 6 and FIG. 7, but it may be shown in a bar graph or in a table in which the change in the value of the opening of the ink keys K is described in a table.

The process of actually creating the second curve by correcting the ink volume of the printing press will be explained with reference to the flowcharts in Figures 2 to 4.

First, the data acquisition means (which may be the same as the data acquisition means 8 or may be composed of different means) acquires the ink key K opening data corresponding to the image area with a low image area ratio (e.g., an image area ratio of 0% to 20%), the ink key K opening data corresponding to the image area with a medium image area ratio (e.g., an image area ratio of 21% to 50%), and the ink key K opening data corresponding to the image area with a high image area ratio (e.g., an image area ratio of 51% to 100%). After acquiring the data, as shown in FIG. 2, plots with an ink key opening of 0, which are inappropriate data, are removed from the acquired data (step S1). Then, outliers are removed (step S2). These outliers are plots where the average and standard deviation of the ink key K opening for the area ratio of each area are calculated, and the difference from the average is more than twice the standard deviation.

After the above two removal processes are performed, the second curve is created (step S3). As shown in FIG. 3, the second curve is created by determining whether the number of plots in the section is equal to or greater than a set number or less than a set number (step S10). If it is determined that the number of plots in all sections is equal to or greater than the set number, it is determined whether there is a previous section point (step S11). If there is a previous section point, an approximate straight line passing through the boundary point with the previous section is derived using the least squares method (step S12). If there is no previous section point, an approximate straight line is derived using the least squares method (step S13).

Here, if there are multiple types of plot area ratios within a section (for example, five types for the image area ratio between 40% and 60% in Figure 5), an approximation line of the plots within the section is found using the least squares method. From the approximation line found, the opening degree of the ink key K at the area ratio of the boundary of the section is calculated and recorded as a point on the second curve. Note that if there is only one type of plot area ratio within a section, using the least squares method will result in a vertical line (the denominator of the slope is 0), so the least squares method is performed including the plot of the previous section to find the line. If the slope of the line is vertical (or close to vertical) even when the plot of the previous section is included, the section is expanded until the slope of the line changes, and the least squares method is performed. If the slope does not change, the least squares method is performed including the plot of the subsequent section.

In Fig. 5, the intervals of 0% to 2% and 40% to 60% image area ratio are approximated straight lines obtained by the least squares method because there are no points in the previous intervals. The intervals of 2% to 4%, 4% to 8%, 8% to 12%, 12% to 16%, 16% to 20%, 60% to 80%, and 80% to 100% image area ratio are approximated straight lines passing through the boundaries with the previous intervals because there are points in the previous intervals. In Fig. 5, there are no plots in the interval of 20% to 40% image area ratio, so the points of 20% image area ratio and 40% image area ratio are connected. In Fig. 5, the approximate straight line of the plots in the intervals is obtained by the least squares method, and the first curve 1R showing the opening degree of the ink key K with respect to the image area ratio is shown. This first curve 1R is a curve before correction using the coefficient described later.

After the derivation of the approximation line is completed, the correction means 10 performs correction using a coefficient on the created first curve (step S15). In the section with a low image area ratio, the ink key K opening is plotted larger than the actual value, and it is easier to adjust the ink key K opening from the lower side. Therefore, for the opening calculated by the least squares method, the low image area ratio section is divided into small sections (for example, in FIG. 5, the section is 0% to 2%, the section is 2% to 4%, the section is 4% to 8%, the section is 8% to 12%, the section is 12% to 16%, and the section is 16% to 20%), and correction is performed by multiplying each section by the coefficient set by the correction means 10 (step S14). The coefficient used in the section with a low image area ratio (0% to 20% in this embodiment, but may be changed) is set to a value less than 1. In this embodiment, the coefficient is selected and set from the range of 0.50 to 0.95. FIG. 5 shows a second curve 2R (see solid line) obtained by correcting the first curve 1R in the section where the image area ratio is 0% to 20% by multiplying it by a coefficient (a value selected from the range of 0.50 to 0.95). In FIG. 5, the opening degree of the ink keys K in the second curve 2R is smaller than the opening degree of the ink keys K in the first curve 1R. And, the ink key opening degree K values of the first curve 1R and the second curve 2R are the same when the image area ratio is 20% or more. That is, the coefficient is set to 1 in the section where the image area ratio is 20% or more. By setting in this manner, the opening degree of the ink keys K can be suppressed to be small in the section where the image area ratio is low. In this embodiment, in the low image area ratio up to 4%, the area is divided into sections every 2%, and in the section where the image area ratio is 4% or more, the area is divided into sections every 4%, which is larger than 2%. The coefficient can also be set to be larger as the image area ratio of the divided area in the low image area is larger. Also, the coefficient may be set to a different value for each divided area, or the same value may be set for multiple areas. In addition, in the ink key opening adjustment system of this embodiment, for sections where it is desired to use the ink key K opening of the first curve in the second curve, even in sections with a low image area ratio, the coefficient can be set to 1. Also, for sections where it is desired to use the ink key K opening of the second curve larger than that of the first curve, a coefficient larger than 1 can be set.

In Figures 6 and 7, the solid line shows the second curve, which was created by multiplying each section of the low image area ratio region of the first curve, which was created by finding an approximation line of the plot within the section using the least squares method as described above, with a coefficient of less than 1. The dashed curves in Figures 6 and 7 are the original curves. The second curve, which was created by multiplying the coefficients as described above, has an ink key K opening in the low image area ratio region that is smaller than the ink key K opening of the first curve (not shown in Figures 6 and 7) before the coefficients were multiplied.

Once the correction is completed by multiplying the coefficient as described above, the process moves to the section where the number of plots is insufficient (step S15). Specifically, as shown in Figure 6, in the section of image area ratio where there is a shortage of plots (12% to 20% in Figure 6), the ink key opening of the original curve (the point where the image area ratio is 16%) exists between the maximum value of the ink key K opening of the section before the section where there is a shortage of plots and the minimum value of the ink key K opening of the section after the section where there is a shortage of plots, so the ink key opening of the original curve is recorded as the ink key K opening of the second curve.

In addition, in an image area ratio section where plots are insufficient (12% to 20% in Figure 6), if the ink key K opening of the original curve (a point where the image area ratio is 16%) does not exist between the maximum ink key opening of the section before the section where plots are insufficient and the minimum ink key opening of the section after the section where plots are insufficient, the point on the line connecting the minimum ink key K opening of the later section and the maximum ink key K opening of the previous section is recorded as the ink key K opening of the second curve, as shown in Figure 7.

When the processing of the section where the plot is insufficient as described above is completed, if there is a section where the slope of the line is negative, that section is processed (step S16). Specifically, if the ink key K opening of a first point on the second curve is lower than that of a second point with a higher image area ratio than that of the first point, connecting these two points will result in a line with a negative slope, so a point before the first point where the ink key K opening is lower is selected to make a line with a positive slope and set the ink key opening of the first point.

Based on the ink key opening of the point of the second curve obtained as described above, the ink key opening is adjusted to 100 stages (step S17). When the creation of the second curve is completed, return to FIG. 2 and perform the processing after the creation of the second curve (step S4). That is, the processing of FIG. 4 is performed. First, check whether an error has occurred during the creation of the second curve (step S20). If it is determined that an error has occurred, a message that the second curve could not be created is displayed on the display unit (step S21), and control is terminated. If it is determined in step S20 that no error has occurred, check for abnormal values (step S22). If there is a point where the value of each point of the second curve exceeds the upper or lower limit of the ink key K opening, it is determined that there is an abnormal value outside the range, and the value of that point is corrected to the upper or lower limit of the ink key K opening (step S23), the corrected second curve is displayed (step S24), and control is terminated. If no abnormal value is found in the abnormal value check, the second curve is displayed (step S24), and control is terminated.

The present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

In the above embodiment, the coefficient value was set to be larger as the image area ratio of the partitioned area was larger, but it may be set to the same value less than 1.

1... ink fountain roller, 2... ink call roller, 3... ink roller group, 4... traverse roller, 5... water fountain, 6... water fountain roller, 7... plate cylinder, 8... data acquisition means, 9... correlation derivation means, 10... correction means, 11... control unit, K... ink key, S... arrow

Claims (3)

The ink key opening adjustment system for a printing press is characterized by comprising: a data acquisition means for acquiring ink key opening data for printing an OK sheet, the ink key opening data corresponding to a low image area ratio of 0% to 20% set in an image region obtained by dividing a print image; a correlation derivation means for deriving a correlation between the low image area ratio and the ink key opening based on the ink key opening data acquired by the data acquisition means; and a correction means for correcting the correlation derived by the correlation derivation means by multiplying the correlation by a coefficient that reduces the ink key opening , i.e., a coefficient set to a value less than 1 . The ink key opening adjustment system for a printing press according to claim 1, characterized in that the coefficient is set for each divided area into which the image area ratio is divided into small parts for each value in a predetermined range, and the coefficient is set to be larger as the image area ratio of the divided area increases. The ink amount correction method for a printing press is characterized by comprising: a data acquisition step of acquiring ink key opening data during OK sheet printing for ink keys corresponding to a low image area ratio of 0% to 20% , which is set in an image region obtained by dividing a print image; a correlation derivation step of deriving a correlation between the low image area ratio and the ink key opening based on the ink key opening data acquired in the data acquisition step; and a correction step of multiplying the correlation derived in the correlation derivation step by a coefficient that reduces the ink key opening , i.e., a coefficient set to a value less than 1 .