Control method based on key area point multicolor overprinting

Abstract

The invention relates to a control method based on key area point multicolor overprinting, and provides a method which takes a key area point of a printing layout as an overprinting reference point and ensures the overprinting precision of the overprinting reference point, and the method comprises the following steps of: 1) selecting the position of a main graphic element representing a graphic surface in a color unit graphic as the key area point, and determining the position coordinate of the key area point of the graphic; determining a distance value from the position of an overprinting reference point of the printing layout to a transverse side line and a distance value from the position of the overprinting reference point to a longitudinal center line according to the row number of unit image-text makeup of the printing layout and longitudinal and transverse center line positions relative to the printing layout; (2) arranging a double-side overprinting color code and an overprinting color code detection probe, and calculating longitudinal and transverse overprinting deviations of each color group according to double-side probe signals; 3) calculating longitudinal and transverse overprinting adjustment amounts of each color group based on the layout overprinting reference points according to a formula; and (4) the overprinting adjustment amount of each color group is input into an overprinting feedback control program, the relative position of each color separation printing plate is adjusted, and overprinting deviation is eliminated.

Description

Technical Field

[0001] The invention relates to printing press overprinting technology, in particular to a control method based on key area point multi-color overprinting. Background Art

[0002] A color pattern has multiple relatively independent graphic elements, among which there is a graphic element that best expresses the design theme, which we call the key area. Since the color pattern is made up of multiple colors overprinted, the pattern designer and user hope that the overprint accuracy of the key area is the highest. However, the overprinting method of the existing multi-color printing machine is to overprint the entire printing format as a whole. The overprint deviation is based on the position deviation value of the detected overprint color mark and input calculation. The goal of overprint accuracy is also to minimize the deviation of the overprint color mark. The overprint color mark is set outside the pattern and is separated from the key area. When the overlap of the overprint color mark is the best, the overprint accuracy of the key area is not necessarily ideal. Therefore, the commonly used overprinting method cannot achieve the highest overprint accuracy in the overprint area. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a control method for multi-color overprinting based on key area points, which has higher precision of printing overprinting.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a control method for multi-color overprinting based on key area points, the overprinting method for a roll substrate printing machine with multiple color groups comprises the following steps:

[0005] 1) Determine the position coordinates of the key points of the image and text:

[0006] Select the location of the main graphic elements representing the drawing in the color unit image to be printed as the key area point, and determine the position coordinates (Q, P) of the key area point in the unit image;

[0007] 2) Determine the centerline position of the printing layout and the position coordinates of the overprint reference point:

[0008] The center line of the printing material in the printing direction is determined as the longitudinal center line, and the center line of the length direction of the entire printing plate is determined as the transverse center line; according to the number of unit image and text imposition rows and columns of the printing plate and the relative longitudinal and transverse center line positions of the printing plate, the distance value Y from the position of the overprint reference point of the printing plate to the transverse edge line and the distance value X to the longitudinal center line are determined;

[0009] 3) Set the overprint color mark of the color separation printing plate:

[0010] Left and right overprint color marks are respectively arranged on both sides of the longitudinal exterior of the image and text of the 1st to Mth color separation printing plates to be overprinted, and the center lines of the left and right overprint color marks are symmetrical to the longitudinal center line of the printing plate;

[0011] 4) Detect and calculate the longitudinal and lateral overprint deviations of the overprinted color marks on the left and right sides of the printing material between each color group:

[0012] 4.1) Use the color mark probes on both sides of the color registration detection system to detect the longitudinal detection distance between the left and right sides of the original color and the previous color registration mark, and subtract it from the plate registration color mark distance. The difference is the longitudinal registration deviation of the color on the left and right sides relative to the previous color group;

[0013] 4.2) Use the color mark probes on both sides of the color registration detection system to detect the height values ​​of the color marks on the left and right sides of the current color group and the previous color group, multiply them by the conversion coefficient of the color mark to obtain the lateral position of the center of the detected color mark. The lateral position distance difference of the color mark centers on the same side of the two color groups is the lateral registration deviation of the left and right sides of the color group where the color mark detection probe is located;

[0014] 5) Calculate the input values ​​of the longitudinal and transverse overprint adjustment for the 2nd to Mth color groups based on the key area points:

[0015] 5.1) Continuously detect the left and right longitudinal overprint deviations of the color group where the color mark detection probe is located within the three substrate plate diameter printing widths on the printing material, subtract the average value of the longitudinal overprint deviations of the left and right sides of the first width from the average value of the longitudinal overprint deviations of the left and right sides of the third width, multiply the obtained difference by the ratio of the longitudinal coordinate Y value of the overprint reference point to the substrate plate diameter printing width length, add the obtained ratio to the average value of the longitudinal overprint deviations of the left and right sides of the first width, and the sum obtained is the longitudinal overprint adjustment value of the color group where the color mark detection probe is located;

[0016] 5.2) Multiply the difference between the lateral overprint deviations on the left and right sides of the detected color group by the distance between the overprint reference point and the left overprint color mark, and then divide it by the distance between the left and right overprint color marks. The calculated value is the adjustment amount of the lateral overprint deviation of the overprint reference point relative to the left overprint color mark. The lateral overprint adjustment amount of the color group where the color mark detection probe is located is obtained by subtracting the adjustment amount of the lateral overprint deviation of the overprint reference point relative to the left overprint color mark from the lateral overprint deviation of the left overprint color mark.

[0017] As an improvement, the specific steps for determining the center line of the printing format and the position coordinates of the key points of the image and text are as follows:

[0018] 2.1) The element graphic area in the unit graphic that represents the theme to be expressed in the graphic is the key area of ​​the unit graphic, and the center point of the key area is determined as the key area point, and the coordinates of the center point are determined as the coordinates of the key area point;

[0019] 2.2) Determine the coordinates of the overprint reference point of the printing plate:

[0020] ① When there is no key point in the unit image, no matter how many unit images the printing layout consists of, the intersection of the longitudinal center line and the transverse center line of the printing layout is used as the overprint reference point of the printing layout. The position coordinates of the overprint reference point are: X = 0, Y = 0.5S pn ;

[0021] ② When the printing layout consists of a unit image, the key point of the unit image is used as the overprint reference point of the printing layout. The position coordinates of the overprint reference point are: X=Q, Y=P, (Q, P) is the coordinate value of the key point;

[0022] ③ When the printing layout consists of a single line of odd-numbered units or a single row of odd-numbered units, the position of the key point of the middle unit of the image and text is used as the overprint reference point of the printing layout. The position coordinates of the overprint reference point are: X = Q, Y = P, (Q, P) is the coordinate value of the key point of the middle unit of the image and text;

[0023] ④ When the printing layout is composed of a single line of even-numbered graphics or a single row of even-numbered graphics, the midpoint of the line connecting the key points of the two middle graphics units is used as the overprint reference point of the printing layout. When the graphics unit is a single line of even-numbered graphics, the position coordinates of the overprint reference point are: X = 0.5 * (Q1-Q2), Y = P; when the graphics unit is a single row of even-numbered graphics, the position coordinates of the overprint reference point are: X = Q, Y = 0.5 * (P2-P1), (Q1, P1) and (Q2, P2) are the coordinate values ​​of the key points of the two middle graphics units;

[0024] ⑤ When the printing layout consists of even-numbered rows and even-numbered rows of unit graphics, the midpoint of the line connecting the midpoints of the key points of the two graphic units in the middle row or middle row is used as the overprint reference point of the printing layout. The position of the overprint reference point is marked as: X = 0.5*(Q1-Q2), Y = 0.5*(P2-P1), (Q1, P1) and (Q2, P2) are the coordinate values ​​of the key points of the two middle graphic units;

[0025] ⑥ When the printed layout consists of even-numbered and odd-numbered rows or odd-numbered and even-numbered rows of unit graphics, the midpoint of the line connecting the key points of the two unit graphics in the middle row or middle row is the overprint reference point of the printed layout. When the graphic unit is an even-numbered row, the position of the overprint reference point is marked as: X = Q2, Y = 0.5*(P2-P1); when the graphic unit is an even-numbered row, the position of the overprint reference point is marked as: X = 0.5*(Q1-Q2), Y = P2, (Q1, P1) and (Q2, P2) are the coordinate values ​​of the key points of the two middle graphic units;

[0026] ⑦ When the printing layout consists of multiple odd-numbered lines and multiple odd-numbered rows of unit graphics, the key area points of the middle unit graphics are used as the overprint reference points of the printing layout. The position of the overprint reference points is marked as: X=Q2, Y=P2, (Q2, P2) is the coordinate value of the key area points of the two middle graphics units.

[0027] As an improvement, the calculation formulas for the longitudinal adjustment amount of sequential overprinting of the Nth color group to the (N-1th) color group and the lateral adjustment amount of sequential overprinting are as follows:

[0028] R Vn =0.5[(Y+S pn )*(ΔL 1l +ΔL 1r )- Y*(ΔL 2l +ΔL 2r )] / S pn mm (1)

[0029] R Cn =ΔC nl +0.5*(ΔC nl -ΔC nr )*(DX) / D mm (2)

[0030] In the above formula:

[0031] X, Y are the coordinate values ​​of the overprint reference point within the printing width of the substrate plate;

[0032] D is the distance between the horizontal center of the overprint color mark and the center line of the printing plate;

[0033] S pn The diameter of the substrate is the printing width length;

[0034] ΔL 1l , ΔL 1r , ΔL 2l , ΔL 2r It is the longitudinal overprint deviation on the left and right sides of the Nth color group of the first and third frames of the printing material;

[0035] ΔC nl and ΔC nr It is the horizontal overwriting deviation on the left and right sides of the Nth color group.

[0036] As an improvement, the formula for calculating the longitudinal overprint deviation on the left and right sides of the Nth color group of the first and third sheets of the printing material is as follows:

[0037] ΔL 1l =L (n-1)l -L e mm (3)

[0038] ΔL 1r =L(n-1)r -L e mm (4)

[0039] ΔL 2l =L (n+1)l -L e mm (5)

[0040] ΔL 2r =L (n+1)r -L e mm (6)

[0041] ΔC nl =[H nl -H (n-1)l ]*I mm (7)

[0042] ΔC nr =[H nr -H (n-1)r ]*I mm (8)

[0043] L (n-1)l , L (n-1)r , L (n+1)l and L (n+1)r To continuously detect the color mark spacing values ​​on the left and right sides of the Nth color group and the (N-1)th color group of the first and third frames on the printing material;

[0044] H nl , H nr , H (n-1)l and H (n-1)r The detection height of the color marks on the left and right sides of the Nth color group and the (N-1)th color group;

[0045] I is the conversion factor between the center height and width of the bidirectional overprint color mark. For the wedge mark:

[0046] I=W / (H B -H T );W is the length of the wedge mark, H B and H T Mark the heights of the upper and lower bases of the wedge respectively.

[0047] As an improvement, the printing press is equipped with a total of M color groups. The calculated values ​​of the sequential overprinting longitudinal adjustment amount and the sequential overprinting lateral adjustment amount of each color group are input into the color registration control program to control the speed of the drive motor of each color separation printing plate, so as to achieve the purpose of the highest overprint of the main graphics in the unit image and text.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] A method is provided for converting equidistant center points of multiple key areas in a printing layout as overprint reference points based on key areas in a color unit graphic, and an algorithm is further provided. When calculating the adjustment amount, the position of the printing reference point of the printing layout is associated with the overprint deviation of the detected overprint color mark, overprint analysis calculation is performed around the key area, and the longitudinal and lateral overprint adjustment amount input values ​​of the color group based on the key area point or center line are calculated to ensure that the overprint accuracy of the key area is maximized. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the longitudinal and lateral overprint adjustment amounts of the overprint reference point.

[0051] Figure 2 Determine the overprint reference point of the printing layout for the first method.

[0052] Figure 3 Determine the overprint reference point of the printing layout for the second method.

[0053] Figure 4 The third method is to determine the overprint reference point of the printing layout.

[0054] Figure 5 The fourth method is to determine the overprint reference point of the printing layout.

[0055] Figure 6 The fifth method is to determine the overprint reference point of the printing layout.

[0056] Figure 7 The sixth method is to determine the overprint reference point of the printing layout.

[0057] Figure 8 The seventh method is to determine the overprint reference point of the printing layout.

[0058] Fig. 9 The eighth method is to determine the overprint reference point of the printing layout.

[0059] Fig.10 The ninth method is to determine the overprint reference point of the printing layout.

[0060] Fig.11 The tenth method is to determine the overprint reference point of the printing layout. DETAILED DESCRIPTION

[0061] The present invention will be further described below in conjunction with the accompanying drawings.

[0062] Figure 2 to Figure 11 The middle trapezoid is the overprint color mark, the rectangle is the key area point of a single graphic unit, and the circle is the overprint reference point of the entire printing page.

[0063] A control method for multi-color overprinting based on key area points, the overprinting method for a roll-type substrate printing machine with multiple color groups comprises the following steps:

[0064] 1) Determine the position coordinates of the key points of the image and text:

[0065] Select the location of the main graphic element representing the theme to be expressed in the color unit graphic to be printed as the key point, and determine the position coordinates (Q, P) of the key point in the unit graphic;

[0066] 2) Determine the centerline position of the printing layout and the position coordinates of the overprint reference point:

[0067] The center line of the printing material in the printing direction is determined as the longitudinal center line, and the center line of the length direction of the entire printing plate is determined as the transverse center line; according to the number of unit image and text imposition rows and columns of the printing plate and the relative longitudinal and transverse center line positions of the printing plate, the distance value Y from the position of the overprint reference point of the printing plate to the transverse edge line and the distance value X to the longitudinal center line are determined;

[0068] 3) Set the overprint color mark of the color separation printing plate:

[0069] Set left and right overprint color marks on both sides of the vertical outside of the image and text of the 1st to Mth color separation printing plates to be overprinted, and determine the horizontal relative position distance between the overprint reference point and each color overprint color mark;

[0070] 4) Detect and calculate the longitudinal and lateral overprint deviations of the left and right color marks on the printing material between each color group:

[0071] 4.1) Use the color mark probes on both sides of the color registration detection system to detect the longitudinal detection distance between the left and right sides of the original color and the previous color registration color mark, and subtract it from the plate registration color mark distance respectively. The difference is the longitudinal registration deviation of the color where the detection probe is located relative to the previous color group on the left and right sides;

[0072] 4.2) Use the color mark probes on both sides of the color registration detection system to detect the height values ​​of the left and right color marks of the current color group and the previous color group, multiply them by the conversion coefficient of the color mark to obtain the lateral position of the center of the detected color mark. The lateral position distance difference of the color mark centers on the same side of the two color groups is the lateral registration deviation of the left and right sides of the color group where the color mark detection probe is located;

[0073] 5) Calculate the input values ​​of the longitudinal and transverse overprint adjustment for the 2nd to Mth color groups based on the key area points:

[0074] 5.1) Continuously detect the left and right longitudinal overprint deviations of the color group in the three substrate plate diameter printing widths on the printing material, subtract the average value of the longitudinal overprint deviations of the left and right sides of the third sheet from the average value of the longitudinal overprint deviations of the left and right sides of the first sheet, multiply the difference by the ratio of the longitudinal coordinate Y value of the overprint reference point to the substrate plate diameter printing width length, add the average value of the longitudinal overprint deviations of the left and right sides of the first sheet to the ratio, and the sum is the longitudinal overprint adjustment value of the color group where the color mark detection probe is located;

[0075] 5.2) Multiply the difference of the lateral overprint deviations on the left and right sides of the detected color group by the distance between the overprint reference point and the left color overprint color mark, and then divide it by the distance between the left and right overprint color marks. The calculated value is the adjustment amount of the lateral overprint deviation of the overprint reference point relative to the left color mark. The lateral overprint adjustment amount of the color group where the color mark detection probe is located is obtained by subtracting the adjustment amount of the lateral overprint deviation of the overprint reference point relative to the left color mark from the lateral overprint deviation of the left color mark.

[0076] The specific steps to determine the center line of the printing format and the position coordinates of the key points of the image and text are:

[0077] 2.1) The element graphic area in the unit graphic that represents the theme to be expressed in the graphic is the key area of ​​the unit graphic, and the center point of the key area is determined as the key area point, and the coordinates of the center point are determined as the coordinates of the key area point;

[0078] 2.2) Determine the coordinate value of the overprint reference point of the printing plate:

[0079] ① Such as Figure 2 As shown in the figure, when there is no key point in the unit image, no matter how many unit images the printing layout consists of, the intersection of the longitudinal center line and the transverse center line of the printing layout is used as the overprint reference point of the printing layout; the reference point A takes the coordinate value: X = 0, Y = 0.5 × S P ;

[0080] ② If Figure 3 As shown, when the printing layout consists of a unit image, the center of the key area of ​​the unit image is used as the overprint reference point of the printing layout; the reference point A takes the coordinate values: X = Q, Y = P;

[0081] ③ When the printing layout consists of a single line of odd-numbered units or a single row of odd-numbered units, the position of the key point of the middle unit image is used as the overprint reference point of the printing layout; Figure 4 As shown, when the vertical arrangement of the unit image and text in the printing layout is 1 and the horizontal arrangement is an odd number, the reference point A takes the coordinate value: X = Q, Y = P; Figure 5 As shown, when the vertical arrangement of the unit images and texts in the printed page is an odd number and the horizontal arrangement is 1, the reference point A takes the coordinate values: X=Q, Y=P2;

[0082] ④ When the printing layout consists of a single line of even-numbered graphics or a single row of even-numbered graphics, the midpoint of the line connecting the key points of the two middle graphics units shall be the overprint reference point of the printing layout; Figure 6 As shown, when the vertical arrangement of the unit images in the printed page is 1 and the horizontal arrangement is an even number, the reference point A takes the coordinate value: X = 0.5 × (Q1-Q2), Y = P; Figure 7 As shown, when the vertical arrangement of the unit image and text in the printed page is 2 and the horizontal arrangement is 1, the reference point A takes the coordinate value: X=Q, Y=0.5×(P2-P1);

[0083] ⑤ Such as Figure 8 As shown, when the printing layout consists of even-numbered rows and even-numbered rows of unit graphics, the midpoint of the line connecting the midpoints of the key area points of the two graphic units in the middle row or middle row is used as the overprint reference point of the printing layout; the reference point A takes the coordinate values: X = 0.5 × (Q1-Q2), Y = 0.5 × (P2-P1);

[0084] ⑥ Such as Fig. 9 As shown in FIG. 1 , when the vertical arrangement of the unit images in the printing layout is an even number and the horizontal arrangement is an odd number, the midpoint of the line connecting the key points of the unit images in the middle row or the middle row is used as the overprint reference point of the printing layout; the reference point A takes the coordinate values: X=Q2, Y=0.5×(P2-P1); Fig.10 As shown, when the vertical arrangement of the unit images in the printing layout is an odd number and the horizontal arrangement is an even number, the midpoint of the line connecting the key points of the unit images in the middle row or the middle line is used as the overprint reference point of the printing layout; the reference point A takes the coordinate value: X = 0.5 × (Q1-Q2), Y = P2;

[0085] ⑦ Such as Fig.11 As shown, when the vertical arrangement of the unit images in the printing layout is an odd number and the horizontal arrangement is an odd number, the key area point of the middle unit image is used as the overprint reference point of the printing layout; the reference point A takes the coordinate value: X=Q2, Y=P2;

[0086] 2.3) Determine the coordinate value of the overprint reference point of the printing plate according to the geometric relationship in the figure and the coordinates of the key points of the graphic unit.

[0087] like Figure 1 As shown, the calculation formulas for the longitudinal adjustment amount of sequential overprinting of the Nth color group to the (N-1)th color group and the lateral adjustment amount of sequential overprinting are as follows:

[0088] R Vn =0.5[(Y+S pn )*(ΔL 1l +ΔL 1r )- Y*(ΔL 2l +ΔL 2r)] / S pn mm (1)

[0089] R Cn =ΔC nl +0.5*(ΔC nl -ΔC nr )*(DX) / D mm (2)

[0090] ΔL 1l =L (n-1)l -L e mm (3)

[0091] ΔL 1r =L (n-1)r -L e mm (4)

[0092] ΔL 2l =L (n+1)l -L e mm (5)

[0093] ΔL 2r =L (n+1)r -L e mm (6)

[0094] ΔC nl =[H nl -H (n-1)l ]*I mm (7)

[0095] ΔC nr =[H nr -H (n-1)r ]*I mm (8)

[0096] In the above formula:

[0097] X, Y are the coordinate values ​​of the overprint reference point within the printing width of the substrate plate;

[0098] D is the distance between the horizontal center of the overprint color mark and the center line of the printing plate;

[0099] ΔL nl and ΔL nr The left and right longitudinal overprint deviations of the sequential overprint of the Nth color;

[0100] ΔL 1l , ΔL 1r , ΔL 2l , ΔL 2r It is the longitudinal overprint deviation on the left and right sides of the Nth color group of the first and third frames of the printing material;

[0101] ΔC nl and ΔC nrIt is the horizontal overwriting deviation on the left and right sides of the Nth color group.

[0102] L (n-1)l , L (n-1)r , L (n+1)l and L (n+1)r To continuously detect the color mark spacing values ​​on the left and right sides of the Nth color group and the (N-1)th color group of the first and third frames on the printing material;

[0103] H nl , H nr , H (n-1)l and H (n-1)r The detection height of the color marks on the left and right sides of the Nth color group and the (N-1)th color group;

[0104] I is the conversion factor between the center height and width of the bidirectional overprint color mark. For the wedge-shaped mark, I=W / (H B -H T );

[0105] S Pn It is the circumference of the printing plate of the Nth color.

[0106] The calculated values ​​of the longitudinal adjustment amount of sequential overprinting and the lateral adjustment amount of sequential overprinting of each color group are input into the color registration control program to control the speed of the drive motor of each color separation printing plate to achieve the purpose of the highest overprint of the main graphics in the unit image.

Claims

1. A control method for multi-color overprinting based on key area points, characterized in that: A method for registering a web-based printing press having multiple color groups comprises the following steps: 1) Determine the position coordinates of the key points of the image and text: Select the location of the main graphic elements representing the drawing in the color unit image to be printed as the key area point, and determine the position coordinates (Q, P) of the key area point in the unit image; 2) Determine the centerline position of the printing layout and the position coordinates of the overprint reference point: The center line of the printing material in the printing direction is determined as the longitudinal center line, and the center line of the length direction of the entire printing plate is determined as the transverse center line; according to the number of unit image and text imposition rows and columns of the printing plate and the relative longitudinal and transverse center line positions of the printing plate, the distance value Y from the position of the overprint reference point of the printing plate to the transverse edge line and the distance value X to the longitudinal center line are determined; 3) Set the overprint color mark of the color separation printing plate: Left and right overprint color marks are respectively set on both sides of the longitudinal outside of the image and text of the 1st to Mth color separation printing plates to be overprinted, and the center lines of the left and right overprint color marks are symmetrical to the longitudinal center line of the printing plate; 4) Detect and calculate the longitudinal and lateral overprint deviations of the overprinted color marks on the left and right sides of the printing material between each color group: 4.1) Use the color mark detection probes on both sides of the color registration detection system to detect the longitudinal detection distance between the left and right sides of the original color and the previous color registration color mark, and subtract it from the plate registration color mark distance. The difference is the longitudinal registration deviation of the color group where the detection probe is located relative to the previous color group on the left and right sides; 4.2) Use the color mark detection probes on both sides of the color registration detection system to detect the height values ​​of the color marks on the left and right sides of the current color group and the previous color group, multiply them by the conversion coefficient of the color mark to obtain the lateral position of the center of the detected color mark. The lateral position distance difference of the color mark centers on the same side of the two color groups is the lateral registration deviation of the left and right sides of the color group where the color mark detection probe is located; 5) Calculate the input values ​​of the longitudinal and transverse overprint adjustment for the 2nd to Mth color groups based on the key area points: 5.1) Continuously detect the left and right longitudinal overprint deviations of the color group where the color mark detection probe is located within the three substrate plate diameter printing widths on the printing material, subtract the average value of the longitudinal overprint deviations of the left and right sides of the first width from the average value of the longitudinal overprint deviations of the left and right sides of the third width, multiply the obtained difference by the ratio of the longitudinal coordinate Y value of the overprint reference point to the substrate plate diameter printing width length, add the obtained ratio to the average value of the longitudinal overprint deviations of the left and right sides of the first width, and the sum obtained is the longitudinal overprint adjustment value of the color group where the color mark detection probe is located; 5.2) Multiply the difference between the lateral overprint deviations on the left and right sides of the detected color group by the distance between the overprint reference point and the left overprint color mark, and then divide it by the distance between the left and right overprint color marks. The calculated value is the adjustment amount of the lateral overprint deviation of the overprint reference point relative to the left overprint color mark. The lateral overprint adjustment amount of the color group where the color mark detection probe is located is obtained by subtracting the adjustment amount of the lateral overprint deviation of the overprint reference point relative to the left overprint color mark from the lateral overprint deviation of the left overprint color mark.

2. According to claim 1, a control method for multi-color overprinting based on key area points is characterized by: The specific steps to determine the center line of the printing format and the position coordinates of the key points of the image and text are: 2.1) The element graphic area in the unit graphic that represents the theme to be expressed in the graphic is the key area of ​​the unit graphic, and the center point of the key area is determined as the key area point, and the coordinates of the center point are determined as the coordinates of the key area point; 2.2) Determine the overprint reference point and coordinate value of the reference point of the printing plate: ① When there is no key point in the unit image, no matter how many unit images the printing layout consists of, the intersection of the longitudinal center line and the transverse center line of the printing layout is used as the overprint reference point of the printing layout. The position coordinates of the overprint reference point are: X = 0, Y = 0.5S pn ; ② When the printing layout consists of a unit image, the key point of the unit image is used as the overprint reference point of the printing layout. The position coordinates of the overprint reference point are: X=Q, Y=P, (Q, P) is the coordinate value of the key point; ③ When the printing layout consists of a single line of odd-numbered unit images or a single row of odd-numbered unit images, the position of the key area point of the middle unit image is used as the overprint reference point of the printing layout, and the position coordinates of the overprint reference point are: X = Q, Y = P, (Q, P) is the coordinate value of the key area point of the middle unit image; ④ When the printing layout consists of a single line of even-numbered graphics or a single row of even-numbered graphics, the midpoint of the line connecting the key points of the two middle graphics units is used as the overprint reference point of the printing layout. When the graphics unit is a single line of even-numbered graphics, the position coordinates of the overprint reference point are: X = 0.5*(Q1-Q2), Y = P; when the graphics unit is a single row of even-numbered graphics, the position coordinates of the overprint reference point are: X = Q, Y = 0.5*(P2-P1), (Q1, P1) and (Q2, P2) are the coordinate values ​​of the key points of the two middle graphics units; ⑤ When the printing layout consists of even-numbered rows and even-numbered rows of unit graphics, the midpoint of the line connecting the midpoints of the key points of the two graphic units in the middle row or middle row is used as the overprint reference point of the printing layout. The position of the overprint reference point is marked as: X = 0.5*(Q1-Q2), Y = 0.5*(P2-P1), (Q1, P1) and (Q2, P2) are the coordinate values ​​of the key points of the two middle graphic units; ⑥ When the printed layout consists of even-numbered and odd-numbered rows or odd-numbered and even-numbered rows of unit graphics, the midpoint of the line connecting the key points of the two unit graphics in the middle row or middle row is the overprint reference point of the printed layout. When the graphic unit is an even-numbered row, the position of the overprint reference point is marked as: X = Q2, Y = 0.5*(P2-P1); when the graphic unit is an even-numbered row, the position of the overprint reference point is marked as: X = 0.5*(Q1-Q2), Y = P2, (Q1, P1) and (Q2, P2) are the coordinate values ​​of the key points of the two middle graphic units; ⑦ When the printing layout consists of multiple odd-numbered lines and multiple odd-numbered rows of unit graphics, the key area points of the middle unit graphics are used as the overprint reference points of the printing layout. The position of the overprint reference points is marked as: X=Q2, Y=P2, (Q2, P2) is the coordinate value of the key area points of the two middle graphics units.

3. The control method of multi-color overprinting based on key area points according to claim 1, characterized in that: The calculation formulas for the longitudinal adjustment amount of sequential overprinting of the Nth color group to the (N-1th) color group and the lateral adjustment amount of sequential overprinting are as follows: R Vn =0.5[(Y+S pn )*(ΔL 1l +ΔL 1r )- Y*(ΔL 2l +ΔL 2r )] / S pn mm (1) R Cn =ΔC nl +0.5*(ΔC nl -ΔC nr )*(D-X) / D mm (2) In the above formula: X, Y are the coordinate values ​​of the overprint reference point within the printing width of the substrate plate; D is the distance between the horizontal center of the overprint color mark and the center line of the printing plate; S pn The diameter of the substrate is the printing width length; ΔL 1l , ΔL 1r , ΔL 2l , ΔL 2r It is the longitudinal overprint deviation on the left and right sides of the Nth color group of the first and third frames of the printing material; ΔC nl and ΔC nr It is the horizontal overwriting deviation on the left and right sides of the Nth color group.

4. The control method of multi-color overprinting based on key area points according to claim 3 is characterized in that: The calculation formula for the longitudinal overprint deviation on the left and right sides of the Nth color group of the first and third sheets of the printing material is as follows: ΔL 1l =L (n-1)l - L e mm (3) ΔL 1r =L (n-1)r - L e mm (4) ΔL 2l =L (n+1)l - L e mm (5) ΔL 2r =L (n+1)r - L e mm (6) ΔC nl =[H nl - H (n-1)l ]*I mm (7) ΔC nr =[H nr - H (n-1)r ]*I mm (8) In the above formula: L ( n-1)l、L ( n-1)r、L ( n +1) l and L ( n +1) r is the color mark spacing value of the left and right sides of the Nth color group and the (N-1)th color group of the first and third frames on the printing material continuously detected; Hnl, Hnr, H ( n- 1) l and H ( n- 1) r is the detection height of the color marks on the left and right sides of the Nth color group and the (N-1)th color group; I is the conversion factor between the center height and width of the bidirectional overprint color mark. For the wedge-shaped mark, I=W / (H B -H T );W is the length of the wedge mark, H B and H T Mark the heights of the upper and lower bases of the wedge respectively.

5. A control method for multi-color overprinting based on key area points according to claims 1 to 4, characterized in that: The calculated values ​​of the longitudinal adjustment amount of sequential overprinting and the lateral adjustment amount of sequential overprinting of each color group are input into the color registration control program to control the speed of the drive motor of each color separation printing plate to achieve the purpose of the highest overprint of the main graphics in the unit image.

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