CN112918074A - Correction method for printing equipment - Google Patents
Correction method for printing equipment Download PDFInfo
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- CN112918074A CN112918074A CN202110080650.1A CN202110080650A CN112918074A CN 112918074 A CN112918074 A CN 112918074A CN 202110080650 A CN202110080650 A CN 202110080650A CN 112918074 A CN112918074 A CN 112918074A
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- distribution correction
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F7/00—Rotary lithographic machines
- B41F7/02—Rotary lithographic machines for offset printing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F13/00—Common details of rotary presses or machines
- B41F13/08—Cylinders
- B41F13/10—Forme cylinders
- B41F13/12—Registering devices
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- Mechanical Engineering (AREA)
- Spectrometry And Color Measurement (AREA)
- Inking, Control Or Cleaning Of Printing Machines (AREA)
Abstract
The invention belongs to the technical field of printing equipment, and particularly relates to a method for correcting the printing equipment. And selecting a group of reflection density data, substituting other data and the minimum density value into a formula to obtain dot area coverage rate data, fitting the plurality of data to obtain an ink volume distribution correction curve, and repeatedly fitting the plurality of groups of reflection density data to obtain a plurality of ink volume distribution correction curves. The printing sample sheets with different ink colors are selected, all the obtained ink amount distribution correction curves are fitted into an ink amount distribution correction curved surface, the curved surface is corrected into a plane, the plane serves as a correction standard of the electronic manuscript, a user can accurately adjust the ink amount of the printing equipment, and the problem of uneven ink colors when a large area or a large area is printed on the spot is solved.
Description
Technical Field
The invention belongs to the technical field of printing equipment, and particularly relates to a method for correcting the printing equipment.
Background
Offset printing packaging products often have large areas of solid background color, requiring thick, uniform and consistent ink color. The consistency of the ink color includes two aspects: the first is the consistency of the ink colors of different printed sheets which are printed in sequence; the second is the consistency of ink colors at different parts of the same printed sheet. The requirement on the consistency of ink colors at different parts of the same printed sheet in the current market is particularly strict, which is also a key factor for evaluating the quality of products.
Offset printing equipment is generally long ink path, and the structure is complicated, and such characteristic makes the seal ink layer of the seal of gluing thinner to lead to the seal to easily appear the defect such as ink stick, back set dirty, dark back before the ink color is shallow. When printing large breadth and large area solid printed sheets, the printed sheets are not easy to achieve the effect of thick, solid and uniform ink color. Therefore, when a lithographic offset press prints large-area pictures and texts or solid printed products, the phenomenon that the ink color of the same printed product is dark in front and light in back or dark in front and back often occurs, and the quality of the product is seriously influenced. The main reason for this phenomenon is, in addition to the process operation and materials, the influence of the long ink path structure layout of the offset printing apparatus itself and the characteristics of the apparatus itself. Currently, due to technical limitation in the industry, the structural layout of a long ink path and the equipment characteristics of offset printing equipment cannot be improved temporarily, and the problem of uneven ink color can be solved only by adjusting the equipment, but the adjusting equipment often lacks reference and standard.
Disclosure of Invention
The present invention has been made to solve the above-described problems, and an object thereof is to provide a method of correcting a printing apparatus for correcting unevenness in printing ink.
The invention provides a correction method for a printing device, which is characterized by comprising the following steps: step 1, manufacturing a lithographic printing test plate consistent with the layout content of an electronic manuscript to be printed by utilizing a CTP (computer to plate) technology; step 2, printing on each unit of the printing equipment in sequence by using a lithographic printing test plate to obtain a plurality of single-color printing samples, wherein the ink colors of the single-color printing samples are different, each printing sample comprises a plurality of areas with different ink rates, the areas extend along a first direction, and the first direction of the single-color printing samples is provided with scale marks; step 3, selecting a printing sample, and respectively measuring the spectral reflection density of data points corresponding to each scale mark of the scales in each area, wherein the spectral reflection density data of each area is a group, so as to obtain a plurality of groups of reflection density data, and each group of reflection density data has a minimum density value and other data; step 4, selecting a group of reflection density data, substituting one of other data in the reflection density data and the minimum density value into a dot area coverage rate calculation formula each time to obtain dot area coverage rate data, and substituting all other data once to obtain a plurality of dot area coverage rate data; step 5, inputting the area coverage rate data of the plurality of dots obtained in the step 4 into a correction program, and fitting to obtain an ink amount distribution correction curve; step 6, selecting different groups of reflection density data each time, repeating the steps 4-5, and respectively obtaining a plurality of ink quantity distribution correction curves; 7, selecting printing samples with different ink colors each time, and repeating the steps 3-6 to respectively obtain a plurality of ink amount distribution correction curves; and 8, fitting the ink amount distribution correction curve obtained in the steps 5, 6 and 7 into an ink amount distribution correction curved surface, adjusting the ink amount distribution correction curved surface into a plane, correcting the pixel value of the electronic manuscript according to the plane, and correspondingly setting the printing equipment.
In the correction method for a printing apparatus provided by the present invention, there may be further provided a feature that: wherein the calculation formula of the dot area coverage rate is as follows
Or
In the above formula, α is the dot area coverage, DminIs the minimum density value in the reflection density data，DSN is a correction coefficient for any one of the remaining data in the reflection density data.
In the correction method for a printing apparatus provided by the present invention, there may be further provided a feature that: the ink color includes black, cyan, magenta and yellow.
In the correction method for a printing apparatus provided by the present invention, there may be further provided a feature that: in step 3, the spectral reflection density is measured using a spectrophotometer or a reflection densitometer for printing.
Action and Effect of the invention
According to the correction method for the printing equipment related by the invention, a lithographic printing test plate with the same page content as an electronic manuscript is manufactured, then the printing equipment provided with the lithographic printing test plate is used for printing sample sheets with different ink colors, each printing sample sheet comprises a plurality of areas with different ink rates, one printing sample sheet is selected, the spectral reflection density of a data point corresponding to a scale mark on the printing sample sheet in each area of the sample sheet is respectively measured, the spectral reflection density data of each area is a group, a plurality of groups of reflection density data are obtained, a group of reflection density data are selected, one of other data in the reflection density data and the minimum density value are taken into a dot area coverage rate calculation formula each time, a plurality of dot area coverage rate data are obtained, the obtained data are input into a correction program, and an ink amount distribution correction curve is obtained by fitting, different groups of reflection density data are selected and are respectively fitted repeatedly to obtain a plurality of ink quantity distribution correction curves, so that points are taken from each area on a printed sample sheet, and the accuracy of the ink quantity distribution correction curves is ensured to the maximum extent. The method comprises the steps of selecting printing samples with different ink colors, respectively and repeatedly measuring to obtain a plurality of ink amount distribution correction curves, fitting all the obtained ink amount distribution correction curves into an ink amount distribution correction curved surface, correcting the curved surface into a plane, correcting the pixel value of an electronic manuscript according to the plane, and meanwhile, enabling the plane to serve as a standard for correspondingly adjusting the printing equipment, so that the ink amount of the printing equipment can be adjusted more accurately by a user, and the problem of uneven ink colors when the printing equipment prints large-breadth or large-area solid printing products is effectively solved.
Drawings
FIG. 1 is a schematic illustration of a lithographic test plate layout in an embodiment of the present invention;
FIG. 2 is a schematic illustration of a black print proof in an embodiment of the invention;
FIG. 3 is a schematic view of an ink amount distribution correcting curved surface in the embodiment of the present invention.
Detailed Description
In order to make the technical means, creation features, achievement objects and effects of the present invention easy to understand, a method for correcting a printing device according to the present invention is specifically described below with reference to the embodiments and the accompanying drawings.
< example >
This embodiment explains a correction method for a printing apparatus in detail.
The correction method for the printing equipment in the embodiment specifically comprises the following steps:
step 1, a lithographic printing test plate (see fig. 1) consistent with pixel values of all points of an electronic manuscript to be printed is manufactured by utilizing a CTP (computer to plate) technology. FIG. 1 is a schematic layout of a lithographic test plate in this embodiment.
And 2, respectively printing black, cyan, magenta and yellow single-color printing samples by using the offset printing test plate arranged on the offset printing equipment.
In the present embodiment, only the monochrome print sheets of the above four colors are exemplified, and in practical cases, monochrome print sheets of other colors may be printed.
Fig. 2 is a schematic diagram of a black print proof in the present embodiment.
As shown in fig. 2, the black print swatch is a 720mm × 1020mm rectangular swatch, containing nine areas of different ink ratios. The nine regions are arranged along the length of the black printed sample, and are sequentially marked as a first region, a second region … from left to right, and so on. The ink ratios of the nine areas are 100% dot, 25% dot, 50% dot, 75% dot, 100% dot, 75% dot, 50% dot, 25% dot, and 100% dot in sequence. The width direction of the black printing sample sheet is taken as a first direction, the nine areas all extend along the first direction, and the black printing sample sheet is further provided with scales A-I extending along the first direction.
In this step, the structure of the black printing sample is taken as an example for explanation, and the structures of the cyan, magenta and yellow printing samples are the same as the structures of the black printing samples except for the ink color, and are not described herein again.
And 3, selecting black printing samples, and measuring the spectral reflection densities of data points corresponding to the A-I scale lines in the first area to the ninth area respectively by using a spectrophotometer, wherein the spectral reflection density data of each area are a group to obtain nine groups of reflection density data, and each group of reflection density data has a minimum density value and other data. The other data are data other than the minimum density value.
And 4, selecting reflection density data of the first area, substituting one of other data in the reflection density data and the minimum density value into a dot area coverage rate calculation formula each time, and substituting all other data once to obtain a plurality of dot area coverage rate data of the first area.
The calculation formula of the area coverage rate of the mesh points is as follows:
wherein, alpha is the dot area coverage rate, DminIs the minimum density value, D, in the reflected density dataSIs any one of the remaining data in the reflection density data.
In this step, the first region is taken as an example for explanation, the calculation method of the dot area coverage data of the second to ninth regions is the same as that of the first region, and is not repeated here, and the dot area coverage data of the nine regions are shown in table 1.
| 100％ | 25％ | 50％ | 75％ | 100％ | 75％ | 50％ | 25％ | 100％ | |
| 1 | 100 | 40.27 | 67.76 | 85.92 | 99.4 | 85 | 67.76 | 40.27 | 99.7 |
| 2 | 99.5 | 38.8 | 66 | 85 | 98.8 | 84.08 | 66 | 37.33 | 99.4 |
| 3 | 98.8 | 37.33 | 64.24 | 84.08 | 98.2 | 83.16 | 64.24 | 35.86 | 98.8 |
| 4 | 98.2 | 35.86 | 62.48 | 82.24 | 97.6 | 82.24 | 62.48 | 34.39 | 98.2 |
| 5 | 97.6 | 32.92 | 60.72 | 81.32 | 97 | 81.32 | 55.44 | 32.92 | 97.6 |
| 6 | 96.4 | 31.45 | 58.96 | 80.4 | 96.4 | 80.4 | 53.68 | 31.45 | 96.4 |
| 7 | 95.8 | 29.98 | 57.2 | 79.48 | 95.8 | 79.48 | 52.13 | 29.98 | 95.8 |
| 8 | 95.2 | 27.04 | 53.68 | 78.56 | 94.6 | 78.56 | 51.92 | 27.04 | 94.6 |
TABLE 1 dot area coverage
And 5, inputting the data of the area coverage rate of the dots in the first area into a spline function program, fitting to obtain an ink amount distribution correction curve of the first area, and sequentially inputting the area coverage rates of the dots from the second area to the ninth area into the spline function program to respectively obtain ink amount distribution correction curves from the second area to the ninth area.
Step 6, selecting a cyan printing sample sheet, and repeating the steps 3-5 to obtain nine ink quantity distribution correction curves; selecting a magenta printing sample sheet, and repeating the steps 3-5 to obtain nine ink quantity distribution correction curves; and (4) selecting a yellow printing sample sheet, and repeating the steps 3-5 to obtain nine ink quantity distribution correction curves.
And 7, fitting the 36 ink amount distribution correction curves obtained in the steps 5 and 6 into an ink amount distribution correction curved surface (see fig. 3), adjusting the ink amount distribution correction curved surface into a plane, correcting the electronic original according to the corrected data, and adjusting the offset printing equipment.
Fig. 3 is a schematic view of the ink amount distribution correction curved surface in the present embodiment.
The test method for the corrected offset printing apparatus was as follows:
and (4) manufacturing a lithographic printing test plate according to the corrected electronic manuscript, repeating the steps 2-7 in the correction method to obtain an ink amount distribution correction plan, and then successfully correcting.
Effects and effects of the embodiments
According to the correction method for a printing apparatus of the present embodiment, a planographic printing test plate having the same page content as an electronic original is manufactured, printing sheets of different ink colors are printed by using a printing apparatus equipped with the planographic printing test plate, each sheet includes a plurality of regions having different ink rates, one sheet is selected, spectral reflection densities of data points corresponding to scale marks on the sheet in each region of the sheet are measured, the spectral reflection density data of each region is grouped, a plurality of groups of reflection density data are obtained, one group of reflection density data is selected, one of other data in the reflection density data and a minimum density value are taken into a dot area coverage ratio calculation formula each time, a plurality of dot area coverage ratio data are obtained, the obtained plurality of data are input to a correction program, and an ink amount distribution correction curve is obtained by fitting, different groups of reflection density data are selected and are respectively fitted repeatedly to obtain a plurality of ink quantity distribution correction curves, so that points are taken from each area on a printed sample sheet, and the accuracy of the ink quantity distribution correction curves is ensured to the maximum extent. The method comprises the steps of selecting printing samples with different ink colors, respectively and repeatedly measuring to obtain a plurality of ink amount distribution correction curves, fitting all the obtained ink amount distribution correction curves into an ink amount distribution correction curved surface, correcting the curved surface into a plane, correcting the pixel value of an electronic manuscript according to the plane, and meanwhile, enabling the plane to serve as a standard for correspondingly adjusting the printing equipment, so that the ink amount of the printing equipment can be adjusted more accurately by a user, and the problem of uneven ink colors when the printing equipment prints large-breadth or large-area solid printing products is effectively solved.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (4)
1. A method of correcting a printing apparatus for printing unevenness in color of printing ink, comprising the steps of:
step 1, manufacturing a lithographic printing test plate consistent with the layout content of an electronic manuscript to be printed by utilizing a CTP technology;
step 2, printing on each unit of the printing equipment in sequence by using the planographic printing test plate to obtain a plurality of single-color printing samples, wherein the ink colors of the single-color printing samples are different, each printing sample comprises a plurality of areas with different ink rates, the areas extend along a first direction, and scale marks are arranged in the first direction of the single-color printing samples;
step 3, selecting one printing sample sheet, and respectively measuring the spectral reflection density of the data points corresponding to each scale mark in each region, wherein the spectral reflection density data of each region is a group, so as to obtain a plurality of groups of reflection density data, and each group of reflection density data has a minimum density value and other data;
step 4, selecting a group of reflection density data, taking one of other data in the reflection density data and the minimum density value to be brought into a dot area coverage rate calculation formula each time to obtain dot area coverage rate data, and substituting all other data once to obtain a plurality of dot area coverage rate data;
step 5, inputting the plurality of dot area coverage rate data obtained in the step 4 into a correction program, and fitting to obtain an ink amount distribution correction curve;
step 6, selecting a group of reflection density data each time, repeating the steps 4-5, and respectively obtaining a plurality of ink quantity distribution correction curves;
7, selecting the printing sample sheets with different ink colors each time, and repeating the steps 3-6 to respectively obtain a plurality of ink amount distribution correction curves;
and 8, fitting the ink amount distribution correction curve obtained in the steps 5, 6 and 7 into an ink amount distribution correction curved surface, adjusting the ink amount distribution correction curved surface into a plane, correcting the pixel value of the electronic original according to the plane, and correspondingly setting the printing equipment.
2. The correction method for a printing apparatus according to claim 1, characterized in that:
wherein the calculation formula of the dot area coverage rate is as follows
Or
In the above formula, alpha is the dot area coverage, DminIs the minimum density value, D, in the reflected density dataSN is a correction coefficient for any one of the remaining data in the reflection density data.
3. The correction method for a printing apparatus according to claim 1, characterized in that:
wherein the ink color comprises black, cyan, magenta and yellow.
4. The correction method for a printing apparatus according to claim 1, characterized in that:
wherein, in step 3, the spectral reflection density is measured using a spectrophotometer or a reflection densitometer for printing.
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Citations (7)
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| JP2002016806A (en) * | 2000-06-30 | 2002-01-18 | Fuji Photo Film Co Ltd | Method and device for creating gradation correction curve |
| JP2002257631A (en) * | 2001-02-28 | 2002-09-11 | Dainippon Printing Co Ltd | Colorimetry analytical apparatus and method |
| JPWO2006051903A1 (en) * | 2004-11-15 | 2008-05-29 | 三菱重工業株式会社 | Pattern color tone control method and apparatus |
| CN101284445A (en) * | 2008-05-29 | 2008-10-15 | 西安理工大学 | Ink resetting method based on JDF digitalization process |
| CN106541702A (en) * | 2016-10-27 | 2017-03-29 | 杭州电子科技大学 | A kind of printing quality corrects system and method |
| CN106585090A (en) * | 2016-11-24 | 2017-04-26 | 杭州电子科技大学 | Detection and correction method for printing dot area increase values |
| CN107796773A (en) * | 2017-11-30 | 2018-03-13 | 上海紫江彩印包装有限公司 | A kind of control method of intaglio printing spot color half tone image quality |
-
2021
- 2021-01-21 CN CN202110080650.1A patent/CN112918074A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002016806A (en) * | 2000-06-30 | 2002-01-18 | Fuji Photo Film Co Ltd | Method and device for creating gradation correction curve |
| JP2002257631A (en) * | 2001-02-28 | 2002-09-11 | Dainippon Printing Co Ltd | Colorimetry analytical apparatus and method |
| JPWO2006051903A1 (en) * | 2004-11-15 | 2008-05-29 | 三菱重工業株式会社 | Pattern color tone control method and apparatus |
| CN101284445A (en) * | 2008-05-29 | 2008-10-15 | 西安理工大学 | Ink resetting method based on JDF digitalization process |
| CN106541702A (en) * | 2016-10-27 | 2017-03-29 | 杭州电子科技大学 | A kind of printing quality corrects system and method |
| CN106585090A (en) * | 2016-11-24 | 2017-04-26 | 杭州电子科技大学 | Detection and correction method for printing dot area increase values |
| CN107796773A (en) * | 2017-11-30 | 2018-03-13 | 上海紫江彩印包装有限公司 | A kind of control method of intaglio printing spot color half tone image quality |
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