Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F33/00—Indicating, counting, warning, control or safety devices
  • B41F33/0036—Devices for scanning or checking the printed matter for quality control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41P—INDEXING SCHEME RELATING TO PRINTING, LINING MACHINES, TYPEWRITERS, AND TO STAMPS
  • B41P2233/00—Arrangements for the operation of printing presses
  • B41P2233/50—Marks on printed material
  • B41P2233/51—Marks on printed material for colour quality control

Definitions

• the invention relates to a method for testing graphical printing on a substrate as well as a device for implementing the method.
• the invention will be more particularly described with regard to a printing on paper, without being limited thereto.
• the invention applies in fact to printing on any type of substrate, paper, plastic, glass, fabric, flat or embossed (three-dimensional volumes) etc.
• the invention relates to all types of contact printing processes such as offset, screen printing, flexography, rotogravure, digital printing, whose printing results are listed in the ISO 12647 23/1 1/2004, and more particularly ISO 12647-2 for offset, ISO 12647-6 for flexography, ISO 12647-5 for screen printing, and ISO 12647-4 for gravure printing.
• the invention also relates to contactless printing, however specific to digital printing considered in ISO 12647-7.
• the invention does not concern non-contact printing by photocopier and projection machine (laser or ink jet) such as an office printer, which are covered by the ISO 12647-8 standard. It is known to appreciate the print quality of a graphic on paper, by comparing this graphic with reference elements, such as colorimetric control strips.
• the European patent application EP2008818 discloses a method for densitometrically and spectrally measuring color elements to regulate the amount of ink provided by inking zones on a print.
• the control system implemented is a closed-loop system that opens and closes ink segments with respect to setpoint values.
• the measuring method is operated by technical means without intervention of the eye of an observer who can be the operator of the machine.
• the method described in this document relates exclusively to offset printing which provides ink delivery by zones, but does not cover applications by a different ink supply such as from a screen, a cylindrical cylinder in flexography or rotogravure, or according to digital printing.
• a different ink supply such as from a screen, a cylindrical cylinder in flexography or rotogravure, or according to digital printing.
• other criteria must be verified in order to agree on satisfactory printing and its reproducibility, for example, the image length, the printing pressure, the possible mechanical distortion due to the printing medium substrate and / or the process of printing, the parallelism of the printing cylinders, the surface coverage of the weft dot expressed in inked percentage.
• the object of the invention is therefore to propose a printing test method for a printing machine so that this machine meets the ISO 12647 standard, while providing a reproducibility of the printing result at any time of the one or more production cycles of the machine to define the technical capabilities (limits and possibilities). This process applies to the contact or non-contact machine outside the ISO 12647-8 part of the standard.
• the method of the invention must make it possible to define the limits and the possibilities of reproduction capacity of a given printing technique in relation to the substrate on which the printing is performed. It makes it possible to conduct comparative studies to choose materials and raw materials, in particular for printing media, inks, consumables (offset blanket blanks).
• the method of printing tests with or without contact on a substrate using a printing machine the printing being of the offset type, screen printing, flexography, gravure printing, and the printing being performed on a test substrate constituting the type of substrate on which the machine is intended to print, the method comprising a step printing on the substrate using the printing machine according to initial machine setting conditions, a step of analyzing the printing with respect to a reference test protocol, is characterized in that than
• the test substrate comprises a plurality of graphic evaluation elements printed on the test substrate, the elements being distinct in their shapes and their colors and including for some of the halograms,
• one of the graphical elements to be analyzed consists of a plurality of identical geometrical shapes, of the square or other type, the color of each shape of which is a raster black with a different frame according to an incrementation, each shape comprising a graphic, such as a number, which is viewable on the test substrate in the event of a fault.
• Visual refers to the test protocol, an appreciation of the graphic elements by the human eye.
• viewable in the sense that the graphic appears visually according to a colored gray in the form with background halftone incremented 5% in 5% for example.
• this graphic is colored because its appearance corresponds to a defect relating to the setting of the color combination to elaborate the black raster and in particular a lack of adjustment on the color of the graphics appearing on the black background raster.
• these colors are composed of cyan, magenta and yellow, printed "trapped" (term of trade) in a reserve (the full graphic form) of the black screen.
• the percentage of the raster obtained by the colors black, cyan magenta and yellow comes from the target values of the standard.
• the graphic design (a number) represents an image for which a percentage of points (corresponding to a surface coverage) is attributed, this percentage being representative of the tones of each color. It is for this reason that the invention makes it possible to visually identify the distortions of a tonal value when the image takes on a colored tendency. It can be deduced, for example, that there is too much cyan in the target values such as 15% to 35% because, in each of the raster forms corresponding to these raster percentage values, an image appears (FIG. percentage of raster: respectively 15, 20, 25, 30, 35) which is colored in cyan.
• the surface covers will then be corrected electronically during the preparation of the printing matrix via the computer tool called "Raster Image Processor” (RIP).
• RIP Raster Image Processor
• the process is indeed of interest only for the four-color process, the color printing.
• the geometric shape can be a square, a round, an ellipse or any other shape. This shape must be full of black raster color.
• the print was programmed to develop this graphic element: a background of black raster with a graphic drawing in stoned.
• This process which presents specific graphic elements and which must be analyzed according to a predefined chronology of observation and intervention, with, first of all, the analysis of the forms in black raster and figures in gray colored (which appear in case of default), can be used to derive deviations in various print parameters from ISO 12647 for each type of contact printing.
• the method of printing tests said without contact on a substrate using a printing machine is the same, the method corresponding to the printing results of the ISO 12647-7 standard outside the ISO 12647-8 part of that standard. Therefore, the method allows a simple "glance" on the graphical element shapes raster black and numbers in gray color, to validate or not the test print. This graphic element makes it possible to know whether the printing meets the standard or not. If a graphic appears in the raster black background, then a fault is detected, the print does not meet the standard.
• This process is very advantageous because it makes it possible to have an anticipatory approach, well before the production phase, in particular during so-called calibration operations, in order to avoid potential risks that could be encountered in production.
• the corrective step in case of malfunction in production can be provided by the method of the invention.
• the sequence of geometric shapes with black halftone and colored gray numbers is the translation of a curve of the spectral and densitometric measurement in comparison with target ISO values, the sequence of the forms corresponds to a percentage incrementation of the screen, for example from 5% to 5%, in particular with the 40% screen value.
• the graphic in case of appearance of the graphic in a geometric form of raster black and numbers in colored gray, the graphic is a number and corresponds to the number of the percentage of the raster.
• the graphic is printed by being distributed on the test substrate in different areas, several of said graphic element consisting of a plurality of forms of black raster.
• the method is carried out using measuring tools, in particular using a densitometer and spectrocolorimeter, for certain graphic elements if a defect has been visually identified on the graphic element of the raster black forms.
• the analysis of at least some of the graphic elements is carried out sequentially in a determined order.
• each graphic element of the graphical printing test method with or without contact corresponds to at least one adjustment parameter of the machine and if one of the graphic elements taken in the sequential order defined by the protocol does not respond not to the reference criteria established by the protocol, the method comprises a step of deducing the setting parameter to be modified on the machine.
• steps of printing on the test substrate, and analysis of the graphic elements are repeated until no defect is detected in the analysis of each of the graphic elements or that the impact of the defect is quantified, the aim being to define the technical capabilities, limitations and possibilities of the printing process.
• one of the graphic elements to be analyzed consists of a scale composed of a multitude of lines, each line being obtained by the superposition of all the printing colors of the machine, and arranged near at least one of the edges of the substrate in the vertical direction.
• This scale makes it possible in particular to validate the identification (color overlay) of the colors when it presents a colorimetric neutrality, detect a deformation of the substrate during printing, give an absolute value of the measurement, especially in the case of anamorphosis techniques.
• vertical refers to the reading direction of the substrate by an observer who reads in a vertical direction from top to bottom or from bottom to top the substrate when the substrate is positioned opposite the observer.
• one of the lines extends so that this extension corresponds to the succession of each of the printing colors adjacent.
• one of the graphic elements to be analyzed consists of at least four black ink strips respectively and primary printing colors of the machine, the strips being printed in the vertical direction of the substrate, and said element comprises vertically several halftone areas of these color bands, each halftone area being compared with each other.
• This graphic element corresponds in particular to the criterion of distribution of the inking between the beginning of printing and the end of printing.
• one of the graphical elements to be analyzed consists of a graphical form of the square type composed of vertical, horizontal and oblique adjacent lines, and in that several of said graphic element are printed on the test substrate, in particular in part upper and lower, to the different colors of the printing machine (primary color and black).
• one of the other graphic elements to be analyzed consists of at least one diagram of each printing color, the diagram consisting of circular sectors that are rasterized, each of the sectors having a raster different from the others, in particular according to a coverage incrementation of 2 or 5% relative to a given screen, preferably diagrams are printed in the upper part and in the lower part of the test substrate. This allows in particular to define the technical capacity of printing a frame with a given screen.
• the invention also relates to a printing test device for the implementation of the method.
• This device comprises computerized support means on which the evaluation graphic elements to be printed are stored, as well as means for supporting a database of analysis data comprising for each graphic element the manner of analyzing said element once printed in order to deduce the eventual defects and to indicate the parameters of the machine on which a setting action is to be performed.
• the database constitutes a written explanatory note, preferably whose support means is in the form of a computer file accessible by computer and accessible on any type of suitable medium of the CD-ROM type, USB key, site Internet.
• the method and its implementation device make it possible to detect the adjustment defects of the printing machine, whatever the type of printing and the nature of the substrate, and to provide repeatability in the printing process. , to define its technical capacity for restitution by indicating the limits and possibilities.
• FIGS. 1 to 5b illustrate the graphical elements taken independently and constituting the evaluation means of the test protocol of the invention
• FIG. 6 illustrates the graphical test printing of the invention including all of the graphic evaluation elements.
• the printing test method of a printing machine according to the invention consists in printing graphic test elements on a test substrate from an implementation device developed according to the invention.
• the printing machine incorporates a matrix which will be of distinct type according to the printing technique, for example offset plate, rotogravure cylinder, screen printing, flexographic printing.
• the test substrate is the type of substrate on which the machine is intended to print. This is for example paper, cloth, glass, etc.
• the method of the invention consists in printing a test form on the test substrate in order to analyze by visual estimation and measurements using appropriate tools of the densitometer and spectrocolorimeter type, specific graphic elements according to the invention for to deduce deviations in various print parameters from ISO 12647.
• the printing step is carried out on the basis of initial machine setting conditions to be tested, that is to say to check whether the machine meets the ISO 12647 standard and / or to know its capabilities.
• an observer who is preferably the operator of the machine or a person skilled in the art, visually analyzes first and then, if necessary, using standard measuring instruments, the test illustration printed on the basis of an analysis protocol.
• the illustration of the invention with the specific graphic elements very advantageously leads to bringing together on the single substrate all the elements useful for the analysis.
• the analysis protocol includes several evaluations, each in relation to a specific graphic element.
• the evaluations are made for certain graphic elements in a sequential order determined.
• the analysis protocol includes for each evaluation, explanations on:
• the interest of the process is to allow the naked eye to visualize extremely quickly several graphical elements to deduce the defects, the observer having a panoramic view of the substrate and able to analyze with intellectual vivacity.
• the defects detected by the analysis protocol of the invention relate to the following information, without being exhaustive:
• circumferential refers to the direction of advancement of the substrate in the printing machine from the beginning of printing to its end. This term is also translated by the notion of vertical direction on the printed substrate.
• the reproducibility characteristics of the printing process expressed for example by the percentage of surface coverage in relation to the screen. It is recalled that the line is expressed in number of lines per inch or cm (for example 150 lines per inch or 60 lines per cm)
• the thickness of the ink film deposited and measured in densitometric values from the optimal contrast of the inking The spectral values of the colors from an ink thickness, also called ink charge, optimized
• the dimensional values for the graphic elements are given hereinafter by way of example for an illustration printed on a test substrate of dimensions 800 mm x 1100 mm.
• the graphic element 1, illustrated in detail in FIG. 1, consists of at least four ink strips respectively of black color 10 and primary colors, cyan 11, magenta 12, and yellow 13, the strips being printed in parallel and contiguous, in the vertical direction of the substrate, or still referred to in the usual manner "circumferential" sense, meaning corresponding to the delivery of the ink on the substrate during the printing process.
• the number of strips corresponds to the total number of colors used by the printing machine, here four. In practice, there would be as many bands as colors able to be delivered by the machine.
• the printed strips preferably extend over the entire height of the substrate.
• the colors of the substrate edge side towards the interior of the substrate are set in the following order: black, cyan, magenta, yellow.
• Each vertical color band is contiguous to the other and has a given width equal for example to 6 mm.
• the width of the strip is adapted to be measurable using a densitometry apparatus or spectrocolorimetry.
• raster zones arranged transversely to the strips 10 to 13, such as four zones 14, 15 and 16 and arranged respectively in the upper part of the substrate, in the middle part, and in the lower part extend according to the width of the four strips.
• the halftone areas extend across the width of the four strips to have a halftone surface by color.
• the height of the screened area is adapted for its analysis with a measuring device. It is for example of the order 5 mm.
• the zones are 80% screened.
• the halftone zones are intended to circumferentially measure the surface coverage as a function of the ink charges (or density) of each color, that is to say to ensure the homogeneity of the ink deposit as as you go through the printing process.
• the measurement is made in a known manner using the Murray Davis formula which is integrated into the measuring apparatus.
• measurement points are located, for example, here on the four distinct halftone areas 14A, 15A, 16A, 17A, adjacent to four zones 14 to 17 which are not framed.
• the surface coverage is measured. If a measurement deviation of the surface coverage is found, for example between the zone 14A and the zone 15A, the operator will intervene on a mechanical adjustment of the machine as for the distribution of ink.
• the graphic element 1, by its first band, is arranged at a precise distance from the edge of the substrate so that the strips are not deformed at the edge of the substrate during printing, not distorting the observations to the using the measuring device.
• the observer will be able to detect a defect in the ink distribution by evaluating the criticality of the surface coverage and will act on the machine to rebalance the ink charge circumferentially.
• the graphic element 2 to be printed is in the form of a square by color, which will be called an optical amplifier.
• each square is made of a combination of at least vertical and horizontal lines 21, and also oblique lines 22.
• the square comprises a frame having two opposite horizontal sides 23 and 24 consisting of vertical lines 20, and two opposite vertical sides 25 and 26 consisting of horizontal lines 21.
• the center 27 of the square, inside the frame, is formed of oblique lines 22.
• the square has dimensions sufficient to visually translate the defects.
• the square is of the order of 3 or 4 cm.
• the thickness of the lines and the pitch between the lines have dimensions adapted to the type of printing substrate, in order to observe the defects on said substrate.
• the pitch is 0.105 mm.
• This graphic element makes it possible to detect certain defects on the printing machine and / or the substrate which are listed below without being exhaustive.
• the machine and / or the substrate do not exhibit the defects mentioned below when the square is of neutral color (FIG. 2b), that is to say when no vertical, horizontal or oblique line is viewed.
• the graphic element 3 visible in FIG. 6 and opposite the partial FIG. 3a and the detail view of FIG. 3b, is a scale composed of a multitude of lines 30 spaced at a constant pitch.
• the scale 3 is positioned vertically (circumferentially) on the printed substrate (FIG. 6) and arranged on both vertical sides of the substrate.
• the scale 3 is close to the edge of the substrate without being too close, for example at least 8 mm from the edge, to promote the ability to disengage or the separation of the inked surface vis-à-vis the matrix.
• the scale or the graphic element 3 is located near the edge of the substrate, being systematically arranged before the graphic element 1 from the edge of the substrate in the horizontal direction toward the center of the substrate.
• the scale is formed of a multitude of horizontal lines spaced at a constant pitch along the vertical.
• the width of the scale that is to say the length of a line according to the horizontal, is for example of the order of 2 to 3 cm. The size must be sufficient to appreciate each trait.
• the lines of the scale are at least four-color, that is to say, according to a superposition of the four colors cyan, yellow, magenta and black.
• each stroke will consist of the combination of all these colors.
• the scale 3 extends over the entire height of the substrate in order to identify any circumferential printing defects with regard to the entire vertical extension of the substrate.
• the scale has a vertical height so that it can be measured by a length measuring tool, such as a ruler using the metric system. Indeed, in case of detected fault, the length of the scale will be different from that expected without defect.
• a length measuring tool such as a ruler using the metric system.
• the length of the scale will be different from that expected without defect.
• the scale is configured so that its printing corresponds for example to 10 cm while once printed, the measurement is 10.08 cm, a defect will be detected with a length variation of 0.08 cm.
• Measuring the length of the scale makes it possible to check the anamorphosis during bending of clichés (matrices) in flexography for example.
• the scale 3 has references numbered 31 according to integers starting from 1, here the number 9, and in numerical order. Each reference is arranged at a line of the scale which extends on the side of said scale. This extended feature is later named “referenced trait”.
• the referenced line thus has an extension whose magnitude relative to the width of the scale is for example of the order of one third of the width of the scale.
• each referenced line is constant, each spacing step incorporating a constant plurality of lines.
• the reference 1 starts at the first line at the upper end of the substrate.
• the referenced line corresponds to a superposition of the printing colors except at its end 32 opposite to the scale for which each of the printing colors succeeds one another in an adjacent manner, for example in a width of 1 mm for each of the colors. colors.
• These aligned segments of the different colors not superimposed will facilitate the appreciation of the differences in printing lengths and the quality of superposition of colors called registration in terms of trade.
• These aligned segments are observable with a magnifying thread count or magnifying glass.
• this scale makes it possible to validate the identification (superposition of colors) of the colors when it presents a colorimetric neutrality.
• the graphic element 4 with reference to FIG. 4, is in the form of a circular sector diagram 40.
• the diagram corresponds to an inking zone of the machine.
• Diagram 4 is of a given color.
• a graphic element 4 is printed on the test substrate per printing color.
• four graphic elements 4A to 4D are arranged for each of the three primary colors and for black, respectively.
• the diagram 4 consists of a plurality of sectors 40 of a specific screen, each of the sectors having a screen different from the others.
• the sectors are presented adjacent to each other following each other in a coverage incrementation of, for example, 2 or 5%.
• the sectors are large enough to be measured with a densitometer or spectrocolorimeter.
• This technical capacity information is only analyzed last, after having analyzed all the potential fault parameters and that these have been neutralized. The operator will return to the analysis of this graphical element 4 after analysis of all the other elements.
• the visual test is conclusive, a priori therefore without defects, when the gradient of color by a gradual framing of said graphical element appears regular, therefore without missing apparent points and when the outline of the points forming the screen is well defined and not fringed, the outline being visible with a son-account.
• This graphic element allows the measurement of the surface coverage with a densitometer but above all a visual appreciation of the balance between the water / ink mixture in the application of the offset, it is also used to evaluate the printing pressure.
• the 80% screened area allows the calculation of the optimum contrast of the inking.
• the graphic element 5, illustrated in FIGS. 5a and 5b, provides a simulation of the colored gray scales. It can only be used for four-color process.
• the graphic element 5 is composed of a plurality of identical geometrical shapes, of the square type, the color of each of which is a screened black, with a different frame for each in order to form a gradient of gray, thus going from black to light gray. , even white.
• the incrementation of the frame is for example 2%.
• each geometric (square) shape is designed so that it is visualized in the square, when a defect in the printing machine exists as for the gray balance, a number.
• the number corresponds to the percentage of the screen. The appearance of the number indicates the detection of a defect in the gray balance and the number itself allows to locate the corresponding place on the curve of the gray scales.
• FIG. 5a there are illustrated in FIG. 5a four squares 50 to 54 of gray scales for which a number appears, while FIG. 5b shows squares of distinct halftone with a numberless background. The number is large enough to be visible to the naked eye and measured spectrally.
• the gray balance is not balanced. It will be necessary to intervene on the machine or on the curve of the gray scales during the realization of the matrix of impression.
• the dominant color of the number appearing in the square reflects a defect related to the other colors or to the dominant color
• the defect can be located at the level of the yellow itself which is too strong in intensity (the intensity corresponding to the component L in the color model L * a * b), or at the level of the other colors, such as cyan and magenta which are too weak in intensity.
• the device for implementing the method allows for analysis.
• At least two graphical elements 5 will be printed on the one hand in the vertical direction of the substrate and on the other hand in the horizontal direction. Indeed, they will thus be perpendicular to the grippers of the machine to not suffer the inking areas and translate circumferential ink input gaps.
• FIG. 6 shows six graphic elements formed of a plurality of grayscale squares, of which two elements 5A and 5B arranged side by side along the vertical side of one of the edges of the substrate, two other elements 5E and 5F also vertical and side-by-side towards the opposite edge, and two elements 5C and 5D arranged according to the horizontal, respectively in the upper part and in the lower part.
• the elements 5A and 5B on the one hand, and 5E and 5F on the other hand, are adjacent by being arranged head to tail by their screen.
• the first square 55 of the screen of the element 5A or 5E in the upper part corresponds to a 2% screen
• the adjacent square 56 of the element 5B or 5F corresponds to a 100% screen, each graphic element being composed of a number of squares decomposing according to a framing of 2 to 100%.
• the graphic element 6, compared with FIG. 6, comprises several images of the photograph type according to categories of images with a different style, with or without technical difficulties of production.
• the images are preferably printed in the central zone of the substrate, the other graphic elements 1 to 5 being arranged around.
• the printed image includes ink charges in dark tones that can cause risks during the printing phase and post-printing. They serve as an alert if traces of smearing (traces of ink on the back of the substrate) appear.
• the method provides a sequential order of analysis of the different graphic elements.
• defects are detected at each analysis step of an element, they are corrected as and when analyzing the graphical element again until no fault is revealed by said element. The operator can then proceed to the analysis of another element.
• graphic element 1 the ink strips
• graphic element 2 the optical amplifier
• graphic element 6 photographic images.
• the first analysis of the graphical element 5 shapes in black raster and numbers in gray colored with visualization of a graphic on it in case of default, allows to know immediately whether the printing meets or not the ISO 12647 standard.
• this graphical “greyscale” element If no defect is detected on this graphical "greyscale” element, the printing machine meets the standard.
• the other adjacent graphical elements can be checked for any other pre-cited defects. If a fault is detected on this graphical element "greyscale", the machine does not meet the standard, it is absolutely necessary to start a process of correction and adjustment on the machine from the analysis of the adjacent elements and according to a chronological intervention on the machine. If after all the checks on the machine, the operator understands that the machine settings are in fact correct but that defects persist on the test print, he will then intervene on the print matrix to adjust the target values to one. operation called compensation on the halftone values expressed as a percentage. The operator will electronically decrease or increase the surface coverage via RI P.
• the operators could not visually detect the adequacy of the target values with the standard. They used a densitometer to evaluate the percentage of color tone. If they detected a defect, not knowing the initial causes of the defect, they were content to intervene, not on the machine, but on the printing matrix by electronically correcting the target values by the compensation of the surface covers. However, if the malfunction was actually on the machine, no intervention having been made on it and its mechanical organs continuing to be requested abnormally, it could inadvertently cause other incidents in cascades. The invention now makes it possible to remedy this problem.
• test method of the invention proposes a set of different graphic elements described above which should be analyzed one by one to detect possible adjustment faults on the machine, each graphic element being linked to a identifiable parameter on the machine.
• the method of the invention makes it possible to qualify, optimize, validate or invalidate a printing method in relation to a specific printing substrate, and to check its repeatability, in order to to provide a homogeneous production of the first substrate printed last in a production cycle.
• the test protocol comprises on the one hand the graphic evaluation elements to be printed by the machine on a test substrate, and on the other hand explanations on the manner of analyzing the graphic elements. and to identify the parameters to be set on the printing machine, is preferably implemented by the following device.
• the device comprises: computerized support means on which the graphic evaluation elements to be printed on the test substrate are stored,
• the support means of the evaluation graphic elements are loaded into the control system of the printing machine so that the machine can print the illustration 7 of FIG. 6.
• the support means are computerized in the sense that they are present in the form of an electronic file stored on any type of support decipherable by reading means of the computer type.
• the support may for example be a CD-ROM, a USB key, a website, etc.
• the support means of the analysis database may be in the form of a paper document of the book type, or of an electronic file that can be consulted by computer and accessible on any type of suitable medium of the CD-Rom type. , USB key, website.
• the graphic evaluation elements to be printed on the test substrate and the analysis database will be downloadable on the Internet.
• a plurality of defects can be demonstrated by the method of the invention that should be corrected in a specific order to achieve the fastest to neutralize and obtain the desired optimal impression.
• Example 1 corresponds to the first analysis to be performed for the graphical element 5 of the gray scales.
• Examples 2 to 4 relate to other graphic elements of the process of the invention.
• gray balance (graphic element 5), for example 50 with a magenta colored trend. It follows that ISO 12647 is not achieved.
• a spectrocolorimeter is then used and it is deduced whether the intensity is greater on the component L of the magenta or insufficient on the cyan and yellow. If a deviation is found, the compensation curves used to make the print matrix are corrected.
• Example 2 It can be seen that the scale 3 is not colorimetrically neutral. Using a thread count, the registration deviation is evaluated and the color with a length defect is identified. From the analysis database, we proceed as follows:
• the diameters are corrected using compensating elements such as calibrated sheets of different thicknesses;
• the ink charge is checked using the optimum contrast of the inking

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• Accessory Devices And Overall Control Thereof (AREA)
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• Inking, Control Or Cleaning Of Printing Machines (AREA)

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