EP0442322B1 - Method for ink control and zonal presetting - Google Patents

Description

The invention relates to a method for color control and zone-by-zone presetting of ink metering elements in inking units of rotary printing presses, in particular offset rotary printing presses, according to the area coverage determined zone by zone according to the preamble of claim 1.

From DE-OS 29 50 606 and DE-OS 29 50 650 it is already known to scan films or printing plates by means of optoelectronic measuring devices with respect to their area coverage in color zones and, after integration or summation of the scanned values, presetting information for color metering elements, for example for color slides to be calculated in inking units of offset rotary printing presses. The scanning elements each record the width of a color zone and have a dimension of 5 mm x 720 mm on a printing press of a normal size. By appropriate movement of the scanner or the templates to be scanned, i.e. of the film or the plate, the presetting values can thus be derived in each case in a color zone from the area coverage. It has been shown in practice that the presetting values to be determined in this way are not sufficiently precise, so that complex readjustments and corrections are required, which, among other things, lead to an increased amount of paper waste and thereby increase the printing time.

The object of the present invention is to create a method in order to be able to precisely determine and influence the ink zone presetting values and the local ink requirement for the overprinting of a plurality of printing inks.

EP 0 143 744 A1 discloses a method and a device for assessing the print quality and / or for regulating the color guidance in an offset printing machine. The device has a film or plate scanner for two-dimensional, raster-shaped and checkerboard-like detection of the area coverage on one print template or on several print templates. A computer arrangement for zone-by-zone determination of the color requirement in each color zone has a plurality of weighting computers and an associated memory. The weighting calculators should weight the color for each picture element depending on the area coverage, the environment and foreign colors. EP 0 143 744 A1 does not show how the printing inks influence one another when printing on top of one another and how accordingly ink acceptance problems, such as those that can arise when printing on top of one another, can be compensated for or prevented.

This object is achieved by the application of the features of the characterizing part of claim 1 for the invention Procedure solved. Claims 2 to 10 represent advantageous developments of the method.

With the aid of the method according to the invention, the presetting values for the ink zone metering can be determined precisely, since, for example, small areas such as fine structures (grid, fine line) and coarse structures (solid areas) can be distinguished on the printing form or on the film or on the printing sheets. Thus, using the philosophy on which the invention is based, the lower consumption in the case of full-tone areas in comparison to screen-tone areas or fine-line areas in the form of correction factors can be taken into account when determining the color zone setting values, preferably by appropriate weighting of the area parts to be printed or the scanning pattern. In a further development of the invention, correction factors depending on the parameter state of the printing process (for example paper, ink, dampening solution composition, printing speed, inking characteristics, etc.) can be modified and stored parameter-related via a self-learning system or via a so-called expert system, for example for repeat jobs. Furthermore, using the method according to the invention, it is possible to take into account color acceptance disturbances in color printing which result from the fact that with the method according to the invention the area proportions of area portions printed on one another or of the scanning grid printed on one another can be determined. With the previously known method for recording the printing area proportions of color printing plates, the position of adjacent areas of superimposed color areas could not be distinguished, so that it was not possible to take this into account in the determined presetting values. The proposed method, on the other hand, makes it possible to determine printing areas printed on one another in the individual colors. From the values that can be determined in this way, it is possible to derive the strength of the ink acceptance disturbances for the individual color zone.

The color presetting can thus be optimized by means of correction factors when determining the color presetting values. Knowledge of the expected ink acceptance disturbance is also of interest for color control or color regulation. By taking into account the correction factors that can be determined according to the invention, the dynamics of the color flows when the color flows change in individual colors or in color zones can be included.

Furthermore, the invention advantageously enables the elimination of stenciling effects, since the novel detection makes it possible to make predictions about stenciling to be expected. The stenciling effects can be counteracted by the lateral rubbing in the inking unit, preferably by means of a paint grinder. Another advantage lies in the fact that in the detection according to the invention of smaller areas, compared to the previously usually recorded areas, the previously used hardware can be used in a modified form. An important advantage of the invention results from the fact that the scanning grid values recorded from the printing area portions are weighted within the color zone before the sum is formed, and that the color requirement per color zone can thereby be optimized by means of correction factors. According to the invention, prior to the summation per color zone, a determination and evaluation of the position of successive and adjacent areas and possibly the same positions or positions of the scanning grid in the associated different-colored templates is carried out, from which correction factors can be derived which are necessary for the color zone presetting or color control ( or regulation) bring advantages. The weighting and calculation of the corrections is carried out in a separate computer or in a computer already present in the machine. In practice, an empirical determination of the correction factors will often be offered, which are then held in a memory in order to be taken into account for the raster areas just scanned in accordance with the scanning sequence.

Fig. 1

in schematischer Darstellung ein Blockschaltbild einer Vorrichtung, mit der das erfindungsgemäße Verfahren durchführbar ist;

Fig. 2

ein Drucksujet in Form einer 2 und

Fig. 3

ein durch das Farbwerk angeliefertes Farbprofil, daß in erfindungsgemäßer Weise in Abhängigkeit von den ermittelten Abtastwerten, die zuvor vorzugsweise korrigiert wurden, in X- und Y-Richtung, d.h. zweidimensional gesteuert vergleichmäßigt wird.

The invention is described in detail below using an exemplary embodiment, reference being made to the accompanying drawings. In these show:

Fig. 1

a schematic representation of a block diagram of a device with which the inventive method can be carried out;

Fig. 2

a printed subject in the form of a 2 and

Fig. 3

a color profile supplied by the inking unit, which in the manner according to the invention is made uniform in the X and Y directions, that is to say two-dimensionally controlled, as a function of the ascertained sample values, which were preferably corrected beforehand.

A schematically illustrated printing machine 1, for example an offset rotary printing machine for printing on print carrier webs or for printing sheets, is connected to an ink zone presetting device 2 which not only shows the electrical or electronic control components but also the mechanics required for zone-by-zone presetting of metering elements Color sliders included. A color requirement determination computer 3 is connected to the ink zone presetting device 2, and the determined information about the ink coverage of each zone can be supplied by a film or plate scanner 4. It is understood that the values scanned by a film and plate scanner also e.g. can be stored in a tape or a floppy disk, from which these can be read into the color requirement determination computer 3.

The film or plate scanner 4 is equipped with at least one row of scanners. For the sake of simplicity, only one scanner 5 or 6 is shown in FIG. 1. In the manner according to the invention, the scanner 5 or 6 is constructed such that a scanning grid of preferably 2 mm × 2.5 mm is detected. The result of this is that, in comparison to the color zones which are usually 20 mm to 60 mm wide, viewed in the X direction, a larger number of scanning grids 7 lying next to one another can be detected within each color zone.

Using the principle on which the invention is based, in contrast to the prior art, the scanner 5 or 6 should be significantly smaller in the X and Y directions than the color zone. The evaluation accuracy becomes better the smaller, i.e. the finer the scanning grid 7. As stated, a preferred size of the scanning grid 5, 6 is 2.5 mm in the X direction and 2.0 mm in the Y direction. For the sake of simplicity, the scanner 5 or 6 required to detect a scanner grid 7 is only shown once, but seen in the X direction, a larger number, approximately over the width of a color zone, of such scanners 5, 6 are arranged in the form of a line .

In Fig. 1 two printing templates 8, 9 are indicated, which can be scanned simultaneously or in succession, for example for carrying out a two-color printing. The templates 8, 9 can represent both plates and films. Ink zones 10, 11 are indicated on the printing templates 8, 9, which can be improved or refined in comparison to the prior art. Due to the smaller dimensions of the scanning grid 7, a much more precise determination of the color coverage can be made compared to what is known. It is understood that when scanning the templates 8 and 9, only a single row of several scanning elements 5 can be used, so that a further row of scanning elements 6 can be saved if the scanning of the templates 8, 9 takes place in succession. The values detected by the scanners 5 and 6, which interpret the area coverage, reach the electronics of the film or plate scanner 4 and together with these values, the X and Y coordinates of the respective one of the scanners 5 (X, Y-) and 6 (X ', Y') in an XY coordinate detection logic and processed. The values determined by the film or plate scanner 4 can be further processed in an area coverage detection logic 13. Furthermore, a color coverage detection logic 14 is provided, with the aid of which the XY values of scanning grids of the same position are compared between different (color) originals 8, 9 in order to determine whether color areas are printed one above the other, so that Corresponding correction values must be determined which have an influence on the ink zone presetting in order to compensate for the ink acceptance disturbances which frequently occur due to overprinting. The values prepared in the XY coordinate detection logic 12, the area coverage detection logic 13 and the color coverage detection logic 14 are sent to a weighting computer 16, which includes a weighting memory, which is not described in more detail. Empirically determined correction factors can be entered via an input device 15. Alternatively, it is also possible to calculate correction factors for the individual grids.

The values previously supplied in a simple manner from a film / plate scanner 4 to the color requirement calculation computer 3 are thus, according to the invention, acted upon by the weighting computer 16 with a correction factor or a correction value for each scanning grid prior to the summation of the scanned values in a color zone the weighting computer 16 is determined on the basis of the information supplied to it in the manner described above.

The presetting values determined in this way for each ink zone 10, 11 then arrive at the corresponding inking unit of the printing press 1 in order to preset the ink metering elements in the form of ink slides or ink knife sections. As explained, the presetting according to the invention is considerably more precise compared to what is known, so that there is less waste and a shorter pressure phase.

Information is preferably determined from the corrected scanning information in a stenciling computer 17, which enables the rubbing of the color to be applied in two dimensions (XY) to be influenced in a novel manner. That is, according to the invention, for example, a grater 21 (axially oscillating distributor roller) is influenced with regard to its phase position, ie the use of the axial displacement, in the stroke and in the distributor frequency in order to distribute the paint to be applied in the XY direction. Taking into account the scanned Values from which the subject to be printed can be derived are thus distributed to the ink to be applied to a printing plate (not shown) in the printing press 1, preferably by means of a scraper, during the inking process in the X and Y directions, which avoids the feared stenciling leads.

A further improvement in the presetting of the ink metering elements results from the fact that, with the aid of a subject computer, 20 investment times and investment time of a respective jack 22 of an inking unit of the printing press 1 (not shown in more detail) can be controlled with regard to the investment time on the next inking roller and the investment time. This results in a favorable influence on the color distribution in the Y direction, in particular in connection with the friction device 21 controlled according to the invention. Thus, not only is the color requirement per color zone taken into account, as in known systems, but the respective location, e.g. within a color zone, i.e. by controlling the grater 21 and / or the ink lifter 22, the ink is also correctly placed and rubbed in the plate circumferential direction (26 or Y).

Within the scope of the invention it is also possible to use as output values for determining the zonal default settings instead of scanning printed templates 8, 9 from an electronic image memory 19 in which the image information (pixels) specified in electronic image processing is present. From DE-OS 38 04 491 it is already known to evaluate such image information (pixels) in order to calculate average density values, but it is extremely disadvantageous in the state of the art that this results in very large memories, which are currently not practically available with complex processing logic are required. In the context of the invention, it is therefore advantageous to compress such image information, ie to combine it into larger surface units, for example in the order of the scanning grid area 7, and to further process these values using the method according to the invention, ie to provide them with correction factors.

A further embodiment within the scope of the invention results from the fact that the print images produced by the printing press 1 are scanned, for example densitometrically or colorimetrically, and that the values obtained therefrom can be fed to the color requirement determination computer 3 by switching on a print carrier scanning logic with a self-learning system or with a so-called expert system, so that the presetting values can be continuously refined during the proofing and also during the production printing phase.

Furthermore, the use of the method according to the invention also allows the ink accumulation in the inking unit, which is inevitable due to the cylinder pit pass, to be taken into account in such a way that between the start and end of printing a corresponding influence on the operating points of the lifter or the lifting roller 22 and a control of the oscillation of the grater 21 he follows. According to the invention, the effect of an uneven color distribution in the printing direction can thus be reduced or eliminated, taking into account the subject to be printed.

Fig. 2 shows a subject 23 in the form of a 2. From this representation it can be seen that within a schematically indicated color zone 10 there is a larger number of scanning areas, as indicated at 7, since according to the invention the scanning grid 7 is smaller, preferably substantially is smaller than the width of the color zone 10 (2.5 mm x 2 mm). Thus a much more refined detection of the printing and non-printing areas within a color zone can be carried out, i.e. this is quasi rasterized.

Fig. 3 illustrates on a plate 24 a "color mountain or a color mountain" 25 that according to the invention in the direction of arrow 26 (Y direction) and in the direction of arrow 27 (X direction) in the manner described above Use of the controlled rollers 21, 22 can be placed (applied) and displaced, so that in Compared to the prior art, there is a significant improvement in the coloring depending on the subject to be printed.

The presetting and control data determined or corrected by the weighting computer 16 can be visualized, e.g. on a screen or in the form of a log.

A further development of the invention is that a computer network between weighting computer 16, subject computer 20 and stencil correction computer 17 on the one hand and a self-learning system or an expert system 18 on the other hand is that this self-learning system or expert system 18 previous orders with all automatic and manual settings and saves corrections for repeat orders and, on the basis of the corrections, modifies the control parameters in weighting calculator 16, subject calculator 20 and stencil correction calculator 17.

Claims (10)

1. Process for ink control with ink dosing elements in inking units of a printing machine (1), in particular an offset printing machine, having a film or plate scanner (4) for two-dimensional, scanning and chessboard pattern detection of surface coverage, with means for two-dimensional, controlled ink distribution in each ink zone (10, 11), taking into account the local ink requirement in each ink zone (10, 11), and with a computer arrangement for the zone-wise determination of ink requirement which has a weighting computer (16) equipped with a weighting memory, in which the ink coverage values produced by the film or plate scanner (4) are corrected in accordance with the two-dimensional scanning in the respective ink zone (10, 11), the correction being made before summing the ink coverage values determined in the respective ink zone (10, 11) by a scanning screen (7), an X-Y coordinate determination circuit being assigned to the film or plate scanner (4) for detecting the position of the scanning screen (7), characterised in that in the weighting computer (16) cooperating with this film or plate scanner (4) in dependence on the ink coverage values determined from the detection of scanning screens from different originals (8, 9) with the same X-Y coordinates a correction of the presetting values is made before the summing for compensation or prevention of ink absorption interference due to ink surfaces printed one above the other.
2. Process according to claim 1, characterised in that the presetting and control values are corrected in accordance with the weighting of the individual scanning values from a scanning screen (7) according to full tone and screen.
3. Process according to claim 1 or 2, characterised in that to control or distribute the ink to be applied in the direction of the ink zones (10, 11), i.e. in the circumferential direction (26) of the cylinder, the time and/or duration of abutment of a lifter (22) are controlled by a subject computer (2).
4. Process according to claim 1 to 3, characterised in that a changing brayer (21) is controlled with regard to changing phase position, frequency and lift by means of a matrix computer (17) in accordance with the expected ink profile, conditional on the subject, in the X-Y direction (26, 27) of a copy (24).
5. Process according to one of the preceding claims 1 to 4, characterised in that brayers (21) and/or lifters (22) are controlled for the two-dimensional ink rubbing or distribution taking into account the path of the cylinder groove and the subject.
6. Process according to one of the preceding claims 1 to 5, characterised in that the correction factors for this scanning surface or scanning screen (7) are modified by a printing carrier scanning logic system (18) having a self-learning system or an expert system, and stored for repeat orders.
7. Process according to one of the preceding claims 1 to 6, characterised in that there is a computer network between the weighting computer (16), subject computer (20) and matrix correction computer (17) on the one hand, and a self-learning system or an expert system (18) on the other hand, in that this self-learning system or expert system (18) stores previous orders with all the automatic and manual settings and corrections for repeat orders, and based on the corrections modifies the control parameters in the weighting computer (16), subject computer (20) and matrix correction computer (17).
8. Process according to one of the preceding claims 1 to 7, characterised in that the scanners (5, 6) are dimensioned so that they detect a scanning surface or a scanning screen (7) of 2 mm x 2.5 mm and in that the width of an ink zone (10, 11) is between 20 and 60 mm, several scanners (e.g. 6) being arranged next to each other.
9. Process according to one of the preceding claims 1 to 8, characterised in that instead of the values ascertained by the scanners (5, 6) for determining the surface cover, data (pixels) are taken from an image memory (19) and, after compressing to scanning screen size, are used, e.g. for the correction of the presetting and control values.
10. Process according to one of the preceding claims 1 to 9, characterised in that the presetting and control data determined by the weighting computer (16) are visualised.

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