EP0505323B2 - Method of adjusting the screendot sizes of a rotary offset printing machine - Google Patents

Description

The invention relates to a method for adjustment the dot sizes for an offset rotary press.

For many years the attitude has been tried and regulation of the essential operating parameters, especially the color setting of printing machines to improve and in particular to automate. Typical examples of the corresponding Efforts are made in GB-0S 2 165 801, DE-OS 33 14 333, DE-OS 38 06 100, DE-OS 37 35 785, DE-OS 39 29 085, DD-PS 256 292, the DD-PS 256 291, GB-OS 2 064 113, DE-PS 32 04 501, DE-OS 37 30 625 and EP-PS 61 596 forth.

In doing so, they are essentially independent of print templates Measuring and control elements used. Around influencing the color scheme as precisely as possible to enable each color setting zone of the printing press, these measuring and control elements become one Set for each inking zone and across the printing width too so-called control strips composed, the outside the printed image in the "white" border of the Printed sheet to be arranged. These control strips are either on-line, i.e. directly in the current Printing press, or off-line on the Substrate scanned, i.e., printing samples are checked outside the press, so then appropriate adjustments are made can.

The use of template-independent However, measuring and control elements have the disadvantage that there is no direct relation to those sensitive to tolerance Image areas of the print template created can be. As a result, there are more control elements per printed page to use than actually required would be, and there are no templates specific to these elements Setpoints. It also requires Handling of measuring and control elements is not insignificant effort for printing form production.

There are several ways to address these shortcomings Suggestions have been made to determine the quality Factors, especially dot size and solid color density, without specific control strips to be determined directly from the printed image.

EP-OS 0 136 542 is concerned with a method to determine the solid color density and the dot gain on two three-color halftone elements using densitometric measurements, calculation formulas and calibration curves. This process is very complex and in practice only with an extremely large one Realizing effort.

Furthermore, a method is known from DE-OS 39 25 011 to monitor the print quality multi-colored Print templates of an offset printing machine, at with the help of a camera with color-selective sensor fields Color separation images of the image segment to be checked in the spectral ranges red, green and blue generated and this by means of image analysis methods in an image processing system are processed so that the color layer thickness via a gray value measurement the color grid points of the individual primary colors are determined can be. This procedure is based on the Desired mean color dot density in the measuring segment but does not take into account the Perception of the human eye allowable tolerances.

DE-OS 28 29 341 deals with data acquisition for color control systems, using a hand-held densitometer is connected to a color control system. For Simplification of operation is user guidance by a display device coupled to the densitometer intended. With the hand densitometer can be printed on a sheet in freely selectable image zones be measured, which are adapted to the subject; there the measuring points can be in the image area, there is no need for the color control strips mentioned above. However, it is not described like this Image zones and their associated target values are determined become.

From DE-OS 2 728 738 it is known to print sheets for samples regarding the quality determining Drawing process parameters, measurements carry out and according to the usual techniques of Control and regulation technology Interventions based on the results found.

Furthermore, a method is known from US Pat. No. 4,468,692 to vary the colors of an image with the density signals for the colors cyan, magenta, yellow and black from an original be removed, fed to the color display become. Color signals for cyan, magenta and yellow become using table memories in color separation density signals converted for red, green and blue; then the converted color separation density signals added individually.

Then add the color separation density signals Correction values for printing the colors added one above the other from a second table memory depending on the color signals be won. A correction value for black printing on the other colors from a third Table memory can be read out to the so received signals are added.

Furthermore, DE-OS 33 19 941 shows a method to display a replica of a multicolor print Color image on a screen where data, which are determined for the production of a colored print, retrieved from a storage device and for everyone Printing inks are added selectively, namely to Generation of a density signal that after its processing a color picture tube for displaying the multicolor print controls color image controls.

U.S. Patent 4,414,636 shows a color control simulator, a variation with the help of table memories made of different color signals can be.

From US-PS 4,843,379 is a monitor for the Playback of color images known, in which means of a given algorithm the saturation of the image colors is influenced while the hue and the color intensity remain unaffected.

Japanese Patent Application 1-131568, published in Patents Abstract of Japan P-922 August 22, 1989, vol. 13 / no. 377, shows a pressure simulator, at the signals for the yellow, magenta and black Color processed and stored digitally. The Output signals of the memories are switched so that the read signals are each half in horizontal and vertical lines. Therefore can, for example, two images of two Save displayed at the same time and on the screen of the color monitor can be compared.

In addition, attempts have already been made to determine the permissible Analyze tolerance depending on the print template and fix. The DE-OS describes this 35 43 444 a process in which on within the color zones printed measuring fields repeated halftone dot sizes, if necessary also solid color densities, be determined and when they fall out tolerance ranges assigned to them by actuation of actuators correcting in the printing process is intervened. Every print job with the help of a catalog of typical test pictures and Color charts classified in an image contrast class. Because of the classification in this class can then tolerance to be observed. The corresponding Target values relate to the image-independent standardized control elements for full and Grid densities. However, this method has the following Disadvantages: For each print template, a must first Test image can be searched and found; if yourself based on this test picture shows that the tolerance range for the intended printing process is tight, the estimate becomes difficult like the print template when "pushing" the printing process-related Tolerances responded when the limit values of the tolerance range can be reached; Moreover this method does not take into account the different Colored structures of the color separations; and finally it becomes very expensive when the artwork is in Regarding different image zone sensitivities must be classified.

A further development of this process is in DE-OS 36 04 222 described, after which in selected Color zones measuring fields in the form of combination measuring fields be formed; to this end become single color measuring fields of at least two different printing colors printed on top of each other, by the number of measuring elements per color zone in the To be able to reduce control strips. From those in these Combination measuring fields determined measured values are corrected values for the solid densities and / or Grid point sizes won. The inclusion of the permissible tolerance range and the previous check the effects of fluctuations in the Operating parameters in this tolerance range visual way is not possible.

The invention has for its object a method for setting the grid point sizes for a To create offset rotary printing press where the disadvantages mentioned above do not occur. In particular to propose a procedure that systematic deviations in color rendering avoids.

According to a first aspect, this task in a method for setting the screen dot sizes for an offset rotary printing press solved the features of claim 1.

This solution aspect is based on the following considerations: When presetting and controlling the Color / water balance of an offset rotary printing press can systematic deviations the actual values of the quality-determining operating parameters occur. As a particularly essential Size the grid point size turned out to be which make a crucial contribution to the illustration supplies.

For the appropriate setting of an offset rotary printing press become standards for the newspaper printing process, e.g. according to UGRA 73/11, specified, after which, for example, a printing form is produced becomes. An essential parameter of this standard provides also represents the screen dot size.

According to the usual procedures, the printing form manufactured in accordance with these standards, which then causes deviations in the current pressure result in the so-called "pressure characteristics". These consist of the differences between the Process pressure characteristic means according to the standard and the current printing characteristics per inking unit, i.e. statements about the actual pressure and the occurring systematic deviations from the Norm values, especially with the dot gain.

As long as in the work area of the "prepress" current actual mean values for the pressure characteristics per Inking units are not known, the color separations must and the page break with the given characteristic mean values the newspaper printing process, for example according to UGRA 73/11.

One asks now just before the printing form is made the current average actual values via the occupancy plan the dot sizes for each Ink units, so the differences between the target values and the actual values of the screen dot size still taken into account in the production of the printing form become. This procedure can be used to shift tone values Differences between the individual colors even before the offset rotary printing press starts up restrict. Doing so provided, of course, that in each case the mean color values are within the process tolerance.

In this way, systematic, machine-related deviations between target and actual values for the grid point size are recorded and can be compensated, according to a preferred Embodiment the average target values of the screen dot sizes taking into account the expected Actual changes during production and the Print template-specific dependencies of the inking units be adapted to each other.

The second aspect of the invention has in claim 2 found its precipitation.

Preferred embodiments are by the Characteristics of the subclaims defined.

These measures can cause random errors to be compensated for due to offset printing of the numerous sensitive dependencies and Variables can occur; because with offset printing the perfect print image of the color / water balance depending on the, regardless of the ink type, must always be formed anew for each printing form. There numerous confounding factors the constancy of this balance affect and cause random errors, is always a regulation with high quality requirements, be it manual or automatic.

From DE-OS 35 43 444 and DE-OS 36 04 222 it is known that fluctuations in tone values primarily as color balance deviations in the midtones be perceived. It follows that a optimal regulation not only the individual Correct colors independently, but rather the relationships between the colors should take into account. Since also the sensations on the deviations from tonal shifts depend heavily on the original image the tolerance for the individual colors and their Relationships very different, template-dependent requirements. Around Requirements in terms of regulatory procedures quickly to implement, according to the invention, a color simulation computer used on the color separations of the print template.

On the screen of this color simulation calculator can the figure to be analyzed, for example a newspaper page on theirs Deviation sensitivities are checked, by the halftone dot sizes of the color separations varies within specified tolerances become. This image influencing is expedient in the same way as on the offset rotary printing press made, namely analog to the color zones and, alternatively, with appropriate input keyboards.

In a first stage of expansion, this process purely manual and basically without coupling to the offset rotary printing press take place, in particular then when the machine already has optimal setting values for the start of production, for example due to the first aspect of the solution. At this stage would be the color simulation calculator serve only as a "behavior trainer" for the printer, to give him a feeling of how he feels when performing random deviations should behave.

For this purpose, both the target submission as well as the test image for the deviations on the screen are shown as a comparison between Images on paper and on the screen too little can be done exactly and also lighting technology cannot be carried out properly.

Since the image analysis is based on a relative Target / actual comparison, this is not necessarily a Disadvantage, especially since the screen comparison is fast and efficient implementation of numerous deviation combination options allowed.

On the other hand, if you want to do a target / actual comparison with Print target specifications for direct cross-comparison with to have the printed copy ready, this should be the case output on a suitable, high-resolution printer be a precise cross-comparison is possible under standard lighting conditions.

The corrective measures developed at this stage of expansion can advantageously with fuzzy logic working control strategies, such as "Fuzzy logic", saved and for automatic Regulation of the offset rotary printing press used become; this results in a significant relief of the printer while the work on the Offset rotary press even at the highest Quality requirements.

To further increase the accuracy here, the printer receives during production data acquisition and evaluation via a tolerance monitoring timely warning if the automated supported Settling the limits of their possibilities has reached.

For the specification of the target values for the screen dot sizes, if necessary also for the solid density the conversion software of the main simulation computer exploited the subtractive process colors cyan, magenta and yellow alternately in the additive process colors violet blue, orange-red and can implement green; this allows the print template relatively very precisely in the sense of a visual target specification display on a high resolution screen; the necessary image information about the Color separations of the three subtractive process colors and black can from the corresponding film or printing plates with the help of a scanner or through the direct transmission of the image information can be obtained from a color separation calculator.

Another problem can be pressure disorders, which is the area coverage of the raster image undesirably change. The related changes the screen dot sizes can in principle be two have different causes, namely irregularities in color flow behavior, which can vary up to one degree to the color guide actuators of the Let offset rotary press influence, and so-called "processing errors" that affect the printed image due to errors in the convergence between paper and Affect impression cylinders. This leads to deformations the grid point and thus also changes the dot size. To these two Clearly distinguish between possible errors the conventional control gauges via special Analysis elements, the so-called pushing and / or detect duplication of the halftone dots.

Since there are no control strips in the solution described here used more in the traditional sense this analysis option also disappears. For Detection of these faults can be done electronically Planimeters are used, which are the halftone dots recorded individually and with the help of an image data processor Systems defined by size and shape. Means a target / actual comparison for the essential quality parameters, namely screen dot size and possibly Solid density and dot shape, can the possible causes of the fault are separated and thus countermeasures can be initiated.

It turned out to be useful for development a color simulation simulation tablet from troubleshooting strategies to use and it with a second row of ink zone-oriented working To provide input keys. This enables the parallel Change of halftone dot sizes of two process colors or the simulation of the transfer from the target state into a disturbing change and their correction. Will these correction options stored, so the system has for typical image disturbances over a ranking of correction proposals.

To determine the metrological target values can the mechanical on the electronic planimeter Screen dot sizes due to the printing characteristics be given directly while for the Grid dot shape with a library if necessary grid-dependent patterns must become.

To determine the densitometric and / or spectrophotometric target values, but also as "Hardcopy" for the visual target specification can be done on the color simulation computer a color printer, e.g. B. after working electrophotographic process, connected become. Another alternative is in the arithmetical specification of these values. The basic setting this color printer as well as that of the screen can be parallel to the basic setting of the offset rotary printing press with the help of suitable test forms respectively.

When controlling densitometric or spectrophotometric measuring devices and / or electronic Planimeters for recording the actual values is operated according to the image control zone priority series, which are formed when the target values are specified becomes.

The measures to reduce the deviations between target and actual values are based the priorities for action when specifying the target values be determined.

The invention is described below using exemplary embodiments with reference to the enclosed schematic drawing explained in more detail single figure gives an overall view of each Components of the overall system there.

A generally in the reproduction department The provided color separation computer 1 disassembles the originals in the color separations for the four process colors cyan, magenta, yellow and black, which then transferred to the printing forms for the four process colors should be. Then with this Information and the corresponding text in the page break designed the entire page to be printed. The Color separation calculator 1 becomes synonymous with color separation and page break system understood.

The page to be printed with the four color separations is from the color separation computer 1 via a data line 11 fed to a color simulation computer 9, the further input signals from a color simulation tablet 21, via a data line 16 from a Densitometer or spectrophotometer 14, over a Data line 19 from an electronic planimeter 18, via a data line 17 from an online measurement Densitometer or spectrophotometer or / and electronic planimeter 15, via a Data line 22 from an AVOR (job preparation) computer 4, and via a data line 10 from receives a film or plate scanner 2.

The color simulation computer 9 is via a data line 30 connected to the printing form production 31.

In addition, the output signals of the color simulation calculator 9 via a data line 20 a control station 6 of the rotary printing press 8 and fed to a monitor 13 via a data line 12, which is usually located near the control center 6 located.

The film or plate scanner 2 is one Data line 3 to the AVOR (work preparation) computer 4 connected to the control center 6 a data line supplies 5 further input signals.

The control center 6 serving as rotation control controls those to be acted upon via a data line 7 Actuators (not shown) in the individual Printing units 8 of the offset rotary printing press on.

This means that all relevant system elements for the overall system is described schematically, wherein should also be mentioned that in the data line network the individual bit-serial individual connections too through a more universal BUS architecture with any Data traffic between the individual participants can be replaced.

The following is how this works Systems discussed in more detail, with the image quality determining Parameters are briefly discussed, which are decisive for process control in offset printing are. This is the color layer thickness, the quantitative with the so-called solid color density is described, on the one hand, and the screen dot size on the other hand, as a percentage of the paint layer coverage is quantified. Differences in the dot size one between mechanical, i.e. more effective, and optical dot size. The optical dot size results from a full tone and screen density measurement with the help of the so-called Murray / Davis formula, which is the optical dot size on the mechanical dot size differentiates by the value of the so-called "light catch", which is an optical light scattering phenomenon quantified. This is for the purpose described here The only difference is that the the two percentages are not confused may be.

For color dosing in offset printing now from the ink layer thickness and the area coverage all halftone dots and solid areas the corresponding within a coloring zone Color volume can be determined. Basically according to the principle of so-called normal coloring method. Then the contrast function for a certain color, a certain color formula (Color batch) and a particular paper maximized. This contrast function is defined as the percentage difference in density related to the corresponding full tone of full tone and screen tone with 3/4 film surface coverage. The contrast maximum is limited at given Materials and pressure ratios the coloring or the solid density upwards as far as at an additional color layer thickness Halftone dots, especially in three-quarter tone, for Tend to go and thus the share of paper white reduce.

Following this principle is given materials the solid density is basically defined, so that the Theoretically, the printing process can only be based on the acquisition / monitoring of area coverage and point size can be controlled. In practice, however the relationship between solid density and dot size not constant, so that the dot size during the printing process and solid tone density are monitored have to; however, the full-tone density has a relevance less important than the dot size.

A crucial attribute of these two quality-determining Features are their respective tolerances. Through decades of efforts to Standardization in offset printing through various national and international institutions are for the different areas of application of offset printing Tolerance information for the solid density and the Screen dot size has been specified. There is two problems: first, these tolerance specifications for the four process colors regardless of the Print template made, and the other must the contradictions of the narrowest possible tolerances and the associated, economically justifiable Effort can be mastered.

The first problem is known to be fluctuations the screen dot sizes and the ink layer thicknesses first as disturbances in the color balance, i.e. overprinting of the inks in the midtones, be perceived. Besides, the sensations on the deviations in the screen dot sizes strongly dependent on the original: pictures with reduce strong chromatic colors and large chromatic contrasts the sensitivity of the viewer in this regard, whereas homogeneous gray areas with extreme low-contrast viewing situations the sensitivity of the viewer significantly, so too small halftone dot size changes still perceived become. Hence the requirement that systemic tolerances depending on the Analyze and monitor print template.

For color dosing on the offset rotary printing press are now basically two different ones Ink types available, namely gap inking units controlled by ink zone and ink zoneless Short inking units. These have ink types specific advantages and disadvantages, but for the present Considerations are not relevant and consequently need not be discussed further. However, it is essential that the quality management system presented here optimally used for both ink types can be.

With the inking zone controlled controlled inking unit is the color dosage in the sense of normal coloring template specific to several Color screws in corresponding color zones and accordingly the color requirements of the artwork via the Print width set. In addition, offset printing then apply the appropriate dampening adjusted to the dampening system assigned to the inking unit become. For setting and regulating the coloring at the inking unit must therefore depend on the artwork Actuators both on the inking unit and on the dampening unit be operated.

In the short inking unit without ink zones, the ink is dosed in the sense of normal coloring using a doctored anilox roller basically independent of artwork. Color guide irregularities within the circulation cannot be influenced here in practice unless, to some extent, with Variable humidification. In the following Explanation of the system functioning is based on the Differences in zone-oriented and zoneless inking units.

With the help of the color separation calculator 1 Original originals in the reproduction department in the Color separations for the four process colors cyan, magenta, yellow and black decomposed. Each can different principles based on order and print template used for the color structure, e.g. "achromatic" or "under color reduction". After that with the so-called page break, the entire printing page designed with text and image. Recently this can be done completely computer-aided, so that the information relevant to the printing technology of the printing pages are available in digital form and about the data line 11 can be passed on. In In this sense, the computer 1 is shown schematically here representative of the color separation calculator and electronic Typesetting system.

The pages prepared for printing with the Four-color separations are then placed in the printing forms implemented (at 31). With an offset printing plate can this is done for example with the help of raster films or after a more recent development direct laser exposure of a light-sensitive plate layer with the digitized stored raster image information. This raster image information are exactly in the reproduction department Screen fineness (lines / cm), screen angulation, screen dot shape and grid point size. In the The reproduction department must determine the grid point size also for an offset printing process pre-compensate for typical dot gain. You needed the relevant press room Tolerant specifications (e.g. optical Halftone dot magnification in the midtone 30 +/- 3%)

As will be described later, the Color simulation computer 9 from the offset printing press the current actual values in the form of pressure characteristics. From these pressure characteristics one can derive systematic errors in the color simulation calculator 9 when checking the mean setpoints of the Screen dot sizes can be taken into account. The The printing form is produced in the device 31 So with mean setpoints for the screen dot sizes, which are the deviations of the updated printing characteristics per inking unit of the offset rotary printing press consider.

The color simulation computer 9 is equipped with conversion software equipped which the subtractive Process colors cyan-blue, magenta-red and yellow alternately in the additive process colors violet blue, can implement orange-red and green; thereby becomes the print template in the sense of a visual target specification on the high-resolution screen of the color simulation computer 9 reproduced.

The image information required for this conversion from the color separations of the three subtractive ones Process colors and black can be created using the Scanners 2 from the corresponding films or Printing plates entered in the color simulation computer 9 become. Another possibility is the direct transmission of the corresponding image information from the color separation calculator 1. The second solution has the advantage of quality control of the disk copy by comparing the information on the Data lines 10 from the scanner 2 and 11 from the Color separation calculator 1 is possible. This can in particular the exact functioning of the plate exposure be checked.

In addition to "subjective" quality control on the screen of the color simulation computer 9 a use objective quality control and the printing press system-related Monitor tolerances exactly to be able to, are at least one more Densitometer or spectrophotometer provided namely either as an off-line system 14 or as an on-line system 15; the corresponding signals will be the color simulation computer 9 via the data line 16 or 17 supplied as actual values for quality control.

The printed paper on the rotary press scanning on-line devices 15 work much faster and automate the quality control loop full, but have the disadvantage that they are per web side to be monitored at least one measuring head each and need a uniaxial positioning device; for machines for multi-line production the on-line devices 15 are therefore very expensive.

The following statements are limited hence on the use of off-line devices 14 which in the simplest version from a measuring table and a manually operated measuring device (densitometer or spectrophotometer) exist; a direct one Measuring point location display using, for example, a Light point is very recommendable.

A much more convenient solution for capturing of the actual value for the quality control consists in the assembly of the densimetric or spectrophotometric working measuring head on an automatic controlled cross slide. The required per picture Measuring point coordinates are directly from the software of the color simulation computer 9 specified.

Especially when there are increased requirements another recording device should be placed used for the actual values of quality control are, namely an electronic planimeter 18; this The device can have the appropriate optics Halftone dots of the individual process colors in the finished Feel the pressure and describe its size and shape. The relevant information will be also the color simulation computer 9 for the target / actual comparison fed. A particularly noteworthy The possibility that arises with this device is Monitoring and, if necessary, correcting the so-called color register or color register. This is the positional accuracy of the one above the other printed color separations to each other and on the Sheet meant.

An advantageous embodiment of the devices 14 and 18 also consists of a combination of the corresponding Measuring heads on only one cross slide unit.

Based on a deviation sensitivity analysis the quality-determining characteristics, in particular the dot size, from the artwork with the help of the color simulation computer 9, your critical image areas with appropriate color compositions examined. This then forms the Basis for the control and regulation strategy at Printing process. Has the quality management system in a simple expansion stage does not yet have the measuring devices 14 and / or 18, the monitoring takes place "Subjectively" via the target specification on the monitor 13. For the Metrologically and automatically supported regulation can, however, due to the deviation analysis Targeted setpoints either in the printed image or in one Digital wedge adapted to the template become. In special cases, of course, is a combined one These techniques can be used. The Digital wedge consists of precisely defined control elements, especially for the dot size and Full tone density, and can be digital in one Computer system can be saved. At the film or This digital wedge is then also used for direct plate exposure transmitted to the printing form. It can be Elements can be part of the picture or outside the actual printed image on the white edge of the image be applied. In the procedure described here can this digital wedge in terms of composition, Design and arrangement of its Control elements in an optimal way to the print template on the one hand and on the color metering technology on the other adapted and from the color simulation computer 9 on the film or platesetter 31 are transmitted.

A particular problem in quality management is the collective production of double cut machines. There are two different types of production Printing forms one after the other on the same cylinder, so that the same color guide actuators in their corresponding zones on printing forms from templates interact with different requirements. This Problem can be dealt with effectively, that both templates on the monitor of the Color simulation calculator 9 simultaneously on their tolerance sensitivity examined and accordingly optimal target values and control elements are defined become.

1. Nach dem Prinzip der erwähnten Normaleinfärbung werden die Druckkennlinien und die Farbwerkgrundeinstellungen ermittelt. Dabei werden die auftretenden Streuungen für die Reproduktionsabteilung ausgemittelt. Die Toleranzbandbreite der Druckkennlinie setzt sich zusammen aus systematisch und zufällig bedingten Abweichungen. Es wird nun grundsätzlich angestrebt, die systematischen Abweichungen durch Nachführen der Maschinengrund- und Voreinstellungen zu reduzieren und die zufälligen Abweichungen nach Möglichkeit im Druckprozeß auszuregeln.

2. Die am Farbauszugs-Rechner 1 ermittelten Farbauszüge werden dem Farbsimulations-Rechner 9 übermittelt. Dieser analysiert die Abweichungsempfindlichkeit der Druckvorlage durch gezielte Größenvariation der bildbeschreibenden Qualitätsmerkmale, insbesondere der Rasterpunktgröße. Aufgrund dieser Untersuchung werden Kontrollelemente und entsprechende Sollwerte festgelegt. Danach werden die Rasterpunktgrößen und die Anzahl Rasterpunkte über die Drucklänge des Druckzylinderumfanges zu Flächendeckungssummen aufintegriert und diese Daten dann dem AVOR-Rechner 4 eingegeben, der unter anderem die sogenannten Maschinenbelegungsprogramme verwaltet; diese geben Auskunft über die Lage der Druckform in der Offset-Rotationsmaschine, wodurch die Zuordnung der entsprechenden Flächendeckungssumme zu einer spezifischen Einheit der Druckmaschine 9 und dem dazugehörigen Farb- und Feuchtwert möglich werden. Diese Informationen werden über die Datenleitung 5 zur Steuerung der Offset-Rotationsmaschine 8 gegeben, die schematisch nur als Leitstand 6 dargestellt ist. Die Maschinensteuerung rechnet mit Hilfe von Eichkurven die Flächendeckungssummen um. Diese Informationen werden über die Datenleitung 7 auf die entsprechenden Stellglieder der Offset-Rotationsmaschine 8 gegeben. Nebst den Farbwerken werden hernach auch die Feuchtwerke voreingestellt. Zur Eichkurvenermittlung wird das bereits erwähnte Prinzip der Normaleinfärbung angewendet. Beim farbzonenlos arbeitenden Farbwerk wird für die Ermittlung der Kontrollelemente und Soll-Werte grundsätzlich gleich verfahren, hingegen entfällt der Voreinstellvorgang für die Farbschrauben. Hier können lediglich Stellgrößen für die Feuchtwerke übermittelt werden.

3. Im Auflagendruck werden nun die Qualitätsmerkmale gemäß den vorstehenden Bildkontrollzonen und/oder Kontrollelementen mit den entsprechenden Sollwerten überwacht. Bei unzulässigen Abweichungen werden entweder automatisch Korrekturen ausgeführt oder entsprechende Vorgaben dem Drucker übermittelt. Dieser veranlaßt sodann die vorgegebenen Korrekturen am Leitstand 6 durch Eingabe entsprechender Soll-Werte für die Stellglieder. Führt die quantifizierte Empfehlung nicht zum Ziel, wird der Drucker diese übersteuern oder aber andere Maßnahmen ergreifen.

4. Bei Produktionsende werden die vorgegebenen und effektiven Einstelldaten miteinander verglichen, abgespeichert und periodisch ausgewertet. Ergeben sich jetzt Abweichungen der Flächendeckungssummenvorgabe mit den entsprechenden effektiven Einstellwerten an der Rotation und treten bei Folgeproduktionen die gleichen manuellen Korrekturen im Sinne von systematischen Abweichungen am Anfang oder im Verlauf der Produktion auf, so kann die Steuerung dem Drucker eine Empfehlung zur Anpassung der Eichkurve geben oder dies im Sinne eines Selbstlernprogrammes selbst vornehmen, wobei mit zugehörigen Kontrollelementen der Kontrast und die entsprechend optimale Volltondichte überprüft werden muß. Mit dieser Vorgehensweise kann sichergestellt werden, daß die Bandbreite der systematischen Abweichungen sukzessive besser eingegrenzt werden kann.Bei den zonenlosen Kurzfarbwerken treten ebenfalls systembedingte Abweichungen auf, und zwar beispielsweie durch andere Farbchargen oder den Rakel- und Rasterwalzen-Verschleiß. Um diese Abweichungen möglichst in ihren Auswirkungen zu beherrschen, empfiehlt es sich, ebenfalls die druckvorlagenabhängige Toleranzanalyse am Farbsimulations-Rechner 9 mit der Festlegung entsprechender Kontrollelemente und Sollwerte durchzuführen. Werden nun die Überwachungsergebnisse nach der Produktion systematisch ausgewertet und verwaltet, zum Beispiel mit dem AVOR-Rechner 4, so können diese Daten sukzessive bei der Bildtoleranzanalyse mitberücksichtigt werden, indem sie über die Datenleitung 22 in den Farbsimulations-Rechner 9 übernommen werden. Werden hierbei jetzt störende Abweichungen festgestellt, die auf diesen Farbwerken kurz vor Produktionsbeginn nicht mehr korrigiert werden können, so müssen gezielte Rasterpunktgrößenkorrekturen vom Farbimulations-Rechner 9 an den Plattenbelichter 31 weitergeleitet werden. Dies bedingt natürlich einen fortgeschrittenen Qualitätsleitsystemausbau, bei dem die Vorlagenanalyse im Zusammenhang mit den systematischen Farbwerkabweichungen vor der Plattenbelichtung ausgeführt werden kann.Zur Verbesserung des Regelungsverhaltens bei farbzonenorientiert arbeitenden Farbwerken zur Verringerung der Bandbreite der zufälligen Abweichungen können am Schluß der Produktion die Veränderungen der Flächendeckungssummenvorgabe und der Einstellwerte abgespeichert und analysiert werden, um daraus Regelungsvorgaben abzuleiten, wie zum Beispiel, daß Rasterpunktgrößenkorrekturen nach oben einfacher zu realisieren sind als nach unten oder/und, daß zweite, dritte und vierte Farben im Übereinanderdruck aufgrund des Farbannahmeverhaltens schwieriger einzustellen sind. Diese Regeln können nun im Farbsimulations-Rechner 9 aufgrund der laufenden Produktionsauswertungen zur sukzessiv optimalisierten Automation gebildet und verwaltet werden.Bei den zonenlos arbeitenden Kurzfarbwerken können ebenfalls zufällige Abweichungen auftreten, und zwar beispielsweise bedingt durch das Raumklima und/oder das druckformbeeinflußte Farb/Wasser-Gleichgewicht. Zur Korrektur solcher Einflüsse ist man bei diesen Farbwerken nachteilig eingeschränkt. Immerhin bestehen aber Möglichkeiten, über die Farbtemperierung oder die gezielte Veränderung der Feuchtung gewisse Korrekturen in der Produktion vorzunehmen. Damit können auch bei zonenlosen Kurzfarbwerken mit dem hier beschriebenen Qualitätsleitsystem zweckmäßige Regelstrategien entwickelt werden.

5. Die in dem vorstehenden Abschnitt erörterten maschinenorientierten Verstellungsregeln können nun am Farbsimulations-Rechner 9 mit den druckvorlagenabhängigen Soll-Werten und ihren Abhängigkeiten untereinander zu produktionsspezifischen Regelungsstrategien kombiniert werden. Zur Entwicklungserleichterung dieser Regelungsstrategien ist beim Farbsimulations-Rechner 9 das Farbsimulations-Tablett 21 vorgesehen, das beispielsweise die zonenweise Veränderung der Punktgrößen im Farbsimulationsrechner 9 in genau gleicher Weise simuliert wie die Farbschraubenverstellung am Leitstand 6 der Offset-Rotationsmaschine 8. Zweckmäßigerweise wird dieses Simulationstablett mit einer zweiten Reihe von farbstellzonenorientiert arbeitenden Eingabetasten versehen. Dies ermöglicht die parallele Veränderung von Rasterpunktgrößen zweier Verfahrensfarben oder die Simulation des Überführens vom Soll-Zustand in eine störende Veränderung und deren Korrektur auf unterschiedlichen Wegen. Durch Abspeichern dieser Korrekturmöglichkeiten verfügt das System für typische Bildstörungen über eine Rangreihe von Korrekturstrategien.

6. Für besonders heikle und wiederkehrende Farbtöne wie Haut-, Möbel- oder gewisse Modefarben kann mit Hilfe des produktionsspezifischen Regelungssystems aus verschiedenen Farbzusammensetzungsvarianten die optimale in Bezug auf die Wiedergabetreue und Abweichungsstabilität erarbeitet und beim wiederholten Bedarf abgerufen werden.

In order to further discuss the flow of information and the various possible uses of the quality control system shown here, the individual procedural steps are now summarized schematically below, with special attention to the data feedback for monitoring and self-adaptation of the system.

1. The printing characteristics and the inking unit basic settings are determined according to the principle of the normal inking mentioned. The scatter that occurs is averaged out for the reproduction department. The tolerance range of the pressure characteristic curve is made up of systematic and random variations. The basic aim now is to reduce the systematic deviations by updating the basic machine and default settings and to compensate for the random deviations in the printing process if possible.

2. The color separations determined on the color separation computer 1 are transmitted to the color simulation computer 9. This analyzes the sensitivity to deviation of the print original by specifically varying the size of the image-describing quality features, in particular the screen dot size. Control elements and corresponding target values are determined on the basis of this examination. Then the screen dot sizes and the number of screen dots over the printing length of the printing cylinder circumference are integrated into area coverage amounts and this data is then input to the AVOR computer 4, which among other things manages the so-called machine occupancy programs; these provide information about the position of the printing form in the offset rotary machine, which makes it possible to assign the corresponding area coverage to a specific unit of the printing machine 9 and the associated color and moisture value. This information is provided via the data line 5 for controlling the offset rotary machine 8, which is shown schematically only as a control station 6. The machine control uses the calibration curves to convert the area coverage. This information is given via the data line 7 to the corresponding actuators of the offset rotary machine 8. In addition to the inking units, the dampening units are then preset. The principle of normal coloring mentioned above is used to determine the calibration curve. In the inking unit that works without ink zones, the procedure for determining the control elements and target values is basically the same, but the presetting process for the ink screws is omitted. Only control values for the dampening units can be transmitted here.

3. In the print run, the quality features are now monitored in accordance with the above image control zones and / or control elements with the corresponding target values. In the event of impermissible deviations, corrections are either carried out automatically or corresponding specifications are sent to the printer. This then initiates the predefined corrections at the control center 6 by entering corresponding target values for the actuators. If the quantified recommendation does not lead to the goal, the printer will override it or take other measures.

4. At the end of production, the specified and effective setting data are compared with one another, stored and periodically evaluated. If there are deviations in the area coverage total specification with the corresponding effective setting values on the rotation and if the same manual corrections occur in subsequent productions in the sense of systematic deviations at the beginning or in the course of production, the controller can give the printer a recommendation to adjust the calibration curve or do this yourself in the sense of a self-learning program, the contrast and the corresponding optimal solid density must be checked with the associated control elements. This procedure can be used to ensure that the range of systematic deviations can gradually be better limited. System-related deviations also occur in the zone-less short inking units, for example due to other ink batches or the wear of doctor blades and anilox rollers. In order to control the effects of these deviations as far as possible, it is advisable to also carry out the tolerance analysis on the color simulation computer 9 with the specification of corresponding control elements and target values. If the monitoring results are now systematically evaluated and managed after production, for example using the AVOR computer 4, this data can be taken into account successively in the image tolerance analysis by being transferred to the color simulation computer 9 via the data line 22. If disturbing deviations are now found here, which can no longer be corrected on these inking units shortly before the start of production, then corrected dot size corrections must be forwarded from the color simulation computer 9 to the platesetter 31. Of course, this requires an advanced quality control system development, in which the template analysis can be carried out in connection with the systematic inking unit deviations before the plate exposure. To improve the control behavior with inking zone-oriented inking units to reduce the range of random deviations, the changes in the area coverage specification and the change can be made at the end of production Setting values are stored and analyzed in order to derive control specifications from them, for example that screen dot size corrections upwards are easier to implement than downwards and / or that second, third and fourth colors in the overprinting are more difficult to set due to the ink acceptance behavior. These rules can now be formed and managed in the color simulation computer 9 based on the ongoing production evaluations for successively optimized automation. Random deviations can also occur in the zone-less short inking units, for example due to the room climate and / or the ink / water balance influenced by the printing form . In order to correct such influences, these inking units are disadvantageously restricted. At least there are possibilities to make certain corrections in the production via the color temperature control or the targeted change of the dampening. Appropriate control strategies can be developed with the quality control system described here, even for zoneless short inking units.

5. The machine-oriented adjustment rules discussed in the previous section can now be combined on the color simulation computer 9 with the template values dependent on the template and their interdependencies to produce production-specific control strategies. To facilitate the development of these control strategies, the color simulation tablet 21 is provided in the color simulation computer 9, which, for example, simulates the zone-by-dot change in the color simulation computer 9 in exactly the same way as the color screw adjustment on the control station 6 of the offset rotary machine 8. This simulation tablet is expediently equipped with a the second row of input keys that work in a color-specific zone. This enables the parallel change of halftone dot sizes of two process colors or the simulation of the conversion from the target state into a disturbing change and its correction in different ways. By storing these correction options, the system has a ranked series of correction strategies for typical image disturbances.

6. For particularly delicate and recurring color tones such as skin, furniture or certain fashion colors, the production-specific control system can be used to work out the optimal color and variation stability from various color composition variants and to call them up when required repeatedly.

Claims (11)

1. A method for setting the half-tone dot sizes for a rotary offset printing machine having the following features:

   a) the current printing characteristics of the rotary offset printing machine for each inking system with given materials are detected at maximum printing contrast prior to the production of the printing formes;

   b) pre-set standard desired values pre-compensating the dot growth for the half-tone dot sizes of the printing forme are compared with the corresponding values of the detected current printing characteristics; and

   c) in the making of the printing forme, in the event of deviations between the standard desired values and the corresponding values of the detected current printing characteristics, desired average values compensated in accordance with these deviations are used instead of the standard desired average values for the half-tone dot sizes of the printing forme, so that systematic deviations in the required colour reproduction are avoided.
2. A method for setting the half-tone dot sizes for a rotary offset printing machine having the following features:

   a) the current printing characteristics of the rotary offset printing machine for each inking system with given materials are detected at maximum printing contrast and calibration curves are determined therefrom;

   b) desired average colour separation values for the half-tone dot sizes of the individual colour separations of an original are determined and

   c) converted via the calibration curves into desired setting values for the printing units of the rotary offset printing machine;

   d) the rotary offset printing machine is feedback-controlled in accordance with the desired setting values;

   e) the effective setting values resulting during the production are compared with the desired setting values and

   f) in the event of deviation of the effective setting values from the desired setting values, the calibration curve is adapted, so that systematic deviations and random deviations in the printing are avoided.
3. A method according to one of Claims 1 and 2, characterised in that the current printing characteristics are detected a plurality of times and corresponding average values are formed from the results.
4. A method according to one of Claims 2 and 3, characterised in that the deviations of the effective setting values of the inking systems during the print run from the desired setting values are compared with one another, stored, periodically evaluated and used to adapt the calibration curve.
5. A method according to one of Claims 1 to 4, characterised

   in that the colour separations of the original are displayed on a screen of a colour simulation computer (9),

   in that the half-tone dot sizes of the colour separations on the screen are varied by specific size change and

   in that the desired colour separation average values for the half-tone dot sizes of the individual colour separations of the original are determined on the basis of these variations.
6. A method according to one of Claims 2 to 5, characterised in that the colour separations are determined on a colour separation computer (1) and transmitted to the colour simulation computer (9).
7. A method according to one of Claims 2 to 5, characterised in that image information for the representation of the colour separations is determined by means of a film or printing-forme scanner (2) and fed to the colour simulation computer (9).
8. A method according to one of Claims 1 to 7, characterised in that, for the determination of the current printing characteristic at maximum printing contrast, printed sheets are measured by means of densitometer or spectrophotometer (14, 15) and the measured values are fed to the colour simulation computer (9).
9. A method according to one of Claims 1 to 8, characterised in that shape and size of the half-tone dots on the printed sheet are scanned by means of an electronic planimeter (18) and fed to the colour simulation computer (9).
10. A method according to one of Claims 2 to 9, characterised in that, for the adjustment of the desired setting values, the ink screw position and/or the damping system setting on the rotary offset printing machine is/are adjusted.
11. A method according to one of Claims 2 to 10, characterised in that the desired setting values are adjusted automatically using control strategies which operate according to inexact logic, such as fuzzy logic.

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