EP0639456B1 - Method and system of communication for computer aided printing - Google Patents

Description

The invention relates to a communication method and system with a computer-controlled data transmission for controlling the printing process of a printing press.

The further development of printing press technology is less and less the way to optimize the mechanical and electronic components separately, but increasingly the way to improve the interaction between the two areas. So far, the printing press electronics can be described in good approximation as self-contained, i.e. Although the machine receives printing plates, paper, ink and other consumables, it does not receive any electronically available information and produces a printed product with practically no direct data communication with the environment. The electronics are limited to a supporting role of the mechanical components of the printing press. So trying, e.g. achieve an increase in quality, shorter run lengths or less waste by using more sensors and more intelligent electronics. However, this generally means an increase in complexity and thus an increase in the cost of the entire machine.

More recent considerations assume that the preparation of the printed image information (in the form of printing plates) for the printing press is carried out in an optimized process in a process called prepress. This process is naturally dependent on obtaining data about how the information is later handled in the printing press, so that, in order to achieve good results, it can counteract the press-specific change in the information there. Of course, this requires communication between these sub-processes.

The exchange of this data is usually achieved via so-called edition standards, which specify a range within which a printing press changes the image data to be printed when using certain color and paper classes (e.g. edition standard offset newspaper, offset illustration printing or sheetfed offset on coated paper). The pre-press and the press must adhere to this range. Exceptions are special in-house standards that, especially in packaging printing, define other, more specific transmission characteristics. However, these more specific characteristics can of course only apply within the very limited scope of the house that defines them; universality or type-neutral data acquisition is not possible.

In order to increase the print quality in the sense of a better agreement with the specification and more constant print results, it makes sense to include information about the product to be printed in the control. Today, this information is used practically exclusively by the printer operating the machine or by special sensors, such as an electronic plate scanner provided.

The product information is available in the prepress stage, in many respects it is even much better or more precise than the printer can provide on the press, but is usually lost when it is output to the print image carrier. However, the press control could work better with the respective product information from the prepress, if it only requested and received it.

Considerations in this direction can already be found, for example, in patent specification DE 35 27 500 C2, which proposes a new method and a device for presetting ink zones in offset. The ink zones are usually set according to the ink consumption in accordance with the assigned print areas. The first approximation is the ink consumption with the documented, ie printing The area of the printing form is identical. This area coverage can be measured on the finished printing plate using a so-called plate scanner. If the imposition scheme, ie the scheme for assembling individual pages into a printing form, is known, it is also possible to calculate the area coverage from the prepress data. Since the calculation is based on the original data, the measurement error of the plate scanner has been eliminated and the accuracy of the values for the color zone setting has been increased. The calculated data must be reported to the press electronics for presetting.

However, there is still a problem in that the preliminary stage must know specific parameters of the respective printing press type, since for example even the zones differ from type to type. Furthermore, a final calculation of the color slider setting is impossible, because on the one hand the lateral rubbing, which differs depending on the machine setting, is not taken into account and, on the other hand, the preliminary stage does not know the transfer characteristic of the values of the area coverage to values of the color slider settings.

Furthermore, it makes sense to also obtain information for the printing press control in general from the data that are available in the prepress stage. In this regard, the European patent application EP 0 495 563 A2, which reveals the features of the preamble of claims 1 and 12, proposes to use an integrated computer-controlled system for controlling several stages of a printing process, in which the information to be applied to the printing plate is available digitally (digital preliminary stage) and which generates from this layout information, for example, presetting data (ink guide) for the printing press and setpoints for the ink guide, in particular in order to achieve an intended printing characteristic. This means that data exchange should be organized from the prepress stage.

However, the entire process can only be related to a specific printing press, so everyone has to process the data specific machine data. This means that a special adjustment of the preliminary stage must be made for every other printing press.

Proceeding from this, it is the object of the invention to optimize a communication method and an associated device for carrying out the method, with which communication between different sub-areas of the printing process, in particular between the pre-press and the printing press, in such a way that the areas of the printing machine which operate independently of the printing press No special adjustment must be made to the printing process when using different printing presses, and that the printing press can receive data for presetting and process control without having to know the type of the independently operating area.

This object is achieved according to the invention by a method with the features of claim 1 and by a system with the features of claim 15.

That means e.g. for the pre-press that the press provides an interface structure for it, into which the data collected by it can be filled on the one hand and via which on the other hand the data output of the pre-press, e.g. on film or disc. The press as a whole behaves like a very complex data set that can run in both directions (prepress press, press prepress). In the computer-to-press application, in which the image data is only materialized in the printing press, the complete image information can be present as a device-independent data record.

However, the communication structure is not limited to pre-press and press, but is applied to various areas of the printing process that can operate independently of the press.

A possible embodiment of the invention is described below with reference to the drawing.

Fig. 1

eine erfindungsgemäße Kommunikationsstruktur,

Fig. 2

eine Kompensation des Farbabfalls eines Bogenoffsetdruckwerks über den Zylinderumfang,

Fig. 3

die Kompensation des Schablonierens über errechnete Kompensationskennlinien,

Fig. 4

eine Art von Kontrollelementen zur Kontrolle des Datenaustauschs zwischen der Druckvorstufe und der Druckmaschine

It shows a schematic representation

Fig. 1

a communication structure according to the invention,

Fig. 2

compensation of the ink drop of a sheetfed offset printing unit over the cylinder circumference,

Fig. 3

compensation of stenciling using calculated compensation characteristics,

Fig. 4

a kind of control elements to control the data exchange between the prepress and the press

1 shows how a plurality of printing units 1, 2, 3 are networked to form a printing press for the purpose of joint job preparation by means of a central main data processing station 4. Each printing unit 1, 2, 3 has an electrical control unit 20, 21, 22. A decentralized data processing sub-station 5, 6 per area of the printing process is in turn connected to this station 4, the connections 7, 8 between the sub-stations 5, 6 and the station 4 being established by means of machine-independent interfaces which permit data exchange in both directions. In the present case, a data processing substation (5) for the prepress and a data processing substation 6 for a production planning system (PPS) are provided to provide order data.

The central station 4 contains the technical order preparation for all of the printing units 1, 2, 3 connected to it. The technical parameters of the order, such as color assignment, formats or paper thickness, are entered there, provided they have not already been collected in advance (prepress, PPS). Furthermore a database system is set up in station 4, with which the orders and machine characteristics are managed. The operating data of the individual machines 1, 2, 3, their transfer characteristics and the control dynamics are also registered and statistically processed there.

A PECOM interface from MAN Roland Druckmaschinen AG is provided for the PPS interface 8. This interface 8 establishes the connection between industry software and the station 4. This enables data communication. This results in a quick provision of current data for production from the branch software or of data from production for the branch software. The order data already collected in advance can be fed into the machine 1, 2 or 3 via this interface 8 and assigned to the respective order. The PPS in turn can call up operating data for the individual machines 1, 2 or 3, the current print status and the status of an order. The PPS thus receives the basic data for the calculation, production planning or cost accounting.

Another type of exchange of operational data for PPS communication is the procedural optimization of imposition. If a product is based on a specific imposition scheme, the number of colors on one side is determined by the production options of the machine, in particular the folder. Even when planning a product using electronic tools, the production options must be taken into account. The printing press can report such a production profile to the planning, or the planning can have the possibility of production confirmed by the press. This can be done interactively with the planning program.

Furthermore, the information available in this way can be used to work towards optimal production conditions in the area of product planning. To clarify this, a special problem in offset is addressed. in the Pages lying one behind the other can only be corrected if a compromise strategy is taken into account, since the relevant color sliders work on several subjects at the same time. If the subjects involved have clearly different color shifts, for example one is blue-dominated, the other is strongly red-oriented, it is very difficult to achieve a satisfactory coloring. One way to avoid this problem is to use the characteristic curve communication or to check in the planning whether such a conflict occurs with the imposition scheme provided. If so, this case can be avoided by changing the imposition scheme, ie the production configuration machine and thereby changing the pages or by deliberately changing the product. In the worst case, in which these changes are not possible, the printer is at least made aware of this critical subject combination, so that he can pay special attention to it.

In technical work preparation, settings are made for paper thickness, machine couplings, turning devices, Finnishing or powder devices, color, cut and fold registers or ink zone slides. The paper type is queried by the PPS and the paper thickness can then be calculated and set from the paper used. Cutting and folding registers as well as the necessary machine configuration for the current order are derived from the imposition scheme, which is also requested by the PPS.

Two formats appear to be particularly suitable for the interface 7, which exchanges data with the prepress stage. On the one hand a subset of SGML, on the other hand a structure based on the TIFF format. SGML (Standard General Markup Language) is used in particular in the area of electronic data exchange between computers of different companies for business processes and in the area of technical manuals for purely electronic documentation. TIFF (Tagged Image File Format) is a general format for the exchange of image data, which is located in the DTP area, but has now also found its way into professional image processing Has. Both formats have in common that information can be exchanged relatively freely via the definition of brands or tags. In the exemplary embodiment, the TIFF format is preferred.

For example, to generate the preset data, the pages are put together in prepress and the images and text segments are placed. Together with the information about the placement of the pages on the printing plate or the printing cylinder, a rough grid of the plate is generated, e.g. in squares from 2.5 mm to 2.5 mm. This coarse grid is entered as a tag in the exchange file in TIF format, possibly pre-treated with TIFF-inherent compression methods analogous to a pixel image to reduce the amount of data. The order number, customer name and other organizational order data are also given as tags. This information serves as a reference for the job assignment beyond the file name. Furthermore instructions are given from the reproduction, the creative prepress or the customer. For example, the statement that the product XY to be advertised is reproduced in a particularly natural way or in a very specific way in a certain image. In the simplest case, this information is passed on to the printer operating the machine or e.g. incorporated into the weighting of the control fields to determine a control strategy.

If the printing process is controlled by machine, control elements (color measuring fields for color control and various marks for controlling the various registers) are required, as already mentioned above. These elements can be printed for this purpose or they can be specific areas of the subject. The information about these control elements can be obtained from the preliminary stage. In electronic imposition, the specific measuring elements are placed so that the location and location are known. This information is passed on to the printing press. For the measurement in the subject, each page is evaluated in the prepress on a list of typical image parts and the type of control element, the position coordinates and the sizes and tolerances to be measured to the Machine reported. Examples of suitable measuring fields are places with negative writing for regulating the register and in the offset halftone areas in one color or in the overprinting of several colors, whose tonal values remain within a predetermined minimum area within predetermined tolerances.

The preferred control element is therefore a search pattern in the form of suitable fields in the subject, the fields found being forwarded to the printing press as a data record. This creates a pedant for the conventional electronic control wedge that does not belong to the subject. In particular, the parts that are e.g. are critical to print.

The printing press 1, 2 or 3 can not only receive control field information in the sense of the invention, it can also register demand. This means that the pre-press is informed which control devices a specific press 1, 2 or 3 has and which control elements should therefore be placed on the plate. The equipment of the printing form with control fields can be adjusted automatically.

A special kind of control fields are register marks, which are used to set the exact overprint. Usually, crosses or similar geometric figures are placed outside the subject on each color separation. The hiring then has the aim of bringing them to cover or to a specified position. Using control field communication, one or more register marks can now be integrated in the subject at a convenient location. The exact position and geometry is then reported to the register measuring and control system of the printing press. Register marks can be negative text or multicolored edges in an image report or multicolored printed positive text. Furthermore, any type of positive printed text (letters with printing ink on paper white) can be converted into a register mark. For this purpose, selected text elements are used in prepress instead of one Original color made up of several colors. The different color separations must then be made to coincide in the machine for regulating the register. If this happens, the viewer will not notice any difference to the normal text. A subject 10 with two images and black text is assumed as an exemplary embodiment (FIG. 4). In the upper left area the "x" is selected from the word "text" and in this case it is made up of all four color separations cyan, magenta, yellow and black. In the lower right area, the "T" is selected from the word text and constructed from cyan, magenta and yellow. In a particularly advantageous manner, particularly inconspicuous text elements such as periods, colons, semicolons, hyphens, hyphens or the like are used. Any combination of color separations is conceivable for the text elements used, which do not result in too great a color deviation from the neighboring elements which are printed with the original color. Combinations of register marks are particularly conceivable, each combining a color separation or several color separations with a reference color separation (for example black with cyan and magenta, black with yellow, black with special colors).

Another way of communicating with a printing press is via image-related elements, i.e. the information about the content of the image is given to the printing press. On the one hand, this is data that can be derived automatically from an image, such as density histogram, Fourier analysis, color dominant, gray balance type, i.e. Type of color separation, etc., and on the other hand, this is information about the author's intent to display and which elements of the image have the highest priority and which are less important.

• Art des Bildes: Portrait, Gruppenaufnahme, Landschaft.
• Bild ist ruhig - lebhaft.
• Bild hat hohen Kontrast - wenig Kontrast.
• Bild ist grau-, braun-, blau-, cyan-, grün-, gelb-, rot-, violett-dominant.
• Bild ist eher bunt - eher eintönig.
• Die wichtigen Elemente des Bildes.
• Die Prioritäten der Elemente.
• Schwerpunkt auf Farbtreue, Farbbrillianz, oder Bildstruktur.

The description of the intention to display can be carried out by the author in prose form or, for example, in connection with settings that a photographer makes on his camera. This description is translated into a defined structure and given to the picture. As examples of such information:

• Type of picture: portrait, group shot, landscape.
• Picture is calm - lively.
• Image has high contrast - little contrast.
• Image is dominated by gray, brown, blue, cyan, green, yellow, red, violet.
• Picture is rather colorful - rather monotonous.
• The important elements of the picture.
• The priorities of the elements.
• Emphasis on color fidelity, color brilliance, or picture structure.

The additional information can be saved as part of the tag structure. A number of tags are specified or predefined. The tags can be filled with information if the author of the image or the recording apparatus can deliver it.

The printer or intelligent systems on the machine can now use this data to control the machine. If e.g. If the separation structure is known, a color space conversion from RGB to CMYK or a control strategy for the printing ink black can be carried out better. With this additional information, each printing process can use its strengths in such a way that the image-important elements are displayed particularly well, while it can accept weaknesses in reproduction in the less important areas without the author's intention to display suffering too much. If so desired, a "best effort" strategy can be used instead of the "no suprise" strategy.

• 1. Flächenelementbeschreibende Information, d.h. Pixeldaten, aus denen jedes Bild, das elektronisch abgespeichert ist, zusammengesetzt ist,
• 2. Zusatzinformation zur dem menschlichen Auge gemäßen Reporduktion, d.h. Daten zum Farbmanagement,
• 3. Bildinhaltsbezogene Information, wie sie oben beschrieben wurde, d.h. die generische Struktur eines Bildes, Bildwesentliches, im besonderen die malerische Partitur des Bildautors.

A special feature of machines for computer-assisted printing are printing machines that produce the printing form in the machine (computer to press) or that rebuild a printing form for each print copy (computer to paper), as is done, for example, by laser printers. These machines require the full image data information in order to be able to create the printing form. In this case, the structure proposed here is as follows: The data is divided into

• 1. Information describing area elements, ie pixel data from which each image that is electronically stored is composed,
• 2. Additional information on the reduction according to the human eye, ie data on color management,
• 3. Information related to the image content as described above, ie the generic structure of an image, image essentials, in particular the painterly score of the image author.

In order to be able to process the device-independent data of the prepress stage properly, the characteristics of the output device of the electronic prepress stage must be known, a procedure for exchanging the necessary data must be installed and the prepress system that calculates the final page run must have the ability to process it .

The printing machine itself can use self-diagnosis mechanisms on which built-in and external sensors, e.g. Color and density measuring devices are involved to record their condition in the form of operating data. This state can then be assigned to a specific operating state, e.g. Paper class, color class, blanket class or operating temperature class. The current transfer characteristics can be determined for this state. Normally, the transfer characteristic curves are processed with methods of statistical evaluation, averaging and machine condition diagnosis and only then passed on. For a new job or the modification of an existing job, the transfer characteristics can be called up by the prepress department, incorporated into the output and thus tailored specifically to the printing press.

If this communication takes place automatically and via data structures, the optimization of a machine can go much further than was previously the case. Even if a specific characteristic was previously used for a special order for a machine-paper-color combination, a maximum of one characteristic was per Printing unit, ie used per color. In the present case, however, a family of characteristics per printing unit and per color can also be used.

In order to compensate for the ink drop of a sheet-fed offset printing unit over the cylinder circumference, for example, a family of characteristic curves is necessary, which changes constantly depending on the distance of the subject section from the start of printing (FIGS. 2a to 2d). The type of change must be derived from the respective machine parameters. Another set of characteristics that depends both on machine parameters and must also take the subject into account and that can be superimposed on the former is the compensation of stencils. Stenciling occurs when a lot of color is removed from one place and this is adjacent to an area with little color decrease. If these two areas have to be operated with the same color slider because they are in the same zone, only a compromise can be reached that under-colors the dark areas, but over-colors the light areas, so that the print result is flat (Fig. 3). The preliminary stage can calculate and output the characteristic curve requirement locally for each printing plate together with the subject-inherent stencil elements to form an overall characteristic curve. This enables system-related weaknesses in the conventional offset process to be compensated for.

With the help of such characteristic curve communication, printing presses can be developed that require fewer control elements and sensors and are therefore cheaper to manufacture. As long as the requirements for the characteristic curves are known and can be met, the same high quality can be produced with such a simplified machine, since fewer control processes are necessary.

In the context of the invention, the communication interface can also exist virtually, namely when the pre-stage computer and the control center computer are different processes on one and the same computer, the processes being connected to one another, for example, by means of pipes communicate. The communication in the form described can also take place between different program parts of a computer.

In brief, in the sense of the invention, the image data are processed in the preliminary stage, regardless of the device. The characteristics of the printing press are brought to the preliminary stage by means of electronic exchange. Only in the final page run, directly before the output on a material medium, are they then linked to the specific characteristics of the then known output device and the printing press. The printing press has mechanisms for self-diagnosis, on which built-in and external sensors, e.g. Color and density measuring devices are involved, their condition is recorded. This enables the current status to be displayed. The current state is not passed on unfiltered, but is correlated with methods of statistical evaluation, averaging and machine condition diagnosis via the assignment to the paper class, color class, rubber blanket class and operating temperature class. Only after this adjustment is this passed on to the preliminary stage. In particular, machine characteristics are incorporated into this group of transfer characteristics, which have so far been completely disregarded in terms of circulation standards.

Claims (15)

1. Communication procedure for controlling the printing process of a printing machine in a communications system with a computer controlled data transfer, having printing units of the printing machine with individual control units and a communications structure for connecting printing machines and areas of the printing process operating independently of these, characterised in that a data exchange of equipment-independent and printing-machine-specific digital data is carried out at least between a data-processing substation (5) of a pre-printing stage and a main data-processing station (4) connected to the electric control units (20, 21, 22) of the printing machine (1, 2, 3), in the form of preset data and characteristic communication in both directions between the pre-printing stage and the printing machine (1, 2, 3) and the main data-processing station (4) and a data-processing substation (6) of a product planning system (PPS) in the form of an operational and job data communication in both directions between the main data-processing station (4) and the PPS, so that data requests can be served in both directions irrespective of type and data for controlling the printing machine (1, 2, 3) can be obtained from machine type independent data, particularly from the pre-printing stage, and the data to be printed from the pre-printing stage can be influenced by the printing machine (1, 2, 3) itself, in such a way that the main data-processing station (4) is filled on the one hand with data gathered from the pre-printing stage (composition, reproduction, make-up, platemaking) for pre-setting the printing machine (1, 2, 3) and influences the data there in their characteristic features, particularly in dependence on characteristic curves, and on the other hand the data output of the pre-printing stage, e.g. on film or plate, of the printing machine (1, 2, 3) is controlled by the main data-processing station (4), and that on the one hand the operational data of the printing machine (1, 2, 3) are transferred and on the other hand job data, which are raised in the PPS, are retrieved from the main data-processing station (4) for preparing the printing machine.
2. Communication procedure according to claim 1, characterised in that the data of the pre-printing stage are pre-processed and condensed in a suitable way for the printing machine (1, 2, 3), but independently of the machine type, and the ink slide positions are calculated from this condensed data with the inclusion of printing-machine-specific data.
3. Communication procedure according to claim 1, characterised in that a gradual decolourisation of an offset-printing unit is compensated for over the cylinder circumference, in that a characteristic curve or family of characteristics, whose values change continually in dependence on the distance of the subject section from the print start called up by the main data-processing station (4), the changes to the values themselves being derived from the respective machine parameters.
4. Communication procedure according to claim 1, characterised in that ghosting, which appears if a large quantity of ink is taken up by an area, this area being adjacent to one with low ink absorption and the two areas being served by the same ink slide, is balanced out in that a family of characteristics, which takes into account both the machine parameters and the subject by underinking the dark areas and overinking the light areas, is delivered to the pre-printing stage from the main data-processing station (4).
5. Communication procedure according to claim 1, characterised in that the printing process is controlled, particularly mechanically, by means of control elements and corresponding data exchange between the printing stage and the printing machine (1, 2, 3).
6. Communication procedure according to claim 5, characterised in that a search pattern in the form of suitable fields in the subject (10) is used, the fields found being passed on to the printing machine (1, 2, 3) in the form of a data file.
7. Communication procedure according to claims 5 and 6, characterised in that register marks are integrated in the subject by means of the control field communication.
8. Communication procedure according to claim 7, characterised in that selected text elements, consisting of several colours, are selected as register marks in the pre-printing stage.
9. Communication procedure according to one of the previous claims, characterised in that data relating to the image content (e.g. density histogram, Fourier analysis, dominant colours, grey balance, etc.) are exchanged between the printing machine (1, 2, 3) and pre-printing stage for controlling the printing process.
10. Communication procedure according to claim 9, characterised in that information about the display intention of the image author is communicated via the pre-printing stage to the printing machine (1, 2, 3).
11. Communication procedure according to one of the previous claims, characterised in that by using the "Computer-To-Press" procedure and "Computer-To-Paper" procedure the data for controlling the printing process are split into

    a) information describing surface elements (pixel data),

    b) information on reproduction by the human eye (ink management data) and

    c) information relating to image content according to claim 12 (sic; 9).
12. Communication system with a computer controlled data transfer for carrying out a communication procedure for controlling the printing process of a printing machine with electric control units for individual printing units of the printing machine and a communications structure for combining a printing machine and areas of the printing process operating independently of this, characterised in that the control units (20, 21, 22) are networked via a main data-processing station (4), the main station (4) is connected to the areas working independently of the printing machine (1, 2, 3) on a digital basis, which include a pre-printing stage and a production planning system (PPS), via data-processing substations (5, 6) and machine-type-specific interfaces (7, 8), which permit data exchange in both directions, so that data requests in both directions can be carried out in a type-neutral manner and data for controlling the printing machine (1, 2, 3) can be derived from machine-type independent data, particularly from the pre-printing stage and the PPS and the data to be printed from the pre-printing stage of the printing machine (1, 2, 3) themselves can be influenced, in such a way that the main data-processing station (4) is filled on the one hand with data gathered from the pre-printing stage (composition, reproduction, make-up, platemaking) for pre-setting the printing machine (1, 2, 3) and influences the data there in their characteristic features, particularly in dependence on characteristic curves, and on the other hand the data output of the pre-printing stage, e.g. on film or plate, of the printing machine (1, 2, 3) is controlled by the main data-processing station (4).
13. Communication system according to claim 12, characterised in that the interface (5) to the pre-printing stage has a structure which is similar to the TIFF-Format (tagged image file format).
14. Communication system according to claim 12, characterised in that the interface to the pre-printing stage has a structure which tends towards the SGML-Format (standard general markup language).
15. Communication system according to claim 12, characterised in that for managing instructions and machine data the central main data-processing station contains a database system.

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