EP1995067B1 - Method for operating a printing press - Google Patents

Description

The invention relates to a method for operating a printing machine, in particular an offset printing press, according to the preamble of claim 1.

In sheet-fed presses, a sheet-shaped printing material, in the form of so-called printing sheet, is moved through a plurality of printing units in order to apply a printed image to the sheet-shaped printing material. For printing, the printing units use printing plates, typically printing plates, which are produced with consideration of prepress-based image data and taking into account substrate data. This is because the printing substrate used has an effect on the printed image produced during printing, which is why data about the printing substrate are already taken into account during the printing plate production or in the prepress stage. In offset printing, the classification of the types of printing material according to certain properties, namely the color of unprinted sections of the substrate, after the gloss of unprinted sections of the substrate, after the dot gain or the printing characteristics of the printing inks when printing, after the reproduced in the color gamut, and after showing a printed image on the substrate during printing. The color gamut that can be reproduced in print is also called gamut, and show through is also called opacity.

If the actual printing of the printing substrate in the printing press uses a printing material that is different from the printing substrate on the basis of which the printing plates are made, the coloration in the print may shift to the point where waste is printed. Under certain circumstances, the complete print run is unusable and must be destroyed. This causes high costs. So far, there are no procedures to operate a printing machine, which take this problem into account.

From the DE 10 2005 049927 A1 a sensor device and a method for operating the sensor device is known. For the monitoring of the printing substrate transport in a printing machine, the adaptation of the sensor functions to the substrate to be processed is to be simplified. The sensor device is provided with cleaning device for the sensor. In conjunction with a machine control of the printing press, a printing material data storage is connected for automated sensor operation. Thus, the adaptation of the sensor setting and the measurement signal processing to the substrate can take place when changing the substrate.

On this basis, the present invention has the object to provide a novel method for operating a printing press, in particular an offset printing press.

This object is achieved by a method according to claim 1.

According to the invention, at least one unprinted and / or at least one printed portion of the printing material is measured, wherein at least one determined actual value is compared with at least one printing material-dependent setpoint value in order to determine on the basis of the comparison whether the printing material actually used corresponds to that printing material with regard to its properties or printing material data on the basis of which the printing plates used for printing are made.

With the method according to the invention, it is proposed for the first time to measure at least one unprinted and / or at least one printed section of a printing material, and in this case to determine actual values which coincide with substrate-dependent setpoint values are compared. Based on the comparison, it can be determined whether the substrate actually used for printing corresponds to the substrate on the basis of which properties in the prepress stage printing plates have been produced. Optionally, based on this comparison, a printing process may be aborted to avoid printing waste.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below.

• Fig. 1: eine schematisierte Darstellung einer als Bogendruckmaschine ausgebildeten Druckmaschine zur Verdeutlichung des erfindungsgemäßen Verfahrens zum Betreiben einer Druckmaschine.

Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

• Fig. 1 : A schematic representation of a trained as a sheet-fed press printing machine to illustrate the inventive method for operating a printing press.

Fig. 1 shows a highly schematic representation of a sheet-fed press 10, wherein the sheet-fed press 10 has a feeder 11, a boom 12 and a plurality of printing units 13 positioned between the feeder 11 and the boom 12. The printing units 13 are preferably designed as offset printing units and are used for the application of partial printing images on the substrate to be printed.

Of the printing units 13 are each a forme cylinder 14, a transfer cylinder 15 and a counter-pressure cylinder 16 is shown, wherein on the forme cylinders 14 printing plates and on the transfer cylinders 15 are positioned transfer forms. In the printing plates are usually printing plates and the transfer forms to blankets, which is why the forme cylinder 14 also referred to as a plate cylinder and the transfer cylinder 15 as a blanket cylinder.

• die Farbe von unbedruckten Abschnitten des Bedruckstoffs,
• den Glanz von unbedruckten Abschnitten des Bedruckstoffs,
• die Tonwertzunahmen bzw. die Druckkennlinien der Druckfarben beim Drucken,
• den wiedergebbaren Farbumfang beim Drucken, den so genannten Gamut, und
• das Durchscheinen eines Druckbilds durch den Bedruckstoff, die so genannte Opazität.

The printing forms positioned on the forme cylinders 14 used for printing are produced in a so-called prepress stage on the basis of print image data and on the basis of data or properties of the printing material to be printed. The data or properties of the printing material which are to be taken into account in the printing forme production are in particular:

• the color of unprinted sections of the substrate,
• the gloss of unprinted sections of the substrate,
• the tonal value increases or the printing characteristics of the printing inks during printing,
• the reproducible color gamut when printing, the so-called gamut, and
• the transparency of a printed image through the substrate, the so-called opacity.

For the purposes of the present invention, at least one unprinted section and / or at least one printed section of the printing material are measured, in which case at least one determined actual value is compared with at least one printing material-dependent setpoint value. On the basis of the comparison, it is determined whether the substrate actually used for printing corresponds in terms of its properties or substrate data to the substrate on the basis of which the printing plates used for printing were produced in the prepress.

In the event that it is determined that the substrate actually used differs from the substrate on the basis of which the printing plates used for printing have been deviated, an error message or warning message is automatically generated and signaled. For large deviations in the characteristic between the actual substrate used and the presupposed in the prepress substrate if necessary, the printing press is stopped or interrupted the printing of the support. By contrast, with relatively small deviations, regulation can be effected by influencing pressure parameters in order to minimize the color deviations thus caused.

Then, if at least one unprinted portion of the printing material is measured, the measurement of the or each unprinted portion is carried out by means of a color measuring device and / or by means of a gloss meter and / or with the aid of an opacity measuring device. Fig. 1 shows by way of example a color measuring device 17 for unprinted sections of the printing material, which is positioned upstream of the printing units 13 and therefore detects the printing material prior to printing thereof by measurement. The measuring device 17 for measuring the or each unprinted portion of the printing material measures the same inline or online within the printing machine during the printing process or during the print production.

Further shows Fig. 1 a measuring device 18, which serves to measure at least one printed portion of the printing material, wherein the or each printed portion is measured by means of a color measuring device.

According to Fig. 1 is the measuring device 18 downstream of the printing units 13 integrated into the sheet-fed press, so that the measurement of the or each printed portion after printing of the substrate takes place, again inline or online during the print production.

Actual values determined by means of the or each measuring device 17, 18 are transmitted to a control device 19, in which the determined actual values are compared with reference values dependent on the printing material. Each determined actual value is compared in the control device 19 with a plurality of setpoint values stored for different types of substrates having different properties or substrate data in order to determine on the basis of the comparison whether the substrate actually used corresponds in terms of its properties or substrate data to the substrate on the basis of which for printing used printing plates have been produced.

This comparison can take place with the aid of software integrated into the control device 19. Alternatively, this comparison software can also be integrated directly into the or each measuring device 17, 18.

Preferably, the measurement of the or each unprinted portion and the measurement of the or each printed portion by means of a color measuring device, namely a spectral color measuring device, the actual values in the so-called L * a * b color space is determined. These actual values in the L * a * b color space are compared with set values in the L * a * b color space, namely such that each actual value is compared with a plurality of desired values stored for different types of substrate. On the basis of this comparison, it is then determined whether the printing stock actually used corresponds in terms of its properties or printing material data to that printing substrate on the basis of which printing plates have been exposed in the prepress stage.

The measurement of the or each unprinted portion and the measurement of the or each printed portion by means of the color measuring device, namely the spectral color measuring device, preferably takes place according to standards. For this purpose, a black measuring pad is positioned opposite to the color measuring device on the other side of the printing substrate and thus along the transport path of the printing material through the printing press.

With the aid of the method according to the invention, it is possible to check inline or online for print production as to whether a printing material actually used for printing corresponds to the printing material in terms of its properties or printing material data, on the basis of which printing plates have been produced in the prepress stage.

If only relatively small deviations of the printing material type are detected, then the resulting color deviation can be compensated by regulating process parameters. For relatively large deviations, the printing process is preferably aborted in order to avoid the printing of waste.

The invention can be used in sheet-fed printing presses and in web-fed printing presses. The invention can be used in the one-sided and two-sided printing of substrates, the two-sided printing is referred to in sheetfed presses as perfecting, even if the substrate has different properties on both sides. Then, correspondingly different setpoints are stored for the two sides.

LIST OF REFERENCE NUMBERS

10

Sheetfed

11

investor

12

boom

13

printing unit

14

form cylinder

15

transfer cylinder

16

pressure cylinder

17

measuring device

18

measuring device

19

control device

Claims (9)

1. A method for operating a printing press, in particular an offset printing press, wherein in printing couples (13) of the printing press a sheet-like or web-like substrate is printed with the help of printing forms, which are produced taking into account image data and substrate data based on a printing pre-stage,
   wherein as substrate data the colour and/or the gloss of unprinted portions of the substrate and/or the tone value increases or print characteristic curves of the printing colours during printing and/or the gamut and/or the opacity of the substrate are provided,
   characterized in that
   at least one unprinted portion is measured with the help of a colour measuring device and/or a gloss measuring device and/or an opacity measuring device, and/or in that at least one printed portion of the substrate is measured, wherein in the process at least one determined actual value is compared with at least one substrate-dependent set value, in order to determine on the basis of the comparison if the actually used substrate with respect to its characteristics or substrate data corresponds to that substrate, based on the substrate data of which the printing forms used for printing are produced.
2. The method according to Claim 1, characterized in that the or each printed portion is measured with the help of a colour measuring device.
3. The method according to any one of the Claims 1 to 2, characterized in that each determined actual value is compared with a plurality of set values stored for different substrate types with different characteristics or substrate data in order to determine on the basis of the comparison if the actually used substrate with respect to its characteristics or substrate data corresponds to that substrate on the basis of which the printing forms used for the printing are produced.
4. The method according to any one of the Claims 1 to 3, characterized in that the or each unprinted portion is measured prior to the printing of the substrate and/or after the printing of the substrate.
5. The method according to any one of the Claims 1 to 4, characterized in that the or each printed portion is measured after the printing of the substrate.
6. The method according to any one of the Claims 1 to 5, characterized in that as colour measuring device a spectral colour measuring device is used, which determines actual values in the L*a*b colour space, wherein these actual values in the L*a*b colour space are compared with set values in the L*a*b colour space.
7. The method according to any one of the Claims 1 to 6, characterized in that when it is determined that the actually used substrate deviates from that substrate on the basis of which the printing forms used for printing are produced, an error message is automatically generated and displayed.
8. The method according to any one of the Claims 1 to 7, characterized in that when it is determined that the actually used substrate deviate from that substrate on the basis of which the printing forms used for printing are produced, parameters of the printing process are automatically adapted.
9. The method according to any one of the Claims 1 to 8, characterized in that the measuring of the or each unprinted portion of the substrate and/or of the or each printed portion of the substrate takes place in line or on line for the printing.

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