EP1671789B1 - Method for regulation of the inking in an offset printing machine - Google Patents

Description

The invention relates to a method for controlling the coloring in an offset printing press according to the preamble of claim 1.

When printing a substrate is successively moved through several printing units of a printing press, wherein in each printing unit usually a printing ink is applied to the substrate. In the case of autotypical se-tenant printing, the four scale colors black, magenta, cyan and yellow and, if appropriate, special colors are generally printed, with a separate printing unit and therefore inking unit being present for each of these printing inks. The inking unit of each printing unit has a Farbdosiereinrichtung, wherein the Farbdosiereinrichtung comprises a number of ink zones corresponding number of Farbzonenstellelementen. The Farbzonenstellelemente are also referred to as a color slider or color meter. Depending on the position of the ink zone setting elements, ink is applied to an ink fountain roller, which is also referred to as a ductor roller. The color quantity applied to the ductor roller depending on the ink zone setting elements per ink zone is transferred from a lifting roller or from a film roller to an inking roller of the inking unit disposed downstream of the Haber roller or film roller. The ink is moved over several inking rollers in the direction of a plate cylinder or plate cylinder of each printing unit. On the forme cylinder of a printing unit rolls at least one inking roller serving as the inking roller of the respective inking unit. Accordingly, the printing ink reaches at least one printing plate positioned on the forme cylinder via the or each inking roller. With the forme cylinder acts a so-called transfer cylinder or blanket cylinder, which transfers the ink from the forme cylinder to the substrate.

The color design of a printed product to be printed is set in a so-called pre-press. In this case, for example, so-called area coverage values are defined for each ink zone to be printed and thus for all inking units of the printing machine involved in the printing for each color zone. As a function of these area coverage values, the ink zone setting elements are adjusted and thus the zonal coloration is determined.

It is already known from the state of the art to measure the coloring which takes place on the printing substrate during printing and, depending thereon, regulates the zonal coloring of the inking units involved in the printing. For this purpose, measuring ranges printed on the printing material, so-called pressure control elements, are usually measured outside of a subject, wherein actual values of the zonal coloring determined in this case are transmitted to a regulating device of the printing press. In the control device, the actual values are compared with predetermined setpoint values in order to generate actuating signals for the ink zone setting elements as a function of the comparison between the actual values and the setpoint values and thus dependent on the control deviation between the measured actual values and the predefined setpoint values. Already an automatic control of the zonal coloring is possible. It is also possible to measure areas within a subject as measuring ranges and to regulate the zonal coloring as a function thereof. It is also possible to measure print control elements and regions within the subject outside of a subject as measurement areas.

From the publication DE-A-195 15 499 For example, a method of controlling coloration when printing with more than three inks is known.

In the publication EP-A-1 302 325 For example, a printing apparatus for applying ink to a printing medium will be described.

In the control of zonal coloration based on the measurement of pressure control elements printed, for example, outside the subject, it may happen that, although the measured actual values coincide with the predetermined target values for all measurement ranges, a deviation between actual values and Setpoints is determined. To date, there are no known methods of color control that take this phenomenon into account.

On this basis, the present invention is based on the problem to provide a novel method for controlling the color in an offset printing machine.

This problem is solved by a method for controlling the color in an offset printing machine according to claim 1. According to the invention, the control deviations between the measured actual values and the predetermined nominal values are modified on the basis of a model of the respective inking unit and / or on the basis of data of the subject.

For the purposes of the present invention, it is proposed to modify the control deviations between the actual values determined by measurement of measuring ranges and the predetermined desired values on the basis of data of the subject and / or on the basis of a model of the respective inking unit. The invention is based on the idea that a deviation between the actual values of the subject and the predefined setpoint values, although the actual values of the measuring ranges coincide with the predetermined setpoint values, on the expression of the subject to be printed and / or on the rolling behavior and optionally on the traversing behavior of the inking unit can depend. Depending on an analysis of the subject and / or an inking model, the control deviations between the actual values measured at the measuring ranges and the predetermined desired values are accordingly modified in order to achieve a correspondence between desired values and actual values in the subject.

According to an advantageous development of the invention, at least one measuring area is measured per color zone of the subject, wherein a circumferential strip covered by the measuring area is smaller than a circumferential strip covered by the respective color zone, and if, in the circumferential strip covered by the measuring area, one from the data of the Subjects certain area coverage value is less than a predetermined limit, the default value for the corresponding Increases inking zone actuator or the measured actual value is reduced.

According to a further advantageous development of the invention, a coverage area value dependent on the stenciling behavior of the respective inking unit is determined from the data of the subject and the model of the respective inking unit for the circumferential strip covered by the measuring area, wherein, if this areal coverage value is greater than a predetermined limit value, the predetermined one Setpoint for the corresponding Farbzonenstellelement reduced or the measured actual value is increased.

According to a further advantageous embodiment of the invention, a drop in color is determined depending on the model of the respective inking, wherein when in the covered by the measuring range perimeter strip is a maximum of the color drop, increases the predetermined target value for the corresponding Farbzonenstellelement or the measured actual value is reduced, and wherein, when there is a minimum of the color drop in the circumferential strip covered by the measuring area, the predetermined target value for the corresponding inking zone actuating element is reduced or the measured actual value is increased.

The above advantageous developments of the invention can be used either alone, in subcombinations or in an overall combination in the color control according to the invention.

Fig. 1:

eine schematisierte Darstellung eines Farbwerks einer Offsetdruckmaschine zur Verdeutlichung des erfindungsgemäßen Verfahrens zur Regelung der Farbgebung;

Fig. 2:

einen Querschnitt durch das Farbwerk der Fig. 1 entlang der Schnittlinie II-II; und

Fig. 3:

eine schematisierte Darstellung eines zu druckendes Druckbogens zur weiteren Verdeutlichung des erfindungsgemäßen Verfahrens zur Regelung der Farbgebung.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. An embodiment of the invention will be described, without being limited thereto, with reference to the drawing. Showing:

Fig. 1:

a schematic representation of an inking unit of an offset printing machine to illustrate the inventive method for controlling the coloring;

Fig. 2:

a cross section through the inking of Fig. 1 along the section line II-II; and

3:

a schematic representation of a printed sheet for further clarification of the method according to the invention for controlling the coloring.

Hereinafter, the present invention will be described with reference to FIG Fig. 1 to 3 described in more detail, although using the example of measuring areas that are outside of a subject as pressure control elements. It should be noted that the invention can also be used analogously for measuring ranges that lie within a subject.

Fig. 1 and 2 show an inking unit 10 embodied as a lifting inking unit of an offset printing press, wherein the inking unit 10 comprises a fountain roller 11 which receives printing ink held ready in an ink fountain 12. With the ductor roller 11, a lifting roller 13 cooperates, wherein the lifting roller 13 receives from the ink fountain roller 11 printing ink in the form of a so-called lift strip and intermittently in the direction of arrow 14 to one of the lifting roller 13 downstream inking roller 15 transfers. The inking roller 15 are further inking rollers 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 and 26 downstream, wherein the inking rollers 16 to 26 transport the ink in the direction of a forme cylinder 27. The inking rollers 23, 24, 25 and 26 roll on the forme cylinder 27 and are therefore also referred to as inking rollers. At least one printing plate is positioned on the forme cylinder, with the inking rollers 23 to 26 applying the printing ink to the printing plate. The amount of ink that is transferred from the ink fountain 12 to the ink fountain roller 11 depends on a zonal coloring of a subject to be printed. As Fig. 2 can be removed, the color box 12 so-called Farbzonenstellelemente 28 are assigned, wherein on the Farbzonenstellelemente 28 which per color zone on the ink fountain roller 11 transmitted amount of color is adjustable. In the embodiment shown, in which the inking unit 10 is designed as a lift inking unit, the Farbzonenstellelemente are designed as a color slider. The ink slide and the squeegee roller are part of a so-called Farbdosiereinrichtung the inking unit.

It should be noted that in Fig. 1 illustrated inking unit 10 is preferably used in sheet-fed offset printing presses. In roll-offset printing presses, inking units are used which, instead of color slides, comprise colorimeters as color zone setting elements and, instead of the lifting roller, a so-called film roller.

Fig. 3 schematically shows a substrate 29, which is printed with a sujet 30 and outside of the subject 30 with pressure control elements 31, wherein the pressure control elements 31 are printed outside the actual subject 30 in the form of a control strip 32 on the substrate 29. In the illustrated embodiment of the Fig. 3 the printed on the substrate 29 sujet 30 is divided into twelve color zones 33; wherein the per ink zone 33 applied to the substrate 29 ink by a corresponding number of Farbzonenstellelementen 28 is adjustable. In the example of Fig. 3 For each color zone 33, a print control element 31 is printed on the printing substrate 29 outside the subject 30, wherein a peripheral strip 34 covered by the print control element 31 is smaller or narrower than the peripheral strip covered by the respective color zone 33. The pressure control elements 31 printed outside of the subject 30 are measured densitometrically and / or colorimetrically and / or spectrally and actual values determined here are compared with predetermined setpoint values in a control device in order to depend on the comparison between the actual values obtained by measuring the pressure control elements 31 and the predetermined setpoint values To generate control signals for the Farbzonenstellelemente 28 for automatically controlling the zonal coloring of the subject 30.

For the purposes of the present invention, it is now proposed to modify the control deviations between the actual values measured on the pressure control elements 31 outside the subject 30 and the predetermined set values on the basis of data of the subject 30 and / or on the basis of data of the inking unit 10.

In this way, the effect can be counteracted that, although the actual values detected in the area of the pressure control elements 31 coincide with the corresponding desired values, deviations between actual values and desired values can be detected in the subject. Preferably, the control deviations are modified both on the basis of data of the subject and on the basis of a model of the respective inking unit.

When modifying data based on data from the subject, digital pre-press data is used, either as low-resolution PPF or JDF format data or as high-resolution image data. The high-resolution image data are preferably so-called bitmaps of the individual color separations, which are usually used for the production of printing forms.

The model of the inking unit, which is used to modify deviations, depends on the rolling behavior and, if necessary, traversing behavior of the rollers of the inking unit. The model of the inking unit can also incorporate data about the materials used in the inking unit as well as the dynamic behavior of the inking unit.

As already mentioned, for each color zone 33 of the subject 30, at least one print control element 31, which is printed on the printing substrate 29 outside the subject 30, is measured, wherein a peripheral strip 34 covered by the print control element 31 is smaller or narrower than one covered by the respective color zone 33 Is circumferential strip.

It is now within the meaning of the present invention to determine from the data of the subject, which are preferably provided from a digital pre-press, for the coverage area covered by the print control element 31, a coverage value. If this areal coverage value determined from the data of the subject is smaller than a predefined limit value, then in accordance with the present invention the predetermined setpoint value for the corresponding color zone setting element is increased or the measured actual value is reduced.

For example, if the area coverage value determined from the data of the subject for the perimeter strip covered by the print control element 31 is between 0% and 0.5%, the target value for the corresponding inking zone actuator is increased by an amount X, which is from the data On the other hand, the area coverage value determined for the subject varies between 0.5% and 2%, so the setpoint can be increased by an amount Y, the amount Y being smaller than the amount X. If, however, the area coverage value determined for the circumferential strip covered by the print control element is greater than 2%, no increase in the reference value takes place.

It should be pointed out that this adjustment law for the setpoint value is merely exemplary and that, depending on the determined areal coverage value, any complex modification of the control deviation between setpoint values and actual values can be undertaken.

With the above-described modification of the deviation between nominal values and actual values as a function of a surface coverage value which is determined from the sujet data of a circumferential strip covered by the print control element, the effect can be counteracted that, if in the circumferential strip of the subject in which the pressure control element is located, no color decrease takes place in the inking unit ink builds up and so the pressure control element contains a higher color density, as with further color decrease the Case would be. Accordingly, in the context of the present invention, if in the circumferential strip covered by the print control element a surface coverage value determined from data of the subject is smaller than a predefined limit value, the predetermined target value for the corresponding inking zone control element is increased or the measured actual value is reduced.

In a further development of this concept according to the invention, the peripheral strip covered by the pressure control element can be subdivided into a plurality of sub-strips, wherein an area coverage value is determined for each of the sub-strips from the data of the subject. It is then possible to use an averaging of the area coverage values of these sub-strips to modify the control deviation between the setpoint and the actual value. Alternatively, only the areal coverage value of that sub-stripe can be used to adapt the setpoint value and / or the actual value and thus to modify the control deviation between the setpoint value and the actual value within which a measurement area of the pressure control element lies.

If a traversing behavior of at least one roller of the inking unit is known from the inking unit model of the inking unit, according to a further advantageous development of the invention not only is the area coverage covered by the printing control member determined from the sujet data, but such areal coverage values are also determined for adjacent circumferential bands , Preferably, for a plurality of adjacent circumferential stripes, corresponding areal coverage values are determined from the data of the subject, wherein in the change of the desired value and / or the actual value of the circumferential strip covered by the control element, more distant circumferential stripes are weighted less heavily than closer circumferential stripes.

According to a further aspect of the present invention, a so-called drop in color is determined depending on the model of the respective inking unit. A drop in color usually sets in when the rolling on the forme cylinder Ink rollers can not apply printing ink on the printing form due to a clamping channel for a printing plate. If it is determined from the inking unit model that a pressure control element is affected by such a drop in color, a modification of the control deviation between the measured setpoint and the preset actual value also takes place.

If, on the basis of the color drop determined from the inking system, it is ascertained that there is a maximum of the color drop in the circumferential strip covered by a pressure control element, then the predetermined target value for the corresponding ink zone actuating element is increased or the measured actual value is reduced. If, on the other hand, there is a minimum of the ink drop in the peripheral strip covered by the pressure control element, then the predetermined desired value for the corresponding ink fountain element is reduced or the measured actual value is increased.

According to a further aspect of the present invention, a surface coverage value dependent on the stenciling behavior of the inking unit is determined from the data of the subject and from the model of the inking unit for a circumferential strip covered by the print control element. If this area-coverage value, which depends on the patterning behavior, is greater than a predefined limit value, then the specified target value for the corresponding ink-zone setting element is reduced or the measured actual value is increased in the sense of the present invention. In this case, the procedure is as follows, that for the circumference strip covered by the pressure control element, a surface coverage value is determined, which is a development length of a application roller in front of the peripheral strip covered by the pressure control element. Preferably, for the two applicator rollers with the largest color flow, a respective unwinding length of these rollers is determined in front of the circumference strip covered by the pressure control element, a corresponding areal coverage value. If the area coverage determined in this case is greater than a predefined limit value, preferably the predefined setpoint value for the corresponding ink zone setting element is reduced.

In this way, the effect can be taken into account that when the covered by the pressure control element perimeter strip a circumferential length of a inking roller from a perimeter strip with high area coverage is removed, the pressure control element displays a lower color density, since such a strong decrease in color after a rollover of the inking roller not yet complete can be compensated.

In a concrete exemplary embodiment, it is possible to proceed in such a way that, if from the data of the subject and the inking model for a circumferential strip, which is a development length before the circumferential strip covered by the print control strip, a surface coverage value of between 80% and 95% is determined, the nominal value for the corresponding color zone element is reduced by an amount A, whereas if this area value is between 95% and 100%, the set point is reduced by a value B, where B is greater than A. If the area coverage values are less than 80%, there will be no reduction in the setpoint for the corresponding color zone actuator. Again, the adjustment can be made arbitrarily complex depending on the stenciling behavior of the inking again.

For the purposes of the present invention, a method for controlling the color scheme is proposed, in which system deviations between actual values and predetermined setpoint values acquired at print control elements printed outside the actual subject are modified depending on data of the subject as well as on an inking unit model. As a result, effects such as the inking unit, the drop in color and the fact that a covered by a pressure control element perimeter strip is smaller than a covered by the respective color zone perimeter strip, bill be taken into account. As a result, the color can be optimized significantly during printing.

LIST OF REFERENCE NUMBERS

10

inking

11

duct roller

12

paintbox

13

vibrator roller

14

arrow

15

Inking roller

16

Inking roller

17

Inking roller

18

Inking roller

19

Inking roller

20

Inking roller

21

Inking roller

22

Inking roller

23

Inking roller

24

Inking roller

25

Inking roller

26

Inking roller

27

form cylinder

28

Ink-zone adjusting element

29

substrate

30

subject

31

Pressure control element

32

control strip

33

color zone

34

peripheral strip

Claims (24)

1. A method for regulating the inking in at least one inking unit (10) of an offset printing machine, namely for regulating the zonal inking, which can be adjusted by ink-zone actuating elements (28) of the respective inking unit (10), wherein to this end measuring regions are measured and actual values that are ascertained thereby are compared with predetermined desired values in order to generate actuating signals for the ink-zone actuating elements (28) as a function of the comparison between the actual values and the desired values, characterised in that the deviations between the measured actual values and the predetermined desired values are modified on the basis of a model of the respective inking unit (10) and/or on the basis of data of the subject (30).
2. A method according to claim 1, characterised in that the deviations between the measured actual values and the predetermined desired values are modified on the basis of data of the subject (30).
3. A method according to claim 2, characterised in that the deviations between the measured actual values and the predetermined desired values are modified on the basis of data of the subject (30) and on the basis of a model of the respective inking unit (10).
4. A method according to one or more of claims 1 to 3, characterised in that the model of the respective inking unit (10) is dependent on the structure of the inking unit (10), in particular on roll-off characteristics and if applicable reciprocating characteristics of the rollers (15, 16, 17, 18, 19, 20, 21, 22) of the inking unit (10).
5. A method according to one or more of claims 1 to 4, characterised in that data from a digital pre-printing stage are used as data of the subject (30).
6. A method according to claim 5, characterised in that low-resolution data in PPF format or JDF format are used as data of the subject (30).
7. A method according to claim 5, characterised in that high-resolution image data, preferably bit maps of the individual ink separations that are also used to produce printing plates, are used as data of the subject (30).
8. A method according to one or more of claims 1 to 7, characterised in that print-control elements (31) that are printed outside a subject (30) are measured as measuring regions.
9. A method according to claim 8, characterised in that print-control elements (31) that are positioned in a control strip (32) outside the subject (30) are measured.
10. A method according to one or more of claims 1 to 7, characterised in that regions within a subject (30) are measured as measuring regions.
11. A method according to one or more of claims 1 to 7, characterised in that print-control elements (31) that are printed outside a subject (30) and regions within the subject (30) are measured as measuring regions.
12. A method according to one or more of claims 1 to 11, characterised in that the measuring regions are measured densitometrically and/or using ink-metrics and/or spectrally.
13. A method according to one or more of claims 1 to 12, characterised in that at least one measuring region is measured per ink zone (33) of the subject (30), with a peripheral strip (34) that is covered by the measuring region being smaller than a peripheral strip that is covered by the respective ink zone (33).
14. A method according to claim 13, characterised in that when in the peripheral strip (34) covered by the measuring region an area-coverage value determined from the data of the subject (30) is smaller than a predetermined limit value, the predetermined desired value for the corresponding ink-zone actuating element (28) is increased or the measured actual value is reduced.
15. A method according to claim 14, characterised in that, depending on the model of the respective inking unit (10), in addition to the area-coverage value of the peripheral strip covered by the measuring region an area-coverage value of at least one adjacent peripheral strip is used to change the desired value and/or actual value.
16. A method according to claim 15, characterised in that the change in the desired value and/or actual value is carried out on the basis of area-coverage values of a plurality of adjacent peripheral strips, with peripheral strips that lie further away being weighted to a lesser extent when changing the desired value and/or actual value than peripheral strips that lie closer.
17. A method according to one or more of claims 13 to 16, characterised in that the peripheral strip (34) that is covered by the measuring region is subdivided into a plurality of partial strips, with an area-coverage value being ascertained from the data of the subject (30) for each of the partial strips.
18. A method according to claim 17, characterised in that an averaging of the area-coverage values of the partial strips is used to adapt the desired value and/or actual value.
19. A method according to claim 17, characterised in that only the area-coverage value of that partial strip within which a measurement field of the measuring region lies is used to adapt the desired value and/or actual value.
20. A method according to one or more of claims 13 to 19, characterised in that a fading of ink is ascertained as a function of the model of the respective inking unit (10), in which case when in the peripheral strip (34) covered by the measuring region the ink-fading is at a maximum, the predetermined desired value for the corresponding ink-zone actuating element (28) is increased or the measured actual value is reduced.
21. A method according to claim 20, characterised in that when in the peripheral strip (34) covered by the measuring region the ink-fading is at a minimum, the predetermined desired value for the corresponding ink-zone actuating element (28) is reduced or the measured actual value is increased.
22. A method according to one or more of claims 13 to 21, characterised in that an area-coverage value that is dependent on the ghosting characteristics of the respective inking unit (10) is ascertained from the data of the subject (30) and the model of the respective inking unit (10) for the peripheral strip (34) that is covered by the measuring region, and in that when this area-coverage value is greater than a predetermined limiting value, the predetermined desired value for the corresponding ink-zone actuating element (28) is reduced or the measured actual value is increased.
23. A method according to claim 22, characterised in that an area-coverage value that is a wind-off length of at least one ink-application roller (23, 24, 25, 26) ahead of the peripheral strip covered by the measuring region is ascertained for the peripheral strip (34) that is covered by the measuring region.
24. A method according to claim 23, characterised in that an area-coverage value is ascertained for the two ink-application rollers (23, 24, 25, 26) with the greatest ink flow a respective wind-on length of these ink-application rollers (23, 24, 25, 26) ahead of the peripheral strip (34) covered by the measuring region, with the desired value and/or the actual value being changed as a function of these area-coverage values.

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