EP0741029A2 - Method for regulating the inking in a printing machine - Google Patents

Abstract

A colour printing process has the print quality continuously monitored to generate data (M) that is processed to generate an average value (M1). Changes in the values are used in an identification process where the type of response characteristics (A) is determined and the time required for the system to respond to a correction can be accurately determined. This allows a prediction to be made of when the system will be outside of a defined tolerance band and allows a correcting operation to be generated.

Description

The invention relates to a method for controlling or regulating the coloring during the printing process, in particular during the continuous printing process, of a printing press, wherein color measurement data are obtained from the continuously produced printed images and used for the control or regulating process for influencing the coloring when a predetermined tolerance is exceeded is.

A method of the type mentioned at the outset is apparent from European Patent 0 196 431. In this known method, variables are used to regulate the desired color balance, which are determined by correlating ink layer thicknesses and / or screen dot sizes of different printing inks. If these quantities fall outside the tolerance ranges assigned to them, corrective intervention is made in the printing process.

The invention is also concerned with achieving a uniform printing result. The object is to create a method for adjusting the coloring which can be carried out in a quick and simple manner.

This object is achieved in that the temporal development of the color measurement data is used for a trend estimate, that the trend estimate is evaluated, and that corrective control or regulation of the coloring is carried out when certain trend estimate data lie outside the tolerance. According to the invention, existing ones are thus Information, namely the color measurement data of the continuously created print images recorded by means of an optical detection device or the like, estimates the future development. There is therefore preventive behavior. The color measurement data known from the "history" are preferably stored and further developed with regard to their expected development, so that the above-mentioned trend estimate is available. The trend estimate is subjected to the evaluation in order to decide whether a corrective intervention in the coloring of the printing press should take place. This corrective intervention is always carried out when the color measurement data that will probably arise in the future exceed a predefinable tolerance.

It is preferably provided that a linear trend estimation is carried out. The color measurement data already determined are therefore developed further in the sense of a linear trend estimate, preferably represented on the basis of a straight line, it being checked during the evaluation whether the straight line exceeds or falls below a predetermined tolerance threshold due to its slope.

It is advantageous if the future point in time is determined in the trend estimate, in which the trend estimate data exceed the tolerance and that the period up to this point in time is compared with a tolerance period. The trend estimation is thus continued into the future until its deviation from a target value of the color measurement data is so great that the predetermined tolerance is exceeded. The point in time when the limit is exceeded defines the previously mentioned time period. This time period is compared with a tolerance time period, that is to say a predetermined size. If the time span is smaller than the tolerance time span, corrective action is taken in the control Coloring intervened. If the future time period is longer than the tolerance time period, the color is not corrected.

It is advantageous if, as mentioned, a trend line is formed from the color measurement data derived from the known temporal development, which is provided with an extension, the extension being based on or forming the trend estimate.

Finally, it is advantageous if the trend line is developed from the evaluated color measurement data of at least two time periods. In this case, mean values can be calculated within the two time periods, so that two average color measurement data are available at two different times, from which the point in time when the tolerance is exceeded can then be calculated using a simple straight line equation. In this way, a considerably more complex linear approximation is avoided.

Since the coloring of a printing press can only be influenced zonally due to a zonally constructed inking unit, preferably only one decision per zone is derived as to whether, and if so, in what way the coloring is to be regulated or controlled. As shown, this decision is based on the temporal development of the color measurement data. These color measurement data are preferably taken from a predeterminable color measurement field of the printed image. For this purpose, at least one location within the zone must be measured for each zone to be controlled in order to obtain the corresponding color measurement data. It is now possible to provide only one measuring location or several measuring locations within a zone. In turn, several primary data values, for example four color measurement data, can arise per measurement location, namely in particular for the X, Y and Z standard spectral values and a value for infrared. Because the printed image in particular Each sheet is measured, the method according to the invention offers a quick and easy way of carrying out the color control or regulation due to the small amount of data.

The drawing illustrates the method according to the invention, namely FIG. 1 shows a diagram in which the color measurement data are shown as a function of time and FIG. 2 shows a flow diagram of the method according to the invention.

In the method for controlling or regulating the coloring during the printing process, in particular continuous printing process, of a printing press, color measurement data M are determined in online operation by means of an optical detection device. The optical detection device determines the color values in the form of color measurement values at a selectable number of image locations of each printed sheet, by means of which the color of the printing press can be influenced by a downstream controller. In the following - for the sake of simplicity - the invention is explained using only a "one-dimensional" example. However, the explanations also apply, of course, to multidimensional systems, that is to say, for example, to several measurement locations within one or more zones, with several color measurement data being generated per measurement location due to the different printing inks and also infrared.

According to FIG. 1, it is assumed that the number of N ₁ color measurement data occurs in a first time range Z ₁ . A later, however, just like the first time measurement range Z ₁ - a second time range Z ₂ lying in the past has the number N ₂ of color measurement data. Both time ranges Z ₁ and Z ₂ belong to the history, that is to say they are in the past, and the number of color measurement data respectively determined by means of an optical detection device can be preselected is, that is, a corresponding time division can be made within the two time ranges, with a measurement and thus a determination of the data value taking place at the respective time. Each sheet is preferably detected. The values of the determined color measurement data M are plotted on the ordinate, the nominal value being indicated by S. With A the current coloring is drawn as a curve. If an average of all the color measurement data M determined there is formed within the first time range Z ₁ , the average M ₁ that is to be present at the time t ₁ is obtained, for example. The same procedure is followed in the second time range Z ₂ , which results in the mean value M ₂ at time t ₂ . The mean values M ₁ and M ₂ can preferably be moving averages. If a straight line is now calculated which runs through the two mean values M ₁ and M ₂ , the result is the trend line g shown in FIG. 1, which passes through the two mean values M ₁ and M ₂ and is provided with an extension V which covers a period in the future. It is assumed that the time T = 0 on the abscissa represents the current time when the method was carried out, so that all actions prior to the time T belong to the past and the actions carried out from this time T relate to the prognosis. The straight-line extension V of the straight line g leads to the fact that, over time, the deviation of the color measurement data M from the target value S becomes larger and larger due to this linear trend estimate, so that at a certain point in time there is a deviation from the target value S which is a predefinable tolerance σ exceeds. This can be g + σ with rising straight line or g - with falling straight line, that is, the tolerance limits lie around the target value S.

wobei M und t beliebige Farbmeßwerte beziehungsweise Zeitpunkte darstellen. $$\begin{array}{c}\begin{array}{c}{\text{T}}_{\text{+}}{\text{= (S + - M}}_{\text{2}}\text{)}\frac{{\text{|t}}_{\text{2}}{\text{- t}}_{\text{1}}\text{|}}{{\text{M}}_{\text{2}}{\text{- M}}_{\text{1}}}\text{+ t2}\\ {\text{T}}_{\text{-}}{\text{= (S - - M}}_{\text{2}}\text{)}\frac{{\text{|t}}_{\text{2}}{\text{- t}}_{\text{1}}\text{|}}{{\text{M}}_{\text{2}}{\text{- M}}_{\text{1}}}{\text{+ t}}_{\text{2}}\\ {\text{M}}_{\text{1}}\text{=}\frac{\text{1}}{{\text{N}}_{\text{1}}}\sum_{=\text{1}} {\text{M}}_{\text{t}}\\ {\text{M}}_{\text{2}}\text{=}\frac{\text{1}}{{\text{N}}_{\text{2}}}\sum_{=\text{2}} {\text{M}}_{\text{t}}\end{array}\end{array}$$

It can be seen from FIG. 1 that the extension V of the trend line g intersects the tolerance (+ σ) at a specific point in time (or from a specific arc number). The time T ₊ σ is present. The linear trend estimate therefore defines a time period between T = 0 and T _{+ σ} , which is compared with a predetermined tolerance time period T _T. If the time period T _{+ σ} lies within the tolerance time period T _T , the color control is activated and thus affects the coloring of the printing press. If the time T _{+ σ were} not within the tolerance period T _T , there is no intervention in the color control. The same applies if the tolerance - σ is exceeded. The tolerance time period T _T is preferably determined in advance with knowledge of the machine dynamics, that is to say the reaction time of the inking unit of the printing press. The following relationships apply to the sizes of FIG. 1: $$\begin{array}{c}\begin{array}{c}\text{g =}\frac{{\text{M}}_{\text{2nd}}{\text{- <figure-callout id="1" label="M" filenames="imgf0002.png" state="{{state}}">M</figure-callout>}}_{\text{1}}}{{\text{| t}}_{\text{2nd}}{\text{- <figure-callout id="1" label="t" filenames="imgf0002.png" state="{{state}}">t</figure-callout>}}_{\text{1}}\text{|}}\\ \text{g =}\frac{{\text{M - M}}_{\text{2nd}}}{{\text{t - t}}_{\text{2nd}}}\end{array}\end{array}$$

where M and t represent any color measurement values or points in time. $$\begin{array}{c}\begin{array}{c}{\text{T}}_{\text{+}}{\text{= (S + - M}}_{\text{2nd}}\text{)}\frac{{\text{| t}}_{\text{2nd}}{\text{- <figure-callout id="1" label="t" filenames="imgf0002.png" state="{{state}}">t</figure-callout>}}_{\text{1}}\text{|}}{{\text{M}}_{\text{2nd}}{\text{- <figure-callout id="1" label="M" filenames="imgf0002.png" state="{{state}}">M</figure-callout>}}_{\text{1}}}\text{+ t2}\\ {\text{T}}_{\text{-}}{\text{= (S - - M}}_{\text{2nd}}\text{)}\frac{{\text{| t}}_{\text{2nd}}{\text{- <figure-callout id="1" label="t" filenames="imgf0002.png" state="{{state}}">t</figure-callout>}}_{\text{1}}\text{|}}{{\text{M}}_{\text{2nd}}{\text{- <figure-callout id="1" label="M" filenames="imgf0002.png" state="{{state}}">M</figure-callout>}}_{\text{1}}}{\text{+ t}}_{\text{<figure-callout id="1" label="2nd M" filenames="imgf0002.png" state="{{state}}">2nd </figure-callout>}}& \\ {\text{M}}_{}{}_{\text{1}}\text{=}\frac{\text{1}}{{\text{<figure-callout id="1" label="N" filenames="imgf0002.png" state="{{state}}">N</figure-callout>}}_{\text{1}}}\sum_{=\text{1}} {\text{M}}_{\text{t}}\\ {\text{M}}_{\text{2nd}}\text{=}\frac{\text{1}}{{\text{N}}_{\text{2nd}}}\sum_{=\text{2nd}} {\text{M}}_{\text{t}}\end{array}\end{array}$$

It is preferably provided that the color measurement data of a measuring field are continuously written into a (ring) memory assigned to the measuring field and are thus available for further processing. A measuring field is to be understood as a certain part of a printed image, the printed image preferably being subdivided into strips corresponding to the color zones, with separate lines separating the individual fields, namely the named measuring fields, transverse to the strips.

• wenn nur ein Meßfeld dies erfordert; oder
• wenn die Mehrzahl der Meßfelder dies fordern; oder
• nur wenn alle Meßfelder dies fordern;
• wenn zumindest eine besonders ausgezeichnete Meßstelle dies fordert.

The decision, in particular the zonal decision to regulate the color, naturally depends on the results of the trend estimation of all color measuring points in the corresponding zone. Different strategies are preferably conceivable: the color is then regulated,

• if only one measuring field requires it; or
• if the majority of the measuring fields require this; or
• only if all measuring fields require this;
• if at least one particularly excellent measuring point requires it.

The results of the trend estimates of the individual measuring points and / or measuring fields can also be summarized in a weighted manner in order to derive a zonal decision.

FIG. 2 shows a flow chart which clarifies the individual process steps. In step 1, ₁ M color measurement data are detected within the first time range Z. In step 2, further color measurement data M are determined in the second time range Z ₂ . In step 3, the color measurement data M is averaged within the first time range Z ₁ and within the second time range Z ₂ , so that average values M ₁ and M ₂ are present. In the following step 4, the straight line g is then calculated by means of a computer or the like and the extension V of the straight line which forms the basis of the forecast is formed. In the following step 5, the time period is then determined within which the values of the linear trend estimate (extension V) exceed the specified tolerance + σ or - σ. In step 6, a comparison of the determined time period with a predefinable tolerance time period T _{T takes place} . In step 7, depending on the comparison mentioned above, either the coloring of the printing press is affected or not.

Reference symbol list

Z ₁ , Z ₂

Time range

N ₁ , N ₂

Number of color measurement data

M

Color measurement data

S

Setpoint

A

current coloring course

M ₁ , M ₂

Average

t ₁ , t ₂

Time range

T

time

V

renewal

G

Just

g + σ

rising straight line

g -σ

descending straight line

T + σ

time

T _T

Tolerance period

1, 2, 3, 4, 5, 6, 7

Procedural steps

Claims (5)

Method for controlling or regulating the coloring during the printing process, in particular during the continuous printing process, of a printing press, wherein color measurement data are obtained from the continuously produced print images and used for the control or regulating process for influencing the coloring if a predetermined tolerance is exceeded,
characterized by
that the temporal development of the color measurement data (M) is used for a trend estimate, that the trend estimate is evaluated and that corrective control or regulation of the coloring takes place if certain trend estimate data lie outside the tolerance (+ σ, -σ). Method according to claim 1,
characterized by
that a linear or non-linear trend estimation is carried out. Method according to one of the preceding claims,
characterized by
that the trend estimate determines the future time period (T _{+ σ} , T _-σ ) in which the trend estimate data exceeds the tolerance (+ σ, -σ) and that the time period (T _{+ σ} , T _-σ ) with a tolerance time period ( T _T ) is compared. Method according to one of the preceding claims,
characterized by
that a trend line (g) is formed from the color measurement data from the temporal development, which with an extension (V) is provided, the extension (V) being the basis of the trend estimate. Method according to one of the preceding claims,
characterized by
that the trend line (g) is developed from the evaluated color measurement data (M ₁ , M ₂ ) of two time periods (Z ₁ , Z ₂ ).

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