EP2762316B1 - Method for controlling a parameter of an inking system - Google Patents

Description

The invention relates to a method for controlling at least one control parameter from a number of parameters of an inking unit of an offset printing machine. Furthermore, the invention relates to an offset printing machine with at least one inking unit, which has a control unit for carrying out the method.
The control parameter is an opening of a color meter and / or a rotational speed of a Farbduktors. This can be used to set the color quantity and color density.
Such methods are used in printing machines, especially in offset printing presses, during startup and during production. In such machines, one or more colors are successively applied to the substrate, typically paper, cardboard or foil. The amount of paint to be applied depends, for example, on the subject, the type of color, the amount of the color pigments contained therein or the personal taste of the client. In order to minimize waste, ie non-salable copies, and to maximize the profitability of the printing press, the aim of each print job is to reach the desired quantity of ink on the printed copy as quickly as possible and to keep it constant during further operation. These are the Operator various possibilities of intervention in the inking unit of the machine available.

The inking unit of a printing press is based on a paint container in which the printing ink is stored. From this container, the ink is typically taken with a slowly rotating roller, the ink ductor. The ink layer thickness on the ductor is determined by adjusting elements, the color knives. The opening of the colorimeters may typically be zonal, i. be set differently over the width of the substrate. This takes into account the different color requirements of the subjects across the width.

Depending on the type of construction, it is distinguished film inking and lifting inking, the color of the ink fountain roller with a fixed-pitch rotating roller, the film roll, or with a pendulum-mounted roller, the squeegee, removed. By a variety of other rollers, the color film is then evened out. In order to prevent the formation of streaks, some rollers, the ink drivers, are additionally oscillated transversely to the direction of rotation. Due to the large number of rollers, the color film is reduced in its thickness until it reaches its final thickness. In offset printing, the application of paint to the substrate is typically about 1 μm. Furthermore, the inking unit has the task of storing color and replacing it in the roller mill where color has been removed by the subject.

A possible structure of an inking unit is, for example, in Wolfgang Walenski: "The web offset printing", 1st edition 1995, Fachschriften-Verlag GmbH & Co. KG , Fellbach, discloses.

To adjust the amount of ink, the operator can typically open and close the colorimeters in each color zone or vary the speed of rotation of the ink fountain. It should also be noted that through the use of Water in wet offset, the color density is also slightly reduced because the ink is diluted with fountain solution.

Since manually adjusting the color density, especially in the case of very irregular subjects, is very complicated and difficult, and because it then takes a very long time to print good copies, devices for automatically controlling the color density are known in the prior art. FIG. 1 shows such a control loop. To control the color density, an achieved actual density 14 with sensors or high-resolution cameras in control fields or in the image is measured at the end of a printing process 16 and compared with a desired density 11. A calculated density difference 12 is then used as input to a controller 15. The controller 15 generates actuating signals 13, typically values for the opening of the colorimeters, and thus intervenes in the printing process 16. The document DE 698 10 385 discloses a prior art PID controller as a typical implementation for such a controller.

This loop works well for common area coverage during running production. FIG. 2 shows qualitatively a typical, regulated density progression 21. After the start of the machine, also referred to as the start-up phase, a tolerance band of the color density is reached after N ₂₁ copies and good copies are printed. The specimens outside the tolerance band around the target density are not salable as waste.

However, such prior art control systems have some disadvantages.

During setup of the machine, ie during the determination of suitable manipulated variables for achieving the desired optical density, measurement of the optical density is typically not possible or only very late because a minimum density on the paper is required for measuring. Only after reaching the Minimum density can be detected by the sensor, a trigger mark or a point in the image for evaluation. As long as the minimum density is not reached, no regulation is possible due to the missing actual value. This is in FIG. 1 represented by the switch 17.

At very low surface coverage only very little color is taken from the inking unit. Depending on the number of rollers in the inking unit and the amount of ink stored with them, the inking unit reacts very slowly to changes in the setting of the ink zones or the speed of the ductor. In unregulated operation, a density curve 22 then increases accordingly FIG. 2 only very slowly. It results in a very high rate of waste, whereby the efficiency of the machine is significantly reduced.

Furthermore, in controlled operation, the simple PID controller can lead to a strong overdriving of the color density, since very large control signals are generated in the controller, but the system responds only very sluggishly. Because of the very large control signals, the control intervention results in color densities after a certain time, which are far above the desired color densities. The controller now starts to counter and the process continues in the reverse direction with a renewed understeer. FIG. 2 shows the typical regulated density profile at low area coverage with curve 23. Typically, at very low area coverage despite intervention of the controller no stationary operating point of the obtained color density. Rather, a manual intervention of the operating personnel is required in the prior art at very low surface coverage.

It is also possible in modern printing presses to influence the color flow through the group of rollers at defined points by pivoting and thus reducing the waste. FIG. 3 shows this with the example of an inking unit of a web offset press. In the Anstellsequenz is between the pivoting of a film roll 32 to a ductor 31, the pivoting of applicator rollers 33 to a plate cylinder 34 and the pressure-on-places of rubber cylinders 35 to the substrate web 36. Simple color density control systems after FIG. 1 do not take advantage of the extended possibility to intervene in the color flow.

In order to circumvent the known problems, various set-up procedures have additionally been developed in order to achieve the setpoint density without color density control as quickly as possible when starting the machine. In all cases, the manipulated variables (ink fountain opening, ink duct speed and setting sequence, in part also the machine speed) are preset statically or quasi-statically. The determination of the start sequence and the setting values is carried out empirically with the aim that the targeted color density is achieved in stationary operation, without further changes to the manipulated variables are required. The documents DE 103 58 172 . DE 698 23 631 . DE 10 2008 034 943 or DE 697 16 515 reveal appropriate procedures.

In document DE 10 2005 013 634 In order to shorten the set-up time, it is proposed to pre-color the entire inking unit across the width with a constant amount of ink, regardless of the image to be printed. An adaptation to the printed image takes place only after an empirically determined time. For pre-inking is in document EP 1 232 862 proposed to open the zones indirectly proportional to the area coverage during a defined period of time. Only then is the return to the conventional preset values. The time periods of the individual steps are fixed. It has turned out that the dynamics are not sufficient, especially with high surface coverage. In order to determine the presetting parameters as accurately as possible, the respective settings are saved on the basis of the past productions and used for the next setup process. An adaptation of the startup sequence does not take place.

The DE 698 10 385 T2 discloses a method for color control in a printing press, in which first a color density is measured in the printed image, wherein then the measured color density is converted into a color layer thickness value to ensure the linearity of the control parameters using a calculation algorithm. The control of the color density then takes place with the converted value.

The DE 101 05 990 A1 teaches a method for controlling parameters of a color layer at a selected location in the printing unit of a printing press, wherein the printing machine at least one color source for generating the ink layer on a transport device, where the Dosiergrößen for controlling the Farbauftrages on the transport device are adjustable in zones. For each zone of the color layer, nominal values of parameters are determined on the basis of measured image data.

All of these solutions have the disadvantage that the timing of the default setting and the Anstellsequenz is fixed. An optimal in all applications waste paper can not be achieved with such an approach.

The document EP 1 671 789 discloses a control method for an inking unit in which a color density measured in peripheral areas is modified by means of a model of the respective inking unit or on the basis of data of the subject. This method only works, provided that valid measured values are available, and is therefore not suitable for the Anstellsequenz when commissioning an inking unit.
It is an object of the invention to provide a method for controlling at least one parameter on which the ink density in the printing machine depends, during startup and also during the printing run. Furthermore, it is an object of the invention to provide a printing machine with an inking unit having a control unit for carrying out such a method.
With regard to the method, this is achieved according to the invention by a method according to claim 1. With regard to the printing machine, this is achieved by an offset printing machine according to claim 13. Advantageous developments can be taken, for example, the respective subclaims.

The invention relates to a method for controlling at least one control parameter from a number of parameters of an inking unit of an offset printing machine wherein the parameters of the inking unit, which may also be control parameters, include an opening of a color meter or a rotational speed of a Farbduktors, based on at least the control parameter is calculated by means of an inking model, a calculated value of a color density on a substrate to be printed by the printing press, and instead of an actual value of the calculated value is used as an input variable for controlling, wherein at least temporarily the calculated value based solely on a number of parameters of the inking unit is calculated, wherein a control parameter is the rotational speed of a Farbduktors and / or the opening of at least one colorimeter. It should be understood that a number within the scope of this application is understood to mean a value of one or more. It should also be understood that the calculation of a value closely corresponding to the color density, for example, the color thickness, is considered to be equivalent to the calculation of the color density. Furthermore, it should also be understood that a parameter is understood to mean a parameter which is regulated by a controller. In addition, it should be understood that the term exclusively based on a number of parameters of the inking unit is understood to mean, in particular, that no measured value of a color density or a similar size is used as the input variable of the model. Nevertheless, constants, formulas, equations, rules of calculation, and the like may be used in the model. The method according to the invention was considered not executable before the priority date of this application. This is because to control an inking unit, a calculated color density value must be available in real time. However, all models known prior to the priority date are based on systems theory models that are based on the known laws of continuum mechanics and are based, for example, on the conservation of mass. To create such a model, appropriate system states for the ink layer thicknesses must be introduced.
The simplest models arise when the investigation is limited to a steady-state operation. Along the surface of a roller then the ink layer thickness between the contact points to adjacent rollers assumed to be constant. At the contact points themselves, paint is either added or removed. Therefore, to create such a model, for each contact point between two adjacent rolls, the mass balance of the incoming and outgoing color streams must be established.

FIG. 4 shows a section of an inking unit of a web-fed printing machine with registered states of the ink layer thickness. For example, the ink layer on a film roll 41 before contact with a ductor 40 has the thickness t ₁ (1), and after contact with the ductor 40 has the thickness t ₂ (2). Part of this ink layer is by cleavage to a transfer roller 42 from. The transfer roller 42 before contact with a film roll on a color layer of thickness t ₄ (4), after contact a color layer of thickness t ₃ (3). The transfer roller 42 in turn is a part of their color to a roller 43 from.

For example, set it accordingly FIG. 4 the mass balance of the ink entering and leaving the contact point between the roller 41 and the roller 42, the ink layer thickness t entering the gap amounts _to (51): $${\mathrm{t}}_{\mathrm{to}}={\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+{\mathrm{<figure-callout\; id="4"\; label="t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_4$$

Likewise, the ink layer thickness t _ab (52) emerging from the nip is calculated to: $${\mathrm{t}}_{\mathrm{from}}={\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_3+{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="imgf0008.png"\; state="\{\{state\}\}">t</figure-callout>}}_1$$

Since no ink can be stored in the nip, the supplied ink layer thickness t _must correspond _to (51) the discharged ink layer thickness t _ab (52): $${\mathrm{t}}_{\mathrm{to}}={\mathrm{t}}_{\mathrm{from}}$$

The ratio of the two outgoing ink layer thicknesses t ₃ (3) and t ₁ (1) is usually described by a cleavage factor k. In the direction of the cylinder to be inked, ie in FIG. 4 As shown in the example of roller 41 on roller 42, the kth component of the incoming ink nip layer thickness is transferred: $${\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_3=\mathrm{k}\cdot \left({\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+{\mathrm{<figure-callout\; id="4"\; label="t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_4\right)$$

This leaves the ink layer thickness on the roller 41: $${\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="imgf0008.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=\left(1-\mathrm{<figure-callout\; id="2"\; label="k\; \cdot \; t"\; filenames="imgf0004.png"\; state="\{\{state\}\}">k\; </figure-callout>},\right)\cdot \left({\mathrm{t}}_{}\right)\left({\mathrm{}}_2+{\mathrm{<figure-callout\; id="4"\; label="t"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_4\right)$$

Usually, the clipping numbers k are assumed to be close to 0.5. Alternatively, it is possible to determine the cleavage digit k by parameter identification methods from known measurement results.

For the transfer of the ink from the forme cylinder to the printing cylinder and in particular from the printing cylinder to the substrate, various approaches are known in the prior art which deviate from Equation 4, e.g. the division law of Walker-Fetsko.

The further procedure in the model production known from the prior art is outlined below only briefly:
If the balances of the ink layer thicknesses according to Equation 4 and Equation 5 are set up for all contact points between adjacent rolls, it is possible to determine a system of equations which can be resolved according to the required ink layer thicknesses. Thus, the layer thicknesses achieved in stationary operation can be calculated. The document EP 0 881 076 discloses such a procedure for determining suitable preset data. In addition, in this document, a relationship between the color density D and the ink layer thickness t on the substrate is assumed.

For a time-dependent, dynamic simulation, which is practically indispensable for a model-based control model, is the sketched and in EP 0 881 076 but not enough. Since, in the transient case, the layer thicknesses on the surface of a roller also change over time between two contact points, additional states must be taken into account here.

FIG. 5 shows, for example, the extended for a time-dependent simulation, from FIG. 4 already known system model. In this example, the ink layer thickness t ₃ (3) must be split into a paint layer thickness (3.1) immediately after contact between roller 41 and roller 42 and into a paint layer thickness (3.2) immediately before contact between roller 42 and roller 43. Analogously, the remaining ink layer thicknesses are split into one part after the last contact with an adjacent roller and into one part before contact with the next adjacent roller. Along a roll surface, a point seen later in the direction of rotation assumes the ink layer thickness of a point in front offset by a dead time T.

For example, applies to the roller assembly in FIG. 5 : $${\mathrm{t}}_{3.2}\left(\mathrm{t}\right)={\mathrm{t}}_{3.1}\left(\mathrm{t}-\mathrm{T}\right)$$

The dead time T is dependent on the rotational speed of the roller 42 and the angle between the contact points to the roller 41 and the roller 43rd

If the other system states are also related in relation to each other, sufficient equations are also available for the dynamic simulation in order to transiently determine the ink layer thicknesses over time. For this purpose, a suitable time integration method should be used.

Experiments with such system-theoretical models have shown, however, that their calculation is very time-consuming and even on the fastest process computers not possible in real time. A model-based color density control on the basis of such system-theoretical approaches is therefore not feasible.

In the context of the invention, it has now been recognized that there are models in which a simulation of the inking unit is possible in real time and still provide sufficient accuracy, so that a control based on a calculated value provided by such a model is possible. Accordingly, the control is based on such a calculated value according to the invention.

This results in a number of advantages. For each application, the optimal inking strategy can be determined and carried out. As a result, the waste can be minimized and there are significant cost advantages for the customer and user. Furthermore, the controller structure can be substantially simplified. Since fewer measurement points are required per unit of time, it is possible to resort to simpler and more cost-effective measuring heads with a lower measurement frequency. Furthermore, the systems can be designed to be traversing despite the fact that the target thickness is reached more quickly and the number of measuring heads can be considerably reduced. This results for the machine manufacturer and especially for the customer considerable cost advantages. Another advantage of this procedure is that the color density can be determined at any time, even if, for example, the expression for detecting the actual density is not yet sufficient. Therefore, the proposed method can be used both for starting the machine and for the production printing.

The basis of the control is a simulation model, which calculates the color density process-parallel in real time. Subsequently, a control strategy can be justified on the simulated values with which, for example, it is possible to intervene in the parameters color zone opening, ink ductor speed, dampening duct speed or in the setting sequence. The calculation model can be designed as complex as you like. A limitation results solely from the real-time requirement, i. the simulation of a time step in the model must not take longer than the real time step.

As an inking unit model, an empirical inking model based on a control-technical transfer element is preferably used. As recognized by the present inventors, this meets the requirements that it be sufficiently accurate and yet computationally manageable.

The inking unit model preferably also has a deadtime element which reflects the transit time of the ink from a color container from changing the control parameter until reaching the first contact point to the film roller (32) or to the squeegee roller. Thus, the delay due to the propagation of color in the inking unit at finite speed can be accommodated.

Further preferably, the inking model further comprises a dead time element reflecting the transit time of a print copy between printing and measurement. Thus, the running time of the substrate from the place where it is printed, up to any sensor or camera bill be taken into account.

According to one embodiment, the control-technical transmission element is a PT ₁ element. It has been shown that this already gives good results for a regulation. According to an alternative embodiment, the control-technical transfer member is a PT ₂ member. This provides even better results in the application because additional system inertia is taken into account. Such elements take into account the finite response time of the color density on the substrate to a change of the control parameter, as far as it also occurs in the theoretical case of the negligibility of the already mentioned dead times.

Particularly preferably, during a start-up phase of the inking unit, the calculated value is calculated exclusively based on a number of parameters of the inking unit, at least until a measured value of the color density on the substrate can be measured. This is typically the case when the color density is large enough to be accessible to measurement by a sensor or camera used. As a start-up phase, the time required to obtain a color density within a tolerance band can be assumed, as already described with reference to FIG FIG. 2 has been described. Thus, the control according to the invention can be used precisely in the time range in which, in the absence of useable measured values, regulation has hitherto been impossible, which in turn can significantly reduce the waste rate.

According to one embodiment of the invention, after a start-up period, preferably after each calculation of a multiplicity of calculated values, for example approximately every 30 seconds, a measured value of the color density on the substrate is measured and the inking model is adjusted based on the measured value. This can be done, for example, by correcting the calculated value by an additive value in order to adapt the calculated value to the measured value at the time of the measurement. Alternatively it can be more complex in the Injection model are intervened. The measurement is preferably carried out in a region downstream of the inking unit. By comparing with a measured value, the accuracy of the control can be improved. Compared to a measurement-based control, however, considerably less measuring points are sufficient in the present case, so that a considerably less complicated measuring technique is sufficient. By way of example, a sensor in the region downstream of the inking unit can traverse the printing web in the transverse direction and thus be used for measuring at several locations. Also, the use of a less fast and thus cheaper sensor is sufficient. Such a sensor is for example in FIG. 3 shown by reference numeral 37.

According to a development, a film or lifting roller of the inking unit is pivoted to the ink ductor when the calculated value exceeds a predetermined limit. Likewise, an applicator roll can be pivoted to a plate cylinder when the calculated value exceeds a predetermined limit. In addition, a blanket cylinder can be pivoted to the substrate if the calculated value exceeds a predetermined limit. Thus, the Anstellsequenz can be controlled based on the calculated value, which allows faster and with less waste startup.

The invention further relates to an offset printing machine with an inking unit, which has at least one ink fountain roller and an associated colorimeter, wherein at least one rotational speed of the ink fountain roller and / or an opening of the colorimeter is adjustable as a control parameter. For the inking unit, a control unit with a regulator and an inking unit model, as well as a sensor traversing or traversing the printing web in a region downstream of the inking unit, are preferably provided. These are designed to carry out a control method according to the invention in order to set at least one rotational speed of the ink ductor and / or an opening of the colorimeter as a control parameter.

The printing machine according to the invention makes use of the already mentioned advantages of the method according to the invention.

Figur 1

zeigt eine Reglerstruktur gemäß dem Stand der Technik.

Figur 2

zeigt verschiedene Verläufe der Farbdichte mit zunehmender Anzahl an Exemplaren.

Figur 3

zeigt ein Modell eines Farbwerks.

Figur 4

zeigt einen Ausschnitt aus einem Modell eines Farbwerks.

Figur 5

zeigt einen abgewandelten Ausschnitt aus einem Modell eines Farbwerks.

Figur 6

zeigt eine erfindungsgemäße Reglerstruktur.

Figuren 7 bis 10

zeigen Ausführungen von Simulationsmodellen.

Figur 11

zeigt eine Anstellsequenz.

Hereinafter, an embodiment of a controller structure will be described with various modifications. Reference is made to the accompanying figures, wherein it should be noted that on the FIGS. 1 to 5 previously referred to:

FIG. 1

shows a controller structure according to the prior art.

FIG. 2

shows different gradients of color density with increasing number of copies.

FIG. 3

shows a model of an inking unit.

FIG. 4

shows a section of a model of an inking unit.

FIG. 5

shows a modified section of a model of an inking unit.

FIG. 6

shows a controller structure according to the invention.

FIGS. 7 to 10

show versions of simulation models.

FIG. 11

shows a pickup sequence.

FIG. 6 shows the schematic structure of a controller structure according to the invention. Compared to a controller structure according to the prior art, as in FIG. 1 this is supplemented by a simulation model 18. The simulation model 18 makes use of the available process data 13, ie the parameter of the inking unit. These are, for example, the already mentioned, typical parameters opening of one or more colorimeters, rotational speed of a Farbduktors, rotational speed of a Feuchtduktors or the Anstellzustand of Film roller or squeegee roller, applicator roller or blanket cylinder. In addition, if required, any further process variables, such as temperatures, properties of paper or ink, dampening parameters, properties of printing blankets or other printing materials, etc., can additionally be made available to the simulation model. From this data, the simulation model calculates a calculated color density 20 as an estimate of the actual color density. With a high model quality, the simulated and the real values are approximately the same. Therefore, a conventional control loop can be constructed, but the calculated values are made available for comparison with the setpoint value 11.

For the starting process, in addition to the calculated color density 20 in the simulation model 18, it can additionally be calculated when the optimal times for advancing the setting sequence are reached. This information 19 is preferably transferred directly to the controller 15.

During printing, a discrepancy between actual and calculated color density can occur over a longer period of time. It can therefore be measured from time to time with a simple measuring device, the actual color density and corrected the model according to the measured value. Since the measurement data are required only at longer time intervals, during which typically a multiplicity of calculated values is calculated, simpler sensor systems or camera systems with a lower temporal resolution can be used. However, the use of the simulation model is particularly advantageous, in particular when starting up the inking unit, because there are still no valid measured values available.

As a simulation model 18, an empirical inking model based on a single control-technical transmission element and additional dead-time elements is used in the present case.

The control technical transmission element is presently a PT ₁ member. This describes the following relationship between the volume flow v 'of the ink flowing into the inking unit and the color density D achieved on the substrate: $$\mathrm{TD}\text{'}\left(\mathrm{t}\right)+\mathrm{D}\left(\mathrm{t}\right)=\mathrm{K\; v}\text{'}\left(\mathrm{t}\right)$$

T is the time constant of the PT ₁ element, K is the amplification factor. Both quantities can be easily identified from measurement data. Alternatively, by the PT ₁ member other sizes, such as the ink layer thickness on the substrate instead of the density or the ink layer thickness on the ductor instead of the volume flow, be set in proportion and these sizes are converted accordingly by an additional block.

In the present case is appropriate FIG. 7 for the empirical inking model in a first embodiment in front of the PT ₁ member 18.2 additionally provided a deadtime element 18.1. This records the time from the location of the colorimeter or from changing the speed of the ink fountain roller to reaching the first contact point either to the film roll or to the squeegee roll. Because of the slowly rotating ductor, it is advantageous if this dead time is not neglected in the calculation model.

For machines with a longer transport distance between printing unit and the location of the color density is appropriate FIG. 8 to take account of the time shift between pressure and measurement in an alternative embodiment after the PT ₁ -Glied 18.2 an additional deadtime 18.3 required.

Both versions may also correspond to a third embodiment FIG. 9 be combined with a PT ₁ -Glied 18.2 and two deadtime elements 18.1, 18.3.

Typically, about 10 to 40 parameters are required to accurately describe the dynamic behavior of an inking unit, and even more for large inking units. Experiments by the inventors have shown that nevertheless the behavior of the inking unit can already be approximated very well with a PT ₁ element.

In order to approximate the real behavior even better, instead of the PT ₁ member alternatively also a PT ₂ member can be used. This describes the following relationship between the volume flow of ink v 'flowing in the inking unit and the color density D achieved on the substrate: $${\mathrm{T}}^{2}D"\left(\mathrm{t}\right)+2\mathrm{d\; TD}\text{'}\left(\mathrm{t}\right)+\mathrm{D}\left(\mathrm{t}\right)=\mathrm{K\; v}\text{'}\left(\mathrm{t}\right)$$

As an additional model parameter this contains the damping d. Again, the state variables D (t) and v '(t) may be represented by equivalent quantities, e.g. Color layer thicknesses to be replaced.

FIG. 10 shows the simulation model 18 with a PT ₂ -Glied 18.2 and 2 dead time elements 18.1, 18.3 analogous to FIG. 9 , It should be noted that the two versions after FIG. 7 and FIG. 8 be combined with a PT ₂ member instead of a PT ₁ member.

In contrast to the classic controller, the model-based approach can not only influence the classic parameters such as the opening of the colorimeter or the rotational speed of a color ductor. Rather, it is It is also possible to intervene directly on the basis of known conditions in the Anstellsequenz the machine.

It can therefore be defined depending on the target density limit values at which the ink layer thickness is in the appropriate ratio to the desired thickness or the color density in the appropriate ratio to the desired density on the respective rollers and in which then a setting is triggered. Ideally, the limits are within a range between 50% and 95% of the calculated and attainable nominal thicknesses or nominal densities.

FIG. 11 shows an example Anstellsequenz invention, as is possible with a model-based control. Qualitatively represented over time is the ink layer amount on the ink fountain roller (reference numeral 81), on the applicator rollers (reference numeral 82), on the forme cylinder (reference numeral 83) and on the substrate (reference numeral 84). The limit values for the pivoting of the film or lifting roller (reference numeral 61), for the pivoting of the applicator rollers on the plate cylinder (reference numeral 62) as well as for pressure-on (reference numeral 63) are also shown. They are in the above range between 50% and 95% of the expected target color thicknesses on the respective rolls. In the time domain 71 only color is on the ink fountain roller, in the time domain 72 also in the roller mill. In the time domain 73, the printing form is also colored. Only in the time domain 74 is ink applied to the substrate.

In contrast to the usual time-controlled setting sequence, the pressure on the substrate is delayed until the calculated quantity of ink on the forme cylinder can be expected to reach the setpoint density or at least its tolerance band. This time delay can be calculated separately for all color zones. With different ink acceptance in different color zones then the target density is reached in all zones at the same time. With a sufficient model quality is thus possible to set up the printing press without waste due to insufficient color density.

Claims (13)

1. A method for controlling at least one control parameter from a number of parameters (13) of an inking unit (16) of an offset printing press, wherein the parameters of the inking unit, which can also be control parameters, comprise an opening of an ink blade or a rotational speed of an ink fountain roller, wherein, based on at least the control parameter, a calculated value (20) of an ink density on a substrate (36), which is to be printed by the printing press, is calculated by means of an inking unit model (18), and, instead of an actual value (14), the calculated value (20) is used as input variable for controlling purposes, wherein the calculated value (20) is at least temporarily calculated exclusively based on a number of parameters (13) of the inking unit (16), wherein
   the rotational speed of an ink fountain roller (31) and/or
   the opening of at least one ink blade is a control parameter.
2. The method according to claim 1, characterized in that an empirical inking unit model (18) based on a control-related transfer element (18.2) is used as inking unit model (18).
3. The method according to claim 2, characterized in that the inking unit model (18) further has a dead time element (18.1), which reflects the runtime of the ink out of an ink container for changing the control parameter until reaching the first contact point with a film roller (32) or with a ductor roller.
4. The method according to one of claims 2 or 3, characterized in that the inking unit model (18) further has a dead time element (18.3), which reflects the runtime of a print copy between print and measurement.
5. The method according to one of claims 2 to 3, characterized in that the control-related transfer element (18.2) is a PT₁ element.
6. The method according to one of claims 2 to 4, characterized in that the control-related transfer element (18.2) is a PT₂ element.
7. The method according to one of the preceding claims, characterized in that the calculated value (20) is calculated exclusively on the basis of a number of parameters (13) of the inking unit (16) during a start-up phase of the inking unit (16), namely at least until a measurement value (14) of the ink density on the substrate (36) can be measured.
8. The method according to one of the preceding claims, characterized in that a measurement value (14) of the ink density on the substrate (36) is measured periodically after a start-up phase, preferably after respective calculation of a plurality of calculated values, in a region downstream from the inking unit, and the inking unit model (18) is adjusted based on the measurement value (14).
9. The method according to claim 8, characterized in that a sensor (37), which traverses the printing web in the transverse direction in the region downstream from the inking unit is used to measure measurement values at different points transversely to the direction of movement of the substrate (36).
10. The method according to one of the preceding claims, characterized in that a film or ductor roller (32) of the inking unit (16) is engaged with an ink fountain roller (31), when the calculated value (14) exceeds a predetermined threshold value (61).
11. The method according to one of the preceding claims, characterized in that an application roller (33) is engaged with a plate cylinder (34), when the calculated value (14) exceeds a predetermined threshold value (62).
12. The method according to one of the preceding claims, characterized in that a blanket cylinder (35) is engaged with the substrate (36), when the calculated value exceeds a predetermined threshold value (63).
13. An offset printing press comprising an inking unit, which has at least one ink fountain roller (31) and an assigned ink blade, wherein at least one rotational speed of the ink fountain roller (31) and/or an opening of the ink blade can be set as control parameter, characterized in that, for the inking unit, a control unit (15, 18) comprising a controller (15) and an inking unit model (18), and preferably a sensor (37), which traverses or does not traverse the printing web in the transverse direction in a region downstream from the inking unit, are further provided, which are embodied to carry out a control method according to one of claims 1 to 12, in order to set at least one rotational speed of the ink fountain roller (31) and/or an opening of the ink blade as control parameter.

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