EP3715136A1 - Method for operating a digital sheet printer, control device and sheet printer - Google Patents

Abstract

A method for operating a digital web printing machine (100), comprising: selecting (10) a frequency (F) for driving a digital print head (210) at the frequency (F) for outputting printing ink (212) onto a printing web (240), determining ( 20) a target conveying speed (vs) for conveying the print web (240) as a function of the selected frequency (F) and print data (D), control (30) of a motor (M1) driving a first roller (220) and / or a motor (M2) driving a second roller (230) as a function of the target conveying speed (vs) in such a way that the printing web (240) between the first roller (220) and the second roller (230) at the target conveying speed (vs ) is funded, and control (40) the digital print head (210) with the selected frequency (F) and depending on the print data (D). This method has the advantage that the digital print head of the web printing machine is controlled with a selected, fixed frequency, why a com plex dynamic control of the digital print head as well as an associated measuring and control system can be omitted.

Description

The present invention relates to a method for operating a digital web printing machine, a control device for operating a digital web printing machine and a web printing machine with such a control device.

In digital web printing machines, to achieve a correct print result, it is necessary to precisely coordinate the control of the print head and the conveyance of the print web through the print area. In known digital web printing machines, this control takes place, for example, in such a way that an optical measuring device is arranged in front of the print head, which measures the current conveying speed of the print web. The frequency with which the print head outputs printing ink is adapted as a function of this conveying speed. Since the conveying speed depends on various factors and, in particular, can be variable over time, the frequency is dynamically adjusted. Errors in the detection of the conveying speed are reflected directly in a faulty print image and / or poor print quality. In order to achieve the desired print quality, the measuring and control system must therefore work very precisely, which is why it is designed in a complex manner.

Against this background, one object of the present invention is to propose an improved method for operating a digital web printing machine.

Accordingly, a method for operating a digital web printing machine is proposed which comprises the following steps. In a first step, a frequency for driving a digital print head with the frequency for outputting printing ink onto a printing web is selected. In In a second step, a target conveying speed for conveying the printing web is determined as a function of the selected frequency and of print data. In a third step, a motor driving a first roller and / or a motor driving a second roller is controlled as a function of the target conveying speed in such a way that the print web between the first roller and the second roller, in particular directly under the digital print head, with the target Conveyor speed is promoted. In a fourth step, the digital print head is controlled with the selected frequency and depending on the print data.

This method has the advantage that the digital print head of the web printing machine is controlled with a selected, fixed frequency, which is why complex dynamic control of the digital print head and an associated measuring and control system can be dispensed with. A web printing machine operated with this method can therefore have a less complex structure and thus be cheaper to manufacture. By regulating the conveying speed of the print web as a function of the frequency, the print result, in particular a print image that matches the print data, is controlled.

In this method, a causal chain is reversed to that of the conventional methods. In the prior art, the printing web is conveyed, the conveying speed is measured and the frequency of the print head is varied as a function of the measured conveying speed. This can lead to a cascade of errors, with measurement errors and control errors increasing so that the print result becomes unusable. This can be avoided with the proposed method. In the present case, the frequency of the print head is specified and the conveying speed of the print web is adjusted accordingly. This is possible because a web conveyor device for conveying the printing web, here for example the first roller and the second roller with the associated control device, is able to convey the print web very consistently and precisely.

The digital print head is arranged in particular above the print web between the first and the second roller. The target conveying speed preferably relates to the position of the print web exactly below the print head. This achieves the target conveying speed for the print web directly under the print head, so that the print result matches the print data.

The digital print head, hereinafter also simply print head, comprises, for example, a number of print nozzles. The number determines in particular a maximum print resolution of the print head. Furthermore, the maximum print resolution is dependent on how large a minimum amount of printing ink is that the print head with a print nozzle can deliver in one cycle. The term clock is understood here to mean the length of a period at the selected frequency. The print resolution is, for example, 9600 DPI, which corresponds to a dot density of 9600 per inch (DPI = dots per inch ). The frequency determines the frequency with which a respective printing nozzle can output printing ink. The amount of printing ink to be output per cycle or per control can be set individually for each nozzle of the print head. Furthermore, the amount can be different and adjustable from cycle to cycle.

In the present case, the printing ink is understood to be the consumable material that is used to generate a print, for example ink or toner. Which material is used as the printing ink depends on the printing technique used.

The print data include the motif to be printed, for example as a machine-readable data record. The motif to be printed is available as a digital image data set, for example as a vector graphic or as a bitmap, which is also referred to below as a template. For example, this template is converted or translated into the print data by means of a printer driver, with a maximum resolution of the print head being taken into account in particular. The print data include, in particular, a resolution with which the original is to be reproduced. With a known frequency and available print data, the target conveying speed at which the print web is to be conveyed under the print head can be determined.

For example, the print data include two lines that are 1 cm apart and are to be printed perpendicular to the conveying direction of the print web. With a known printhead resolution and a predetermined frequency of the printhead, the target conveying speed results, for example, as the product of printhead resolution and frequency. With a resolution of 10,000 points per cm and a frequency of 10 kHz, a target conveying speed of 1 cm / s or 0.6 m / min results, for example.

The setpoint conveying speed determined in this way as a function of the selected frequency is set by a corresponding regulation of the motors which drive the first roller and / or the second roller conveying the printing web. This means that the print web is conveyed at the target conveying speed, so that correct printing in accordance with the print template is guaranteed.

A peripheral speed of the respective roller can be derived from a rotational frequency of the motor driving the respective roller, a gear ratio and the diameter of the respective roller. With a thin printing material, for example up to 0.5 mm, and when there is no slip between the printing web and a respective roller, the peripheral speed of the respective roller corresponds to the conveying speed of the printing web at the roller. The printing web is conveyed with a certain tensile stress, for example. This can lead to a stretching of the printing web, which is why a conveying speed on the first roller and on the second roller can be different and also between the rollers can assume different values, which must be taken into account in the regulation.

If the print web is conveyed at the target conveying speed and the print head is controlled according to the print data and with the frequency, the print result achieved, the printout, will correspond to the original. In particular, the dimensions of the printout and a color intensity will correspond to those of the original.

According to one embodiment of the method, a conveying parameter of the first roller and / or the second roller is detected and a conveying speed of the printing web is determined as a function of the conveying parameter. The first motor and / or the second motor is regulated as a function of the determined conveying speed, so that the conveying speed corresponds to the target conveying speed.

This embodiment has the advantage that an actual conveying speed is determined and used to regulate the motors for conveying the printing web at the target conveying speed.

A conveying parameter includes, for example, a rotational frequency, a torque, a diameter, the wrapping of the respective roller with the printing web and / or a coefficient of friction between the respective roller and the printing web. The wrapping indicates, for example, which portion of the respective roller is wrapped by the printing web. The wrap can be specified as an angle, for example. The coefficient of friction relates in particular to a particular combination of a roller with a specific material.

These parameters can affect a conveying characteristic, in particular the conveying speed. The speed or the torque of the respective roller can be deduced from the speed or the torque of the respective motor. A transfer function is preferably used for this known, which takes into account, for example, a gear ratio and / or a loss value.

The determined conveying speed can include a first conveying speed of the printing web on the first roller, a second conveying speed of the printing web on the second roller and / or a conveying speed at one or more points between the two rollers.

According to a further embodiment of the method, a printing web parameter of the printing web is detected and the first motor and / or the second motor is regulated as a function of the detected printing web parameter.

This embodiment has the advantage that parameters of the printing web that can affect a conveying characteristic, in particular a conveying speed, are taken into account.

Print web parameters include in particular material parameters such as a modulus of elasticity and / or a behavior of the print material during printing. Furthermore, geometric parameters such as a thickness of the printing material and / or a width of the printing web can be taken into account.

For example, the thickness of the printing material can be variable, which can have a direct effect on the conveying speed. In this embodiment, for example, the material thickness is recorded and the conveying speed is regulated accordingly as a function of the recorded thickness.

According to a further embodiment of the method, a register mark is periodically printed onto the printing web by the digital print head. A distance between two successively printed register marks on the printing web is then detected and the first motor and / or the second motor is regulated as a function of the detected distance.

This embodiment has the advantage that the printing result achieved can be checked directly by means of the register marks and the regulation of the roller drive, that is to say of the first motor and / or the second motor, can be adapted accordingly.

Periodic printing of register marks is preferably understood to mean that there is a fixed time interval between two register marks printed one after the other, for example one second. The actual conveying speed results from the detected distance between two register marks printed one after the other, for example as the quotient of the distance divided by the time interval. For example, a specific register mark sensor can be provided, which is arranged after the print head in the conveying direction.

In addition to the distance, a color saturation or color intensity of the register marks can also be detected, for example. If the saturation is too low, the amount of printing ink output by a printing nozzle per cycle can be adapted, for example.

According to a further embodiment of the method, image data are generated as a function of a print motif printed on the print web by the digital print head. The image data are compared with the print data. The first motor and / or the second motor are regulated as a function of a result of the comparison.

This embodiment is advantageous because the print result is at least partially, advantageously also as a whole, recorded and checked by means of the comparison. For example, a digital image sensor such as a CCD camera is arranged after the print head in the conveying direction and records the image data. Comparison is understood to mean, in particular, that, for example, a dimension of a printed graphic with the Dimension of the graphic in the print data is compared. For example, a difference is formed between the recorded value and the theoretical value. If the result of the difference is positive, then the printed graphic is larger than the original (conveyor speed too high) and if the difference is negative, then the printed graphic is smaller than the original (conveyor speed too low). An incorrect conveying speed therefore leads to an expansion or compression of a graphic in comparison with the original, which in this embodiment can be corrected by adjusting the conveying speed.

Furthermore, in this embodiment too, a color saturation or color intensity of the printed graphic can be compared with the original and the output quantity of printing ink of a printing nozzle per cycle can be adapted accordingly.

According to a further embodiment of the method, an output quantity of the printing ink for a printing nozzle of the digital print head is set in a period of the selected frequency as a function of the print data and the set conveying speed.

This embodiment is advantageous since it allows a maximum color intensity or print density to be adapted. Furthermore, shades or color gradations can also be produced in the same way at different conveying speeds.

According to a second aspect, a control device for operating a digital web printing machine is proposed. The control device comprises a setting unit for setting a selected frequency, a determining unit for determining a target conveying speed of a printing web as a function of the frequency and printing data, a control unit for regulating a first motor driving a first roller and / or a second motor driving a second roller for setting the conveyor speed the print web running between the first roller and the second roller as a function of the determined target conveying speed, and a control unit for controlling a digital print head for outputting printing ink at the frequency and as a function of the print data.

This control device is advantageously set up for operating a digital web printing machine according to the method according to the first aspect, from which the above-mentioned advantages result. The embodiments and features explained for the method apply accordingly to the control device.

The control device is at least partially implemented in terms of hardware, but can at least partially also be implemented in terms of software. The control device can be designed, for example, as a computer or as a microprocessor. Parts implemented using software technology are designed, for example, as a computer program product, as a function, as a routine, as part of a program code or as an executable object.

The setting unit preferably comprises a clock generator which is set up to output the selected frequency.

According to one embodiment of the control device, it comprises a first detection unit for detecting a conveying parameter of the first roller and / or the second roller, the determination unit being set up to determine the conveying speed as a function of the detected operating parameter. The control unit is set up to control the first motor and / or the second motor as a function of the determined conveying speed.

The control of the conveying speed thus advantageously takes place as a function of the conveying speed derived from the conveying parameters.

A conveying parameter includes, for example, a rotational frequency, a torque, a diameter, the wrapping of the respective roller with the printing web and / or a coefficient of friction between the respective roller and the printing web. The wrapping indicates, for example, which portion of the respective roller is wrapped by the printing web. The wrap can be specified as an angle, for example. The coefficient of friction relates in particular to a particular combination of a roller with a specific material.

These parameters can affect a conveying characteristic, in particular the conveying speed. The speed or the torque of the respective roller can be deduced from the speed or the torque of the respective motor. For this purpose, a transfer function is preferably known that takes into account, for example, a gear ratio and / or a loss value.

The determined conveying speed can include a first conveying speed of the printing web on the first roller, a second conveying speed of the printing web on the second roller and / or a conveying speed at one or more points between the two rollers.

According to a further embodiment of the control device, it comprises a second detection unit for detecting a print path parameter of the print web. The determination unit is set up to determine the conveying speed as a function of the detected print web parameter. The control unit is set up to control the first motor and / or the second motor as a function of the determined conveying speed.

The control of the conveying speed thus advantageously takes place as a function of the conveying speed derived from the printing path parameters.

Print web parameters include in particular material parameters such as a modulus of elasticity and / or a behavior of the print material during printing. Furthermore, geometric parameters such as a thickness of the printing material and / or a width of the printing web can be taken into account.

For example, the thickness of the printing material can be variable, which has a direct effect on the conveying speed. In this embodiment, for example, the material thickness is recorded and the conveyor speed is regulated in accordance with the recorded thickness.

According to a further embodiment of the control device, it comprises a third acquisition unit for acquiring sensor data from the printed print web and a correction unit for determining a correction value as a function of the print data and the acquired sensor data. The determination unit is set up to determine a corrected conveying speed as a function of the correction value and the control unit is set up to control the first motor driving the first roller and / or the second motor driving the second roller to set the corrected conveying speed.

This embodiment is advantageous because it enables errors in a print image, which may arise, for example, due to incorrect assumptions and / or inaccuracies in a physical model of the web printing machine that is used to determine the conveying speed, to be corrected directly on the basis of an actually achieved print result.

The third detection unit comprises, for example, an optical sensor, such as an image sensor, which detects the printed print motif and converts it into image data. The correction unit compares the captured image data with the print data. The correction unit is part of the determination unit, for example. In particular, the correction unit determines whether the image data matches the print data with regard to the dimensions of graphics and the color intensities or whether there are deviations. The type of deviation is also determined, for example whether there is compression or expansion. A corresponding correction value is determined and output. The correction value is used to determine a corrected conveying speed, for example by addition or multiplication.

According to a third aspect, a web printing machine is proposed with a printing web running between a driven first roller and a driven second roller. A digital print head for outputting printing ink onto the printing web is arranged between the first roller and the second roller above the printing web. Furthermore, the web printing machine comprises a control device according to the second aspect, which is set up to operate the web printing machine.

This web printing machine can advantageously be operated by means of the control device according to the method according to the first aspect, from which the above-mentioned advantages result. The embodiments and features explained for the method apply accordingly to the web printing machine.

According to one embodiment of the web printing machine, it includes a means for detecting a conveying parameter of the first roller and / or the second roller. The control device is set up to operate the printing press as a function of the detected conveying parameter.

The means comprises, in particular, a sensor which, for example, detects a circumferential speed of the respective roller and / or a torque on the roller surface of the respective roller as the conveying parameter. The control device takes into account the conveying parameters, in particular for regulating the motors that drive the respective roller. The delivery parameter can also be a derived value, for example the peripheral speed or the torque on the roll surface can be deduced from a speed or a torque of a motor with a known gear ratio and roll diameter.

According to a further embodiment of the web printing machine, it comprises a means for acquiring a printing web parameter of the printing web, the control device being set up to operate the printing machine as a function of the acquired material parameter.

The means comprises in particular a sensor which, for example, detects a conveying speed and / or a tensile stress of the printing web in the area of the first roller, in the area of the second roller and / or between the rollers as the printing web parameter. The sensor preferably works without contact, such as an optical sensor, so that the sensor does not influence the conveying characteristics. It should be pointed out that the printing path parameter is not used to adapt a control frequency of the printing head, but rather to regulate the conveying speed of the printing path. Further printing web parameters are, for example, material parameters of the printing material used, such as a modulus of elasticity.

According to a further embodiment of the web printing machine, it comprises a sensor arranged in the conveying direction of the print web after the digital print head for acquiring sensor data from the printed print web. The control device is set up to determine a correction value as a function of the detected sensor data and the print data and to operate the web printing machine as a function of the correction value.

This embodiment is advantageous because it results in errors in a print image which, for example, are due to incorrect assumptions and / or inaccuracies in a physical one on which the determination of the conveyor speed is based Model of the operated web printing machine can be corrected directly on the basis of an actually achieved printing result.

The sensor is preferably an optical sensor and is set up to detect register marks and / or the printed print motif. Register marks are markings that are periodically printed on the printing web in particular by the digital print head. To this extent, the register marks are part of the print data. A distance between two successively printed register marks depends on the conveying speed. The conveying speed can therefore be deduced from the distance and this can therefore be regulated accordingly. If the printed print motif is recorded, a correspondence between the printed print motif and the print data can be determined. Depending on whether the printed print motif matches the print data or how it deviates therefrom, a correction value can be determined, in particular for the conveying speed to be set, in order to achieve a match.

Furthermore, a computer program product is proposed which causes the method as explained above to be carried out on a program-controlled device.

A computer program product such as a computer program means, for example, as a storage medium, e.g. Memory card, USB stick, CD-ROM, DVD, or also in the form of a downloadable file from a server in a network. This can be done, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program means.

Further possible implementations of the invention also include combinations, not explicitly mentioned, of features or embodiments described above or below with regard to the exemplary embodiments. The skilled person will do this too Add individual aspects as improvements or additions to the respective basic form of the invention.

• Fig. 1 zeigt ein schematisches Blockschaltbild eines Ausführungsbeispiels eines Verfahrens zum Betreiben einer digitalen Bahndruckmaschine;
• Fig. 2 zeigt ein schematisches Blockschaltbild eines ersten Ausführungsbeispiels einer Steuerungsvorrichtung;
• Fig. 3 zeigt ein schematisches Blockschaltbild eines zweiten Ausführungsbeispiels einer Steuerungsvorrichtung; und
• Fig. 4 zeigt schematisch ein Ausführungsbeispiel einer Bahndruckmaschine.

Further advantageous configurations and aspects of the invention are the subject matter of the subclaims and the exemplary embodiments of the invention described below. In the following, the invention is explained in more detail on the basis of preferred embodiments with reference to the attached figures.

• Fig. 1 shows a schematic block diagram of an exemplary embodiment of a method for operating a digital web printing machine;
• Fig. 2 shows a schematic block diagram of a first embodiment of a control device;
• Fig. 3 shows a schematic block diagram of a second embodiment of a control device; and
• Fig. 4 shows schematically an embodiment of a web printing machine.

In the figures, elements that are the same or have the same function have been provided with the same reference symbols, unless otherwise stated.

Fig. 1 FIG. 4 shows a schematic block diagram of an exemplary embodiment of a method for operating a digital web printing machine 200 (see FIG Fig. 4 ).

In a first step 10, a frequency F (see Figs. 2-4 ) with which the digital print head 210 (see Fig. 4 ) to output ink 212 (see Fig. 4 ) is selected. Selecting is understood here to mean, for example, that an operator of the web printing machine 200 inputs the frequency F via a suitable input means. Alternatively, the frequency F can be derived from certain boundary conditions will. Furthermore, it can be provided that the frequency F is fixed, for example, by the print head 210, since this can only be operated with a specific frequency F.

In a second step 20, depending on the selected frequency F, a target conveying speed vs (see FIG Fig. 2 , 3 ) for the conveying speed v (see Fig. 4 ) determined. The target conveying speed vs can, for example, be determined, in particular calculated, from a relationship between the frequency F and a desired print resolution. The print resolution results, for example, from print data D (see Figs. 2-4 ).

In a third step 30, the rollers 220, 230 (see Fig. 4 ), which has a printing path 240 (see Fig. 4 ) through a print area 250 (see Fig. 4 ) promote, regulated such that the conveying speed v of the printing web 240 corresponds to the target conveying speed vs. This is done in particular by a first motor M1 (see Fig. 4 ), which drives the first roller 220 and / or a second motor M2, which drives the second roller 220, can be regulated accordingly.

In a fourth step 40, the digital print head 210 is activated with the selected frequency F and the print data D.

This method can in particular be used to operate a web printing machine 200, the print head 210 of which is not controlled at a variable frequency as a function of a detected conveying speed of the printing web 240.

The following is based on the Fig. 2 and 3 each an exemplary embodiment for a control device 100 is described, which can operate a web printing machine 200 by means of the described method.

Fig. 2 FIG. 11 shows a schematic block diagram of a first exemplary embodiment of a control device 100. The control device 100 comprises a setting unit 110 which is set up to set a selected frequency F. The setting unit 110 comprises, in particular, a clock generator. Furthermore, the setting unit 110 can have an input means or a receiving means for selecting the frequency F.

The setting unit 110 outputs the selected and set frequency F to a determination unit 120 and a control unit 140. The determination unit 120 is set up to determine a target conveying speed vs as a function of the frequency F and of pressure data D. The print data D are specified or entered from the outside in particular and include, for example, a print motif M to be printed (see FIG Fig. 4 ) in the form of machine-readable data. The control unit 140 is set up to read the print data D and a digital print head 210 (see FIG Fig. 4 ) to be controlled accordingly. Print nozzles (not shown) of the digital print head 210 for outputting printing ink 212 (see FIG Fig. 4 ) controlled at frequency F. This means that in each period of the frequency F a printing nozzle outputs a specific amount or a specific volume of the printing ink 212. The printing ink 212 output in a period generates a pixel on the printing web 240.

The determination unit 120 outputs the determined setpoint conveying speed vs to a control unit 130. The control unit 130 controls a first motor M1 as a function of the target conveying speed vs (see FIG Fig. 4 ), which has a first roller 220 (see Fig. 4 ) drives, and / or a second motor M2 (see Fig. 4 ), which has a second roller 230 (see Fig. 4 ) drives. This regulation increases the conveying speed v (see Fig. 4 ) the printing web 240 is set to the target conveying speed vs. This ensures that the printed print motif M matches the print data D.

Fig. 3 FIG. 11 shows a schematic block diagram of a second exemplary embodiment of a control device 100. This second exemplary embodiment has all the features of the first exemplary embodiment from FIG Fig. 2 on. In addition, the control device 100 here comprises three acquisition units 150, 160, 170 and a correction unit 172.

The first detection unit 150 is for detecting a conveying parameter P1, P2 of the first roller 220 (see FIG Fig. 4 ) and / or the second roller 230 (see Fig. 4 ) furnished. The first conveying parameter P1 includes, for example, a peripheral speed v1 (see FIG Fig. 4 ) of the first roller 220 and the second conveying parameter P2 includes, for example, a peripheral speed v2 (see FIG Fig. 4 ) of the second roller 230. The determination unit 120 is set up to determine the conveying speed v of the printing web 240 as a function of the parameters P1, P2. The control unit 130 is set up to control the conveying speed v as a function of the determined conveying speed v.

The second acquisition unit 160 is set up to acquire a printing path parameter P3. This is, for example, a thickness of the printing web 240. The determination unit 120 is set up to determine the conveying speed v of the printing web 240 as a function of the parameter P3. The control unit 130 is set up to control the conveying speed v as a function of the determined conveying speed v.

The third acquisition unit 170 is for acquiring image data B of one by the digital print head 210 (see FIG Fig. 4 ) printed motif M (see Fig. 4 ) furnished. The correction unit 172 determines a correction value K as a function of the captured image data B and the print data D. The correction value K is used by the determination unit 120 to determine a corrected conveying speed vk. For example, the corrected conveying speed vk is a sum from the setpoint conveying speed vs and the correction value K. The determination unit 120 outputs the setpoint conveying speed vs or the corrected conveying speed vk to the control unit 130, whereupon this controls the conveying speed v of the printing web 240 accordingly.

Fig. 4 shows schematically an exemplary embodiment of a web printing machine 200. The web printing machine 200 comprises, in particular, a control device 100 which is set up to operate the web printing machine 200. The control device 100 can, for example, be one of the in FIG Fig. 2 or Fig. 3 shown embodiments correspond. The control device 100 is for performing the based on Fig. 1 described procedure.

The web printing machine 200 comprises a digital print head 210 which is arranged over a printing web 240. The digital print head 210 is set up to output printing ink 212 onto the printing web 240 by means of printing nozzles (not shown). The area in which the print head 210 can output printing ink 212 onto the print web 240 is referred to as the print area 250.

The printing area 250 lies between a first roller 220 and a second roller 230, which convey the printing web 240. The first roller 220 can also be referred to as a feed roller, the second roller 230 can also be referred to as a discharge roller. Four guide rollers 260 are arranged between the rollers 220, 230 and serve to support and guide the printing web 240 in the printing area 250. For reasons of clarity, only one guide roller 260 is identified with a reference number. The guide rollers 260 are not driven and are preferably mounted so that they can rotate very easily, so that they rotate with the printing web 240 without acting on it.

The first roller 220 is driven by a first motor M1, the second roller 230 is driven by a second motor M2. The motors M1, M2 are in particular electric motors and drive the rollers 220, 230 directly, that is, there is no transmission between the motor M1, M2 and the respective roller 220, 230. In this way, a particularly exact regulation of the conveying speed v of the printing web 240 can be implemented.

The control device 100 operates the web printing machine 200. This is done in accordance with FIG Fig. 1 described procedure. The control device 100 operates the web printing machine 200 as a function of print data D and a selected frequency F. The frequency F determines the time intervals at which a print nozzle of the print head 210 can output printing ink 212. The control device 100 determines, as a function of the frequency F and the print data D, with which target conveying speed vs the print web 240 is to be conveyed through the print area 250 so that the printed print motif M matches the print data D. For this purpose, the control device 100 comprises in particular a determination unit 120 (see FIG Fig. 2 or 3 ). Furthermore, the control device 100 comprises a control unit 130 (see Fig. 2 or 3 ), which controls the motors M1, M2 in such a way that the printing web 240 is conveyed at the target conveying speed vs.

In this exemplary embodiment, the printing press 200 also includes an optional sensor 270, which is designed here as a CCD camera. The CCD camera 270 is arranged behind the print head 210 in the conveying direction. The CCD camera 270 detects the print motifs M printed by the print head 210 and converts them into image data B. The image data B are output to the control device 100. This monitors whether the image data B match the print data D, that is, whether the print result obtained corresponds to the print data D. If there is a discrepancy between the image data B and the print data D, a correction unit 172 (see FIG Fig. 3 ) a correction value K, which the control device 100 takes into account when the web printing machine 200 is operated. In particular, the conveying speed v of the printing web 240 is adjusted to a corrected conveying speed vk set. Furthermore, an output quantity of printing ink 212 by a printing nozzle per activation period can also be adapted if, for example, a color intensity of the printed print motif M differs from the print data D. A color mix can also be adjusted for multi-colored printouts.

Although the present invention has been described on the basis of exemplary embodiments, it can be modified in many ways.

List of reference symbols

10

Process step

20th

Process step

30th

Process step

40

Process step

100

Control device

110

Setting unit

120

Investigation unit

130

Control unit

140

Control unit

150

Registration unit

160

Registration unit

170

Registration unit

172

Correction unit

200

Web printing machine

210

Digital print head

212

Printing ink

220

roller

230

roller

240

Print web

250

Pressure area

260

Guide roller

270

sensor

B.

Image data

D.

Print data

F.

frequency

K

Correction value

P1

parameter

P2

parameter

P3

parameter

v

Conveyor speed

v1

Turning speed

v2

Turning speed

vk

corrected conveyor speed

vs.

Setpoint

Claims (14)

A method for operating a digital web printing machine (100) comprising: Selecting (10) a frequency (F) for driving a digital print head (210) at the frequency (F) for outputting printing ink onto a printing web (240), Determination (20) of a target conveying speed (vs) for conveying the printing web (240) as a function of the selected frequency (F) and of print data (D),
Controlling (30) a motor driving a first roller (220) (M1) and / or a motor (M2) driving a second roller (230) as a function of the target conveying speed (vs) such that the print web (240) between the first roller (220) and the second roller (230), in particular directly under the digital print head (210) at which the target conveying speed (vs) is conveyed, and Driving (40) the digital print head (210) with the selected frequency (F) and as a function of the print data (D). Method according to claim 1,
marked by
Detecting a conveying parameter (P1, P2) of the first roller (220) and / or of the second roller (230),
Determining a conveying speed (v) of the printing web (240) as a function of the conveying parameters (P1, P2), and
Control of the first motor (M1) and / or the second motor (M2) as a function of the determined conveying speed (v), so that the conveying speed (v) corresponds to the target conveying speed (vs). Method according to claim 1 or 2,
marked by
Detecting a printing path parameter (P3) of the printing path (240), and
Controlling the first motor (M1) and / or the second motor (M2) as a function of the detected printing web parameter (P3). Method according to one of Claims 1 to 3,
marked by
periodic printing of a register mark on the print web (240) by the digital print head (210),
Detecting a distance between two successively printed register marks on the printing web (240), and
Controlling the first motor (M1) and / or the second motor (M2) as a function of the detected distance. Method according to one of Claims 1 to 4,
marked by
Generation of image data (B) as a function of a print motif (M) printed on the print web (240) by the digital print head (210),
Comparing the image data (B) with the print data (D), and regulating the first motor (M1) and / or the second motor (M2) as a function of a result of the comparison. Method according to one of Claims 1 to 5,
marked by
Setting an output quantity of the printing ink (212) for a printing nozzle of the digital printing head (210) in a period of the selected frequency (F) as a function of the printing data (D) and the target conveying speed (vs). Control device (100) for operating a digital web printing machine (200), comprising: a setting unit (110) for setting a selected frequency (F), a determination unit (120) for determining a target conveying speed (vs) of a printing web (140) as a function of the frequency (F) and of printing data (D), a control unit (130) for controlling a first motor (M1) driving a first roller (220) and / or a second motor (M2) driving a second roller (230) for setting a conveying speed (v) between the first roller (220) ) and the second roller (230) Print web (240) as a function of the target conveying speed (vs), and a control unit (140) for controlling a digital print head (210) for outputting printing ink at the frequency (F) and as a function of the print data (D). Control device according to claim 7,
marked by
a first detection unit (150) for detecting a conveying parameter (P1, P2) of the first roller (120) and / or the second roller (130), wherein
the determination unit (120) is set up to determine the conveying speed (v) as a function of the detected operating parameter (P1, P2) and the control unit (130) to control the first motor (M1) and / or the second motor (M2) in Dependence of the determined conveying speed (v) is set up. Control device according to claim 7 or 8,
marked by
a second detection unit (160) for detecting a print web parameter (P3) of the print web (240), wherein
the determination unit (120) is set up to determine the conveying speed (v) as a function of the detected printing web parameter (P3) and the control unit (130) to control the first motor (M1) and / or the second motor (M2) as a function of the determined conveying speed (v) is set up. Control device according to one of Claims 7 to 9,
marked by
a third acquisition unit (170) for acquiring sensor data (B) from the printed printing web (240), and
a correction unit (172) for determining a correction value (K) as a function of the pressure data (D) and the sensor data (B), wherein
the determination unit (120) is set up to determine a corrected conveying speed (vk) as a function of the Correction value (K) to determine and the control unit (140) for controlling the first motor (M1) driving the first roller (220) and / or the second motor (M2) driving the second roller (230) for setting the corrected conveying speed (vk ) is set up. Web printing machine (200) with a printing web (240) running between a driven first roller (220) and a driven second roller (230), comprising
a digital print head (210) arranged between the first roller (220) and the second roller (230) above the printing web (240) for outputting printing ink (212) onto the printing web (240), and
a control device (100) according to one of claims 7 to 10 for operating the web printing machine (200). Web printing machine according to claim 11,
marked by
a means for detecting a conveying parameter (P1, P2) of the first roller (220) and / or the second roller (230), the control device (100) for operating the printing press (200) as a function of the detected conveying parameter (P1, P2) is set up. Web printing machine according to claim 11 or 12,
marked by
a means for detecting a printing web parameter (P3) of the printing web (240), wherein the control device (100) is set up to operate the printing press (200) as a function of the detected printing web parameter (P3). Web printing machine according to one of Claims 11 to 13,
marked by
a sensor (270) arranged in the conveying direction of the print web (240) after the digital print head (210) for acquiring sensor data (B) from the printed print web (240), wherein
the control device (100) for determining a correction value (K) as a function of the detected sensor data (B) and the print data (D) and is set up to operate the web printing machine (200) as a function of the correction value (K).

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