阅读说明：本技术 运行数字卷筒纸印刷机的方法、控制装置和卷筒纸印刷机 (Method for operating a digital web printing press, control device and web printing press ) 是由 伯恩哈德·迪尔施 菲利普·罗斯特 埃尔玛·舍费尔斯 于 2020-03-27 设计创作，主要内容包括：本发明涉及用于运行数字卷筒纸印刷机的方法、控制装置和卷筒纸印刷机。该方法包括：选定用于驱控数字印刷头(210)的频率(F),利用该频率将印刷油墨(212)输出到印刷卷筒纸(240)上；根据选定的频率和印刷数据(D)确定用于输送印刷卷筒纸的额定输送速度(vs)；根据额定输送速度控制驱动第一辊(220)的马达(M1)和/或驱动第二辊(230)的马达(M2),从而利用额定输送速度在第一辊与第二辊之间输送印刷卷筒纸；以及利用选定的频率并且根据印刷数据驱动数字印刷头。该方法所具有的优点是,利用选定的固定频率驱控卷筒纸印刷机的数字印刷头,因此能省去数字印刷头的复杂动态驱控以及相关的测量和控制系统。(The invention relates to a method for operating a digital web printing press, a control device and a web printing press. The method comprises the following steps: selecting a frequency (F) for actuating the digital print head (210) with which to output printing ink (212) onto the printing web (240); determining a nominal transport speed (vs) for transporting the printing web on the basis of the selected frequency and the printing data (D); controlling a motor (M1) driving the first roller (220) and/or a motor (M2) driving the second roller (230) in dependence on the nominal transport speed, thereby transporting the print web between the first roller and the second roller with the nominal transport speed; and driving the digital print head with the selected frequency and in accordance with the print data. This method has the advantage that the digital print head of the web printing press is actuated with a selected fixed frequency, thus eliminating the need for complex dynamic actuation of the digital print head and associated measurement and control systems.)

1. A method for operating a digital web printing press, the method comprising:

selecting a frequency (F) for actuating the digital printing head (210), with which frequency (F) printing ink is output onto the printing web (240);

determining a nominal transport speed (vs) for transporting the print web (240) on the basis of the selected frequency (F) and the print data (D);

-controlling a first motor (M1) driving a first roller (220) and/or a second motor (M2) driving a second roller (230) as a function of the nominal transport speed (vs) so as to transport the print web (240) between the first roller (220) and the second roller (230) with the nominal transport speed (vs); and is

Controlling the digital print head (210) with the selected frequency (F) and in dependence of the print data (D).

2. Method according to claim 1, characterized in that a first motor (M1) driving a first roller (220) and/or a second motor (M2) driving a second roller (230) is controlled as a function of the nominal transport speed (vs) so that the print web (240) is transported directly under the digital print head (210) with the nominal transport speed (vs).

3. The method according to claim 1 or 2,

detecting a transport parameter (P1, P2) of the first roller (220) and/or of the second roller (230);

determining a transport speed (v) of the print web (240) from the transport parameters (P1, P2); and is

Controlling the first motor (M1) and/or the second motor (M2) as a function of the determined conveying speed (v) such that the conveying speed (v) corresponds to the nominal conveying speed (vs).

4. The method according to any one of claims 1 to 3,

detecting a print web parameter (P3) of the print web (240); and is

Controlling the first motor (M1) and/or the second motor (M2) in accordance with the detected print web parameters (P3).

5. The method according to any one of claims 1 to 4,

periodically printing, by the digital print head (210), registration marks onto the print web (240);

detecting a spacing between two of the register marks printed in succession on the print web (240); and is

Controlling the first motor (M1) and/or the second motor (M2) in accordance with the detected spacing.

6. The method according to any one of claims 1 to 5,

generating image data (B) from a printing theme (M) printed onto the printing web (240) by the digital print head (210);

comparing the image data (B) with the print data (D); and is

Controlling the first motor (M1) and/or the second motor (M2) according to a result of the comparison.

7. The method according to any one of claims 1 to 6,

-setting the output of printing ink (212) for the printing nozzles of the digital printing head (210) during the selected period of the frequency (F) on the basis of the printing data (D) and the nominal delivery speed (vs).

8. A control device (100) for operating a digital web printing press (200), the control device comprising:

a setting unit (110) for setting a selected frequency (F);

a determination unit (120) for determining a nominal transport speed (vs) of the printing web (240) on the basis of the frequency (F) and the 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) so as to set a transport speed (v) of the printing web (240) running between the first roller (220) and the second roller (230) according to the nominal transport speed (vs); and

a drive unit (140) for driving a digital print head (210) to output printing ink using the frequency (F) and in accordance with the printing data (D).

9. The control device according to claim 8,

a first detection unit (150) for detecting a transport parameter (P1, P2) of the first roller (120) and/or of the second roller (130) is provided, wherein,

the determination unit (120) is designed to determine the conveying speed (v) as a function of the detected operating parameters, and the control unit (130) is designed to control the first motor (M1) and/or the second motor (M2) as a function of the determined conveying speed (v).

10. The control device according to claim 8 or 9,

a second detection unit (160) for detecting a print web parameter (P3) of the print web (240) is provided, wherein,

the determination unit (120) is designed to determine the transport speed (v) as a function of the detected print web parameter (P3), and the control unit (130) is designed to control the first motor (M1) and/or the second motor (M2) as a function of the determined transport speed (v).

11. The control device according to any one of claims 8 to 10,

a third detection unit (170) is provided for acquiring sensor data (B) from the printed print web (240), and

a correction unit (172) is provided for determining a correction value (K) from the printing data (D) and the sensor data (B), wherein,

the determination unit (120) is designed for determining a corrected transport speed (vk) from the correction value (K), and the control unit (140) is designed for controlling the first motor (M1) driving the first roller (220) and/or the second motor (M2) driving the second roller (230) to set the corrected transport speed (vk).

12. A web printing press (200) having a print web (240) running between a driven first roller (220) and a driven second roller (230), the web printing press comprising:

a digital print head (210) disposed above the print web (240) between the first roller (220) and the second roller (230), the digital print head for outputting printing ink (212) onto the print web (240); and

control device (100) according to one of claims 8 to 11 for operating the web printing press (200).

13. The web printing press as recited in claim 12,

means are provided for detecting transport parameters (P1, P2) of the first roller (220) and/or of the second roller (230), wherein the control device (100) is designed to operate the web printing press (200) as a function of the detected transport parameters (P1, P2).

14. The web printing press as recited in claim 12 or 13,

a mechanism is provided for detecting a print web parameter (P3) of the print web (240), wherein the control device (100) is designed to operate the web printing press (200) as a function of the detected print web parameter (P3).

15. The web printing press according to any one of claims 12 to 14,

a sensor (270) for acquiring sensor data (B) from the printed print web (240) is arranged downstream of the digital print head (210) in the transport direction of the print web (240), wherein,

the control device (100) is designed to determine a correction value (K) as a function of the detected sensor data (B) and the print data (D) and to operate the web printing press (200) as a function of the correction value (K).

Technical Field

The invention relates to a method for operating a digital web printing press, a control device for operating a digital web printing press and a web printing press having such a control device.

Background

In order to obtain correct printing results, in digital web printers the control of the print heads and the transport of the printing web through the printing zone must be accurately coordinated. In the known digital web printing machines, this control is effected, for example, in that an optical measuring device is arranged in front of the printing head, which optical measuring device measures the current transport speed of the printing web. The frequency of the printing ink output from the print head is controlled according to the transport speed. Since the conveying speed depends on different factors and can vary in particular over time, the frequency is adjusted dynamically. The detection error of the conveying speed is directly reflected as a wrong printed image and/or poor printing quality. Therefore, in order to obtain the desired print quality, the measurement and control system has to work very precisely and is therefore designed to be very complex.

Disclosure of Invention

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

Accordingly, a method for operating a digital web printing press is proposed, which method comprises the following steps. In a first step, a frequency for actuating the digital print head is selected, with which printing ink is output onto the printing web. In a second step, a nominal transport speed for transporting the print web is determined based on the selected frequency and the print data. In a third step, the motor driving the first roller and/or the motor driving the second roller are controlled as a function of the nominal transport speed, so that the printing web is transported with the nominal transport speed between the first roller and the second roller, in particular directly below the digital print head. In a fourth step, the digital print head is controlled using the selected frequency and in accordance with the print data.

This method has the advantage that the digital print head of the web printing press is actuated with a selected fixed frequency, thus eliminating the need for complex dynamic actuation of the digital print head and associated measurement and control systems. The web press operated in this way can therefore be constructed more simply and can therefore be produced more cheaply. By controlling the transport speed of the printing web in dependence on the frequency, the printing result, in particular the printing image matching the printing data, is monitored.

In this process, the causal chain is reversed compared to conventional processes. In the prior art, a print web is transported, the transport speed is measured, and the frequency of the print head is changed in dependence on the measured transport speed. This can lead to a cascade of errors in which measurement errors and control errors are amplified, so that the printing result cannot be used. This can be avoided with the proposed method. In the present case, the frequency of the print heads is preset and the transport speed of the print web is adjusted accordingly. This is possible because the web transport device for transporting the printing web (here, for example, the first roller and the second roller with associated control device) can transport the printing web very stably and precisely.

Between the first roller and the second roller, the digital print head is arranged in particular above the printing web. The nominal transport speed is preferably related to the position of the print web just below the print head. Thus, a nominal transport speed for the printing web is achieved directly below the print head, so that the printing result matches the printing data.

A digital print head (hereinafter also simply referred to as print head) comprises, for example, a plurality of print nozzles. The number of nozzles determines, among other things, the maximum printing resolution of the print head. Furthermore, the maximum printing resolution depends on the minimum amount of printing ink that can be delivered by the print head with the printing nozzles in one cycle. The beat period is the length of one period of the selected frequency. For example, the print resolution is 9600DPI, which corresponds to a dot density of 9600 per inch (DPI ═ dots per inch). This frequency determines the frequency at which the corresponding nozzle can output printing ink. The amount of printing ink to be output per cycle of the beat or per drive control can be set individually for each nozzle of the print head. Furthermore, the amount can be different in each beat period and can be adjusted.

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

The print data includes the subject to be printed, for example as a machine-readable data record. The object to be printed is recorded as digital image data, for example as vector graphics or bitmaps, which are also referred to below as patterns. The pattern is converted or transformed into printing data, for example by means of a printer driver, wherein in particular the maximum resolution of the print head is taken into account. The print data comprise, in particular, the resolution to be used for the replication pattern. Using the known frequency and the existing print data, a nominal transport speed for transporting the print web under the print head can be determined.

For example, the print data includes two lines having a pitch of 1cm and printed in a direction perpendicular to a conveyance direction of the print web. Given a print head resolution and a predefined print head frequency, the nominal transport speed is obtained, for example, as the product of the print head resolution and the frequency. For example, in the case of a resolution of 10000 dots per cm and a frequency of 10kHz, the rated conveying speed is 1cm/s or 0.6 m/min.

The nominal transport speed, which is determined in this way as a function of the selected frequency, is set by corresponding control of the motors for driving the first and/or second rollers transporting the printing web. I.e. the print web is transported at the nominal transport speed, so that correct printing is ensured in accordance with the print pattern.

The rotational speed of the respective roller can be derived from the rotational frequency of the motor driving the respective roller, the transmission ratio and the diameter of the respective roller. In the case of thin (e.g. maximum 0.5mm) printing material, and if there is no slip between the printing web and the respective roller, the rotational speed of the respective roller corresponds to the transport speed of the printing web at the roller. The printing web is transported, for example, under a certain tensile stress. This may lead to an expansion of the print web, the transport speed at the first and second roll may thus be different and may also assume different values between the rolls, which needs to be taken into account in the control.

If the print web is transported at the nominal transport speed and the print heads are driven according to the print data and frequency, the obtained print result, the print output corresponds to the pattern. In particular, the size and color intensity of the printed output corresponds to the size and color intensity of the pattern.

According to one embodiment of the method, a transport parameter of the first roller and/or of the second roller is detected, and the transport speed of the print web is determined as a function of the transport parameter. The first motor and/or the second motor are controlled in accordance with the determined conveying speed such that the conveying speed corresponds to a nominal conveying speed.

The advantage of this embodiment is that the actual transport speed is determined and used to control the motor, which is used to transport the printing web at the nominal transport speed.

The transport parameters include, for example, the rotation frequency, the torque, the diameter, the winding of the respective roller with the print web, and/or the friction coefficient between the respective roller and the print web. The winding for example indicates which part of the respective roll is surrounded by the printing web. The winding may be expressed as an angle, for example. The coefficient of friction relates in particular to the respective combination of the roller with the particular material.

These parameters can influence the transport properties, in particular the transport speed. The rotational speed or torque of each roller can be derived from the rotational speed or torque of each motor. Preferably, a transfer function is known for this purpose, for example taking into account the transmission ratio and/or the loss value.

The determined transport speed may include a first transport speed of the print web at the first roller, a second transport speed of the print web at the second roller, and/or a transport speed at one or more points between the two rollers.

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

The advantage of this embodiment is that print web parameters which may influence the transport properties, in particular the transport speed, are taken into account.

The printing web parameters include, inter alia, material parameters, such as the modulus of elasticity and/or the behavior of the printing material during the printing process. Furthermore, geometrical parameters such as the thickness of the printed material and/or the width of the printed web may be taken into account.

For example, the thickness of the printed material can be variable, which can directly affect the transport speed. In this embodiment, for example, the material thickness is detected and the transport speed is controlled accordingly as a function of the detected thickness.

According to another embodiment of the method, register marks are printed periodically on the printing web by a digital print head. Then, a spacing between two register marks printed successively on the print web is detected, and the first motor and/or the second motor is controlled according to the detected spacing.

The advantage of this embodiment is that the printing result obtained can be checked directly by the register marks and the control of the roller drive, i.e. the first motor and/or the second motor, can be adjusted accordingly.

Periodic printing of register marks is preferably understood to mean that a fixed time interval, for example one second, is provided between two register marks printed in succession at time. The actual transport speed is derived from the detected spacing between two successively printed register marks, for example by the quotient of the spacing divided by the time interval. For example, a special register mark sensor can be provided, which is arranged behind the print head in the transport direction.

In addition to the spacing, the color saturation or color intensity of the registration mark may also be recorded. If the saturation is too low, the amount of printing ink output by the printing nozzles per beat cycle can be controlled, for example.

According to a further embodiment of the method, the image data is generated from a printing theme (Druckmotiv) printed on the printing web by the digital printing head. The image data is compared to the print data. The first motor and/or the second motor are controlled according to the result of the comparison.

This embodiment is advantageous because the printing result is at least partially, advantageously completely, detected and checked by the comparison. For example, a digital image sensor such as a CCD (charge coupled device) type camera is arranged behind the print head in the conveying direction and captures image data. The comparison means compare, for example, the size of the printed pattern with the size of the pattern in the print data. For example, a difference is formed between the detected value and the theoretical value. If the difference results in a positive, the printed pattern is larger than the pattern (the transport speed is too high); if the difference is negative, the printed pattern is smaller than the design (the transport speed is too slow). Thus, the wrong conveying speed causes the image to be enlarged or compressed compared to the original image, and in this design, such a mistake can be corrected by controlling the conveying speed.

In this embodiment, the color saturation or color intensity of the printed image can also be compared with the pattern, and the output of printing ink from the printing nozzles per cycle of the clock can be controlled accordingly.

According to a further embodiment of the method, the output of printing ink for the printing nozzles of the digital printing head in a period of the selected frequency is set as a function of the printing data and the set transport speed.

This design is advantageous because it allows control of the maximum color intensity or print density. Further, even at different conveyance speeds, shading or color gradation can be produced in the same manner.

According to a second aspect, a control device for operating a digital web printing press is proposed. The control device includes: a setting unit for setting the selected frequency; a determination unit for determining a nominal transport speed of the print web on the basis of the frequency and the print data; a control unit for controlling a first motor driving the first roller and/or a second motor driving the second roller so as to set a transport speed of a print web running between the first roller and the second roller according to a rated transport speed; and a driving unit for driving the digital printing head so as to output the printing ink by using the frequency and according to the printing data.

Advantageously, the control device is designed for operating the digital web printing press according to the method of the first aspect, whereby the above-mentioned advantages are obtained. The embodiments and features explained for the method apply correspondingly to the control device.

The control device is implemented at least partially in hardware technology, but may also be implemented at least partially in software technology. The control device can be designed, for example, as a computer or microprocessor. The parts implemented in software technology are for example designed as computer program products, functions, routines, parts of program code or executable objects.

Preferably, the setting unit comprises a clock generator designed to output the selected frequency.

According to one embodiment of the control device, the control device comprises a first detection unit for detecting a transport parameter of the first roller and/or of the second roller, wherein the determination unit is designed to determine the transport speed as a function of the detected operating parameter. The control unit is designed to control the first motor and/or the second motor depending on the determined conveying speed.

The conveying speed is thus advantageously controlled as a function of the conveying speed derived from the conveying parameters.

The transport parameters include, for example, the rotation frequency, the torque, the diameter, the winding of the respective roller with the print web, and/or the friction coefficient between the respective roller and the print web. The winding for example indicates which part of the respective roll is surrounded by the printing web. The winding may be expressed as an angle, for example. The coefficient of friction relates in particular to the respective combination of the roller with the particular material.

These parameters can influence the transport properties, in particular the transport speed. The rotational speed or torque of each roller can be derived from the rotational speed or torque of each motor. Preferably, a transfer function is known for this purpose, for example taking into account the transmission ratio and/or the loss value.

The determined transport speed may include a first transport speed of the print web at the first roller, a second transport speed of the print web at the second roller, and/or a transport speed at one or more points between the two rollers.

According to a further embodiment of the control device, the control device comprises a second detection unit for detecting a print web parameter of the print web. The determination unit is designed to determine the transport speed on the basis of the detected print web parameters. The control unit is designed to control the first motor and/or the second motor depending on the determined conveying speed.

The transport speed is thus advantageously controlled in dependence on a transport speed derived from the print web parameters.

The printing web parameters include, inter alia, material parameters, such as the modulus of elasticity and/or the behavior of the printing material during the printing process. Furthermore, geometrical parameters such as the thickness of the printed material and/or the width of the printed web may be taken into account.

For example, the thickness of the printed material can be variable, which directly affects the transport speed. In this embodiment, for example, the material thickness is detected and the transport speed is controlled as a function of the detected thickness.

According to a further embodiment of the control device, it comprises a third detection unit for detecting sensor data from the printed printing web and a correction unit for determining a correction value on the basis of the printing data and the detected sensor data. The determination unit is designed to determine the corrected transport speed on the basis of the correction value, and the control unit is designed to control the first motor driving the first roller and/or the second motor driving the second roller to set the corrected transport speed.

This design is advantageous because it enables errors in the printed image to be corrected directly on the basis of the actually obtained printing result, which errors can be caused, for example, by incorrect presettings and/or inaccuracies in the physical model of the web press used for determining the transport speed.

For example, the third detection unit includes an optical sensor, such as an image sensor, which detects the printed printing subject and converts it into image data. The correction unit compares the obtained image data with the print data. The correction unit is, for example, a component of the determination unit. The correction unit determines, in particular, whether the image data matches the print data in terms of pattern size and color intensity or whether there is a deviation. The type of deviation is also determined, for example, whether compression or tension is present. A corresponding correction value is determined and output. The correction value is used to determine the corrected conveying speed, for example by addition or multiplication.

According to a third aspect, a web printing press is provided having a printing web running between a driven first roller and a driven second roller. The web printing press includes a digital print head disposed over the print web between the first roller and the second roller for outputting printing ink onto the print web. The web printing press also comprises a control device according to the second aspect, which control device is designed for operating the web printing press.

Advantageously, the web printing press can be operated according to the method of the first aspect by means of the control device, whereby the above-mentioned advantages are obtained. The embodiments and features described for the method are correspondingly suitable for a web-fed printing press.

According to one embodiment of the web printing press, the device comprises a device for detecting a transport parameter of the first roller and/or of the second roller. The control device is designed to operate the printing press according to the detected transport parameters.

The device comprises, in particular, sensors which detect, for example, the rotational speed of the respective roller and/or the torque on the roller surface of the respective roller as a conveying parameter. The control device takes into account transport parameters, in particular for controlling the motors driving the individual rollers. The transport parameter may also be a derived value, for example the rotational speed or the torque on the roller surface can be derived from the speed or torque of a motor with a known gear ratio and roller diameter.

According to a further embodiment of the web printing press, which comprises a device for detecting a printing web parameter of the printing web, the control device is designed to operate the printing press on the basis of the detected material parameter.

The device comprises, in particular, sensors which detect, for example, the transport speed and/or the tension of the printing web in the region of the first roller, in the region of the second roller and/or between the rollers as printing web parameters. The sensor preferably operates in a contactless manner, for example an optical sensor, so that the sensor does not influence the transport properties. It should be noted that the print web parameters are not used to control the drive frequency of the print heads, but rather to control the transport speed of the print web. Further printing web parameters are, for example, the material parameters of the printing material used, for example the modulus of elasticity.

According to a further embodiment of the web printing press, a sensor is arranged downstream of the digital printing head in the transport direction of the printing web, which sensor is used to detect sensor data from the printing web being printed. The control device is designed to determine a correction value on the basis of the detected sensor data and the printing data and to operate the web printing press on the basis of the correction value.

This design is advantageous because it enables errors in the printed image to be corrected directly on the basis of the actually obtained printing result, which errors can be caused, for example, by incorrect presettings and/or inaccuracies in the physical model of the web press used for determining the transport speed.

The sensor is preferably an optical sensor and is designed for detecting register marks and/or printed matter. Register marks refer to marks that are periodically printed (particularly by a digital print head) on a print web. Thus, the register mark is an integral part of the print data. The spacing between two successively printed register marks depends on the transport speed. The spacing can therefore be used to infer the transport speed, which can therefore be controlled accordingly. If a printed printing topic is detected, it may be determined that the printed printing topic matches the printing data. Depending on whether the printing subject printed matches the printing data or differs from the printing data, correction values can be determined, in particular for the transport speed to be set, in order to achieve a match.

Furthermore, a computer program product is proposed, which causes the method as set forth above to be executed on a device controlled by a program.

For example, a computer program product, such as a computer program element, is provided as a storage medium, such as a memory card, a U-disk, a CD-ROM, a DVD, or as a file downloadable from a server in a network. For example, it may be implemented in a wireless communication network by transmitting a corresponding file with a computer program product or computer program element.

Other possible implementations of the invention also include combinations of features or embodiments described above or below with reference to embodiments that are not explicitly described. Those skilled in the art will also add various aspects as improvements or additions to the various basic concepts of the present invention.

Drawings

Further advantageous developments and aspects of the invention are the embodiments of the invention described below. The invention is explained in detail below on the basis of preferred embodiments and with reference to the drawings.

FIG. 1 shows a schematic block diagram of an embodiment of a method for operating a digital web printing press;

fig. 2 shows a schematic block diagram of a first embodiment of the control device;

fig. 3 shows a schematic block diagram of a second embodiment of the control device; and

FIG. 4 shows a schematic view of an embodiment of a web printing press.

Detailed Description

In the drawings, identical or functionally identical elements have identical reference numerals, unless otherwise specified.

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

In a first method step 10, a frequency F (see fig. 2 to 4) is selected, at which the digital print head 210 (see fig. 4) is actuated in order to output printing ink 212 (see fig. 4). The selection here represents, for example, the operator of the web printing press 200 entering the frequency F via a suitable input device. Alternatively, the frequency F may be derived from certain boundary conditions. It can furthermore be provided that the frequency F is permanently preset, for example, by the print head 210, since it can only be operated at a specific frequency F.

In a second method step 20, a setpoint conveying speed vs (see fig. 2, 3) for the conveying speed v (see fig. 4) is determined as a function of the selected frequency F. The setpoint conveying speed vs can be determined, in particular calculated, for example as a function of the relationship between the frequency F and the desired printing resolution. The printing resolution is derived, for example, from the printing data D (see fig. 2 to 4).

In a third method step 30, a first roller 220 and a second roller 230 (see fig. 4) are controlled, which transport a print web 240 (see fig. 4) through a printing zone 250 (see fig. 4) such that a transport speed v of the print web 240 corresponds to a nominal transport speed vs. This is achieved in particular by controlling the first motor M1 (see fig. 4) driving the first roller 220 and/or the second motor M2 driving the second roller 220 accordingly.

In a fourth method step 40, the digital print head 210 is actuated using the selected frequency F and the print data D.

The method can be used in particular for operating a web printing press 200 whose printing heads 210 are not actuated at variable frequencies as a function of the detected transport speed of the printing web 240.

An exemplary embodiment of a control device 100, which is capable of operating a web printing press 200 by means of the described method, is described below with reference to fig. 2 and 3.

Fig. 2 shows a schematic block diagram of a first embodiment of the control device 100. The control device 100 comprises a setting unit 110 which is designed to set the selected frequency F. The setting unit 110 comprises, inter alia, a clock generator. Furthermore, the setting unit 110 can also have input means or receiving means for selecting the frequency F.

The setting unit 110 outputs the selected and set frequency F to the determination unit 120 and the driving unit 140. The determination unit 120 is designed to determine the nominal conveying speed vs from the frequency F and the printing data D. The printing data D are in particular preset or input from the outside and comprise, for example, the printing subject M to be printed in the form of machine-readable data (see fig. 4). The actuation unit 140 is designed to read the printing data D and to actuate the digital print head 210 accordingly (see fig. 4). Here, the printing nozzles (not shown) of the digital print head 210 for outputting printing ink 212 (see fig. 4) are driven at a frequency F. That is, in each cycle of frequency F, the printing nozzle outputs a certain amount or volume of printing ink 212. The printing ink 212 output during a cycle produces pixels on the print web 240.

The determination unit 120 outputs the determined rated conveyance speed vs to the control unit 130. The control unit 130 controls the first motor M1 (see fig. 4) driving the first roller 220 (see fig. 4) and/or the second motor M2 (see fig. 4) driving the second roller 230 (see fig. 4) according to the rated conveying speed. By this control, the conveyance speed v (see fig. 4) of the print web 240 is set to the rated conveyance speed vs. This ensures that the printed printing subject M matches the printing data D.

Fig. 3 shows a schematic block diagram of a second embodiment of the control device 100. This second embodiment has all the features of the first embodiment of fig. 2. In addition, the control device 100 here includes a first detection unit 150, a second detection unit 160, a third detection unit 170, and a correction unit 172.

The first detection unit 150 is designed for detecting a first transport parameter P1 and/or a second transport parameter P2 of the first roller 220 (see fig. 4) and/or the second roller 230 (see fig. 4). The first conveying parameter P1 comprises, for example, the rotational speed v1 of the first roller 220 (see fig. 4), and the second conveying parameter P2 comprises, for example, the rotational speed v2 of the second roller 230 (see fig. 4). The determination unit 120 is designed to determine the transport speed v of the print web 240 on the basis of the first transport parameter P1, the second transport parameter P2. The control unit 130 is designed to control the transport speed v in dependence on the determined transport speed v.

Second detection unit 160 is designed to detect print web parameter P3. This is, for example, the thickness of print web 240. The determination unit 120 is designed to determine the transport speed v of the print web 240 on the basis of the print web parameter P3. The control unit 130 is designed to control the transport speed v in dependence on the determined transport speed v.

The third detection unit 170 is designed to detect the image data B of the printing subject M (see fig. 4) printed by the digital print head 210 (see fig. 4). The correction unit 172 determines a correction value K from the detected image data B and print data D. The correction value K is used in the determination unit 120 to determine the corrected conveyance speed vk. For example, the corrected conveyance speed vk is the sum of the rated conveyance speed vs and the correction value K. The determination unit 120 outputs the setpoint transport speed vs or the corrected transport speed vk to the control unit 130, which accordingly controls the transport speed v of the print web 240.

FIG. 4 schematically illustrates one embodiment of a web printing press 200. The web printing press 200 comprises, in particular, a control device 100, which is designed to operate the web printing press 200. The control device 100 may for example correspond to one of the embodiments shown in fig. 2 or 3. The control device 100 is designed to carry out the method described with reference to fig. 1.

Web printing press 200 includes a digital print head 210 disposed over a print web 240. Digital print head 210 is designed to output printing ink 212 through printing nozzles (not shown) onto print web 240. Print zone 250 represents the area in which print head 210 may print printing ink 212 onto print web 240.

Print zone 250 is located between first roll 220 and second roll 230 that transport print web 240. The first roller 220 may also be referred to as a supply roller, and the second roller 230 may also be referred to as a discharge roller. Four guide rollers 260 are disposed between the first roller 220 and the second roller 230 and serve to support and guide the print web 240 in the print zone 250. For the sake of clarity, only one guide roller 260 is indicated with a reference numeral. The guide roller 260 is not driven and is preferably mounted in a flexible rotatable manner so that it can rotate with the print web 240 without affecting the print web.

The first roller 220 is driven by a first motor M1, and the second roller 230 is driven by a second motor M2. The first motor M1 and the second motor M2 are in particular electric motors and directly drive the first roller 220 and the second roller 230, i.e. there is no transmission between the first motor M1, the second motor M2 and the respective first roller 220, the second roller 230. In this way, a particularly precise control of the transport speed v of the print web 240 can be achieved.

The control device 100 operates the web printing press 200. This is achieved according to the method described with reference to fig. 1. Control device 100 operates web printing press 200 based on print data D and selected frequency F. The frequency F determines the time interval during which the printing nozzles of the print head 210 can output the printing ink 212. The control device 100 determines from the frequency F and the print data D at which nominal transport speed vs the print web 240 is to be transported through the printing zone 250 in order to match the printed print theme M to the print data D. For this purpose, the control device 100 comprises, in particular, a determination unit 120 (see fig. 2 or 3). Furthermore, the control device 100 comprises a control unit 130 (see fig. 2 or 3), which control unit 130 controls the first motor M1 and the second motor M2 such that the print web 240 is transported with the nominal transport speed vs.

In this embodiment, the printing press 200 also comprises an optional sensor 270, which is here designed as a CCD camera. The CCD camera is arranged downstream of the print head 210 in the conveying direction. The CCD camera picks up the printing subject M printed by the print head 210 and converts it into image data B. The image data B is output to the control device 100. It is monitored whether the image data B matches the print data D, i.e., whether the obtained print result corresponds to the print data D. If there is a difference between the image data B and the print data D, the correction unit 172 (see fig. 3) determines a correction value K, which the control device 100 takes into account when operating the web printing press 200. In particular, the transport speed v of the print web 240 is set to the corrected transport speed vk. Furthermore, for example, when the color intensity of the printed printing subject M is different from the printing data D, the output amount of the printing ink 212 may also be adjusted by the printing nozzle in each activation period. In the case of multicolor printing, the color mixture can also be adjusted.

Although the present invention has been described in terms of embodiments, it can be modified in various ways.

List of reference numerals

10 method step

20 method step

30 method step

40 method step

100 control device

110 setting unit

120 determination unit

130 control unit

140 drive and control unit

150 first detecting unit

160 second detection unit

170 third detecting unit

172 correcting unit

200 web printing press

210 digital print head

212 printing ink

220 first roller

230 second roll

240 print web

250 print area

260 guide roller

270 sensor

B picture data

D printing data

Frequency F

Correction value of K

P1 first conveying parameter

P2 second conveying parameter

P3 print web parameters

v transport speed

v1 rotational speed

v2 rotational speed

vk corrected transport speed

vs. nominal transport speed.