Method for operating a web printing press

Abstract

A method according to the invention for operating a web-fed printing press for producing printed products, which comprises a roll changer (10) and a plurality of printing units (20, 50), wherein a flying web change from a first web (13) to a second web (15) takes place to create a splice (17) and wherein settings are made on the printing units (20, 50) in accordance with the passage of the splice (17) through the web-fed printing press (1), is characterized in that at least two printing units (20) of the web-fed printing press are each designed and provided as a double printing unit (20) for flexographic printing and are operated for producing printed products, wherein each existing double printing unit (20) comprises a first partial printing unit (21) and a second partial printing unit (22),and that a respective first partial printing unit (21) or second partial printing unit (22) is activated or deactivated in accordance with the passage of the splice (17) through the web-fed printing press (1), or that switching occurs from a first partial printing unit (21) to a second partial printing unit (22) of the respective double-sided printing unit (20) - or vice versa. The invention advantageously enables the non-stop and automated operation of a flexographic printing press during web changes. The invention is advantageously used in the operation of a web-processing rotary printing press for flexographic printing; it increases its degree of automation, productivity, and print quality.

Description

invention

[0001] The invention relates to a method for operating a web-fed printing press having the features of the preamble of claim 1 and claim 17. field of technology

[0002] The invention lies in the technical field of the graphic arts industry, and in particular in the field of operating a flexographic printing press, i.e., a rotary printing press for printing with flexographic printing plates on web-like printing materials. In particular, the invention lies in the subfield of controlling or regulating the machine or its drives and / or actuators to increase print quality and productivity and / or avoid or reduce malfunctions.

[0003] JP2006321213A discloses an offset web printing press with a roll changer and a plurality of printing units. If a web roll is almost used up, a new web roll with essentially the same web material, i.e., one that still matches the existing print job, is changed on the fly, or both webs are joined together at a splice. During such a web change, register changes can occur as a result of the creation and passage of the splice through the machine, and therefore a necessary adjustment of the register settings of the printing units is carried out. This adjustment appears to be coordinated with the passage of the splice through the web printing press. It is not disclosed that a print image change also occurs simultaneously with the web change, that the two webs differ significantly (e.g.(web thickness, web width, or web material) or that the printing cylinder or offset cylinder is shut down when making the register adjustments. It also seems that only the longitudinal register, but not the cross register, is addressed. Register sensors are mentioned, but not their measuring positions. A database can be accessed when making the register adjustments.

[0004] A web-processing flexographic printing machine with double printing units is known, for example, from DE102017222700A1 or DE102021126115A1.

[0005] During continuous operation of a flexographic printing press (highly productive "non-stop" operation), a web change may occur, whereby the two webs differ significantly in at least one web parameter, particularly the web thickness. This can occur, for example, during a job change. Print shop operators demand that such a change should not interrupt production, should not reduce print quality, and should generate little or no waste. Print shop operators also demand further automation of the printing presses in order to save personnel costs or to replace missing personnel. Technical task

[0006] It is therefore an object of the present invention to provide an improvement over the prior art, which in particular makes it possible to operate a flexographic printing machine non-stop and automatically during web changes. Inventive solution to the problem

[0007] This object is achieved according to the invention by a method according to claim 1 and claim 17.

[0008] Advantageous and therefore preferred developments of the invention emerge from the subclaims as well as from the description and the drawings.

[0009] A method according to the invention for operating a web-fed printing press for producing printed products, which comprises a roll changer and a plurality of printing units, wherein a flying web change from a first web to a second web takes place to create a splice, and wherein settings are made on the printing units in accordance with the passage of the splice through the web-fed printing press, is characterized in that at least two printing units of the web-fed printing press are each designed and provided as a double printing unit for flexographic printing and are operated for producing printed products, wherein each existing double printing unit comprises a first partial printing unit and a second partial printing unit,and that a respective first partial printing unit or second partial printing unit is activated or deactivated in accordance with the passage of the splice through the web-fed printing press, or that switching takes place from a first partial printing unit to a second partial printing unit of the respective double printing unit - or vice versa.

[0010] A further (alternatively formulated) method according to the invention for operating a web-fed printing press, wherein a flying web change from a first web to a second web takes place with the creation of a splice, is characterized in that at least two printing cylinders of separate printing units are each switched off from the first web or switched on to the second web in a manner coordinated with the passage of the splice through the web-fed printing press. Advantageous embodiments and effects of the invention

[0011] The invention advantageously enables a flexographic printing machine to be operated non-stop and automatically during web changes.

[0012] The invention is advantageously used in the operation of a web-processing rotary printing press for flexographic printing; it increases its degree of automation, productivity, and print quality.

[0013] The invention advantageously avoids production interruptions and thus reduces production costs. The invention advantageously reduces or eliminates waste, thus also reducing production costs. The invention advantageously improves print quality, e.g., through rapid and optimal adjustment of the pressure (impression cylinder to counter cylinder), which, in particular, prevents pinch marks, print dropouts, or excessively low pressure in flexographic printing. The invention allows for fewer or less trained personnel to be employed, thus further reducing production costs.

[0014] The invention is particularly applicable to so-called on-the-fly job changes, e.g., from a first print job for a first product (first print image, first web material, first web thickness) to a second print job for a different second product (second print image, second web material, second web thickness). The products can preferably be packaging.

[0015] According to the invention, "the switching is coordinated with the passage of the splice through the web-fed printing press, for example, from a first partial printing unit to a second partial printing unit of the respective double-sided printing unit." Since the splice passes through the double-sided printing units of the printing press sequentially, the switching occurs one double-sided printing unit at a time, i.e., not simultaneously at all printing units, but with a time offset corresponding to the respective web travel time from double-sided printing unit to double-sided printing unit. Preferably, all double-sided printing units are ultimately switched.

[0016] Activation, deactivation or switching in the double-sided printing unit preferably takes place close to the time at which the splice passes the printing nip between the impression cylinder and the counter cylinder, and preferably successively, i.e. step by step and sequentially from printing unit to printing unit. In this way, waste can be saved optimally. Ideally, switching takes place as soon as the splice passes the printing nip. Switching is therefore synchronized with the movement of the splice through the web-fed printing press. It would be desirable for switching to take place very close to the splice passing through the double-sided printing unit and, in particular, through the printing nip formed there. However, the time-varying location of the splice must be known for this, which is preferably done using a signal from the reel stand or a corresponding sensor, and preferably a computer.Since the speed of web transport in industrial web-fed printing machines is extremely high, it is advantageous to position the sensor at an appropriate spatial distance in front of the printing unit / in front of the printing nip in order to be able to trigger an appropriate reaction for the switching process in good time.

[0017] Similarly, a single printing unit (or several, preferably successively) can be activated or deactivated in a manner that synchronizes the splice's passage through the web-fed printing press. The single printing unit can, for example, be a coating unit with a coating cylinder; in this case, the single printing unit can remain activated during a web change.

[0018] The invention can be extended to machines or units for further processing, e.g., for punching, folding, gluing, or even palletizing. Such machines or units can be automatically switched when changing the printing substrate: For example, settings for punching and / or folding can be adjusted depending on the printing substrate.

[0019] Instead of flexographic printing, the invention can also be used in other printing processes, e.g. gravure printing. Further developments of the invention

[0020] Preferred developments of the invention (hereinafter referred to as "developments") are described below. These can also be combined with one another where not technically mutually exclusive.

[0021] A further development can be characterized in that the second partial printing units or their respective flexographic printing cylinders - or in the converse case, the first partial printing units or their respective flexographic printing cylinders - are adjusted to the second web during switchover at a speed adapted to the speed of the second web. A further development can be characterized in that the second partial printing units or their respective flexographic printing cylinders - or in the converse case, the first partial printing units or their respective flexographic printing cylinders - are adjusted to the second web during switchover at a pressure or feed adapted to the second web or its web parameters. A further development can be characterized in that the pressure or feed is adjusted separately on both lateral sides of the second partial printing unit.For this purpose, the thickness of the web can be measured at several points (in a lateral direction to the transport direction of the web). A further development can be characterized in that the anilox cylinders of the second partial printing units - or conversely the anilox cylinders of the first partial printing units - are adjusted to the flexographic printing cylinders during switchover with a pressure adapted to the second web or its web parameters. A further development can be characterized in that the second partial printing units or their respective flexographic printing cylinders - or conversely the first partial printing units or their respective flexographic printing cylinders - are adjusted to the second web during switchover with a pre-register adapted to the second web or its web parameters. A further development can be characterized in that the pre-register comprises the longitudinal register and the cross-register.Starting - as well as stopping - can preferably be done with servo motors.

[0022] A further development can be characterized by the dryer performance being adjusted to the second web or its web parameters during switchover. The dryers can be located on the web path between the double printing units and / or between the partial printing units.

[0023] A further development can be characterized by a print job change when switching between print jobs. A further development can be characterized by a print image change when switching between print jobs.

[0024] A further development can be characterized in that the flexographic printing cylinders of the first partial printing units - or in the converse case the flexographic printing cylinders of the second partial printing unit - are successively switched off or switched on in a timely manner as the splice passes through the web-fed printing press. A further development can be characterized in that the flexographic printing cylinders of the first partial printing units - or in the converse case the flexographic printing cylinders of the second partial printing unit - are switched off directly before the splice or switched on directly after the splice. A further development can be characterized in that the flexographic printing cylinders of the second partial printing units are switched on in a timely manner as the splice passes through the web-fed printing press. A further development can be characterized in that the flexographic printing cylinders of the second partial printing units are switched on directly after the splice.A further development can be characterized by the fact that a flexographic printing cylinder of a printing unit is stopped directly before the splicing point and started again directly after the splicing point.

[0025] A further development can be characterized in that the double printing units each comprise a register sensor (or at least two), and in that the register sensors are adjusted in their respective measuring positions in accordance with the passage of the splice through the web-fed printing press. A further development can be characterized in that the register sensors are moved transversely to the transport direction of the webs. A further development can be characterized in that the double printing units are each operated with a register control algorithm and at least one register control parameter, and in that the register control algorithm and / or the register control parameters are adjusted in accordance with the passage of the splice through the web-fed printing press.

[0026] A further development can be characterized in that the first web and the second web differ significantly in at least one web parameter. A further development can be characterized in that the web parameter is one of the following parameters: web thickness, web width, web material, web surface. The web surface differs significantly, for example, if the material is recycled and / or coated on one or both sides and / or calendered and / or drawn and / or extruded. The roughness of the web surfaces of two webs or their color can also vary. The material / surface parameters present in a web to be processed can be measured: via reflection or IR spectroscopy or using ultrasound or laser light. The measurement(s) are preferably carried out before the printing unit, particularly preferably shortly before the printing unit (little waste!). The measurement, in particular of the web thickness, is preferably carried out continuously.The web thickness can preferably be measured using an optical measuring system. Alternatively, the required parameters can be loaded from a database. Alternatively, the required parameters can be stored on the web (e.g., QR code) or the web roll (e.g., QR code or NFC chip) and read out, preferably in the roll changer. A further development can be characterized by the web thickness being determined by sensors. A further development can be characterized by the web parameters being stored and made available in a digital database.

[0027] A further development can be characterized by the fact that the second web is connected to the first web at the adhesive point.

[0028] A further development can be characterized in that during the passage of the splice through the web-fed printing press, at least one first partial printing unit is set for a first print job and contributes to the first print job on the first web and that at least one second partial printing unit is set for a second print job and contributes to the second print job on the second web.

[0029] A further development can be characterized in that the web tension is adjusted before the double printing units and / or after the double printing units, in particular that the inlet web tension is adjusted.

[0030] A further development can be characterized in that at least one single printing unit is provided in addition to the double printing units.

[0031] A further development can be characterized in that when the web width changes - ie from a first width to a second, larger or smaller width - at least one sensor or another component which is arranged at a working distance from the first width is moved to a safety distance from the second width and from there to a new working distance from the second width.

[0032] A further development can be characterized by the fact that printing units for gravure printing with gravure cylinders are used instead of printing units for flexographic printing.

[0033] A further development of the further method according to the invention can be characterized in that at least one double printing unit or at least one single printing unit is involved in the stopping and / or starting.

[0034] The features and combinations of features disclosed in the above sections Technical Field, Invention and Further Developments as well as in the following section Exemplary Embodiments represent - in any desired combination with one another - further advantageous developments of the invention. Example 1: Concrete application

[0035] A package A with a circumference of 567 mm ("six-pack") is being printed on the printing press. The corresponding web WA has a thickness of 300 µm and is located as a roll RA on a winding spindle WA . A roll RB is inserted into the free part of the non-stop unwinder; this roll has a thickness of 250 µm, for example. The print job for package B with a circumference of 678 mm ("mint tea") is prepared in the machine while it continues to produce package A. Job A is finished when the roll RA has been unwound from the winding spindle WA. Meanwhile, the winding spindle WB is brought up to machine speed and "spliced" , i.e. the web BB is adhesively bonded to the running web BA. The two webs therefore have different thicknesses and possibly also different moduli of elasticity.As soon as the new web BB enters the machine, certain machine parameters are adjusted so that as little waste as possible is created. Next, print job B, i.e. the corresponding printing cylinders, are brought up to speed and into register with each other in the machine, while production of packaging A continues. The print position for print job B then takes place exactly at the point where the new web BB passes the respective printing unit. The print setting, i.e. the pressure / position (to the web), is adjusted so that it suits the new printing substrate with the changed thickness. This is initially done in the front part of the printing press, where the material is just being fed in and print job B is being printed. In the rear part of the printing press, where print job A is still running, the value 300µm is used for the print settings so as not to create any waste there.The changeover takes place while the printing press continues production. Therefore, two different webs, BA and BB, with different properties, are simultaneously in the press, and the printing press "manages" the two material webs as well as the two associated print jobs, A and B, with different pack sizes / pack designs. Over time, the material change (splice) moves toward the end of the printing press. At a certain point, the changeover process is complete, and only print job B is being produced, and only web BB remains in the press. Example 2: Concrete attitude changes

[0036] The following specifications and adjustments can be changed individually, in groups, or all together during the splice run: printing units involved, web thickness, web width, web material, web modulus of elasticity, web tension, pressure / adjustment between impression and counter cylinder and / or between anilox and impression cylinder, print image, print format, pre-register (register presetting), locations of the register marks on the web (axial and circumferential), measuring locations of the register control sensors (axial and circumferential), dryer settings (temperature, fan speed, UV power), speed of the ink pumps. Embodiments of the invention and figures

[0037] The figures show preferred embodiments of the invention and its further developments. Corresponding features are provided with the same reference numerals throughout the figures. Recurring reference numerals have been partially omitted for clarity. Figure 1 shows a schematic representation of a sectional view of a web-fed printing press when carrying out a preferred embodiment of the method according to the invention. Figure 2 shows a schematic representation of a sectional view of a roll changer involved in carrying out a preferred embodiment of the method according to the invention. Figures 3 , 4 and 5 each show a schematic representation of a sectional view of a double printing unit involved in carrying out a preferred embodiment of the method according to the invention.

[0038] Figure 1shows a web-fed printing press 1, in particular for flexographic printing or gravure printing, for printing a printing material web 2, in particular a paper or cardboard web, which is conveyed through the press 1 via a number of guide rollers 3 in a transport direction 4. The control of the web-fed printing press 1 is preferably carried out via a computer 55.

[0039] The web-fed printing machine 1 comprises a roll changer 10 (cf. Figure 2) for flying roll changes with two unwinders 11 for unwinding a first roll 12 or a first web 13 and for unwinding a second roll 14 or a different, second web 15. The roll changer 10 further comprises a so-called spice device 16 for connecting the first web 13 to the second web 15 via a common splicing point 17 between the two webs 13 and 15. Alternatively, it can be provided that the web 13 or 15 wound up and stored on a roll 12 or 13 already has one or more splicing points 17, ie that at least two different webs are wound up on the roll and can be unwound. The roll changer 10 also comprises a number of guide rollers 3, which determine the path of the web 2 or its transport direction 4. Downstream of the roll changer 10 is a feed mechanism 18, which e.g.serves to regulate the web tension and / or which guides the web edges or the web center, e.g. when two webs of different widths are glued together.

[0040] The web-fed printing press 1 comprises at least one printing unit 20 (cf. Figures 3 , 4 and 5), but preferably a plurality of printing units 20 for the production of multi-color prints. The printing unit 20 is designed as a double printing unit 20, i.e., it comprises a first partial printing unit 21 and a second partial printing unit 22. The printing unit 20 is preferably designed for flexographic printing or gravure printing. The first partial printing unit 21 comprises a first printing cylinder 30, in particular a flexographic or gravure cylinder, and preferably a first screen cylinder 34 for printing a first print image 31 onto the web 2; the second partial printing unit 22 comprises a second printing cylinder 32, in particular a flexographic or gravure cylinder, and preferably a second screen cylinder 35 for printing a second print image 33 onto the web 2. The double printing unit 20 is designed for on-the-fly job changes, ie preferably either the first partial printing unit 21 prints the first print image 31 or the second partial printing unit 22 prints the second print image 33, wherein (cf. Figures 3 and4 ) one of the two printing cylinders 30 or 32 is positioned against a central impression cylinder 36 and the other printing cylinder is positioned away from it. Alternatively (see Figure 5 ) two impression cylinders 36 and 37 are provided. During a job change on the fly, switching takes place between the two partial printing units 21 and 22, for which purpose each partial printing unit 21 and 22 is equipped with a stop device 38. The non-printing partial printing unit 21 or 22 can be prepared for a new print job during production, ie, provided with at least one new printing form.

[0041] The Figures 3 , 4 and 5Each shows a double printing unit 20, to which a web 2 is fed in a transport direction 4 and from which the web 2 is guided further in a transport direction 4 to another unit. Above the double printing unit 20, a superstructure with a number of guide rollers 3 for the web 2 and a dryer 53 for the printed web 2 is provided. The double printing units 20 shown each comprise a first partial printing unit 21 and a second partial printing unit 22, as already described above.

[0042] At least in front of a first double printing unit 20 of the web-fed printing press 1 (if necessary in front of each double printing unit 20, cf. Figure 1) a sensor 40 is arranged. The sensor 40 can, for example, be a web thickness sensor 40 for determining the thickness of the incoming web 2 and / or for detecting a splice 17; or, for example, a reflection sensor which detects an adhesive tape. The web-fed printing press 1 and / or the double-sided printing unit 20 comprises / comprise the computer 55, which is connected to the sensor 40 - preferably via a connection 56. The sensor 40 preferably transmits its measured values continuously to the computer 55, and the computer 55 then sends - after appropriate calculations - control signals 57 (cf. Figure 1 ) to the double printing unit 20 or to the plurality of double printing units 20. In Figure 1In this regard, it can be seen that the control signals 57 preferably cause a plurality of double printing units 20 to switch between the two partial printing units 21 and 22 in succession. In this way, it can be ensured that the switching takes place in coordination with the passage of the splice 17 through the web-fed printing press 1 or its double printing units 20. When switching between the two partial printing units 21 and 22, the pressure / positioning of the printing cylinder 32 to its impression cylinder 36 or 37 and thus to the web can preferably be preset. This presetting can be selected depending on the web thickness of the web 15 following the splice 17; or vice versa. Likewise, the pressure / positioning of the screen cylinder 34 to the printing cylinder 30 during the web change can be preset depending on the passage of the splice 17.

[0043] The double printing units 20 further preferably each comprise a register sensor 41, which is arranged to be adjustable in its measuring position 42; the register sensor 41 can preferably be displaced transversely to the transport direction of the web 2. During a web change, the register sensor 41 can therefore be changed in its measuring position 42—preferably transversely to the web travel direction, i.e., axially—as soon as the splice has passed the register sensor. The control signals 57 or corresponding control signals can also be used for this switching process. A register preset can also be performed during the passage of the splice 17 and during the synchronized switching.

[0044] In Figure 5It is also shown that intermediate dryers 54 can be arranged along the path of web 2 between the two impression cylinders 36 and 37. These intermediate dryers 54 and / or the dryers 53 of the web-fed printing press 1 can also be controlled by the computer 55 during a web change, and the drying parameters can be changed from the first web 13 to the second web 15.

[0045] This change also advantageously occurs at the time when the adhesive point 17 passes the respective dryer.

[0046] The Figure 1 The web-fed printing press 1 shown comprises, in addition to the double printing unit 20, optionally also at least one single printing unit 50, in particular for flexographic or gravure printing. This single printing unit 50 can also be switched on and off and can be controlled by the computer 55 in this regard.

[0047] Furthermore, the web-fed printing press 1 comprises a further unit 51, which can preferably be designed as a rewinder 51 for the printed web 2. In addition to the unit 51 or alternatively, the web-fed printing press 1 can comprise a further unit 52, which can preferably be designed as a finishing unit 52, for example, a punching unit 52. The finishing unit 52 can also be controlled by the computer 55 with regard to a switching process during a web change.

[0048] The figures show, by way of example, the switching from a first web 13 to a second web 15. It is clear that a switching from the second web 15 to the first web 13 can also take place and that a multiple switching to webs 13, 15 and further webs to be processed one after the other can take place. List of reference symbols

[0049] 1Web-fed printing press 2Web 3Guide rollers 4Transport direction 10 Reel changer 11 Unwinder 12 First reel 13 First web 14 Second reel 15 Second web 16 Splice device 17 Splice point 18 Feed unit 20Printing unit(s), in particular double printing unit(s) for flexographic printing 21First partial printing unit, in particular flexographic printing unit 22Second partial printing unit, in particular flexographic printing unit 30First printing cylinder, in particular flexographic printing cylinder 31First print image 32Second printing cylinder, in particular flexographic printing cylinder 33Second print image 34First screen cylinder 35Second screen cylinder 36(Central) impression cylinder 37Further impression cylinder 38Shutdown device and / or setting device 40Sensor, in particular web thickness sensor or reflection sensor 41Register sensor 42Measuring position 50Printing unit(s), in particular single printing unit(s) for flexographic printing 51Additional unit, in particular rewinder 52Optional finishing units 53Dryer 54Intermediate dryer 55Computer 56Connection(s) 57Control signals

Claims

1. A method for operating a web-fed printing press for producing printed products, which comprises a roll changer (10) and a plurality of printing units (20, 50), wherein a flying web change from a first web (13) to a second web (15) is carried out to produce a splice (17), and wherein settings are made on the printing units (20, 50) in accordance with the passage of the splice (17) through the web-fed printing press (1), characterized by thatat least two printing units (20) of the web-fed printing press are each designed and provided as a double printing unit (20) for flexographic printing and are operated for producing printed products, wherein each existing double printing unit (20) comprises a first partial printing unit (21) and a second partial printing unit (22), and that a respective first partial printing unit (21) or second partial printing unit (22) is activated or deactivated in accordance with the passage of the splice (17) through the web-fed printing press (1), or that switching is carried out from a first partial printing unit (21) to a second partial printing unit (22) of the respective double printing unit (20) - or vice versa.

2. Method according to claim 1, characterized by thatthe second partial printing units (22) or their respective flexographic printing cylinders (32) - or in the converse case, the first partial printing units (21) or their respective flexographic printing cylinders (30) - are adjusted to the second web (15) at a speed adapted to the speed of the second web (15) when switching over.

3. Method according to one of the preceding claims, characterized by that the second partial printing units (22) or their respective flexographic printing cylinders (32) - or in the converse case the first partial printing units (21) or their respective flexographic printing cylinders (30) - are adjusted to the second web (15) during switching with a pressure or feed adapted to the second web (15) or its web parameters.

4. Method according to one of the preceding claims, characterized by thatScreen cylinders (35) of the second partial printing units (22) - or, in the opposite case, screen cylinders (34) of the first partial printing units (21) - are adjusted to the flexographic printing cylinders (32) during switching with a pressure or feed adapted to the second web (15) or its web parameters.

5. Method according to one of the preceding claims, characterized by that the second partial printing units (22) or their respective flexographic printing cylinders (32) - or in the converse case the first partial printing units (21) or their respective flexographic printing cylinders (30) - are adjusted to the second web (15) during switching with a pre-register adapted to the second web (15) or its web parameters.

6. Method according to one of the preceding claims, characterized by that the performance of dryers (53) is adapted to the second web (15) or its web parameters when switching over.

7. Method according to one of the preceding claims, characterized by that when switching, a print job change occurs.

8. Method according to one of the preceding claims, characterized by that the flexographic printing cylinders (30) of the first partial printing units (21) - or, in the opposite case, the flexographic printing cylinders (32) of the second partial printing unit (22) - are successively switched off or switched on in accordance with the passage of the splice (17) through the web-fed printing press (1).

9. Method according to claim 8, characterized by that the flexographic printing cylinders (30) of the first partial printing units (21) - or, in the opposite case, the flexographic printing cylinders (32) of the second partial printing unit (22) - are positioned directly in front of the splicing point (17) or positioned directly after the splicing point (17).

10. Method according to one of the preceding claims, characterized by thatthe double printing units (20) each comprise a register sensor (41) and that the register sensors (41) are changed in their respective measuring position (42) in accordance with the passage of the splice (17) through the web-fed printing machine (1).

11. Method according to one of the preceding claims, characterized by that the first path (13) and the second path (15) differ significantly in at least one path parameter.

12. Method according to claim 11, characterized by that the web parameter is one of the following parameters: web thickness, web width, web material, web surface.

13. Method according to claim 11 or 12, characterized by that the web parameter is loaded from a database or from a memory on the web (2) or on the web roll (12, 14).

14. Method according to one of the preceding claims, characterized by thatduring the passage of the splice (17) through the web-fed printing press (1), at least one first partial printing unit (21) is set for a first print job and contributes to the first print job on the first web (13) and that at least one second partial printing unit (22) is set for a second print job and contributes to the second print job on the second web (15).

15. Method according to one of the preceding claims, characterized by that when the web width changes - ie from a first width to a second, larger or smaller width - at least one sensor (40, 41) or another component which is arranged at a working distance from the first width is moved to a safety distance from the second width and from there to a new working distance from the second width.

16. Method according to one of the preceding claims, characterized by thatinstead of the printing units (20, 50) for flexographic printing, printing units (20, 50) for gravure printing with gravure cylinders (30, 32) are used.

17. A method for operating a web-fed printing press, wherein a flying web change from a first web (13) to a second web (15) takes place to produce a splice (17), characterized by that at least two printing cylinders (30, 32) of separate printing units (20, 50) are each positioned away from the first web (13) or positioned on the second web (15) in a manner adapted to the passage of the splice (17) through the web-fed printing machine (1).

18. Method according to claim 15, characterized by that at least one double printing unit (20) or at least one single printing unit (50) is involved in stopping or starting.

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