EP1384580A1 - Method and device for setting registers of a printing press - Google Patents

Abstract

The method involves continuously optically detecting the print product during the printing process and comparing it as an actual print image (9) with a previously stored desired print image (8), whereby if a there is a detected deviation between the desired and actual print images, a suitable adjustment of the register (3) is automatically carried out. AN Independent claim is also included for the following: (a) an arrangement for implementing the inventive method.

Description

Multi-color printing presses have a so-called register arrangement, which is formed from a plurality of individual registers. each this register is used to adjust a printing cylinder for the application of a Printing ink on the carrier medium to be printed.

Numerous different printing processes are known from the prior art, some of which also use different printing ink systems be performed. A color system is the so-called CMYK color system. This ink system uses a total of four inks, namely cyanate (C), Mangenta (M), Yellow (Y) and Black (K). Set from these four inks the colors that are ultimately printed on the print carrier, not mixing these inks within the press takes place, but instead the print carrier, if necessary, four times with each one of the printing inks is printed once. Of course, only those areas of the print medium printed with the respective color that for achieving the overall color combination desired on the print carrier is necessary.

It is necessary to ensure that the print image is flawless to bear that generated by the respective printing sleeves of the individual inks Print images lie exactly on top of each other in the desired way, i.e. one exact overprinting with the different printing inks takes place. Should such an exact overprint cannot be adhered to, so result blur in particular on gradient edges, which also act as fraying or blurring are perceived. In addition, disadvantageously, a mixed color contrary to the specification is insufficient adjust because the intensity is one of those for achieving this mixed color the inks used are too low or too high. In both of the above Cases when the print image of just one ink is not the correct one Place is applied to the print carrier or the job in one only insufficient intensity is carried out, it is disadvantageous an inadequate print image compared to the desired print result, that can no longer be used as waste and must be disposed of.

In order to achieve a desired print image, it is at the beginning of a Printing process required, the printing press with respect to the individual to set the respective printing colors generated printing images. This adjustment process in the run-up to a printing process is called moving off. In the course of this The printer registers the individual registers of the printing press manually set so that the pressure sleeves arranged in the registers provides the desired print image, so that in the composition of the respective individual print images the desired overall print image is created. This adjustment process is used for the sake of reproducibility later on for printing The machine can actually be printed later using the respective one Carrier carried out. Experience shows that with such waste starting a waste, i.e. a committee of in part up to 12% based on the total print volume is produced. Furthermore there may be considerable losses during the printing process Fluctuations in the design of the individual print images, for example through temperature fluctuations, paper quality differences or through changing printing speeds is justified and also to a reject production leads.

Register systems are known from the prior art, which with Raster marks work. These raster marks need a white background and are mostly rectangular boxes, which are printed with one ink each are.

However, there are a number of printed images for which the application of Raster marks are not possible. This is always the case if none There is an outer edge that can later be cut away or that Print image for optical reasons does not allow raster marks.

The aforementioned problem is also exacerbated if not using it of the CMYK color system, but numerous special printing inks are used, for each of which in other registers Pressure sleeve is to be provided. This is the case with napkin printing, for example and admit to using presses that have eight or more registers feature. The setting process of the printing press both during the start-up process as well as during ongoing production is correspondingly complex so that reject production increases disadvantageously.

Starting from the above, it is therefore an object of the invention under Avoiding the disadvantages mentioned above is a procedure for discontinuing the To provide registers of a printing press that while achieving a desired printing result to reduce the waste production helps. Furthermore, the invention is intended to be a device for carrying out the Procedure are proposed.

To achieve the above object, the invention proposes a process in which the Print result recorded optically and as an actual print image with a previously saved one The target print image is compared, in the event of a discrepancy a corresponding one between the target print image on the one hand and the actual print image on the other The registers are set automatically.

According to the invention, the printing result becomes continuous in the current printing process checked. For this purpose, a target print image is stored as a benchmark, that it is necessary to achieve with the current printing process. For a comparison between the reference size predetermined by the target print image on the one hand and on the other hand, the print image actually generated by the printing press this is optically recorded and as an actual print image with the specified target print image compared. If this comparison reveals that there is a discrepancy between the predetermined target print image and the actual print image recorded in the current printing process is present, the register setting of the printing press becomes Correction of this deviation set accordingly. This adjustment process takes place automatically during the ongoing printing process, so that the Printing machine depending on the actual print image actually achieved with the Result is constantly readjusted that the actual print image achieved meets the requirements of Corresponds to the target print image and thus a desired print image is obtained, without the need for manual register adjustment. In Advantageously, the production of rejects during a Reduce printing process significantly.

Another significant advantage of the method according to the invention is that Justified the fact that also caused by a starting process Reject production can be reduced dramatically. Trials have shown that a reduction in scrap production of up to 90% can be achieved. The reason for this enormous reduction in reject production is almost completely dispensing with manual register setting even within the scope of a Starting process of the printing press. The starting point is also here predetermined target print image, the receipt of which is described in more detail below will be. This target print image is with the actual print image, which during the Starting process is optically detected, compared and the resulting Deviations are, as described above, by a corresponding one Register setting compensated. Since it is no longer necessary, manually individual registers of a printing press one after the other, but it on the contrary, it is possible for the optically recorded actual print image to be in its entirety capture and with the reference given by the target print image can compare the register setting for all individual registers in only a very little time-consuming work cycle, so that with the Automatic register setting proposed method according to the invention time-optimized. As a result, the amount of over the course of the Starting process required pressure medium can be reduced so that overall a significantly reduced reject production. Furthermore is the effectiveness and productivity with the inventive method a printing press further improved. Because it is different from that from the manual setting of the register known in the prior art in particular no longer required for the initial setting in the start-up process, time-consuming To provide starting operations. Instead, a time-optimized initial setting take place so that the start of the actual printing process after starting a printing press is achieved much faster. The dead times of one Printing machine, which is caused to a large extent by complex start-up processes can be advantageously reduced to a minimum. This allows more effective use of the printing press, which ultimately results in increased productivity.

Overall, the invention proposes a method that is ongoing Printing process a constant control of what is generated by the printing press Print image carried out and using a predetermined target print image an automatic register setting in such a way that deviations between the actual print image actually generated by the printing press on the one hand and the specified target print image on the other hand be kept as low as possible. The method according to the invention thus helps simultaneous achievement of a desired printing result, the Reduce scrap production. The use of raster marks is for the Implementation of the method according to the invention is not necessary, so that with the procedure a register setting also for such printing processes in is advantageously possible, the use of due to the printed image Exclude grid marks.

To determine the target print image, it is provided according to the invention that the registers the printing press manually in a one-off start-up process can be set and the result of this register setting Print results are recorded optically and saved as a target print image. Intended is therefore to carry out a one-off start-up process manually, the for The print result that was found to be good is then saved as the target print image and as Reference size is used for further printing. It is advantageous it is possible to start the process to determine the target print image and separate subsequent printing processes later. So can For example, a start-up process to determine the target print image is carried out are, this target print image not only following the starting process Printing process, but also subsequent printing processes at different times is available in the same way. Especially with recurring, however, the process according to the invention is advantageous in short print runs, since the target print image specification once recorded and stored again and again used and to achieve a reproducible result again can be used. Once the target print image is available, the Printing machine after any necessary conversion using of the existing target print image as a benchmark within a comparatively time and material-consuming start-up process set become. Another advantage is that the printing results are two from each other Printing processes carried out separately, using the same target print image as a reference variable use, are almost identical, so that quality deviations in Print result even when separated from one another or on different ones Printing operations performed printing machines advantageously not occur. It is also advantageous that the individual registers are activated the printing press not by the number of registers used is limited, so that almost regardless of the number of to be set Register with the inventive method a very fast Register setting can be achieved automatically. The use is manual Work steps to be carried out reduced to a minimum, so that in Difference from the state of the art in the manual work to be performed can be reduced per printing process.

According to a further feature of the invention, the optical detection takes place both the target print image and the actual print image using an image capture unit, preferably a scanner. Another one is also conceivable here Type of optical image capture, for example using a digital camera. The only decisive factor is that the actual printed image is recorded in such a way can be that with regard to the quality characteristics decisive for the printing result Corresponding data usable by a computer unit are supplied become. The actual print image is preferably acquired here line by line, it does not matter that the continuously from the Rather, printing machine issued print media per print image it is sufficient to take the optical print image acquisition at any time to start and depending on the printing speed at a time finish, which is determined by the fact that the print carrier over the length at least a print image in the printing direction of the machine on the image capture unit was passed by. The computer unit connected to the printing press can then the captured print image with respect to the actual print image start or Convert the actual print end so that the desired actual print image for the further implementation of the method according to the invention is available.

According to a further feature of the invention, for a comparison between Target print image and actual print image at least one test area within the print image defined and a comparison between target and actual print image is only based on of this test area. Research has shown that it is for it is not necessary to achieve the desired printing result The target print image and the actual print image in their entirety to compare. Rather, it is sufficient to have characteristic areas of each other to take out the print images to be compared and only a comparison test based on these predefined areas. Such areas are called referred to as so-called test areas, the use of test areas den has great advantage that the inventive method much faster can be carried out. A comparison test between target and actual print images delivers sufficiently precise results based on the test areas so that a Comparison test between target print images and actual print images only on the basis of predefined ones Test area is sufficient to avoid deviations in the desired print result to recognize and make appropriate register settings. In this context, it is proposed that the test area with regard to their size and position within the printed image is defined in such a way that this comprises at least one color boundary running in the printed image. As special A meaningful comparison criterion is particularly suitable for the course of a Color limit, because blurring in the printed image is clearly detected on the basis of this limit and specifications for readjustment of the registers can be calculated exactly can be.

According to a further feature of the invention, the inside of the Color boundary test performed a color boundary analysis, wherein the colors of the printed image detected at the color limit with regard to their composition analyzed from the individual inks in the register become. The aim of the color boundary analysis is that with the optical image acquisition recognized color composition of the printed image in the applied printing inks disassemble. With the color boundary analysis, a "back calculation" is found the printing inks used instead. A comparison of the actual print image and the target print image can now use these inks determined by the color limit analysis be carried out, with a comparison both in terms of by the respective printing color to be produced as well as with respect to the intensity can take place. For example, it can be the result of a color boundary analysis be that the print image generated by a certain ink is incorrectly positioned is applied to the print carrier and, for example, in relation to the the color boundary in the test area is too far to the left. This is recognized by the color boundary analysis, so that a register setting can be such that the print image produced by this printing ink in its Position is shifted slightly to the right, so that in the following The correct printing of the respective print image takes place, which in turn can also be recognized by a color boundary analysis.

According to a further feature of the invention, the registers were set both in the direction of rotation and transverse to it. It is therefore possible that print images generated from the printing sleeves arranged in the respective registers both in the production direction of the printing press, i.e. in the direction of rotation as well as crosswise to adjust so that printed images with respect to each Point can be set in a Cartesian coordinate system. For a precise control of the registers can advantageously be provided be the deviation determined by a color boundary analysis by one or to determine several points in the Cartesian coordinate system exactly and from there to calculate the readjustment of the register. this happens by comparing the respective printing colors from the actual print image and the target print image, the determined deviations within the Cartesian coordinate system can be converted and as a result the setting of the respective one necessary to eliminate this deviation Deliver registers. It goes without saying that this is not just a Cartesian Coordinate system but also other coordinate systems can be used can, the use of a Cartesian coordinate system as has shown particularly advantageous.

According to a further feature of the invention, an upstream Process step determines the color intensity of the printing inks in the register. This is preferably done by a separate imprint of the individual colors in the register. These can then be obtained from the image acquisition unit recorded and stored in terms of their intensity as a reference variable become. This upstream process step is preferably carried out at a only carried out reduced speed of the print carrier, so that the production of rejects can be kept low. Just like the one-off start of the printing press for determining a target print image is also the determination the color intensity only once. The results obtained can, however, continue for a variety of downstream printing processes be used.

With regard to the device is a to solve the aforementioned problem Device for performing the method proposed, with an optical Image acquisition unit, preferably a scanner, a storage unit and a control device that continuously uses the image capture unit to print the image recorded during the printing process and that with a comparison unit the captured actual print image with the one stored in the storage unit Comparing the target print image and, if the values are not equal, a corresponding setting the register makes.

The essential components of the device according to the invention are the image acquisition unit, the storage unit and the control device. With the help of Image capture unit, the current print image is captured. This actual print image is compared to a target print image using the control device, that is determined in a start-up procedure previously carried out and as a reference variable is available and stored in the storage unit is. The comparison between the actual print image and the target print image is used of the above-described method according to the invention, wherein in If an inequality is found, the control device of the invention Device ensures that a control element provided for this purpose makes a corresponding setting of the register of the printing press, so that the inequality between the actual print image on the one hand and the target print image on the other is balanced.

Further features and advantages of the invention result from the description with reference to Figure 1. This shows a schematic representation of the Device according to the invention for performing the invention Process.

1 schematically shows a print carrier 1, for example a paper web, by means of transport rollers 2 through the not shown Printing machine 11 is transported. The printing press 11 includes one Control device 13, which in turn is a scanner 4, a comparison unit 5 and a storage unit 7. The scanner 4, the comparison unit 5 and the storage unit 7 are in communication with one another Connection, wherein the scanner 4 on the print carrier 1 from the Printing machine applied optically detected print image 12 and as an actual print image 9 the comparison unit 5 transmits. The storage unit 7 transmits to the Comparison unit a target print image 8, so that the comparison unit 5 in one Comparison test of the actual print image 9 supplied by the scanner on the one hand and that of the target print image 8 supplied to the storage unit 7 on the other hand can compare.

In the event that the comparison unit 5 a deviation between the actual print image 9 and the target print image 8 are determined, the register arrangement is triggered 10 3. Those registers of register arrangement 3 are set here their printing colors or the resulting individual print images as different were recognized by the target print image 8. A setting of the individual registers the register arrangement 3 can here both in the direction of rotation 6 Direction of transport of the print medium 1 and transversely thereto, so that a Readjustment of the registers of the register arrangement 3 in order to achieve a Desired print image 12 can be performed exactly.

The printing press 11 equipped with the device according to the invention allows using the method according to the invention advantageously a time-optimized readjustment of the register arrangement 3, so that a reject production due to an adjustment of the register arrangement 3 in progress Printing process as well as in particular during a start-up process advantageously can be prevented. This increases productivity and effectiveness of the printing press 11.

LIST OF REFERENCE NUMBERS

1

print carrier

2

transport wheels

3

register arrangement

4

scanner

5

comparing unit

6

direction of rotation

7

storage unit

8th

Target print image

9

Actual print image

10

control

11

press

12

print image

13

control device

Claims (12)

Method for setting the register (3) of a printing press (11), at the continuously the printing result during the printing process optically recorded and as an actual print image (9) with a previously stored one Desired print image (8) is compared, in the event of a detected deviation between the target print image (8) on the one hand and the actual print image (9) on the other the registers (3) are automatically set accordingly. A method according to claim 1, characterized in that the registers (3) of the printing press (11) are set manually to determine the target print image (8) and the print result resulting from this register setting is optically recorded and stored as the target print image (8) becomes. Method according to Claim 1 or 2, characterized in that the target print image (8) is determined in the course of a one-off start-up process of the printing press (11). Method according to one of claims 1, 2 or 3, characterized in that the optical detection of both the target print image (8) and the actual print image (9) takes place by means of an image capture unit (4), preferably a scanner. Method according to one of the preceding claims, characterized in that for a comparison between the target print image (8) and the actual print image (9) at least one test surface is defined within the print image (12) and a comparison between the target and actual print image ( 8, 9) is only carried out on the basis of this test area. Method according to one of the preceding claims, characterized in that the size and position of the test area within the print image (12) is defined in such a way that it comprises at least one color boundary running in the print image (12). Method according to one of the preceding claims, characterized in that the test area is defined automatically. Method according to one of the preceding claims, characterized in that a color boundary analysis is carried out on the basis of the color boundary running within the test area, the composition of the colors of the printed image (12) recorded at the color boundary being analyzed with regard to their composition from the individual printing inks in register (3) , Method according to one of the preceding claims, characterized in that a target-actual comparison of the printed images (12) is carried out on the basis of the printing inks determined by the color limit analysis. Method according to one of the preceding claims, characterized in that the registers (3) are set both in the direction of rotation (6) and transversely thereto. Method according to one of the preceding claims, characterized in that the color intensity of the printing inks in the register (3) is determined in a preceding process step. Device for carrying out the method according to one of the preceding Claims 1 to 11, with an optical image acquisition unit (4), preferably a scanner, a storage unit (7) and a control device (13) which, with the image capture unit (4), the print image (12) continuously recorded during the printing process and with a comparison unit (5) the captured actual print image (9) with that in the storage unit (7) stored target print image (8) compares and in case of inequality the registers (3) are set accordingly.

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