Patent Publication Number: US-11639069-B2

Title: System and process for mounting a printing plate on a carrier

Description:
The present application is a continuation of U.S. patent application Ser. No. 16/319,108 (status: allowed), filed 18 Jan. 2019, which is a national phase submission under 35 U.S.C. § 371 of PCT Application Ser. No. PCT/EP2017/068385, titled SYSTEM AND PROCESS FOR MOUNTING A PRINTING PLATE ON A CARRIER, filed 20 Jul. 2017, which claims priority from U.S. Provisional Application No. 62/365,041, titled PROCESS FOR MOUNTING A PRINTING PLATE ON A CARRIER, filed on 21 Jul. 2016, the contents of both of which are incorporated herein by reference in their entirety for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     In commercial printing, the occasion arises where it is desired to mount a relatively smaller printing plate on a relatively larger carrier sheet, such as for using the plate on a press. U.S. Pat. App. Ser. No. 20110308411 (“the &#39;411 Publication), owned by the assignee of the present invention and incorporated herein by reference, describes a process for creating one or more imaged segments from a full size printing plate sheet, marking each segment with non-printing registration marks, and mounting the segments onto a mounting material using the registration marks for alignment. 
     U.S. Pat. No. 6,954,291, also owned by the assignee of the present invention and incorporated herein by reference, describes a plurality of plate “patches” having a size less than a full size plate that may be disposed on a single carrier having a size of the full size plate to save on printing plate material costs. The process for mounting each patch comprises printing indicia, such as corner marks, on the carrier sheet to mark where each patch should be affixed. The workflow for creating such patching is well established, such as using Esko&#39;s PlatePatcher™ module that is offered as a part of its Digital Flexo Suite. PlatePatcher analyses large bitmap files to create small plate slugs with printing information. The mounting locations are then sent to the Kongsberg (Plot &amp; Cut workflow) software for marking the corner marks for mounting the plate on the carrier sheet. The carrier sheet may then be cut to a desired size after the plate has been mounted. 
     In certain workflows, however, such as those that require mounting a large (e.g. greater than 1 meters in dimension on one or more sides) plate on a carrier sheet, the workflow as described above, comprising creating registration marks on the plate, using those registration marks to align the plate on the carrier relative to marks on the carrier, then cutting the carrier, may result in significant misregistration if the plate is not precisely aligned on the carrier prior to cutting, thereby causing unacceptable defects in the print job. Additionally, achieving precise alignment may be very difficult for relatively large plates. Accordingly, a superior workflow is needed. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention comprises a process for mounting a printing plate having a first periphery on a carrier sheet having a second periphery that surrounds the first periphery. The process comprising the sequential steps of first, providing registration indicia—typically a plurality of at least two registration marks—on the printing plate, then placing a carrier sheet on a cutting table of a cutting system, mounting the printing plate to the carrier sheet, and detecting with the cutting system absolute coordinates of the registration marks on the printing plate. The carrier sheet is then cut along a cut line having absolute coordinates generated based upon the detected absolute coordinates of the one or more printing plate registration marks. A cut file associated with the printing plate may be generated, and an identifier of the file provided on the printing plate. The cut file comprises a plurality of machine readable instructions for controlling the cutting system for carrying out the steps of detecting the registration marks and cutting the carrier sheet based upon those marks, including relative coordinates for location of the cut line based upon relative coordinates of the printing plate registration marks. 
     In one embodiment, the process may include the step of, after placing the carrier sheet on the cutting table, disposing on the carrier sheet a plurality of corner indicia marking approximate corners of the carrier sheet to be cut. If inspection of the carrier sheet shows that one or more of the plurality of corner indicia are disposed outside of the carrier sheet, placement of the carrier sheet is adjusted and the corner indicia are regenerated. Then, after the carrier sheet is confirmed to be properly placed, the process comprises disposing on the carrier sheet plate mounting indicia marking an approximate location and orientation for mounting the printing plate. The cut file may include corresponding instructions for performing the foregoing steps of this embodiment, as well as absolute coordinates for location of the corner and plate mounting indicia to be marked on the carrier sheet. 
     Aspects of the invention include the processes described herein, systems comprising processor memories programmed with instructions for performing the processes described herein, and computer readable media containing the instructions for performing the processes described herein 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an exemplary plate making and cutting table system and its workflow in accordance with one embodiment of the invention. 
         FIG.  2    illustrates an exemplary carrier sheet and mounted printing plate in accordance with one aspect of the invention. 
         FIG.  3    illustrates an exemplary carrier sheet prior to mounting a printing plate in accordance with another aspect of the invention. 
         FIG.  4    illustrates the exemplary carrier sheet of  FIG.  3    with the printing plate mounted thereon. 
         FIG.  5    is a flowchart depicting an exemplary workflow corresponding to one aspect of the invention. 
         FIG.  6    is a flowchart depicting an exemplary workflow corresponding to another aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures,  FIG.  2    illustrates the arrangement of the plate and the carrier sheet in a first embodiment of the invention in accordance with the flowchart of  FIG.  5   , depicting a first exemplary process workflow. Printing plate  200  has a periphery that is surrounded by the periphery of carrier sheet  100 . In an exemplary workflow, in step  410 , indicia, namely a plurality of registration marks  202   a - 202   d,  comprising at least two registration marks, such as marks  202   a  and  202   c,  are disposed on the printing plate. These registrations marks are detectable by a camera (not shown) of a cutting table, such as a Kongsberg cutting table, from Esko-Imaging Graphics GmbH of Itzehoe, Germany. Although depicted as visible cross marks in  FIG.  2   , the registration marks may have any characteristics suitable for detection. Although not limited to any particular type of indicia or process for making them on a plate, U.S. Pat. No. 6,954,291, referenced above, describes an exemplary process for marking printing plates with exemplary registration marks. 
     Carrier sheet  100  is then placed on a cutting table of a cutting system (not shown) in step  420 , and printing plate  200  is mounted to the carrier sheet (such as with adhesive or any means for fixation known in the art) in step  430 . The camera of the cutting system then detects the coordinates of the registration marks on the plate in step  440 , a processor connected to the camera and the cutting system automatically determines the coordinates for the cut line based upon the coordinates of the registration marks, and then, in step  450 , the cutting system cuts the carrier sheet along cut line  110  based upon the detected absolute coordinates of the plate registration marks, which define the location and orientation of the printing plate. Thus, in contrast to the prior art process, in which the cutting system prints indicia for alignment of the plate on the carrier, and then performs the cutting step based upon an expected location of the plate, under the assumption that the plate has been sufficiently well aligned relative to those corner marks, the process described herein cuts the edges of the carrier sheet based upon the actual detected orientation of the plate as detected by the location of the registration marks on the plate, thereby ensuring perfect alignment between the image features on the plate and the edges of the carrier sheet. 
     Although shown with four registration marks in  FIGS.  2  and  4   , it should be understood that various registration systems are known, and that anywhere from two to four registration marks are typically used. As is known in the art, a registration mark having certain characteristics (such as a cross shape) may enhance detection of location and orientation of each mark. The invention is not limited to any particular number or shape of plate registration marks. As used herein, the term “registration indicia” may refer to a single mark or any number of marks. 
     In the aforementioned process, a cut file is generated and uniquely named that comprises a plurality of machine readable instructions for controlling the cutting system for carrying out the process. The cut file is typically generated at approximately the same time as the plate is marked with the indicia, but may be created before or afterwards, and contains the coordinates for locating the cut line relative to the locations of the printed registration indicia on the plate. The cut file is then associated with the printing plate, such as for example, by marking the plate with the unique name for the cut file and saving the cut file by the name in computer memory. After the printing plate has been mounted on the carrier sheet, the cut file is retrieved from memory and activated, and the instructions are carried out by the cutting system to detect the registration marks, generate the absolute coordinates for the cut line based upon the detected absolute coordinates of the printing plate registration marks and the relative coordinates in the cut file, and then cut the carrier sheet along those coordinates. 
     The process described above may be perfectly suited for a workflow in which the distances between the cut line and the periphery of the uncut carrier sheet and between the periphery of the plate and the periphery of the uncut carrier sheet are relatively large, such that misalignment of the carrier sheet on the cutting table and/or misplacement or misalignment of the plate on the carrier sheet relative to expected locations does not risk the cut line falling outside the periphery of the carrier sheet. A more foolproof embodiment, however, may be preferred for certain jobs, such as those in which the aforementioned distances are not so large, and misalignment of the carrier sheet on the cutting table would indeed risk the cut line falling outside the periphery of the carrier sheet. As this more foolproof embodiment contains additional steps, which will require more time per work piece, workflows may be tailored with or without these additional steps based on the commercial realities of the job being implemented. Referring now to  FIGS.  3  and  4    in accordance with the flowchart of  FIG.  6   , a second exemplary process workflow is illustrated conforming to this more foolproof embodiment. 
     In the second exemplary process, after disposing the plurality of registration marks  202   a - 202   d  on the printing plate in step  510  and placing the carrier sheet on the cutting table in step  520 , the cutting system, in accordance with step  530 , places on the carrier sheet corner indicia  102   a - d  marking the approximate corners of the expected cut line based upon an expected location for placement of the printing plate. In step  540 , the carrier sheet is inspected to determine whether performing step  530  has resulted in one or more of the approximate corner indicia disposed outside of the carrier sheet, and if so, the workflow reverts to step  520 , the orientation of the carrier sheet is adjusted, and step  530  is repeated. Although shown as small dots  102   a - d,  the corner indicia may have any shape or size. The carrier sheet is inspected again in step  540 , and the workflow is not advanced until performance of steps  520  and  530  results in all of the approximate corner indicia disposed on the carrier sheet. Then, in step  550 , the cutting system marks the carrier sheet with plate mounting indicia  104   a - d  identifying an approximate location and orientation for mounting the printing plate. Although shown as four corner marks (short lines abutting at a 90 degree angle, each oriented to align with the edges of the placed printing plate), the indicia may take on any shape, size, and number. For example, the indicia may comprise a single marking comprising the full outline of the plate to be mounted. 
     In step  560 , the printing plate is mounted in approximate alignment with the plate mounting indicia on the carrier sheet, as shown in  FIG.  4   , and in step  570 , the camera detects the absolute coordinates of the registration marks  202   a - d  on the plate. In step  580 , after processing the absolute coordinates of the registration marks as detected to determine the absolute coordinates of the cut line, the cutting system cuts the carrier sheet along the cut line  110 . A suitable cut file may also contain the instructions for carrying out the steps of this embodiment, including for marking the carrier sheet as described above, and also contains the relative coordinates for the cut line based upon the relative coordinates of the registration marks, as well as absolute coordinates for the four approximate corner marks and for the indicia for approximately aligning the plate on the carrier sheet. 
     In operation, the carrier sheet is placed on the cutting table, the cut file identifier (read from the printing plate) is entered in the cutting system, the cut file is located and activated, and instructions from the cut file are processed by a processor associated with the cutting system. If the cut file includes instructions for marking the carrier sheet, the four corner indicia are marked, and the system waits for confirmation that the corners are disposed on the plate before advancing to the next set of instructions in the file. If the markings are not all disposed on the carrier sheet, the sheet is repositioned, and the corner marking instructions are re-run. Then the indicia for approximately aligning the plate are printed, and the system waits for confirmation that the plate has been mounted before advancing to the next set of instructions. Upon receipt of that confirmation, the system then locates the registration marks and cuts the carrier sheet based upon the location and orientation of the registration marks. In a typical operation, a human operator may perform the steps of placing the carrier sheet on the cutting table, reading and entering the cut file name into the cutting system, checking to ensure the four corner indicia appear on the carrier sheet, and mounting the plate to the carrier sheet, and may provide a signal to the cutting system when each of these steps has been performed, to permit the system workflow to move to the next set of programmed instructions (or to revert back to a prior step, if necessary). It should be understood, however, that each of these steps may be made fully automatic or partially automatic, and that the human operator may rely on various machines and equipment known in the art to provide assistance in performing each step. 
     Cutting systems, including the computer systems associated therewith, including processors, memory, and various physical and virtual connections between them to permit communication between the various parts of the system, are well known in the art, as are workflow for making printing plates and mounting them on carrier sheets. Accordingly, many of the details that will be well known to those of skill in the art are not repeated here, but exemplary embodiments of such workflows and systems are specifically incorporated by reference via the patents mentioned above. Aspects of the invention include systems comprising processor memories programmed with instructions for performing the processes described herein, as well as computer readable media containing such instructions. 
       FIG.  1    depicts an exemplary workflow relevant to the present invention. Imager  133  may be configured for direct-to-plate printing on sheets that have an ablatable mask material thereon. In the case of non-direct-to-plate imaging, the imager exposes a mask, e.g., a photographic mask. The workflow also includes a UV exposer and washer  135  that is used to cure the sheet with a mask thereon by exposing the front of the plate with the mask thereon to UV radiation. In the case of direct-to-plate imaging, the sheet of plate material (after back-radiation) is imaged on the imager. In the case of non-direct-to-plate imaging, the UV exposer and washer  135  includes a mechanism to place a mask on the front of the plate prior to exposure, and it is the mask that comes from the imager and placed with the sheet of plate material after back-exposure. 
     An exemplary cutting system includes a cutting table  137 , such as but not limited to an Esko Kongsberg-Table (X-Table), which typically includes a tool holder  139  and is operably controlled according to x-y control data. In some embodiments, the x-y table can operate one of a set of tools in the tool holder  139  under control of the x-y control data, including selecting a tool of the set. As an example, one tool of the set may be a cutting tool, such as a milling spindle or a knife head, making the x-y table  137  operative to cut segments from a sheet placed on the table according to x-y control data that includes the cutting data  123 . The x-y table  137  may include a laser positioning tool and in some embodiments, one or more video cameras. The positioning tool and/or the video cameras or both are used to accurately register the position of a sheet of plate material placed on the cutting table. The set of tools  139  may include a marking tool, which depending of the embodiment, can be laser tool, a knife tool, a drill tool, or a pen tool, that may be used for placing registration marks on a plate or carrier sheet placed on the table  137 . In some embodiments, for example, the imaging data includes one or more registration marks on the printing plate that are exposed to produce visible registration marks on the plate. By registering to the registration marks on the plate, the imaging data  121  and any x-y control data, e.g., mounting data  127  for mounting a printing plate on a carrier sheet, marking data  125  for marking the carrier sheet with a marking tool, and cutting data  123  for cutting the carrier sheet with a cutting tool can all have the same frame of reference on the surface of the sheet when placed on the x-y table  137 . 
     While  FIG.  1    shows a controllable x-y table for cutting, any controllable cutting device can be used for cutting. After the printing plate has been mounted on the carrier sheet, it may then be used in a printing press  143  to make desired printed matter. 
     An exemplary system for mounting a printing plate in accordance with the process disclosed herein comprises at least a cutting system, such as that shown in  FIG.  1   , comprising a cutting table  137  for receiving a carrier sheet, a camera (not shown) operable to detect registration marks on a printing plate, a processor for processing coordinates of the detected registration marks and for calculating coordinates for cutting the carrier sheet based upon the detected registration mark coordinates, a cutter (e.g. a cutting tool placed in tool holder  139 ) for cutting the carrier sheet, and a controller for controlling the cutting system based upon programmed instructions. The cutting system also includes a computer memory, readable by a machine, and programmed with instructions for instructing the cutting system controller. The processor, controller, and memory are typically part of an integrated processing system that may have a workstation operated by a human user, such as workstation processing system  131  depicted in  FIG.  1   . 
     The programmed instructions may include at least programming for carrying out the following steps: 
     a. detecting with the cutting system camera absolute coordinates of one or more registration marks on the printing plate when mounted on the carrier sheet; 
     b. calculating absolute coordinates for the cut line based upon the detected absolute coordinates of the one or more printing plate registration marks in accordance with stored relative coordinates for location of the cut line based upon relative coordinates of the registration marks; and 
     c. cutting the carrier sheet along the cut line. 
     The cutting system is also preferably integrated with a plate maker (e.g. imager  133 ) programmable to place the one or more registration marks on the printing plate, in which case the programmed instructions further comprise instructions for placing the one or more registration marks on the printing plate and for defining the relative coordinates for location of the cut line based upon relative coordinates of the registration marks. A typical cutting system also typically has means for placing indicia on the carrier sheet, such as any of the marking tools in tool set  139 , described above. The marking means may also be an ink jet printer module operable to dispose ink in accordance with programmed instructions. Non-ink indicia may be created using cuts or scores or drill holes made by a cutting or drilling tool or by marks made by a laser, and the marking means may also be a pen (or pencil) tool, comprising a point or stylus that makes physical contact with the carrier sheet, and any and all means for creating marks on a carrier sheet known in the art equivalent to the foregoing. Thus, to carry out the embodiment described in  FIG.  6   , the system may also comprise programmed instructions for disposing on the carrier sheet a plurality of corner indicia marking approximate corners of the carrier sheet, and disposing on the carrier sheet plate mounting indicia marking an approximate location and orientation for mounting the printing plate. 
     Aspects of the invention also include computer readable media containing programmed instructions for controlling a cutting system to facilitate the processes disclosed herein, such as: 
     a. instructions for defining relative coordinates for location of a cut line on the carrier sheet based upon relative coordinates of one or more registration marks on the printing plate; 
     b. instructions for detecting with the cutting system absolute coordinates of the one or more registration marks on the printing plate when mounted on the carrier sheet; 
     c. instructions for calculating absolute coordinates for the cut line based upon the detected absolute coordinates of the one or more printing plate registration marks and the relative coordinates for location of the cut line based upon the relative coordinates of the one or more printing plate registration marks; and 
     d. instructions for causing the cutting system to cut the carrier sheet along the cut line. 
     The programmed instructions may also include instructions for disposing on the carrier sheet a plurality of corner indicia marking approximate corners of the carrier sheet, instructions for disposing on the carrier sheet plate mounting indicia marking an approximate location and orientation for mounting the printing plate, and instructions to cause a plate maker to place the registration marks on the printing plate. In an exemplary embodiment, the instructions for causing the plate maker to place the registration marks on the printing plate may comprise a module in the Esko PlatePatcher software that provides instructions for making a single, large plate with such registration marks (rather than multiple small plate pieces, as disclosed in the &#39;291 patent and as heretofore delivered using the PlatePatcher software). The invention is not limited to any particular process for providing the registration marks on the printing plate, however. 
     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.