Systems and methods for designing and creating printed versions

Abstract

A method for designing a printing plate to be mounted on a printing cylinder. By applying an energy minimization function, an optimal lateral seam path is defined between opposite lateral edges of the plate. The top and bottom edges of the plate are defined based on the optimal lateral seam path, preferably with a variable gap therebetween, and the bottom edge unfolds from the top edge to define a closed cutting path. The area within the closed cutting path is wrapped with the original image or a portion thereof, and an updated digital graphic file is stored. The energy minimization function may include a penalty function with weighting factors, a total seam path length, and a seam path amplitude. For an original image including staggered channels of a stepped and repeated single design image, the optimal lateral seam path may extend across the single design image, the steps between adjacent single design images, or a combination thereof on each channel.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 029,978, filed May 26, 2020, entitled "SYSTEM AND METHOD FOR DESIGNING AND CREATING A PRINTING PLATE", the content of which is incorporated herein by reference. Background Art

[0003] In flexographic printing on a continuous web, such as in the field of flexible packaging or label printing, a "single design" (a single sample of the complete design to be printed), sometimes also referred to herein as a "station", is not web - wide. Thus, multiple copies of the same (or different) single design are printed in multiple lanes side - by - side. An exemplary printing sleeve 120 on a printing cylinder 112 is depicted in FIG. 1A, which has three lanes 114 with a single design 116. If the single designs in all lanes are "in - phase", as depicted in FIG. 1A, then when the cylinder moves in the machine direction along arrow Y, the risk of mechanical vibration will increase, and such vibration may have a negative impact on print quality. Therefore, it is more desirable to align the single designs in a staggered manner, where the single designs in multiple lanes on the printing cylinder are out - of - phase offset relative to each other.

[0004] When using a flexographic printing sleeve 120 such as depicted in FIGS. 1A and 1B, the staggered layout can be imaged directly as needed. However, a flat flexographic printing plate 130 is often used, such as depicted in FIGS. 1C and 1D, which has a lateral (or horizontal) width C defined between the lateral edges of the cylinder w and a nominal length Cc (or vertical height) defined between the top and bottom edges 131, 132 and corresponding to the circumference of the cylinder. The term "vertical" as used herein refers to the machine direction Y, consistent with the illustration. The artwork can be oriented in any direction, and the use of the term "vertical" only refers to the machine direction and not any reference direction of the artwork itself. The vertical height / nominal length dimension L of the printing plate corresponds to the circumference of the printing cylinder 112. When the flat plate 130 is wrapped around the printing cylinder 112, the adjacent edges 131, 132 of the wrapped plate form a seam 134. Attempting to print inked content that extends continuously across the seam is technically undesirable. Thus, a straight seam without one or more inflection points is generally not an option for a staggered layout, meaning the plate needs to be imaged and cut according to a non - straight seam (such as seam 134) having one or more inflection points.

[0005] Producing an intercut flexible printing plate presents several challenges. Plates with non-rectangular top and bottom edges typically result in relatively more waste of flexographic material compared to plates with rectangular top and bottom edges. Determining the optimal plate cutting path is a time-consuming operation, even for a skilled operator. The risk of damaging the plate during cutting, mounting, and dismounting generally increases with the complexity of the cutting path.

[0006] A single print production run (color) typically requires multiple flexible plates, one for each print color separation. To ensure print registration, all color separation plates must follow the same intercut layout, but this does not necessarily mean that they are all cut into the same shape.

[0007] Near the side of the cylinder, some space is typically reserved for production marks for (inline) quality / process control, or for bearer bars (a portion of the plate material whose maximum height is above the floor outside the original image to help spread the printing pressure). Defining the cutting path must also take into account the position of the seams relative to these marks to ensure that they can still perform their intended functions.

[0008] Historically, the most common practice has been for the seams to follow the edges / spaces between single designs, as depicted in FIGS. 1C and 1D, in which case the plates for all print color separations can use the same cutting pattern. However, if a color separation has sufficient blank space 202 (an area between printable features 204, 206 where no ink transfer is desired) in the design, the seam 234 can travel through the single design, as depicted for plate 200 in FIGS. 2A and 2B. Notably, each single design 210 is shown as having a defined boundary 212 that does not include printable content but can represent, for example, the seam path along which the printed content will ultimately be cut to form a single instance of a printed sample, such as a label. The ability to create seams through single designs can enable the use of less complex plate shapes, which results in less material waste and can also have other benefits. In the example of the color separation depicted in FIGS. 2A and 2B, plate 200 has top and bottom edges that are relatively more nearly straight lines than a line that only extends through the gap between adjacent single designs, and the position of these edges does not interfere with print quality.

[0009] Referring now to the flowchart of FIG. 3, an exemplary method 300 for producing a plate with interleaved content (wherein single designs in adjacent channels are vertically offset from each other) includes, in step 310, preparing an interleaved pattern of plate contours and cutting paths for each color separation digitization and storing the prepared content in a step-and-repeat graphic file. In step 320, a raster image processor (RIP) processes (ripes) the step-and-repeat graphic file. In step 330, plate merging software is typically used to determine the best way to layout the plate on the available plate material for each color separation. Some software (such as the Digital Flexo Suite from BVBA EskoSoftware TM software) will ignore the ripened data outside the plate cutting path (if not removed by a masking step), thus allowing for closer nesting of patches or plates when creating the plate material. Then, as determined by the plate merging software, in step 340, the plate material is imaged and processed, and then in step 350, an automated cutting table is typically used to cut the processed plate material into the desired flexographic plate(s) according to the defined cutting boundaries. Then, in step 360, the cut plate is mounted on a printing cylinder (or an intermediate carrier) in preparation for printing.

[0010] Current methods for creating a plate layout on a cylinder can use an algorithm to automatically find a path between single designs, such as the seam path that results in seam 134 in FIG. 1D. This path is then typically used for all color separations.

[0011] In other embodiments, an operator can use manual tools to draw / modify the seam path (which can be different for each printing color separation), such as the seam path that results in seam 234 depicted in FIG. 2B. Thus, the manual method of achieving an optimal cutting pattern still requires a skilled operator and additional time, while the automated alternative results in more plate material waste. Therefore, it remains an important goal to more effectively provide a plate design that minimizes plate material waste with a minimum of operator time.

[0012] Some existing methods (such as the method described in U.S. Patent No. 8,477,380 B2) involve a method in which the plate material is cut into an identified pattern and then mounted on an imaging cylinder for imaging. Other methods (such as the methods implemented in products such as Esko etc.) first image the plate and then cut the plate into a cutting shape.

[0013] While the method for determining a seam line proposed in U.S. Patent No. 8,477,380 states that a seam cutting line can be generated in the non-imaged area within an image element, and that a minimum acceptable distance is maintained between the seam cutting line and the imaged area, the method optimizes the seam cutting line by minimizing the length of the seam cutting line. However, merely seeking to minimize the length of the line may not provide the overall best seam line. In fact, in some cases, using the minimum distance from the original image and the minimum length of the cutting path as the sole criteria for optimization may not produce a solution at all. In other cases, although the line stays outside the minimum distance from the original image, that minimum distance may still be unnecessarily close to the original image.

[0014] When selecting a cutting path that extends through the original artwork, it is desirable to consider not only the increased risk that the cut through the artwork may be visible in the printed result, but also other risks. For example, the original artwork that is very close to the cutting edge is more likely to be damaged during cutting, mounting, or dismounting. Therefore, in at least some parts of the design, it may be more desirable to place the seam path further away from the original image than the minimum distance. It may also be important to avoid having unnecessary sharp corners in the cutting path, because sharp corners are difficult to cut and there are weak points where the plate will tear during dismounting. In addition, some operators prefer to have a gap at the seam to make it easier to insert a tool to dismount the plate from the cylinder. Finally, it may be desirable for the seam to avoid interfering with the intended function of production marks or support bars.

[0015] Although there is software (such as Plato TM ) that helps prepare a cylinder layout with an interleaved design and a plate cutting path for color separation, existing automatic algorithms may not produce the best cutting path, and the manual workflow is very time-consuming and requires experienced operators. SUMMARY OF THE INVENTION

[0016] One aspect of the present invention includes a method for designing a printing plate having a plate width defined between lateral edges and a nominal plate length defined between top and bottom edges. The printing plate is configured to be mounted on a printing cylinder having a cylinder width and a cylinder circumference, wherein the nominal plate length dimension corresponds to the cylinder circumference. The method includes the steps of: (a) preparing an initial digital graphic file including an original image; (b) defining an optimal lateral seam path between opposite lateral edges of the printing plate by applying a minimum energy path finding algorithm, such as an energy minimization function; (c) defining the top and bottom edges of the plate; and (d) unfolding the bottom edge from the top edge to define a closed cutting path that includes the top edge, the bottom edge, and opposite side edges connecting the top and bottom edges of the plate. The area defined by the closed cutting path is then wrapped with the original image or a portion thereof; and the updated digital graphic file is stored. The original image outside the closed cutting path may be removed in a masking step before saving the updated file.

[0017] The top and bottom edges may be defined to enclose a gap, the gap width of which is equal to or less than the maximum gap width on opposite sides of at least a portion of the optimal lateral seam path, and the gap may have a variable gap width along the length of the optimal lateral seam path, which means that the top and bottom edges may not be geometrically identical. The method may include smoothing the optimal lateral seam path and / or the top and bottom edges to minimize the number of inflection points and maximize the radius of the inflection points.

[0018] The original image may include a plurality of production marks, and one or more channels of a single design image or a portion thereof are arranged in a step-and-repeat pattern along the length of the printing plate, wherein the one or more channels are distributed across the width of the plate. Each single design image has a top boundary, a bottom boundary, and opposite lateral edges, and there is a step between each bottom boundary of a first single design image and the adjacent top boundary of a second single design image in the same channel. In such an embodiment, the optimal lateral seam path is defined to travel through one or more single design images, the steps between adjacent single design images, or a combination thereof in each channel. In an embodiment having at least two channels, the top boundary of the uppermost complete single design image in the first channel is offset from the top boundary of the corresponding uppermost complete single design image in the second channel.

[0019] The energy minimization function can include a proximity metric and one or more curve metrics, such as, for example, an energy minimization function including a proximity penalty function P integrated along a seam path, such as a penalty function configured to assign the highest penalty to proximity within or at a minimum distance from a printed feature of the original image, the lowest penalty to proximity beyond a desired distance from the printed feature, the desired distance being greater than the minimum distance, and a variable penalty within a range between the minimum distance and the desired distance. In an embodiment where the original image includes a die line and a bleed area, the penalty function can be configured to assign a relatively greater penalty to printed features within the die line than to printed features within the bleed area. The proximity penalty function also includes one or more centerline corridors corresponding to a centerline between die lines, where the penalty assigned to the centerline corridors is relatively lower than the penalty assigned based on proximity to the bleed area. The energy minimization function can include minimizing the total seam path length and / or minimizing the seam path amplitude as optimization criteria, and can include weighting factors for weighting the penalty function, the total seam path length, and the seam path amplitude. The penalty function can be a pixelated penalty function.

[0020] The steps for determining an optimal lateral seam path and a closed-plate seam path as described above can be performed for each of a plurality of color separations corresponding to a digital graphic file. The step of defining an optimal lateral seam path includes: defining a plurality of potential lateral seam paths that meet a seam path criterion within a predetermined deviation degree, providing a visual display depicting the plurality of potential lateral seam paths, and receiving user input selecting one of the plurality of potential lateral seam paths as the optimal lateral seam path.

[0021] A first initial digital graphic file can be provided having a first interleaving distance between complete single designs in adjacent channels, the method steps can be performed to define an optimal lateral seam path corresponding to the first interleaving distance, and then the method steps can be performed again for a second interleaving distance different from the first interleaving distance to define a second optimal lateral seam path corresponding to the second interleaving distance. The remaining steps of the method can be performed using one selected from the first or second interleaving distances.

[0022] Another aspect of the present invention includes a process for creating a printing plate, including the steps of: designing a printing plate according to the method described herein, imaging the printing plate according to an updated graphic file; exposing and processing the printing plate; and cutting the printing plate according to a closed cutting path. The process is preferably sequential, where the imaging, exposure, and processing steps are performed before cutting the printing plate. The imaging step can be performed after merging more than one printing plate onto a merged intermediate plate, in which case the merged plate is cut according to the respective closed cutting paths of each of the more than one printing plates.

[0023] Another aspect of the present invention includes a method of printing using a printing plate created by the process described herein, the method further comprising the steps of: setting the printing plate on a printing cylinder such that the top edge and the bottom edge of the plate are adjacent to each other, having a gap as described herein between at least their respective portions, and printing an original image on a substrate. The method may further include the step of removing the printing plate from the printing cylinder using a tool inserted into the gap.

[0024] Another aspect of the present invention includes a printing plate product manufactured by the process described herein. Such a printing plate may have a top edge containing a first path geometry and a bottom edge containing a second path geometry, wherein the first path geometry and the second path geometry are not the same. When the winding cylinder is set, the top edge and the bottom edge of the printing plate may be adjacent to each other within a distance ranging from zero to a predetermined maximum value as defined by the gap.

[0025] Another aspect of the present invention includes a computer-readable medium embodying non-transitory computer-readable instructions that, when executed by a processor, cause the processor to perform the method described herein or any part thereof. Another aspect of the present invention includes a printing system that includes a processor and a computer-readable medium as described. The printing system may further include an imager and a cutter, the imager being configured to receive instructions from the processor to image the printing plate according to an updated graphic file, and the cutter being configured to receive instructions from the processor to cut the printing plate according to a closed cutting path. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1A is a perspective illustration depicting an exemplary prior art printing sleeve mounted on a cylinder, wherein multiple single-design images in adjacent channels are in relative alignment.

[0027] FIG. 1B is a perspective illustration depicting an exemplary prior art printing sleeve mounted on a cylinder, wherein multiple single-design images in adjacent channels are out of phase with each other.

[0028] FIG. 1C is a plan view illustration of a flat printing plate having the same arrangement of single-design images as FIG. 1B, configured to wrap around a cylinder, having a top and a bottom edge with one or more inflection points, but only extending through the gaps between adjacent single-design images.

[0029] FIG. 1D is a perspective illustration depicting the printing plate of FIG. 1C, showing a seam where the top and bottom edges of the plate are adjacent to each other when the plate is wrapped around the printing cylinder.

[0030] Figure 2A is a plan view illustration of a flat printing plate configured to wrap around a cylinder, where a single design image has blank spaces between the graphic features in the image, and the top and bottom edges have one or more inflection points that bisect the blank space within the boundary of the single design image.

[0031] Figure 2B is a perspective view illustration of the printing plate of Figure 2A, showing a seam where the top and bottom edges of the plate are adjacent to each other when the plate wraps around the printing cylinder.

[0032] Figure 3 is a flow chart schematically depicting an exemplary prior art method for creating a printing plate with an offset channel.

[0033] Figure 4A is an exemplary staggered layout showing the positioning of a single design and production marks.

[0034] Figure 4B is an exemplary staggered layout showing exemplary cutting paths for the top and bottom edges of a defined plate for a specific color separation, where the edges have one or more inflection points.

[0035] Figure 4C is an exemplary staggered layout showing exemplary cutting paths for the top and bottom edges of a defined plate for multiple color separations.

[0036] Figure 4D is a profile of a first color separation having top and bottom edges defined by one of the cutting paths in Figure 4C , resulting in a straight line shape.

[0037] Figure 4E is a profile of a second color separation having top and bottom edges defined by one of the cutting paths in Figure 4C .

[0038] Figure 4F is a profile of a third color separation having top and bottom edges defined by one of the cutting paths in Figure 4C .

[0039] Figure 5 is a flow chart schematically depicting an exemplary method for designing a printing plate with an offset channel according to one aspect of the present invention.

[0040] Figure 6 is a flow chart schematically depicting an exemplary process for creating a printing plate according to one aspect of the present invention.

[0041] Figure 7 is an illustration of a graph depicting one aspect of applying a penalty function.

[0042] Figure 8A diagram depicting the application of a penalty function that applies different penalties within the die line, in the bleed area, and in the centerline corridor.

[0043] Figure 9A A diagram of an original layout including a site with a die line, a bleed area, and production marks, showing an exemplary seam path.

[0044] Figure 9B Is Figure 9A A diagram of a prominent part of the layout, showing a variable gap between the top and bottom plate edges relative to the cutting line.

[0045] Figure 10 A diagram of applying an energy function to a pixelated version of the penalty function.

[0046] Figure 11 A diagram of an exemplary system according to one aspect of the present invention.

[0047] Figure 12A A diagram of a portion of a line derived by applying the Voronoi path finding algorithm.

[0048] Figure 12B Is applied to Figure 12A Line smoothing of the line derived in. Detailed Description

[0049] One aspect of the present invention is an overall process 600 for manufacturing a printing plate, as depicted in the flowchart of Figure 6 In step 610, a digital original is received for a printing cylinder, which has an initial layout. In step 612, an optimal seam path with a gap is defined (e.g., as described herein), in step 614, the path and gap are expanded into a closed cutting path, and in step 615, the path is stored in the original file. In step 616, the original is repeated to fill the area within the cutting path, and in step 618, a mask is applied to remove anything outside the cutting path boundary. Steps 612 - 618 are repeated for each color separation, and in step 630, the digital original is stored. In step 642, the flexographic plate is imaged and processed (e.g., exposed, e.g., with UV light, and uncured polymer is removed); in step 644, the plate is cut according to the stored cutting path; and in step 646, the plate is mounted on the printing cylinder. Steps 642 - 646 are repeated for each color separation. Then, in step 650, printing begins. In the imaging and processing step, multiple printing plates can be combined onto a larger combined intermediate plate, in which case, after imaging and processing, the combined intermediate plate is cut according to the respective closed plate cutting paths of the multiple printing plates.

[0050] Exemplary processes for creating a printing plate can include designing a printing plate according to the methods described herein, forming a printing plate corresponding to an updated digital graphic file by imaging, exposing, and otherwise processing the printing plate, cutting the printing plate along a closed cutting path geometry to define a top cutting edge and a bottom cutting edge of the plate, and wrapping the plate around a printing cylinder such that the top cutting edge and the bottom cutting edge and the gap therebetween form a seam.

[0051] The methods described herein are preferably executed by a computer processor programmed with non - transitory machine - readable instructions for causing the processor to execute the method steps described herein.

[0052] As Figure 11 Depicted, an exemplary system 1100 for implementing the present invention includes a processor 1102 that accesses a computer storage medium 1104 containing non - transitory machine - readable instructions stored on the medium. The computer storage medium can include any type of computer storage medium known in the art or to be widely implemented, including but not limited to magnetic, optical, flash, etc., and can include portable media, media co - located with one or more associated processors, such as in a desktop or laptop computer or mobile device, and media on a server or otherwise network - accessible, such as via the Internet. The system can also include a display device 1106 configured to present visual information to a human user, and a user interface for receiving inputs such as instructions from a human user. The user interface can include visual images presented on the display device 1106 as part of a graphical user interface (GUI), and any type of user input device 1108 known in the art. Suitable user input devices include, for example, a mouse, trackball or other cursor control and selection device, a keyboard for entering alphanumeric instructions, and / or a touchscreen for allowing a user to manipulate images on the display device. The touchscreen implementation can be configured to allow a user to use a stylus or finger or multiple fingers to draw graphic images or otherwise manipulate the screen, to select radio buttons or items from a menu such as a drop - down menu, or to select alphanumeric characters on a virtual keyboard. The display / user interface can include a mobile device connected to the processor via a wired or wireless network. The processor (which can include multiple processors communicating with each other in multiple locations) can be locally resident, remotely resident on a network (including via the Internet), or partially resident on a mobile device. The present invention is not limited to any particular computer system, computer processor, display type, memory type, or user input device for implementing the present invention.

[0053] System 1100 can be further integrated with other components of a workflow for creating a printed plate, including but not limited to imager 1120 and cutting machine 1130, which can receive instructions specific to the plate design created using the system. The processor can be part of an integrated system that also controls other aspects of the plate-making workflow, including an exposure unit (which, in some embodiments, can also receive image-like information specific to printed or non-printed features on the plate), plate cleaning (or other plate processing equipment), and a lithographic printing system for applying ink to a sheet web using a printed plate created in accordance with aspects of the present invention. Although described herein with respect to imaging plates using LAM and UV exposure techniques, it should be understood that the present invention is not limited to any particular plate-making method and can include, for example, other masking techniques as well as additive manufacturing, without limitation.

[0054] Reference Figures 4A - 4F and Figure 5 , an exemplary method 500 will now be described in more detail generally in accordance with one aspect of the present invention, such as a method performed by a computer processor in a system such as Figure 11 depicted. As Figures 4A - 4F depicted, an exemplary digital graphic file corresponding to graphic layout 400 has three channels 402a, 402b, 402c, which are distributed across the width of the plate, and each channel defines a plurality of single design images 404 (404a, 404b, 404c, etc.) or portions thereof, which are arranged in a stepped and repeating pattern along the length of the printed plate. Each single design image has a top boundary 405, a bottom boundary 406, and opposing lateral edges 407, 408. Each pair of adjacent single design images (e.g., 404a, 404b) in the same channel (e.g., 402a) has a step 410 between each bottom boundary of the first single design image 404a and the adjacent top boundary of the second single design image 404b. The top boundary of the complete topmost single design image 404b in channel 402a is offset by a distance Y from the top boundary of the corresponding complete topmost single design image 404e in channel 402b, herein referred to as the "stagger distance".

[0055] According to one embodiment of the method, an operator first specifies a desired staggered layout, such as the staggered layout depicted on plate 400 as Figure 4A shown, including the positions of single designs 404 and production marks 412. Although represented as rectangles in Figures 4A - 4F , production marks 412 typically include more complex artwork. The initial staggered layout represents one possible way of how the plate will be cut, including specifying the step size between adjacent single design images, but not necessarily the final shape of the plate. The algorithm repeats (wraps) the artwork along the drum circumference in step 510 to simulate the expected seamless printing result, as Figure 4Brepresented by the brighter shaded regions 404, 413 in

[0056] Then, for each printing separation, in step 520, the processor defines an optimal seam path connecting the left and right sides of the blanket cylinder ( Figure 6 in step 612 of ). This optimal seam path can extend between single designs, through them, or a combination thereof, such as cutting path 414, as depicted, for example, in Figure 4B . The optimal cutting path preferably avoids the ink areas by a sufficient distance and has a minimum amplitude A. In some embodiments, the RIP process can be simulated to identify the ink areas that specify a certain amount of ink transfer, while in other embodiments, the optimal seam path can be identified from the vector image. The optimal path travels from one vertical edge of the plate to the opposite vertical edge of the plate, traveling only through the non-inked areas (or optionally, through the bleed lines, preferably through the centerlines of adjacent die lines). The algorithm can include programming to avoid the inked areas by a given distance and to minimize the vertical amplitude of the path, with the ideal path being a straight (horizontal) line without inflection points. Although not limited to any specific distance, the exemplary given minimum safe distance from the inked content is typically in the range between 0.2 mm and 0.5 mm, and the preferred given distance from the inked area is typically about 10 times larger: in the range between 2 mm and 5 mm.

[0057] In step 530, a gap is added to the cutting path, which may have a variable width. This gap is depicted, for example, by the upper line 902 and the lower line 906 that define the seam 904 in Figure 9B . Then, by first smoothing the seam path (and / or the top and bottom edges) in step 540 and then vertically offsetting the top and bottom edges of the gap by the blanket cylinder circumference in the unfolding step 550 ( Figure 6 in step 614 of ), this seam and gap are converted into a closed plate cutting path. The foregoing steps are repeated for each separation, resulting in corresponding top and bottom cutting paths 414t and 414b, 416t and 414b, and 418t and 418b for each flexographic separation, as depicted, for example, in Figure 4C . If not already done, then the step is updated and the graphic file is repeated to ensure that all original graphics, including partial single designs, are present between the top and bottom cutting paths of each separation and that the original graphics outside the closed plate cutting path are removed ( Figure 6 in step 618 of ). This masking is performed independently for each separation. The digital file is updated accordingly ( Figure 6 in step 630 of ). In a system configured to ignore the data outside the plate cutting path, the masking step may be unnecessary.

[0058] As depicted in Figure 4D , 4EAs depicted by 4F, the resulting plates may all be different, and installation marks (e.g., microdots) 412 are typically used to ensure that the plates are consistently installed on their respective cylinders in register with each other. As Figure 6 The remainder of the process outlined in

[0059] by which the plates are imaged, processed, and machine cut according to the defined closed plate cutting paths, is then performed on the updated file so created as previously described.

[0060] In some cases, the characteristics of the "best" path may be conflicting, in which case each characteristic can be graded, weighted, or ranked by the operator, or according to one or more default gradings or weightings, which may be different for different types of operations and may be preset according to the operation type.

[0061] Finding the best cutting path presents an optimization problem with multiple different metrics, such as including: (A) limiting the total amplitude A (vertical extent) of the path to reduce plate waste; (b) limiting the non-0% (printed) area close to the cutting path to minimize the risk that the cutting path affects print quality; and (c) limiting the number and severity of inflection points 420 in the cutting path to reduce the risk of plate damage. These metrics may be conflicting, where the best solution involves a compromise between them. Thus, in one embodiment, the processor can prompt for and receive user input specifying the relative importance or weight of these three metrics, and then use these as weights to evaluate possible solutions. Additionally, including a gap at the seam aids installation and removal purposes, including, for example, making it easier to insert tools for removing the plate from the cylinder, and may also take into account avoiding production (registration) marks.

[0062] Programming the metrics for defining the seam path includes specifying a desired longitudinal offset spacing Y between the respective top boundaries of adjacent full single design images (e.g., 404b, 404e in adjacent channels 402a, 402b). One or more cut-acceptable regions are defined between the lateral edges 307, 308 of each single design image 404, which are acceptable for containing the seam path. The definition of such cut-acceptable regions can include, for example, identified non-ink-bearing regions beyond a predefined distance from the ink-bearing features, or regions within the bleed line, such as the centerline of adjacent die lines. Defining an optimal lateral seam path between the opposing lateral edges of the printing plate, where the optimal lateral seam path is defined to travel in each channel by passing only through the cut-acceptable regions or by stepping between adjacent single design images, and based on seam path criteria, the seam path criteria includes:

[0063] · Minimizing the path amplitude;

[0064] · Maximizing the distance from non-cut-acceptable regions; and

[0065] · Minimizing the number of corners with a radius less than a predetermined size.

[0066] As discussed in the background section, there are many risks associated with cutting imaging plates, and these risks can be translated into criteria for optimizing the cutting path:

[0067] 1. The cutting plate must wrap around the cylinder and contain all the original images required on the cylinder surface.

[0068] 2. The cutting path must be away from the original images, maintaining at least a minimum margin, but preferably a little more than the minimum margin (desired margin).

[0069] 3. The cutting path is ideally smooth, i.e., does not contain (sharp) corners, minimizing the degree and number of inflection points.

[0070] 4. In some embodiments, it is desirable that the gap at the seam be large enough to facilitate installation and disassembly (e.g., inserting a tool for disassembly).

[0071] 5. All production marks should still serve their intended purpose. Thus, for example, cutting the carrier bar is not disapproved because even the cut carrier bar will still contribute to the stability of the pressure bar, but cutting registration marks is disapproved.

[0072] These standards often conflict with each other. For example, if the original image occupies a large part of the plate, it is impossible to maintain the minimum distance from the original image. In fact, in order to meet the first standard, it may even be necessary to cut off the original image. A smooth cutting path may bring the path closer to the original image. If there is not enough blank space in the design, then the ideal gap at the seam may not be achievable without cutting off the original image.

[0073] Embodiments of the present invention are designed to automatically find an appropriate balance between the aforementioned standards. The methods described herein are performed using an initial input from a user, including a (digital) original image for which a plate is to be made. In some embodiments, the original image may include sites that include die-cut shapes. These sites may be staggered. The original image may also contain production marks or other objects. The initial original image may be laid out according to a possible cutting pattern (not necessarily the pattern ultimately used). Alternatively, the original image is already prepared to fit a rectangle that matches the drum area (which is common when producing flexographic sleeves or gravure cylinders). The initial input provides the orientation of the original image relative to the web direction. Additional inputs include the dimensions of the drum area C for receiving the plate (width C wand and circumference C c ); a predetermined minimum distance D between the cutting path and the original image m , a desired distance D between the cutting path and the original image d , a desired minimum corner radius R of the cutting path, and a desired gap distance G that defines the space between the two ends of the plate when mounted on the drum.

[0074] Thus, in the method described above with reference to Figure 5 , after performing step 520 to identify the seam path 904(S) that connects the left and right edges of the drum, in step 530, the gap G is defined by offsetting S to create a top cutting path 906(S t ) and a bottom cutting path 902(S b ), as depicted in Figure 9B , such that the distance between 902(S t ) and 906(S t ) is at most G. Although the gap distance between 902(S b ) and 906(S t ) can vary, the gap G represents the distance between 902(S b ) and 906(S t ). In some regions, the gap distance can be 0 (e.g., in the channel 908 between the die-cut lines). The plate cutting paths 902(S b ) and 906(S t ) may be allowed to come arbitrarily close to the bleed original image, but may need to maintain a minimum distance D from the original image within the die-cut shape 912m As further explained below, the edges are rounded where possible.

[0075] The preferred algorithm in step 540 now smooths S t and S b (without exceeding the maximum gap width), such that the curvature k at each point along those paths is at most 1 / R (unless this would cause S t or Sb to cut off any original image). Next, the algorithm unfolds S C by moving down along the drum circumference C b , and joins it to S t to create a closed path. Thus, referring now to Figure 4C , the top path 414t, the left path 450, the bottom path 414b, and the right path 452 create a closed path. This is the cutting path ultimately obtained for this color separation. The left path 450 and the right path 452 similarly form closed paths with the top path 416t, the bottom path 416b, and with the top path 418t, the bottom path 418b, respectively.

[0076] We now review each of these steps in more detail. Step 510, which includes preparing a digital graphic file with an offset channel having a stepped and repeated single design, can also be referred to as "wrapping". Wrapping refers to the process in which the original image is vertically repeated on the drum circumference C c to cover the entire drum area C (Cc × Cw). Figure 9A and 9B illustrate an exemplary layout 900 including a plurality of stations 920, each station including an original image 910 defined within a die line 912 and a bleed mask 913 defined between a bleed line 914 and the die line 912. Registration marks 916 are located on one side of the layout. The optimal seam path 904 is depicted as extending through the original image according to an algorithm described in more detail below.

[0077] Step 520 automatically finds a path S from one side of C to the other (e.g., from the left side of C to the right side).

[0078] The path is found by solving an optimization problem, e.g., by applying a minimum energy path finding algorithm. An exemplary such algorithm is an energy minimization function including a proximity metric and one or more curve metrics, such as Equation 1:

[0079] E(S) = a(∫p In s P(p)dl) + β(L(S)) + γ(A(S)) [1]

[0080] Finding the optimal seam path involves finding the path that minimizes the energy function of Equation 1. The energy function of Equation 1 consists of three terms: · A proximity penalty function P integrated along the path (see below)

[0081] · The path length L(S); and

[0082] · The amplitude of the path A(S), which is the difference between the maximum and minimum vertical coordinates of the path.

[0083] The relative weights of each of these terms can be selected by varying the α, β, and γ factors. These factors can be assigned in software, can have preset values for certain applications, or can be provided to the user as a means of controlling the importance of each requirement (such control can include selecting a preset combination of factors that is more advantageous in certain situations).

[0084] Energy terms for other path attributes (such as smoothness or the number of sharp corners, etc.) can also be configured and weighted with corresponding factors.

[0085] Exemplary proximity penalty function

[0086] The p in Equation 1 is a function that maps each point p on the drum to a penalty value based on the original image to be imaged by the drum. A simple proximity penalty function can be based on the distance of the point to the nearest imaging area, as Figure 7 shown in Figure 7 including graph 750, which indicates how the penalty value of a point relates to its distance to the nearest imaging area. Figure 7 Depicts three exemplary points 730, 732, 734 relative to a square imaging area 700, which are surrounded by a first area 710 representing the minimum distance D m from the imaging area and a second area 720 representing the desired distance D d from the imaging area. Then, each point relative to the imaging area is mapped to graph 750, which depicts the penalty P as a function of the distance of the point p to the imaging area 700. If p is within the imaging area or closer to the imaging area than D m , for example at location point 730, P(p) = P high (e.g., infinite). If the distance from p to the nearest imaging area > D d , for example at the location of point 734, then P(p) = 0. If the distance from p to the nearest imaging area is between D m and D d , then P(p) linearly progresses from P medium to 0 along line 752. However, the present invention is not limited to any particular distance-based function.

[0087] By dividing the imaging area into different categories and then defining a partial penalty function for each category (each category having different parameters D m , D d , P high , P medium ), and combining them into a penalty function by taking the maximum value among the partial penalty functions, the penalty function can be further improved. Exemplary categories can include:

[0088] · The imaging area within the die-out shape. This category may have P high (e.g., infinite) and the highest value of P medium .

[0089] · The imaging area of production (e.g., registration) marks (e.g., D m = 0 and a lower P high value).

[0090] · The imaging area within the bleed area. This can be given the same parameters as the production marks.

[0091] Depending on the type of the original image, more categories can be considered to create the desired grading (e.g., crossing a carrier bar mark may have a lower penalty than crossing a registration mark).

[0092] The penalty function can be further improved by adding corridors. A corridor is a curve (or narrow track) in the function domain where the penalty function is clipped to not exceed a threshold P low , despite all the above rules. This allows the optimization algorithm to find a path through these corridors that would otherwise have an excessive penalty. For example, in one embodiment, corridors can be provided on the centerline between die-cut shapes, such as Figure 9B the line 908 in Figure 8 shows the intersection of an exemplary penalty function 800 with respect to two types of content (the original image 810 and the bleed 820), further depicting the intersection of the function with the centerline corridor 830 (e.g., Figure 9B the corridor 908 depicted between the bleed lines 914 of adjacent sites 920 in

[0093] The step 530 of identifying the best seam path creates two paths 902(S t ) and 906(S b ) on both sides of the seam path 904(S). S t and S b together define the gap that the mounting plate will have. The distance between each path S t and S b to the seam path S can vary along its length and is asymmetric (for S t and S bare different).

[0094] S t and S b The distance between and S is at most G, but can also be as small as zero. Generally, S t or S b should not cross the imaging area, unless S itself crosses the imaging area.

[0095] As described above, in step 550, the seam path S is smoothed, and / or the top and bottom seam paths S t and S b are each smoothed. An exemplary smoothing algorithm is described in Chapter 3 of JuYoung Kang and ByungSuk Lee's Optimisation of pipeline route in the presence of obstacles based on a least cost path algorithm and laplacian smoothing, which is incorporated herein by reference.

[0096] Then, the digital graphic file is updated to define the top and bottom edges of the plate according to the geometry of the optimal lateral seam path as defined, and at least two channels are filled with corresponding multiple single design images or portions thereof between the updated top edge and the updated bottom edge. Then, the method is performed for each of the multiple color separations corresponding to the digital graphic file.

[0097] The step of defining the optimal lateral seam path may include defining a plurality of potential lateral seam paths that meet the seam path criteria within a predetermined deviation degree, providing a visual display (e.g., on the display 1106) illustrating the plurality of potential lateral seam paths, and receiving user input (e.g., via the input device 1108), such as by the user selecting (e.g., graphically with a mouse click) one of the plurality of potential lateral seam paths as the optimal lateral seam path. In some embodiments, the user may show one or more points on the original image for the path to pass through, where the user selects the desired points. Then the optimal path is searched for within the given user-defined constraints.

[0098] Because each color separation of a printing production job typically has different printing characteristics, the calculated lateral seam paths are usually different for each printing plate. In many embodiments, this is desirable because it results in plates that are highly desirable for certain applications. (Although they have different shapes, when installed on the drum, these plates will all align with the expected repeating design). However, in other embodiments, it may be desirable for the printing plates to share the same shape (because this may make it easier to transport the cut plates). To achieve this, the lateral seam path can be calculated based on the union of all color separations rather than one color separation at a time. This option can be included among the multiple potential lateral seam paths provided to the user.

[0099] In one embodiment, a pixelated version of the proximity penalty function P can be implemented. This embodiment can include the following steps:

[0100] 1. Calculate a penalty image sized for the drum area at a high enough resolution:

[0101] a. Rasterize the color separations into an original image (same size and resolution). Use different pixel values to distinguish non - imaging areas and imaging areas (and possibly different types of imaging areas).

[0102] b. Evaluate the penalty function for isolated imaging pixels and store it in a kernel image (sized 2D d ×2D d and centered on the imaging pixel). If the penalty function contains terms for different original image classes, create a separate kernel image for each class.

[0103] c. Initialize the penalty image with all zeros.

[0104] d. For each imaging pixel in the original image, align the corresponding kernel image with the penalty image and store the highest of the two values in the penalty image.

[0105] e. Repeat steps b - d for all imaging pixels.

[0106] 2. Find an initial cut path S with the minimum penalty:

[0107] a. Treat the penalty image as a graph diagram 1000, where each pixel is represented by a node 1010 connected to its 8 neighbors (horizontally, vertically, and diagonally), as Figure 10 depicted. Two additional nodes 1012, 1014 represent the left and right edges respectively.

[0108] b. The pixels at the top row 1020 of the image are similarly connected to their bottom - row counterparts 1030 (simulating the seamless nature of the drum)

[0109] c. Consider the contribution of each edge to the energy function [e.g., Equation 1]:

[0110] i. Contribution to L(S): the length of the edge; and

[0111] ii. Contribution to ∫p In s P(p)dI: the length of the edge multiplied by the average of the penalty pixel values at both ends.

[0112] d. Run a path-finding algorithm on this graph, such as an algorithm known in the art, to find the lowest-energy path from the left side 1012 to the right side 1014, e.g., represented by path 1050 in Figure 10 . The algorithm can be applied from left to right or from right to left.

[0113] e. Convert this pixel path to a vector path.

[0114] 3. Execute steps 530 to 550 of the above method.

[0115] Exemplary path-finding algorithms known in the art include those commonly referred to as "Dijkstra" (Dijkstra, E.W. (1959). "A note on two problems in connexion with graphs." Numerische Mathematik. 1:269 - 271) and its extensions, including "A*" [read as "A-star"] (Hart, P.E.; Nilsson, N.J.; Raphael, B. (1968). "A Formal Basis for the Heuristic Determination of Minimum Cost Paths". IEEE Transactions on Systems Science and Cybernetics. 4(2); 100 - 107), which are hereby incorporated by reference.

[0116] In some embodiments, the method may omit the magnitude (A) of the cut path from the energy function. In other cases, step 2(d) may be performed multiple times with at least one difference (e.g., applied between at least one different start node on the left edge, a different end node on the right edge, or forced to include at least one intermediate node to obtain a predetermined number of results). Then, multiple iterations can be evaluated for P, L, and A to produce different E values, from which the best value of E (usually the lowest value) is ideally selected.

[0117] While a design including a parting line can have a corresponding parting line associated therewith (which fixes the interleaving pattern of a single design), in other embodiments the interleaving pattern can be more variable, allowing iterative optimization of the cutting paths for different offsets between single designs in adjacent channels. In such embodiments, the method described above can be performed to select an optimal cutting path for a first interleaving pattern and then performed again for a different interleaving pattern. The different interleaving patterns can be selected by a human operator or determined automatically, e.g., by incrementally increasing the interleaving distance within a distance range according to a predetermined step distance. The range and step parameters can be provided by user input or set to default values. The interleaving distance affects all color separations, so the cutting paths for all color separations can be considered when selecting an optimal interleaving pattern.

[0118] Although some steps are described herein in a preferred order, the present invention is not necessarily limited to any order of step execution. Although described herein with respect to specific penalty functions and specific energy functions, it should be understood that the present invention is not limited to any particular equations of these functions.

[0119] The above-described embodiment for finding a seam path is an example of a minimum energy path finding algorithm, where the inked areas are obstacles and the path length and proximity are used as energy metrics. Other minimum energy path finding algorithms known in the field of path finding and obstacle avoidance can be applied to find a path according to such metrics. For example, in one embodiment, as Figure 12A illustrated, a Voronoi diagram can be formed by inked areas (obstacles) 1202, 1204 based on the centerlines 1210 between adjacent obstacles. The diagram is then converted into a graph 1200, where graph nodes 1220 are all points where three or more centerlines 1210 intersect, and where graph edges represent the centerlines between these nodes. Two nodes are added to represent the left and right sides of the plate (not shown), and the graph is simplified by pruning all dead-end graphs. The contribution of each edge to the energy of the seam path is calculated, e.g., by evaluating E(p) along the subpath. Alternatively, instead of integrating a penalty function, a penalty value can be assigned based on the closest proximity of the subpath to the inked area. Then, a shortest path algorithm (e.g., Dijkstra) is used to find the lowest energy path 1230 through the graph (from left to right, or vice versa). The path is then post-processed as described above to smooth and straighten it (e.g., by moving node 1232 from a first position on path 1230 along arrow 1234 to a new position 1242 on path 1240, modifying path 1230 to path 1240, as Figure 12Bas depicted), and adding gaps (as previously described). Smoothing in Voronoi embodiments can be rather drastic because the centerline may bend unnecessarily. Exemplary algorithms for applying Voronoi diagrams and subsequent smoothing for obstacle-avoiding path finding (for a metric based solely on curve length) can be found in Ho, Yi-Ju and Jing-Sin Liu "Smoothing Voronoi-based Obstacle-avoiding Path by Length-minimizing Composite Bezier Curve." (2009), which is incorporated herein by reference.

[0120] The aspects of the invention described herein have advantages over prior art systems because they can reduce plate waste, result in simpler cutting paths, use less operator time, or a combination of all of the above. While in some cases the use of the systems and methods of the invention may achieve the same results that might otherwise have been achieved using prior art systems, over time the use of the invention is expected to provide, on average, greater efficiency, reliability, and repeatability.

[0121] Although discussed in the context of a staggered layout, the systems and methods of the invention are not exclusive to a staggered layout, and aspects of the invention can also be applied to other continuous designs that require non-rectangular plates. When printing on very wide webs, it is also common for each cylinder to produce multiple plates and have them mounted in channels. In such an embodiment, the invention described herein can also be applied to an individual channel rather than the entire cylinder. Thus, references herein to "cylinder width" in the context of such an embodiment refer only to the width of the portion of the cylinder covered by a particular channel that extends between the vertical edges of one printing plate.

[0122] Although the invention has been 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 bounds of the equivalents of the claims without departing from the invention.

Claims

1. A method for designing a printing plate having a plate width defined between lateral edges and a nominal plate length defined between a top edge and a bottom edge, the printing plate being configured to be mounted on a printing cylinder having a cylinder width and a cylinder circumference, the nominal plate length dimension corresponding to the cylinder circumference, the method comprising the steps of: (a) Preparing an initial digital graphic file including an original image; (b) Defining an optimal lateral seam path between opposite lateral edges of the printing plate by applying a minimum energy path finding algorithm; (c) Defining the top edge and the bottom edge of the plate according to the geometry of the optimal lateral seam path; (d) Unfolding the bottom edge from the top edge to define a closed plate cutting path, the closed plate cutting path including the top edge, the bottom edge and opposite side edges connecting the top and bottom edges of the plate, the closed plate cutting path defining an area; (e) Wrapping the area defined by the closed plate cutting path with the original image or a portion thereof; and (f) Storing the updated digital graphic file.

2. The method according to claim 1, wherein the original image includes a plurality of production marks, and one or more channels of a single design image or a portion thereof are arranged in a stepped and repeating pattern along the length of the printing plate, the one or more channels being distributed across the width of the plate, each single design image having a top boundary, a bottom boundary and opposite lateral edges, and each pair of adjacent single design images in the same channel having a step between each bottom boundary of the first single design image and the adjacent top boundary of the second single design image, wherein the optimal lateral seam path is defined to travel through one or more single design images, steps between adjacent single design images, or a combination thereof in each channel.

3. The method according to claim 2, including at least two channels, wherein the top boundary of the complete topmost single design image in the first channel is offset by a staggering distance from the top boundary of the corresponding complete topmost single design image in the second channel.

4. The method according to any one of the preceding claims, including defining the top edge and the bottom edge to enclose a gap, the gap width of the gap being equal to or less than the maximum gap width on opposite sides of at least a portion of the optimal lateral seam path.

5. The method according to claim 1, further comprising smoothing one or more of the optimal lateral seam path, the top edge and the bottom edge to minimize the number of inflection points and maximize the radius of the inflection points.

6. The method according to claim 1, wherein the minimum energy path finding algorithm uses a proximity metric and one or more curve metrics.

7. The method according to claim 1, wherein the minimum energy path finding algorithm includes an energy minimization function.

8. The method according to claim 7, wherein the energy minimization function includes a proximity penalty function P integrated along the optimal lateral seam path.

9. The method according to claim 8, wherein, The proximity penalty function is configured to assign the highest penalty to proximity within the printed features of the original image or to proximity within a minimum distance from the printed features of the original image, assign the lowest penalty to proximity beyond a desired distance from the printed features, the desired distance being greater than the minimum distance, and assign a variable penalty to proximity within a range between the minimum distance and the desired distance.

10. The method according to claim 8 or 9, wherein, the original image includes a die line and a bleed area, and the proximity penalty function is configured to assign a relatively greater penalty to printed features within the die line than to printed features within the bleed area.

11. The method according to claim 10, wherein the proximity penalty function further includes one or more centerline corridors corresponding to a centerline between die lines, and the penalty assigned to the centerline corridors is relatively lower than the penalty assigned based on proximity to the bleed area.

12. The method according to claim 8, wherein the proximity penalty function is a pixelated penalty function.

13. The method according to claim 8, wherein the energy minimization function includes minimizing the total seam path length as an optimization criterion.

14. The method according to claim 13, wherein the energy minimization function includes minimizing the seam path amplitude as an optimization criterion.

15. The method according to claim 14, wherein, the energy minimization function includes a weighting factor for weighting the proximity penalty function, the minimized total seam path length, and the minimized seam path amplitude.

16. The method according to claim 1, including performing steps (b)-(f) for each of a plurality of color separations corresponding to a digital graphic file.

17. The method according to claim 1, wherein, the step of defining an optimal lateral seam path includes: defining a plurality of potential lateral seam paths that meet the seam path criteria within a predetermined deviation, providing a visual display illustrating the plurality of potential lateral seam paths, and receiving user input selecting one of the plurality of potential lateral seam paths as the optimal lateral seam path.

18. The method according to claim 17, wherein, the plurality of potential lateral seam paths provided in the visual display includes potential lateral seam paths for a plurality of color separations, which includes at least one combination of potential lateral seam paths for a plurality of color separations, wherein the potential lateral seam paths correspond to printing plates for all of the plurality of color separations having the same shape.

19. The method according to claim 17 or 18, including providing an initial digital graphic file having a first stagger distance, defining an optimal lateral seam path corresponding to the first stagger distance, considering a second stagger distance different from the first offset, defining a second optimal lateral seam path corresponding to the second stagger distance, and selecting one of the first or second stagger distances for performing the remaining steps of the method.

20. The method according to claim 1, wherein the original image outside the closed plate cutting path is removed in a masking step performed between steps (e) and (f).

21. A process for creating a printing plate, the process comprising the following steps: (A) Designing a printing plate according to the method of any one of claims 1-20; (B) Imaging the printing plate according to an updated graphic file; (C) Exposing and processing the printing plate; (D) Cutting the printing plate according to a closed plate cutting path.

22. The process according to claim 21, wherein steps (B)-(D) are carried out in the order (B), (C), (D).

23. The process according to claim 21 or 22, wherein step (B) includes merging a plurality of printing plates onto a merged intermediate plate, and step (D) includes cutting the merged plate according to the respective closed cutting paths of each of the plurality of printing plates.

24. A method of printing using a printing plate created by the process of any one of claims 21-23, further comprising the following steps: Setting the printing plate on a printing cylinder such that the top edge and the bottom edge of the plate are adjacent to each other; and Printing an original image on a substrate.

25. The method according to claim 24, wherein, the printing plate set on the printing cylinder has a gap between its top edge and bottom edge in at least one region thereof, and further comprising the following steps: Removing the printing plate from the printing cylinder using a tool inserted into the gap.

26. A printing plate product manufactured by the process of any one of claims 21-23.

27. The printing plate product according to claim 26, wherein the printing plate has a top edge containing a first path geometry and a bottom edge containing a second path geometry, wherein the first path geometry and the second path geometry are not the same.

28. The printing plate product according to claim 27, wherein, when set in a configuration wound around a cylinder, the top edge and the bottom edge of the printing plate are adjacent to each other within a distance ranging from zero to a predetermined maximum value from each other.

29. A computer-readable medium embodying non-transitory computer-readable instructions which, when executed by a processor, cause the processor to perform the method of any one of claims 1-20.

30. A printing system comprising a processor and the computer-readable medium of claim 29.

31. The printing system according to claim 30, further comprising: An imager configured to receive instructions from the processor for imaging a printing plate according to an updated graphic file; A cutter configured to receive instructions from the processor for cutting a printing plate according to a closed cutting path.

Images