Digital printing system and method

Abstract

A printing method includes generating a first image at a first position (16a, 23a) on a movable intermediate transfer mechanism (ITM) (44) of a printing system (10), and moving the ITM (44) to transfer the first image to a first substrate (50). For a second image intended to be generated on the ITM (44) at a second position (16b, 23b) different from the first position (16a, 23a): (i) specifying an intentional offset (18, 24) of the second position (16b, 23b) relative to the first position (16a, 23a), (ii) calculating a movement of the ITM (44) that will at least partially compensate for the offset (18, 24) when transferring the second image to the second substrate (50), and (iii) generating the second image and moving the ITM (44) according to the calculated movement to transfer the second image to the second substrate (50).

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application 63 / 210,507, filed June 15, 2021, the disclosure of which is incorporated herein by reference. Invention Field

[0003] The present invention relates generally to digital printing, and more particularly to methods and systems for reducing imprints on intermediate transfer components during the printing process. Background of the Invention

[0005] Some printing systems have an intermediate transfer element configured to receive an image and transfer it to a target substrate. In some cases, printing batches containing a large number (e.g., thousands) of copies of a particular image produced on the intermediate transfer element may result in the undesirable formation of traces of the image on the intermediate transfer element, such that the image outline may appear in the printing of another image, for example, in a subsequent printing batch. This phenomenon is also referred to herein as “memory” or “ghosting” and can degrade the quality of subsequent images printed using the same intermediate transfer element. Summary of the Invention

[0006] The embodiments of the present invention described herein provide a printing method comprising: generating a first image at a first position on a movable intermediate transfer member (ITM) of a printing system, and moving the ITM to transfer the first image to a first substrate; and for a second image intended to be generated on the ITM at a second position different from the first position: (i) specifying an intentional offset of the second position relative to the first position, (ii) calculating a movement of the ITM that will at least partially compensate for the offset when transferring the second image to a second substrate, and (iii) generating the second image and moving the ITM according to the calculated movement to transfer the second image to the second substrate.

[0007] In some embodiments, the first image and the second image are copies of a given image. In other embodiments, the second location covered by the second image partially overlaps with the first location covered by the first image. In still other embodiments, the ITM includes a closed loop that is rotatable, and: (i) during a first rotation of the ITM, the first image is generated by positioning the ITM at the first location relative to the image forming station, and (ii) during a second rotation of the ITM, the second image is generated by positioning the ITM at the second location relative to the image forming station.

[0008] In one embodiment, the method includes, after generating the first image and before generating the second image: (i) generating a third image on the ITM at a third position, the third position being shifted relative to a desired position of the third image; (ii) calculating an additional movement of the ITM that will at least partially compensate for the shift when transferring the third image to a third substrate; and (iii) moving the ITM according to the calculated additional movement to transfer the third image to the third substrate.

[0009] In some embodiments, the intentional offset is specified in a direction parallel to the direction of movement of the ITM. In other embodiments, the intentional offset is specified in a direction not parallel to the direction of movement of the ITM.

[0010] In some implementations, the intentional offset of the second position is performed along a first direction, the method comprising, for a plurality of third images intended to be generated on the ITM at a plurality of third positions different from the first and second positions: (i) specifying an additional intentional offset of the third positions along the first direction based on a predefined step size, (ii) calculating a plurality of third movements of the ITM that will at least partially compensate for the additional intentional offset when the third images are transferred to the third substrates respectively, and (iii) generating the third images and moving the ITM according to the calculated movements to transfer the third images to the third substrates respectively.

[0011] In other embodiments, the first substrate, the second substrate, and the third substrate have a given size at least along the first direction, and at least the predefined step size depends on the given size. In still other embodiments, the method includes performing the intentional offset and the additional intentional offset in a second direction other than the first direction after applying the intentional offset and the additional intentional offset and generating and transferring the first image, the second image, and the third image according to the predefined step size.

[0012] According to an embodiment of the invention, a system is further provided, comprising a printing assembly and a processor. The printing assembly is configured to: (i) generate a first image at a first position on a movable intermediate transfer member (ITM) of the printing system, and move the ITM to transfer the first image to a first substrate; and (ii) generate a second image at a second position different from the first position, and move the ITM to transfer the second image to a second substrate. The processor is configured to: (i) specify an intentional offset of the second position relative to the first position; (ii) calculate a movement of the ITM that will at least partially compensate for the offset when transferring the second image to the second substrate; and (iii) control the printing assembly to move the ITM according to the calculated movement to transfer the second image to the second substrate.

[0013] The invention will be more fully understood through the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, wherein: Attached Figure Description

[0014] Figure 1 This is a schematic side view of a digital printing system according to an embodiment of the present invention;

[0015] Figure 2A , Figure 2B , Figure 2C and Figure 2D This is a schematic diagram illustrating the memory effect appearing on the intermediate transfer mechanism (ITM) of a digital printing system according to an embodiment of the present invention;

[0016] Figure 3 This is a schematic side view of an apparatus according to an embodiment of the present invention for compensating for positional offset of an image generated on an ITM when transferring an image to a target substrate; and

[0017] Figure 4 This is a flowchart schematically illustrating a method for reducing the memory effect in a digital printing system with ITM according to an embodiment of the present invention. Detailed Implementation

[0018] Overview

[0019] Some printing systems have an intermediate transfer element configured to receive an image and transfer it to a target substrate. In some cases, printing batches containing a large number (e.g., thousands) of copies of a particular image produced on the intermediate transfer element may result in the undesirable formation of traces of the image on the intermediate transfer element, such that the image outline may appear in the printing of another image, for example, in a subsequent printing batch. This phenomenon is also referred to herein as “memory” or “ghosting” and can degrade the quality of subsequent images printed using the same intermediate transfer element.

[0020] In principle, memory loss during subsequent printing can be reduced by frequently replacing intermediate transfer components and / or performing extensive cleaning processes on these components. However, such operations reduce the utilization and productivity of the printing system and also result in a significant amount of chemicals and intermediate transfer components becoming waste.

[0021] The embodiments of the present invention described below provide an effective method and system for reducing the occurrence of memory in digital printing processes using intermediate transfer components.

[0022] In some embodiments, a digital printing system includes a printing assembly having: (i) an image forming station configured to apply droplets of printing fluid (e.g., jet ink droplets) to the surface of an intermediate transfer member (ITM) to generate an image thereon; (ii) an impression station configured to transfer the image from the ITM to a target substrate (e.g., a sheet); and (iii) an ITM module configured to move the ITM to (a) generate an image by receiving ink droplets from the image forming station, and (b) transfer the image to the sheet. The digital printing system also includes a processor configured to control the printing assembly.

[0023] In this example, the ITM includes a flexible member formed as a loop and has (a) multiple panels, each intended to receive an image, and (b) one or more segments not intended to receive an image. The ITM module is configured to rotate the ITM to perform multiple rotations, and for each panel and each rotation, the processor controls a printing assembly to produce an image and subsequently transfers the image to a sheet, such that in the next rotation, a given panel is ready to receive the next image.

[0024] In some implementations, for a given panel in the panel, the processor is configured to control the printing assembly to: (i) generate a first image at a first position on the ITM during a first rotation and move the ITM to transfer the first image to a first sheet, and (ii) generate a second image on the given panel at a second position different from the first position during a subsequent second rotation and move the ITM to transfer the second image to a second sheet.

[0025] In some implementations, the processor is configured to: (i) specify an intentional offset of the second position relative to the first position; (ii) calculate a movement of the ITM that will compensate for the offset when transferring the second image to the second substrate; and (iii) control the printing assembly to move the ITM according to the calculated movement to transfer the second image to the second substrate. It should be noted that by varying the position of the image produced on a given panel during different rotations of the ITM, undesirable memory imprints on the ITM are reduced.

[0026] In some implementations, in addition to applying offsets to each panel between subsequent rotations of the ITM, the processor is also configured to apply the same technique to shift the relative positions of images between different panels of the ITM. For example, in an ITM having eleven (11) panels, the processor may apply the technique described above to each pair of images generated on a corresponding pair of adjacent panels. In each pair, the images are referred to herein as “earlier” and “follower” images, generated on the “earlier” and “follower” panels, respectively. In this example implementation, the processor controls the printing assembly to shift the position of the subsequent image by an offset of approximately 60 μm relative to the position of the earlier image. Thus, in the aforementioned given panel, the second image generated in the second rotation is positioned at an offset of approximately 660 μm (i.e., 11 offsets of approximately 60 μm) relative to the position of the first image generated in the first rotation.

[0027] The disclosed technology improves: (i) the quality of images printed in digital printing systems with intermediate transfer components, (ii) the productivity of such systems, and (iii) the environmental cleanliness of such printing processes.

[0028] System Description

[0029] Figure 1This is a schematic side view of a digital printing system 10 according to an embodiment of the present invention. In some embodiments, system 10 includes a rolling flexible blanket 44 that is circulated through an image forming station 60, a drying station 64, an impression station 84, and a blanket handling station 52. In the context of the invention and in the claims, the terms "blade" and "intermediate transfer element (ITM)" are used interchangeably and refer to a flexible element comprising one or more layers serving as an intermediate transfer element, the flexible element being formed as a loop configured, for example, to receive an ink image from the image forming station 60 and transfer the ink image to a target substrate, as will be described in detail below.

[0030] In one operating mode, the image forming station 60 is configured to form a mirror ink image of the digital image 42 on a running section of the surface of the blanket 44, the mirror ink image also referred to herein as an "ink image" (not shown) or, for simplicity, an "image". The ink image is then transferred to a target substrate (e.g., paper, folded cartons, multilayer polymers, or any suitable flexible packaging in sheet or continuous roll form) located below the lower running section of the blanket 44.

[0031] In the context of this invention, the term "running segment" refers to the length or section of the rubber blanket 44 between any two given rollers guiding the rubber blanket 44.

[0032] In some embodiments, during installation, the rubber sheet 44 may be adhered edge-to-edge using a seam segment 45 (also referred to herein as seam 45) to form a continuous rubber sheet loop (also referred to herein as a closed loop). Examples of methods and systems for seam installation are described in detail in U.S. Patent Application Publication 2020 / 0171813, the disclosure of which is incorporated herein by reference.

[0033] In some embodiments, the image forming station 60 typically includes a plurality of printing bars 62, each mounted on a frame (not shown) at a fixed height above the surface of an running section of the blanket 44. In some embodiments, each printing bar 62 includes a series of printing heads as wide as the printing area on the blanket 44 and includes individually controllable printing nozzles configured to spray ink and other types of printing fluids onto the blanket 44, as described in detail below.

[0034] In some embodiments, the image forming station 60 may include any suitable number of printing rods 62, which, for simplicity, are also referred to herein as rods 62. Each rod 62 may contain a printing fluid, such as water-based inks of different colors. The inks typically have visible colors, such as, but not limited to, cyan, magenta, red, green, blue, yellow, black, and white. Figure 1 In one example, the image forming station 60 includes seven printing bars 62, but may include, for example, four printing bars 62 having any selected color (such as cyan (C), magenta (M), yellow (Y), and black (K)).

[0035] In some embodiments, the printhead is configured to spray ink droplets of different colors onto the surface of the blanket 44 to form an ink image (not shown) on the surface of the blanket 44. In this example, the blanket 44 moves along the X-axis of the XYZ coordinate system of the system 10, and the ink droplets are guided by the printhead, typically parallel to the Z-axis of the coordinate system.

[0036] In some implementations, the different printing rods 62 are spaced apart from each other along a movement axis, which is also referred to herein as (i) the movement direction 94 of the blanket 44 or (ii) the printing direction. In this example, the movement direction of the blanket 44 is parallel to the X-axis, and each printing rod 62 extends along the Y-axis of the XYZ coordinate system 10. In this configuration, the accurate spacing between the rods 62 along the X-axis and the synchronization between the ink droplets guiding each rod 62 and the moving blanket 44 are crucial for achieving the correct placement of the image pattern.

[0037] In the context of this disclosure and in the claims, the terms “inter-color pattern placement,” “pattern placement accuracy,” “inter-color registration,” “C2C registration,” “inter-color positional difference,” “bar registration,” and “color registration” are used interchangeably and refer to any placement accuracy of two or more colors relative to each other.

[0038] In some embodiments, system 10 includes a heater 66, such as a hot gas or air blower and / or an infrared-based heater having a gas or air blower for flowing gas or air at any suitable temperature. The heater 66 is positioned between the printhead bars 62 and configured to partially dry ink droplets deposited on the surface of the blanket 44. This airflow between the printhead bars can help, for example (i) reduce condensation and / or dispose of splatter (e.g., residue or small droplets distributed around the main ink droplets) at the surface of the printhead, and / or (ii) prevent clogging of the orifices of the inkjet nozzles of the printhead, and / or (iii) prevent undesirable mixing of ink droplets of different colors on the blanket 44.

[0039] In some embodiments, system 10 includes a drying station 64 configured to direct infrared radiation and cold air (or another gas) and / or blow hot air (or another gas) onto the surface of rubber blanket 44. In some embodiments, drying station 64 may include an infrared-based irradiation assembly (not shown) and / or an air blower 68 or any other suitable drying equipment.

[0040] In some embodiments, in drying station 64, the ink image formed on blanket 44 is exposed to radiation and / or hot air to dry the ink more thoroughly, thereby evaporating most or all of the liquid carrier and leaving only a layer of resin and colorant heated to the point of becoming a sticky ink film.

[0041] In some embodiments, system 10 includes a blanket module 70 (also referred to herein as an ITM module) comprising a rolling flexible ITM, such as blanket 44. In some embodiments, blanket module 70 includes one or more rollers 78, wherein at least one of the rollers 78 includes a motion encoder (not shown) configured to record the position of blanket 44 to control the position of segments of blanket 44 relative to corresponding printing bars 62. In some embodiments, one or more motion encoders may be integrated with additional rollers and other moving parts of system 10.

[0042] In some embodiments, the aforementioned motion encoder typically includes at least one rotary encoder configured to generate a rotation-based position signal indicating the angular displacement of the corresponding roller. It should be noted that in the context of this invention and in the claims, the terms "indicative of" and "indication" are used interchangeably.

[0043] Alternatively or concurrently, the rubber blanket 44 may include an integrated encoder (not shown) for the operation of various modules of the control system 10. One implementation of the integrated motion encoder is described in detail, for example, in PCT International Publication WO 2020 / 003088, the disclosure of which is incorporated herein by reference.

[0044] In some embodiments, the blanket 44 is guided on rollers 76, 78 and other rollers described herein, as well as on a powered tension roller, also referred to herein as a floating roller assembly 74. The floating roller assembly 74 is configured to control the slack length of the blanket 44 and its movement within... Figure 1 The image is schematically represented by a double-headed arrow. Furthermore, any stretching of the blanket 44 due to aging will not affect the ink image placement performance of the system 10, and any further slack will only need to be recovered by tensioning the floating roller assembly 74.

[0045] In some embodiments, the floating roller assembly 74 may be motorized. The configuration and operation of rollers 76 and 78 are described in more detail in, for example, U.S. Patent Application Publication 2017 / 0008272 and the aforementioned PCT International Publication WO 2013 / 132424, the disclosures of which are incorporated herein by reference in their entirety.

[0046] In some embodiments, system 10 includes a blanket tension drive roller (BTD) 99 and a blanket control drive roller (BCD) 77, which are powered by respective first and second motors (typically electric motors (not shown)) and configured to rotate about their own first and second axes, respectively.

[0047] In some embodiments, system 10 may include one or more tension sensors (not shown) disposed at one or more locations along the rubber blanket 44. The tension sensors may be integrated into the rubber blanket 44 or may be sensors located external to the rubber blanket 44, using any other suitable technology to acquire signals indicating the mechanical tension applied to the rubber blanket 44. In some embodiments, the processor 20 and additional controller of system 10 are configured to receive signals generated by the tension sensors to monitor the tension applied to the rubber blanket 44 and control the operation of the floating roller assembly 74.

[0048] In impression station 84, blanket 44 passes between impression cylinder 82 and pressure cylinder 90, the pressure cylinder being configured to carry a compressible blanket (hereinafter referred to as...). Figure 3 (As shown in the figure). In some embodiments, the motion encoder is integrated with at least one of the impression cylinder 82 and the pressure cylinder 90.

[0049] In some implementations, system 10 includes a console 12 configured to control multiple modules of system 10, such as a blanket module 70, an image forming station 60 located above the blanket module 70, and a substrate transport module 80 located below the blanket module 70 and including one or more impression stations, as will be described below.

[0050] In some embodiments, console 12 includes processor 20 (typically a general-purpose processor) having suitable front-end and interface circuitry to interface with and receive signals from the controller and controller 54 of the floating roller assembly 74 via cable 57. Alternatively or additionally, console 12 may include any suitable type of application-specific integrated circuit (ASIC) and / or digital signal processor (DSP) and / or any other suitable type of processing unit configured to perform any type of processing on the data processed in system 10.

[0051] In some embodiments, the controller 54, schematically shown as a single device, may include one or more electronic modules mounted on the system 10 at a predefined location. At least one of the electronic modules of the controller 54 may include electronic devices such as control circuitry or a processor (not shown), which are configured to control various modules and stations of the system 10. In some embodiments, the processor 20 and the control circuitry may be software-programmed to implement the functions used by the printing system and the software data may be stored in memory 22. For example, the software may be downloaded electronically to the processor 20 and the control circuitry via a network, or the software may be provided on a non-transitory tangible medium, such as an optical, magnetic, or electronic memory medium.

[0052] In some embodiments, console 12 includes a display 34 configured to display data and images received from processor 20 or input inserted by a user (not shown) using input device 40. In some embodiments, console 12 may have any other suitable configuration, such as alternative configurations of console 12 and display 34 described in detail in U.S. Patent 9,229,664, the disclosure of which is incorporated herein by reference.

[0053] In some embodiments, processor 20 is configured to display digital image 42 on display 34, the digital image including one or more segments (not shown) of image 42 and / or various types of test patterns that may be stored in memory 22.

[0054] In some embodiments, the blanket treatment station 52 (also referred to herein as a cooling station) is configured to treat the blanket by, for example, cooling the blanket and / or applying a processing fluid to and / or cleaning the outer surface of the blanket 44. At the blanket treatment station 52, the temperature of the blanket 44 can be reduced to a desired temperature level before the blanket 44 enters the image forming station 60. This treatment can be carried out by passing the blanket 44 over one or more rollers or blades configured to apply cooling and / or cleaning and / or processing fluid to the outer surface of the blanket.

[0055] In some embodiments, the blanket treatment station 52 may also include one or more rods (not shown) positioned adjacent to the printing rod 62, such that the treatment fluid can be applied to the blanket 44 by jetting, either additionally or alternatively.

[0056] In some embodiments, processor 20 is configured to receive, for example, a signal indicating the surface temperature of blanket 44 from a temperature sensor (not shown) to monitor the temperature of blanket 44 and control the operation of blanket processing station 52. Examples of such processing stations are described, for example, in PCT International Publications WO 2013 / 132424 and WO 2017 / 208152, the disclosures of which are incorporated herein by reference in their entirety.

[0057] exist Figure 1 In this example, station 52 is installed between impression station 84 and image forming station 60; however, station 52 may be installed adjacent to blanket 44 at any other or one or more suitable locations between impression station 84 and image forming station 60. As described above, station 52 may also be additionally or alternatively installed on a pole adjacent to image forming station 60.

[0058] exist Figure 1 In this example, impression cylinder 82 and pressure cylinder 90 imprint an ink image onto a target flexible substrate (such as a single sheet 50), which is conveyed from an input stack 86 to an output stack 88 by a substrate transport module 80 via an impression station 84. In this example, a rotary encoder (not shown) is integrated with impression cylinder 82.

[0059] In some embodiments, the lower running section of the blanket 44 selectively interacts with the impression cylinder 82 at the impression station 84 to imprint an image pattern onto a target flexible substrate compressed between the blanket 44 and the impression cylinder 82 by the pressure of the pressure cylinder 90. Figure 1 In the case of the simplex printing press shown (i.e., printing on one side of the sheet 50), only one printing station 84 is required.

[0060] In other embodiments, module 80 may include two or more impression cylinders (not shown) to allow one or more duplex printing locations. The configuration of two impression cylinders also enables single-sided printing at twice the speed of printing double-sided prints. Furthermore, large quantities of mixed single-sided and double-sided prints can be printed. In alternative embodiments, different configurations of module 80 can be used for printing on continuous roll substrates. For example, detailed descriptions and various configurations of duplex printing systems and systems for printing on continuous roll substrates are provided in, for example, U.S. Patents 9,914,316 and 9,186,884, PCT International Publication WO 2013 / 132424, U.S. Patent Application Publication 2015 / 0054865, and U.S. Provisional Application 62 / 596,926, the disclosures of which are incorporated herein by reference in their entirety.

[0061] As briefly described above, the sheet 50 or continuous roll substrate (not shown) is carried by module 80 from input stack 86 and passes through a gap (not shown) located between impression cylinder 82 and pressure cylinder 90. Within the gap, the surface of the blanket 44 carrying the ink image is firmly pressed against the sheet 50 (or another suitable substrate) by, for example, the compressible blanket of pressure cylinder 90, such that the ink image is imprinted onto the surface of the sheet 50 and cleanly separated from the surface of the blanket 44. The sheet 50 is then conveyed to output stack 88.

[0062] exist Figure 1 In this example, roller 78 is positioned on the running section of blanket 44 and configured to keep blanket 44 taut as it travels adjacent to image forming station 60. Additionally, it is particularly important to control the speed of blanket 44 below image forming station 60 to achieve accurate ink droplet ejection and deposition, thereby forming an image on the surface of blanket 44 through image forming station 60.

[0063] In some embodiments, the impression cylinder 82 engages and disengages from the blanket 44 periodically to transfer an ink image from the moving blanket 44 to a target substrate passing between the blanket 44 and the impression cylinder 82. In some embodiments, the system 10 is configured to apply torque to the blanket 44 using the aforementioned roller and floating roller assembly to keep the running section taut and substantially isolate the running section of the blanket 44 from mechanical vibrations occurring in the lower running section.

[0064] In some embodiments, system 10 includes an image quality control station 55 (also referred to herein as an automated quality management (AQM) system), which serves as a closed-loop inspection system integrated into system 10. In some embodiments, such as Figure 1 As shown, the image quality control station 55 can be positioned adjacent to the impression cylinder 82, and / or at any other suitable location in the system 10.

[0065] In some embodiments, the image quality control station 55 includes a camera (not shown) configured to acquire one or more digital images of the aforementioned ink image printed on the sheet 50. In some embodiments, the camera may include any suitable image sensor (such as a contact image sensor (CIS) or a complementary metal-oxide-semiconductor (CMOS) image sensor) and a scanner including a slit having a width of about one meter or any other suitable width.

[0066] In the context of this disclosure and in the claims, the terms “about” or “approximately” used for any numerical value or range indicate appropriate dimensional tolerances that allow a portion or assembly of parts to function to achieve their intended purpose, as described herein.

[0067] In some embodiments, station 55 may include a spectrophotometer (not shown) configured to monitor the quality of ink printed on sheet 50.

[0068] In some embodiments, digital images acquired by station 55 are transmitted to a processor (such as processor 20 or any other processor of station 55), which is configured to evaluate the quality of the corresponding printed image. Based on the evaluation and signals received from controller 54, processor 20 is configured to control the operation of modules and stations of system 10. In the context of this invention and in the claims, the term "processor" refers to any processing unit (such as processor 20 or any other processor or console connected to or integrated with station 55) configured to process signals received from the camera and / or spectrophotometer of station 55. It should be noted that the signal processing operations, control-related instructions, and other computational operations described herein may be implemented by a single processor or shared among multiple processors of one or more corresponding computers.

[0069] In some embodiments, station 55 is configured to inspect the quality of the printed image and test pattern to monitor various properties, such as, but not limited to, full image registration with sheet 50 (also referred to herein as image-to-substrate registration), inter-color (C2C) registration, print geometry, image uniformity, color contours and linearity, and print nozzle functionality. In some embodiments, processor 20 is configured to automatically detect geometric distortion or other errors of one or more of the aforementioned properties.

[0070] In some implementations, processor 20 is configured to analyze detected distortions in order to apply corrective actions to faulty modules, and / or to feed instructions to another module or station of system 10 to compensate for the detected distortions.

[0071] In some embodiments, system 10 may, for example, print test marks (not shown) or other suitable features at the bevels or edges of sheet 50. By acquiring images of the test marks, station 55 is configured to measure various types of distortion, such as C2C registration, image-to-substrate registration, differences in width between colors (referred herein to as “bar width difference” or “color width difference”), various types of local distortion, and front-back registration errors (in duplex printing). In some embodiments, processor 20 is configured to: (i) pick sheet 50 with distortion above a first set of predefined thresholds to, for example, a rejection tray (not shown); (ii) initiate a correction action on sheet 50 with distortion above a lower second set of predefined thresholds; and (iii) output sheet 50 with slight distortion, for example, below the second set of thresholds, to output stack 88.

[0072] In some implementations, processor 20 is configured to detect deviations in the outline and linearity of printed colors based on signals received from a spectrophotometer at station 55.

[0073] In some embodiments, the processor of station 55 is configured to determine whether to stop the operation of system 10, for example, if the distortion density exceeds a specified threshold. The processor of station 55 is also configured to initiate a correction action in one or more of the modules and stations of system 10, as described above. In some embodiments, the correction action may be implemented immediately (while system 10 continues the printing process) or offline by stopping the printing operation and addressing the problem in the corresponding module and / or station of system 10. In other embodiments, any other processor or controller of system 10 (e.g., processor 20 or controller 54) is configured to initiate a correction action or stop the operation of system 10 if the distortion density exceeds a specified threshold.

[0074] Alternatively or additionally, processor 20 is configured to receive, for example, signals from station 55 indicating additional types of distortion and problems during the printing process of system 10. Based on these signals, processor 20 is configured to automatically estimate the pattern placement accuracy level and additional types of distortion and / or defects not mentioned above. In other embodiments, any other suitable method for inspecting patterns printed on sheet 50 (or on any other substrate described above) may be used, such as using an external (e.g., offline) inspection system or any type of measuring instrument and / or scanner. In these embodiments, based on information received from the external inspection system, processor 20 is configured to initiate any suitable corrective action and / or stop the operation of system 10.

[0075] For the purpose of clarifying the invention, the configuration of system 10 is simplified and provided only by way of example. The components, modules, and stations described above in printing system 10, as well as additional components and configurations, are described in detail in, for example, U.S. Patents 9,327,496 and 9,186,884, PCT International Publications WO 2013 / 132438, WO 2013 / 132424 and WO 2017 / 208152, and U.S. Patent Application Publications 2015 / 0118503 and 2017 / 0008272, the disclosures of which are incorporated herein by reference in their entirety.

[0076] A specific configuration of system 10 is illustrated by way of example to illustrate certain problems solved by embodiments of the present invention and to demonstrate the applicability of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are by no means limited to this particular category of example systems, and the principles described herein can be similarly applied to any other category of printing systems.

[0077] Reduce the occurrence of the memory effect on the rubber blanket.

[0078] Figure 2A This is a schematic diagram illustrating the memory effect appearing on the rubber sheet 44 of the system 10 according to an embodiment of the present invention.

[0079] In some implementations, the rubber blanket 44 includes a plurality of panels 11, each panel 11 intended to receive an image, as described above. Figure 1 As described in detail above. The rubber blanket 44 also includes one or more segments 13, which are not intended to receive images and may have features for assisting the above description. Figure 1 Various types of patterns are described in the printing process. It should be noted that panel 11 is also a segment of blanket 44 (intended to receive an image), but in order to distinguish it from “segment 13” which is not intended to receive an image, the segment is referred to herein as “panel”.

[0080] In this example, each segment 13 includes a mark 15 at a predefined location, which can be used to control the blanket 44 relative to the preceding text. Figure 1 The reference positions for the movement of the station and components of system 10 described herein. Furthermore, the seam 45, which is not intended to receive ink droplets, is positioned in one of the sections 13. It should be noted that in... Figure 2A In this example, the dimensions of panel 11 and segment 13 along the X-axis of rubber sheet 44 are not proportional. In this example, the ratio between the dimensions of panel 11 and segment 13 along the X-axis may be approximately 8 (e.g., the length of panel 11 is approximately 940 mm, and the length of segment 13 is approximately 190 mm), or any other suitable ratio, such as between 5 and 20.

[0081] In the context of this disclosure and in the claims, the terms “about” or “approximately” used for any numerical value or range indicate appropriate dimensional tolerances that allow a portion or assembly of parts to function to achieve their intended purpose, as described herein.

[0082] In some cases, a printing job (also referred to herein as a printing batch) containing a large number (e.g., thousands or more) copies of a particular image produced on blanket 44 may unintentionally result in the formation of traces of the image on blanket 44. The formation of traces on the surface of blanket 44 may cause the image outline to appear in a subsequent print of another image, such as in the next printing batch. This unintentional phenomenon is also referred to herein as the “memory effect” or “ghosting” or “printing with ghosting,” which may occur on each panel 11 and in… Figure 2A In this example, it is shown as memory 16. In such cases, the outline of memory 16 may be printed on sheet 50 in subsequent batches of subsequent images (e.g., printing jobs), and may therefore degrade the quality of subsequent images printed using the same blanket 44. It should be noted that memory 16 typically appears in each panel 11 of blanket 44, but for clarity of presentation and conceptual clarity, memory 16 is shown in… Figure 2A It only appears on one panel, 11.

[0083] The size of the memory effect and appearance can be influenced by various factors, such as, but not limited to, the number of times the blanket is wound (see below). Figure 2B The factors described in the text include the number of image copies in the printing operation, ink type (e.g., formulation), color and blanket temperature, coverage levels of different ink colors in the image (e.g., an image with coverage of 60% K, 60% C, 60% M, and 60% Y will generally have a greater memory effect compared to an image with coverage of 40% C, 27% M, and 27% Y), blanket handling process, temperature and chemicals used in blanket handling station 52, magnitude of various types of registration errors occurring during printing, uniformity of the image formed on blanket 44, service time and aging of blanket 44, type of target substrate (e.g., uncoated sheet 50, coated sheet 50, or continuous roll with a layered structure), and other system-related and process-related parameters. For example, when comparing the memory effect between two systems 10, the system with better image uniformity and lower registration error is expected to have a greater memory effect.

[0084] Figure 2B This is a schematic illustration of the memory effect that occurs on the rubber blanket 44 when an intentional offset is applied to each copy of the image generated during each corresponding rotation of the rubber blanket 44 according to an embodiment of the present invention.

[0085] To describe the following implementation, system 10 includes a printing assembly incorporating an image forming station 60, an impression station 84, and a blanket module 70. In this example, the printing assembly is controlled by processor 20. As described above... Figure 1 As described above, the rubber blanket 44 includes a flexible member formed as a loop. Furthermore, as stated above... Figure 2A As described herein, memory traces typically appear in each panel 11 of the rubber blanket 44, but for clarity of presentation and conceptual clarity, the memory traces described herein are... Figure 2B It appears only on one panel 11, which is in Figure 2B It is also referred to as "Given Panel 11".

[0086] In some implementations, the blanket module 70 is configured to rotate the blanket 70 for multiple rotations, and for each panel 11 and each rotation, the processor 20 controls the printing assembly to produce a copy of the image, and then transfers the image from the panel 11 to the sheet 50. Subsequently, the blanket 44 undergoes various processes in the blanket processing station 52 such that, in the next rotation, the same panel 11 is ready to receive ink droplets from the image forming station 60 to produce the next copy of the image.

[0087] In an example of a given panel 11 of a blanket 44, the processor 20 is configured to control the printing assembly to produce a first image at a first position on the blanket 44 during a first rotation, and subsequently move the blanket 44 in a movement direction 94 to transfer the first image to a first sheet 50 (as described above). Figure 1 The input stack 86 shown is received. (For example...) Figure 2B As shown, after the first image is transferred to the first sheet 50, unwanted imprints or marks of memory 16a will remain on the rubber blanket 44.

[0088] In some embodiments, during a subsequent second turn of the blanket 44, the processor 20 is configured to control the printing assembly to produce a second image on a given panel 11 at a second location, which differs from the first location of the first image described above. Subsequently, the processor 20 controls the printing assembly to move the blanket 44 in a movement direction 94 to transfer the second image to a subsequent second sheet 50, which also originates from the first image described above. Figure 1 The input stack 86 shown is received.

[0089] exist Figure 2B In one instance, after the second image is transferred to the second sheet 50, undesirable traces of memory 16b remain on the rubber blanket 44. For example... Figure 2BAs shown, the processor 20 controls the printing assembly to apply the same technique in subsequent turns of the blanket 44, each turn unintentionally generating additional memory 16 on the blanket 44, such as memory 16c generated in the third turn.

[0090] In some implementations, processor 20 is configured to specify an intentional offset 18 of the second position relative to the first position. Figure 2B In one example, an intentional offset is shown between memory 16a and memory 16b, which correspond to the positions of the first and second images, respectively.

[0091] In some implementations, the location of memory 16b at least partially overlaps with the location of memory 16a, such as Figure 2B As shown in the example. However, in other embodiments, the processor 20 may set the offset 18 large enough that the imprints of memories 16a and 16b may appear separate from each other. It should be noted that the appearance of the memories is determined by the amount of overlap between the images produced on the surface of a given panel 11 during the respective turns of the rubber blanket 44. Figure 2A As shown, with Figure 2B Compared to the size of memory 16a-16c, memory 16 is significantly larger.

[0092] In some embodiments, the processor 20 is configured to achieve offset 18 by controlling the image forming station 60 to apply (e.g., eject) ink droplets onto the surface of panel 11 at a predefined delay relative to the initially anticipated ejection time. In such embodiments, delayed ejection causes imprint memory 16b to appear to the right of memory 16a as the blanket moves in direction 94. Figure 2B As shown. Similarly, processor 20 can control the image forming station to advance the ejection of ink droplets. In other words, controlling image forming station 60 to eject ink droplets earlier than initially expected, such that the imprint of memory 16b may appear to the left of memory 16a (as shown). Figure 2B (The position of memory 16b shown is opposite to that of memory 16a).

[0093] In the context of this disclosure, the term "initially intended" refers to a specified ejection time of the ink droplets without causing a positional shift of the given image produced on the corresponding panel 11.

[0094] In some implementations, processor 20 is configured to calculate the movement of blanket 44, which will at least partially and generally completely compensate for the offset when transferring the second image to the second sheet 50. (The following is in...) Figure 3One implementation of such an embodiment is described in detail below. The processor 20 is configured to control the printing assembly to move the blanket 44 according to the calculated movement to transfer the second image onto the second sheet 50 without causing registration errors between the image and the substrate.

[0095] In some embodiments, the processor 20 may use marker 15 to control the position of each image generated on each panel 11 during each rotation of the blanket 44. In other embodiments, the processor 20 may use any other reference location on the blanket 44 (e.g., the position of one or more fibers of the blanket 44) to control the position of each image generated on each panel 11 during each rotation of the blanket 44.

[0096] exist Figure 2B In one example, processor 20 controls the printing assembly to shift the second image by 18 (e.g., by delaying the ejection time of the second image), and subsequently controls the movement of the blanket 44 (e.g., by reducing its speed) to compensate for the shift, such that the first and second images are transferred to the first and second sheets 50 at the same positions, respectively. (The following is in...) Figure 3 The paper describes in detail one of the compensation implementation techniques.

[0097] exist Figure 2B In one example, an intentional offset (e.g., offset 18) is performed only along the X-axis, for example, between images sequentially generated during different rotations of the blanket 44. In other embodiments, the processor 20 is configured to specify any other suitable offset, which may be parallel or not parallel to the direction of movement 94. (See below for further details.) Figure 2D An example implementation of an offset that is not parallel to the X-axis is described in detail. Furthermore, the offset 18 can have any suitable size (also referred to as the step size in this document), for example, between 1 μm and 10 mm.

[0098] In some embodiments also partially described above, the size of the memory imprint on the rubber blanket 44 is reduced by changing the position of the image produced on a given panel 11 during different rotations of the rubber blanket 44. Figure 2A and Figure 2B In the examples, compared to Figure 2B Memory 16a-16c, Figure 2A Memory 16 appears black (i.e., darker). Different gray levels indicate that Memory 16 has a more pronounced imprint on the surface of the rubber blanket 44 than Memory 16a-16c.

[0099] Figure 2C This is a schematic illustration of the intentional offset of different copies of an image generated on the surface of different panels 11 of the rubber blanket 44 according to another embodiment of the invention.

[0100] In some embodiments, the rubber blanket 44 includes panels 11a and 11b separated by segment 13 along the X-axis. The processor 20 can use marker 15 or any other suitable reference position to position the first image generated on panel 11a and the second image generated on panel 11b.

[0101] exist Figure 2C In this example, the first image and the second image are generated at corresponding first and second positions on the surfaces of panels 11a and 11b, respectively, and the processor 20 controls the printing assembly to generate the second image at a shifted position relative to the position of the first image, as will be described in detail below. Subsequently, the printing assembly moves the blanket 44 to transfer the first image to the first sheet 50 and the second image to the second sheet 50. It should be noted that in Figure 2C In the instances and with Figure 2A and Figure 2B The process described herein is reversed; the first and second images are generated during the same rotation of the rubber blanket 44. After the transfer of the first and second images, unwanted imprints of memories 23a and 23b are formed on the surfaces of panels 11a and 11b, respectively. Note that the positions of memories 23a and 23b indicate the positions of the first and second images described above.

[0102] In some embodiments, the rubber blanket 44 includes lines 25a and 25b that respectively indicate the left and right edges of panel 11a. Similarly, lines 25c and 25d indicate the left and right edges of panel 11b, respectively. Figure 2C In the example, the edge of memory 23a appears to touch line 25a, while memory 23b appears to be shifted by offset 24 relative to line 25c along the X-axis due to the position of the second image. The direction of offset 24 is also referred to in this document as the rightward direction (opposite to the leftward direction).

[0103] Based on the above Figure 2B The technique described herein involves processor 20 configured to calculate the movement of blanket 44, which will compensate for offset 24 when transferring an image generated on panel 11b to corresponding sheet 50. In some embodiments, processor 20 is configured to control the printing assembly to move blanket 44 according to the calculated movement to transfer an image generated on panel 11b to corresponding sheet 50 without causing registration errors of the image to the substrate or affecting its size.

[0104] In some embodiments, the rubber blanket has eleven (11) panels (or any other suitable number of panels), and the processor 20 is configured to transfer the above text in Figure 2BThe techniques described herein are applied to each pair of images generated on a corresponding pair of adjacent panels 11. In this example, processor 20 controls the printing assembly to shift the position of the image in panel 11b by an offset 24 of approximately 60 μm (or another offset with any other suitable size and orientation). Processor 20 may apply the same techniques to each pair of images generated separately on adjacent panels. For example, between the second image (of panel 11b) and a third image generated on a third panel (not shown), which is adjacent to and behind panel 11b.

[0105] In such embodiments, the third image is shifted approximately 120 μm to the right relative to the left edge of the third panel (and relative to the position of the first image within the panel) (achieved by applying two 60 μm shifts between the first and third images). Furthermore, after the first rotation is completed, the eleventh image generated on the eleventh panel is positioned approximately 600 μm offset relative to the left edge of the eleventh panel and also relative to the first image (within each respective panel 11).

[0106] Subsequently, the image generated in panel 11a during the second rotation is positioned at an offset of approximately 660 μm (i.e., 11 shifts of approximately 60 μm) relative to the position of the first image generated on panel 11a during the first rotation. In other words, after the image generated on panel 11a during the second rotation is transferred (to the corresponding sheet 50), a memory imprint of this image appears in panel 11a at a position shifted approximately 660 μm relative to memory 23a. In other words, the step size along the X-axis between adjacent images generated on the surface of each panel 11 during the successive rotations of the blanket 44 is approximately 660 μm.

[0107] In this embodiment, after all images generated during the second rotation of the rubber blanket 44 are transferred to the corresponding sheet 50, the offset between the first memory and the second memory in each panel 11 of the rubber blanket 44 is approximately 660 μm. Similarly, after all images generated during the third rotation of the rubber blanket 44 are transferred to the corresponding sheet 50, the offset between the second memory and the third memory in each panel 11 of the rubber blanket 44 is also approximately 660 μm.

[0108] In some implementations, the processor 20 is configured to define, for example, the step size along the X-axis, by the total amount of positional shift of the image generated on the panel 11 of the blanket 44. Figure 2B and Figure 2CIn one example, when applying an image shift equal to offset 24 between adjacent panels, processor 20 can define a step size of approximately 60 mm along the X-axis. In other words, after applying offset 24 to approximately 1,000 consecutive images generated on the surfaces of 1,000 consecutive panels 11, processor 20 is configured to reverse the shift direction. As described above... Figure 2B As described above, processor 20 can control the displacement direction by delaying or advancing the ejection of ink droplets relative to the initially anticipated ejection time. Furthermore, using the above-described... Figure 2B In addition to reversing the transfer direction, the processor 20 is also configured to: (a) calculate the movement of the blanket 44, which will compensate for the reversed offset when transferring the image to the surface of the corresponding panel 11, and (b) control the printing assembly to move the blanket 44 according to the calculated movement to transfer the image to the surface of the corresponding panel 11.

[0109] It should be noted that the size of the sheet 50 may be varied based on the requirements of the end customer of the printed product. In some embodiments, the limit of the cumulative intentional step size (e.g., about 60 mm as described above) depends on the size of the sheet 50 to prevent the impression station 84 from joining the seam 45 to the sheet 50. In other words, a smaller size of the sheet 50 along the X-axis allows for a cumulative intentional step size greater than about 60 mm. For example, based on calculations and experimental data: (i) when the size of the sheet 50 along the X-axis is about 750 mm, the maximum permissible step size can be increased from about 60 mm to about 80 mm; (ii) when the size of the sheet 50 along the X-axis is about 700 mm, the maximum permissible step size can be increased to about 130 mm; and (iii) when the size of the sheet 50 along the X-axis is about 650 mm, the maximum permissible step size can be increased to about 180 mm.

[0110] In such implementations, processor 20 is configured to control the printing assembly to maintain an image shift of approximately 60 μm in each panel (e.g., offset 24), and to increase the shift amount before reversing the shift direction. In one of the examples described above, when the sheet 50 is approximately 650 mm in size along the X-axis, the maximum permissible step size is approximately 180 mm. In this example, processor 20 is configured to control the printing assembly to apply offset 24 to approximately 3,000 (instead of approximately 1,000 as described above) consecutive images generated on the surfaces of approximately 3,000 consecutive panels 11. After applying approximately 3,000 offsets 24, processor 20 is configured to reverse the shift direction to apply offset 24 to approximately 3,000 consecutive images generated on the surfaces of approximately 3,000 consecutive panels 11 in the reverse direction. In other words, the step size and the number of consecutive images are increased threefold.

[0111] In some implementations, the processor 20 is configured to control the shift and direction reversal operation by applying a threshold to the step size (e.g., about 180 mm in the example described above) and / or to the number of images generated on the corresponding panel before the reverse shift direction (e.g., about 3,000 in the example described above).

[0112] In principle, the image is only shifted during each or multiple rotations of the blanket 44; that is, the image is not shifted on every panel. However, by applying a small shift (e.g., about 60 μm) to each panel (which amounts to a large offset for each panel in each rotation (e.g., about 660 μm)), the memory effect on the blanket 44 is reduced without deteriorating the image uniformity and registration performance of the system 10 (e.g., C2C and image-to-substrate registration error).

[0113] Figure 2D This is a schematic illustration of the intentional offset of a corresponding copy of an image generated on the surface of panel 11c of rubber blanket 44 according to another embodiment of the invention.

[0114] As mentioned above Figure 2B and Figure 2C As described above, processor 20 controls the printing assembly to shift the position of the image along the X-axis by a predefined offset (such as described above). Figure 2B Offset 18).

[0115] exist Figure 2D In the example embodiment shown, processor 20 is configured to control the printing assembly to shift the position of an image (e.g., a copy of a given image) produced on the surface of panel 11c in any suitable direction other than parallel to the X-axis, and by any suitable step size relative to the step size applied to a previous image produced on the surface of panel 11c during a previous blanket rotation. For example, images 30 and 31 are produced during a corresponding first and second rotation of the blanket 44 on the surface of panel 11c.

[0116] In some implementations, the processor 20 controls the printing assembly to shift the position of image 31 relative to the position of image 30 along the X and Y axes. More specifically, image 31 is shifted along a negative direction parallel to the X-axis (i.e., opposite to the arrow direction of the X-axis) and a positive direction parallel to the Y-axis. Subsequently, for example, in the next rotation of the blanket 44, image 32 is generated at a position maintaining the same shift direction of image 31 relative to image 30 but using different step sizes on the X and Y axes.

[0117] In some implementations, the processor 20 controls the printing assembly to shift the position of image 33 relative to the position of image 32 in a negative direction parallel to the X and Y axes. The same shift direction (but not necessarily the corresponding step size) is maintained in the positions of subsequent images (including the position of image 35) generated during subsequent corresponding rotations of the blanket 44.

[0118] In some implementations, when the position of image 36 is shifted relative to the position of image 35, the shift direction along the Y-axis is reversed again, and the same shift direction is maintained until image 37 is generated on panel 11c of blanket 44.

[0119] In some implementations, the processor 20 controls the printing assembly to shift the positions of the images 30-33 and 35-37 so that the shifted position of the image produced on the panel 11c during the corresponding rotation of the blanket 44 is in the shape of a wave 38.

[0120] In some embodiments, the processor 20 controls the printing assembly to repeatedly shift the position of the image generated on the panel 11c so as to repeat the shape of the wave 38 along the panel, and subsequently maintain or change the shape of the wave 38 when the shifting direction is reversed on the X-axis. It should be noted that the wave 38 may have a regular shape or an irregular shape.

[0121] In other embodiments, instead of generating an image based on the shape of wave 38, processor 20 is configured to control the printing components to shift the position of the image generated during each rotation of blanket 44 according to any other regular pattern (e.g., a spiral pattern) or irregular pattern.

[0122] Figure 3 This is a schematic side view of an apparatus according to an embodiment of the present invention for compensating for positional offset of an image generated on a rubber blanket 44 when transferring an image onto a sheet.

[0123] exist Figure 3 In some instances, the device specifically includes the above-mentioned Figure 1 The BCD 77, BTD 99, and imprint station 84, controlled by processor 20, are used to process the above text. Figure 2C Several offsets (such as offset 24) shown and described in detail below are compensated for. It should be noted that the following text... Figure 3 The techniques described in [the text] can also be applied, with necessary modifications, to the above-mentioned [text]. Figure 2B The offset 18 shown or any other offset and / or shift shown in this disclosure shall be compensated.

[0124] As mentioned above Figure 1As described above, processor 20 is configured to control BCD 77 and BTD 99 to move the blanket in direction 94 at a pre-assigned speed. The term "pre-assigned" indicates that the speed of blanket 44 is not predefined as a constant value, but is adjusted to compensate for the offset described above. Blanket 44 moves between BTD 99 and BCD 77 to generate an image on surface 44a of panel 11. Subsequently, blanket 44 moves from BCD 77 to impression station 84 to transfer the image generated on each panel 11 to the corresponding sheet 50, and after image transfer, blanket 44 moves between impression station 84 and BTD 99 to begin the next rotation, as described above. Figures 2A to 2C As described in the text.

[0125] Reference is now made to a clockwise rotating pressure roller (PC) 90. In some embodiments, a compressible rubber sheet (CB) 19 is positioned to make circumferential contact with the PC 90 and to engage the wall 41 of the gap 43 of the PC 90 in order to maintain tension on the circumference of the PC 90.

[0126] In some implementation schemes, such as Figure 3 As shown, gap 43 faces blanket 44 only when section 13 moves between PC 90 and impression cylinder (IC) 82. Note that in this position, sheet 50 is not fed between PC 90 and IC 82. Note that in this example, the area of ​​gap 43 is approximately one-fifth of the total area of ​​PC 90.

[0127] In some implementations, as the panel 11 and sheet 50 move between PC 90 and IC 82, CB 19, which is in circumferential contact with PC 90, is configured to press the rubber blanket 44 against the sheet 50 in order to transfer an image from surface 44a to the sheet 50.

[0128] Referring now to IC 82, which rotates counterclockwise and has twice the diameter relative to the diameter of PC 90 in this example.

[0129] In some implementations, IC 82 has two opening angles 47, each including a clamp 49 configured to clamp sheet 50 and move the sheet between PC 90 and IC 82 to transfer an image from surface 44a of panel 11 to sheet 50, as described above.

[0130] In some embodiments, segments 51 and 53 on the circumference of IC 82 are configured to press sheet 50 against blanket 44 to receive an image from surface 44a of panel 11. It should be noted that during image transfer, the first sheet 50 is fitted onto segment 51, and after image transfer, the first sheet 50 is moved by substrate transport module 80 toward output stack 88. Furthermore, in this example, during operation of impression station 84, gap 43 and opening angle 47 generally face each other, and simultaneously, as blanket 44 moves in direction 94, segment 13 of blanket 44 passes between PC 90 and IC 82. Subsequently, a second sheet 50 (not shown) is held and moved by a holder 49 at another (e.g., opposite) opening angle 47 to fit onto segment 53 to transfer the next image from next panel 11 to the second sheet 50. For example, the operation of the imprint station 84 and its components is described in more detail in PCT International Publication No. WO 2020 / 099976A1, granted to Lean et al., the disclosure of which is incorporated herein by reference.

[0131] Now for reference Figure 3 An overall view. As mentioned above... Figure 2B and Figure 2C As described, processor 20 is configured to calculate the movement of blanket 44, which will typically compensate for the offset when transferring the displaced image to the corresponding sheet 50.

[0132] In some implementations, the processor 20 controls the BCD 77 and BTD 99 to adjust the speed of the blanket 44 according to the calculated movement in order to transfer the displaced image to the corresponding sheet 50 without causing registration errors between the image and the substrate.

[0133] Figure 3 One possible implementation of offset compensation is illustrated. In some embodiments, the processor 20 is configured to define, for example, a step 39 between dashed lines 46a and 46b, the step indicating the total amount of positional displacement of the image generated on the panel 11 of the blanket 44. According to... Figure 2B , Figure 2C and optional Figure 2D In an example implementation, the processor 20 can define the size of the step 39 as approximately 60 mm along the X-axis.

[0134] exist Figure 3 In the example, arrows 48a and 48b are used to indicate the adjusted speed of the blanket 44 relative to the nominal speed of the blanket, where arrow 48a indicates a higher speed of the blanket 44 relative to the nominal speed, and arrow 48b indicates a lower speed of the blanket 44 relative to the nominal speed.

[0135] As mentioned above Figure 2C As shown and described, the second image is shifted to the right along the X-axis so that memory 23b appears at offset 24 relative to line 25c. In other words, the position of memory 23b is shifted by an amount of offset 24 (e.g., about 60 μm) relative to its nominal position with respect to the direction of movement 94. In some embodiments, processor 20 controls BCD 77 and BTD 99 to increase the speed of blanket 44 to a speed higher than the aforementioned nominal speed to compensate for offset 24 and thereby transfer the image to the same position on all sheets 50.

[0136] In other words, when the position on the image is shifted behind its nominal position, the processor 20 adjusts the speed of the blanket 44 to exceed the nominal speed in order to compensate for the shifted position of the image generated by the image forming station 60 on the surface 44a of the blanket 44. Figure 3 These implementation schemes are shown in the figure.

[0137] In one embodiment, in response to the application of offset 24, the seam 45 of the rubber blanket 44 moves in direction 48a at a relative velocity, i.e., at a velocity higher than the nominal velocity of the rubber blanket 44. In another embodiment, in response to the application of offset in the direction opposite to offset 24, the seam 45 moves in direction 48b at a relative velocity, i.e., at a velocity lower than the nominal velocity of the rubber blanket 44. It should be noted that in Figure 3 In the example, the rubber blanket 44 always moves in direction 94, while arrows 48a and 48b indicate the relative velocity of the rubber blanket 44 compared to its nominal velocity.

[0138] In some implementation schemes, based on the above... Figure 2C In the implementation described herein, processor 20 controls BCD 77 and BTD 99 to adjust the speed of the blanket 44 in order to compensate for a 60 μm offset in each panel 11 of the blanket 44. It should be noted that when gap 43 and opening angle 47 face each other and seam 45 moves between PC 90 and IC 82, processor 20 controls the position of seam 45 within the range of step 39, i.e., between dashed lines 46a and 46b.

[0139] Figure 4 This is a flowchart schematically illustrating a method for reducing the occurrence of memory effect in the rubber blanket 44 according to an embodiment of the present invention.

[0140] The method begins with a first image printing step 100, in which the processor 20 controls the printing components to a first position (such as the position of memory 16a on the panel 11 of the blanket 44, as described above). Figure 2BThe first image is generated at point 94, and then the rubber blanket 44 is moved in direction 94 to transfer the first image from panel 11 to first sheet 50, as shown below. Figure 1 and Figure 2B As described in detail in [the text].

[0141] At offset specification step 102, processor 20 specifies an offset 18 for the second image intended to be generated at a second position on panel 11 of blanket 44. Figure 2B In the example, the second position includes the position of memory 16b, which is different from the first position, such as the position of memory 16a, as described above. Figure 2B As described in detail in [the text].

[0142] At compensation calculation step 104, processor 20 calculates the movement of blanket 44, which will at least partially and generally completely compensate for offset 18 when transferring the second image to second sheet 50, as described above. Figure 2B As described in detail in [the text].

[0143] At the second image printing step 106, the processor 20 controls the printing assembly to produce the second image and moves the blanket 44 according to the calculated movement to transfer the second image onto the second sheet 50, as described above. Figure 2B As described in detail in [the text].

[0144] In some implementations, the first image and the second image are copies of a given image, and the location of memory 16b (indicating the location of the second image) partially overlaps with the location of memory 16a (indicating the location of the first image).

[0145] As mentioned above Figure 1 As described above, the blanket 44 has the shape of a continuous blanket loop and rotates to perform multiple revolutions. In some embodiments, during the first revolution of the blanket 44, the processor 20 controls the printing assembly to produce a first image by positioning the blanket 44 at a first position relative to the image forming station 60. During the second revolution of the blanket 44, the processor 20 controls the printing assembly to produce a second image by positioning the blanket 44 at a second position relative to the image forming station, as described above. Figure 2B As described in detail in [the text].

[0146] In some implementation schemes, as described above Figure 2C As shown and described in detail above, after the generation of the first image (e.g., during the first rotation of the blanket 44) and before the generation of the second image (e.g., during the second rotation of the blanket 44), the processor 20 controls the printing assembly to generate a third image on the blanket 44 at a third position. Figure 2CIn this example, memory 23a indicates the position of the first image, and memory 23b indicates the position of the third image, which is shifted (e.g., offset 24) relative to its intended position. Processor 20 is also configured to calculate a movement of blanket 44 that will compensate for the offset 24 when transferring the third image to the third sheet 50. Processor 50 controls the printing assembly to move blanket 44 according to the calculated movement to transfer the third image to the third sheet 50.

[0147] In some implementations, an intentional offset (e.g., offset 18 or offset 24) is specified along the X-axis parallel to the direction of movement 94, as described above. Figure 2B and Figure 2C As shown and described in detail.

[0148] In alternative implementations, the intentional offset may be specified in any direction or in a combination of movement along the X and Y axes, and may be specified for a constant or varying step size, as described below. Figure 2D As described in detail in [the text].

[0149] Although the embodiments described herein are primarily aimed at digital printing using flexible intermediate transfer components, the methods and systems described herein can also be used in other applications, such as any category of printing systems and processes having any suitable type of intermediate equipment (e.g., components) for receiving and transferring images to a target substrate.

[0150] It should be understood that the embodiments described above are cited by way of example, and the invention is not limited to what has been specifically shown and described above. Rather, the scope of the invention includes both combinations and sub-combinations of the various features described above, as well as variations and modifications of the features that would occur to those skilled in the art upon reading the foregoing description and that are not disclosed in the prior art. Documents incorporated herein by reference shall be considered an integral part of this application; however, in the event of any conflict between any terminology defined in these incorporated documents and the definitions expressly or implicitly made herein, only the definitions in this specification shall be considered.

Claims

1. A printing method, the method comprising: A first image is generated at a first position on a movable intermediate transfer unit (ITM) of the printing system, and the ITM is moved to transfer the first image to a first substrate. as well as For a second image intended to be generated on the ITM at a second location different from the first location: Specify an intentional offset of the second position relative to the first position, wherein the intentional offset is applied between images generated on the same panel of the ITM during different rotations of the ITM; The movement of the ITM is calculated, which will at least partially compensate for the intentional offset when transferring the second image to the second substrate, wherein the calculation includes determining a speed adjustment of the ITM relative to the nominal speed of the ITM to compensate for the intentional offset; as well as The second image is generated at the second position with the intentional offset, and the ITM is moved according to the calculated movement by adjusting the speed of the ITM relative to the nominal speed to compensate for the intentional offset, thereby transferring the second image onto the second substrate.

2. The method of claim 1, wherein the first image and the second image are copies of a given image generated on the same panel of the ITM.

3. The method according to any one of claims 1 and 2, wherein the second position covered by the second image partially overlaps with the first position covered by the first image on the same panel of the ITM.

4. The method according to any one of claims 1 and 2, wherein the ITM comprises a closed loop, the closed loop being rotatable, and wherein: (i) During the first rotation of the ITM, the first image is generated by positioning the ITM at the first position relative to the image forming station, and (ii) During the second rotation of the ITM, the second image is generated on the same panel by positioning the ITM at the second position relative to the image forming station.

5. The method of claim 4, further comprising, after generating the first image and before generating the second image: (i) generating a third image on the ITM at a third position, the third position being shifted relative to a desired position of the third image; (ii) calculating an additional movement of the ITM that will at least partially compensate for the shift when transferring the third image to the third substrate; and (iii) moving the ITM according to the calculated additional movement by adjusting the speed of the ITM relative to the nominal speed to transfer the third image to the third substrate.

6. The method according to any one of claims 1 and 2, wherein the intentional offset is specified in a direction parallel to the direction of movement of the ITM.

7. The method according to any one of claims 1 and 2, wherein the intentional offset is specified in a direction not parallel to the direction of movement of the ITM.

8. The method of any one of claims 1 and 2, wherein the intentional offset of the second position is performed along a first direction, and the method comprises: For multiple third images intended to be generated on the ITM at multiple third positions, which are respectively different from the first position and the second position: (i) specifying an additional intentional offset of the third position along the first direction based on a predefined step size, (ii) calculating multiple third movements of the ITM that will at least partially compensate for the additional intentional offset by determining a speed adjustment of the ITM relative to the nominal speed when transferring the third image to the third substrate, respectively, and (iii) generating the third image and moving the ITM according to the calculated movements by adjusting the speed of the ITM relative to the nominal speed to transfer the third image to the third substrate, respectively.

9. The method of claim 8, wherein the first substrate, the second substrate, and the third substrate have a given size at least along the first direction, and wherein at least the predefined step size depends on the given size.

10. The method of claim 8, further comprising, after applying the intentional offset and the additional intentional offset and generating and transferring the first image, the second image and the third image according to the predefined step size, performing the intentional offset and the additional intentional offset in a second direction other than the first direction.

11. A printing system, the system comprising: A printing assembly configured to: (i) generate a first image at a first position on a movable intermediate transfer member (ITM) of a printing system, and move the ITM to transfer the first image to a first substrate; and (ii) generate a second image on the same panel of the ITM at a second position different from the first position during different rotations of the ITM, and move the ITM to transfer the second image to a second substrate. as well as A processor configured to: (i) specify an intentional offset of the second position relative to the first position; (ii) calculate a movement of the ITM that will at least partially compensate for the intentional offset by determining a speed adjustment of the ITM relative to a nominal speed when transferring the second image to the second substrate; and (iii) control the printing assembly to move the ITM by adjusting the speed of the ITM relative to the nominal speed according to the calculated movement to transfer the second image to the second substrate.

12. The printing system of claim 11, wherein the first image and the second image are copies of a given image produced on the same panel of the ITM.

13. The printing system of any one of claims 11 and 12, wherein the processor is configured to specify the intentional offset of the second position covered by the second image to partially overlap with the first position covered by the first image on the same panel of the ITM.

14. The printing system according to any one of claims 11 and 12, wherein the ITM comprises a closed loop, the closed loop being rotatable, and wherein: (i) during the first rotation of the ITM, the processor is configured to control the printing assembly to generate the first image by positioning the ITM at the first position relative to the image forming station, and (ii) during the second rotation of the ITM, the processor is configured to control the printing assembly to generate the second image on the same panel by positioning the ITM at the second position relative to the image forming station.

15. The printing system of claim 14, further comprising, after the generation of the first image and before the generation of the second image, the processor being configured to control the printing component to: (i) generate a third image on the ITM at a third position, the third position being shifted relative to a desired position of the third image; (ii) calculate an additional movement of the ITM that will at least partially compensate for the shift when transferring the third image to the third substrate; and (iii) move the ITM by adjusting its speed relative to the nominal speed according to the calculated additional movement to transfer the third image to the third substrate.

16. The printing system according to any one of claims 11 and 12, wherein the processor is configured to specify the intentional offset in a direction parallel to the movement direction of the ITM.

17. The printing system according to any one of claims 11 and 12, wherein the processor is configured to specify the intentional offset in a direction not parallel to the movement direction of the ITM.

18. The printing system of any one of claims 11 and 12, wherein the processor is configured to specify the intentional offset of the second position along a first direction, and includes, for a plurality of third images intended to be generated on the ITM at a plurality of third positions, respectively different from the first position and the second position, the processor being configured to: (i) specify an additional intentional offset of the third position along the first direction based on a predefined step size, (ii) calculate a plurality of third movements of the ITM that will at least partially compensate for the additional intentional offset when the third image is transferred to a third substrate, respectively, and (iii) generate the third image and move the ITM by adjusting the speed of the ITM relative to the nominal speed according to the calculated movement to transfer the third image to the third substrate, respectively.

19. The printing system of claim 18, wherein the first substrate, the second substrate, and the third substrate have a given size at least along the first direction, and wherein at least the predefined step size depends on the given size.

20. The printing system of claim 18, further comprising, after applying the intentional offset and the additional intentional offset and generating and transferring the first image, the second image and the third image according to the predefined step size, the processor being configured to perform the intentional offset and the additional intentional offset in a second direction other than the first direction.

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