Patent Publication Number: US-2021178784-A1

Title: Printing systems and associated structures and methods having ink drop deflection compensation

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/411,982 filed on May 14, 2019, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     At least one embodiment of the present invention pertains to a vacuum conveyor system for inkjet printing applications. More specifically, at least one embodiment of the present invention pertains to vacuum conveyor printing systems, and associated structures and methods that mitigate ink drop deflection. 
     BACKGROUND 
     Vacuum conveyor systems in inkjet printing applications can be used for flattening, securing and conveying substrates, to ensure accurate reproduction of an image to be printed on the substrate. Such vacuum conveyor systems typically include a perforated transfer belt and a perforated support table, through which a vacuum can be applied to generate adhesion forces between the substrate and the transfer belt. One of the problems associated with this configuration is related to the presence of open perforations through the transfer belt and the support table near the periphery of the conveyed substrate. During the drop jetting process, the flow of air through these open perforations can induce a drag force on the falling ink drops, which can make the ink drops deviate from their designated landing location. This effect is called drop deflection. 
     Some vacuum conveyor systems have been disclosed to prevent the flow of applied vacuum through open perforations that are not covered by the substrates. For instance, some vacuum conveyor systems can be adjusted for the media size along the transverse direction, by separating the vacuum chamber into different compartments, which can be independently opened or closed, such as to eliminate the flow of applied vacuum on one or both sides of the substrate as the substrate is transferred through the printing area. Other vacuum conveyor systems can control the active width of a print chamber in a stepless manner. 
     Furthermore, some vacuum conveyor systems have been disclosed to address the transient nature of substrate passages, such as with respect to the space between two adjacent substrates as they are transported through the printing system. For instance, at least one vacuum conveyor system has been disclosed that synchronizes the timing of the feeding of the sheets with the position of belt holes, to ensure that there are no openings in the gap between adjacent substrates. However, this procedure only works if the gap between boards, plus the board length, is a multiple of the distance between belt holes along the process direction. As a result, this procedure limits the allowable perforation patterns, the substrate dimensions, and the gap between sheets. In an alternate system, solid inter-copy gaps are employed to prevent this effect, but is limited in terms of format size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments of the present invention are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements. 
         FIG. 1  is a simplified schematic diagram of an illustrative printing system having drop deflection compensation, including a conveyor system having a perforated platen, a plurality of printheads, a substrate delivery system, and a vacuum delivery system. 
         FIG. 2  is a schematic view of an illustrative workpiece, such as having a characteristic length, width, and thickness, and opposing surfaces, in which the workpiece can include one or more non-planar features. 
         FIG. 3  is a partial cutaway view of an illustrative printing system having a perforated vacuum platen and a conveyor, in which applied vacuum near the periphery of a printing region can result in ink drop deflection. 
         FIG. 4  is a side view of an illustrative printing system having drop deflection compensation. 
         FIG. 5  a detailed partial perspective view of an illustrative conveyor assembly associated with a printing system having drop deflection compensation. 
         FIG. 6  is a plan view of an illustrative printing system having drop deflection compensation, wherein having a plurality of print bars, such as including staggered printheads. 
         FIG. 7  is an end view showing an illustrative conveyor drive mechanism, and showing one or more printheads within a print bar. 
         FIG. 8  is a schematic end view of a workpiece located within a printing region of an illustrative printing system having a printer vacuum table that includes a plurality of vacuum zones, in which an applied vacuum can be disabled for outer transverse non-printing regions. 
         FIG. 9  is a side schematic view of a workpiece located within a printing region of an illustrative printing system having a printer vacuum table, in which the vacuum table is configured to apply vacuum to a substrate from a vacuum manifold located below the printer table surface, in which more air flow is induced in non-printing regions, and less air flow is induced in regions that are substantially aligned with the printheads, 
         FIG. 10  is a simplified plan view of an illustrative platen for a printing system, which is configured to induce high air flow levels in non-printing regions, and low air flow levels in printing regions, 
         FIG. 11  is a detailed view if an illustrative platen for a printing system, which is configured to induce high air flow levels through platen apertures in non-printing regions, and low air flow levels through platen apertures in printing regions, wherein the platen apertures are configured in rows to generally align with apertures defined through a transfer belt. 
         FIG. 12  is a plan view of an illustrative modular platen plate that is configured to induce high air flow levels in non-printing regions, and low air flow levels in printing regions. 
         FIG. 13  is a plan view of an alternate illustrative modular platen plate that is configured to induce high air flow levels in non-printing regions, and low air flow levels of vacuum in printing regions. 
         FIG. 14  is a plan view of an illustrative platen assembly that includes a plurality of modular platen plates. 
         FIG. 15  is a detailed feed entrance of an illustrative embodiment of a platen assembly that includes a plurality of modular platen plates. 
         FIG. 16  is a schematic view of sequential feeding of substrates on a perforated transfer belt, in which no belt apertures are located within the inter gap region between sequentially transferred workpieces. 
         FIG. 17  is a schematic view of sequential feeding of substrates on a perforated transfer belt, in which some of the belt apertures are partially covered by at least one of the workpieces in the inter gap region between sequentially transferred workpieces. 
         FIG. 18  is a schematic view of sequential feeding of substrates on a perforated transfer belt, in which no belt apertures are partially covered the workpieces in the inter gap region between sequentially transferred workpieces. 
         FIG. 19  is a flow chart for an illustrative method of configuring and operating a printing system that is configured to mitigate ink drop deflection, such as with passive as well as active drop deflection compensation. 
         FIG. 20  is a high-level block diagram showing an example of a processing device that can represent any of the systems described herein. 
     
    
    
     DETAILED DESCRIPTION 
     References in this description to “an embodiment”, “one embodiment”, or the like, mean that the particular feature, function, structure or characteristic being described is included in at least one embodiment of the present invention. Occurrences of such phrases in this specification do not necessarily all refer to the same embodiment. On the other hand, the embodiments referred to also are not necessarily mutually exclusive. 
     Introduced here are techniques that can be used to improve mitigate ink drop deflection in a printing environment that includes an applied vacuum to retain workpieces on a conveyor belt while the workpieces are transferred through a printing region. 
     One or more of the techniques discloses herein can be implemented for a wide variety of vacuum conveyor configurations, and do not limit the working conditions of the vacuum conveyor system. 
       FIG. 1  is a schematic diagram of an illustrative printing system  10  having a printer vacuum table conveyor system  11  for transporting one or more workpieces WP in relation to an array  40  of one or more print bars  42 , e.g.,  42   a - 42   h , wherein each of the print bars  42  includes one or more printheads  45 , and in which the system  10  can be configured to mitigate deflection  112   d  ( FIG. 3 ) of ink drops  102  ( FIG. 3 ). 
       FIG. 3  is a partial cutaway view  100  of an illustrative printing system  10  having a perforated platen  20  and conveyor, i.e., transfer belt  18 , in which applied vacuum  24  near the periphery of a printing region can result in ink drop deflection  112   d . As seen in  FIG. 1  and  FIG. 3 , the perforated platen  20  includes a platen plate  109  having a first surface  27   a  and a second surface  27   b  opposite the first surface  27   a , wherein the platen plate extends from a first end  29   a  to a second end  29   b  opposite the first end  29   a.    
     The illustrative printing system  10  seen in  FIG. 3  includes a vacuum source  25  that is connected though a vacuum conduit  106  to a vacuum manifold  22 , in which a vacuum  24  can be applied to a workpiece WP, such as through platen apertures  110  and belt apertures  108 . As seen in  FIG. 3 , a belt aperture  108  in close proximity  114  to a workpiece WP, but not covered by the workpiece WP, can result in deflection  112   d  of ink drops  102 , which would otherwise be delivered  141  ( FIG. 5 ) through an intended trajectory  112   a  to accurately define an image  104  on the workpiece WP. 
     In an illustrative embodiment, a perforated platen  20  for a printing system  10  can include: a platen plate  109  having a first surface  27   a  and a second surface  27   b  opposite the first surface  27   a , wherein the platen plate  109  extends from a first end  29   a  to a second end  29   b  opposite the first end  29   a , and a first transverse side  250   a  ( FIG. 7 ) and a second transverse side  250   b  ( FIG. 7 ) opposite the first side  250   a ; a plurality of apertures  110  that extend from the first surface  27   a  to the second surface  27   b  of the platen plate  109 , wherein the plurality of apertures  110  are arranged in a plurality of rows  442  ( FIG. 11 ) that extend longitudinally between the first end  29   a  and the second end  29   b ; wherein the first surface  27   a  of the platen plate  109  is configured for supporting a transfer belt  18  that includes a plurality of holes  108  therethrough, as the transfer belt  18  is advanced from the first end  29   a  of the platen plate  109 , through a printing region  406  corresponding to one or more print bars  42 , e.g.,  42   a - 42   h , each including one or more printheads  45 , to the second end  29   b  of the platen plate  109 ; wherein the plurality of apertures  110  are configured to apply a vacuum  24  to the first surface  27   a  of the platen plate  109  from a vacuum source  25  connected  106  ( FIG. 3 ) to the second surface  27   b  of the platen plate  109 ; wherein the plurality of apertures  110  include a group of apertures  110  located substantially below the print bar  42  that are configured to reduce flow induced by the applied vacuum  24  in the printing region  408   p.    
     In some embodiments, an illustrative print bar  42  includes a plurality of printheads  45 , wherein the plurality of apertures  110  below the print bars  42  includes a first group of apertures  110  located below each of the plurality of the printheads  45  that are configured to reduce the induced air flow in the printing region  408   p , and a second group of apertures  110  located in one or more regions  408   n  other than below the printheads  45 , which are configured to constrain a workpiece WP on the transfer belt  18 . In some embodiments, the printheads  45  have a staggered arrangement, wherein the first group of apertures  110  has a staggered arrangement that matches the staggered arrangement of the printheads  45 . In some such embodiments, the staggered arrangement of the apertures  110  that matches the staggered arrangement of the printheads  45  is configured to improve flattening of the workpiece WP, while mitigating deflection  112   d  of ink drops  102  jetted  141  toward the workpiece WP in the printing region  408   p.    
     In some embodiments of the perforated platen  20 , the second group of apertures  110  is configured to constrain a leading edge  67   a  ( FIG. 2 ) of the workpiece WP on the transfer belt as the workpiece WP exits a printing region  408   p . In some embodiments; the second group of apertures  110  is configured to constrain a trailing edge  67   b  ( FIG. 2 ) of the workpiece WP on the transfer belt  18  before the workpiece WP enters a printing region  408   p . In some embodiments, the second group of apertures  110  is configured to constrain a transverse edge  69 , e.g.,  69   a  and/or  69   b  ( FIG. 2 ), of the workpiece WP on the transfer belt  18 . In some embodiments, the applied vacuum  24  is configured to constrain the workpiece WP on the transfer belt  18 , such as by preventing movement of the workpiece WP with respect to the transfer belt  18 , and/or by flattening the workpiece WP against the transfer belt  18 . 
     In some embodiments of the perforated platen  20 , the limits along the travel direction of the envelope of the group of apertures  110  are configured to reduce the flow induced by the applied vacuum  24  are not perpendicular to the travel direction  34 . In some such embodiments, the shape of the limits along the travel direction  34  of the envelope of the group of apertures  110  can be configured to reduce the flow induced by the applied vacuum  24  to mitigate the perturbation or deviation of the transition between low flow regions  408   p  and high flow regions  408   n.    
     In some embodiments of the perforated platen  20 , the platen plate  109  is comprised of a plurality of platen plates  502 , e.g.,  502   a ,  502   b  ( FIGS. 12-15 ). In some embodiments, one or more of the plurality of platen plates  502  are any of movable or replaceable. In some embodiments, at least one of the platen plates  502  is configured to be located between the first end  29   a  of the platen  20  and the printing region  406  ( FIG. 10 ). In some embodiments, at least one of the platen plates  502  is configured to be located between the printing region  406  and the second end  29   b  of the platen  20 . 
     In some embodiments, a printing system  10  for mitigating deflection  112   d  of ink drops  102  in a printing environment includes: a perforated platen  20  having a first surface  27   a  and a second surface  27   b  opposite the first surface  27   a , wherein the perforated platen  20  extends from a first end  29   a  to a second end  29   b  opposite the first end  29   a ; a perforated transfer belt  18  for transporting workpieces WP over the perforated platen  20  from the first end  29   a , through a printing region  406  below at least one print bar  42  that includes one or more printheads  45 , to the second end  29   b ; and a vacuum source  25  connected to the second surface  27   b  of the perforated platen  20 , e.g., such as through a manifold  22 , for applying vacuum  24  through the perforated platen  20  and the perforated transfer belt  18 , to constrain the workpieces WP to the perforated transfer belt  18  as the workpieces WP are transported from the first end  29   b , through the printing region  406 , to the second end  29   b ; wherein the perforated platen  20  is configured to reduce flow induced by the applied vacuum  24  in regions  408   p  directly substantially below the print bar  42  than in regions  408   n  other than the regions  408   p  substantially below the print bar  42 . 
       FIG. 2  is an illustrative view  60  of an illustrative workpiece WP, such as having a characteristic length  64 , width  66 , and thickness  68 , and opposing surfaces  70   a , 70   b . While the illustrative workpiece WP shown in  FIG. 2  is shown as having a characteristic length  64 , such as for printing of separate sequentially transferred workpieces WP through a printing region  103  ( FIG. 3 ), other embodiments of the printer vacuum table systems  11  and printing systems  10  can be used for a workpiece WP that is longer than the vacuum table system  11 , such as for a workpiece WP that is passes into the print region  103  from a transfer roll. The illustrative workpiece WP shown in  FIG. 2  has a leading edge  67   a , a trailing edge  67   b  opposite the leading edge  67   a , and opposing transverse edges  69   a , 69   b.    
     The first surface  70   b  of the illustrative workpiece WP shown in  FIG. 2  can represent a surface  70  upon which graphics  104  ( FIG. 3 ) are to be printed  141  ( FIG. 5 ), while the opposing surface  70   a  can represent a surface  70  that can be constrained by a perforated transfer belt  18  that is configured to transfer the workpiece WP in the print direction  32  through a printing region  406  ( FIG. 10 ). In this manner, vacuum  24  can controllably be applied (e.g.;  FIGS. 1,3 ), such as to compensate for non-planar features  72  of the workpiece WP. 
     Workpieces WP to be printed, such as paper, paperboard, corrugated cardboard, or other media, can often include surfaces  70  that are other than flat, such as including convex or concave features  72 , or other features  72  that are either consistent to the workpieces WP or are specific to one or more specific workpiece items WP. For instance, a workpiece WP may often include convex or concave features  72  across its width  66  or length  64 , such as based on a general characteristic of the workpiece WP, or based on the particular characteristics of one or more separate workpieces WP to be printed. 
     The illustrative printer vacuum table conveyor system  11  seen in  FIG. 1  comprises a transfer belt  18  that extends between a plurality of rollers  16 , e.g.,  16   a ,  16   b , which are rotatably mounted with respect to a chassis  12 . It should be understood that the illustrative printing system  10  seen in  FIG. 1  provides a simplified view of the printing system  10 . For example, the printer vacuum table conveyor system  11  can further comprise one or more additional rollers, such as a tension roller  52  associated with a tension mechanism  132  ( FIG. 4 ), and/or the rollers  16  and transfer belt  18  can further comprise a belt interlock mechanism  156  ( FIG. 5 ), such as but not limited to a plurality of teeth  156  that intermesh. As well, some illustrative embodiment of the enhanced printing system  10  can include additional structures and mechanisms to provide improved dimensional tolerances for any of setup, operation, or longevity. 
     The illustrative printer vacuum table conveyor system  11  seen in  FIG. 1  is typically operated upon by a drive mechanism  26 , which controllably rotates one of the rollers  16 , e.g.,  16   a , thus producing movement  32  of the transfer belt  18 , by which one or more workpieces WP, e.g., boards WP, are controllably moved, such as to be operated upon at one or more locations with respect to the system  10 . While the illustrative printing system  10  is described herein with respect to one or more workpieces WP, e.g., paper board WP, it should be understood that the structures and systems described herein can readily be implemented for a printing system  10  associated with other workpieces or substrates WP, such as but not limited to any of paper, film, cardboard, tile, or other articles of manufacture. 
     The drive mechanism  26  typically comprises a drive motor  242  ( FIG. 7 ) and a coupling mechanism, e.g., a transfer drive  244  ( FIG. 7 ), wherein the drive motor  242  is controllably powered through a controller  21 , e.g., a programmable logic controller (PLC). In some embodiments, the drive mechanism  26  can include one or more enhanced structures, to provide highly accurate and repeatable location and movement. 
     The illustrative print system  10  seen in  FIG. 1  includes an encoder  28 , such as to provide accurate controlled movement  32  of the transfer belt  18  through the drive mechanism  26 . The controller  21  typically comprises one or more processors  23 , e.g.,  23   a - 23   e , and can also comprise storage  25 , e.g., memory, such as for but not limited to storage of any of operating parameters, thresholds, operational history, and/or tracking. In some embodiments, the controller  21  is configured to control all of the movements and operations in the printing system  10 , such as for any of movement of the transfer belt  18  through the drive mechanism  26 , and the coordinated operations of the printheads  45 , which in some embodiments are integrated within print bars  42 , e.g.,  42   a - 42   h , and/or feeding  712  ( FIG. 19 ) of workpieces WP by a feed system  402  ( FIG. 10 ). 
     As also seen in  FIG. 1 , a display  34  and user interface  36  are also typically connected to the controller  21 , such as to provide input from a user USR, e.g., an operator, and/or to provide information to the user USR. As well, the printing system  10  can further comprise a communications link  46 , through which the controller  21  may preferably be configured to transmit an output signal  48  and/or receive an input signal  50 . 
       FIG. 4  is a side view  120  of an illustrative printing system  10  having drop deflection compensation.  FIG. 5  a detailed partial perspective view  140  of an illustrative vacuum conveyor system  11  associated with a printing system  10  having drop deflection compensation. 
     The illustrative printing system  10  seen in  FIG. 4  and  FIG. 5  is configured for printing on workpieces WP, and in some embodiments can include one or more workpiece guides  158 , upstream of one or more of the print bars  42 , such as at the entrance area  146  ( FIG. 5 ) of the transfer belt  18 . Workpieces WP that are placed on the transfer belt  18  may not initially be located with a great degree of accuracy, and/or may be twisted, i.e., rotated. The workpiece guides  158  ensure that workpieces WP are in the proper location on the transfer belt  18 , e.g., in the middle, and that the workpieces WP are acceptably straight, e.g., within an acceptable threshold. 
     The illustrative printer system  10  seen in  FIGS. 4-6  can include an enhanced tension adjustment mechanism  132  for the transfer belt  18 . For example, such as during any of initial setup, belt replacement, or other service, a threaded, i.e., guide screw mechanism  202  ( FIG. 6 ) may be rotatably moved, such as to provide a fine adjustment of linear distance between the rollers  16 , e.g.,  16   a , 16   b , to obtain a desired tension in the transfer belt  18 , such as recommended by the manufacturer of the transfer belt  18 . 
     Similarly, for adjustment of parallelism between the rollers  16 , some embodiments of the tension mechanism  132  can include a pair of guide screws  202 , e.g.,  202   a ,  202   b , on opposing sides of at least one of the rollers  16 , e.g.,  16   a  or  16   b . One or both of the guide screws  202 , e.g.,  202   a  and/or  202   b , may preferably be adjustable, to achieve parallelism between the roller  16  and transfer belt  18 , i.e., to achieve 90 degrees between the axis of the roller  16  and the longitudinal axis of the transfer belt  18 . 
     In some embodiments, a guide screw set  102  associated with a first roller  16 , e.g.,  16   a , may be considered a main or primary guide mechanism  102 , which may be adjustable for parallelism, when the corresponding roller  16  is free for adjustment of any of parallelism or tension, i.e., not locked down, such as when the position of the opposing roller  16 , e.g.,  16   b , is maintained. Similarly, the opposite roller  16 , e.g.,  16   b , may be adjustable for any of parallelism or tension, i.e., not locked down, such as when the position of the opposing roller  16 , e.g.,  16   a , is maintained. The operator USR can then determine when the roller  16  is aligned with the workpiece guide  98 , which assures that the transfer belt  18  is parallel to the opposing roller  16  and properly aligned with the transfer belt  18 . 
     As described below, some embodiments of the printing system  10  include sequential feeding of workpieces WP, which is also synchronized to the perforated transfer belt  18 , such that some embodiments require the relative location of the perforated transfer belt  18  to be known with respect to the workpieces WP. 
     Once the transfer belt  18  is adjusted to be parallel, with adequate tension, the guide screw mechanism  202  is tightened, and the workpiece guide  98  is put back in place. Upon completion, the operator USR may start up the illustrative printing system  10  in a test mode, such as to confirm that the guide is not getting hot, e.g., from excessive friction. If not, the illustrative printing system  10  may be put into or returned to service. If the temperature of the workpiece guide  98  increases excessively during testing, the operator or service personnel USR may repeat one or more of the procedures as necessary, and retest. After setup, the owner or operator USR, does not typically need to reset the tolerance, as the rollers  16  and transfer belt  18  are dimensionally stable, such as for the expected lifetime of the transfer belt  18 . 
     An illustrative printing operation is also seen in the in  FIG. 4 , wherein a print job  126 , such as received from a remote terminal, e.g., an artist or designer, arrives at a main computer  122 , which may be associated with the controller  21 . In some system embodiments, the print job  126  comprises a tagged image file format (TIFF) print job  126 . 
     The main computer  122  then typically produces, i.e., RIPs, a raster image file from the received print file  126 , through which the main computer  122  makes appropriate separations  124 , which are assigned to one or more channels  128 , e.g.,  128   a - 128   h , as necessary to print the image. Each of the channels  128 , e.g.,  128   a - 128   h , are sent to a corresponding slave computer or processor  130 , e.g.,  130   a - 130   h , associated with each print bar  42 , e.g.,  42   a - 42   h , for printing respective colors or other coatings on the workpieces WP. The slave computers or processors  130  can be independent of or integrated with corresponding print bars  42 . The different print bars  42 , e.g.,  42   a - 42   h , are controlled by the respective slave computers  130 , wherein each slave computer  130 , e.g.,  130   a , operates in conjunction with a respective print bar  42 , e.g.,  42   a , i.e., one channel for each slave computer  130 . 
     While the main computer  122  is making the RIP, the printing system  10  is typically configured to work with the graphics that are loaded into the slave computers  130 . When each of the slave computers  130  has the information for their respective print bar  42 , the slave computer  130  connects, e.g., through a high-performance computing (HPC) card, to each of the printheads  45 . In some printing system embodiments  10 , each printhead  45  has a dedicated HPC card, for local processing. 
     The controller  21  may preferably be configured, such as through the programmed processors  23 , e.g.,  23   a - 23   e , to provide integral printer management capabilities, and/or to optimize the printer&#39;s capabilities across its options. The controller  21  and processors  23  may preferably be remotely updatable, such as through the communications link  46 , which enables the worker USR to handle all the elements fast and intuitively. 
     In some embodiments, the printing system  10  can include additional features, such as any of a tone adjustment system (TAS), calculated linearization capabilities, and/or calculate ink consumption capabilities. The tone adjustment system (TAS) may preferably be based on an intuitive interface, such as displayed  36 , which guides the user USR through the process of study and application of changes in tone or intensity, to apply to a model. This feature enables adjustments or variations on existing models in the illustrative printing system  10 , without use of external additional software, or extensive knowledge in color management. 
     In some embodiments, the electronic design of the printing system  10  can be based on the modular distribution of components, thus facilitating future upgrades and allowing full accessibility. In some embodiments, the electronic system of the printing system  10  can deliver high performance, by using the main computer  122  to upload image files, i.e., print jobs  126 , and slave computers  130  that manage the printing of the image files  126 . The result is increased graphical variability and nonstop manufacturing. The enhanced electronics design makes it possible to choose from various printing options, and simultaneously use different printheads  45  in the same printing system  10 , e.g., some for jetting graphic designs, and others to apply any of undercoating, primer, overcoating, or effects. 
       FIG. 5  is a detailed partial perspective view  140  of an illustrative printer vacuum table conveyor system  11  associated with a printing system  10 , wherein the transfer belt  18  moves in a direction of travel  32  with respect to an X axis  142   x , a Y axis  142   y , and a Z axis  142   z . The illustrative print bars  42  seen in  FIG. 5  can be fixedly locked with respect to the chassis  12 . 
       FIG. 6  is a plan view  200  of an illustrative printing system  10 , wherein each of the print bars  42  are in an aligned and locked position  203   a  in relation to the chassis  12 . In some embodiments, the plurality of print bars  42 , e.g.,  42   a - 42   h , comprise separate, i.e., independent, modular print bars  42 .  FIG. 7  is an end view  240  which shows an illustrative conveyor drive mechanism  26 , and also shows one or more printheads  45  within a print bar  42 , such as including a print bar frame  154 . 
     The printing system  10  can be implemented for a wide variety of vacuum conveyor systems  11 , such as for print systems  10  in which vacuum is applied across the entire width  410  ( FIG. 10 ) of the platen  20 , and/or for print systems  10  which include multiple vacuum zones  304 , e.g.,  304   a - 304   g  ( FIG. 8 ). 
     For instance,  FIG. 8  is an end schematic view  300  of a workpiece WP located within a printing region  303  of a printing system  10 , e.g.,  10   b , having a printer conveyor vacuum table system  11  that includes a plurality of vacuum zones  304 , e.g.,  304   a - 304   g , wherein the printing system  10  is configured to hold the workpiece WP with a flatness range  303  that allows high definition printing  141  onto the upper surface  70   b  of the workpiece WP. 
       FIG. 8  is a side schematic view  300  of a workpiece WP located within a printing region  303  of an illustrative printing system  10 , e.g.,  10   b , having a printer vacuum table system  11 , in which the printer vacuum table system  11  is configured to apply vacuum  24  to a workpiece WP from one or more illustrative vacuum zones  304  located below the printer vacuum surface  14 . For instance, the illustrative perforated platen  20  seen in  FIG. 3  can be permeable or can include holes, passages or conduits  110  defined therethrough, to transfer an applied vacuum  24  to a workpiece WP, from one or more of the vacuum zones  304 , in which each of the vacuum zones  304  includes holes, passages or conduits  110  defined therethrough for applying vacuum  24 , such as from the vacuum source  25 . 
     The flatness range  303  of the workpiece WP is accomplished by controlled application of vacuum  24  through one or more vacuum zones  304 , such as vacuum zones  304  that coincide with the workpiece WP to be printed  141 . For instance, the illustrative workpiece WP seen in  FIG. 8  is shown as being center aligned with respect to the width  20  of the printer vacuum surface  14 , such that the workpiece WP is located over some of the plurality of vacuum zones  304 , e.g.,  304   b ,  304   c ,  304   g ,  304   d  and  304   e . As also seen in  FIG. 8 , the center-aligned workpiece WP does not coincide with the peripheral vacuum zones  304   a  and  304   f.    
     The illustrative printing system  10   b  seen in  FIG. 8  includes a printhead assembly  310 , e.g., a print carriage  310 , that includes one or more printheads  45 , e.g.,  45   a - 45   f , for controllable delivery  141  of ink  102 , and a corresponding print system controller  21  and user interface  110  for interaction with a user, i.e., operator USR. The illustrative printhead assembly  310  seen in  FIG. 8  is shown as extending over the width  20  of the printer vacuum surface  14 , and is stationary with respect to the printer vacuum table  12 , for printing on one or more workpieces WP as the workpieces WP are advanced on a perforated transfer belt  18  in the print direction  32 . In some embodiments of the printing system  10 , the printhead assembly or carriage  310  can be moved vertically, e.g.,  142   z  ( FIG. 5 ), such as to compensate for workpieces WP having an increased thickness  68  ( FIG. 2 ). 
     The illustrative print system  10   b  seen in  FIG. 8  includes a vacuum source  25 , e.g., a vacuum blower  25 , which can be controlled either locally, through a local controller  302 , or from the print system controller  21 , to apply vacuum  24  to one or more vacuum zones  304  that are enabled. For instance, vacuum zones  304   b ,  304   c ,  304   d ,  304   e  and  304   g  shown in  FIG. 8  are enabled to apply vacuum  24  through corresponding open valves  306   b ,  306   c ,  306   d ,  306   e  and  306   g , respectively, while vacuum zones  304   a  and  304   f  shown in  FIG. 8  are disabled to prevent the application of vacuum  24  through corresponding closed valves  306   a  and  306   f , respectively, because vacuum zones  304   a  and  304   f  do not coincide with the workpiece WP within the printing region  303 . 
     While the illustrative print system  10   b  seen in  FIG. 8  includes valves  306  to limit flow of vacuum  24  in one or more lateral zones  304 , some embodiments can alternately include limiting plates that extend longitudinally below the perforated platen  20 , such as to reduce or close a passage of the vacuum aspiration  24  on the zones  304  that are not covered by the parts on the platen. For instance, for workpieces WP that sequentially transported on the perforated transfer belt, which do not extend across the width  410  of the platen, the workpieces WP can be center-aligned, right aligned, or left aligned, such as with respect to the transverse axis  142   y  ( FIG. 5 ). As such, one or more zones  304  can be disabled by one or more limiting plates that extend longitudinally below the perforated platen. 
       FIG. 9  is a side schematic view  360  of a workpiece WP located within a jetting region  303  of an illustrative printing system  10  having a printer vacuum table  14 , in which the printer vacuum table  14  is configured to apply vacuum  24  to a workpiece WP through a vacuum manifold  22  located below the printer table surface  20 , in which more air flow  24  is induced in non-printing regions  408   n  ( FIG. 10 ), and less or no air flow  24  is induced in regions  408   p  ( FIG. 10 ) that are substantially aligned with the printheads  45 . 
       FIG. 10  is a simplified plan view  400  of an illustrative perforated platen  20  for a printing system  10 , which is configured to induce high air flow levels in non-printing regions  408   n , and low air flow levels in printing regions  408   p . The illustrative platen  20  seen in  FIG. 10  includes staggered printing regions  408   p , such as corresponding to staggered printheads  45  located above the platen  20 , e.g., four sets of staggered printheads  45  for four color inkjet printing  141  (cyan (C), magenta (M), yellow (Y), and black (K)). Alternate configurations can be used, such as for printing any of one or more process or spot colors, primer or undercoat layers, and/or overcoat layers. In some embodiments, the use of staggered printheads  45  and staggered printing regions  408   p  helps to constrain workpieces WP during the printing process, while mitigating ink drop deflection  112   d . The illustrative platen  20  seen in  FIG. 10  has a characteristic width  410  and length  412 , and can be integrated with a feed system  402 , such that, in operation, workplaces WP in a feed region  404  are sequentially fed onto the transfer belt  18 , though the entry region  146 , the printing region  406 , and the exit region  148 , along a direction of travel  32 . 
     The illustrated perforation patterns  110  seen in  FIG. 11  can thus be configured to correspond to different regions  408  below the printheads  45 , such as to achieve a flow reduction effect in the regions  408 , e.g.,  408   p , where it is necessary to mitigate ink drop deflection  112   d , while the rest of the vacuum table area  408  e.g., regions  408   n , can be freely designed for optimum workpiece substrate WP flattening performance. 
     This flow reduction effect can be detrimental for the flattening performance of the vacuum transport system  11 , particularly in cases where a workpiece substrate WP is severely warped along its transverse edges  69   a , 69   b , and when there are transfer belt holes  108  partially covered by the workpiece substrate WP, such as seen in  FIG. 17 . Under such conditions, maximum air flow  24  may be needed to keep the workpiece substrate WP as flat as possible; hence an air flow reduction may induce a spring-back action of the workpiece substrate WP. 
     The illustrative perforated platen  20  can reconcile these conflicting goals, by introducing perforation patterns  408   p  that are designed for air flow reduction in the same staggered arrangement as the printheads  45 , and preserve the perforation pattern, e.g.,  408   n , of the rest of printer platen  20 , in the space between printheads  45 . This configuration combines low air flow and high air flow regions  408 , in which the low air flow regions  408   p  below the printheads  45  ensure that the ink drops  102  ( FIG. 3 ) are not deflected  112   d , while increased flow of applied vacuum  24  in the high air flow regions  408   n  compensates for the reduced flow of applied vacuum  24  in the other regions  408   p , and thus can keep the workpiece substrate WP flat in unfavorable conditions. 
     In an illustrative embodiment, a conveyor system  11  is configured for transferring substantially planar workpieces WP through a longitudinal path through a printing region  406  located below a print bar  42  that includes one or more printheads  45 , wherein the conveyor system  11  includes: a transfer belt  18  that is configured to travel from a first end  29   a  to a second end  29   b  along the longitudinal path  32 , the transfer belt  18  including a plurality of belt apertures  108  defined therethrough, wherein the belt apertures  108  are arranged as a series of evenly spaced rows  642  ( FIG. 18 ) of belt apertures  108  that extend transversely across the transfer belt  18 , wherein a portion of the belt apertures  108  located under the substantially planar workpieces WP are configured to apply a vacuum  24  to a lower surface  70   a  ( FIG. 2 ) of each of the substantially planar workpieces WP, to constrain the substantially planar workpieces WP to the transfer belt  18  through the printing region  408   p ; and a feed system  402  that is configured to feed the plurality of substantially planar workpieces WP onto the transfer belt  18  in a synchronized manner with respect to the evenly spaced rows  642  of belt apertures  108  that extend transversely across the transfer belt  18 , to ensure that there are no belt apertures  108  that are partially covered by any of a trailing edge  67   b  ( FIGS. 16-18 ) or a leading edge  67   a  ( FIGS. 16-18 ) of any of the substantially planar workpieces WP within a longitudinal gap  602 , e.g.;  602   a - 602   c  ( FIGS. 16-18 ) defined between a trailing edge  67   b  of each of the workpieces WP and a leading edge  67   a  of a sequential one of the workpieces WP. 
     In some embodiments, the prevention of partially covered belt apertures  108  within the longitudinal gap  602  ( FIGS. 16-18 ) between successive substantially planar workpieces WP is configured to reduce deflection  112   d  of ink drops  102  as they are delivered  141  within the printing region  408   p . In some embodiments, the prevention of the belt apertures  108  within the longitudinal gap  602  between successive substantially planar workpieces WP is configured to reduce flow rate requirements of the vacuum system  25  for the printing region  408   p  substantially below the print bar  42 . In some embodiments, the printing system  10  includes a feed system  402  that is configured to feed the workpieces WP onto the perforated transfer belt  18  in a synchronized manner with respect to rows  642  of belt apertures  108  that extend transversely across the transfer belt  18 , to ensure that there are no belt apertures  108  that are partially covered by any of a trailing edge  67   b  or a leading edge  67   a  of any of the workpieces WP within a longitudinal gap  602  defined between a trailing edge  67   b  of each of the workpieces WP and a leading edge  67   a  of a sequential one of the workpieces WP. 
       FIG. 11  is a detailed view  440  of an illustrative perforated platen  20  for a printing system  10 , which is configured to induce high air flow levels  24  through platen apertures  110  in non-printing regions  408   n , and low air flow levels  24  through platen apertures  110  in printing regions  408   p , wherein the platen apertures  110  can be configured in longitudinal rows  442  to generally align with belt apertures  108  defined through a perforated transfer belt  18 . As seen in  FIG. 10 ; any of the location, spacing, i.e., density, and the size, i.e., diameter of the platen apertures  110  can be configured to establish different regions  408  to apply different amounts of vacuum  24 . 
     While some embodiments of the perforated platen  20  can be provided a single perforated sheet, e.g., a single stainless steel or aluminum alloy, other embodiments can be configured using multiple plates  502 , such as seen in  FIGS. 12-14 . 
       FIG. 12  is a plan view  500  of an illustrative modular platen plate  502 , e.g.,  502   a , that is configured to induce high air flow levels  24  in non-printing regions  408   n , and low air flow levels  24  in printing regions  408   p .  FIG. 13  is a plan view  520  of an alternate illustrative platen plate  502 , e.g.,  502   b , that is configured to apply high levels of vacuum in non-printing regions  408   n , and low levels of vacuum  24  in printing regions  408   p . As seen in  FIGS. 12 and 13 , the platen plates  502  have a length  506 , such as generally corresponding to the width  410  ( FIG. 10 ) of an assembled perforated platen  20 . As also seen in  FIGS. 12 and 13 , the platen plates  502  have a transverse width  504 , such that a number of platen plates  502  can be installed, e.g., end-to end, to form the perforated platen  20 . The illustrative platen plate  502   b  seen in  FIG. 13  also includes a non-perforated region  408   b , wherein the plate  502   b  can be used in transition regions, e.g., an entry region  146  and/or an exit region  148 . 
       FIG. 14  is a plan view  540  of an illustrative platen assembly  20  that includes a plurality of modular platen plates  502 , e.g.,  502   a  and  502   b , which can be configured to define a perforated platen  20  that includes any of printing regions  408   p , non-printing regions  408   n , and/or transition regions  408   b  ( FIG. 11 ).  FIG. 15  is a detailed partial lateral view  580  of an illustrative platen assembly  20  having a characteristic width  410 , that includes a plurality of modular platen plates  502 . While the illustrative platen plates  502  can be configured as a series of plates  502  that are longitudinally arranged to make up the perforated platen plate  20 , other embodiments can include modular plates that can be transversely arranged across the width  410  of the platen  20 . 
     Although in the previously presented embodiments, such as shown in  FIG. 12 , the transition between the printing regions  408   p  and the non-printing regions  408   n  is shown as perpendicular to the direction of travel  32 , a transition between these two regions that is not perpendicular to the direction of travel is also considered as a method to mitigate the perturbation between these two regions  408   p ,  408   n.    
     The use of the improved perforated platens  20 , as disclosed herein, can readily be implemented to reduce or eliminate ink drop deflection effects  112   d  ( FIG. 3 ) for a wide variety of vacuum conveyor configurations. As noted above, the phenomenon of drop deflection  112   d  is commonly observed in industrial inkjet printers with vacuum conveyor systems. 
     To mitigate drop deflection effects  112   d  effect on any of the leading edges  67   a  or trailing edges  67   b  of the workpieces WP, e.g., boards, some embodiments of the printing system  10  and associated structures and methods combine a passive system, such as the perforated platen  10  that reduces the air flow  24  in the region below the printheads  45 , and an active system, such as a feed system  402  that distributes the workpieces WP in an optimal way with respect to the transfer belt perforations  108 . 
     The introduction of the perforated platen  20 , despite eliminating the drop deflection issue while keeping the workpiece WP flat, can impact the higher blower pressure necessary to generate enough force  24  in the high air flow regions  408   n  to compensate for the reduced force  24  in the low air flow regions  408   p . In some circumstances, this can result in more severe working conditions of the conveyor system  11  that can be detrimental for the accurate and robust operation of the inkjet printing system  10 . 
       FIG. 16  is a schematic view  600  of sequential feeding of workpiece substrates WP on a perforated transfer belt  18 , in which no belt apertures  108  are located within the inter-copy gap region  602   a  between sequentially transferred workpieces WP, as designated by  604 .  FIG. 17  is a schematic view  620  of sequential feeding of workpiece substrates WP on a perforated transfer belt  18 , in which some of the belt apertures  108  are partially covered by at least one of the workpieces WP in the inter gap region  602   b  between sequentially transferred workpieces, as designated by  624 .  FIG. 18  is a schematic view  640  of sequential feeding of workpiece substrates WP on a perforated transfer belt  18 , in which no belt apertures  108  are partially covered the workpieces WP in the inter-copy gap region  602   c  between sequentially transferred workpieces WP, as designated by  644 . 
     The excess flow requirements through the perforated platen  20  and the perforated transfer belt  18  can this be reduced or eliminated, by ensuring that there are not belt holes  108  partially covered by the workpiece substrates WP. In some embodiments, this is accomplished with a synchronized feeder  402 , that feeds workpiece substrates WP to ensure that there are not belt holes  108  that are partially covered by the workpiece substrates WP. In this case, the flow rate requirements in the region  408   p  below the printheads  45  are eliminated, because the belt holes  108  can be fully sealed by the substrate WP, so the holding force generated by these perforations  108  is independent of the flow through them. Contrary to the illustrative configuration seen in  FIG. 17 , this approach, such as seen in  FIG. 18 , does not ensure that there are not open holes  108  in the inter-copy gap  602   c  between substrates WP for certain combinations of gap between substrates WP, substrate length  64  and distance between belt holes  108  along the travel direction  32 , but ensures that there are not partially covered belt holes  108 . This approach can be achieved for any combination of substrate WP and process parameters. The difference between the different strategies is schematically shown in  FIGS. 16-18 . 
     The combination of the passive and active embodiments allows the printing system  10  to achieve a universal drop-deflection compensation solution. While the passive features, i.e., the perforated platen  20 , can reduce the air flow  24  through the belt holes  108  that can be present in the gap  602  between substrates WP, active techniques, e.g.,  710  ( FIG. 19 ) can minimize the impact of the perforated platen  20  on the requirements on the vacuum system components  25 . 
       FIG. 19  is a flow chart for an illustrative method  700  of configuring and operating a printing system  10  that is configured to mitigate ink drop deflection  112   d , such as with passive as well as active drop deflection compensation. For instance, during setup  702  of the printing system  10 , a perforated platen  20  is configured to apply different levels of vacuum  24  for printing areas  408   p  and non-printing areas  408   n , and a perforated transfer belt  18  is provided for transporting workpieces WP on the perforated platen  20 , through a printing region  406  having one or more printheads  45 . In operation, specific operating parameters are set  708  for a specific print job  126  ( FIG. 4 ), such as based on any of printing parameters, substrate alignment, vacuum zone shut off, substrate type, or substrate planarity. In some embodiments, the feed system  402  can be set for any of inter-copy gap  602  and belt apertures  108  located within the inter-copy gap  602 . Once the operating parameters are set, the print job can be run, by sequentially feeding the workpieces WP through the active printing system  10 . 
     An illustrative method  700  for mitigating ink drop deflection  112   d  in a printing system  10  can include configuring  704  a perforated platen  20  to apply a lower induced air flow level of vacuum  24  in a printing region  408   p  proximate to a printhead  45  than the induced air flow level of vacuum  24  to a region  408   n  other than the printing region  408   p ; configuring  706  a perforated transfer belt  18  for transporting workpieces WP over the perforated platen  20 ; setting operating parameters  708  for a print job; sequentially feeding  712  the workpieces WP onto the transfer belt  18  while applying vacuum  24  through the perforated platen  20  and the perforated transfer belt  18  to constrain the workpieces WP; and jetting ink  102  onto the workpieces WP based on the print job; wherein the printing system  10  mitigates ink drop deflection  112   d . In some embodiments, wherein the perforated transfer belt  18  includes a plurality or belt apertures  108  extending therethrough, the workpieces WP are sequentially fed  112  onto the transfer belt  18  such that there are no belt apertures  108  that are partially covered by the workpieces WP. 
     The disclosed printing systems, structures and methods can be implemented for a wide variety of inkjet industrial printers, and makes possible the flattening, conveying and printing of highly deformed and stiff substrates WP, without significant degradation of the printing quality. 
     The description herein provides certain specific details for a thorough understanding and enabling description of these examples. One skilled in the relevant technology will understand, however, that some of the disclosed embodiments may be practiced without many of these details. 
     Likewise, one skilled in the relevant technology will also understand that some of the embodiments may include many other obvious features not described in detail herein. Additionally, some well-known structures or functions may not be shown or described in detail herein, to avoid unnecessarily obscuring the relevant descriptions of the various illustrative examples. 
     The terminology used herein is to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the embodiments. Indeed, certain terms may even be emphasized herein. However, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such. 
       FIG. 20  is a high-level block diagram showing an example of a processing device  1000  that can be a part of any of the systems described above, such as the print system controller  21 , or local controllers  23 , 302 . Any of these systems may be or include two or more processing devices such as represented in  FIG. 20 , which may be coupled to each other via a network or multiple networks. In some embodiments, the illustrative processing device  1000  seen in  FIG. 20  can be embodied as a machine in the example form of a computer system within which a set of instructions for causing the machine to perform one or more of the methodologies discussed herein may be executed. 
     In the illustrated embodiment, the processing system  1000  includes one or more processors  1005 , memory  1010 , a communication device and/or network adapter  630 , and one or more storage devices  1020  and/or input/output (I/O) devices  1025 , all coupled to each other through an interconnect  1015 . The interconnect  1015  may be or include one or more conductive traces, buses, point-to-point connections, controllers, adapters and/or other conventional connection devices. The processor(s)  1005  may be or include, for example, one or more general-purpose programmable microprocessors, microcontrollers, application specific integrated circuits (ASICs), programmable gate arrays, or the like, or a combination of such devices. The processor(s)  1005  control the overall operation of the processing device  1000 . Memory  1010  and/or  1020  may be or include one or more physical storage devices, which may be in the form of random access memory (RAM), read-only memory (ROM) (which may be erasable and programmable), flash memory, miniature hard disk drive, or other suitable type of storage device, or a combination of such devices. Memory  1010  and/or  1020  may store data and instructions that configure the processor(s)  1005  to execute operations in accordance with the techniques described above. The communication device  1030  may be or include, for example, an Ethernet adapter, cable modem, Wi-Fi adapter; cellular transceiver, Bluetooth transceiver, or the like, or a combination thereof. Depending on the specific nature and purpose of the processing device  1000 , the I/O devices  1025  can include devices such as a display (which may be a touch screen display), audio speaker, keyboard, mouse or other pointing device, microphone, camera, etc. 
     While the printing system  10  can readily be implemented for a wide variety of inkjet industrial printers  10 , it should readily be understood that the vacuum conveyor system  11  also be configured for other ink and fluid delivery systems. 
     Unless contrary to physical possibility, it is envisioned that (i) the methods/steps described above may be performed in any sequence and/or in any combination, and that (ii) the components of respective embodiments may be combined in any manner. 
     Many of the ink delivery system and printer system techniques introduced above can be implemented by programmable circuitry programmed/configured by software and/or firmware, or entirely by special-purpose circuitry, or by a combination of such forms. Such special-purpose circuitry (if any) can be in the form of, for example, one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc. 
     Software or firmware to implement the techniques introduced here may be stored on a machine-readable storage medium and may be executed by one or more general-purpose or special-purpose programmable microprocessors. A “machine-readable medium”, as the term is used herein, includes any mechanism that can store information in a form accessible by a machine (a machine may be, for example, a computer, network device, cellular phone, personal digital assistant (PDA), manufacturing tool, or any device with one or more processors, etc.). For example, a machine-accessible medium includes recordable/non-recordable media, e.g., read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; etc. 
     Those skilled in the art will appreciate that actual data structures used to store this information may differ from the figures and/or tables shown, in that they, for example, may be organized in a different manner; may contain more or less information than shown; may be compressed, scrambled and/or encrypted; etc. 
     Note that any and all of the embodiments described above can be combined with each other, except to the extent that it may be stated otherwise above or to the extent that any such embodiments might be mutually exclusive in function and/or structure. 
     Although the present invention has been described with reference to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.