Print production processes implement both sheetfed and web offset lithography devices such as printing presses that print, respectively, onto individual sheets and large rolls of paper. In either case, these print production processes typically employ one or more post-print finishing devices that perform additional finishing operations on printed material after printing has been completed. A finishing operation generally includes any post-printing process, such as slitting, trimming, die-cutting, folding, coating, embossing, and binding. Finishing operations can be performed by one or more finishing devices that are in-line or near-line with the printing device.
With in-line printing processes, finishing devices are connected directly to a single printing device so that printed material passes directly from the printer to the one or more in-line finishing devices without being removed from the process and taken to other devices. With near-line printing processes, finishing devices are not connected directly to a particular printing device, so printed material (e.g., stacks of printed sheet paper) needs to be demounted from the printing device and remounted on the one or more near-line finishing devices. While the need to transfer printed material to near-line finishing devices seems disadvantageous, it has the advantage of allowing near-line finishing devices to process printed material from more than one printing device. In general, advantages and disadvantages between the use of in-line or near-line finishing devices depend on factors such as printing speeds, finishing device processing speeds, printer down-time, and so on.
One challenge that persists with regard to sheetfed print production processes is achieving an accurate alignment of the sheet paper between the printing device and the finishing device. Paper sheets are cut to standard sizes, such as “A”, “B”, and “C” series paper sizes, and various standards specify tolerances for the different sized sheets. For example, the tolerance for a “B2” sheet size is ±2-3 mm under the international paper size standard, ISO. When changing between different printing modes (e.g., simplex and duplex), the printing device and finishing device can align the sheet of paper to opposite edges. Is such cases, the paper tolerance can create alignment inaccuracies with in-line finishing processes.
The present embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.
As alluded to above, the manner in which paper sheets are aligned within printing and finishing devices can change for different printing modes (i.e., simplex and duplex modes). Due to tolerances in standard cut paper sizes, this can create misalignments in the finishing processes that can result in misplaced and/or deficient finishing effects. For example, finishing effects such as paper slits, trims, die-cuts, folds, and so on, that are added to the paper sheets by the finishing device, can be aligned incorrectly with respect to printed matter (e.g., text, graphics, etc.) that has been previously applied to the paper sheets by the printing device.
In the simplex printing mode, the printing device prints on one side of the paper sheet, and the sheet is aligned in both the printing device and the finishing device to the leading edge of the sheet (i.e., the same edge of the sheet). Because the finishing device and printing device align the sheet to the same edge in simplex mode, the paper tolerance overhang, or residue, at the trailing edge of the sheet does not create an alignment issue between the printed output and the finishing effect.
However, in duplex printing mode, the printing device prints on both sides of the paper sheet. Duplex printing entails flipping the paper sheet over within the printing device. Nevertheless, the paper sheet is still aligned to the leading edge of the page within the printer, and both sides of the sheet are printed according to the leading edge alignment. In the finishing device, however, because the paper sheet has been flipped over within the printing device, the sheet aligns to the trailing edge instead of the leading edge. This occurs primarily when the printing and finishing devices are configured in an in-line printing process where the paper sheets move directly from the printing device to the connected finishing device. It can also occur in a near-line printing process where the printed sheets are manually transferred from the printer to the finishing device (e.g., on a pallet). When the printing device and finishing device align the paper sheets to opposite edges (i.e., leading edge vs. trailing edge), the finishing effect applied by the finishing device can be misaligned with respect to the printed output on the paper sheet by an amount that corresponds to the tolerance overhang, or residue, that exists at the trailing edge of the sheet.
Embodiments of the present disclosure help to remedy the misalignment of sheetfed pages between printing and finishing devices, generally through a decision algorithm that determines when to execute a fine-tune, alignment correction cycle within the finishing device. A printing device employs cameras during printing to measure the lengths of paper sheets that are of the same standard dimension. In one implementation, the printing device forwards camera-measured sheet length data, on-the-fly, to an in-line finishing device that executes an algorithm to determine if an alignment correction cycle should be run. Sheet length data is gathered in this manner and stored for each paper sheet as it passes through the printing device. As sheet length data is received from the printing device, the algorithm performs a difference calculation to calculate the difference between the last two sheets. When the difference in length between two consecutive sheets exceeds a two-sheet threshold, the algorithm initiates an alignment correction cycle on the finishing device. The alignment correction cycle aligns the second sheet so that the finishing effect is applied at the correct location on the sheet. When the difference in length between two consecutive sheets does not exceed the two-sheet threshold, the algorithm determines if the total number of sheets (i.e., a sheet count (SC)) exceeds a sheet-count threshold (SCT). If the sheet-count threshold has been exceeded, the algorithm determines if the average length of the previous SCT number of sheets exceeds a trend threshold. When the average length of the previous SCT number of sheets exceeds the trend threshold, the algorithm initiates the alignment correction cycle on the finishing device.
In an example implementation, a processor-readable medium stores code representing instructions that when executed by a processor cause the processor to receive sheet length data for two paper sheets of a same standard dimension passing consecutively through a printing device. The code further causes the processor to calculate a length difference between the two paper sheets, and when the length difference exceeds a two-sheet threshold, initiate an alignment correction cycle in a paper finishing device.
In another example implementation, a processor-readable medium stores code representing instructions that when executed by a processor cause the processor to receive a matching list that includes measured sheet lengths matched to specific paper sheets from a printed media stack. The processor runs a first and second paper sheet from the printed media stack through a finishing device and compares measured sheet lengths from the list for the first and second paper sheets. The processor initiates a correction cycle on the second paper sheet when a difference in measured sheet lengths between the first and second paper sheets exceeds a two-sheet threshold.
In another example implementation, a processor-readable medium stores code representing instructions that when executed by a processor cause the processor to receive and store a prior sheet length, receive and store a next sheet length, increment a sheet count (SC) for each sheet length received, and calculate a length difference between the prior and next sheet lengths. When the length difference exceeds a two-sheet threshold as determined by the processor, the processor causes the execution of an alignment correction cycle. When the length difference does not exceed the two-sheet threshold, the processor determines if the SC exceeds a sheet count threshold (SCT). When the SC exceeds the SCT, the processor calculates an average sheet length of the most recent sheets numbering up to the SCT. When the average sheet length exceeds a trend threshold, the processor causes the execution of the alignment correction cycle.
As shown in
In an example electrophotographic print process, a charge mechanism applies an electrostatic charge to a photo imaging member, such as a photoconductor drum. As the photoconductor drum rotates, a laser assembly writes a latent image onto the drum with a laser that discharges electrostatic charge from appropriate portions of the drum. A toner supply guides toner to a developer roller, and as the developer roller and photoconductor drum rotate, toner is developed to the latent image on the photoconductor drum. Different color components of an image can also be developed onto the photoconductor drum in this manner. Each color can be developed onto the photoconductor drum and transferred one color at a time to an image transfer element (e.g., a transfer blanket). The full image is then transferred or “offset” from the blanket to the paper sheet 111 (or other print media 111) and fused in a fuser assembly before the sheet 111 exits the print engine 106. The movement and alignment of paper sheets 111 through the print engine 106 is managed by various media alignment and advancement mechanisms 112a. Media alignment and advancement mechanisms 112a can include, for example, guide rollers, alignment bars, moving platforms, and so on.
In another example, print engine 106 comprises components of an inkjet printer that operate to apply liquid ink to a print medium 111 (e.g., paper sheet 111) through an ink jetting process. An inkjet-based print engine 106 generally includes multiple printheads integrated onto one or more printbars, several fluid supplies that supply liquid bonding agents and different colored inks to the printheads, a printhead service station to maintain the printheads, and a dryer that provides warm air to dry the paper sheet 111 (or other print media 111) after application of the liquid ink. During operation, as the media alignment and advancement mechanism 112a transports paper sheets 111 past the printbar, printhead nozzles are activated by signals from controller 110a to eject droplets of ink onto the sheets 111. Printhead nozzles are typically arranged in one or more columns or arrays so that properly sequenced ejection of ink from the nozzles causes characters, symbols, and/or other graphics or images to be printed on the print media 111 as it moves past the printbar.
Referring still to
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Referring again to printing device 102 and finishing device 104, the electronic controllers 110a and 110b generally include, respectively, processors (CPU) 116a and 116b, and memories 118a and 118b. In addition to processor 116a and memory 118a, controller 110a may also include firmware and other electronics for communicating with and controlling print engine 106, cameras 108, and media alignment and advancement mechanisms 112a. Memory 118 (118a, 118b) can include both volatile (i.e., RAM) and nonvolatile (e.g., ROM, hard disk, floppy disk, CD-ROM, etc.) memory components comprising non-transitory computer/processor-readable media that provide for the storage of computer/processor-readable coded instructions, data structures, program modules, JDF, and other data. For example, electronic controller 110a receives print data 120 from a host system, such as a computer, and stores the data 120 in memory 118a. Data 120 represents, for example, a document or image file to be printed. As such, data 120 forms a print job for printing device 102 that includes one or more print job commands and/or command parameters. Using data 120, electronic controller 110a controls print engine 106 to form characters, symbols, and/or other graphics or images on paper sheets 111.
In one implementation, electronic controller 110a includes a correction cycle decision algorithm 122a and sheet length data 124 stored in memory 118a. Correction cycle decision algorithm 122a comprises instructions executable on processor 116a to control components of printing device 102 for generating sheet length data 124 while paper sheets 111 pass through print engine 106. More specifically, decision algorithm 122a executes on processor 116a to control cameras 108 to capture images of each paper sheet 111 while the print engine 106 prints on the sheet 111. Decision algorithm 122a uses the images to measure, or calculate, the length of each sheet 111. While the paper sheets 111 being imaged and measured are of the same standard size (e.g., size B2), each standard sheet size has a tolerance within which the length of the sheet can vary. For example, the tolerance for a B2 sheet size is ±2-3 mm. Decision algorithm 122a accurately measures the actual length of each paper sheet 111 so that differences in sheet lengths can be determined, as discussed here below.
In one implementation, the measured sheet lengths are stored as sheet length data 124 on printing device 102 and used on-the-fly (i.e., as each sheet 111 is measured) by decision algorithm 122a to determine when to send a correction cycle initiation command 126 to the finishing device 104. Thus, as a printed sheet 111 transfers directly from the printing device 102 to the finishing device 104, the corresponding sheet length data 124 is used in real time to determine whether a correction cycle 128 is appropriate for that same sheet. In this implementation, the decision to initiate (i.e., execute) a correction cycle 128 on the finishing device 104 is made by the decision algorithm 122a executing on the printing device 102. In other implementations, however, the decision to initiate a correction cycle 128 on the finishing device 104 is made by the decision algorithm 122b executing on the finishing device 104. The specific steps performed by algorithms 122a and 122b to determine when to initiate a correction cycle are discussed in detail herein below.
As just noted, in another implementation, decision algorithm 122b executing on finishing device 104 determines when to initiate a correction cycle 128. Accordingly, memory 118b on electronic controller 110b includes decision algorithm 122b executable on processor 116b. In this implementation, decision algorithm 122a on printing device 102 executes to capture images of each paper sheet 111 with cameras 108, and sends measured sheet length data 124 on-the-fly (i.e., as each sheet 111 is measured) to the finishing device 104. Decision algorithm 122b executes on finishing device 104 to receive the sheet length data 124, and uses the data 124 to determine in real-time when to send a correction cycle command 126, initiating a correction cycle 128. Thus, in one implementation, decision algorithm 122a on printing device 102 generates and analyzes sheet length data 124, and determines when to initiate a correction cycle 128. In another implementation, decision algorithm 122a on printing device 102 generates the sheet length data 124 and sends it to the finishing device 104, where decision algorithm 122b analyzes the data 124 and determines when to initiate a correction cycle 128.
A correction cycle 128 is executable on processor 116b to control a fine-tune setup of the media alignment mechanisms 112b on finishing device 104. For example, a correction cycle 128 can include adjusting the positions of media alignment bars within the finishing device 104 to ensure that the finishing mechanism 114 properly positions a finishing effect (e.g., a paper slit) on the paper sheet 111. A correction cycle 128 can also adjust the positions of the finishing mechanisms 114 to ensure that the finishing effect is properly positioned on the paper sheet 111. For example, a correction cycle 128 can adjust the positions of slitters, or knives, with respect to the paper sheet 111 such that the finishing effect (i.e., the paper cut) is properly located on the sheet 111. A correction cycle 128 can also implement a combination of adjustments to both the alignment mechanisms 112b and the finishing mechanisms 114.
The specific steps performed by decision algorithms 122a and 122b to determine when to initiate a correction cycle 128, are the same for both algorithms. That is, algorithms 122a and 122b are the same with respect to determining when to initiate a correction cycle 128. Algorithms 122a and 122b differ in that 122a gathers paper sheet images and generates the sheet length data 124. In this respect, therefore, decision algorithms 122a and 122b can be collectively referred to as decision algorithm 122.
Decision algorithm 122 selectively determines when to initiate an alignment correction cycle 128 on finishing device 104 based on two different types of calculations. A first calculation finds the difference in length between two consecutively printed sheets 111, and the algorithm 122 compares the difference to a “two-sheet threshold” to determine whether to initiate a correction cycle 128. A second calculation finds an average length of a number of most recently printed sheets 111, and the algorithm 122 compares the average to a “trend threshold” to determine whether to initiate a correction cycle 128.
At decision block 206, the absolute difference between the LNS and LPS is calculated and compared to a two-sheet threshold (TST). Thus, the length of two consecutively printed sheets is being compared. If the difference is greater than the TST, the algorithm 122 initiates a correction cycle 128 on the finishing device 104. The algorithm 122 then makes the LNS into the LPS at block 210 (i.e., it sets LNS=LPS), and returns to block 204 to receive and store a new LNS, and to increment SC. If, however, the difference at decision block 206 is not greater than the TST, the algorithm 122 determines if the sheet count, SC, exceeds a sheet count threshold (SCT), as shown at decision block 212. If the SCT has not been exceeded, the algorithm 122 again makes the LNS into the LPS at block 210 (i.e., it sets LNS=LPS), and returns to block 204 to receive and store a new LNS, and to increment SC.
If the SCT has been exceeded, however, the algorithm 122 calculates the average length of the most recent SCT number of sheets (i.e., the AVGSCT) and determines if the AVGSCT is greater than a trend threshold (TT), as shown at decision block 214. Thus, the slope of the lengths of the most recent SCT number of sheets is compared to a trend threshold to see if the sheet lengths are trending up or down above a certain threshold amount. If the AVGSCT is not greater than the TT, then the algorithm 122 again makes the LNS into the LPS at block 210 (i.e., it sets LNS=LPS), and returns to block 204 to receive and store a new LNS, and to increment SC. If the AVGSCT is greater than the TT, however, the algorithm 122 initiates a correction cycle 128 on the finishing device 104. The algorithm 122 then makes the LNS into the LPS at block 210 (i.e., it sets LNS=LPS), and returns to block 204 to receive and store a new LNS, and to increment SC. It is worth noting that in other implementations, at block 214, the algorithm can calculate the average length of a different number of sheets other that the most recent SCT number of sheets.
In addition, because there is not a direct physical connection between the printing and finishing devices, there is usually not a hard-wire connection between the devices that would enable direct, on-the-fly, data transfers as in the in-line system 100 discussed above. However, as shown in
While algorithms 122 function in generally the same manner as discussed above regarding
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This is a continuation of U.S. application Ser. No. 13/906,647, filed May 31, 2013, which is hereby incorporated by reference.
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20150130128 A1 | May 2015 | US |
Number | Date | Country | |
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Parent | 13906647 | May 2013 | US |
Child | 14605563 | US |