JP2012198294A - Image forming system and post-processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently fold a plurality of sheets with high quality.SOLUTION: The image forming system includes: a folding mechanism that forms a middle folding line on a sheet discharged from an image forming device; a normal conveyance mechanism for conveying the sheet with the middle folding line to a post-processing part; a reversal conveyance mechanism for turning over the sheet with the middle folding line to the folding mechanism again; an image formation control part for setting an image formation order for each page according to a predetermined number of times that the sheets to be used for image formation are folded in the middle when images for a plurality of pages are formed; an image forming part for forming images for a plurality of pages in the set image formation order; a paper discharge mechanism for discharging the sheets used for forming the images for a plurality of pages to a post-processing device; and a conveyance control part for controlling the normal conveyance mechanism and the reversal conveyance mechanism so as to fold the sheets discharged from the image forming device, in the middle for the above number of times and to convey them to the post-processing part.

Description

  The present invention relates to a post-processing apparatus that processes a sheet on which an image is formed, and an image forming system having the post-processing apparatus.

  2. Description of the Related Art An image forming system having an image forming apparatus such as an MFP (Multi Function Peripheral) or an on-demand printer and one or more post-processing apparatuses (finishers) connected to the image forming apparatus has been put into practical use. The post-processing apparatus performs one or more of various post-processing (processing) such as punching, stapling, folding, gluing bookbinding, and cutting. The image forming system includes an image forming apparatus and a post-processing apparatus having functions according to the application. For example, an image forming system used for creating a booklet includes an image forming apparatus having a booklet mode for forming a total of four pages on the front and back of a printing sheet (hereinafter referred to as paper), and two sheets of paper. And a post-processing device capable of “saddle folding” and “saddle stitching” for stapling a bundle of sheets at the fold position. In some cases, a post-processing device capable of half-folding and a post-processing device capable of saddle stitching are used in combination.

  With respect to the middle folding, in Patent Document 1, when a plurality of sheets are stacked and folded together in a bundle of sheets, in order to obtain a good folding state, folding that pushes the position of the sheet fold from one direction is performed. It has been proposed to perform the operation once when the number is small and twice when the number is large. Patent Document 2 proposes controlling the number of folding operations in accordance with the direction of the sheet gap that affects the foldability. Further, Patent Document 3 discloses a saddle stitcher that folds sheets one by one or a small number of sheets prior to center folding in a bundle of sheets. There is a description in the same document that a high-quality booklet with less bulging of the fold portion can be created by two-stage middle folding.

  On the other hand, as a function of a digital image forming apparatus, a function of forming an image of each page in an order other than the page number order when printing a document of a plurality of pages is known. For example, in the above-described booklet mode, two pages having consecutive page numbers are printed in the order of being divided into a front side and a back side of one sheet. Japanese Patent Application Laid-Open No. 2004-228561 proposes a change in order in which a monochrome page is continuously formed after a color page is continuously formed when color pages and monochrome pages are mixed.

JP-A-9-183567 JP 2008-174383 A JP 2010-70292 A JP 2008-292644 A

  The paper type affects the quality of the folded paper. In general, a paper with a large basis weight is difficult to make a sharp crease, and when folded, the vicinity of the crease on the paper surface is curved in the thickness direction. The swelling of the thickness due to the curvature reduces the number of sheets that can be accommodated (stackability) in a space with a limited size for accommodating paper. If the predetermined number of sheets cannot be discharged into the storage space or overflows from the storage space, the post-processing is interrupted.

  With the technique of repeating the same folding process on a sheet bundle as in the prior arts of Patent Documents 1 and 2, it is difficult to sufficiently reduce the swelling of the thickness near the fold. In addition, when forming an image using a plurality of papers of different paper types, the number of folding processes is set according to the paper type that is most difficult to crease in the paper bundle, and many easy-to-fold papers are folded unnecessarily. It will be.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming system capable of efficiently performing high-quality folding processing on a plurality of sheets.

  An image forming system that achieves the above object includes an image forming apparatus and a post-processing apparatus. The post-processing device includes a folding mechanism that folds the sheet discharged from the image forming apparatus, a normal conveyance mechanism that conveys the sheet that has been folded by the fold mechanism, to a post-processing unit, and the folding mechanism. And a reversing and conveying mechanism for reversing the front and back of the sheet with the middle crease and conveying it again to the folding mechanism. When the image forming apparatus forms an image for a plurality of pages, the image forming order in units of pages is set to the number of times the middle folding process by the folding mechanism determined for the paper used for the image forming should be performed. An image forming control unit that is set according to the image forming unit, an image forming unit that forms an image for the plurality of pages in the image forming order set by the image forming control unit, and an image forming unit that forms the image for the plurality of pages. A paper discharge mechanism for discharging the used paper to the post-processing device. Either the image forming apparatus or the post-processing apparatus performs the normal folding mechanism on the paper ejected from the image forming apparatus and transports it to the post-processing unit so as to perform the half-folding process. A transport control unit that controls the reverse transport mechanism is provided.

  According to the present invention, high-quality regardless of the paper type without wasteful folding, by switching whether to perform both valley folding and mountain folding or only one side of the paper according to the paper type. The folding processing result can be obtained. In addition, the folding process for a plurality of sheets can be speeded up by changing the order of image formation.

1 is a diagram illustrating a configuration of a post-processing device included in an image forming system according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating components related to folding processing in the image forming system. It is a figure which shows the point of the paper conveyance in the case of performing both a valley fold and a mountain fold about one paper surface. It is a figure which shows the point of the paper conveyance in the case of performing only a valley fold about one paper surface. FIG. 10 is a diagram illustrating an example of a relationship between two conveyance modes in the post-processing apparatus and an image forming order in the image forming apparatus. FIG. 6 is an explanatory diagram illustrating simplification of a sheet transport mechanism by changing an image forming order. It is a figure which shows an example of the operation screen for operation which designates the paper type of a paper. 6 is a diagram illustrating folding number information stored in the image forming apparatus. FIG. It is a figure which shows the flow of the conveyance setting process performed in response to operation which designates a paper type.

  An image forming system 1 illustrated in FIG. 1 includes an image forming apparatus 2 and a post-processing apparatus 3. The image forming apparatus 2 is an information device called an MFP (Multifunction Peripheral) or a multifunction device having various uses including copying and network printing. The image forming apparatus 1 includes a tandem printer engine 24 that forms a color or monochrome image by electrophotography. The post-processing device 3 is a finisher that can be connected to the image forming device 2 and has the following mechanism for creating a booklet.

  The post-processing device 3 connected to the image forming apparatus 2 receives the paper P on which an image is discharged from the image forming apparatus 2. The paper P is carried into the folding mechanism 32 on the conveyance path R1 by the conveyance roller pair 41. The folding mechanism 32 includes a roller pair 321 that sandwiches the paper P and a chopper unit 322 that projects a thin plate toward the nip of the roller pair 321, and folds the paper P perpendicular to the transport direction. At this time, the operation timing is set so that the fold line is a middle fold line located in the center of the sheet P in the transport direction. The folding mechanism 32 does not fold the paper P in half, sandwiches the paper P to such an extent that the middle crease is attached, and then reverses the rotation of the roller pair 321 to return the paper P to a nearly flat state at an appropriate time. When attention is paid to the upper surface of the paper P in the figure, the folding method by the folding mechanism 32 is valley folding. Depending on the state of the guide claw 44 in the vicinity of the conveyance roller pair 42, the sheet P with the middle crease is conveyed through the conveyance path R1 to the subsequent processing unit 38, or indicated by a thick broken line arrow in the drawing. It is once carried into the switchback path R2a which is a part of the reverse conveyance path R2. The reverse conveyance path R2 is a characteristic element of the post-processing device 3, and the sheet P is subjected to both front and back folding processing (each surface undergoes valley folding and mountain folding) by a single folding mechanism 32. It is provided for. The folding process for the front and back sides will be described later.

  The paper P transported to the subsequent processing unit 38 through the transport path R1 is stored in the temporary storage space S1 for stacking the paper, and at that time, positioned by the stopper 55 in the transport direction. In the temporary storage space S1, a plurality of sheets (including the sheet P) constituting the booklet are stored in the order of conveyance. In the figure, a sheet bundle PG in which a plurality of sheets are overlapped is drawn. The post-processing unit 38 includes an alignment mechanism (not shown) that aligns the edges in the crease direction of the sheet bundle PG, a staple mechanism 52 for saddle-stitching the aligned sheet bundle PG, and a folding mechanism 54 for folding the sheet bundle PG. Have. The booklet PGb created by the stapling mechanism 52 and the folding mechanism 54 is discharged to a booklet receiving tray 58. When the user designates an operation that does not require half-folding, the paper P is discharged to the paper discharge tray 59.

  FIG. 2 shows components related to folding processing in the image forming system 1.

  The image forming apparatus 2 includes a main controller 21 that controls the image forming system 1 and a printer controller 27 that controls the image forming operation. The main controller 21 performs predetermined control in response to a user instruction from the operation panel 20 and an operation request from an external device that communicates via the communication interface 28. The main controller 21 includes a central processing unit (CPU) as a computer that executes a control program and various applications, a read only memory (ROM) that stores the control program, and a random access memory (RAM) that is a work area for executing the program. Have. In a print job using the printer engine 24 among various jobs given to the image forming apparatus 1 which is an MFP, the main controller 21 controls the printer engine 24 and print data suitable for the printer engine 24. Instruct the generation of. As a print job, the contents to be printed are stored in a network printing job described in a page description language (PDL), a copy job using the image scanner 22, and a hard disk drive which is a built-in storage 29. There is a job to print a document.

  The printer controller 27 controls the printer engine 24, the paper feed mechanism 25, and the paper discharge mechanism 26 in accordance with a given print job. Further, the printer controller 27 implements post-processing designated in the print job in cooperation with the finisher controller 30 provided in the post-processing device 3. The paper feed mechanism 25 includes a paper stacker (not shown) that is a paper supply source of a predetermined paper type and a manual paper feed tray, and feeds designated paper from the supply source to the printer engine 24 that is an image forming unit. The paper discharge mechanism 26 discharges the paper on which the image has been formed by the printer engine 24 to the post-processing device 3.

  When a print job requesting image formation of a plurality of pages is given, it is determined which pages are formed on the front surface (first surface) and the back surface (second surface) of a single sheet or a plurality of sheets used for image formation. An image forming order is set for each page. In the present embodiment, the printer controller 27 has a function as an image formation control unit for performing this setting. In general, the image formation order in single-sided printing at the same magnification is the order of page numbers (the order of arrangement of pages of original image data). However, in double-sided printing, images are not always formed in the order of page numbers even at the same magnification. Depending on the configuration of the reversal paper feed mechanism and the relationship between the conveyance path length and the paper size, there is a case where the printing on the one side of a plurality of papers is continuously performed and then the remaining one side is printed for speeding up. However, in this case, when the sheets discharged in order are viewed, the page order is the order of page numbers for two pages.

  The image forming apparatus 2 is provided with a booklet mode that is a printing mode in which the image forming order is greatly changed from the page number order. In a typical booklet mode that prints two pages on one side, if the total number of pages is a multiple of 4 as a simple example, the first page and the last page are usually printed on the first side of the first sheet. Then, an image forming order (this is referred to as “standard order”) for printing the second page and the last previous page on the second side is set. The printer controller 27 does not always set such a normal order in the booklet mode, but sets the image forming order according to the number of times that the half-folding process determined for the paper to be used is to be performed. Since the number of times to perform the half-folding process is determined for each paper type option, the setting of the image forming order in the booklet mode is performed according to the paper type designation by the user.

  When a print job requesting image formation in the booklet mode is given, the printer controller 27 notifies the finisher controller 30 of the number of times the middle folding process should be performed. The finisher controller 30 controls the normal conveyance mechanism 34 and the reverse conveyance mechanism 36 so as to carry out the half-fold processing for the number of times notified to the paper and convey it to the subsequent processing unit 38 as a conveyance control unit. The normal transport mechanism 34 passes the paper from the transport roller 41 shown in FIG. 1 through the folding mechanism 32, the transport roller 42, and the transport roller 51 in the post-processing unit 38 to the transport path R1 that reaches the temporary storage space S1. Transport. The reverse conveyance mechanism 36 uses the conveyance rollers 45 and 46 and the guide claws 43 and 44 on the reverse conveyance path R <b> 2 to reverse the sheet with the middle crease by the folding mechanism 32, and re-conveys the paper to the folding mechanism 32. .

  Hereinafter, operations related to the folding process of the image forming system 1 will be described in more detail.

  FIG. 3 shows a procedure for conveying a sheet for both front and back folding processing for performing both valley folding and mountain folding on one sheet. In FIG. 3A, the paper P on the transport path R1 faces the folding mechanism 32. 3B, the folding mechanism 32 performs a folding process that forms a valley fold on the upward surface of the sheet P1, and then the switchback path R2a of the reverse conveying path R2 as shown in FIG. 3C. The paper P is once accommodated. The sheet P1 switched back by the reversal of the conveyance roller pair 45 is guided by the guide claw 43 as shown in FIG. 3D and proceeds in the reversal conveyance path R2. As a result, the sheet P1 that has been turned upside down returns to the transport path R1 through the transport roller pair 46 near the end of the reverse transport path R2, and is re-loaded into the folding mechanism 32. Then, as shown in FIG. 3E, the folding mechanism 32 performs a second folding process in which the upper side of the paper P1 is valley-folded and the lower side is mountain-folded. Thereafter, as shown in FIG. 3F, the sheet P is guided by the guide claw 44 and proceeds along the transport path R1 toward the end thereof. If the front and back reversal conveyance of FIGS. 3B to 3E in such a series of conveyance is repeated, the folding process of the even number of times four times or more can be performed on the paper P.

  FIG. 4 shows the procedure of paper conveyance when only valley folding is performed on one paper surface. In FIG. 4A, the sheet P on the transport path R1 is directed toward the folding mechanism 32. As shown in FIG. 4B, the folding mechanism 32 applies a folding process to the upward surface of the paper P1, and then guides the paper P to the guide claw 44 as shown in FIG. Advances along the transport path R1 toward its end. If the conveyance as shown in FIG. 4 is combined with the above-described reverse-inversion conveyance shown in FIGS. 3B to 3E, the sheet P can be folded three times or more odd times.

  FIG. 5 shows an example of the relationship between the two conveyance modes in the post-processing apparatus 3 and the image forming order in the image forming apparatus 2. Here, it is assumed that a booklet mode operation is performed in which 12 pages are printed on 3 sheets of 4 pages each to create a booklet that opens left (a form in which pages are turned to the left). In the booklet mode of the image forming apparatus 2, the user uses a sheet having a different paper type as the first sheet serving as the cover (cover) of the booklet from the second and subsequent sheets overlapping inside the cover in the folded state. Can be specified. It is also possible to specify the same paper type including the cover. A typical example of changing the paper type is a case where only the cover is made of relatively strong paper such as glossy paper or cardboard in order to improve the appearance of the booklet.

  In the illustration of FIG. 5A, all the sheets are plain papers of the same paper type, and the folding process by the folding mechanism 32 is performed once for all the sheets P1, P2, P3. In this case, since the number of folding processes for each of the sheets P1, P2, and P3 is an odd number, the image forming order is the standard order described above. That is, the last page (12) and the first page (1) are printed on the first surface (first surface) of the first sheet P1 in the discharge order in the image forming apparatus 2 (the numbers in parentheses are Represents the page number). Since it is left-open, page (12) is arranged in the left half of the page, and page (1) is arranged in the right half. Page (2) and page (11) are printed on the second side (second side) of the first sheet P1. Page (10) and page (3) are printed on the first side (third side) of the second sheet P2, and page (4) and page (9) are printed on the second side (fourth side). Printed. Page (8) and page (5) are printed on the first side (fifth side) of the last third sheet P3, and pages (6) and (7) are printed on the second side (sixth side). And are printed.

  The sheets P1, P2, and P3 on which predetermined pages are printed in this order are carried into the post-processing apparatus 3 from the image forming apparatus 2 in a face-down manner with their first surfaces facing downward. In the example, since it is left-opening, folding processing by the folding mechanism 32 is sequentially performed on the sheets P1, P2, and P3 so that the first surface is mountain-folded. The sheets P1, P2, and P3 with the middle folds are stacked in the transport order to form a sheet bundle PG2.

  In the example of FIG. 5B, the first sheet P1b as the cover is a thick sheet, and the other sheets P2 and P3 are plain sheets. The folding process by the folding mechanism 32 is performed twice for the first sheet P1b, and the folding process by the folding mechanism 32 is performed once for the second and subsequent sheets P2, P3. In this case, there are even and odd numbers of times of folding processing of the sheets P1, P2, and P3, which are different from the case where all of them are odd numbers. In this case, the image forming order is an order obtained by changing a part of the standard order. That is, page (2) and page (11) are printed on the first side (first side) of the first sheet P1, and the last page (12) and the first page (second side) are printed on the second side (second side). 1) are printed. For the second and subsequent sheets P2, P3, the corresponding pages are printed in the same order as the standard order.

  The sheets P1b, P2, and P3 on which predetermined pages are printed in this order are sequentially carried from the image forming apparatus 2 to the post-processing apparatus 3 in a face-down manner with their first surfaces facing downward. A folding process is performed on the first sheet P1b by the folding mechanism 32 so that the first surface is a mountain fold, and then the front / back reversal conveyance including the switchback is performed, and the first surface is a valley fold 2. The second folding process is performed by the folding mechanism 32. After that, the folding mechanism 32 applies the first face to the paper P1 and P2 with the first face being folded and folded once. The sheets P1b, P2, and P3 with the middle folds are stacked in the transport order to form a sheet bundle PG3. By appropriately setting the image formation order, the arrangement of a total of 12 pages in the sheet bundle PG3 is the same as the arrangement in the sheet bundle PG2 in FIG.

  As shown in FIG. 6, the sheet transport mechanism can be simplified by changing the image forming order. Temporarily, four pages are printed on the paper P1b without changing the image forming order in the standard order even though the folding process is performed twice only on the paper P1b as the cover. Assume that the first folding process is performed in a face-down state in which the first surface on which page (1) and page (12) are printed is the lower surface as in FIG. 6 (A). Then, it is assumed that the paper P1b is returned to the folding processing position by reversing the front and back. Furthermore, it is assumed that the second folding process is performed in a state where the first surface is the upper surface as shown in FIG. Then, in order to make the front and back directions suitable for stacking, it is necessary to reverse the paper P1b that has undergone the second folding process again. If the sheet is fed in the reverse conveyance path R2, the subsequent sheet cannot be folded during that time, and the subsequent sheet must be kept on standby for a long time. Therefore, it is conceivable to use the switchback path R2a of the reversal conveyance path R2 for front and back reversal. However, a third transport path R3 that guides the switched-back sheet P1b to the transport path R1 is required. Further, it is necessary to extend the switchback path R2a so that almost the entire sheet P1b can be accommodated. That is, if an attempt is made to fold both front and back surfaces without changing the image forming order, the number of components of the paper transport mechanism of the post-processing device 3 increases. In addition, the time required for post-processing is inevitably increased with an increase in the number of times of front / back reversal. In other words, when performing the folding process on both the front and back sides to make the crease good, the post-processing device 3 can be reduced in size and price by changing the order in the image forming stage, and the post-processing can be speeded up. be able to.

  A user of the image forming system 1 uses a user interface on an information device such as an operation panel 20 provided in the image forming apparatus 2 or a personal computer that accesses the image forming apparatus 2 via a network. Can be selected and the contents of the operation settings can be specified.

  FIG. 7 shows an example of an operation screen for an operation for designating the paper type displayed on the touch panel of the operation panel 20. In FIG. 7A, an item selection key 53 for selecting the booklet mode is arranged on the operation screen Q12 which is an initial screen for setting relating to the copy function. When the user touches the item selection key 53, a window Q21 for detailed setting pops up in the pop-up display area of the operation screen Q12. At this time, the background color of the item selection key 53 of the selected item is changed to a color different from the background color of the other item selection keys corresponding to the non-selected items.

  The window Q21 has a plurality of operation keys including an item selection key 74 for designating the booklet opening direction and an item selection key 75 for designating the paper type of the cover. For example, when the user touches the item selection key 75, a window Q31 is popped up partially overlapping the window Q21 as shown in FIG. 7B. The window Q31 has a plurality of selection keys respectively corresponding to a plurality of paper types as options. The user can specify a desired paper type for the cover in the window Q31. The paper type other than the cover used for creating the booklet can be specified by, for example, a window displayed when the item selection key 52 corresponding to the item “paper” on the operation screen Q12 is touched.

  A plurality of paper types that are options in the specifications of the image forming system 1 are grouped from the viewpoint of easiness of folding, and the number of times that folding processing by the folding mechanism 32 is to be performed for each group is determined in advance. Yes. FIG. 8 shows an example of a table T1 that the image forming apparatus 2 stores as folding number information. The table T1 stores data necessary for conveyance control such as the number of foldings and the inter-paper weight for each paper type group. In the example, the number of folding is set to 1 for plain paper, the number of folding is set to 2 for thick paper 1, and the number of folding is set to 3 for thick paper 2.

  When the user selects the booklet mode and designates the cover sheet type, the control setting process shown in FIG. 9 in the image forming apparatus 2 is executed by, for example, the main controller 21. The main controller 21 checks which group the designated paper type corresponds to (S101), reads the data of the corresponding group from the table T1, and sets the control contents for image formation and post-processing. If the designated paper type corresponds to the group “plain paper”, the plain paper processing in step S102 is executed. In plain paper processing, the image forming order is set to the standard order, and all the folding processes are added once. If the designated paper type corresponds to the group “thick paper 1”, the thick paper 1 process in step S103 is executed. In the thick paper 1 process, the image forming order is set to an appropriate order other than the standard order, and the folding process is set to be performed twice for the cover and once for the other sheets. If the designated paper type corresponds to the group “thick paper 2”, the thick paper 2 process in step S104 is executed. In the thick paper 2 processing, the image forming order is set to an appropriate order other than the standard order, and the folding process is set to be performed three times for the cover and once for the other sheets. The contents set in the control setting process are applied to the control by the printer controller 27 and the finisher controller 30.

  In the above embodiment, the configurations of the image forming apparatus 2 and the post-processing apparatus 3 are not limited to the examples. For example, the post-processing device 3 may have another post-processing mechanism such as a punch punching mechanism or a side stitching mechanism upstream or downstream of the folding mechanism 32. The shapes and lengths of the transport path R1 and the reverse transport path R2 should be appropriately selected according to the apparatus configuration. Further, the post-processing device 3 may be capable of not only an online operation in cooperation with the image forming apparatus 2 but also an offline operation for processing paper set in the paper stacker.

  The conveyance control means for controlling the normal conveyance mechanism 34 and the reverse conveyance mechanism 36 of the post-processing apparatus 3 is not necessarily provided in the post-processing apparatus 3 and may be provided in the image forming apparatus 2.

  In the booklet mode, the maximum number of pages per sheet is not limited to four, and may be a multiple of four. The image forming order may be set according to the maximum number of pages per sheet and the opening direction.

DESCRIPTION OF SYMBOLS 1 Image formation system 2 Image formation apparatus 3 Post-processing apparatus 32 Folding mechanism 34 Normal conveyance mechanism 36 Reverse conveyance mechanism P, P1, P1b, P2, P3 Paper 24 Printer engine (image formation part)
27 Printer controller (image formation controller)
26 Paper discharge mechanism 30 Finisher controller (conveyance control unit)
T1 table (fold number information)

Claims (5)

An image forming system having an image forming apparatus and a post-processing apparatus,
The post-processing device includes:
A folding mechanism for making a middle crease on the paper discharged from the image forming apparatus;
A normal transport mechanism for transporting the sheet with the middle crease by the folding mechanism to a subsequent processing section;
A reversing conveyance mechanism that reverses the front and back of the sheet with the middle crease by the folding mechanism and re-conveys to the folding mechanism,
The image forming apparatus includes:
Image formation in which an image forming order is set in units of pages according to the number of times that the folding mechanism defined by the folding mechanism should be performed on a sheet used for image formation when forming an image for a plurality of pages. A control unit;
An image forming unit that forms the images for the plurality of pages in the image forming order set by the image forming control unit;
A paper discharge mechanism for discharging paper used for image formation for the plurality of pages by the image forming unit to the post-processing device,
Either the image forming apparatus or the post-processing apparatus performs the normal folding mechanism on the paper ejected from the image forming apparatus and transports it to the post-processing unit so as to perform the half-folding process. An image forming system comprising: a conveyance control unit that controls the reverse conveyance mechanism. In the case where a plurality of sheets are used for forming the images for the plurality of pages, the image formation control unit is configured such that at least one of the plurality of numerical values determined as the number of times for each of the plurality of sheets is an even number. The image forming system according to claim 1, wherein a different order is set as the image forming order when there is a certain number and when all of the plurality of numerical values are odd numbers. The image forming apparatus stores folding number information indicating the number of times determined for each of a plurality of paper types,
The image forming system according to claim 2, wherein the image forming control unit sets the image forming order according to the number of times corresponding to a paper type of a sheet designated by a user of the image forming system in the folding number information. . The image forming apparatus is an image forming mode in which images of a plurality of pages are formed using a plurality of sheets, and the user is different from the sheet type of the second and subsequent sheets with respect to the first sheet. The image forming system according to claim 3, further comprising a booklet mode in which a paper type can be specified. A post-processing device that processes a sheet on which an image is formed,
A folding mechanism for making a middle crease in the paper;
A normal transport mechanism for transporting the sheet with the middle crease by the folding mechanism to a subsequent processing section;
A reversing conveyance mechanism for reversing the front and back of the sheet with the middle crease by the folding mechanism and re-conveying to the folding mechanism;
In accordance with the number of times of performing the middle folding process by the folding mechanism determined in advance for the sheet, the normal folding process is performed for the number of times and the sheet is conveyed to the subsequent processing unit. A post-processing apparatus comprising: a transport mechanism; and a transport control unit that controls the reverse transport mechanism.

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