JP7641137B2 - METHOD FOR MAINTENANCE OF PRINT HEAD IN INKJET PRINTING APPARATUS AND INKJET PRINTING APPARATUS USING SAME - Google Patents

Description

The present invention relates to a method for maintaining a print head in an inkjet printing device and an inkjet printing device using the same, and in particular to a method for maintaining a print head that is composed of multiple head modules.

Conventionally, some inkjet printing devices of this type are equipped with a print head configured by arranging multiple head modules in the width direction of the print paper. Each head module has multiple nozzles in at least the width direction of the print paper, either in the transport direction or the width direction. The head module has a drive board for driving each nozzle, and a memory for storing the ejection characteristics of the head module. If the frequency of nozzles not ejecting in the head module becomes higher than a certain value, or if the number of nozzles that are not ejecting exceeds a predetermined value, a malfunction of the print head is reported, and maintenance of the print head is performed.

As a first method, for example, a defective head module is replaced with a new head module (see, for example, Patent Document 1). The head module is given unique identification information. During maintenance, the identification information of the head module that was removed due to a malfunction is compared with the identification information of the installed head module, and if the head module that was removed due to a malfunction is mistakenly reinstalled, this is notified. This prevents a defective head module from being installed due to a work error.

In the first method described above, there is a risk of density differences occurring between adjacent head modules. In such a situation, print quality will decrease. Therefore, as a second method, for example, there is one in which the defective head module is replaced with a new head module, and then the ejection characteristics of the new head module are corrected (see, for example, Patent Document 2). This reduces density differences between adjacent head modules, and suppresses deterioration of print quality.

The second method described above requires the effort of correcting the ejection characteristics. Therefore, a third method involves, for example, replacing a head module adjacent to a defective head module that has been replaced with a new head module that has an inverse density gradient in the width direction (see, for example, Patent Document 3). This makes it possible to suppress density unevenness at the joints between adjacent head modules with little effort.

JP 2019-166708 A JP 2013-78943 A JP 2015-47833 A

However, the conventional example having such a configuration has the following problems.
That is, the conventional method is based on the premise that if a malfunction occurs in the print head, the head module is replaced with a new one. The print head is composed of multiple head modules. Therefore, it may be possible to restore the print quality to the same level as before the malfunction occurred by simply changing the position of the defective head module, without having to replace the defective head module with a new head module. Nevertheless, since the defective head module is replaced with a new one, when a malfunction occurs in the head module, the frequency of head module replacement increases. This results in a problem of increased operating costs for the device.

The present invention has been made in consideration of these circumstances, and aims to provide a method for maintaining the print head in an inkjet printing device that can reduce operating costs even if a malfunction occurs in the head module, and an inkjet printing device using the same.

In order to achieve the above object, the present invention has the following configuration.
That is, the invention described in claim 1 is a method for maintaining a print head in an inkjet printing device equipped with a print head composed of a plurality of head modules that print by ejecting ink onto a printing medium, the method comprising the steps of: detecting that a malfunction has occurred in any of the head modules that constitute the print head; and determining whether or not print quality by the print head can be maintained by treating the head module in which the malfunction has occurred as a defective head module and replacing the position of the defective head module in the print head based on unique information including the ejection characteristics of each head module that constitutes the print head excluding the defective head module and the unique information of the defective head module. and, if it is determined by the judgment step that printing quality can be maintained, a notification step of notifying the switching of the position , wherein the judgment step is characterized in that it determines whether, when the defective head module has caused an ejection abnormality, printing quality can be maintained by switching the position of the defective head module on the print head so that the defective head module is positioned at the end of the print head, or, when the defective head module has caused a density distribution defect, printing quality can be maintained by switching the position of the defective head module on the print head so that the difference in density distribution between adjacent parts of the head modules is within a certain range .

[Actions and Effects] According to the invention described in claim 1, if a malfunction is detected in one of the head modules in the detection step, a determination step is made as to whether the print quality of the print head can be maintained by swapping the position of the defective head module, based on the unique information of each head module and the unique information of the defective head module. If it is determined that the print quality can be maintained by swapping the position, the swapping of the position is notified in the notification step. Therefore, by swapping the position of the notified head module with the defective head module, the frequency of replacement with a new head module can be reduced. Therefore, even if a malfunction occurs in a head module, the operating costs of the device can be reduced.

The unique information referred to here refers to the density distribution that indicates the relationship between the position and the amount of ejection for the multiple nozzles that the head module has, the position of the non-ejecting nozzles, the frequency with which the nozzles fail to eject, etc.

The judgment step can determine whether print quality can be maintained by placing the defective head module at the end of the print head when a defective head module causes an ejection abnormality or a density distribution problem, or whether print quality can be maintained by replacing the defective head module with another head module when a density distribution problem occurs.

The invention described in claim 2 is a method for maintaining a print head in an inkjet printing device equipped with a print head composed of a plurality of head modules that print by ejecting ink onto a printing medium, the method comprising the steps of: detecting that a malfunction has occurred in any of the head modules that compose the print head; determining whether or not the print quality of the print head can be maintained by treating the head module in which the malfunction has occurred as a defective head module and replacing the defective head module in the print head based on unique information including the ejection characteristics of each head module that composes the print head excluding the defective head module and the unique information of the defective head module; and determining whether or not the print quality of the print head can be maintained by the determination step. and if it is determined in the determination step that the printing quality cannot be maintained by replacing the defective head module in the print head, a notification step is carried out to notify the replacement of the position.If it is determined in the determination step that the printing quality cannot be maintained by replacing the defective head module in the print head, a database storing unique information about a plurality of new head modules is accessed, and a new head module that can maintain the printing quality by replacing the defective head module is searched for based on the unique information of the defective head module and the unique information of each head module that constitutes the print head excluding the defective head module, and if the new head module that can maintain the printing quality is determined to be the new head module, an exchange presentation step is carried out to present the new head module.

If it is determined in the judgment step that print quality cannot be maintained by simply swapping the layout, a database is accessed and a new head module capable of maintaining print quality is searched for based on the unique information of the defective head module and the unique information of the other head modules in the print head excluding the defective head module. Then, in the replacement suggestion step, a new head module capable of maintaining print quality is presented. In this way, by replacing the defective head module with the new head module, a suitable head module can be obtained, and the print quality of the print head can be maintained.

In addition, in the present invention, in addition to the replacement suggestion step, it is preferable to carry out an alternative suggestion step in which, based on the unique information of the new head module and the unique information of all head modules that make up the print head excluding the defective head module, the print quality of a simple replacement when the new head module is replaced with the defective head module is compared with the print quality of various replacements when the arrangement positions of each head module excluding the defective head module are replaced with the new head module, and the one with higher print quality is also suggested (Claim 3) .

The print quality of a simple replacement in which the defective head module is replaced with a new head module is compared with the print quality of various replacements in which each head module of the print head is replaced with a new head module. Then, in the alternative proposal presentation step, the alternative with the highest print quality is also presented. This allows the user to increase the options available when replacing a head module, allowing for the replacement of a suitable head module.

The invention described in claim 4 is a method for maintaining a print head in an inkjet printing device equipped with a print head composed of a plurality of head modules that print by ejecting ink onto a printing medium, the method comprising the steps of: detecting that a malfunction has occurred in any of the head modules that compose the print head; and determining whether or not print quality by the print head can be maintained by treating the head module in which the malfunction has occurred as a defective head module and replacing the position of the defective head module in the print head based on unique information including ejection characteristics of each head module that composes the print head excluding the defective head module and the unique information of the defective head module. and if it is determined by the judgment step that printing quality can be maintained, a notification step is carried out of notifying the change in the placement position, and if the head module can be attached to the print head in an attitude facing either the feed direction in the transport direction of the printing medium or the counter-feed direction opposite to the feed direction, the head module has an attachment direction of either the feed direction or the counter-feed direction in the unique information, and in the judgment step, if the attachment direction in the unique information of the head module is different from the attachment direction of the head module, the attachment direction of the unique information is updated to the correct direction, and any unique information that has directionality is reversed to a direction perpendicular to the transport direction of the printing medium.

If the head module can be mounted in both the feed direction and the counter-feed direction, the unique information includes the mounting direction. If the mounting direction in the unique information of the head module being judged differs from the actual mounting direction of the head module, the mounting direction in the unique information is updated to the correct direction, and if the unique information has directionality, it is inverted to a direction perpendicular to the transport direction of the print medium. Therefore, in the judgment step, a correct judgment can be made based on the unique information depending on the mounting direction.

In the present invention, it is preferable that, prior to the determining step, an installation direction detecting step is carried out for detecting the installation direction of each head module constituting the print head (claim 5) .

By performing the mounting direction detection step, the determination step can make an accurate determination based on the unique information depending on the mounting direction of the head module.

The invention described in claim 6 is an inkjet printing device equipped with a print head composed of a plurality of head modules which print by ejecting ink onto a print medium, the device comprising: a transport section which transports the print medium in a predetermined transport direction; a control section which operates the print head to cause it to print onto the print medium; a detection section which detects that a malfunction has occurred in any of the head modules which constitute the print head; a head memory which is provided for each of the head modules and which stores unique information including ejection characteristics; and a head module in which the malfunction has occurred is designated as a defective head module, and a position of the defective head module in the print head is determined based on the unique information for each head module which constitutes the print head excluding the defective head module and the unique information for the defective head module. The ink jet head is provided with a judgment unit which judges whether the printing quality of the print head can be maintained by replacing the defective head module, and a notification unit which notifies the user of the replacement of the position when the judgment unit judges that the printing quality can be maintained. The judgment unit is characterized in that it judges whether, when the defective head module has caused an ejection abnormality, the printing quality can be maintained by replacing the position of the defective head module on the print head so that the defective head module is placed at the end of the print head, or whether, when a defect in the concentration distribution of the defective head module has occurred, the printing quality can be maintained by replacing the position of the defective head module on the print head so that the difference in concentration distribution in adjacent portions of the head modules is within a certain range .

[Function and Effect] According to the invention described in claim 6 , the control unit operates the print head to perform printing while the transport unit transports the print medium. If the detection unit detects a malfunction in a head module, the judgment unit judges whether the print quality of the print head can be maintained by swapping the position of the defective head module based on the unique information of each head module and the unique information of the defective head module. If it is determined that the print quality can be maintained by swapping the position, the notification unit notifies the swapping of the position. Therefore, by swapping the position of the notified head module with the defective head module, the frequency of replacement with a new head module can be reduced. Therefore, the operating costs of the device can be reduced even if a malfunction occurs in a head module.

According to the print head maintenance method for an inkjet printing device of the present invention, when a malfunction in one of the head modules is detected in the detection step, a determination step is made as to whether the print quality of the print head can be maintained by swapping the position of the defective head module, based on the unique information of each head module and the unique information of the defective head module. If it is determined that the print quality can be maintained by swapping the position, the swapping of the position is notified in the notification step. Therefore, by swapping the position of the notified head module with the defective head module, the frequency of replacement with a new head module can be reduced. Therefore, even if a malfunction occurs in a head module, the operating costs of the device can be reduced.

1 is a diagram illustrating the overall configuration of an inkjet printing apparatus according to an embodiment. FIG. 2 is a plan view showing the positional relationship between a print head and continuous paper. FIG. 13 is a schematic diagram showing an example of unique information. FIG. 2 is a schematic diagram showing the unique information of the head modules that make up the print head arranged side by side. 5 is a flowchart showing a process flow during a printing operation. 13 is a flowchart showing a process flow during maintenance processing. 13A is a schematic diagram showing an arrangement of unique information indicating a current state, and FIG. 13B is a schematic diagram showing an arrangement of unique information indicating a state in which the information has been rearranged based on density distribution. 13A is a schematic diagram showing a list of unique information indicating a current state, and FIG. 13B is a schematic diagram showing a list of unique information indicating a state after the list has been rearranged based on the position where an abnormal nozzle has occurred. 13 is a schematic diagram showing a sequence of unique information used to explain a case where replacement is performed based on a severity tolerance threshold. FIG. 13 is a diagram showing a configuration for determining the mounting direction as viewed from the transport direction. FIG. 13A shows the arrangement of unique information when the mounting direction is −1, and FIG. 13B shows the arrangement of unique information when the mounting direction is determined to be +1. 5A and 5B are schematic diagrams illustrating the relationship between the mounting direction and the flow path direction.

An embodiment of the present invention will now be described with reference to the drawings.
Fig. 1 is a diagram showing the overall configuration of an inkjet printing apparatus according to an embodiment of the present invention, Fig. 2 is a plan view showing the positional relationship between a print head and continuous paper.

<Device configuration>

The inkjet printing device 1 includes a paper feed section 3, a printing device 5, and a paper discharge section 7. The inkjet printing device 1 is connected to a head module station 9 so that it can communicate with the head module station 9. The inkjet printing device 1 also receives print data, which is the data for the printed matter, from a host computer (not shown).

The paper feed unit 3 unwinds, for example, a roll of the continuous paper WP in the transport direction X. The paper feed unit 3 is loaded with a roll of the continuous paper WP with its rotation axis facing the width direction Y perpendicular to the transport direction X. The printing device 5 takes in the continuous paper WP unwound from the paper feed unit 3 and performs a printing process on the continuous paper WP. The printed continuous paper is wound around a horizontal axis in the paper discharge unit 7.

The printing device 5 includes a drive roller 11, a print head 13, a plurality of transport rollers 15, a drying section 17, a scanning section 19, a drive roller 21, and a bottom surface imaging section 23.

The drive roller 11 takes in the web paper WP from the paper feed section 2 and transports the web paper WP in the transport direction X. The print head 13 is disposed downstream of the drive roller 11 in the transport direction X. The print head 13 includes a plurality of head modules 25. The print head 13 ejects ink onto the top surface of the web paper WP to form an image. The print head 13 will be described in more detail below.

A drying unit 17 is disposed downstream of the print head 15. The drying unit 17 dries the ink ejected onto the web paper WP. A scanning unit 19 is disposed downstream of the drying unit 17. The scanning unit 19 scans the image of the dried web paper WP. A drive roller 21 is disposed downstream of the scanning unit 19. The drive roller 21 sends the web paper WP scanned by the scanning unit 19 to the paper discharge unit 7.

A bottom surface imaging unit 23 is disposed between the bottom surface of the print head 13 and the top surface of the web paper WP. This bottom surface imaging unit 23 is configured to be movable between a shooting position directly below the bottom surface of the print head 13 and a standby position offset to the side from the print head 13. The bottom surface imaging unit 23 images the bottom surface (nozzle surface) of each head module 25 that makes up the print head 13.

As shown in FIG. 2, the print head 13 is composed of multiple head modules 25. Each head module 25 has multiple nozzles 27 in at least the transport direction X and the width direction Y. FIG. 2 shows a configuration with five head modules 25 as an example. In this embodiment, when it is necessary to distinguish between each of the five head modules 25, the head modules 25 are referred to as head modules HM1 to HM5, respectively.

2, the print head 13 is, for example, downstream in the transport direction X, with head module HM1 arranged on the left side in the width direction Y, head module HM3 arranged spaced apart to the right of head module HM1 in the width direction Y, and head module HM5 arranged spaced apart to the right of head module HM3 in the width direction Y. The print head 13 is, for example, upstream in the transport direction X, with head module HM2 arranged on the left side in the width direction Y, and head module HM4 arranged spaced apart to the right of head module HM2 in the width direction Y. When viewed from the upstream side of the print head 13 toward the transport direction X, the head modules HM1 to HM3 are arranged in the width direction Y such that the right end of head module HM1 and the left end of head module HM3 overlap both ends of head module HM2. When viewed from the upstream side of the print head 13 in the transport direction X, the head modules HM3 to HM5 are arranged in the width direction Y so that the right end of the head module HM3 and the left end of the head module HM5 overlap both ends of the head module HM4. This arrangement of the head modules 25 is also called a "staggered arrangement."

The print head 13 has a length that exceeds the print area PA of the web paper WP in the width direction Y. The print area PA is the area in which images and the like are printed by the print head 13. This print area PA is set at a position a predetermined distance inward from both ends of the web paper WP in the width direction Y. Furthermore, the length in the width direction Y that can be printed by the print head 13 exceeds the width direction Y dimension of the print area PA and also exceeds the width direction Y dimension of the web paper WP. This is so that the print head 13 can print in the width direction Y of the web paper WP even if the web paper WP meanders in the transport direction X.

As shown in FIG. 2, the continuous paper WP has a gap between each printing area PA. For example, a test chart TC is printed in this gap. This test chart TC is made up of five individual charts formed for each head module 25. Each individual chart is formed, for example, by ejecting a predetermined pattern at a predetermined density from all the nozzles 27 that make up each head module 25. From these individual charts, various ejection characteristics for each head module 25 can be obtained.

Each head module 25 has a built-in head memory 29. Each head memory 29 stores information specific to each head module 25.

Here, reference is made to Figure 3, which is a schematic diagram showing an example of unique information.

The unique information is information for each head module 25, including the ejection characteristics. For example, the unique information includes a serial number, a density distribution, correction information, an abnormal nozzle occurrence position, an abnormal nozzle occurrence frequency, and history and statistical information. The serial number is the manufacturing number of the head module 25, and is a unique number that does not overlap with other head modules. The density distribution is density information for all nozzles 27 of the head module 25. Specifically, for the nozzles 27 arranged in the width direction Y, the density of an image formed by applying a predetermined signal is arranged for each width direction Y. The correction information is information representing the value of a signal that is applied to each nozzle 27 to correct the density distribution, if there is a signal. The abnormal nozzle occurrence position is information representing the position of the nozzle 27, if the nozzle 27 has an abnormality such as non-ejection or chipping. The abnormal nozzle occurrence frequency is information indicating the frequency of abnormality in the abnormal nozzle 27. The history and statistical information is information such as the number of times ink has been ejected by the head module 25 and the cumulative time that it has been attached to the print head 13 and powered on.

The printing device 5 includes a head control unit 31, a data processing unit 33, a display unit 35, a database 37, and a control unit 39.

The head control unit 31 is operated by the control unit 39. The head control unit 31 is composed of a circuit board, and operates the print head 13 in response to a signal from the control unit 39 based on the print data. The head control unit 31 operates each head module 25 in response to a signal from the control unit 39. The head control unit 31 is capable of reading and writing from each head memory 29. The head control unit 31, for example, refers to unique information stored in the head memory 29, and corrects the signal from the control unit 39 based on that information. The head control unit 31 also transmits the unique information read from the head memory 29 to the control unit 39.

The data processing unit 33 is connected to the scanning unit 19 and the bottom surface photographing unit 23. The scanning unit 19 photographs an image of the continuous paper WP printed by the print head 13 and converts the image into digital data. The image referred to here is an image within the print area PA and a test chart TC outside the print area PA. The data processing unit 33 judges the print quality of the printed image based on the data from the scanning unit 19. The data processing unit 33 also outputs information on the ejection characteristics based on the data of the test chart TC from the scanning unit 19. The bottom surface photographing unit 23 photographs the bottom surface of each head module 25 at a photographing position directly below the bottom surface of the print head 13. The photographed bottom surface image is output to the data processing unit 33 as digital data. The data processing unit 33 collects information indicating non-ejection or chipping of each nozzle 27 in each head module 25 based on the bottom surface image. The collected information is output to the control unit 39.

The display unit 35 is composed of a display device such as a liquid crystal display device. The display unit 35 displays information according to a signal from the control unit 39. For example, if a problem occurs with the head module 25, the display unit 35 displays that information. The display unit 35 displays, as will be described in detail later, information on the replacement of the placement position based on unique information, and information on alternative proposals based on a simple replacement with a new head module 25 and various replacements in which the new head module 25 is placed in various positions.

The database 37 is connected to the head module station 9. The head module station 9 is configured to allow multiple head modules 25 to be attached. The head module station 37 reads out unique information from the head memory 29 of each attached head module 25. The read out unique information is sent to the database 37. The database 37 stores unique information associated with each head module 25 connected to the head module station 9. The control unit 39 accesses the database 37 and refers to the unique information of each head module 25.

The control unit 39 comprehensively controls the drive rollers 11, 21, the drying unit 17, the scanning unit 19, the underside image capturing unit 23, the head control unit 31, the data processing unit 33, the display unit 35, and the database 37. The control unit 39 may also be connected to the inkjet printing device 1 for reverse side printing via, for example, an inversion device (not shown) disposed downstream of the inkjet printing device 1. In such a case, the control unit 39 also communicates with the inkjet printing device 1 for reverse side printing. For example, the control unit 39 acquires unique information, etc., from the inkjet printing device 1 for reverse side printing as external information.

The control unit 39 also obtains the unique information shown in FIG. 3 from the print head 13. Here, reference is made to FIG. 4. FIG. 4 is a schematic diagram showing the unique information of the head modules that make up the print head arranged in an order. The control unit 39 reads out the unique information of each head module 25 that makes up the print head 13 via the head control unit 31. For example, the control unit 39 refers to the unique information arranged in order from the leftmost head module HM1 to the rightmost head module HM5 in the width direction Y. In this example, only the concentration distribution, the position where the abnormal nozzle occurs, and the frequency of abnormal nozzle occurrence are shown among the unique information. In this way, the control unit 39 grasps the unique information of all the head modules 25 that make up the current print head 13 at an appropriate timing.

The control unit 39 detects that a nozzle malfunction has occurred based on information from the data processing unit 33. When the control unit 39 detects that a nozzle malfunction has occurred, it displays on the display unit 35 what type of malfunction has occurred in which head module 25 that constitutes the print head 13. Furthermore, the control unit 39 does not simply notify the user that a malfunction has occurred, but also determines whether print quality can be maintained by replacing the position of the head module 25 that has malfunctioned with another head module 25 that currently constitutes the print head 13.

Here, maintaining print quality refers to the following cases, for example. The print quality of the head modules HM2 to HM4 near the center of the print head 13 will decrease if there is a non-ejecting nozzle 27 even at the end of each. Therefore, if there is a non-ejecting nozzle 27 at the left end of the head module HM2, the position of the head module HM2 and the head module HM1 are swapped. The head module HM2 arranged at the leftmost end has its left end located outside the printing area PA, so it is used very infrequently. Therefore, it can be determined that print quality can be maintained even if the head module HM2 is arranged at the left end in the width direction Y. In addition, for nozzles 27 whose non-ejection frequency has reached a certain level or more, if they are located at the end of the head module 25, they may be arranged so that they are located outside the printing area PA. Note that even if they are not outside the printing area PA, but are swapped to be located at the end of the printing area PA depending on the printing data, it can be determined that print quality can be maintained. Therefore, it is preferable to determine whether print quality can be maintained by taking the printing data into consideration.

In addition, the print quality also deteriorates when the difference in density distribution between adjacent parts of each head module 25 in the print head 13 is equal to or greater than a certain level. For example, as shown in FIG. 4, the difference between the adjacent parts of the head module HM2 and the head module HM3 is greater than that between other adjacent parts, and the difference in density distribution is equal to or greater than a certain level. In such a case, the print quality deteriorates. Therefore, for example, the positions of the head module HM2 and the head module HM5 are swapped so that the difference in density distribution between adjacent parts is within a certain level. Even if a defect in density distribution occurs in this way, the print quality may be maintained by swapping the positions. The control unit 39 refers to the unique information of the defective head module 25 and the unique information of the other head modules 25 to determine whether the print quality can be maintained by swapping the positions. The difference as the threshold value of the density distribution when making the above determination is determined in advance by experimentation as the difference in density distribution at which print quality can be maintained, and the value is stored in the control unit 39 as the threshold value.

The continuous paper WP described above corresponds to the "printing medium" in the present invention, the drive rollers 11 and 21 and the transport roller 15 correspond to the "transport section" in the present invention, the scanning section 19, the bottom surface photographing section 23 and the data processing section 33 correspond to the "detection section" in the present invention, the control section 39 corresponds to the "determination section" in the present invention, and the display section 35 corresponds to the "notification section" in the present invention.

<When printing>

The operation of the inkjet printing device 1 configured as described above will be described with reference to Figs. 5 and 6. Fig. 5 is a flow chart showing the process flow during printing operation. Fig. 6 is a flow chart showing the process flow during maintenance processing.

Step S1
Prior to a printing operation for executing one job, which is one block of printing processing, the control unit 39 receives unique information for all of the head modules 25 that make up the print head 15 .

Step S2
The control unit 39 executes printing. Specifically, the continuous paper WP is conveyed in the conveying direction X at a conveying speed according to the printing conditions in accordance with the received print data and the printing conditions set in advance, while the drying unit 17 performs drying at a drying temperature according to the printing conditions. At that time, printing is performed while ejecting ink from the print head 13 based on the unique information. For example, if the unique information of the head module 25 includes correction information, the head control unit 31 corrects a signal according to the print data according to the correction information and outputs a signal to the head module 25 to perform printing processing. Note that it is preferable to print a test chart TC each time between the printing areas PA. The test chart TC includes a pattern that can obtain the density distribution of the head module 25 and a pattern that can determine non-ejection, chipping, etc.

Step S3
The control unit 39 operates the scanning unit 19 to capture an image of the printed surface of the web paper WP printed in step S2. The data processing unit 33 converts the image of the print area PA and the image of the test chart TC printed outside the print area PA into digital data.

Step S4
The control unit 39 operates the bottom surface imaging unit 23 to image the bottom surface of the print head 13. The data processing unit 33 converts the image of the bottom surface of the print head 13, the area including all of the head modules 25, into digital data.

Step S5
The data processing unit 33 calculates unique information for each head module 25 based on the digital data collected in steps S3 and S4. For example, it calculates density distribution based on the test chart TC, identifies the positions of nozzles that are not ejecting or are missing as abnormal nozzle occurrence positions based on the test chart TC and an image of the bottom surface of the print head 13, and calculates the frequency of abnormal nozzle occurrence. It also calculates history and statistical information according to the operating time, etc.

Step S6
The unique information calculated in step S5 for each head module 25 is transmitted to the control unit 39. The control unit 39 writes the unique information in the head memory 29 of the head module 25 via the head control unit 31 to update it.

Step S7
The control unit 39 refers to the unique information of each head module 25 updated in step S6, and judges whether or not there is a problem with the print quality based on the density distribution, the position where the abnormal nozzle occurs, the frequency of occurrence of the abnormal nozzle, etc. If the control unit 39 judges that there is no problem with the print quality, it ends the job. On the other hand, if the control unit 39 judges that there is a problem with the print quality, it branches the process to step S8.

Step S8
The control unit 39 executes maintenance processing for the print head 13 .

Note that step S7 described above corresponds to the "detection step" in this invention.

<Maintenance processing>

Now, let's refer to Figure 6.

Step S11
The control unit 39 branches the process depending on whether or not it is possible to maintain the print quality by replacing the head module 25 for the print head 13. If it is possible to maintain the print quality by replacing the head module 25, the process branches to step S12, and if it is difficult to maintain the print quality by replacing the head module 25, the process branches to step S13.

The control unit 39 judges whether or not printing quality can be maintained by replacing the head module 25, for example, as follows. Reference is now made to Figures 7 and 8. Figure 7(a) shows the arrangement of unique information indicating the current state, and Figure 7(b) is a schematic diagram showing the arrangement of unique information indicating the state after replacement based on the density distribution. Figure 8(a) shows the arrangement of unique information indicating the current state, and Figure 8(b) is a schematic diagram showing the arrangement of unique information indicating the state after replacement based on the position of the abnormal nozzle.

For example, as shown in FIG. 7(a), the control unit 39 refers to the unique information of all head modules 25 that make up the print head 13. Here, it is assumed that the density difference exceeds a threshold value in the adjacent area between head module HM2 and head module HM3. As a result, it is assumed that the control unit 39 determines that a malfunction has occurred in head module HM2. In other words, it is assumed that a malfunction has occurred in the density distribution. It may also be determined that a malfunction has occurred in head module HM3 adjacent to head module HM2. In that case, for example, it is preferable to determine that a malfunction has occurred in the head module 25 whose density distribution has changed significantly by comparing it with the previous unique information.

The control unit 39 determines the density difference in each adjacent portion of the density distribution in the print head 13 for each combination in which the defective head module HM2 is swapped adjacent to each of the remaining head modules HM1, HM3 to HM5 excluding the defective head module HM2, based on the density distribution of the unique information of all head modules 25 of the print head 13. If this trial results in a combination that can eliminate the defect, the process proceeds to step S12.

Note that step S11 described above corresponds to the "judgment step" in this invention.

Step S12
The control unit 39 displays on the display unit 35 information on the replacement of the combination of the head modules 25 that can eliminate the malfunction.

As the replacement information, the arrangement of the head modules 25 in the print head 13 for which the density difference is below the threshold value is presented. For example, in FIG. 7(a), if the head module HM2 and the head module HM5 are swapped and arranged, the density distribution between the head module HM2 that is determined to be defective and the adjacent head module HM3 will be below the threshold value as shown in FIG. 7(b). If only this combination has a density difference below the threshold value in the adjacent parts, the control unit 39 outputs the arrangement of the head modules 25 as shown in FIG. 7(b) to the display unit 35. If there are any other arrangements of the head modules 25 in the print head 13 for which the density difference is below the threshold value as a result of swapping, all of them are displayed.

The above example is a case where the head module 25 has a defect in density distribution, but for example, a case where a non-ejection occurs in the head module 25 will be described. For example, as shown in FIG. 8A, in the unique information of the head module HM4, the abnormal nozzle occurrence position is 1, 5, and the abnormal nozzle occurrence frequency is 12345, 13456. Here, the abnormal nozzle occurrence position 1, 5 indicates the vicinity of the left end in the width direction Y. In addition, the abnormal nozzle occurrence frequency 12345, 13456 indicates that ejection is rare. Therefore, the control unit 39 determines that a defect has occurred in the head module HM4. From the abnormal nozzle occurrence position in the unique information, the control unit 39 can determine that the nozzle 27 where the non-ejection occurs in this head module HM4 is near the left end of the head module HM4 in the width direction Y. Therefore, when the control unit 39 takes into account the known positional relationship between the print head 13 and the printing area PA, it is determined that the position of the abnormal nozzle in the defective head module HM4 can be positioned outside the printing area PA. Therefore, the control unit 39 can determine that printing quality can be maintained by replacing the head module HM4 with the head module HM1.

In this case, in step S12, the control unit 39 displays on the display unit 35 information on replacing the head module 25 that can resolve the problem, as shown in FIG. 8(b).

Note that step S12 described above corresponds to the "notification step" in the present invention.

Step S13
In the above-mentioned step S11, if it is difficult to maintain the print quality by replacing the head module 25, the process branches to step S13.

The control unit 39 refers to the database 37. The database 37 stores the unique information of all head modules 25 attached to the head module station 9, corresponding to each head module 25 attached to the head module station 9 by its serial number. The control unit 39 searches through each head module 25 for a new head module 25 that can maintain print quality by replacing the defective head module 25. As a result, when the control unit 39 finds a new head module 25 that can maintain print quality, it causes the display unit 35 to display the new head module 25 attached to the head module station 9. This provides replacement information to the operator.

In addition, it is preferable that the control unit 39 searches whether print quality can be maintained in various replacement cases, such as when a new head module 25 is replaced while rearranging the positions of the remaining head modules 25 excluding the defective head module 25, rather than simply replacing the defective head module 25 with a new head module 25. This allows for a more optimal arrangement of the head modules 25 in the print head 13, which may improve print quality.

Note that step S13 described above corresponds to the "exchange offer step" and "alternative offer offer step" in this invention.

Step S14
The operator of the inkjet printing apparatus 1 replaces or exchanges the head module 25 in accordance with the replacement information or the alternative proposal information displayed on the display unit 35 .

Step S15
When the replacement or exchange work of the head modules 25 is completed, the control unit 39 acquires unique information from all of the head modules 25 that make up the print head 13 .

Step S16
The control unit 39 determines whether the attached head module 25 is new or second-hand based on, for example, history and statistical information among the unique information of the attached head module 25 .

Steps S17 and S18
If the head module 25 replaced in step S13 is new, a test chart TC is printed. Then, the scanning unit 19 and the bottom surface photographing unit 23 are operated to obtain unique information such as density information and abnormal nozzle occurrence position. Even if the head module 25 is new, a printing operation may be performed in a test machine to determine a reference voltage and the like during the manufacturing stage of the head module 25. In that case, the unique information is stored in the head memory 29. However, the unique information at the time the head module 25 is manufactured may differ from the unique information at the time it is attached. Therefore, this step S17 is performed to update the unique information of the head module 25 currently constituting the print head 13 to the latest state. This makes it possible to obtain the latest unique information.

Step S19
The control unit 39 calculates the optimal position of the new head module 25 based on the unique information of the new head module 25 that has been installed by replacement and has been updated to the latest state, taking into consideration the density distribution, the position where the abnormal nozzle occurs, etc.

Step S20
When the optimal position is calculated in step S19, the control unit 39 presents the position information by outputting it to the display unit 35. When this is presented, the user of the inkjet printing device 1 decides whether or not to replace the presented position information, and replaces it if necessary. This makes it possible to place the head module 25 in a more optimal position, thereby improving print quality.

<How to find the optimal layout>

In step S19 described above, the optimal position of the head module 25 is calculated based on the latest unique information. A suitable method for calculating the optimal position is described below.

Now, reference is made to FIG. 9. FIG. 9 is a schematic diagram showing an arrangement of unique information used to explain the case of replacement based on the severity tolerance threshold. Note that in FIG. 9, as an example, the head module 25 is composed of seven pieces, but some of them are omitted from the illustration.

For example, the optimal arrangement is determined for head module HM1 located at the leftmost position in the width direction Y and head module HM4 located in the center in the width direction Y. Here, the unique information stores, for example, the position where an abnormal nozzle occurs and its frequency of occurrence in association with each other. At first glance, this may look different from the unique information in Figure 3 described above, but since the nozzle position is associated with its frequency, it is the same unique information. The difference is that the unique information in Figure 9 includes a severity tolerance threshold.

This severity tolerance threshold is a reference value for determining whether the severity is high or low when compared with the severity obtained as follows. It is preferable to arrange the head module 25 with a severity lower than this severity tolerance threshold. The severity tolerance threshold is set in advance so that it is small at the center of the print head 13 in the width direction Y and large at both ends in the width direction Y. In other words, it indicates that items with low severity can be arranged closer to the center of the print head 13, and items with high severity can be arranged closer to the ends. This is because it is required that the center of the print head 13 has higher print quality than the ends. In the following formula, the position of the nozzle 27 at the center of the head module 25 in the width direction Y is 2500.

Severity = SUM (frequency of abnormal nozzle occurrence / | (difference from center of abnormal nozzle occurrence position) |, all nozzles)

The SUM in the formula sign means that the abnormal nozzle occurrence frequency / | (difference from the center of the abnormal nozzle occurrence position) | is added for all nozzles 27. The severity is greater the more frequently abnormalities occur, and the closer the abnormal nozzle 27 is to the center, the greater the severity.

When calculating the specific severity for head modules HM1 and HM4, the values are as follows:

Head module HM1 severity = 2/|2500-2400| = 0.02

Head module HM4 severity = 50/|2500-10|+200/|2500-200|=0.1

The severity of head module HM1 = 0.02 is smaller than the severity tolerance threshold = 0.10. Therefore, it can be determined that the severity is low and print quality can be maintained even in this position. The severity of head module HM4 = 0.1 is greater than the severity tolerance threshold = 0.05. Therefore, it can be determined that the severity is not suitable for use in this position and print quality cannot be maintained in this position. Therefore, in this example, the head module HM1 with low severity is moved toward the center in the width direction Y of the print head 13 where its severity is lower than the severity tolerance threshold, and the head module HM4 with high severity is moved toward the end in the width direction Y of the print head 13 where its severity is lower than the severity tolerance threshold. Specifically, if the positions of head module HM1 and head module HM4 are swapped, this becomes the optimal position.

According to this embodiment, when a malfunction is detected in one of the head modules 25, the control unit 39 determines whether the print quality of the print head 13 can be maintained by swapping the position of the defective head module 25 based on the unique information of each head module 25 and the unique information of the defective head module 25. If it is determined that the print quality can be maintained by swapping the position, the swapping of the position is displayed on the display unit 35. Therefore, by swapping the position of the displayed head module 25 with the defective head module 25, the frequency of replacement with a new head module 25 can be reduced. Therefore, even if a malfunction occurs in a head module 25, the operating costs of the device can be reduced.

<Installation direction>

In the above-described embodiment, the mounting direction of the head module 25 in the transport direction X was not an issue. However, for example, some head modules 25 can be mounted in the "feed direction" in which one side faces downstream in the transport direction X, and in the "counter-feed direction" in which one side faces upstream in the transport direction. When using such a head module 25, it is preferable to adopt the following configuration.

Now, let us refer to Figure 10. Figure 10 shows the configuration for determining the mounting direction as seen from the transport direction.

The head module 25 has a direction determination mark 45 provided on a part of the underside where the nozzle 27 is formed. For example, the direction determination mark 45 indicates the feed direction when it is located on the right side in the width direction Y of the head module 25. On the other hand, for example, the direction determination mark 45 indicates the counter-feed direction when it is located on the left side in the width direction Y of the head module 25. The direction determination mark 45 is photographed by the underside photographing unit 23, and the mounting direction is determined by the data processing unit 33. Note that this determination (mounting direction detection step) is preferably performed before the above-mentioned step S11.

When adopting such a configuration, it is preferable to configure the unique information as shown in Figures 11(a) and (b). Figure 11(a) shows the arrangement of unique information when the mounting direction is -1, and Figure 11(b) shows the arrangement of unique information when the mounting direction is determined to be +1.

For example, if the mounting direction is the reverse feed direction, the mounting direction in the unique information is set to "-1", and if the mounting direction is the feed direction, the mounting direction in the unique information is set to "+1". In this way, the mounting direction of the head module 25 can be detected by reading the unique information. However, as a result of imaging by the bottom surface imaging unit 23, the mounting direction detected by the data processing unit 33 may not match the mounting direction in the unique information 29. For example, as shown in FIG. 11(a), the mounting direction in the unique information of the head memory 29 is "-1" (reverse feed direction). Meanwhile, as a result of imaging by the bottom surface imaging unit 23, the mounting direction is "+1". In this way, when the mounting direction in the unique information differs from the mounting direction indicated by the direction determination mark 45, the unique information is updated.

Specifically, among the unique information, those that have directionality are inverted in the width direction Y, centered on the transport direction X of the web paper WP. As shown in FIG. 11(b), the ejection amount for each nozzle, which is related to the density distribution in FIG. 3, and the nozzle missing frequency for each nozzle, which is related to the abnormal nozzle occurrence frequency in FIG. 3, are swapped left and right with respect to FIG. 11(a).

By detecting the actual mounting direction in this way and updating the unique information, it is possible to make correct decisions based on the unique information according to the actual mounting direction of the head module 25. Therefore, for example, it is possible to accurately make a replacement decision in step S11 described above.

Now, referring to Figure 12, we will explain an example of how each head module 25 is attached to the print head 13. Figure 12 is a schematic diagram that explains the relationship between the attachment direction and the flow path direction.

For example, the print head 13 has a flow path direction for each head module 19 as shown in Figure 12. In this flow path direction, that is, ink is supplied from the left side of the print head 13 to the head modules HM1, HM3, and HM5 on the downstream side in the transport direction X, and ink is supplied from the right side of the print head 13 to the head modules HM2 and HM4 on the upstream side in the transport direction X. In the print head 13 having such a flow path direction, as shown in Figure 12, for example, the head modules HM1, HM3, and HM5 on the downstream side in the transport direction X are mounted in a mounting direction of "+1" in the feed direction. Furthermore, the head modules HM2 and HM4 on the upstream side in the transport direction X are mounted in a mounting direction of "-1" in the counter-feed direction, for example. Therefore, in step S11 described above, when attempting to swap head module HM1 and head module HM4, the mounting directions of head module HM1 and head module HM4 are reversed, so when determining whether or not printing quality can be maintained by swapping them, the head control unit 31 makes the determination taking into account the mounting direction from the data processing unit 33.

In step S11 described above, the replacement of the head modules 25 is considered. In this case, the even-numbered head modules HM2 and HM4 are considered to be replaced, and the odd-numbered head modules HM1, HM3, and HM5 are considered to be replaced. In these considerations, since the mounting directions are the same, the unique information is not inverted and is used as is. Furthermore, when considering the replacement of the even-numbered head modules HM2 and HM4 with the odd-numbered head modules HM1, HM3, and HM5, the unique information is inverted according to the mounting direction as described above. Also, for example, regardless of whether the head modules 25 attached to the print head 13 are even or odd, it may be considered whether the difference in density distribution between adjacent head modules 25 is reduced by reversing the mounting direction.

The mounting direction in FIG. 12 described above is just an example. For example, contrary to FIG. 12, the head modules HM1, HM3, and HM5 on the upstream side of the transport direction X may be mounted in the counter-feed direction "-1", and the head modules HM2 and HM4 on the downstream side in the transport direction X may be mounted in the feed direction "+1". Also, the print head 13 may be configured so that the mounting direction can be determined for each head module 25, regardless of whether it is upstream or downstream in the transport direction X.

The present invention is not limited to the above embodiment, but can be modified as follows:

(1) In the above-described embodiment, the density distribution, the position where abnormal nozzles occur, and the frequency with which abnormal nozzles occur have been described as examples of defects occurring in the head module 25. However, the present invention can also be applied to defects other than these that affect print quality.

(2) In the above-described embodiment, the printing medium has been described using web paper WP as an example. However, the present invention can be applied to any printing medium that can be printed on by an inkjet print head 13. For example, the present invention can be applied to a printing medium made of a plastic film.

(3) In the above-described embodiment, a configuration in which the print head 13 has five head modules 25 was exemplified. However, the present invention is not limited to this configuration. Also, the print head 13 was described using an example in which the head modules 25 are arranged in a staggered manner, but the present invention is not limited to this configuration. For example, the print head 13 may be configured with multiple head modules 25 arranged in a straight line in the width direction Y.

(4) In the above-described embodiment, the mounting direction was determined by the direction determination mark 45 photographed by the bottom surface photographing unit 23. However, the present invention is not limited to such a determination method. For example, when the head module 25 has an asymmetric shape between the upstream side and the downstream side when the width direction Y is used as a reference, specifically, when the bottom surface of the head module 25 has a trapezoidal shape, the mounting direction may be determined according to the length of the upper base and the lower base. Also, instead of using the bottom surface photographing unit 23, a mechanical switch such as a limit switch may be provided on the print head 13 to which the head module 25 is attached, and the switch may be configured to operate only when the mounting direction is in one direction.

(5) In the above-described embodiment, only the inkjet printing device 1 that prints on one side of the web paper WP has been described as an example. However, the present invention is not limited to this configuration. For example, there is a double-sided printing system that is connected to an inkjet printing device 1 for back side printing via an inversion device (not shown) arranged downstream of the inkjet printing device 1. In such a configuration, the control unit 39 may receive unique information of the print head 13 in the inkjet printing device 1 for back side printing as external information, and may replace or exchange the head modules 25, including the print head 13 for back side printing and the print head 13 for front side printing.

As described above, the present invention is suitable for a method for maintaining a print head in an inkjet printing device and an inkjet printing device using the same.

REFERENCE SIGNS LIST 1 ... inkjet printing device 3 ... paper feed section 5 ... printing device 7 ... paper discharge section 9 ... head module station WP ... continuous paper X ... transport direction Y ... width direction 11, 21 ... drive roller 13 ... print head 15 ... transport roller 17 ... drying section 19 ... inspection section 21 ... drive roller 23 ... bottom surface photographing section 25 (HM1 to HM5) ... head module 27 ... nozzle 29 ... head memory 37 ... database 39 ... control section 45 ... direction determination mark

Claims (7)

A method for maintaining a print head in an inkjet printing device having a print head constituted by a plurality of head modules that eject ink onto a print medium to perform printing, comprising the steps of:
detecting that a malfunction has occurred in any of the head modules constituting the print head;
a determination step of determining whether the print quality of the print head can be maintained by replacing the position of the defective head module in the print head based on unique information including the ejection characteristics of each head module constituting the print head excluding the defective head module and the unique information of the defective head module;
a notification step of notifying the user of the change in the arrangement positions when it is determined that the print quality can be maintained by the determination step;
Implemented the following:
A maintenance method for a print head in an inkjet printing device, characterized in that the judgment step determines whether, when the defective head module has caused an ejection abnormality, printing quality can be maintained by rearranging the position of the defective head module on the print head so that the defective head module is positioned at the end of the print head, or whether, when the defective head module has caused a density distribution defect, printing quality can be maintained by rearranging the position of the defective head module on the print head so that the difference in density distribution between adjacent parts of the head modules is within a certain range. A method for maintaining a print head in an inkjet printing device having a print head constituted by a plurality of head modules that eject ink onto a print medium to perform printing, comprising the steps of:
detecting that a malfunction has occurred in any of the head modules constituting the print head;
a determination step of determining whether the print quality of the print head can be maintained by replacing the position of the defective head module in the print head based on unique information including the ejection characteristics of each head module constituting the print head excluding the defective head module and the unique information of the defective head module;
a notification step of notifying the user of the change in the arrangement positions when it is determined that the print quality can be maintained by the determination step;
Implemented the following:
If it is determined in the determination step that the print quality cannot be maintained by replacing the arrangement position of the defective head module in the print head,
A method for maintaining a print head in an inkjet printing device, comprising: accessing a database storing unique information for a plurality of new head modules; searching for a new head module that can maintain printing quality by replacing the defective head module based on the unique information of the defective head module and the unique information of each head module that constitutes the print head excluding the defective head module; and performing an exchange presentation step to present the new head module if the new head module that can maintain printing quality is determined to be a new head module . 3. The method for maintaining a print head in an inkjet printing apparatus according to claim 2 , further comprising the steps of:
A method for maintaining a print head in an inkjet printing device, characterized in that, in addition to the replacement suggestion step, an alternative suggestion step is carried out in which, based on the unique information of the new head module and the unique information of all head modules that make up the print head excluding the defective head module, the printing quality of a simple replacement when the new head module is replaced with the defective head module is compared with the printing quality of various replacements when the arrangement positions of each head module excluding the defective head module are replaced with the new head module, and the one with higher printing quality is also suggested. A method for maintaining a print head in an inkjet printing device having a print head constituted by a plurality of head modules that eject ink onto a print medium to perform printing, comprising the steps of:
detecting that a malfunction has occurred in any of the head modules constituting the print head;
a determination step of determining whether the print quality of the print head can be maintained by replacing the position of the defective head module in the print head based on unique information including the ejection characteristics of each head module constituting the print head excluding the defective head module and the unique information of the defective head module;
a notification step of notifying the user of the change in the arrangement positions when it is determined that the print quality can be maintained by the determination step;
Implemented the following:
When the head module can be attached to the print head in a posture facing either a feed direction in a transport direction of the print medium or a counter-feed direction opposite to the feed direction, the head module has an attachment direction, either the feed direction or the counter-feed direction, in the unique information,
A method for maintaining a print head in an inkjet printing device, characterized in that in the judgment step, if the mounting direction in the unique information of the head module is different from the mounting direction of the head module, the mounting direction of the unique information is updated to the correct direction, and any unique information that has directionality is reversed to a direction perpendicular to the transport direction of the printing medium . 5. The method for maintaining a print head in an inkjet printing apparatus according to claim 4 , further comprising the steps of:
A maintenance method for a print head in an inkjet printing device, comprising the steps of: prior to the determination step, performing an installation direction detection step of detecting the installation direction for each head module constituting the print head. An inkjet printing device having a print head composed of a plurality of head modules that ejects ink onto a printing medium to perform printing,
a transport unit that transports the print medium in a predetermined transport direction;
a control unit that operates the print head to print on the print medium;
a detection unit that detects when a malfunction occurs in any of the head modules that configure the print head;
a head memory provided for each of the head modules, the head memory storing unique information including ejection characteristics;
a determination unit that determines whether the printing quality of the print head can be maintained by determining, as a defective head module, the head module in which the defect has occurred, and by replacing the position of the defective head module in the print head based on the unique information about each head module constituting the print head excluding the defective head module and the unique information about the defective head module;
a notification unit that notifies the user of the change in the arrangement positions when the determination unit determines that the print quality can be maintained;
Equipped with
The inkjet printing device is characterized in that the judgment unit judges whether, when the defective head module has caused an ejection abnormality, printing quality can be maintained by rearranging the position of the defective head module on the print head so that the defective head module is positioned at the end of the print head, or whether, when the defective head module has caused a density distribution defect, printing quality can be maintained by rearranging the position of the defective head module on the print head so that the difference in density distribution between adjacent parts of the head modules is within a certain range . An inkjet printing device having a print head composed of a plurality of head modules that ejects ink onto a printing medium to perform printing,
a transport unit that transports the print medium in a predetermined transport direction;
a control unit that operates the print head to print on the print medium;
a detection unit that detects when a malfunction occurs in any of the head modules that configure the print head;
a head memory provided for each of the head modules, the head memory storing unique information including ejection characteristics;
a determination unit that determines whether the printing quality of the print head can be maintained by determining, as a defective head module, the head module in which the defect has occurred, and by replacing the position of the defective head module in the print head based on the unique information about each head module constituting the print head excluding the defective head module and the unique information about the defective head module;
a notification unit that notifies the user of the change in the arrangement positions when the determination unit determines that the print quality can be maintained;
Equipped with
Further comprising a database storing the unique information regarding a plurality of new head modules;
When the determination unit determines that the print quality cannot be maintained by changing the arrangement position of the defective head module in the print head,
an exchange suggestion unit that accesses the database, searches for a new head module that can maintain print quality by replacing the defective head module based on unique information of the defective head module and unique information of each head module constituting the print head excluding the defective head module, and suggests the new head module when the new head module that can maintain print quality is determined as a new head module.

Images