Printing systems allow for a printing fluid to be deposited onto a print medium. Printing fluid may be deposited onto the print medium via a print head using fluid ejection technologies. These include thermal and piezoelectric ejection technologies. The resolution of the print head may be determined by the number of individual nozzles employed in the print head. Some printing systems, such as large industrial presses, may print at a high throughput with a high image quality For such high throughput printing systems, regular periodic servicing or maintenance may have to be performed in order to maintain a high image quality throughout the duration of a single print job.
Various features of the present disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example only, features of the present disclosure, and wherein:
As discussed certain printing systems, such as large industrial presses, may print at a high throughput with a high image quality. Such systems may use multiple print heads, each of which may have a relatively low resolution. In these cases, due to the demand for high throughput and the relatively low level of nozzle redundancy in each print head, the output quality of a print head may be increasingly sensitive to the malfunctioning of individual nozzles. Nozzles may malfunction for a variety of reasons, including misalignment, blockage, or instability. During the course of a print production job, a continual deterioration of a set of nozzles in a print head may cause the print head to repeatedly reach an image quality threshold, e.g. the threshold being representative of a respective deterioration in image quality. Every time this threshold is reached, a maintenance or servicing operation may be instructed for the print head. Not only does each servicing operation result in printing system downtime, it may often result in the wastage of a substantial amount of printing fluid, such as ink. A “printer” or “printing system” as described herein may comprise any device suitable for performing an additive manufacturing process, which may include, but not be limited to, systems for additive manufacturing in two-dimensions and/or three-dimensions.
Certain examples described herein allow for a nozzle compensation procedure to be performed during an established printing operation. As such printing fluid wastage may be avoided, and disruption to a printing operation may be minimized. In certain examples, information is obtained that relates to a condition of at least a first nozzle of a print head following a first period of an established printing operation performed by the print head. Based on the information obtained, at least a second nozzle of the print head is caused to be operated in place of the first nozzle of the print head during a second period of the established printing operation. In one described case, the information obtained is compared to a plurality of ranges indicative of different nozzle operation states. Responsive to the information obtained indicating a first nozzle operation state, the nozzle compensation procedure is performed. Responsive to the information obtained indicating a second nozzle operation state, the established printing operation is interrupted and a maintenance operation on the print head is instructed. Responsive to the information obtained indicating a third nozzle operation state, the established printing operation is continued. In one described case, the information is obtained repeatedly during the established printing operation.
Certain examples described herein reduce the wastage of printing fluid by reducing the occurrence of servicing operations on a print head. Accordingly, the extent of printer downtime may also be reduced for the same reasons, increasing the productivity rate of the printing system. Additionally, the print head itself may acquire an increased longevity, as it may be enabled to perform a print job for a longer time period without the need for replacement or servicing.
In certain cases, multiple first nozzles in the first nozzle set 130 may be flagged as malfunctioning or poorly functioning and thus be targets for compensation, and may be replaced, within the established printing operation, by multiple second nozzles in the second nozzle set 135. In certain cases, the first nozzle set 130 may be spread across multiple print heads. Likewise the second nozzle set 135 may also be spread over multiple print heads. Print heads may be configured to operate at a relatively low resolution, for example in the range 100-300 dots-per-inch (dpi). In one example, a print head may be configured to operate at 150 dpi. The print head may use thermal and/or piezoelectric actuators to eject printing fluid through the nozzles. The nozzles may also be coupled to one or more printing fluid chambers and/or reservoirs. “Nozzle” as discussed herein may refer to at least one of an ejection mechanism comprising an actuator, an aperture in a print head and any printing fluid chambers.
The printing system 100 may further comprise, according to certain examples, a control system for controlling at least one of the printing mechanism, the nozzle diagnostic mechanism and the nozzle compensator. The nozzle diagnostic mechanism may, in one case, be configured to compare the information obtained relating to a condition of the first nozzle set to a plurality of ranges indicative of different nozzle operation states. In this case, the printing system may be configured to operate the nozzle compensator responsive to the information indicating a first nozzle operation state. The first nozzle operation state may indicate that nozzle compensation is possible without a print quality metric falling below a threshold, e.g. without substantial degradation to a printed image output. In one case, the nozzle diagnostic mechanism may be configured to cause, responsive to the information indicating a second nozzle operation state, the established printing operation to be interrupted. In this case, a signal may be generated relating to the instruction of a maintenance operation on the print head. The second nozzle operation state may indicate that nozzle compensation is not possible without a print quality metric failing below a threshold, e.g. even with nozzle compensation a substantial degradation to a printed image output may occur. In a further case, the nozzle diagnostic mechanism may be configured to cause, responsive to the information indicating a third nozzle operation state, the continuation of the established printing operation. The third nozzle operation state may be associated with a nozzle operation state that results in a print quality metric being above a predefined quality threshold, e.g. a “good” operational state. The continuation of the established printing operation may be performed without the instructing of a maintenance operation on the print head or the operating of the nozzle compensator.
The nozzle diagnostic mechanism may be further configured, according to certain examples, to obtain information relating to a condition of a first nozzle set repeatedly during the established printing operation. In at least one example, the nozzle compensator may be further configured to perform repeatedly both the receiving of said information and the causing, based on the received information, a second nozzle set to be operated in place of the first nozzle set during the established printing operation. As such the first and second nozzle sets may change during each repetition. In one example, the nozzle diagnostic mechanism may be configured to perform repeatedly during the established printing operation the causing of the printing operation to be interrupted and the generating of the signal relating to the instruction of a maintenance operation on the print head.
In one example, the nozzle diagnostic mechanism may be configured to obtain information relating to a condition of at least one nozzle following a first period of an established printing operation based on information obtained during a previous printing operation. The nozzle diagnostic mechanism may, according to one example, be configured to obtain information relating to the first nozzle set, the first nozzle set comprising nozzles that are not suitable for use in a printing operation. The first nozzle set may not be suitable for use in a printing operation due to malfunction, degradation, or otherwise being in a poor operational state, according to various examples. The nozzle diagnostic mechanism may be further configured to obtain information relating to the second nozzle set, the second nozzle set comprising nozzles that are suitable for use in the printing operation. In one case, the nozzle compensator may be configured to perform a nozzle compensation process. The nozzle compensation process may, according to one example, comprise instructing at least one nozzle of the second nozzle set to be operated in place of at least one nozzle of the first nozzle set during an established printing operation. The nozzle diagnostic mechanism may, according to some examples, comprise control electronics to instruct the printing of a calibration pattern onto a print medium. The calibration pattern may comprise information indicative of a condition of at least one nozzle of the print head. In one example, the calibration pattern may comprise a plurality of predetermined positions, where each predetermined position is representative of a particular nozzle of the print head. At each predetermined position, the condition of the corresponding nozzle may be indicated by a mark, line, dot or other symbol which may be deposited by the print head upon the print medium upon instruction by the nozzle diagnostic mechanism. In some examples, the absence of such a mark, line, dot or other symbol at a predetermined position after the printing of the calibration pattern may be indicative of the corresponding nozzle being in a malfunctioning state, or of being in a malfunctioning state during the first period of the established printing operation.
The nozzle diagnostic mechanism may further comprise, according to several examples, a sensor for obtaining information relating to the calibration pattern printed upon the print medium. In one such example the obtained information may comprise an image of the calibration pattern. The sensor may be connectively coupled to the control electronics. In at least one example, the control electronics may be configured to receive the information relating to the calibration pattern obtained by the sensor and to determine, based on the calibration pattern, the condition of the at least one nozzle of the print head. Said determination may, according to one such example, comprise comparing the received information relating to the printed calibration pattern with at least one predefined value. The at least one predefined value may be based on a predefined calibration pattern. In certain other examples, the information obtained by the sensor relating to the printed calibration pattern may be sent to the nozzle compensator, which may be configured to determine the condition of the at least one nozzle based on the calibration pattern. In one example, the nozzle diagnostic mechanism may be further configured to determine the number of malfunctioning nozzles of a print head.
The nozzle diagnostic mechanism may be further configured, according to one example, to obtain information indicating whether at least one nozzle of the print head was redundant during the first period of the established printing operation. In another example, information indicating whether at least one nozzle of the print head was redundant during the first period of the established printing operation may be obtained by the nozzle compensator. In one example, the nozzle diagnostic mechanism may be further configured to determine the number of redundant nozzles of a print head. In another example, the number of redundant nozzles of the print head may be determined by the nozzle compensator.
According to certain examples, the nozzle diagnostic mechanism may be configured to determine whether to instruct a nozzle compensation procedure. In certain other examples, the determining of whether to instruct a nozzle compensation procedure may be performed by the nozzle compensator. The determining whether to instruct a nozzle compensation procedure may be based on, amongst other factors, the number of nozzles of the print head determined to be malfunctioning, and/or the number of nozzles of the print head determined to be redundant.
The nozzle compensator may, according to certain examples, comprise control electronics configured to communicate with the print head. In at least one example, the control electronics may be configured to determine, based on information received from the nozzle diagnostic mechanism indicative of a malfunction of a first nozzle, whether a second nozzle may be suitably operated in place of the first nozzle. Said determination may be based on, amongst many factors, whether the second nozzle was determined to be malfunctioning during the first period of the established printing operation, and whether the second nozzle was determined to be redundant during the first period of the established printing operation. In one example, the nozzle compensator may determine that the second nozzle may be suitably operated in place of the first nozzle if the second nozzle was not malfunctioning and was redundant during the first printing period. The control electronics may, according to certain examples, employ computer program code comprising control instructions for allocating a second nozzle to replace the first nozzle during the second period of the printing operation. In several examples, the control electronics may be configured to generate a signal based on the determination whether the second nozzle may be suitably operated in place of the first nozzle. In one such example, the generated signal may be received by the print head, and may comprise instructions for operating the second nozzle in place of the first nozzle.
The information relating to a condition of a nozzle may, according to various examples, relate to a health condition of the nozzle. The health condition may comprise an indication of whether the nozzle is malfunctioning. The nozzle may be determined to be malfunctioning if it is blocked, clogged, misaligned, flipped, unstable, missing, or is otherwise not functioning within a predefined range of parameters. In one example, the information relates to a health condition of at least a first and a second nozzle of a print head.
In some examples, status information may be obtained prior to the causing of the second nozzle to be operated in place of the first nozzle, said status information indicating that the second nozzle is not presently malfunctioning or was not malfunctioning during the first period of the established printing operation. In other examples, said status information may indicate that the second nozzle is presently redundant or was redundant during the first period of the established printing operation. In another example, said status information may indicate the position of the second nozzle relative to the first nozzle.
In one example, block 210 may be performed by the printing mechanism 110. In another example, block 210 may be performed by a control system of the printing system. Starting the print production operation may, according to one case, comprise receiving a user input via an interface of the printing system, and signaling to the printing mechanism to initiate a printing operation. In another case, a print production operation may start following a print job communicated by a print driver of a computer device. In certain examples, blocks 220 and 230 may be performed by the nozzle diagnostic mechanism 140 and block 240 may be performed by the nozzle compensator 150. In one case the nozzle diagnostic mechanism 140 may also perform block 250. According to various other examples, at least one of blocks 210 to 250 may be performed by a processor connectively coupled to a computer-readable storage medium.
In certain cases, causing the second nozzle to be operated in place of the first nozzle may comprise performing a predefined nozzle compensation procedure. The nozzle compensation procedure may comprise instructing nozzle compensation for the print head. In one example, the nozzle compensation procedure may comprise obtaining information indicative of an allocation of a second nozzle to replace the first nozzle and generating a signal relating to said allocation. The nozzle compensation procedure may further comprise, according to certain examples, receiving the generated signal relating to the allocation of a second nozzle, and causing the second nozzle to be fired and the first nozzle not to be fired during the second period of the established printing operation. Said receiving the generated signal and said causing the second nozzle to be fired and the first nozzle not to be fired may, according to one example, be performed by the print head of the printing system. In this case. “firing” a nozzle may be defined as activating a fluid ejection actuator associated with the nozzle, e.g. applying a voltage via print head control electronics.
The obtaining of status information at block 320 may, according to one example, be performed on a further occasion to confirm the successful outcome of the nozzle compensation procedure performed at block 340. In another example, the obtaining of the status information at block 320 may be performed repeatedly throughout the duration of the print job. This is shown by the dotted line from block 370 to block 320 in
The first nozzle operation state may, according to one example, be based on whether compensation of the first nozzle set by a second nozzle set is determined to be suitable. The second nozzle operation state may, according to one example, be based on a determination that nozzle compensation is unsuitable. Nozzle compensation may be unsuitable due to the first nozzle set not being in a malfunctioning state. In this case, the print job may continue at block 370. Nozzle compensation may also be unsuitable due to a second nozzle set not being allocated to replace the first nozzle set. The second nozzle set not being allocated may occur, according to an example, if the number of malfunctioning nozzles of the print head exceeds a first threshold value. In another example, the second nozzle set not being allocated may occur if the number of redundant nozzles that are not malfunctioning falls below a second threshold value. In a further example, the second nozzle set not being allocated may occur if there is a fault in the nozzle compensator.
In one example, as a consequence of performing the nozzle compensation procedure 490, nozzles which have a relatively high likelihood of failing may be detected and compensated for, resulting in a reduced rate of degradation 470 for the second period of the printing operation. Furthermore, by avoiding a maintenance operation during the printing operation, the offset 415 in nozzle performance due to permanent degradation and maintenance repeatability may be diminished.
As described herein nozzle compensation functions, e.g. control routines that instruct the firing of particular redundant nozzles, may be used to compensate for malfunctioning nozzles. Nozzle compensation may comprise analyzing a health map that maps the health or functionality of a set of nozzles of the print head, and allocating one or more redundant nozzles to replace one or more malfunctioning nozzles, thereby improving the operability of the print head without the need for servicing.
Processor 510 can include a microprocessor, microcontroller, processor module or subsystem, programmable integrated circuit, programmable gate array, or another control or computing device. The computer-readable storage medium 520 can be implemented as one or multiple computer-readable storage media. The computer-readable storage medium 520 includes different forms of memory including semiconductor memory devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable and programmable read-only memories (EPROMs), electrically erasable and programmable read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy and removable disks; other magnetic media including tape; optical media such as compact disks (CDs) or digital video disks (DVDs); or other types of storage devices. The computer-readable instructions 530 can be stored on one computer-readable storage medium, or alternatively, can be stored on multiple computer-readable storage media. The computer-readable storage medium 520 or media can be located either in the printing system 500 or located at a remote site from which computer-readable instructions can be downloaded over a network for execution by the processor 510.
The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.
Number | Date | Country | Kind |
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15161774.3 | Mar 2015 | EP | regional |