WO2024191458A1

WO2024191458A1 - Printhead carriage speed determination

Info

Publication number: WO2024191458A1
Application number: PCT/US2023/064414
Authority: WO
Inventors: Carles CARMONA CALPE; Utpal Kumar Sarkar; David VENDRELL TORNERO
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2023-03-15
Filing date: 2023-03-15
Publication date: 2024-09-19

Abstract

In an example, a method includes receiving an image to be printed by a printer and determining a drop density for a portion of the image, wherein the drop density represents drops to be printed during a pass of a printhead. The method may include determining a carriage speed for a printhead carriage of the printer based on the determined drop density and a highest available drop firing frequency for the printhead, and adjusting a printhead carriage speed setting to the determined carriage speed.

Description

PRINTHEAD CARRIAGE SPEED DETERMINATION

BACKGROUND

Print apparatuses utilise various techniques to disperse print agents such as coloring agent, for example comprising a dye or colorant, coating agents, thermal absorbing agents and the like. Some apparatuses use ‘inkjet’ techniques and such apparatus may comprise a printhead. An example printhead includes a set of nozzles and a mechanism for ejecting a selected agent as a fluid, for example a liquid, through a nozzle. A printhead carriage in the print apparatus may be to receive a printhead and transport the printhead across a print media during printing, so that print agent from the nozzles can be deposited at different positions across the print media.

BRIEF DESCRIPTION OF THE DRAWINGS

[0001] Non-limiting examples will now be described with reference to the accompanying drawings, in which:

[0002] Fig. 1 shows a schematic representation of an example method, which may be a method for setting a carriage speed of a print apparatus;

[0003] Fig. 2 shows a schematic representation of another example method, which may be a method for setting a carriage speed of a print apparatus;

[0004] Fig. 3 shows a schematic representation of an example machine- readable medium in association with a processor; and

[0005] Fig. 4 shows a schematic representation of an example print apparatus.

DETAILED DESCRIPTION

[0006] In some printers, e.g. inkjet printers The speed at which a printhead carriage of the print apparatus moves may influence and constrain the printing speed. The carriage speed needs to be slow enough to ensure there is enough time for the nozzles to deposit the correct amount of drops of print agent in a particular area, without exceeding an upper threshold of the range of available firing frequencies of the nozzles. The highest available frequency of drop firing of the nozzles can be constrained by electronics that control the drop ejection. High frequency drop firing, even when not so high as to be constrained by electronics, can potentially cause damage to a printhead due to overheating. Furthermore, there can be a trade-off between speed and print quality in inkjet printers. For example, high drop firing frequencies may reduce image quality, as drop size can be impacted, and there is a risk some drops will not be ejected at all. Therefore, an upper threshold may be set on the range of available firing frequencies of the nozzles, e.g. as an operating boundary for a printer or printhead, or to define a recommended or predefined maximum, to reduce the risk of image quality issues.

[0007] In some situations, a user would like to print as fast as possible (for example in a draft mode), without risking damage to the printhead. In some examples, a draft mode may correspond to a faster printing mode, which may be e.g. a single-pass printing mode where high accuracy or high quality is less of a priority, but preventing damage to the printer is still a relevant consideration. In some situations, a user would like to print as fast as possible without risking image quality issues.

[0008] Fig. 1 shows an example method 100, which may be a method for setting a carriage speed of a print apparatus, (e.g. an inkjet printer). In some examples, the method 100 may be performed by the print apparatus. In some examples, the method 100 may be performed by an image processing module, which may be part of a print apparatus, or may be in communication with a print apparatus. In some examples, the method 100 may be performed at an electronic device separate from the print apparatus which is to perform processing on a print job prior to sending the print job to the print apparatus.

[0009] At block 102, method 100 comprises receiving an image to be printed by a printer, e.g. an inkjet printer. For example, block 102 comprises receiving image data or print data representing an image to be printed. In some examples, the whole of the image to be printed may be received at the same time, in some examples, the image to be printed may be received and processed in a plurality of sub-sections.

[0010] Block 104 of method 100 comprises determining a drop density for a portion of the image, wherein the drop density represents drops to be printed during a pass of a printhead. For example, block 104 may comprise analysing the image data or print data received in block 102 to determine a drop density. The image is comprised of a plurality of rows of dots. For single-pass printing, each row of the image may correspond to one pass of the printhead over the print media, carried by the carriage. For multi-pass printing, a row of the image may be printed in a plurality of passes, with the printhead being controlled to print a proportion of the dots in the row on each pass.

[0011] In some examples (e.g. for single-pass printing), determining a drop density comprises determining a total number of drops per row. In some examples (e.g. for multi-pass printing) determining a drop density comprises determining a number of drops that will be printed in one pass of the printhead. In some examples, determining a drop density comprises determining a number of drops to be deposited over a particular distance, e.g. determining drops per inch over a whole row of the image or over part of a row. In some examples, where each carriage carries multiple printheads, block 104 comprises determining an associated drop density for each of a plurality of printheads associated with the carriage. The associated drop density may comprise a drop density of drops to be printed by the associated printhead (e.g. drops of a particular type of print agent or color required for the image portion). In some examples, determining the drop density may comprise selecting one of the associated drop densities calculated for each of the plurality of printheads. For example, the drop density associated with the printhead that has a highest drop density for the portion of the image may be selected out of the plurality of drop densities. [0012] In some examples, determining the drop density comprises determining an expected drop density associated with a portion of the image. For example, the drop density may be estimated based on image data. E.g. the drop density may be estimated based on the number of non-blank pixels per row in the image. Determining an expected drop density may comprise determining how many drops are expected to be deposited in one pass for a multi-pass print mode (since in this case the carriage will pass over a particular part of the print media multiple times depositing some of the drops for that row on each pass). For example, this may be estimated or predicted based on image data or print data for a particular multi-pass printing mode.

[0013] In some examples, the portion of the image may be the entire image. In some examples, the portion of the image is less than the entire image, for example a single row, or a plurality of rows of the image. In some examples, the portion of the image is a plurality of rows, also referred to as a frame of the image.

[0014] Block 106 comprises determining a carriage speed for a printhead carriage of the inkjet printer based on the determined drop density and an available drop firing frequency range for a printhead or printheads associated with the carriage. For example, block 106 may comprise determining a carriage speed based on the determined drop density and an upper boundary of the range of available drop firing frequencies, also referred to herein as a highest available drop firing frequency. The carriage speed may also be referred to as a carriage velocity.

[0015] Block 106 may include receiving an available drop firing frequency range associated with the inkjet printer, or with a printhead or printheads associated with the carriage. In some examples, block 106 may comprise receiving a range of available drop firing frequencies. For example, the available range may be a range of drop firing frequencies that are available to the printer or printhead. These may be based, for example on operating boundaries of the printer or on other predefined boundaries that may have been selected in advance for a printer or printhead. In some examples, block 106 may include receiving an upper boundary of an available range, also referred to herein as a highest available drop firing frequency. In some examples, the available drop firing frequency may represent a highest drop firing frequency, also referred to as a highest sustained firing frequency, that the printing apparatus and/or printhead can support without risking damage to the printhead. In some examples, the available drop firing frequency comprises a pre-defined drop firing frequency threshold. For example, the threshold may be set at a level that represents a highest safe drop firing frequency, a level that has been found to reduce the likelihood of print defects, or at any suitable predefined level. For example, the available drop firing frequency may be determined for a particular model of printer or printhead during tests to find safe operating boundaries of the printer or printhead. In some examples, the available drop firing frequency may be associated with a particular print apparatus or model of print apparatus, and may be retrieved e.g. from a look-up table. In other examples, e.g. where the method is performed at a printer, the available drop firing frequency may be stored in the printer. In some examples, where the available drop firing frequency is predefined, block 106 may be performed without explicitly retrieving the available drop firing frequency. For example, block 106 may comprise using a look-up table to look up a suitable carriage speed setting or indicator for a given drop density, wherein the settings or indicators in the table correspond to carriage speeds that are based on the available drop firing frequency and the drop density.

[0016] In some examples, an available drop firing frequency is pre-defined for a particular printer model, printhead, or set of printheads. In some examples, the method may include determining an available drop firing frequency e.g. based on printer properties, printhead properties, and/or print conditions e.g. using local statistics. In some examples, where the carriage is to carry multiple printheads, a shared available drop firing frequency may be defined for all the printheads. In some examples, different printheads may each have an associated available drop firing frequency. In that case, a carriage speed may be calculated for each of the printheads associated with the carriage based on their associated drop densities and drop firing frequencies, and a slowest carriage speed of the calculated carriage speeds may be selected as the determined carriage speed. This ensures that the carriage speed does not cause the drop firing frequency to exceed an available drop firing frequency for any of the printheads.

[0017] In some examples, determining the carriage speed may comprise determining a highest carriage speed setting that will allow printing at the drop density with the highest drop firing frequency.

[0018] Block 108 of method 100 comprises adjusting a printhead carriage speed setting to the determined carriage speed. In some examples, block 108 may comprise controlling a print apparatus to set the carriage speed to the determined value or setting. In some examples, block 108 may comprise outputting a notification or indicator to be received by the print apparatus, to cause a controller of the print apparatus to set the carriage speed to the determined speed. In some examples, block 108 may comprise associating a portion of image data or print data with a particular carriage speed setting.

[0019] In some examples, the method 100 may comprise controlling a printhead carriage of a print apparatus to move at the determined speed during printing of the portion of the image, or of the whole image.

[0020] The method 100 may enable a printhead carriage to be operated at a speed which can be customised for different images, rather than setting the carriage speed at a pre-set speed e.g. based on pre-set printing modes. Setting the carriage at a low pre-set speed may cause the printer to operate too slowly for images that have a low drop density. On the other hand, setting the carriage at a high pre-set speed could risk damage to the printhead, or print quality issues, for images that have a high drop density. Therefore the method 100 may enable the carriage speed to be optimised for each image. [0021] For example, a particular printhead may have an associated highest available drop firing frequency of 12KHz and a particular plot or image to be printed has a drop at every position at a resolution of 600 dpi (dots per inch). Therefore, the image has a drop density of 600 dpi. A carriage speed based on the highest available drop firing frequency of 12KHz and the drop density of 600 dpi may therefore be 20 ips (inches per second). In contrast, where an image or plot has a low drop density (e.g. lines or text), the firing frequency may no longer be a constraining factor so the carriage speed may be increased to its maximum velocity. For example, the carriage speed may be increased from e.g. 20 ips to e.g. 60 ips.

[0022] In some examples, the method may include repeating blocks 104 to 108 for different portions of an image. For example, a first portion of an image may be received, a first drop density may be determined from the first portion of the image and a first carriage speed may be determined based on the first drop density and the highest available drop firing frequency as described above. A carriage speed setting may then be adjusted to a first speed setting. The method may further comprise determining a second drop density for a second portion of the image to be printed, determining a second carriage speed for the printhead carriage of the inkjet printer based on the second drop density and the highest available drop firing frequency for the printhead; and after the first portion of the image has been printed, updating the carriage speed setting of the printhead to the second carriage speed. In some examples the carriage speed setting may be updated for each of a plurality of portions of the image based on a drop density determined for each portion of the image.

[0023] In this way, the printing speed can be changed during printing to enable areas with higher drop density to be printed more slowly to prevent risk of damage to the printhead, or print quality issues. Areas of the image with lower drop density, where there is less risk of the printhead overheating, or print defects occurring, can then be printed more quickly to increase the overall speed of printing the image. [0024] Fig. 2 shows a method 200, which may be a method for setting a carriage speed of an inkjet printer. Method 200 comprises block 102 as described above in relation to Fig.1. Method 200 further comprises, at block 204, determining a drop density associated with each portion of the image. For example, block 204 may comprise determining a drop density associated with each row of the image, or each pass of the printhead carriage. For example, block 204 may comprise, for a single-pass printing mode, determining a drop density for each row of the image.

[0025] Block 206 comprises determining a highest drop density out of the drop densities determined at block 204. That is, block 206 may comprise determining which row of the image has the highest total number of drops, or which image portion has the highest drops per inch, and setting this as the highest drop density. Block 208 comprises determining a carriage speed based on the available drop firing frequency and the highest drop density. Block 201 comprises adjusting the carriage speed setting based on the determined carriage speed.

[0026] Method 200 therefore enables determination of an upper threshold for the carriage speed, wherein the upper threshold is not to be exceeded. The upper threshold is defined based on a row or pass of the image that has a highest drop density. This sets a maximum speed for printing the image without risking damage to the printhead. Once the maximum speed is determined, the whole image may be printed at this maximum speed. This method therefore enables the image to be printed quickly without risking damage to the printheads and/or print defects.

[0027] In some examples, a portion of the image may be analyzed to determine a highest drop density in that portion and then the carriage speed setting may be adjusted for printing that portion of the image. The carriage speed may then be updated for printing a subsequent portion of the image that may have a different highest drop density. In some examples, the highest drop density may be determined by determining which row of the image portion, has the highest drop density. In some examples, the highest drop density may be determined by identifying part of a row that has a highest drop density (e.g. a highest concentration of drops measured in dpi).

[0028] In some examples, method 200 comprises controlling the printer (e.g. an inkjet printer) to print the portion of the image, wherein printing the portion of the image includes controlling the carriage to move at the selected carriage speed.

[0029] In some examples, method 100 or method 200 may be performed in response to receiving an indication that the image is to be printed in a draft mode.

[0030] Fig. 3 shows a machine-readable medium 300 in association with a processor 302. The machine-readable medium 300 comprises instructions 304 to be executed by the processor 302. Instructions 304 may be to, when executed by the processor 302, cause the processor 302 to perform the method of Fig. 1 or Fig. 2.

[0031] The instructions 304 include instructions 306 to cause the processor 302 to receive an image to be printed, wherein the image is to be printed by a printer (e.g. an inkjet printer).

[0032] The instructions 304 include instructions 308 to analyze a plurality of parts of the image to determine a drop density for each of the plurality of parts of the image. In some examples, each part may be one row of the image. In some examples, each part may be part of a row of the image. Each part is to be printed during a pass of a printhead carriage of the inkjet printer. For example, where the part corresponds to a row of the image, printing the part may correspond to one pass of the carriage. Where the part corresponds to part of a row, printing the part may correspond to a section of a pass of the carriage. In some examples, determining the drop density comprises determining the number of drops to be deposited in a pass of the printhead. In some examples, determining the drop density comprises determining an expected drop density, e.g. an expected drop density associated with a row of the image, or with a particular pass of the carriage.

[0033] In some examples, the instructions 304 may comprise instructions to select a highest drop density of the determined drop densities.

[0034] Instructions 304 further include instructions 310 to cause the processor to determine a carriage speed for a printhead carriage of the inkjet printer based on the determined drop density and on an available drop firing frequency range of the printhead. In some examples, instructions 310 may comprise defining or selecting a carriage speed (which may be an upper carriage speed threshold) based on a highest drop density and the highest available drop firing frequency for the printhead.

[0035] Instructions 304 include instructions 312 to cause the processor to output a notification to set a carriage speed of the printhead at the determined carriage speed. For example, the notification may be any output that when received by a print apparatus, causes the print apparatus to automatically set a carriage speed of the print apparatus to the determined carriage speed in response to receiving the output.

[0036] In some examples, the instructions 304 include instructions to determine the carriage speed based on the determined drop density and on the highest available drop firing frequency of the printhead in response to receiving an indication that the image is to be printed in a fast printing mode such as a draft mode.

[0037] In some examples, the instructions 304 include instructions, which when executed by the processor 302, cause the processor 302 to trigger printing of the image by the printer. [0038] In some examples, the machine-readable medium 300 may be part of a print apparatus such as an inkjet printer. In some examples, the machine- readable medium 300 may be external to a print apparatus. For example, the machine-readable medium 300 and the processor 302 may be part of an electronic device in communication with a print apparatus, wherein the electronic device is to transmit the image to be printed to the print apparatus after performing some initial processing on the image in preparation for printing.

[0039] In some examples, the instructions 304 include instructions to determine a first drop density for a first part of the plurality of parts of the image and determine a second drop density for a second part of the plurality of parts of the image. Instructions 304 then comprise instructions to determine a first associated carriage speed based on the first drop density and the highest available drop firing frequency and determine a second associated carriage speed based on the second drop density and the highest available drop firing frequency. The instructions 304 may include instructions to output a notification to set a carriage speed of the printhead at the first associated carriage speed for printing the first part of the image; and output a notification to set the carriage speed of the printhead at the second associated carriage speed for printing the second part of the image.

[0040] In some examples, the instructions may be to determine a drop density and determine a corresponding carriage speed for each of the plurality of parts of the image and to associate the determined carriage speeds with each respective part so that each part is printed with a customized carriage speed.

[0041] Figure 4 shows a schematic representation of a print apparatus 400, which may be an inkjet print apparatus. Print apparatus 400 may be to perform the method 100 or method 200. Print apparatus 400 may include the machine- readable medium 300. Print apparatus 400 may include the processor 302. [0042] Print apparatus 400 comprises a carriage 402, wherein the carriage 402 is for a printhead, comprising nozzles for dispensing print agent, to be mounted on the carriage. The carriage 402 is to transport a printhead back and forth over a print media with a carriage speed so that drops of print agent may be dispensed onto the print media from the printhead in pre-defined locations on the print media. In some examples, the print apparatus 400 may also include the printhead, in some examples the printhead may be a removable or replaceable part that is provided separately from the print apparatus 400.

[0043] Print apparatus 400 also includes a controller 404. In some examples the controller 404 may comprise the machine-readable medium 300 and processor 302 of Fig. 3. The controller 404 is to receive image data for an image to be printed at the print apparatus 400, determine, from the image data, a drop density, e.g. as described in more detail above, and determine, based on the drop density and an available drop firing frequency range of the printhead, a carriage speed for the carriage 402. In some examples, the controller is to determine the carriage speed based on a highest drop density and on an upper boundary of the available drop firing frequency range, also referred to herein as a highest available drop firing frequency. In some examples, the controller 404 may receive a highest available drop firing frequency and/or an available drop firing frequency range from the printhead. In some examples, controller 404 may look up a highest available drop firing frequency or an available drop firing frequency range in a look-up table. For example, the highest available drop firing frequency or available drop firing frequency range may be associated with a printer model or a printhead model in a look-up table which may be stored on the printer or may be stored externally to the printer and accessible to the printer e.g. over wireless communication.

[0044] The controller 404 is also to control the carriage to move at the determined carriage speed while controlling the printhead to print a portion of the image represented by the image data. [0045] In some examples, the controller 404 is to determine a highest drop density by analyzing the image data to determine a printhead pass or a portion of a printhead pass that has a highest expected number of drops per inch.

[0046] The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart. It shall be understood that each flow and/or block in the flow charts and/or block diagrams, as well as combinations of the flows and/or diagrams in the flow charts and/or block diagrams can be realized by machine readable instructions.

[0047] It shall be understood that some blocks in the flow charts can be realized using machine readable instructions, such as any combination of software, hardware, firmware or the like. Such machine-readable instructions may be included on a computer readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon.

[0048] The machine-readable instructions may, for example, be executed by a general purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine-readable instructions. Thus functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit, ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors.

[0049] Such machine-readable instructions may also be stored in a computer readable storage that can guide the computer or other programmable data processing devices to operate in a specific mode. Further, some teachings herein may be implemented in the form of a computer software product, the computer software product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure.

[0050] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims.

[0051] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.

Claims

CLAIMS What is claimed is:

1 . A method comprising: receiving an image to be printed by a printer, determining a drop density for a portion of the image, wherein the drop density represents drops to be printed during a pass of a printhead; determining a carriage speed for a printhead carriage of the printer based on the determined drop density and an available drop firing frequency range for the printhead; and adjusting a printhead carriage speed setting to the determined carriage speed.

2. A method according to claim 1 , comprising: determining a drop density associated with each portion of the image; and determining a highest drop density out of the determined drop densities; wherein determining the carriage speed comprises selecting a carriage speed based on the highest drop density and the highest available drop firing frequency for the printhead; and wherein adjusting a printhead carriage speed setting comprises adjusting the carriage speed setting to correspond to the selected carriage speed.

3. A method according to claim 2, further comprising controlling the printer to print the portion of the image while controlling the carriage to move at the selected carriage speed.

4. A method according to claim 1 , wherein determining the drop density comprises determining the number of drops to be deposited in a pass of the printhead.

5. A method according to claim 1 , wherein determining the drop density comprises determining an expected drop density associated with a portion of the image based on image data.

6. A method according to claim 1 , wherein the drop density comprises a first drop density, the portion of the image comprises a first portion of the image, and the carriage speed comprises a first carriage speed, the method further comprising: determining a second drop density for a second portion of the image to be printed; determining a second carriage speed for the printhead carriage of the printer based on the second drop density and the highest available drop firing frequency for the printhead; and after the first portion of the image has been printed, updating the carriage speed setting of the printhead to the second carriage speed.

7. A machine-readable medium comprising instructions which, when executed by a processor, cause the processor to: receive an image to be printed by a printer; analyze a plurality of parts of the image to determine a drop density for each part; determine a carriage speed for a printhead carriage of the printer based on the determined drop density and an available drop firing frequency range of the printhead; output a notification to set a printhead carriage speed at the determined carriage speed.

8. A machine-readable medium according to claim 7, further comprising instructions, which when executed by the processor cause the processor to: determine the carriage speed based on the determined drop density and on the available drop firing frequency range of the printhead in response to receiving an indication that the image is to be printed in a fast printing mode.

9. A machine-readable medium according to claim 7, further comprising instructions, which when executed by the processor cause the processor to: select a highest drop density of the determined drop densities; wherein determining the carriage speed comprises defining a carriage speed based on the highest drop density and the highest available drop firing frequency for the printhead.

10. A machine-readable medium according to claim 7, further comprising instructions, which when executed by the processor cause the processor to trigger printing of the image by the printer.

11. A machine-readable medium according to claim 7, wherein determining the drop density comprises determining the number of drops to be deposited in a pass of the printhead.

12. A machine-readable medium according to claim 7, wherein determining the drop density comprises determining an expected drop density associated with a row of the image.

13. A machine-readable medium according to claim 7, comprising instructions to determine a first drop density for a first part of the plurality of parts of the image; determine a second drop density for a second part of the plurality of parts of the image; determine a first carriage speed based on the first drop density and the available drop firing frequency range; determine a second carriage speed based on the second drop density and the available drop firing frequency range; output a notification to set a carriage speed of the printhead at the first carriage speed for printing the first part of the image; and output a notification to set the carriage speed of the printhead at the second carriage speed for printing the second part of the image.

14. A print apparatus comprising: a carriage, wherein the carriage is for a printhead, comprising nozzles for dispensing a print agent, to be mounted on the carriage; and a controller; wherein the controller is to: receive image data for an image to be printed at the print apparatus; determine, from the image data, a drop density; determine, based on the drop density and an available drop firing frequency range of the printhead, a carriage speed for the carriage. control the carriage to move at the determined carriage speed while controlling the printhead to print a portion of the image represented by the image data.

15. A print apparatus according to claim 14, wherein the controller is to determine the carriage speed based on a highest available drop firing frequency of the printhead and a highest drop density, wherein determining the highest drop density comprises analyzing the image data to determine a printhead pass or a portion of a printhead pass that has a highest expected number of drops per inch.