Inkjet printing

Abstract

An inkjet printer for printing on a printable medium using an inkjet printer head 400 comprising a plurality of nozzles 450. The inkjet printer comprising one or more processors, the one or more proc

Description

Technical Field The disclosure herein relates to a method for printing on a printable medium using an inkjet printer head which comprises a plurality of nozzles. Background Inkjet printing is a type of printing that uses ink to print text and / or graphics on a printable medium such as envelopes or letters. In inkjet printing, ink is forced through nozzles to create minuscule droplets which are precisely arranged to create the text or graphics on the printable medium. One of the challenges in inkjet printing is the clogging of nozzles of the printer head due to ink drying in the nozzles which can adversely affect the delivery of ink droplets to the printable medium. Over time the clogging of nozzles can affect print quality and necessitate costly repairs or replacements in addition to leading to wastage of printable medium. The invention herein aims to solve at least one of the problems associated with current inkjet printing technologies. Summary According to a first aspect of the invention, there is provided a method for printing on a printable medium using an inkjet printer head comprising a plurality of nozzles. The method comprising printing on a first printable portion of a first printable medium using a first group of nozzles from the plurality of nozzles; and printing on a second printable portion of a second printable medium using a second group of nozzles from the plurality of nozzles. The second group of nozzles is different from the first group of nozzles. In this way, the invention addresses the issue of nozzle clogging due to nozzle underuse in inkjet printers. By alternating between different groups of nozzles for printing on various printable media, the invention ensures regular usage of all nozzles, thus reducing the likelihood of nozzles clogging due to infrequent use. Preferably, wherein the first printable portion and the second printable portion are located within corresponding regions of the first printable medium and the second printable medium. Preferably, wherein the corresponding regions are regions for printing addresses, graphics or logos on the printable medium. The regions may be designated for printing addresses, graphics or logos on the printable medium, for example, by a specification set by a postal service. In this way, by alternating between different groups of nozzles even when printing on corresponding regions that typically use the same nozzles in conventional setups, the invention allows the usage of previously underused nozzles which effectively reduces the overall risk of nozzle clogging across the printer head. Preferably, wherein the second group of nozzles comprises no nozzles in common with the first group of nozzles. Preferably, wherein the first and second groups of nozzles are selected based on a predetermined pattern to evenly distribute usage across all nozzles over time. In this way, the invention addresses the issue of nozzle clogging due to nozzle underuse in inkjet printers. By ensuring that all of the nozzles across the first and second groups of nozzles are evenly used, this helps prevent clogging of the nozzles through underuse. Preferably, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a sequential order. Preferably, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a non-sequential order. Preferably, wherein a printing cycle is defined as the process of utilising each nozzle in the inkjet printer head at least once, such that every nozzle is utilised before the printing cycle ends. Preferably, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles is used for printing on an equal number of envelopes within the printing cycle. Preferably, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles consumes approximately the same amount of ink during the printing cycle. Preferably, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles operates for a duration of time that is comparable to the average operational time of all nozzles across the printing cycle. Preferably, wherein the printable medium is an envelope or a letter. According to a second aspect of the invention, there is provided an inkjet printer for printing on a printable medium using an inkjet printer head comprising a plurality of nozzles, the inkjet printer comprising one or more processors, with the one or more processors collectively configured to cause the inkjet printer head to: print on a first printable portion of a first printable medium using a first group of nozzles from the plurality of nozzles; and print on a second printable portion of a second printable medium using a second group of nozzles from the plurality of nozzles. The second group of nozzles is different from the first group of nozzles. Preferably, wherein the first printable portion and the second printable portion are located within corresponding regions of the first printable medium and the second printable medium. Preferably, wherein the corresponding regions are regions for printing addresses, graphics or logos on the printable medium. The regions may be designated for printing addresses, graphics or logos on the printable medium, for example, by a specification set by a postal service. Preferably, wherein the second group of nozzles comprises no nozzles in common with the first group of nozzles. Preferably, wherein the first and second groups of nozzles are selected based on a predetermined pattern to evenly distribute usage across all nozzles over time. Preferably, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a sequential order. Preferably, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a non-sequential order. Preferably, wherein a printing cycle is defined as the process of utilising each nozzle in the inkjet printer head at least once, such that every nozzle is utilised before the printing cycle ends. Preferably, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles is used for printing on an equal number of envelopes within the printing cycle. Preferably, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles consumes approximately the same amount of ink during the printing cycle. Preferably, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles operates for a duration of time that is comparable to the average operational time of all nozzles across the printing cycle. Preferably, wherein the printable medium is an envelope or a letter. According to a third aspect of the invention, there is provided a computer-readable medium comprising instructions which, when executed by a processor, performs the method of any previous method statement. Brief Description of the Drawings The invention shall now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 illustrates examples of printable media; FIG. 2 presents an example of a printer head of an inkjet printer; FIG. 3 illustrates examples of printing defects that can occur due to underused nozzles in an inkjet printer; FIG. 4 illustrates a printer head with a plurality of nozzles according to an embodiment of the invention; FIG. 5 illustrates an example of how the present invention can eliminate or reduce printing Hofor+c: ■ kJ CI CLxLO / FIG. 6 illustrates a printer head with a plurality of nozzles according to a further embodiment of the invention; FIG. 7 illustrates a printer head with a plurality of nozzles according to a further embodiment of the invention; and FIG. 8 shows a flow diagram for illustrating a method for printing on a printable medium using an inkjet printer head comprising a plurality of nozzles. Detailed Description FIG. 1 illustrates examples of printable media, such as envelope 100 and a pre-printed letter 120. Envelope 100 comprises a printable portion 100a, while pre-printed letter 120 comprises a printable portion 120a. Within the context of this specification, a 'printable portion' refers to a pre-defined region of a printable medium—such as an envelope or a preprinted letter—that is specifically designated for the application of textual content (such as addresses), graphics, or logos printed by an inkjet printer, for example, as designated by a specification set by a postal service. When multiple printable media are printed as part of a batch, the printable portion of each printable medium is located in a corresponding region of each printable medium. For example, the printable medium may be a pre-printed letter 120 that is to be sent to a large number of customers of a business and the printable portion is the region in the pre-printed letter 120 where the address of each customer is to be printed (for example, to allow the address to align with a window in an envelope), or the printable medium may be an envelope 100 containing the preprinted letter 120 and the address of each customer is printed on the printable portion 100a of the envelope 100. FIG. 2 shows an example of a printer head 200 of an inkjet printer positioned directly over the printable portion 100a of envelope 100 to facilitate ink deposition on to the printable portion 100a. As shown more clearly in the exploded view 210, the printer head 200 comprises multiple nozzles 250, each designed for depositing ink onto the printable portion 100a. As mentioned in the background section, one of the main challenges with inkjet printing is the clogging of nozzles of the printer head which can affect the delivery of ink droplets to the printable medium. The clogging of nozzles occurs due to specific nozzles being underused relative to other nozzles when printing on the same part of printable media repeatedly. To visualise this problem, consider the nozzles of the printer head to be arranged in lines L1-L16 aligned along the direction in which address lines will be printed in the printable medium. In the example of FIG. 2, the direction of printing on the printable medium is along the X-axis (i.e., the direction in which the printer head 210 and the printable medium move relative to each other). However, the direction of printing on the printable medium can also be along the Y-axis. If a specific address only requires part of the space on the printable portion of a printable medium, only the corresponding nozzles are used. In an address that has more address lines than a typical address that is being printed, the nozzles that are required to print the additional address lines may be found to be clogged as they may not be used often when printing other typical addresses. Furthermore, the nozzles located between the lines on the address will be underused as they may only be used when printing descending characters such as the letters "g", "q" and "y", however, those letters are not printed often enough to prevent clogging of nozzles located between address lines. For example, if the bottom part of some of the descending characters is printed by the nozzles in L3, L8 and L13 then some or all the nozzles in L3, L8 and L13 may be clogged due to repeated underuse. Therefore, when it comes time to print the descending character, the nozzles used to print those characters may be clogged. The use of nozzles in a particular line may vary; therefore, some nozzles in a particular line may become clogged due to infrequent usage, while other nozzles in the same line may not be clogged due to frequent usage. Similarly, if the same graphic or logo is repeatedly printed across multiple printable media, only the nozzles that align with the specific graphic or logo area in the printable portion are used while the remaining nozzles are not used or are underused. This uneven usage can lead to the clogging of those nozzles that are less frequently engaged in the printing process. FIG. 3 presents two examples, 300a and 300b, illustrating examples of printing problems that can occur due to underused nozzles in an inkjet printer. Example 300a shows a text sample where the 'risers' of certain letters are missing. For example, the top of the 'S' in 'Sample' and the top of the 'T' in 'Town' are missing in the third line. This is due to the nozzles aligned over the area where the 'risers' of those letters are to be printed in the printable portion are underused and subsequently dried out, leading to incomplete printing of those characters. Example 300b demonstrates an additional issue with the 'droppers' of certain letters. The bottom of the letter 'p' in 'Sample' is missing in the first two lines. Again, this is a result of the specific nozzles that print those parts of the letters being underused, leading to them drying out and failing to deliver ink when required. Those examples demonstrate the problem of nozzles clogging due to uneven usage in inkjet printers. This issue is a significant challenge in maintaining consistent print quality and efficiency. Over time, it can lead to increased maintenance costs, printer downtime, and ultimately, a less reliable printing process. To overcome the clogging challenge of inkjet printing, the disclosure herein provides a method that involves alternating the use of the plurality of nozzles 250 of the printer head 200 when printing on different / a sequence of printable media and thus mitigating the risk of nozzles clogging by ensuring that nozzles are not underused. FIG. 4 illustrates a printer head 400 with a plurality of nozzles 450 according to a first aspect of the invention. The plurality of nozzles 450 comprise one or more groups of nozzles. In this example, the one or more groups of nozzles are represented by G1-G4. The method described herein has been developed for printing on a first printable portion of a first printable medium using the first group of nozzles, G1 for example, from the plurality of nozzles, 450, and printing on a second printable portion of a second printable medium using the second group of nozzles, G2 for example, wherein the second group of nozzles, G2, is different from the first group of nozzles, Gl. Thus, the method described herein provides a solution to the problem of nozzle clogging due to nozzle underuse by using different nozzles to print on different printable media. The invention described herein enables different groups of nozzles to be used on a printable medium, such as an envelope or a letter, which decreases the likelihood of nozzles getting clogged due to the printer head activating different groups of nozzles. In order to ensure that nozzles are not underused, a concept of a printing cycle is introduced. A printing cycle can be defined as a period where each nozzle in the inkjet printer head 400 is utilised at least once, such that every nozzle is utilised before the printing cycle ends. A predetermined pattern may be used which ensures that each nozzle in the plurality of nozzles 450 consumes approximately the same amount of ink during the printing cycle and / or each nozzle is activated at least once during the printing cycle. The predetermined pattern may also ensure that each nozzle in the plurality of nozzles operates for a comparable duration of time. In this example, the comparable duration of time means that each nozzle's operation time is within 10 % of the average operational time of all nozzles across the printing cycle. FIG. 5 illustrates an example of improved printing according to the invention herein. In this figure, a text sample, represented as 500a shows the same text sample from FIG. 3 being printed multiple times each on a different printable medium, but in slightly different locations in the printable portions of each printable medium. This is achieved by moving the text sample 500a around the printable portion so that the nozzles which would otherwise not be frequently used for printing are utilised more regularly. This method of printing ensures that substantially all of the nozzles are used evenly, thereby reducing the likelihood of any nozzles being underused and subsequently drying out. By ensuring regular usage of substantially all nozzles, the method described herein effectively mitigates the problem of nozzles clogging in inkjet printers, thereby enhancing print quality and reducing maintenance costs associated with nozzles clogging. FIG. 6 illustrates the printer head 400 of FIG. 4. As illustrated in FIG. 6 the groups of nozzles are not limited to a certain order and the first group of nozzles, Gl, and second group of nozzles, G2, may refer to any group of nozzles on the printer head 400. Note in the examples of FIGs. 4 and 6, the different groups of nozzles comprise no nozzles in common. FIG 7. illustrates the printer head 400 of FIG.4. In this example, the first group of nozzles, Gl, and the second group of nozzles, G2, share nozzles in common 720. Therefore, the nozzles in common 720 may be used when printing using the first group of nozzles, Gl, and may also be used when printing using the second group of nozzles, G2. The nozzles in common 720 are not limited to that which is illustrated in FIG.7 and may refer to nozzles in common between any of the one or more groups of nozzles (e.g., G1-G4). Any two adjacent groups of the one or more groups of nozzles (e.g., G1-G4) may share all of their nozzles (i.e. the nozzles in common 720 encompasses all of the nozzles comprised in the first group of nozzles, Gl, and all of the nozzles comprised in the second group of nozzles, G2), which may lead the adjacent groups of nozzles to combine and form a singular group of nozzles. In some examples, the first and second groups of nozzles are selected based on a predetermined pattern to evenly distribute usage across all nozzles over time. The predetermined pattern may comprise rotating through the plurality of nozzles in a sequential order ora non-sequential order. The number of nozzles 250 / 450 shown in FIG. 2 / FIG. 4 / FIG. 6 / FIG. 7 is merely illustrative and it would be understood that a printer head 200 / 400 may comprise more or less nozzles. Furthermore, the number of nozzles in each group of nozzles is not limited to the number of nozzles illustrated in FIG. 2 / FIG. 4 / FIG. 6 / FIG. 7 and the number of nozzles in the one or more groups of nozzles may or may not be equal to each other. For example, a first group of nozzles, Gl for example, may comprise more, less, or an equal number of nozzles compared to a second group of nozzles, G2 for example. FIG. 8 illustrates a method of printing on a printable medium using an inkjet printer head comprising a plurality of nozzles. Step 800 of the method includes printing on a first printable portion of a first printable medium using a first group of nozzles from a plurality of nozzles. Step 850 of the method includes printing on a second printable portion of a second printable medium using a second group of nozzles from the plurality of nozzles; wherein the second group of nozzles is different from the first group of nozzles. The methods disclosed herein may be in the form of instructions on a computer readable storage medium. When the instructions are executed by a processor, the instructions cause the processor to perform the methods disclosed herein. The methods disclosed herein may be provided as a software update for existing hardware. When this update is installed and its instructions are executed by a processor, the software causes the processor to perform the methods disclosed herein. The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation 5 to any one embodiment may be used alone or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A method for printing on a printable medium using an inkjet printer head comprising a plurality of nozzles, the method comprising:printing on a first printable portion of a first printable medium using a first group of nozzles from the plurality of nozzles; andprinting on a second printable portion of a second printable medium using a second group of nozzles from the plurality of nozzles;wherein the second group of nozzles is different from the first group of nozzles.

2. The method of claim 1, wherein the first printable portion and the second printable portion are located within corresponding regions of the first printable medium and the second printable medium.

3. The method of claim 2, wherein the corresponding regions are regions for printing addresses, graphics or logos on the printable medium.

4. The method of any preceding claim, wherein the second group of nozzles comprises no nozzles in common with the first group of nozzles.

5. The method of any preceding claims, wherein the first and second groups of nozzles are selected based on a predetermined pattern to evenly distribute usage across all nozzles over time.

6. The method of claim 5, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a sequential order.

7. The method of either of claims 5 or 6, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a non-sequential order.

8. The method of any of claims 5 to 7, wherein a printing cycle is defined as a process of utilising each nozzle in the inkjet printer head at least once, such that every nozzle is utilised before the printing cycle ends.

9. The method of claim 8, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles is used for printing on an equal number of envelopes within the printing cycle.

10. The method of either of claims 8 or 9, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles consumes approximately the same amount of ink during the printing cycle.

11. The method of any of claims 8-10, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles operates for a duration of time that is comparable to the average operational time of all nozzles across the printing cycle12. The method of any preceding claim, wherein the printable medium is an envelope or a letter.

13. An inkjet printer for printing on a printable medium using an inkjet printer head comprising a plurality of nozzles, the inkjet printer comprising one or more processors, the one or more processors collectively configured to cause the inkjet printer head to:print on a first printable portion of a first printable medium using a first group of nozzles from the plurality of nozzles; andprint on a second printable portion of a second printable medium using a second group of nozzles from the plurality of nozzles;wherein the second group of nozzles is different from the first group of nozzles.

14. The inkjet printer of claim 13, wherein the first printable portion and the second printable portion are located within corresponding regions of the first printable medium and the second printable medium.

15. The inkjet printer of claim 14, wherein the corresponding regions are regions for printing addresses, graphics or logos on the printable medium.

16. The inkjet printer of any of claims 13-15, wherein the second group of nozzles comprises no nozzles in common with the first group of nozzles.

17. The inkjet printer of any of claims 13-16, wherein the first and second groups of nozzles are selected based on a predetermined pattern to evenly distribute usage across all nozzles over time.

18. The inkjet printer of claim 17, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a sequential order.

19. The inkjet printer of either of claims 17 or 18, wherein the predetermined pattern comprises rotating through the plurality of nozzles in a non-sequential order.

20. The inkjet printer of any of claims 17 to 19, wherein a printing cycle is defined as the process of utilising each nozzle in the inkjet printer head at least once, such that every nozzle is utilised before the printing cycle ends21. The inkjet printer of claim 20, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles is used for printing on an equal number of envelopes within the printing cycle.

22. The inkjet printer of either of claims 20 or 21, wherein the predetermined pattern 5 ensures that each nozzle in the plurality of nozzles consumes approximately the same amount of ink during the printing cycle23. The inkjet printer of any of claims 20-22, wherein the predetermined pattern ensures that each nozzle in the plurality of nozzles operates for a duration of time that is comparable to the average operational time of all nozzles across the printing cycle10 24. The inkjet printer of any of claims 13-23, wherein the printable medium is anenvelope or a letter.

25. A computer-readable medium comprising instructions which, when executed by a processor, performs a method of any of claims 1-12.13

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