Patent Publication Number: US-2022212478-A1

Title: Supply and Mixing Cartridges

Description:
RELATED APPLICATIONS 
     This patent arises from a continuation of U.S. application Ser. No. 16/765,710 (now U.S. Pat. No. 11,292,266), titled Supply and Mixing Cartridges,” filed May 20, 2020, which is a 35 U.S.C. 371 National Stage Application of PCT/US2019/052227, titled “Supply and Mixing Cartridges,” filed Sep. 20, 2019, both of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     Most types of printing apparatus are equipped with replaceable printing material cartridges that hold printing material for the printing process. Such printing material cartridges may include toner cartridges that contain laser printer toner, ink cartridges that contain different types of ink, ribbon cartridges that include inked ribbons, and 3D build material cartridges that contain build material for 3D printers. Ink and other fluid containing cartridges may include materials that require regular recirculation or mixing of the ink in order to avoid precipitating heavy particles which may block the printing apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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 features of the present disclosure, and wherein: 
         FIG. 1  is a schematic illustration of a printing apparatus and supply and mixing cartridges according to an example; 
         FIG. 2  is a schematic illustration of a supply cartridge according to an example; 
         FIG. 3  is a schematic illustration of a mixing cartridge according to an example; 
         FIG. 4  is a flow chart showing a method of operating a printing apparatus according to an example; 
         FIG. 5  is a user interface display according to an example; 
         FIG. 6  is a flow chart showing a method of operating a printing apparatus according to another example; 
         FIGS. 7A-7D  are schematic illustrations of a printing apparatus and supply and mixing cartridges according to another example at different stages of a circulation process; and 
         FIG. 8  is a method of operating a printing apparatus according to another example. 
     
    
    
     DETAILED DESCRIPTION 
     Printing material cartridges, such as those used for an ink jet printing apparatus, may contain a printing fluid which may be applied to a print medium by the printing apparatus. The term “printing fluid” includes all fluids that may be deposited on a print medium from a cartridge and includes fluids such as ink, toner, varnish, gloss, etc. Printing material cartridges may also contain other material for use in printing processes including build material, heat absorbing or reducing agents, and colorants for 3D printing. For ease of explanation, an example of ink is used in the description herein; however, this should not be seen as limiting. An ink may be oil or water based with one or more colorants, e.g. inks may be supplied as cyan, magenta, yellow and/or black inks. 
     A printing material cartridge may comprise a reservoir or printing ink container for storing the ink, as well as an integrated circuit having memory and a processor to perform identification, authentication, and other processes such as retrieving parameters related to the ink which may be used by the printing apparatus. The integrated circuit or smart-chip is protected using memory encryption and limited logic operations of the processor to ensure that the cartridge may only be used with the printing apparatus in an approved predetermined manner. For example, the printing apparatus may only use the cartridge when it contains a predetermined memory setting that is not configurable by an external process, such as a code that may be verified by the printing apparatus. An example mechanism for secure interaction between the integrated circuit of the cartridge and the printing apparatus is described in PCT published patent document WO2016/068990. 
     The printing apparatus may retrieve information about the ink supplied by the cartridge to ensure the cartridge has been installed correctly, is supported by the printing apparatus, or allows the printing apparatus to utilize appropriate color mapping or other processes dependent on characteristics of the ink such as color and chemical composition. The cartridge also comprises an interface containing electrical and fluid connections for interfacing with the printing apparatus. The cartridge is removable from the printing apparatus such as an inkjet printer, so that once the supply of ink is depleted, the cartridge may be replaced with a new cartridge having a full supply of ink. 
     Certain types of ink may contain heavy particles such as titanium dioxide (TiO 2 ) in white ink. Over time these particles may precipitate out of the liquid ink and fall to the lowest level of their container, conduit or local volume. These particles may cause blockages or other issues such as reduced quality image reproduction by the printing apparatus and therefore the printing apparatus may implement recirculation processes to regularly move the ink from one part of the printing apparatus to another in order to avoid precipitation so that the particles remain fully dissolved in the ink. Different types of ink containing different particles or different concentrations of the same particles may require different recirculation processes. Recirculation may also be used to address issues such as ink surface oxidation. Oxidation of ink at the surface is reduced by changing the ink at the surface using recirculation and thus reducing the air exposure duration of any given volume of ink. Recirculation may also be used to address other issues. 
     Using the incorrect recirculation process for an ink may result in poor image reproduction by the printing apparatus due to some precipitation of heavy particles, and may result in blockage due to insufficient mixing of the ink. The recirculation process appropriate for the ink contained in the cartridge may be preinstalled in the printing apparatus memory or added later using a firmware update, or the process may be downloaded manually by a user of the printing apparatus. However, it is not always possible to ensure that the correct recirculation process is used as this may depend on a user correctly identifying the ink in the cartridge or the process being available in the memory of the printing apparatus. 
     Some cartridges containing inks requiring recirculation may be provided with both a supply reservoir and a mixing reservoir which allows the printing apparatus to move the ink between the reservoirs on a regular basis in order to avoid precipitation of heavy particles. However, when the ink supply is depleted and the cartridge is replaced, both the supply reservoir and the mixing reservoir must be replaced as the cartridge is provided as a unitary product. Typically, the ink supply must be replenished more regularly than the mixing reservoir needs to be replaced as the mixing reservoir may only be replaced at the end of its life whereas the supply reservoir may be replaced upon depletion of ink supply. Therefore, replacing such cartridges is relatively expensive and environmentally unfriendly. 
       FIG. 1  illustrates a printing apparatus  100  including two removable cartridges  110  and  120 . The printing apparatus comprises one or more print heads  130 , one or more transport components such as pumps  145  and valves  140 , one or more pressure sensors  150  and pipes or ink conduits  135  connecting the various parts. The printing apparatus may in some examples also comprise an intermediate ink storage tank  147 . The printing apparatus also comprises a controller  155  for controlling the various parts of the apparatus and includes a processor  157  and memory  158 . A user interface  160  provides printing apparatus status information to a user and may allow a user to control some functions. The user interface may include a display and input controls, for example a keypad or a touchscreen. The printhead  130  deposits ink drops onto a print medium and may be controlled to move across the print medium and deposit a controlled number of drops of ink at predetermined locations in order to preproduce an image. 
     The cartridges  110 ,  120  removably couple to a coupling interface  160  which provides fluid communication with other parts of the printing apparatus  100  as well as electrical connection with the controller  155 . Each cartridge  110 ,  120  comprises an ink reservoir  115 ,  125  and an integrated circuit or smart-chip  112 ,  122  including protected memory. One of the cartridges is a supply cartridge  110  which is initially provided with a full reservoir  115  containing ink for use in printing by the printing apparatus and may be replaced when more ink is required. The other cartridge is a mixing cartridge  120  and is initially provided with an empty reservoir  125  and is independently replaceable of the supply cartridge  110 , for example after a predetermined number of uses. The mixing cartridge  120  is used as a reservoir to facilitate ink recirculation in which ink is regularly moved around the printing apparatus to ensure the ink is mixed often enough in order to avoid precipitation of heavy particles. The controller  155  controls the pumps  145  and valves  140  in order to move the ink from the supply cartridge reservoir  115  to the mixing cartridge reservoir  125 , the intermediate tank  147 , and/or the printhead  130 . This movement of ink is typically performed in repeated cycles known as recirculation events, where the movements are dependent on the ink. For example, some inks may need mixing more frequently than others. 
     The cartridge integrated circuits  112 ,  122  may be used to store data related to the ink, for example an identifier that can be used to determine an appropriate recirculation process, an authentication code for ensuring that only approved cartridges may be used with the printing apparatus, characteristics or other data related to the ink in order assist with accurate color reproduction by the printing apparatus. Integrated circuits  112  and  122  for a supply cartridge  110  and a mixing cartridge  120  and according to an example are shown in more detail in  FIGS. 2 and 3  respectively. 
     The integrated circuit  112  for the supply cartridge  110  includes a processor  213 , memory  217  and an interface  215  for connecting with the electrical part of the coupling interface  160 . The processor  213  may be configured to provide limited functionality or may be instructed by the controller  155  of the printing apparatus, for example as an I2C slave. The memory  217  may contain protected fields that are not re-writable, or may only be writable in a limited way for example as a counter only writable in one direction (increasing or decreasing). Some of the fields may also be encrypted so that they can only be read with the correct key to ensure that some information is only available to approved printing apparatus. In an example the memory  217  includes a supply cartridge identifier  230 , a printing material counter  232 , a reservoir printing material level parameter  234 , a removal protection parameter  236 , a paired mixing cartridge identifier  250 , recirculation process instructions  255 , a printing material characteristics parameter  240 , and secret key and authentication instructions for processor  242 . Many of these data fields will be encrypted and otherwise protected to ensure their integrity. 
     The supply cartridge identifier  230  is a read only field containing a unique identifier for the cartridge. This may be used with the paired mixing cartridge identifier  250  to pair a supply cartridge and a mixing cartridge so that once paired they may only be used together. When the supply cartridge  110  is first used with the printing apparatus, the printing apparatus reads a mixing cartridge identifier from an installed mixing cartridge and writes this to the paired mixing cartridge identifier field  250  of the supply cartridge memory  217 . The printing apparatus may be configured to only use the supply cartridge  110  when this field  250  matches a mixing cartridge identifier stored on the paired mixing cartridge  120 . The supply cartridge identifier  230  may also be written to a corresponding paired supply cartridge identifier field  350  on the mixing cartridge as described in more detail below. This ensures that the supply and mixing cartridges are paired to each other to ensure correct operation of the system including for example avoiding mixing of incompatible inks. The printing apparatus may ensure that ink characteristics data stored on each cartridge are compatible, for example that only supply cartridges having the same ink as previously used in the mixing cartridge are paired. By ensuring that the supply cartridge and mixing cartridge only work together, printing system coherence is maintained. For example, only supply and mixing cartridges using the same ink are used together, the levels of the system ink and the ink in each reservoir  115 ,  125  are properly maintained and the use of counterfeit cartridges is avoided. Were a different supply cartridge to be installed with a different ink to that previously mixed in the mixing cartridge, the integrity of the color rendered by the ink would be reduced and mixing of these different inks may lead to other issues such as precipitation of heaving particles and blockage of the printing apparatus. This use of paired identifiers also helps to defeat the use of counterfeit cartridges which do not provide for storing of paired identifiers. 
     The printing material counter  232  is a non-resettable one-directional counter which is re-writable only to decrease (or increase) its value and is indicative of the total level or amount of ink in the printing apparatus  100 , including the supply cartridge  110  and the mixing cartridge  120 . This total system ink counter is initially at a maximum when the supply cartridge is first installed and reduces as the ink is used for printing. The counter may be updated by the printing apparatus, for example when monitoring the number of drops of ink used in a print job. The counter is not changed when the ink is moved as part of a recirculation process, for example from the supply cartridge to the mixing cartridge, but only when the ink is consumed by printing so that the total or system ink is reduced. 
     The reservoir printing material level parameter  234  is indicative of the amount of printing material in the reservoir  115  and is a rewritable field that may be updated by the printing apparatus, based for example on sensors in the reservoir, flowmeters in the printing apparatus, or estimated based on recirculation events. The level of ink in the reservoir  115  may go up as well as down, for example when ink is transferred from the mixing cartridge back to the supply cartridge as part of a recirculation process. 
     The removal protection parameter  236  may be a resettable bit that is used to indicate whether the supply cartridge  110  may be removed from the printing apparatus  100 . It may also be used to indicate whether the supply cartridge can be accepted upon installation. The removal protection parameter or bit may be set when not all of the ink in the printing apparatus is stored in the supply cartridge reservoir  115 . In other words, there is still ink in the mixing cartridge  120 . The removal protection bit may be unset when all system ink is contained in the supply cartridge. Whether or not the supply cartridge is removable may be indicated by the user interface  160 , and a user interface control may allow a user to instruct the printing apparatus to move all ink to the supply cartridge so that it may be replaced. 
     By ensuring that all of the ink is returned to the supply cartridge before removal and replacement with a new supply cartridge, the maximum level of ink in the printing apparatus is not exceeded. For example if ink is retained in the mixing cartridge and a new supply cartridge is installed, the total system level of ink may be too great to allow for recirculation, thereby resulting in precipitation of particles and other issues such as inaccurate monitoring of total system ink levels leading to inaccurate indications of cartridge replacement requirements for example. If the supply cartridge  110  is removed anyway, even with the removal protection parameter indicating that it should not be, this bit will remain set so that the supply cartridge will not be accepted by another printing apparatus. The printing apparatus from which the supply cartridge was removed may need to perform some additional process before accepting any new supply cartridges, for example the mixing cartridge may need to be replaced with an empty one in order to ensure that the maximum level of ink in the printing apparatus is that provided with a new supply cartridge. 
     The printing material characteristics parameter  240  may contain information about the ink in the reservoir  115 , for example it&#39;s color, chemical composition such as pigments used and their concentration compared with a carrier, the use and amount or concentration of dispersants, the use and amount or concentration of agents such as titanium dioxide, the use and amount or concentration of latex binders. Other information may include ink type or identifier, volume, manufacturing batch and other information. The field  242  containing secret key and authentication instructions for processor  213  is used by the processor to access the protected memory  217 . The memory  217  also comprises recirculation process instructions  255  which may be used by the printing apparatus to perform recirculation processes relevant to the ink provided in the reservoir  115 . 
     The integrated circuit  122  for the mixing cartridge  110  includes a processor  313 , memory  317  and an interface  315  for connecting with the electrical part of the coupling interface  160 . The processor  313  may be configured to provide limited functionality or may be instructed by the controller  155  of the printing apparatus, for example as an I2C slave. The memory  317  may contain protected fields that are not re-writable, or may only be writable in a limited way for example as a counter only writable in one direction (increasing or decreasing). Some of the fields may also be encrypted so that they can only be read with the correct key to ensure that some information is only available to approved printing apparatus. In an example the memory  317  includes a mixing cartridge identifier  330 , a reservoir printing material level parameter  334 , a removal protection parameter  336 , a paired mixing cartridge identifier  350 , a recirculation cycle counter  335 , a maximum recirculation cycle parameter  337 , a printing material characteristics parameter  340 , and secret key and authentication instructions for processor  342 . Many of these data fields will be encrypted and otherwise protected to ensure their integrity 
     The mixing cartridge identifier  330  is a read only field containing a unique identifier for the cartridge. This may be used with the paired supply cartridge identifier  350  to pair a supply cartridge and a mixing cartridge so that once paired they may only be used together. When the mixing cartridge  120  is first used with the printing apparatus, the printing apparatus reads the mixing cartridge identifier  330  and writes this to the paired mixing cartridge identifier field  250  of the supply cartridge memory. Similarly, the printing apparatus reads a supply cartridge identifier from an installed supply cartridge and writes this to the paired supply cartridge identifier field  350  of the mixing cartridge memory  317 . The printing apparatus may be configured to only use the mixing cartridge  120  when this field  350  matches a supply cartridge identifier stored on the paired supply cartridge  120 . The printing apparatus may ensure that ink characteristics data stored on each cartridge are compatible, for example that only supply cartridges having the same ink as previously used in the mixing cartridge are paired. By ensuring that the supply cartridge and mixing cartridge only work together, printing system coherence is maintained. For example, only supply and mixing cartridges using the same ink are used together, the levels of the system ink and the ink in each reservoir  115 ,  125  are properly maintained and the use of counterfeit cartridges is avoided. Once a supply cartridge is depleted, the paired supply cartridge identifier may be erased so that a new supply cartridge can be installed, and its identifier written to the paired supply cartridge identifier field  350  so that the mixing cartridge and the new supply cartridge are now paired. In another example, the pairing of the supply and mixing cartridges may only occur when a recirculation process is ongoing and the supply and/or mixing cartridges may be removed and installed in other printing apparatus when the ink is fully contained in the supply cartridge. 
     The recirculation cycle counter  335  may be a non-resettable one-directional counter or field that stores the number of recirculation cycles or events experienced by the mixing cartridge  120 . The counter  335  may be updated by the printing apparatus as recirculation cycles are performed, for example one cycle of moving the ink from the supply cartridge to the mixing cartridge and back to the supply cartridge. The maximum recirculation cycle parameter  337  is a read-only field that stores the maximum number of recirculation events that define the useable lifetime of the mixing cartridge  120 . The value of this parameter may be dependent on the materials used to construct the mixing cartridge. When the value of the recirculation cycle counter  335  equals (or is greater than) the value of the maximum recirculation cycle parameter  337 , the mixing cartridge is deemed unusable and can be replaced. 
     The reservoir printing material level parameter  334  for the mixing cartridge  120  is indicative of the amount of printing material in the reservoir  125  and is a rewritable field that may be updated by the printing apparatus, based for example on sensors in the reservoir, flowmeters in the printing apparatus, or estimated based on recirculation events. The level of ink in the reservoir  125  will vary depending on recirculation processes as ink is transferred to and from the mixing cartridge  120 . 
     A removal protection parameter  336  may also be used in the mixing cartridge. The removal protection parameter may be a resettable bit that is used to indicate whether the mixing cartridge  110  may be removed from the printing apparatus  100 . It may also be used to indicate whether the mixing cartridge can be accepted upon installation. The removal protection parameter or bit may be set when there is ink in the mixing cartridge reservoir  125 . The removal protection bit  334  for the mixing cartridge may be unset when there is no ink in the mixing cartridge. Whether or not the supply cartridge is removable may be indicated by the user interface  160 , and a user interface control may allow a user to instruct the printing apparatus to move all ink to the supply cartridge so that the mixing cartridge may be replaced. 
     The printing apparatus  100  may also store the cartridges identifiers  230  and  330  in memory  158  when setting the corresponding removal protection parameter  236  and  336  in the supply and mixing cartridge memories  217  and  317 . This may allow the printing apparatus  100  to accept cartridges having their removal protection parameter  236  or  336  set when their cartridge identifier  230  or  330  matches that stored in the printing apparatus memory  158 . This arrangement allows a cartridge  110  and/or  120  to be tied to a single printing apparatus  100  using the removal protection bit  236  or  336  stored on the cartridge memory  217 ,  317  and the cartridge identifier  230 ,  330  stored on the printer apparatus memory  158 . For example even if the cartridge is removed with the removal protection bit set, the printing apparatus may be configured to accept it if its cartridge identifier  230 ,  330  is stored on the printing apparatus memory  158 . 
     The printing material characteristics parameter  340  may contain information about the ink that the reservoir  125  may accept, for example it&#39;s color, chemical composition, type or identifier, volume, manufacturing batch and other information. The field  342  containing secret key and authentication instructions for processor  313  is used by the processor to access the protected memory  317 . 
       FIG. 4  illustrates a method  400  of operating a printing apparatus and may be implemented by the controller  155  of the printing apparatus of  FIG. 1  and the integrated circuits and fields in the supply and mixing cartridges  110 ,  120  of  FIGS. 2 and 3 . The method  400  may be performed to control recirculation of certain inks as well as to control use of separately removable supply and mixing cartridges. At block  405 , the method  400  comprises retrieving data from the supply and mixing cartridges. The data may include ink characteristics parameters  240 ,  340 , removal protection parameters  236 ,  336 , cartridge identifiers  230 ,  330  and paired cartridge identifiers  250 ,  350 , system ink counter  232 , reservoir levels  234 ,  334 , recirculation cycles counter  335  and maximum recirculation cycles  337 . 
     At block  410 , the method  400  determines whether this data allows operation of the printing apparatus to proceed. For example if the cartridge identifiers  230 ,  330  are not legitimate, if the removal protection bits  236 ,  336  are set, the paired cartridge identifier fields  250 ,  350  do not match the corresponding cartridge identifier fields  330 ,  230 , or the recirculation cycle counter value  335  is not less than the value in the maximum recirculation cycles field  337 , then the cartridges may be rejected by the printing apparatus  100 . In this case the method  400  may move to block  415  where an error message is displayed to a user on the user interface  160 . A more detailed explanation of use of the paired cartridge identifiers  250 ,  350  is described in more detail below with respect to  FIG. 8 . If the data from the cartridges  110 ,  120  is determined to allow operation of the cartridges with the printing apparatus, the method moves to block  420 . Otherwise the method moves to an error state  415  which may result in a user notification. 
     At block  420 , the method  400  operates the printing apparatus  100  by controlling pumps  145  and values  140  to move ink between different parts of the printing apparatus. For example ink may be moved from the supply cartridge reservoir  115  to the intermediate tank  147  and/or to the mixing cartridge reservoir  125  in order to mix the ink to avoid precipitation of heaving particles. The ink may then be moved back to the supply cartridge reservoir  115  in order to complete a recirculation cycle. The ink may also be moved from the supply cartridge or the mixing cartridge to the printhead to enable printing of an image onto a printing medium. 
     At block  425 , after each ink moving operation, the method updates the data fields in the cartridges  110 ,  120 . For example, the reservoir printing material level parameters  234 ,  334  are updated as ink moves into and out of these storage volumes. Similarly, the printing material counter  232  is updated as the printhead expels ink, thereby reducing the total ink in the system. The removal protection parameter(s)  236 ,  336  are set when not all of the system ink is contained in the supply cartridge reservoir  115 . This may be implemented by comparing the printing material counter  232  with the reservoir printing material level parameter  234  of the supply cartridge—if the former is larger than the later this indicates that some of the total system ink is contained in other parts of the printing apparatus, for example in the mixing cartridge. If the ink movement completes a recirculation cycle (eg moving ink back to the supply cartridge), the recirculation cycle counter  335  in the mixing cartridge is updated. 
     At block  430 , the method  400  determines whether the system ink is low, for example by checking if the value of the printing material counter  232  is below a threshold. If this is not the case, the method moves to block  435  and determines whether the recirculation cycle counter  335  has reached its maximum threshold, the value stored in the maximum recirculation cycles field  337 . If this is not the case, the method returns to the next printing apparatus operation at block  420 . 
     If the total or system ink is low, the method moves to block  440  where the ink in the printing apparatus is moved to the supply cartridge reservoir  115 . At block  445 , the removal protection parameter  236  is unset which indicates that the supply cartridge may be replaced by a user at block  450 . The method then returns to block  405 . If the recirculation cycle counter  335  has reached its maximum threshold, the method  400  again moves to block  440  to ensure that any ink in the printing apparatus is moved to the supply cartridge  110 . If a removal protection parameter  336  is used in the mixing cartridge  120 , this may be unset at block  445  which indicates that the mixing cartridge may be replaced by a user at block  450 . The method then returns to block  405 . 
     Referring to  FIG. 5 , a display for the user interface  160  is shown. This includes a window  510  for a supply cartridge  110  and a window  520  for a mixing cartridge  120 . The supply cartridge window includes an icon  512  indicating the total ink within the printing apparatus—in this case indicating that the total ink is at approximately 75% capacity. This icon corresponds to the printing material counter  232 . A second icon  514  indicates the level of ink within the supply cartridge reservoir  115 —in this case approximately half full and not all system ink is contained in the reservoir  115 . This icon corresponds to the reservoir printing material level parameter  234  of the supply cartridge. A third icon  516  indicates whether the supply cartridge  110  can be removed, for example to replace with a new supply cartridge with full reservoir  115 . This icon corresponds with the removal protection parameter  236  of the supply cartridge and may include a “don&#39;t remove” warning indicator when not all of the system ink is contained in the supply cartridge as is the situation shown. The mixing cartridge window  520  includes an icon  524  indicating the level of ink within the mixing cartridge reservoir  125 —in this case approximately one quarter full. This icon corresponds to the reservoir printing material level parameter  334  of the mixing cartridge. Another icon  526  indicates whether the mixing cartridge  110  can be removed, for example to replace with a new mixing cartridge. This icon corresponds with the removal protection parameter  336  of the mixing cartridge (if used) and may include a “don&#39;t remove” warning indicator when not all of the system ink is contained in the supply cartridge (or when there is some ink in the mixing cartridge reservoir  125 ) as in the situation shown. 
       FIG. 8  illustrates a method  800  of operating a printing apparatus and may be implemented by the controller  155  of the printing apparatus of  FIG. 1  and the integrated circuits and fields in the supply and printing cartridges  110 ,  120  of  FIGS. 2 and 3 . The method  800  may be performed to pair a supply cartridge with a particular mixing cartridge in order to prevent improper operation of the printing apparatus should one of the cartridges be replaced with a different type or a counterfeit cartridge which may not include some or all of the previously described fields used to enable the above described operation. Inaccurate or missing fields may result in incorrect operation of the printer, poor quality printing and possible damage. For example, as described above the printing apparatus tracks the total ink in the system as well as levels of ink in each of the reservoirs  115 ,  125  by updating data  232 ,  234 ,  334  securely stored in the memory  217 ,  317  of the cartridges  110 ,  120 . If a different cartridge is incorrectly installed, the total ink level may be incorrect leading to poor operation of the printing apparatus and possibly damage. 
     At block  805  the method  800  retrieves cartridge identifiers  230 ,  330  from the supply and mixing cartridges  110 ,  120  and if available the paired cartridge identifiers  250 ,  350 . At block  810  the method  800  determines if the paired cartridge identifiers  250 ,  350  from either cartridge are empty. This may occur if the cartridge  110  or  120  has been newly installed. In this case, the method moves to block  820  where the cartridge identifier  230  or  330  is written to the paired cartridge identifier field  350  or  250  of the other cartridge. For example, the cartridge identifier  230  of the supply cartridge  110  is written into the paired cartridge identifier  350  of the mixing cartridge  120 . Similarly, the cartridge identifier  330  of the mixing cartridge  120  is written into the paired cartridge identifier  250  of the supply cartridge  120 . Checks to ensure that the cartridges are not counterfeit may be performed initially, for example that an authentication process can be performed by each cartridge. If there are no fields for paired cartridge identifiers this may also indicate a counterfeit cartridge. In these cases an error message may be displayed to a user of the printing apparatus that the cartridge(s) can not be accepted. 
     If the paired cartridge identifiers  250 ,  350  are recovered, the method  800  moves to block  830  where these are checked against the cartridge identifier  230 ,  330  in the other cartridge. For example, the paired cartridge identifier  250  in the supply cartridge  110  is compared with the cartridge identifier  330  in mixing cartridge  120 . If these do not match the method moves to block  835  where an error message is displayed to a user and the cartridge is rejected for use with the printing apparatus. Similarly, the paired cartridge identifier  350  in the mixing cartridge  120  is compared with the cartridge identifier  230  in supply cartridge  110 . If these do not match the method moves to block  835  where an error message is displayed to a user and the cartridge is rejected for use with the printing apparatus. If the paired cartridge identifiers  250 ,  350  do match the cartridge identifiers  330 ,  230  on the other cartridge, then the method moves to block  825  where operation of the printing apparatus using the cartridges may begin—for example as described above. 
     The method  800  ties a supply and mixing cartridges together so that they can only be used together in a printing apparatus  100 . The paired cartridge identifiers  250 ,  350  may be used with or without the removal protection parameters  236 ,  336  which can be used to tie a cartridge  110 ,  120  to a particular printing apparatus  100 . For example, using only the paired cartridge identifiers  250 ,  350  it is possible that the corresponding cartridges  110 ,  120  may be used together in a different printing apparatus. 
     Referring to  FIG. 6 , a method  600  of operating a printing apparatus is illustrated and may be implemented by the controller  155  of the printing apparatus of  FIG. 1  and the integrated circuits and fields in the supply cartridges  110  of  FIG. 2 . The method  600  may be performed to control recirculation processes within the printing apparatus  100  using process instructions stored on the supply cartridge  110 . The recirculation process may be specific to ink stored in the reservoir  115  and/or to the printing apparatus  100  on which the recirculation is to be performed. As noted above, the process instructions may be stored in a field or location  255  of the integrated circuit memory  217 . The process instructions may be stored in the form of an encrypted, compressed XML file, although other file types may alternatively be used. More than one set of process instructions may be stored for use with different printing apparatus. 
     At block  605 , the printing apparatus checks the supply cartridge for a recirculation process file. Where multiple sets of process instructions are included for different printing apparatus, an index may be provided including printing apparatus identifiers to indicate whether the printing apparatus is supported. At block  610 , if no process file or instructions are found, the method moves to block  630  to reject the cartridge and to indicate an error message to the user. If appropriate process instructions  255  are found, the method moves to block  620 . 
     At block  620  the process instructions  255  are retrieved from the cartridge  110  and are decompressed. The decompressed process instructions may be in the form of an XML file containing instructions directly interpretable by the controller  155  of the printing apparatus  100 . At block  625  the controller executes the instructions to transport ink to and from the cartridge  110  as well as within the printing apparatus in order to mix the ink to avoid precipitating particles which may cause blockages and/or reduce print quality. 
     An example of process instructions is shown below and is described with respect to  FIGS. 7A and 7B . The printing apparatus  700  comprises pumps  745  (labelled P- 1  and P- 2  in the figure and pump_ 1  and pump_ 2  in the XML code below) and valves  740  (labelled V- 1 , V- 2 , V- 3 , V- 4  in the figure and valve_ 1 , valve_ 2 , valve_ 3 , valve_ 4  in the XML code below). These transport components are controlled to move ink within the printing apparatus to its different parts, including to and from the supply cartridge  710  and a mixing cartridge  720 . The heavy lines show transport of the ink, in the case of  FIG. 7A  from the supply cartridge  710  to the mixing cartridge  720 , and in the case of  FIG. 7B  the reserve direction from the mixing cartridge back to the supply cartridge. This recirculation cycle may be repeated at predetermined time periods, following periods of inactivity where no printing occurs, or following or preceding other recirculation cycles. This or a combination of recirculation cycles may depend on the ink being transported and/or the printing apparatus used. 
     An XML file for the operations illustrated in  FIGS. 7A and 7B  is shown below: 
     
       
         
           
               
               
             
               
                   
                   
               
             
            
               
                   
                 &lt;processing&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;xml xml_index=“1” version=“1” encoding=“utf-8”/&gt; 
               
               
                   
                 &lt;mixing_AtoB&gt; 
               
               
                   
                 &lt;pump_1 action=“ON” duration=“10” PWM= “50” 
               
               
                   
                 direction=“reverse”/&gt; 
               
               
                   
                 &lt;pump_1 action=“ON” duration=“10” PWM= “50” 
               
               
                   
                 direction=“reverse”/&gt; 
               
               
                   
                 &lt;pump_2 action=“OFF” duration=“10” PWM= “0” 
               
               
                   
                 direction=“forward”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;valve_1 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_2 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_3 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_4 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;trigger stop=“time”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;/mixing_AtoB&gt; 
               
               
                   
                 &lt;mixing_BtoA&gt; 
               
               
                   
                 &lt;pump_1 action=“ON” duration=“10” PWM= “50” 
               
               
                   
                 direction=“reverse”/&gt; 
               
               
                   
                 &lt;pump_2 action=“OFF” duration=“10” PWM= “0” 
               
               
                   
                 direction=“forward”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;valve_1 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_2 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_3 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_4 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;trigger stop=“time”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;/mixing_BtoA&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;/processing&gt; 
               
               
                   
                   
               
            
           
         
       
     
     In order to move the ink from the supply cartridge  110  to the mixing cartridge  120 , pump_ 1  (V- 1 ) is turned on in the reverse direction and pump_ 2  (P- 2 ) is off, valve_ 1  (V- 1 ) and valve_ 2  (V- 2 ) are closed and valve_ 3  (V- 3 ) and valve_ 4  (V- 4 ) are open. In order to move the ink back from the mixing cartridge  120  to the supply cartridge  110 , pump_ 1  (V- 1 ) is turned on in the reverse direction and pump_ 2  (P- 2 ) is off, valve_ 1  (V- 1 ) and valve_ 2  (V- 2 ) are open and valve_ 3  (V- 3 ) and valve_ 4  (V- 4 ) are closed. The process description or instructions are shown for printer xml_index=1; different printers may use the same or different process instructions. 
     Process instructions for a different ink are shown below and are described with respect to  FIGS. 7C and 7D . The instructions are for the same printing apparatus, or same group of printing apparatus, and requires more complex recirculation than the first ink type, including passing through the printhead  730 . 
     In order to move the ink from the supply cartridge  110  to the mixing cartridge  120 , pump_ 1  (V- 1 ) is turned off and pump_ 2  (P- 2 ) is turned on in the forward direction. Valve_ 1  (V- 1 ) and valve_ 2  (V- 2 ) are closed and valve_ 3  (V- 3 ) and valve_ 4  (V- 4 ) are open. In order to move the ink back from the mixing cartridge  120  to the supply cartridge  110 , pump_ 1  (V- 1 ) is turned off and pump_ 2  (P- 2 ) is turned on in the forward direction. Valve_ 1  (V- 1 ) and valve_ 2  (V- 2 ) are open and valve_ 3  (V- 3 ) and valve_ 4  (V- 4 ) are closed. 
     An XML file for the operations illustrated in  FIGS. 7A and 7B  is shown below: 
     
       
         
           
               
               
             
               
                   
                   
               
             
            
               
                   
                 &lt;processing&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;xml xml_index=“3” version=“2” encoding=“utf-8”/&gt; 
               
               
                   
                 &lt;mixing_AtoB&gt; 
               
               
                   
                 &lt;pump_1 action=“OFF” duration=“10” PWM= “50” 
               
               
                   
                 direction=“reverse”/&gt; 
               
               
                   
                 &lt;pump_2 action=“ON” duration=“10” PWM= “25” 
               
               
                   
                 direction=“forward”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;valve_1 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_2 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_3 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_4 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;trigger stop=“pressure” target=“10psi”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;pump_1 action=“OFF” duration=“10” PWM= “0” 
               
               
                   
                 direction=“reverse”/&gt; 
               
               
                   
                 &lt;pump_2 action=“OFF” duration=“10” PWM= “0” 
               
               
                   
                 direction=“forward”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;valve_1 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;valve_2 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;valve_3 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;valve_4 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;trigger stop=“time”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;/mixing_AtoB&gt; 
               
               
                   
                 &lt;mixing_BtoA&gt; 
               
               
                   
                 &lt;pump_1 action=“OFF” duration=“10” PWM= “50” 
               
               
                   
                 direction=“forward”/&gt; 
               
               
                   
                 &lt;pump_2 action=“ON” duration=“10” PWM= “25” 
               
               
                   
                 direction=“reverse”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;valve_1 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_2 action=“power_on” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_3 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;valve_4 action=“power_off” duration=“20”/&gt; 
               
               
                   
                 &lt;trigger stop=“pressure” target=“10psi”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;pump_1 action=“OFF” duration=“10” PWM= “0” 
               
               
                   
                 direction=“reverse”/&gt; 
               
               
                   
                 &lt;pump_2 action=“OFF” duration=“10” PWM= “0” 
               
               
                   
                 direction=“forward”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;valve_1 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;valve_2 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;valve_3 action=“power_off” duration=“0”/&gt; 
               
               
                   
                 &lt;valve_4 action=“power_off” duration=“0”/&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;trigger stop=“time”/&gt; 
               
               
                   
                 &lt;/mixing_BtoA&gt; 
               
            
           
           
               
               
            
               
                   
                 &lt;/processing&gt; 
               
               
                   
                   
               
            
           
         
       
     
     A combination of these actions may be performed for predetermined time periods and the same or different pump rates. The same or different time periods may be used for controlling the valves. This file also has a higher version number so the printing apparatus uses the latest version even if an earlier version is stored locally, for example from a firmware update, or an earlier cartridge stored process description or instructions. 
     The controller  155  interprets the recirculation instructions and may control various components such as pumps using local operating system instructions. Various compression algorithms may be used for compressing the recirculation process instructions file, including for example those described in PCT patent publication WO2017/086989. Various authentication and control processes may be used to ensure that the process instructions  255  are protected in the integrated circuit or smart chip and are only accessible by authorized printing apparatus. For example, the cartridge processor  213  may be an I2C slave microcontroller and the printer controller processor  157  may be the I2C master. The microcontroller  213  may be read by the printer controller  155 ,  157  by addressing a read field and cryptographically authenticating the read message and loading into a read field, although other secure methods may be employed. An example of a mechanism for securely interacting with a cartridge is described in PCT patent publication WO2016/068990. 
     In another example, a separate removable mixing cartridge may not be used and the ink may be moved between the supply cartridge, an intermediate tank permanently within the printing apparatus and the printhead(s). In other examples a different file type may be used than XML to contain recirculation instructions which can be retrieved by a printing apparatus and executed. The recirculation process may be triggered in different ways, for example based on time, temperature, printer usage, ink levels, etc. 
     The process instructions may be adapted to the ink in the supply cartridge. For example, a whitening agent such as titanium dioxide TiO2 particles may be dissolved in a carrier together with a dispersant additive which keeps the particles in suspension longer, but this can decrease the performance of the ink in the printing process. The ratio between dispersant and TiO2 particles therefore needs to be carefully controlled and the recirculation processes can be tailored to ensure appropriate movement of the ink depending on different ink compositions in order to avoid precipitation of the particles. Therefore, the recirculation instructions may be updated as ink compositions change over time and the most appropriate recirculation procedures can be incorporated by printing apparatus when the supply cartridge is installed thereby effectively adapting older printers (as well as new printers) to changing ink compositions over time. 
     In some examples the ink may comprise one or more of the following: white pigments; titanium dioxide; dye sub ink; reactive ink; enamel ink; organic compounds; latex binders. The printing material cartridge may include an at least partially flexible container to hold the ink and a support structure to hold the container. The container may be is a bag and the support structure may be a carton box. In some examples the carton box may contain a single bag and in other examples the carton box may contain two or more bags. 
     In some examples, the percentage of solid pigments by weight is approximately 20-25% for white ink and 10-15% for other inks. In other examples the solid pigments by weight is 15-30% for white ink and 10-20% for other inks. In some examples the D90 particle size distribution for white inks is 350-550 nm and 200-450 nm for other inks. In other examples the D90 particle size distribution for white inks is 300-600 nm and 150-500 nm for other inks. 
     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. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples