printer

Abstract

There is provided a continuous inkjet printer. The continuous inkjet printer comprises a controller and a printhead. The printhead comprises an ink chamber for containing ink; a nozzle, in fluid communication with the ink chamber, configured to form a jet of droplets of ink; a charge electrode assembly for applying a charge to the droplets of ink; a deflection electrode assembly for deflecting charged droplets of ink; and a gutter for collecting unprinted droplets of ink. The controller is configured to determine a range of available operating ink temperatures and control at least one operating parameter of the continuous inkjet printer based upon an operating ink temperature selected within the available operating range.

Description

[0001] Printer

[0002] The present invention relates to a continuous inkjet printer and a method of using a continuous inkjet printer.

[0003] Industrial printers, such as continuous inkjet printers including binary array inkjet printers and multi jet inkjet printers, are used in production line printing to mark products or product packaging with information related to the product. These printers are sophisticated devices with many components. For example, continuous inkjet printers include components to charge ink and other components apply electric fields in order to control movement of the charged droplets of ink to form desired patterns on the product or product packaging.

[0004] Continuous inkjet printing is an established technique for marking information on rapidly moving substrates in industrial environments such as production lines. Although such arrangements usually comprise a fixed printer and moveable substrate, the reverse is also in principle possible.

[0005] One or more continuous ink jets are emitted by one or more printing nozzles located on a printhead. The printhead is in fluid communication with an ink reservoir which contains ink of a suitable composition. In multi-jet applications a plurality of nozzles and / or orifices each corresponding to an ink jet may be provided. The printing orifices, and thus the ink jets, may be arranged as an array. In binary array printers, the spacing of the ink jets in the array determines the horizontal and / or vertical resolution of the printhead. It will be apparent that different applications may require different printhead resolutions.

[0006] Vibration is applied to the one or more ink jets typically by one or more piezoelectric elements suitably disposed in, and coupled with, parts of the printhead and / or the nozzles individually. In use, the ink jets are caused by the vibration to break off into discrete droplets of ink which may be selectively charged so that they can be selectively deflected downstream of the nozzle(s), on their travel to the printed substrate, by an electric deflection field generated by, usually, corresponding deflection plates. The arrangement is such that, typically, the charged droplets are deflected into a gutter and, from there, returned to the ink reservoir, whereas the uncharged droplets are printed onto the moving substrate. Such arrangements are known as binary arrays.

[0007] The ink that is ejected from the nozzle or nozzles of the printhead comprises dye / pigment and solvent. Continuous inkjet printers consume makeup (solvent used to dilute ink to maintain the correct rheology for printing) during standard operation, as well as when idling between prints.

[0008] The rate of solvent consumption is especially significant for binary array printers (MU). Higher rates of solvent usage increase operating costs and the regularity with which a solvent source must be replenished for example by replacing makeup / solvent cartridges in the printer.

[0009] There exists a need to provide an alternative continuous inkjet (C ) printer that overcomes one or more of the disadvantages of known systems, whether mentioned in this document or otherwise.

[0010] The optional and / or preferred features for each aspect of the invention set out herein are also applicable to any other aspects of the invention.

[0011] According to a first aspect of the invention there is provided a continuous inkjet printer, comprising: a controller; and a printhead, the printhead comprising: an ink chamber for containing ink; a nozzle, in fluid communication with the ink chamber, configured to form a jet of droplets of ink; a charge electrode assembly for applying a charge to the droplets of ink; a deflection electrode assembly for deflecting charged droplets of ink; and a gutter for collecting unprinted droplets of ink; wherein the controller is configured to: determine a range of available operating ink temperatures; and control at least one operating parameter of the continuous inkjet printer based upon an operating ink temperature selected within the available operating range. The printer may be a continuous inkjet printer or a binary array inkjet printer.

[0012] The controller may be integrated with the printhead or may be arranged separately. The controller is provided to control the printhead, in particular it controls the generation of ink drops from the printhead and the generation of electric fields in the charge electrode assembly. The controller may be arranged to control a user interface and send and receive control signals to and from the printhead. The controller may be arranged to determine and report performance changes of the printhead and these may be displayed on a user interface.

[0013] The ink chamber encompasses a cavity in the printhead for containing ink. Where ink in the ink chamber is a composition of dye / pigment and solvent.

[0014] The nozzle encompasses an orifice or in some embodiments an array of orifices which extend through a wall of the ink chamber to allow ink to pass from the chamber to form jets. Actuation means may be provided to break the jet of ink into droplets of ink at a predetermined distance from when the jet of ink emanates from the nozzle.

[0015] The charge electrode assembly encompasses means for selectively electrically charging droplets of the jet of ink, and the deflection electrode assembly encompasses means for deflecting the charged droplets. The gutter encompasses means for collecting droplets (which may be charged or uncharged dependent upon the type of printer) that are not used in printing.

[0016] The term “the controller is configured to determine a range of available operating ink temperatures” encompasses a plurality of available operating ink temperatures and the controller determining a range of ink temperatures, that may be used during a printing process. The controller may determine this range using empirical data known for the type of ink in the printhead. The empirical data may relate to particular characteristics of the ink e.g. its boiling point, or a point at which the ink becomes too viscous. The range of available operating temperatures may also be based upon temperature data and / or humidity data, which may be obtained from the printer or an external source. The term “operating ink temperature” encompasses the temperature of ink at a particular location in the printer. For example, the operating ink temperature may be the temperature of the ink in the ink chamber of the printhead. On the other hand, it may be the temperature of the ink in an ink source. It will be appreciated that the temperature of ink in a printer may vary at different locations in the printer due to, for example, heat losses when transporting ink from on location to another or heat gains when heating the ink at a particular location, and therefore the operating ink temperature is the temperature of ink at a known location.

[0017] The controller determining a range of available operating ink temperatures is beneficial as it allows the temperature of the ink to be selectively controlled within the available operating range. That is to say, during initiation / start-up or even during use of the printer a user may be able to select which ink temperature they wish for the assembly / printer to run at. Alternatively, the ink temperature may not be selected by a user, it may be for example selected by the controller based upon the temperature data.

[0018] The term the “controller is configured to control at least one operating parameter of the continuous inkjet printer” encompasses the controller maintaining and / or adjusting operating parameters of the continuous inkjet printer. Parameters of the continuous inkjet printer may include but are not limited to a transducer frequency, a transducer modulation voltage; a printhead pressure, a printhead ink drop velocity, ink temperature, ink composition, ink rheology, and ink viscosity.

[0019] The controller may be configured to adjust a first continuous inkjet printer operating parameter. Then in response to the first continuous inkjet printer operating parameter being adjusted it may make further adjustments to the same parameter and / or to other operating parameters. The controller may maintain the first operating parameter following an adjustment.

[0020] Providing a controller that can adjust one or more operating parameters in response to an operating ink temperature being selected is beneficial as it allows for the operating ink temperature of the ink to be selected. In particular, continuous and multi-jet inkjet printers are commonly run at a set temperature, whereas being able to select an operating ink temperature that is a lower (or higher) temperature than the usual set temperature, can reduce energy consumption, and more so, can reduce solvent consumption.

[0021] The controller may be configured to select and / or receive an indication of a temperature in the range of available operating ink temperatures.

[0022] That is to say that the controller, may automatically select an operating ink temperature based upon the range of available operating ink temperatures generated, or the controller may receive an indication of an operating ink temperature from a user input or from other another controller.

[0023] The continuous inkjet printer my further comprise an ink temperature sensor configured to generate data indicative of a temperature of the ink in the ink chamber and provide the generated data to the controller; and wherein the controller may be configured to determine the range of available operating ink temperatures based upon the sensed temperature data.

[0024] The ink temperature sensor encompasses any suitable type of sensor for sensing and recording temperature. The ink temperature sensor may be located in the printhead.

[0025] The ink temperature sensor may directly sense the temperature of ink in the ink chamber. The ink temperature may indirectly sense the temperature of ink in the ink chamber, for example by sensing the temperature of the ink at a different location to the ink chamber and said sensed temperature being indicative of the ink temperature in the ink chamber.

[0026] The controller may be configured to set a target ink rheology based upon the operating ink temperature selected, and the controller may be configured to control at least one operating parameter of the printer based upon the target ink rheology.

[0027] The term target ink rheology encompasses parameters of the physical properties of the ink including viscosity, viscoelasticity and surface tension. That is to say that the continuous inkjet printer may further comprise means for determining the rheology of the ink, for example a rheometer. It is beneficial to set a target ink rheology based upon the selected operating ink temperature. This is because the optimal rheology of the ink may change dependent upon the temperature of the ink. The controller may be arranged to adjust the ink rheology, for example by changing the make-up of the ink, such as adding solvent and / or other substances to the ink. As such the operating parameters may include solvent levels in the ink, in addition to the parameters listed above.

[0028] The controller may be configured to set a target ink viscosity based upon the operating ink temperature selected, and the controller may be configured to control at least one operating parameter of the printer based upon the target ink viscosity.

[0029] That is to say that the continuous inkjet printer may further comprise means for determining the viscosity of the ink, for example a viscometer. It is beneficial to set a target ink viscosity based upon the selected operating ink temperature. This is because the optimal viscosity of the ink may change dependent upon the temperature of the ink. The controller may be arranged to adjust the ink viscosity, for example by changing the make-up of the ink, such as adding solvent and / or other substances to the ink. As such the operating parameters may include solvent levels in the ink, in addition to the parameters listed above.

[0030] The controller may be configured to receive ambient temperature data, and wherein the controller may be configured to determine the range of available operating ink temperatures based upon the ambient temperature data.

[0031] The ambient temperature encompasses the air temperature surrounding the printer. The ambient temperature data may be provided to the controller form an external source. The continuous inkjet assembly may comprise an ambient temperature sensor, which is configured to sense the ambient temperature.

[0032] A minimum temperature in the range of available operating ink temperatures may be within a predetermined amount of the ambient temperature.

[0033] In other words, the minimum value that the ink temperature may be in the available operating range, may be a set amount higher or lower than the ambient temperature. By way of example, the minimum selectable temperature may be around 5 degrees Celsius lower than the ambient temperature. It will be appreciated that if the ink temperature is selected at a temperature lower than the ambient temperature the ink may require cooling.

[0034] Alternatively, the minimum ink temperature that can be selected may be a predetermined amount higher than the ambient temperature. That is to say that the minimum ink temperature that can be selected may be around 5 degrees Celsius higher than the ambient temperature. It will be appreciated that where the minimum selectable temperature is higher than the ambient temperature, the ink may require heating.

[0035] In some cases, the minimum temperature may be the ambient temperature.

[0036] The available operating ink temperature may also have a maximum value. The maximum value may be dependent upon the temperature data, and / or may be based upon the properties of the ink), for example the ink’s boiling point. In addition to the minimum temperature being within a predetermined amount of the ambient temperature, the available minimum operating ink temperature may also be based upon the properties of the ink. For example, the conductivity of the ink for a given rheology at a particular temperature. That is to say, in order to obtain an optimal ink rheology for a selected temperature, the ink may need to be diluted with solvent (or other substances), dilution of the ink may reduce the conductivity of the ink to unacceptable levels. Accordingly, the minimum ink temperature may be limited by conductivity requirements for printing that are not achievable at certain temperatures.

[0037] Limiting the available operating range of ink temperatures mitigates against a user selecting an unobtainable or incompatible temperature. By incompatible temperature, it is meant that if the ink were to be adjusted to that temperature it would not have the necessary properties to function as an ink for printing in a continuous inkjet printer, a multi-jet printer, or a binary array inkjet printer.

[0038] The continuous inkjet printer may further comprise a heater for heating ink, and wherein the operating parameters may include ink temperature.

[0039] The heater may be configured to heat the ink in the ink chamber. The heater may be configured to heat the ink at a location upstream of the ink chamber. The printer may comprise more than one heater provided at various locations. In addition, the ink may be heated by other components of the printer for example a pump. The printer may comprise one or more heat exchangers to facilitate the heating of ink. The heater may be used to the control the ink temperature. The heater may be used in combination with an ink temperature sensor to control the ink temperature.

[0040] The continuous inkjet printer may further comprise a transducer for generating the droplets of ink, and wherein the operating parameters include a frequency of the transducer and / or a modulation voltage of the transducer.

[0041] The term transducer encompasses an actuator. The transducer may be arranged to cause ink in the ink chamber to vibrate such that the jet of ink is broken down into droplets. The droplets of ink may be generated at a predetermined distance from the nozzle.

[0042] The transducer may be a piezoelectric transducer. The transducer is arranged to convert an electrical signal (a modulation signal) into mechanical vibration which is responsible for generating areas of low pressure in the ink jet, thereby triggering the formation of the ink droplets.

[0043] When the temperature of the ink is changed, the distance that a substrate which is printed on from the nozzle may also have to change. Likewise, the drying time of ink on the substrate may also change, and hence the rate and velocity at which ink is delivered from the printhead to the substrate may also be required to change. In order to achieve this, the frequency of the transducer may be controlled and / or the modulation voltage of the transducer may be controlled.

[0044] It will be appreciated that various droplet formation processes and printhead designs are possible, typically comprising one or more electromechanical actuators, such as piezoelectric elements.

[0045] The operating parameters may include a target velocity of the droplets of the ink. The target velocity of the droplets of ink may be interchangeably referred to as a target speed of the droplets of ink. It may be preferred to control or vary the velocity of the ink droplets when the operating ink temperature is changed.

[0046] The operating parameters may include a pressure in the printhead.

[0047] That is to say that the jet of ink droplets is a pressurised stream. When changing the temperature of the ink, an operating parameter which may need to be controlled is the pressure in the printhead. In particular, the pressure in the printhead may be the pressure inside ink chamber.

[0048] The continuous inkjet printer may further comprise an ink system for storing and supplying ink to the printhead, wherein the ink system may be in fluid communication with the ink chamber and the gutter.

[0049] The ink system may form part of a printer. The ink system is arranged to store and supply ink to the printhead, in particular the ink system may be arranged to pump and filter ink to the printhead. The ink system may comprise one or more of an ink tank, an ink cartridge, a solvent tank, a solvent cartridge, and a mixer tank where ink and solvent (or make-up fluid) are mixed prior to being delivered to the ink chamber in the printhead. The ink system may be arranged to measure and / or control the rheology of the ink in the mixer tank and / or in the ink tank. The ink system may also be arranged to heat the ink in the mixer tank and / or ink tank prior to delivering the ink to the printhead.

[0050] The ink system may further comprise a suction pump to draw unprinted ink from the gutter back to the ink tank or mixer tank.

[0051] The controller may be configured to control the temperature of the ink in the ink system.

[0052] That is to say that the controller may be arranged to maintain or adjust the temperature of ink in the ink system.

[0053] The controller may control the temperature of ink in the ink system based upon the temperature data from the temperature sensor. It may be particularly beneficial to control the temperature of ink in the ink system in binary array printers, where there are more than two jets of ink exiting the nozzle, and in most cases an array of jets, typically 256 or above. This is because the rate at which ink is ejected from the nozzles is typically higher than in a single (or dual head) continuous inkjet printer, therefore controlling the temperature of the ink in the ink system reduces the power required to heat or cool the ink to the selected operating temperature in-line between the ink system and the printhead, which beneficially results in a stable and consistent temperature of ink in the printhead.

[0054] In most instances, the ink may be heated to the selected temperature or close to the selected temperature in the ink system. However, in some cases, where the selected temperature is below the ambient temperature, ink may be cooled in the ink system. Ink may be cooled and heated in the ink system (and in the printhead) using conventional and known heating and cooling means.

[0055] The continuous inkjet printer may further comprise a solvent source; and wherein the controller may be configured to predict a consumption rate of the solvent source based upon the operating ink temperature selected within the available operating range.

[0056] The solvent source may be a solvent cartridge, or a solvent tank, or any other suitable source.

[0057] As is known in the art, the ink is mixed with fluid generally solvent prior to printing. The consumption of solvent is dependent upon a number of factors which include but are not limited to the rate of printing and the temperature of the ink.

[0058] Solvent consumption is often high in continuous inkjet printers due to ink continuously passing through the nozzle to a substrate or the gutter. Further, because solvent evaporates at a lower temperature than the dye / pigment in the ink, even when ink is recycled through the gutter the solvent levels in the ink often require topping-up so as to maintain the rheology of the ink. In selecting an operating ink temperature, the rate of solvent consumption will also change. The controller predicting a solvent consumption rate is advantageous as it allows a user to understand how the selected temperature will effect solvent consumption. In some printing processes, for example binary array printing where there is an array of continuous jets of ink and a large proportion of the ink is delivered to the gutter, solvent consumption may be a substantial cost. Therefore, being able to predict and adjust solvent consumption by selecting an operating ink temperature is particularly advantageous.

[0059] The printhead may be a binary array printhead, and the nozzle may be configured to form more than two jets of droplets of ink.

[0060] The term binary array printhead encompasses a multi-jet printhead. That is to say that the printhead is configured to generate more than two jets of droplets of ink. Typically, the printhead generates an array of jets of ink. The printhead may generate an array comprising 256 jets or above of ink.

[0061] A binary array printhead does not encompass a single or dual head continuous inkjet printer.

[0062] The deflection electrode assembly may be configured to deflect charged droplets of ink into the gutter.

[0063] In other words, the charge electrode assembly selectively charges droplets of ink. The droplets of ink which are charged are deflected and pass into the gutter. Whereas the uncharged droplets are not deflected when passing through the deflection electrode assembly and a printed onto a substrate.

[0064] In contrast, in single head continuous inkjet printers, the charged droplets are typically deflected and printed onto a substrate, and the uncharged droplets are delivered to the gutter.

[0065] According to a second aspect of the invention, there is provided a continuous inkjet printer, comprising: a controller; and a printhead, the printhead comprising: an ink chamber for containing ink; a nozzle, in fluid communication with the ink chamber, configured to form a jet of droplets of ink; a charge electrode assembly for applying a charge to the droplets of ink; a deflection electrode assembly for deflecting charged droplets of ink; and a gutter for collecting unprinted droplets of ink; and wherein an operating ink temperature of the printer is selectable.

[0066] That is to say that a user may select an operating ink temperature to be used in the printer. In some instances, the controller may select the operating ink temperature.

[0067] The controller may be configured determine a range of available operating ink temperatures. The controller may be configured to control at least one operating parameter of the continuous inkjet printer based upon an operating ink temperature selected within the available operating range.

[0068] The optional features of the first aspect of the invention may be combined with the second aspect of the invention

[0069] According to a third aspect of the invention, there is provided a method of using a continuous inkjet printer, the method comprising: determining a range of available operating ink temperatures; selecting an operating ink temperature from the range of available operating ink temperatures; controlling at least one operating parameter of the printer in response to the operating ink temperature selected.

[0070] The printer may be a continuous inkjet printer or a binary array printer.

[0071] Determining a range of available operating ink temperatures encompasses determining a range of ink temperatures that may be used during a printing process. This range may be determined using empirical data known for the type of ink in the printer. The range may be determined by using ink temperature data or ambient temperature that it receives. The range may be determined using a controller

[0072] Determining a range of available operating ink temperatures is beneficial as it allows the temperature of the ink to be selectively controlled within the available operating range. That is to say, during initiation / start-up or even during use of the printer a user may be able to select which ink temperature they wish for the assembly / printer to run at. Alternatively, the operating ink temperature may not be selected by a user, it may be for example selected by the controller based upon the temperature data.

[0073] The term “controlling with at least one operating parameter of the printer in response to the operating ink temperature selected” encompasses maintaining and / or adjusting operating parameters of the printer. Parameters of the printer may include but are not limited to a transducer frequency, a transducer modulation voltage; a printhead pressure, a printhead ink drop velocity, ink temperature, and ink viscosity.

[0074] A controller may control the at least one operating parameter of the printer in response to the operating ink temperature selected.

[0075] The controller may be part of a printhead. The controller may be part of an ink system. The controller may be an external controller.

[0076] The method may further comprise receiving temperature data; and determining the range of available operating ink temperatures based upon the received temperature data.

[0077] The temperature data may be ambient temperature data. The range of available operating ink temperatures may be determined using known characteristics of the ink in combination with the temperature data.

[0078] The temperature data may be generated from an ink temperature sensor. The ink temperature sensor may be located in a printhead, in particular the ink temperature data may sense the temperature of ink in an ink chamber in the printhead. The ink temperature data may be communicated from the ink temperature sensor The controller may select the operating ink temperature.

[0079] That is to say that the operating ink temperature is selected without input from a user.

[0080] The method may further comprise measuring an ink temperature and comparing the ink temperature to the operating ink temperature selected.

[0081] The ink temperature measured may be the ink in an ink chamber of a printhead. The ink temperature measured may be the ink in an ink cartridge, an ink tank, a mixer tank, or along a fluid line, or any other suitable location.

[0082] In doing so the controller can determine if the operating parameters require further adjustments. This step may be undertaken multiple times as an iterative or closed loop control process, and different operating parameters may be maintained or adjusted after each comparison.

[0083] The comparison may occur at periodic time intervals so as to allow adequate time for any changes in the operating parameters to take place, for example heating of the ink.

[0084] The method may further comprise: controlling at least one operating parameter of the printer in response to the comparison of ink temperature and operating ink temperature selected.

[0085] The method may further comprise: measuring the ink viscosity; comparing the measured ink viscosity to a target ink viscosity; controlling at least one operating parameter of the printer in response to the comparison of the measured ink viscosity and the target ink viscosity.

[0086] Controlling of at least one parameter of the printer in response to the comparison allows for the viscosity to be maintained or adjusted as required. The at least one operating parameter may include temperature of the printhead and / or the ink, and the make-up of the ink i.e. the amount of solvent that is mixed with the ink. The ink viscosity may be measured in a printhead, in particular in an ink chamber of the printhead. The ink viscosity may be measured in an ink system, for example in a mixer tank, ink tank, or an ink cartridge. The target ink viscosity when measured in the printhead may be different to a target ink viscosity when measured in an ink system. The method may include measuring the ink viscosity at more than one location ink the printer.

[0087] The target ink viscosity may be predetermined based upon the printer that the ink is used in. The target ink viscosity may include a range of operable ink viscosities.

[0088] The method may further comprise: determining a target ink rheology based upon the operating ink temperature selected; and controlling the ink viscosity to achieve the target ink rheology.

[0089] It is beneficial to set a target ink rheology based upon the selected operating ink temperature, this is because the optimal rheology of the ink may change dependent upon the temperature of the ink. The ink viscosity may be controlled for example by adding additional solvent to the ink to decrease the viscosity. The ink viscosity may be controlled by allowing solvent to evaporate from the ink and / or by adding fresh ink to the ink. The ink viscosity may be controlled in the printhead.

[0090] The method may further comprise: determining the ambient temperature; and determining the range of available operating ink temperatures using the ambient temperature.

[0091] The ambient temperature encompasses the air temperature surrounding the printer. The ambient temperature may be determined using data from an external source. The printer may comprise an ambient temperature sensor which is configured to sense the ambient temperature.

[0092] The method may further comprise: determining the operating parameters to control using a look-up table of ink temperature data and ink viscosity data. That is to say that a controller may be provided with a look-up table or correlation data which has been empirically derived. Using this data, the controller can determine which operating parameters to control. This is particularly beneficial as the rheology of ink does not change uniformly with a uniform change in temperature. As such, the controller is able to optimise the other characteristics of the ink for a selected operating ink temperature.

[0093] The controller using this data and controlling operating parameters may be able to identify to a user, via a user interface, performance changes to the printer based upon the selected temperature. Thus, allowing a user to understand performance changes (e.g. print speed, drying time) as a result of selecting an ink temperature to operate at.

[0094] The method may further comprise controlling at least one operating parameter of:

[0095] (i) a transducer frequency;

[0096] (ii) a transducer modulation voltage;

[0097] (iii) a pressure in a printhead;

[0098] (iv) a printhead ink drop velocity;

[0099] (v) ink temperature;

[0100] (vi) ink viscosity;

[0101] (vii) ink rheology; and

[0102] (viii) ink composition.

[0103] The printhead may comprise one or more transducers (e.g. a piezoelectric transducer) or any suitable electromechanical actuator. As a result of selecting an ink temperature to operate at, the rate at which drops of ink are generated may need to change. Therefore, controlling (maintaining or adjusting) the transducer frequency and modulation voltage, allows for the printer to operate optimally at the selected operating ink temperature.

[0104] The jet or jets of ink droplets are a pressurised stream. When changing the temperature of the ink, an operating parameter which may need to be controlled is the pressure in the printhead, the pressure in the printhead may be the pressure inside an ink chamber. The term “ink temperature” may be the temperature of the ink in an ink chamber of a printhead.

[0105] Ink composition encompasses the proportion of solvent in the ink prior to printing.

[0106] The method may further comprise determining an expected solvent consumption rate of the printer.

[0107] That is to say the rate at which a solvent source may be consumed for a given operating ink temperature can be determined. The solvent consumption rate may be determined by a controller. Empirically derived data may be used to determine the solvent consumption rate.

[0108] The method may further comprise displaying the expected solvent consumption rate on a user interface.

[0109] In selecting an operating ink temperature, the rate of solvent consumption will also change. Determining a solvent consumption rate and displaying it on a user interface is advantageous as it allows a user to understand how the selected temperature will effect solvent consumption. In some printing processes, for example binary array printing where there is an array of continuous jets of ink and a large proportion of the ink is delivered to the gutter, solvent consumption may be a substantial cost. Therefore, being able to predict and adjust solvent consumption by selecting an operating ink temperature is particularly advantageous.

[0110] The method may further comprise selectively applying a charge to droplets of ink, and deflecting charged droplets of ink into a gutter of a printhead

[0111] The method may further comprise generating more than two jets of droplets of ink for printing.

[0112] According to a fourth aspect of the invention, there is provided a method of using a continuous inkjet printer, the method comprising: determining a range of available operating ink temperatures; and selecting an operating ink temperature from the range of available operating ink temperatures.

[0113] The method may further comprise controlling at least one operating parameter of the printer in response to the operating ink temperature selected.

[0114] Optional features of the third aspect of the invention may be combined with the fourth aspect of the invention.

[0115] It will, of course, be appreciated that features described in the context of one aspect of the invention may be combined with features described in the context of other aspects of the invention. For example, features of the printer (described as the first aspect above) may be combined with features of the printer in the second aspect or the methods of using a continuous inkjet printer (third and fourth aspects) and vice versa.

[0116] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0117] Figure 1 is a schematic illustration of a continuous inkjet printhead assembly of a continuous inkjet printer in accordance with an embodiment of the invention;

[0118] Figure 2 is a schematic illustration of a binary array inkjet printer in accordance with an embodiment of the invention;

[0119] Figure 3 is a graph illustrating the changes in viscosity with temperature for differing ink compositions; and

[0120] Figure 4 is a flow chart of a method of operating a continuous inkjet printer according an embodiment of the present invention.

[0121] A printhead 10 of a continuous inkjet printhead assembly 1 is schematically represented in Figure 1. In particular, the printhead 10 is for a binary array inkjet printer. The printhead 10 has at least one nozzle 11 for generating ink droplets 22, 23, 24, 25, 26 from a continuous stream of ink 21 (also schematically represented in Figure 1 as a set of overlapping droplets). The diagram is simplified for ease of understanding, but in use, there may be a plurality of streams of ink 21. The ink droplets and ink in the printer comprise dye / pigment and solvent, and may be interchangeably referred to as an ink-solvent composition. Various droplet formation processes and printhead designs are possible, typically comprising one or more electromechanical actuators, such as piezoelectric elements, converting an electrical signal (a modulation signal) into mechanical vibration which is responsible for generating areas of low pressure in the ink stream 21, thereby triggering the formation of the ink droplets 22, 23, 24, 25, 26. These components and mechanisms are described in the art, and will not be described further herein.

[0122] The ink droplets 22, 23, 24, 25, 26 are routed through a charge electrode assembly 13 for selectively acquiring charge. An electric field is selectively applied to the charge electrode assembly 13 at appropriate times, and at appropriate magnitudes, to induce a required charge on the selected droplets 23, 26. The other droplets 24, 25 remain electrically neutral, or have acquired a smaller or negligible amount of charge. In this described embodiment, the charged droplets 23, 26 are deflected by an electric deflection field applied between a deflection electrode assembly 15, and collected into a gutter system (not shown) for return to an ink reservoir (also not shown) in fluid communication with the printhead 10. The uncharged droplets 24, 25 are printed onto a moving substrate 12. Various designs and arrangements for the charge electrode 13, deflection plates 15, and the moving substrate are possible, and one related to a binary array printhead will be described in further detail below in connection with Figure 2. In an embodiment, a single earthed deflection plate 15 is used, which acts to cause charged droplets to be deflected towards the gutter system. The charge electrode assembly 13 and the deflection electrode assembly 15 may form part of the printhead 10.

[0123] In contrast, for continuous inkjet printers that are not of the binary array type, uncharged droplets of ink are generally returned to an ink system via the gutter which is generally positioned so as to capture droplets which are emitted from the nozzle orifice and which are not deflected. The charged droplets are printed on to the moving substrate at a position which varies in a direction that is substantially orthogonal to the direction of travel of the substrate. This position is controlled by selectively varying and electric field applied to the charge electrode, which provides a variable charge on the drops. The deflection of the droplets within a field created by a deflection electrode assembly, and hence the resulting position on the substrate, is governed primarily by the amount of charge on the drop.

[0124] The inkjet printhead assembly 1 further comprises a controller 50. The controller 50 is arranged to communicate data to and from the printhead 10 and to control operating parameters of the printhead 10 via communication line 51. The controller 50 is further arranged to control the charge electrode assembly 13 via communication line 52 and the controller is arranged to control the deflection electrode assembly 15 via communication line 53.

[0125] The printhead 10 further comprises a temperature sensor 30. The sensor 30 is shown in the printhead 10, but may be provided in other parts of the inkjet printhead assembly 1.

[0126] The temperature sensor 30 is an ink temperature sensor and is configured to measure the temperature of the ink. In particular, the temperature sensor 30 senses the temperature of the ink in an ink chamber or cavity of the printhead 10. The ink temperature sensor 30 in some embodiments may not sense the temperature of the ink directly in the printhead 10. For example, the ink sensor 30 may be provided in an ink tank or ink cartridge in an ink system, or in a fluid line for transporting ink. If the ink temperature sensor 30 is not configured to directly sense the temperature in the ink chamber, the ink temperature that it does sense may be indicative of the ink temperature in the ink chamber.

[0127] Additional temperature sensors (not shown) may be provided which measure the ambient temperature. The additional temperature sensors may be integral with the printhead 10, or the printhead assembly 1 , or the printer itself, or they may be external temperature sensors. The ink temperature sensor 30 is configured to send data to the controller 50 via communication line 54.

[0128] Turning to Figure 2 which shows a schematic illustration of a binary array inkjet printer 100 in accordance with an embodiment of the invention. The same reference numerals are used for the same features as shown in Figure 1. The binary array inkjet printer 100 comprises an inkjet printhead assembly 1 having a controller 50 and a printhead 10.

[0129] The inkjet printhead assembly 1 comprises a transducer 102, an ink chamber 104 (the ink chamber may be interchangeably referred to as an ink cavity 104), a nozzle 11 , a charge electrode assembly 13, a deflection electrode assembly (not shown), and a gutter 106. The printhead 10 comprises the ink temperature sensor 30. The ink temperature sensor 30 is configured to sense the temperature of the ink in the ink chamber 104. The printhead 10 further comprises an ambient temperature sensor 31 for measuring the ambient (atmospheric) temperature. The ambient temperature sensor 31 does not need to be provided on the printhead 10. It may be provided on another portion of the printer 100, or in some embodiments the ambient temperature sensor may be external to the printer 100.

[0130] An array of droplets of ink 108 emanate from the nozzle 11 , through a plurality of orifices, and are selectively charged by the charge electrode assembly 13. The charged droplets are then deflected by the deflection electrode assembly into the gutter 106, and the uncharged droplets are printed on to a substrate 12.

[0131] The operation of the above mentioned features is well known in the art and so is not explained in detail in this specification.

[0132] The inkjet printer 100, further comprises an ink system 110. The ink system 110 generally comprises at least an ink source and a solvent source. The ink system may also comprise a mixer tank where additional solvent from the solvent source is added to ink from the ink source, or to ink returned from the printhead 10, in order to maintain the rheology of the ink to be printed. It will be appreciated that different ink systems may comprise various ink and solvent sources such as tanks and cartridges, and some systems 110 may not comprise a mixer tank.

[0133] The ink system 110 is in fluid communication with the printhead 10. That is to say that ink either from the ink source or a mixer tank (where applicable) is configured to be delivered to the ink chamber 104. The ink system 110 may be configured to deliver only ink and only solvent to the printhead 10. It may be beneficial to deliver only solvent for example during a cleaning process. The ink system 110 is also in fluid communication with the gutter 106 and is configured to receive the unprinted ink from the gutter 106.

[0134] The ink temperature sensor 30 is shown and described as being in the printhead 10 and sensing the temperature of the ink in the ink chamber 104. However, in other embodiments, the ink temperature sensor 30 may be provided in the ink system 110. In particular, it may be configured to sense the temperature of ink in the ink source or in a mixer tank. The ink temperature sensor 30 may be configured to sense the ink temperature in a fluid line between the ink system 110 and the printhead 10, or in any other suitable location. When the ink temperature sensor 30 is not configured to directly sense the temperature of ink the ink chamber 104, the ink temperature that is sensed may be indicative of the ink temperature in the ink chamber 104. Put another way, there may be a temperature relationship between the ink temperature at the location it is sensed at and the ink temperature in the ink chamber 104. Thus by sensing the temperature at a location other than the ink chamber 104, it may be possible to determine the temperature of ink in the ink chamber 104.

[0135] The printer 100 further comprises a main controller 112. The main controller 112 is in communication with the printhead 10 via the controller 50. The main controller 112 is configured to send and receive data and instructions from the controller 50.

[0136] In some embodiments, the controller 50, may be the main controller 112, and the main controller 112 is not required.

[0137] Figure 3 is a schematic representation 300 of the viscosity of different ink compositions as a function of temperature.

[0138] The first line 302 shows a temperature-viscosity relationship of a first ink composition.

[0139] The second line 304 shows a temperature-viscosity relationship of a second ink composition. Wherein the second ink composition is different to the first ink composition.

[0140] The third line 306 shows a temperature-viscosity relationship of a third ink composition. Wherein the third ink composition is different to the first and second ink compositions. The first, second and third ink compositions all comprise the same type of ink. The difference in the three compositions is that each comprises a different proportion of solvent.

[0141] Figure 3 is provided as a representative example to illustrate that it has been found that the viscosity-temperature relationship ink-compositions with different proportions of solvent is non-linear. That is to say that a change in the proportion of solvent in the composition may result in a non-linear shift in the viscosity-temperature relationship.

[0142] This schematic is provided to convey how the relationship of viscosity as function of temperature may change for different ink compositions and that the same change in temperature for different ink compositions can result in different changes in viscosity.

[0143] It will be appreciated that in practice, a person could conduct numerous experiments to determine viscosity-temperature relationships for ink- compositions that they are interested in.

[0144] Returning to Figure 2. The printhead 10 and the ink system 110 comprise a variety of other sensors 116. The sensors 116 may include, sensors to sense the viscosity of the ink in the ink chamber 104, and the ink source (and where applicable the mixer tank) in the ink system 110. The sensors 116, for simplicity are shown in the printhead 10, but it will be appreciated that they may be located in any suitable part of the printer 100. Sensors 116 may be arranged to measure the speed of a substrate 12 that is to be printed on (or the speed of the printhead 10, if the printhead moves during printing). In particular, a sensor 117, external to the printhead 10, is provided to sense the speed of the substrate 12. The sensor 117 is optional. Sensors 116 may further include sensing the speed of ink droplets 108 that are ejected from the printhead. Sensors 116 may include pressure sensors for sensing the pressure in the printhead 10. Any other suitable sensors for sensing operating parameters of the printhead 10 and ink system 110 may be provided. The sensors 116 are configured to provide data to the controller 50 and / or the main controller 112. For ease, in the schematic of Figure 2 only two sensors 116 are shown in the printhead 10 and one sensor 116 is shown in the ink system 110, however the printhead 10 and ink system 110 may each contain a plurality of various sensors 116. The printer 100 further comprises a user interface 114. The user interface 114 is configured to display a variety of information about the printhead 10 and the ink system 110. For example, the user interface 114 may display data about the volume of ink and / or solvent remaining in their respective sources; and / or the temperature of the ink in the ink chamber 104 that is received from ink temperature sensor 30 or any other suitable temperature sensor (which may provide temperature data indicative of the ink temperature in the ink chamber 104); and / or the ambient temperature that is received from another temperature sensor 116. The user interface 114 is ultimately arranged to receive data from the controller 50 and / or the main controller 112 and display the information to a user of the printer, including technicians.

[0145] The user interface 114 may also be arranged to receive input data from a user and communicate this data to the controller 50 and / or the main controller 112. The user interface may also be configured to receive input commands from a user, which may include but is not limited to start / stopping the printhead 10, initiating a cleaning stage of the printhead 10, and a command to prepare the printer 100 for replacing ink and solvent cartridges ink the ink system 110.

[0146] The user interface 114, also allows a user to select a temperature at which they wish for the printhead 10 to operate, i.e. the temperature of the ink. In conventional printers, the temperature of the ink is not a variable that can be changed by a user, and is instead at a set temperature, often around 35 degrees Celsius. It is beneficial to allow a user to adjust the temperature at which the printhead operates, as this will have an effect on the solvent consumption. In particular, the user may be able to select to run the printhead 10 at a temperature that reduces solvent consumption (or increases solvent consumption).

[0147] Solvent consumption in binary array printers is generally higher than other types of continuous inkjet printing, for example a single or dual head continuous inkjet printer. Solvent consumption is particularly high when the printhead 10 is in an “idle” or “ready to print” mode. In an idle mode, droplets of ink 108 are continuously ejected from the printhead 10, but all of the droplets are charged, meaning that the all of the droplets 108 are delivered to the gutter. Having an idle mode is often required in manufacturing settings where it is necessary to quickly swap from printing with one printhead 10 to printing with a different printhead 10 (i.e. when the first printhead encounters an error, blockage or requires maintenance). Being able to quickly swap to a different printhead 10 minimises downtime of printing on the substrates 12. An idle mode is also often required in settings where production and hence printing may be sporadic, and immediate readiness to print is required. However, running a printhead 10 in an idle mode results in solvent consumption, as the solvent in the ink still evaporates when ink is ejected from the nozzle 11 and delivered to the gutter 106. While some solvent vapour may be captured by the gutter 106, at least a portion of the solvent vapour is likely to pass out of a print slot and be lost from the printer

[0148] When a user selects a temperature for the printhead 10 to operate at, this is transmitted to the controller 50 and / or the main controller 112. The controllers 50,112 receiving this input of temperature that the printhead 10 should be operated at, then control at least one operating parameter of the printer 100. By way of example, the controllers 50, 112 may control a heating means or a cooling means of the printhead 10 to adjust the temperature of the ink- in the ink chamber 104. Other operating parameters that the controllers 50, 112 may control are changing the modulation voltage and / or frequency of the transducer 102. The controllers 50, 112 may control the velocity at which droplets of ink 108 are delivered to a substrate 12, the controllers 50, 112 may also control the speed of the substrate 12 or speed of the printhead 10. Controlling operating parameters of the printer 100 include maintaining and adjusting the parameters where necessary.

[0149] As already described in Figure 3, a change in temperature of an ink composition results in a change in viscosity of the composition, and that for the same change in temperature the change in viscosity is different for different ink compositions.

[0150] Allowing the temperature of the ink to be selected, requires the rheology of the ink to be adjusted and hence other operating parameters, so that the desired operating conditions of the printer are achieved. Following the selecting of a temperature, the printhead 10, via the controller 50 and / or main controller 120, and the user interface 114, can report an estimated rate of solvent consumption (e.g. the time taken for the solvent source to be depleted for the given operating the printer 100 at the selected temperature). The user interface 114 may also display changes to other aspects of the printing operation as a result of adjusting the temperature of the printhead 10. By way of example, changes in one or more of the throw distance, maximum print speed, printed drop opacity, print drying time, print quality and cleaning interval times may be displayed on the user interface.

[0151] A method 400 of operating the printhead 10 (of the type described in Figure 2) will now be described using the flow diagram of Figure 4.

[0152] The method of operating the printhead includes a step S1 of determining a range of available operating ink temperatures. This may be done using known data relating to the properties of the ink (e.g. characteristics of the ink) in the printer, for example by reading data provided on an electronic data storage device associated with an ink cartridge.

[0153] The range of available operating ink temperatures may also be determined by using temperature data from the ink temperature sensor 30, and / or other temperature sensors which provide data indicative of the ink temperature ink the ink chamber 104, and / or a temperature sensor 116 that measures the ambient temperature, and / or temperature data that is received from an external source, for example a building management or climate control system. In doing so the controller 50 and / or main controller 112 may receive temperature data, which is shown in Figure 4 as optional step SO.

[0154] In some embodiments the controller 50 may receive data from a humidity sensor. The humidity sensor may be part of the printer or it may be an external sensor. The range of available operating ink temperatures may also be determined by using data from the humidity sensor. By way of example, in high humidity environments, the minimum operating temperature may be higher, so as to avoid condensation on or within the printhead. At step SO, the controller may receive temperature and / or humidity data.

[0155] The controller 50 and / or the main controller 112 may use known data about properties of the ink and / or temperature data (e.g. from temperature sensors 30, 116) to generate a range of available operating ink temperatures of the printhead 10, i.e. a range or plurality of temperatures that the ink can be adjusted to whilst being able to adjust other parameters to achieve an acceptable or desired rheology of the ink composition. The controllers 50, 112 are able to determine the available range of operating ink temperatures using the temperature and / or humidity data provided and empirical data (for example the type of data shown in Figure 3) of how the rheology (in particular viscosity) of the ink composition may change for a given temperature. The controllers 50, 112 may use look-up tables which provide data of various characteristics (e.g. viscosity, conductivity, viscoelasticity, surface tension, droplet angle etc.) of the ink for a given temperature. The data in the look-up tables may have been generated by performing experiments.

[0156] The available operating range (or plurality) of temperatures that is determined by the controllers 50, 112, may have a maximum value. The maximum value may be limited by the characteristics of the ink, such as the boiling point. The range of available operating ink temperatures may also have a minimum value. The minimum value may be limited by the characteristics of the ink, for example when the viscosity of the ink is too high for printing operations. The minimum value may be within a pre-determined amount or percentage of the ambient temperature. By way of example, the minimum value may be 5 degrees higher than the ambient temperature, in other cases the minimum value may be 5 degrees lower than the ambient temperature, and in other cases the minimum value may be the ambient temperature. Put another way, if the ambient temperature is 18 degrees Celsius, if the minimum temperature in the available operating range has to be 5 degrees Celsius higher, then the minimum temperature in the available operating range would be 23 degrees Celsius. Setting minimum and / or maximum values in range mitigates against a user selecting an unobtainable or incompatible temperature. The minimum temperature may also be limited by the conductivity of the ink for a particular temperature. That is to say, the minimum available operating temperature may be set to a temperature where the conductivity of the ink meets a minimum rating for use in the printer. The conductivity of the ink may be determined using look-up tables of empirical data for a given ink rheology at a particular temperature.

[0157] Once the range of available operating ink temperatures have been determined an operating ink temperature may be selected, step S2. This operating ink temperature may be selected automatically by the controller, 50, 112. The operating ink temperature may be selected by a user, by displaying the range of operating ink temperatures on the user interface 112, and a user selecting a desired operating ink temperature. At step S3, following selection of the temperature, the performance characteristics of the printhead 10 operating with ink at the selected temperature are displayed on the user interface 114. The performance characteristics may include, but are not limited to the throw distance, maximum print speed, printed drop opacity, print drying time, print quality, and required cleaning interval. At step S3, the user interface 114 may display the predicted solvent consumption rate. In some instances, the user interface 114, may display the cost per hour of solvent and / or ink consumption. In some embodiments, step S3 may be omitted.

[0158] Following step S3, or step S2 in cases where S3 is omitted, at step S4 the temperature of the printhead 10 is adjusted to the selected operating ink temperature. In particular, the temperature of the ink in the printhead is adjusted to the selected operating ink temperature. In most instances, adjusting the operating ink temperature will involve heating the ink (in the ink chamber 104) to the selected operating ink temperature, however it could include maintaining the ink temperature if already at the selected operating ink temperature, and in some instances cooling the ink. Setting of the operating temperature may include an iterative or closed loop control process, of measuring the actual temperature of the ink and comparing it to the selected operating ink temperature, and controlling the temperature of the ink until the actual temperature is the same as (or is within an acceptable range of) the selected operating ink temperature.

[0159] In order to maintain optimal print settings, it may be preferred to set a target ink viscosity in response the selected operating ink temperature of the ink. The term target ink viscosity, encompasses the viscosity of the ink in the ink chamber 104; in some cases, it may also, or alternatively, include the viscosity of ink in a mixer tank in the ink system 110. It will be appreciated that the temperature of the ink in the ink chamber 104 may be different to the temperature of ink in the mixer tank. The ink temperature may be higher in the ink chamber 104 compared to in the mixer tank. The target ink viscosity will be set by the controller 50 and / or the main controller 112, in particular the target ink viscosity may be set using a viscosity management system. The target ink viscosity may be determined using look-up tables. The actual viscosity of the ink may be measured (e.g. using a viscometer), or inferred from other measurements, and compared to the target ink viscosity. The viscosity may then be adjusted until the ink viscosity is the same as (or within an acceptable range of) the target ink viscosity. The viscosity, may in addition to being adjusted by changing the temperature, may be adjusted, for example, by adjusting the amount of solvent in the ink.

[0160] The temperature of the ink in the ink chamber 104 may in some cases differ from the temperature of the ink where is it measured and controlled (i.e. in an ink tank or cartridge). The printer 100 is therefore in effect controlling the ink rheology. The term ink rheology encompasses parameters of the physical properties of the ink including viscosity, viscoelasticity and surface tension. The ink rheology may be controlled by setting a target viscosity for the conditions at which it is measured, based upon a known correlation between viscosity and temperature (as exemplified in Figure 3). The parameters of this correlation are unique to specific operating temperatures, and may be defined by a lookup table along with other operating parameters described below. The rheology of the ink may be adjusted primarily by controlling the solvent concentration in the ink. By way of example, additional solvent may be added to the ink, so as to thin the ink and reduce the viscosity. As another example, to increase the viscosity of the ink solvent may be allowed to evaporate and / or fresh ink may be added. Rheological properties other than viscosity may not be independently controlled, but their changes as a result of the control method (dilution of the ink) may be accounted for by other operating parameters.

[0161] As the ink rheology changes and may be adjusted following selection of operating ink temperature, the conductivity of the ink my also change. Prior to selecting an operating ink temperature, the controller 50 and / or the main controller 112 may determine the effect on other ink characteristics, for example conductivity, that selecting an operating ink temperature would have. It is important that the ink is conductive so that a charge can be selectively applied to droplets of ink. If selecting a particular operating ink temperature would result in the rheology of the ink changing such that the conductivity of the ink is not acceptable, such an operating temperature may be excluded from the available operating range of temperatures.

[0162] Following setting of the operating ink temperature, at step S5 and S6, the controller 50 and / or main controller 112 will determine which other parameters of the printer 100 require adjustment or control, and will then control the operating parameters accordingly. In other words, the controller 50 and / or main controller 112 control at least one operating parameter of the printer 100. Controlling an operating parameter includes maintaining or adjusting the operating parameters.

[0163] It may be necessary to control at least one operating parameter of the printer 100. As already described in relation to Figure 3, as the temperature of the ink changes the viscosity of the composition also changes. The change in viscosity of the ink does not exhibit a linear relationship with temperature. For a given temperature change, the viscosity of different ink compositions changes by differing amounts. In changing the ink temperature, the rheology of the ink will change, it is therefore may be necessary to control operating parameters of the printer 100 to achieve desired operating conditions with the adjusted rheology of the ink.

[0164] The operating parameters that may be controlled include but are not limited to controlling a heating or cooling element; controlling the frequency of the transducer 102, controlling the modulation voltage of the transducer 102, controlling the target velocity of droplets of ink 108, controlling the pressure in the printhead 10 (e.g. the pressure in the ink chamber 104), controlling the temperature of ink and / or solvent in the ink system 110, controlling the ink composition.

[0165] Once the operating parameters have been controlled, printing may begin (step S7). The step S7 of printing may include, running the printhead 10 in an idle mode.

[0166] Although the above steps have been described in relation to a binary array inkjet printhead, it will be appreciated that they may be applied to a single or dual head continuous inkjet printer.

Claims

CLAIMS:

1. A continuous inkjet printer, comprising: a controller; and a printhead, the printhead comprising: an ink chamber for containing ink; a nozzle, in fluid communication with the ink chamber, configured to form a jet of droplets of ink; a charge electrode assembly for applying a charge to the droplets of ink; a deflection electrode assembly for deflecting charged droplets of ink; and a gutter for collecting unprinted droplets of ink; wherein the controller is configured to: determine a range of available operating ink temperatures; and control at least one operating parameter of the continuous inkjet printer based upon an operating ink temperature selected within the available operating range.

2. The continuous inkjet printer according to claim 1, wherein the controller is configured to select and / or receive an indication of a temperature in the range of available operating ink temperatures.

3. The continuous inkjet printer according to claim 1 or claim 2, further comprising an ink temperature sensor configured to generate data indicative of a temperature of the ink in the ink chamber and provide the generated data to the controller; and wherein the controller is configured to determine the range of available operating ink temperatures based upon the sensed temperature data.

4. The continuous inkjet printer according to any of claims 1 to 3, wherein the controller is configured to set a target ink rheology based upon the operating ink temperature selected, and the controller is configured to control at least one operating parameter of the printer based upon the target ink rheology.

5. The continuous inkjet printer according to any of claims 1 to 4, wherein the controller is configured to set a target ink viscosity based upon the operating inktemperature selected, and the controller is configured to control at least one operating parameter of the printer based upon the target ink viscosity.

6. The continuous inkjet printer according to any of claims 1 to 5, wherein the controller is configured to receive ambient temperature data, and wherein the controller is configured to determine the range of available operating ink temperatures based upon the ambient temperature data.

7. The continuous inkjet printer according to claim 6, wherein a minimum temperature in the range of available operating ink temperatures is within a predetermined amount of the ambient temperature.

8. The continuous inkjet printer according to any preceding claim, further comprising a heater for heating ink, and wherein the operating parameters include ink temperature.

9. The continuous inkjet printer according to any preceding claim, further comprising a transducer for generating the droplets of ink, and wherein the operating parameters include a frequency of the transducer and / or a modulation voltage of the transducer.

10. The continuous inkjet printer according to any preceding claim, wherein the operating parameters include a target velocity of the droplets of the ink.

11. The continuous inkjet printer according to any preceding claim, wherein the operating parameters include a pressure in the printhead.

12. The continuous inkjet printer according to any preceding claim, further comprising an ink system for storing and supplying ink to the printhead, wherein the ink system is in fluid communication with the ink chamber and the gutter.

13. The continuous inkjet printer according to claim 12, wherein the controller is configured to control the temperature of the ink in the ink system.

14. The continuous inkjet printer according to any preceding claim, further comprising a solvent source; and wherein the controller is configured to predict a consumption rate of the solvent source based upon the operating ink temperature selected within the available operating range.

15. The continuous inkjet printer according to any preceding claim, wherein the printhead is a binary array printhead, and the nozzle is configured to form more than two jets of droplets of ink.

16. The continuous inkjet printer according to claim 15, wherein the deflection electrode assembly is configured to deflect charged droplets of ink into the gutter.

17. A method of using a continuous inkjet printer, the method comprising: determining a range of available operating ink temperatures; selecting an operating ink temperature from the range of available operating ink temperatures; controlling at least one operating parameter of the printer in response to the operating ink temperature selected.

18. The method according to claim 17, wherein a controller controls the at least one operating parameter of the printer in response to the operating ink temperature selected.

19. The method according to claim 18, further comprising: receiving temperature data; and determining the range of available operating ink temperatures based upon the received temperature data.

20. The method according to claim 18 or claim 19, wherein the controller selects the operating ink temperature.

21. The method according to any of claims 17 to 20, further comprising measuring an ink temperature and comparing the ink temperature to the operating ink temperature selected.

22. The method according to claim 21 , further comprising: controlling at least one operating parameter of the printer in response to the comparison of ink temperature and operating ink temperature selected.

23. The method according to any of claims 17 to 22, wherein the method further comprises: measuring the ink viscosity; comparing the measured ink viscosity to a target ink viscosity; controlling at least one operating parameter of the printer in response to the comparison of the measured ink viscosity and the target ink viscosity.

24. The method according to any of claims 17 to 23 further comprising: determining a target ink rheology based upon the operating ink temperature selected; and controlling the ink viscosity to achieve the target ink rheology.

25. The method according to any of claims 17 to 24 further comprising: determining the ambient temperature; and determining the range of available operating ink temperatures using the ambient temperature.

26. The method according to any of claims 17 to 25 further comprising: determining the operating parameters to control using a look-up table of ink temperature data and ink viscosity data.

27. The method according to any of claims 17 to 26, further comprising controlling at least one operating parameter of:(i) a transducer frequency;(ii) a transducer modulation voltage;(iii) a pressure in a printhead;(iv) a printhead ink drop velocity;(v) ink temperature;(vi) ink viscosity;(vii) ink rheology; and(viii) ink composition.

28. The method according to any of claims 17 to 27, further comprising determining an expected solvent consumption rate of the printer.

29. The method according to any of claims 17 to 28, further comprising selectively applying a charge to droplets of ink, and deflecting charged droplets of ink into a gutter of a printhead30. The method according to any of claims 17 to 29, further comprising generating more than two jets of droplets of ink for printing.

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