WO2025257572A1

WO2025257572A1 - Printer and associated method

Info

Publication number: WO2025257572A1
Application number: PCT/GB2025/051308
Authority: WO
Inventors: David Andrew Horsnell; Michael Jeffrey Stamp; William James Towry LEWIS
Original assignee: Videojet Technologies Ltd; Videojet Technologies Inc
Current assignee: Videojet Technologies Ltd; Videojet Technologies Inc
Priority date: 2024-06-14
Filing date: 2025-06-13
Publication date: 2025-12-18
Anticipated expiration: 2026-12-14
Also published as: GB202408544D0

Abstract

A print head for a continuous inkjet printer is disclosed. The print head comprises a nozzle, a charge electrode, at least one electrode, a gutter and a heating element. The nozzle is for generating and ejecting a stream of ink droplets for printing. The charge electrode is for selectively charging the stream of ink droplets. The at least one electrode is for guiding the stream of ink droplets. The gutter is for receiving droplets of ink which are not used for printing. The heating element is for drying the print head.

Description

_{Printer and method} _{The present invention relates to a print head, a continuous inkjet printer and various} associated methods. In inkjet printing systems, the print is made up of individual droplets of ink generated at a nozzle and propelled towards a substrate. There are two principal systems: droplet on demand, where ink droplets for printing are generated as and when required; and continuous inkjet (CIJ) printing, in which droplets are continuously produced and only selected ones are directed towards the substrate, the others being recirculated to an ink system. CIJ printers supply pressurised ink to a print head droplet generator where a continuous stream of ink emanating from a nozzle is broken up into individual regular droplets by, for example, an oscillating piezoelectric element. The droplets are directed past a charge electrode, where they are selectively and separately given a predetermined charge, before passing through a transverse electric field provided across a pair of deflection plates, the pair comprising a high voltage (or extra high tension (EHT)) plate and a zero or negative voltage plate (the ‘ground’ plate). Each charged droplet is deflected by the field by an amount that is dependent on its charge magnitude before impinging on the substrate, whereas the uncharged droplets proceed without deflection and are collected at a gutter from where they are recirculated to the ink system. The charged droplets bypass the gutter and hit the substrate at a position determined by the charge on the droplet and the position of the substrate relative to the print head. Typically the substrate is moved relative to the print head in one direction and the droplets are deflected in a direction generally perpendicular thereto, although the deflection plates may be oriented at an inclination to the perpendicular to compensate for the speed of the substrate (the movement of the substrate relative to the print head between droplets arriving means that a line of droplets would otherwise not quite extend perpendicularly to the direction of movement of the substrate). The various components of the print head are typically contained within a cover tube or print head casing. In CIJ printing, a character is printed from a matrix comprising a regular array of potential droplet positions. Each matrix comprises a plurality of columns (strokes), each being defined by a line comprising a plurality of potential droplet positions (e.g. seven) 69726509-2 determined by the charge applied to the Thus, each usable droplet is charged according to its intended position in the stroke. If a particular droplet is not to be used then the droplet is not charged and it is captured at the gutter for recirculation. This cycle repeats for all strokes in a matrix and then starts again for the next character matrix. Ink is delivered under pressure to the print head by an ink system that is generally housed within a sealed compartment of a cabinet that includes a separate compartment for control circuitry and a user interface panel. The ink system includes a main pump that draws the ink from a reservoir or tank (often referred to as a mixing tank) via a filter and delivers it under pressure to the print head. As ink is consumed, the reservoir is refilled as necessary from a replaceable ink cartridge that is releasably connected to the reservoir by a supply conduit. The ink is fed from the reservoir via a flexible delivery conduit to the print head. The unused ink droplets captured by the gutter are recirculated to the reservoir via a return conduit by a pump. The flow of ink in each of the conduits is generally controlled by solenoid valves and/or other like components. As the ink circulates through the system, there is a tendency for it to thicken because of solvent evaporation, particularly in relation to the recirculated ink that has been exposed to air in its passage between the nozzle and the gutter. In order to compensate for this, “make-up” solvent is added to the ink as required from a replaceable solvent cartridge to maintain the ink viscosity within desired limits. The ink and solvent cartridges are filled with a predetermined quantity of fluid and generally releasably connected to the reservoir, or mixing tank, of the ink supply system so that the reservoir can be intermittently topped-up by drawing ink and/or solvent from the cartridges as required. CIJ printers generally operate in high throughput environments for which the printers, and inks, need to be able to keep up with high production line speeds, fast drying time requirements and virtually non-stop production. A problem faced by operators of existing continuous inkjet printers is that of undesirable build-up of deposits within, and around, the print head. Deposits include ink ‘fur’, created by non-volatile ink components which remain after the fluid component of the ink (and solvent mixture) has evaporated. Such deposits risk the accuracy of printing, the operation of the print head, and, in extreme circumstances, may result in the blocking of an ink ejection aperture of the print head (e.g. rendering the print head non-operational 69726509-2 for at least a period of time). Deposits exist internally within the print head, but also _{externally. For example, an (external) end face of the print head (e.g. in which the ink} aperture is located) may also be liable to the build-up of deposits due to ink ‘splash-back’ during printing. There exists a need to provide an alternative continuous inkjet (CIJ) printer that overcomes one or more of the disadvantages of known systems, whether mentioned in this document or otherwise. According to a first aspect of the invention there is provided a print head for a continuous inkjet printer, comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; and a heating element for drying the print head. The print head may be a self-cleaning print head. The print head may comprise a cleaning chamber, optionally selectively sealable by a sealing mechanism. The at least one electrode may be disposed in the chamber. The heating element may be described as a local heating element by virtue of being provided in the print head. The heating element may be an always-on heating element. Put another way, the heating element may be maintained at a given temperature throughout the operational life of the print head, not just when a drying cycle is initiated. Advantageously, the heating element provides a drying effect for drying at least part of the print head (e.g. for evaporation of cleaning fluid). The heating element may be described as a chamber drying heating element. The heating element may comprise one or more of: an ink heater; a nozzle body, which defines the nozzle; the charge electrode; a low voltage electrode; and a deflection electrode. 69726509-2 Where the heating element is constituted by the nozzle body, charge electrode, low voltage electrode or deflection electrode, existing components of the print head can be _{utilised in order to provide heating effect. This may take the form of providing one or} more of these components with a power supply so as to increase the temperature of these components to achieve a heating effect. The ink heater may be described more generally as a fluid heater. The ink heater may otherwise be used to control a temperature of the ink (e.g. to control a viscosity thereof) at, or upstream of, the nozzle body. Specifically, the ink heater can be used to heat the ink, increasing the viscosity of the ink. In some embodiments the ink heater may be coupled to the nozzle body. This may be described as a nozzle heater, or a nozzle body heater. The nozzle body can thus be heated in different ways. Where the nozzle body is used as the heating element, the nozzle body can be provided with power to increase the temperature of the nozzle body (and provide a heating effect). Where the ink heater is coupled to the nozzle body, the nozzle body may be heated by activation of the ink heater (e.g. heated by conduction). For either option, the nozzle body can then transfer heat to fluid passing through the nozzle body (and so nozzle), and/or heat other components in thermal communication with the nozzle body, to provide a drying functionality. Using the ink heater provides further options for heating the print head to dry the print head. The ink heater may be a resistive heater. The heating element may comprise a resistive heater. Resistive heater is intended to mean a dedicated component which increases in temperature upon application of a power supply. In its simplest form a resistor is a form of a resistive heater. The resistive heater may be a PTC (positive temperature co-efficient of resistance) heater, which is a safe heater. That is to say, the resistance is linked to temperature, and this form of heater is therefore prevented from overheating. Advantageously, the resistive heater provides a dedicated component by which a heating effect can be obtained. 69726509-2 The print head may comprise a cleaning the at least one electrode disposed in the cleaning chamber. The cleaning chamber may otherwise be described as an enclosed volume. The cleaning chamber is preferably selectively sealable by a sealing mechanism. The use of a heating element in such a self-cleaning print head is particularly advantageous because the enclosed volume can prove challenging to dry. Providing the heating element can thus increase the speed and efficiency of drying, desirably reducing an overall cleaning cycle time. The cleaning chamber may be at least partly defined by one or more walls of a chamber housing, and wherein the heating element is coupled to the one or more walls. The heating element being coupled to the one or more walls may be described as the heating element being provided in conductive thermal communication with the one or more walls. The heating element may be directly coupled to the one or more walls, or may be indirectly coupled. Advantageously, coupling the heating element to the one or more walls which define the cleaning chamber provides a direct heating effect, via conduction, to the chamber. The chamber, and components disposed therein, can thus be dried more swiftly. The one or more walls may comprise a reduced thickness proximate the heating element. The one or more walls comprising a reduced thickness proximate the heating element may be described as a narrowing of the one or more walls in at least a region of the heating element. This is desirable for the reason that a comparatively thinner wall provides a better conductive thermal pathway for heating the chamber. The cleaning chamber may be at least partly defined by a chamber housing, the chamber housing being manufactured from a thermally conductive plastic. 69726509-2 Thermally conductive plastic is to mean a plastic which is doped with a thermally conductive material to improve the thermal conductivity of the plastic. One example of this is aluminium nitride, which can be doped into a plastic to improve the thermal conductivity, but not increase the electrical conductivity, of the plastic. It is desirable to maintain a poor electrical conductivity to avoid issues with the shorting of electrodes, and other components, within the chamber. The heating element may comprise an infrared LED. The heating element may comprise a plurality of infrared LEDs. Advantageously, when power is supplied the infrared LED emit rays of infrared light. These provide a drying effect by way of radiation. Infrared LED are advantageously a low cost heating option which could be readily incorporated around the chamber. For example, the print head may comprise a plurality, or an array, of infrared LEDs. The print head may comprise a cleaning chamber, the at least one electrode may be disposed in the cleaning chamber. The print head may further comprise a low voltage electrode, and the cleaning chamber _{may be at least partly defined by the low voltage electrode.} The low voltage electrode may cooperate with a deflection electrode (e.g. a high voltage electrode) to facilitate directional control of charged ink droplets in use. The deflection electrode may be disposed in the cleaning chamber. A first face of the low voltage electrode may be exposed to the cleaning chamber. Described another way, the first face of the low voltage electrode may define at least part of a wall of the cleaning chamber. The first face of the low voltage electrode may be described as defining part of a boundary of the cleaning chamber. Advantageously, the first face of the low voltage electrode being exposed to the cleaning chamber provides a direct thermal pathway to the chamber. Drying is therefore more effective. Heat transfer is also improved by virtue of the comparatively large surface area of the low voltage electrode. 69726509-2 The resistive heater may be thermally to the low voltage electrode. Described another way, the low voltage electrode may be (directly) heated by the resistive heater (e.g. by conduction). The low voltage electrode may define a conductive thermal pathway between the resistive heater and the cleaning chamber. Advantageously, the low voltage electrode acts as a thermal bridge between the resistive heater and the cleaning chamber. Heat is readily transferred from the resistive heater to the cleaning chamber (via the low voltage electrode) to swiftly dry the cleaning chamber and components therein. The resistive heater does not need to be disposed in the cleaning chamber, where space is limited. Furthermore, the resistive heater, and optionally other components coupled to the low voltage electrode, can be shielded from exposure to the operation of the cleaning chamber (e.g. cleaning fluid, ink etc.). The conductive thermal pathway means heat is transferred at a faster rate than, for example, a convective heat transfer pathway. _{According to a second aspect of the invention there is provided a continuous inkjet printer} comprising: a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; further comprising a heating element for drying the print head. The print head may be in accordance with the first aspect of the invention. The heating element may be disposed in the printer body. Alternatively, the heating element may be disposed in the print head. Further alternatively, the heating element may be disposed somewhere along the umbilical. 69726509-2 The print head may be a self-cleaning print head. The print head may comprise a cleaning chamber, optionally selectively sealable by a sealing mechanism. The at least one electrode may be disposed in the chamber. Advantageously, the heating element provides a drying effect for drying the print head, reducing the cycle time of a cleaning cycle. The heating element may be a resistive heater. One or more of the printer body and the print head may comprise the heating element. The printer body may comprise the heating element, and wherein the heating element is provided in thermal communication with a fluid conduit in the printer body. The heating element being provided in thermal communication with a fluid conduit in a printer body is intended to mean that the heating element can heat fluid in the fluid conduit. Described another way, the heating element provides thermal energy to increase a thermal mass of fluid in the fluid conduit. This may be by way of a heat exchanger. The fluid may be a gas, such as air. Alternatively, the fluid may be liquid, such as cleaning fluid. Advantageously, increasing the temperature of the fluid, which is subsequently provided to the print head, provides a convective heating effect to the print head and improves the drying of the print head. The heating element may be a Peltier device. A Peltier device is an example of a thermoelectric cooling device. Upon receipt of a current, the Peltier device moves heat from a warm side of the device to a cold side of the device. Providing fluid in thermal communication with a warm side of the Peltier device can therefore provide a heating effect to the fluid. Furthermore, in instances where a dehumidified fluid is to be supplied to the print head, the Peltier device can also be used. For example, the fluid can first be passed across a cool side of the Peltier device, to reduce the moisture content of the fluid (e.g. to dry the fluid). Subsequently, 69726509-2 the dried fluid can be passed across the side of the Peltier device to warm the fluid. This increases the fluid to be able to absorb fluid. Advantageously, the Peltier device is a readily available heating element that can be used to provide heating effect upon supply of power. Furthermore, for the reasons previously mentioned, the Peltier device can advantageously provide a dehumidifying effect. According to a third aspect of the invention there is provided a wash station for a print head, comprising: a housing for receiving the print head; and a heating element for drying the print head. The heating element may be a resistive heater. The heating element may be a Peltier device. _{According to a fourth aspect of the invention there is provided a method of cleaning a} print head of a continuous inkjet printer, comprising: providing a supply of cleaning fluid to the print head; and heating at least part of the print head to dry the print head. The method of cleaning a print head may be carried out by a printer, or by a wash station. The print head may be a self-cleaning print head. Providing a supply of cleaning fluid to the print head may comprise at least partially filling a chamber of a self-cleaning print head with cleaning fluid, or providing a spray of cleaning fluid for a wash station. Heating at least part of the print head to dry the print head may comprise heating a chamber of the print head. Heating at least part of the print head may comprise heating a specific component within the print head. Advantageously, providing a supply of cleaning fluid provides a cleaning effect, and heating at least part of the print head subsequently dries the print head. The print head can thus be cleaned, and subsequently dried, such that the cycle time can be reduced. Heating at least part of the print head may comprise activating a heating element. 69726509-2 Activating a cleaning element may otherwise be described as powering on, or providing a power supply to, a heating element. Activating the heating element may comprise activating a resistive heating element, or an infrared LED, to name two examples. In some embodiments, the heating element may be an always-on heating element. That is to say, a temperature may be maintained at a substantially constant level within the print head. This has also been found to desirably improve a dehumidifying performance within the print head. Alternatively, the heating element may activated responsive to initiation of a drying step of a cleaning cycle. Activating the heating element may comprise activating a heating element disposed in the print head. Advantageously, activating the heating element disposed in the print head provides a more direct heating effect, possibly by way of conduction, for drying the print head. Activating the heating element may comprise activating a resistive heater that heats a cleaning chamber of the print head. Activating the resistive heater may comprise heating a low voltage electrode thermally coupled to the resistive heater. The low voltage electrode may define at least part of the cleaning chamber, and heating the low voltage electrode may heat the cleaning chamber to dry the cleaning chamber. The method may further comprise ramping the heating element to a target temperature _{based upon one or more input variables, the one or more input variables optionally} comprising one or more ambient conditions such as temperature and/or humidity. Advantageously, the heating element response can be adjusted based upon one or more input variables. For cooler ambient conditions (for example), the heating element can be controlled to reach a target temperature more swiftly (e.g. a sharper, or steeper, ramp). For warmer ambient conditions (for example), the heating element can be controlled to _{reach a target temperature more gradually (e.g. a shallower ramp). Ambient conditions} 69726509-2 may comprise one or more of humidity, ink temperature, and cleaning fluid _{temperature. The ramping may be executed, or controlled, by a controller. The controller} may form part of a low voltage electrode assembly. Activating the heating element may comprise activating a heating element disposed in a printer body of the continuous inkjet printer, the heating element heating a fluid flowing from the printer body to the print head. Advantageously, activating a heating element disposed in the printer body means that the print head can be reduced in size in comparison to the heating element being incorporated in the print head. Heating the fluid flowing from the printer body to the print head may comprise heating one or more of a flow of cleaning fluid and a flow of air. Heating one or more of a flow of cleaning fluid and a flow of air is desirable for the reason that both fluids are already present and available in the printer body. Furthermore, the printer architecture provides a flow path, by way of the fluid conduits in the umbilical, to be able to transfer the fluids from the printer body to the print head. These fluids can therefore act as a transport medium for the thermal energy from the heating element. _{According to a fifth aspect of the invention there is provided a method of cleaning a print} head of a continuous inkjet printer, comprising: providing a supply of cleaning fluid to the print head; and drying the print head by one or more drying actions. The drying action may comprise activating a gutter pump. The drying action may comprise opening a sealing mechanism of the print head and exposing a chamber of the print head to atmosphere. The drying action may comprise providing a plurality of bursts of fluid flow to the print head. The drying action may comprise directing a supply of fluid to targeted components of the print head. The drying action may comprise providing an unstable fluid flow. The drying action may comprise providing a supply of drying fluid from a canister or factory air supply. The drying action may comprise providing a supply of dehumidified fluid. The drying action may comprise activating a nozzle, of the print 69726509-2 _{head, and ejecting a fluid stream to draw fluid through the print head. The} drying action may comprise a plurality of the above drying actions. The method of cleaning a print head of a continuous printer may be carried out by a printer or by a wash station. The print head may be a self-cleaning print head. Activating the gutter pump preferably occurs after a sealing mechanism of a self-cleaning print head has been closed. Activating the gutter pump acts to reduce the pressure within a cleaning chamber, improving the drying. Opening the sealing mechanism and exposing a chamber of the print head to atmosphere advantageously reduces a back pressure generated by pumping fluid through the print head. Air, for example, can thus be pumped into the print head with reduced wear on the pump. The drying effect can thus be improved accordingly. Providing a plurality of bursts of fluid flow is intended to refer to a periodic supply of gas. The cyclical nature of the bursts provides a greater pressure drop and corresponding velocity gradient, which has been found to provide an improved drying effect. Directing a supply of fluid to targeted components of the print head may otherwise be described as selective drying of components of the print head. Where there are particular components, or regions, of the print head which are liable for cleaning fluid to build up, and so difficult to dry, these can be targeted. This may occur by way of ports being positioned to direct fluid at certain components, or regions of the print head, and those ports being selectively placed in fluid communication with an air supply (e.g. an air pump). Providing an unstable fluid flow is intended to mean an irregular fluid flow, or an erratic flow, which has been found to provide an improved drying effect. One way in which an unstable fluid flow can be generated is by the use of a compliant membrane, such as a duckbill. As the fluid flows across the membrane, the membrane deforms so as to redirect the fluid e.g. in the form of a sail. Providing a supply of drying fluid from a canister may comprise providing a supply of gas, such as nitrogen, carbon dioxide or dry air. The canister may be described as a 69726509-2 consumable. Alternatively, providing a of drying fluid from a factory air supply may comprise a supply of compressed air being provided (e.g. through a factory air-line). Either option provides for the supply of an alternative gas to standard air, which has been found to provide an improved drying effect. A supply of dehumidified fluid refers to a fluid supply which has a reduced moisture level. Put another way, the moisture level within the fluid has been reduced before it is supplied. This can be achieved by selectively passing a flow of air over a Peltier device so as to dehumidify the air before it is supplied (to name one example). Dehumidified fluid has an improved drying effect owing to its improved ability to absorb liquid (e.g. facilitating evaporation of liquid from the chamber). Activating a nozzle of the print head and ejecting a fluid stream there from to draw fluid through the print head may otherwise be described as activating a nozzle to provide a first fluid stream, and using that first fluid stream to entrain, or draw, a further fluid stream through the print head. For example, if the nozzle is activated so as to provide a jet of ink, running the nozzle to provide the jet of ink will draw other fluid, such as air, through the chamber so as to provide a drying effect. The stream of fluid ejected from the nozzle may comprise ink or cleaning fluid. _{According to a sixth aspect of the invention there is provided a continuous inkjet printer} comprising: a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; a controller in electrical communication with the print head; the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the controller is configured to, upon initiation of a drying step of a cleaning cycle, implement one or more drying actions. 69726509-2 The controller may be configured to a gutter pump, in the printer body, to draw fluid through the gutter in the print head. The controller may be configured to open a sealing mechanism of the print head to expose a chamber of the print head to atmosphere. The controller may be configured to provide a plurality of bursts of fluid flow. The controller may be configured to direct a supply of fluid to targeted components of the print head. The controller may be configured to provide an unstable fluid flow. The controller may be configured to provide a supply of drying fluid from a canister or factory air supply. The controller may be configured to provide a supply of dehumidified fluid. The controller may be configured to activate the nozzle to generate and eject a fluid _{stream to draw fluid through the print head. The controller may be configured to} implement a plurality of the aforementioned drying actions. The print head may be a self-cleaning print head. The print head may comprise a cleaning chamber, optionally selectively sealable by a sealing mechanism. The at least one electrode may be disposed in the chamber. _{According to a seventh aspect of the invention there is provided a continuous inkjet} printer comprising: a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; a controller in electrical communication with the print head; the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; further comprising a compliant membrane, disposed along a fluid flowpath between the printer body and the print head, for generating an unstable fluid flow in the print head. _{According to an eighth aspect of the invention there is provided a continuous inkjet printer} comprising: 69726509-2 a printer body comprising an ink for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; and a controller in electrical communication with the print head; the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the controller is configured to: initiate a drying control mode; and supply the deflection electrode with a supply voltage. The drying control mode refers to a control mode of the deflection electrode. This may be described as reducing the sensitivity, or entirely disabling, a typical deflection electrode trip response in the printer. Initiating a drying control mode may otherwise be described as not shutting down the printer if a deflection electrode short is detected. The controller being configured to supply the deflection electrode with a supply voltage may be described as the controller placing the deflection electrode in power communication with a supply voltage, preferably from a power supply (e.g. a high voltage power supply, such as 8 kilovolts). Advantageously, initiating the drying control mode and supplying the deflection electrode with a supply voltage can be used to run one or both of a drying step of a cleaning cycle, and a dryness test. The controller may be configured to initiate a drying step of a cleaning cycle. The drying step of a cleaning cycle takes place by virtue of the supply of the deflection electrode with a supply voltage. Any lingering cleaning fluid is electrostatically _{atomised/dispersed, in the form of webs, from the deflection electrode and through any} local grounds. This effectively vaporises the cleaning fluid and prevents the cleaning 69726509-2 fluid from providing a shorting path in a cycle. Put another way, the region between the deflection electrode and the ground electrode is dried. Advantageously, this can be used to remove cleaning fluid lingering from a cleaning cycle and place the printer, more readily, in a printing-ready state (e.g. being dry). The controller may be configured to: initiate a dryness test; supply the deflection electrode with a supply voltage; receive a signal from the deflection electrode; and process the signal to determine whether a dryness of a region between the deflection electrode and the low voltage electrode falls within an acceptable range. Initiating a dryness test may be described as running a pre-printing dryness check. The deflection electrode is preferably provided with a full supply voltage, such as 8 kilovolts in some examples. The signal received from the deflection electrode may be a voltage reading across a resistor in the printer body. Said reading may be indicative of a state of the deflection electrode. Processing the signal may be described as processing an electrical response of the deflection electrode. The dryness of a region between the deflection electrode and the low voltage electrode may refer to walls of a chamber for a self-cleaning print head. The dryness falling with an acceptable range may refer to an absolute dryness (e.g. the absence of any liquid). Alternatively, a dryness falling within an acceptable range may not be entirely dry (i.e. there may still be some cleaning fluid present) but at a level sufficiently low that printing can be carried out. Dryness of a region between the deflection electrode and the low voltage electrode falling within an acceptable range may comprise the region being dry enough that a deflection electrode voltage is supported. Dryness of a region between the deflection electrode and the low voltage electrode falling within an acceptable range may comprise the region being dry enough that the stream of ink droplets (e.g. jet) is not interfered with (e.g. including the deflected drop trajectory, when droplets are used for printing). Dryness of a charge electrode falling within an acceptable range may comprise the charge electrode being dry enough not to be loaded by wetness. 69726509-2 A dryness of the chamber, and optionally any component disposed within the chamber, falling within an acceptable range may comprise there being no liquid drips when a sealing mechanism is opened. Advantageously, the dryness test can be used to determine whether the dryness stage is completed and whether the print head is safe to operate. This could be used to shorten a cleaning cycle (e.g. to avoid unnecessary additional time spent during the drying phase). Alternatively, the dryness test could be used to extend the drying phase where necessary (e.g. run a subsequent drying cycle, if it is determined the dryness does not fall within an acceptable range). If the dryness of a region between the deflection electrode and the low voltage electrode falls outside of the acceptable range, the controller may initiate a drying step of a cleaning cycle. Should the dryness of a region between the deflection electrode and the low voltage electrode fall outside of an acceptable range, this may be described as a failed dryness test. In response, the controller may initiate a drying step of a cleaning cycle so as to improve this failed dryness reading. This could take the form of repeating a dryness step, or, if the dryness test occurs mid-drying, extending a drying stage (e.g. drying the print head for a longer period of time). Advantageously, the dryness test can thus form a feedback loop in which drying steps can be repeated until the dryness test is passed which confirms the print head is dry and ready for printing. _{According to a ninth aspect of the invention there is provided a method of using a print} head of a continuous inkjet printer, comprising: initiating a drying control mode; and supplying a deflection electrode of the print head with a supply voltage. The method may be a method of drying the print head. 69726509-2 The method may be a dryness testing for determining whether a print head of a continuous inkjet printer is dry, the method further comprising: monitoring an electrical response of the deflection electrode over time; and determining whether a dryness of a region between the deflection electrode and the low voltage electrode falls within an acceptable range, based upon the electrical response of the deflection electrode. Monitoring an electrical response of the deflection electrode over time may comprise monitoring a voltage drop and/or current drawn by the deflection electrode. If the full supply voltage is not reached by the deflection electrode, this implies a grounding issue in that cleaning fluid is still present. An alternative way of detecting this is to observe a current draw, which also indicates that a short is occurring. If the dryness of the region between the deflection electrode and the low voltage electrode falls outside of the acceptable range, a drying step of a cleaning cycle may be initiated. _{According to a tenth aspect of the invention there is provided a method of cleaning a} print head of a continuous inkjet printer, comprising: providing a supply of cleaning fluid to the print head; and drying the print head; wherein one or more parameters of the method are determined responsive to one or more input variables. The input variable may comprise an orientation of the print head. The input variable may comprise an ambient condition. The input variable may comprise a type of ink and/or cleaning fluid. The input variable may comprise a dimension of a fluid flowpath of the printer. The input variable may comprise a cleaning and/or shutdown history of the print _{head and/or printer. The input variable may comprise a plurality of the aforementioned} input variables. The method of cleaning a print head may be carried out by a printer or by a wash station. The print head may be a self-cleaning print head. 69726509-2 The one or more parameters of the may be determined before the method of cleaning begins, or alternatively may be determined after initiation of the method (e.g. on the fly). The orientation of the print head refers to a position of the print head in space. Certain orientations of the print head have been found to be more challenging to dry than others, and so for certain orientations of print head a longer drying stage, for example, may be used. Ambient conditions include temperature and humidity. In certain ambient conditions the drying stage of the print head in the cleaning cycle may be varied so as to provide a greater certainty that the print head is dry. For example, where the print head is used in cooler ambient conditions (e.g. lower temperatures, such as a refrigerated printing line) it may be more challenging to dry the print head using a standard baseline cycle. It may therefore be desirable to modify the cleaning method to provide a more reliable drying step in some conditions. The type of ink and/or cleaning fluid can also have an effect on how effective a baseline cleaning method is. For example, certain inks, including resins, may be comparatively difficult to wash from internal components of the print head. Similarly, certain cleaning fluids, such as solvents like MEK, may require a longer drying time. It may therefore be advantageous for the input variables of type of ink and/or cleaning fluid to affect one or _{more of the drying and cleaning fluid supply stages of the cleaning method. The ability} of an ink (e.g. dye/resin) to redissolve, and/or the speed of dissolving, may be factors which affect how difficult it is to wash the ink from internal components of the print head. Dimensions of fluid flow paths of the printer include a fluid conduit length (e.g. a length of at least the umbilical) and a nozzle diameter. These have an effect on the choke points within the printer (e.g. liable to block due to ink build up) and/or surface areas along which ink sediment is most likely to dry. Longer fluid conduits, and smaller nozzles, are more likely to necessitate a deeper cleaning cycle. The cleaning and/or shutdown history of the printer head and/or printer may be stored in a memory on board the printer. Accordingly, it is possible to review how regularly the printer has been cleaned, for example, and whether the last shutdown, or last few 69726509-2 shutdowns, occurred successfully (e.g. incorporating a cleaning cycle). Should a printer be regularly serviced, and shutdown be successful, a baseline cleaning method may be sufficient to maintain the printer. Alternatively, if a previous cleaning history is not as would be expected, or should one or more previous shutdowns have been unsuccessful, a deeper clean may be necessitated. Advantageously, the aforementioned method provides a feedback in which one or more parameters of the method are modified in response to one or more input variables. These can provide greater certainty that the cleaning method will provide a clean print head, but also avoid, or reduce, the risk that a cleaning cycle continue for an unnecessarily long period of time (e.g. when not required). _{The method of cleaning may occur at start-up.} Advantageously, where the method of cleaning occurs at start-up, the start-up cleaning cycle can be responsive to the, for example, nature of the previous shut down. The method can be provided efficiently and on the basis of, for example, the previous cleaning cycle and/or shutdown history. The one or more input variables may be automatically detected. The one or more input variables being automatically detected may be detected by way of one or more sensors or from data read from a chip (e.g. of an ink and/or solvent cartridge) to name some examples. Advantageously, the automatic detection means that the method can be modified in a more streamlined manner, not requiring operator intervention. The one or more input variables may be manually input. The one or more input variables being manually input may be input by an operator through a control panel of the printer body. 69726509-2 Advantageously, the one or more can be manually input where the variables may be challenging to detect automatically. For example, a type of ink and/or cleaning fluid or one or more dimensions of a fluid flow path of the printer. _{A baseline cleaning method may be used for one or more input variables falling within a} baseline range. The baseline cleaning method may otherwise be described as a standard cleaning method. The standard cleaning method may be used when an input parameter falls within a baseline range. This may be described as one or more, or all, of the input variables falling within a baseline range. The baseline range may be a recommended range of operation for the printer. The baseline cleaning method may be a cleaning method where a reliable clean can be expected based upon the (one or more) input parameters falling within the baseline range. The baseline range may refer to a numerical range (e.g. a temperature falling between 20° and 40°) or may refer to a number of discrete data points (for example, the type of ink falling within a comparatively easily cleaned variety). A baseline cleaning method may be used where no input variables fall within a deep clean range. That is to say, a baseline cleaning method may be used where all input variables fall within a light clean range or a baseline range. _{A deep cleaning method may be used for one or more input variables falling within a} deep clean range. The deep cleaning method may be modified relative to the baseline method in a number of different ways. Longer cycle times, further steps, modified steps, and/or repeated sub- _{cycles or entire cycles are just some ways in which the parameters of the method can} be modified for a deep clean method. One or more input variables falling within the deep clean range may be described as one or more of the input variables being indicative that the printer will need a more intensive cleaning cycle than the baseline cleaning method. Put another way, one or more input variables falling within the deep clean range may indicate that the baseline cleaning 69726509-2 method may not provide a reliable (for example, a cleanliness level in a predetermined cycle time). Advantageously, providing a deep cleaning method where an input variable falls within a deep cleaning range ensures that the printer, and print head, remain clean even when the input variables present challenging conditions. This can avoid unnecessary and costly downtime, and/or excessive cycle times and/or unreliable cleaning. A deep cleaning method may be used where any one input variable falls within a deep clean range. Alternatively, a deep cleaning method may be used when a plurality of input variables (e.g. all input variables, or a subset of input variables) fall within a deep clean range. _{A light cleaning method may be used for one or more input variables falling within a light} clean range. A light cleaning method refers to a cleaning method which is less intensive than the baseline method. The light cleaning method may be a shorter method, having fewer steps, and fewer, or no, repetitions of sub-cycles or entire cycles. An input parameter falling within a light clean range may be indicative that the printer does not require even a baseline cleaning method because the conditions are favourable to the cleaning. For example, if the printer has been regularly cleaned, ambient conditions fall within a recommended range, none of the printer geometry represents a particular cleaning difficulty, and the type of ink and cleaning fluid are readily cleaned. A light cleaning method may be used where no input variables fall within a baseline or deep clean range. That is to say, a light cleaning method may be used where all input variables fall within a light clean range. _{The ambient condition may comprise temperature. The ambient condition may comprise} humidity. The ambient condition may comprise ink temperature. The ambient condition _{may comprise cleaning fluid temperature. The ambient condition may comprise a} plurality of the aforementioned ambient conditions. 69726509-2 Advantageously, modifying the based upon temperature and humidity, optionally ink and cleaning fluid temperature, provides a cleaning method which corresponds to the method necessitated by these conditions. These input variables have been found to have the most profound effect upon the efficacy of cleaning. _{The dimension of a fluid flowpath of the printer may comprise a length of a fluid conduit} extending between a printer body and the print head. The dimension of a fluid flowpath _{of the printer may comprise a diameter of a nozzle of the print head. The dimension may} comprise a plurality of the aforementioned dimensions. The dimension of the fluid flow path of the printer may be one of a number of different dimensions. One example of such a dimension is a length of a fluid conduit extending between a printer body and the print head. The length of the fluid conduit, in embodiments incorporating an umbilical, may be at least as long as the umbilical. The length of fluid conduit is indicative of a distance along which fluid from the printer body has to travel to reach the print head. A longer line may be more susceptible to the drying of ink, for example, which can necessitate a deeper cleaning cycle. Another such dimension that can have an effect on the cleaning cycle is a diameter of a nozzle of the print head. The nozzle is the aperture through which fluid, such as ink droplets, is ejected from the nozzle body. The nozzle diameter may represent a greatest constriction (i.e. throat) within the printer. The nozzle can therefore be liable to blockage _{by the build-up of ink and other deposits. A smaller diameter of nozzle may be more} susceptible to blockages, and may therefore necessitate a deeper cleaning cycle. Advantageously, for the reasons set out above, adjusting one or more parameters of a cleaning method responsive to fluid dimensions of a fluid flow path of the printer reduces the risk of blockages and provides for a more efficient cleaning cycle. The cycle thus has regard to a scale of the printer and associated geometry. Determining one or more parameters of the method responsive to a cleaning and/or _{shutdown history of the print head and/or printer may comprise analysing data entries} corresponding to one or more previous cleaning cycles, and determining whether the one or more previous cleaning cycles fall within an acceptable range. Determining one or more parameters of the method responsive to a cleaning and/or shutdown history of 69726509-2 the print head and/or printer may analysing data entries corresponding to the previous shutdown cycle, and determining whether the previous shutdown cycle falls _{within an acceptable range. Determining one or more parameters may comprise both of} the aforementioned determination options. A cleaning and/or shutdown history of the print head and/or printer refers to previous cleaning cycles and previous power down cycles which the printer and print head have undergone. For a print head with a history of regular, successful cleans, this could negate the need for a deep cleaning cycle. Put another way, regular servicing of the printer can mean that a deep cleaning cycle may not be needed. Similarly, where a previous shutdown history of the printer has generally occurred successfully, and optionally incorporating a cleaning cycle, the use of a deep cleaning cycle on start-up may not be needed. Alternatively, where a previous shutdown has not been completed in accordance with protocol (e.g. a power cord having been pulled by an operator, not allowing for a typical shut down cycle to complete), a deeper cleaning method may be needed in order to prepare the printer for printing. The analysis can take one of a number of different forms. For example, reviewing the previous cleaning cycles of the printer, which may comprise analysing data entries corresponding to one or more previous cleaning cycles. This may be carried out by the controller. Data corresponding to the previous cleaning and shut down cycles is preferably written to a memory by the printer. The analysis of these data entries may then comprise determining whether one or more previous cleaning cycles fall within an acceptable range. Determining whether one or more previous cleaning cycles fall within an acceptable range may comprise determining whether one or more previous cleaning cycles completed successfully. Determining whether one or more previous cleaning cycles fall within an acceptable range may comprise determining whether one or more previous cleaning cycles occurred in accordance with a recommended schedule of cleaning. Determining whether one or more previous cleaning cycles fall within an acceptable range may comprise determining whether one or more previous cleaning cycles falls within a light, baseline or deep clean range. 69726509-2 The analysis may alternatively data entries corresponding to the previous shut down cycle. Determining whether the previous shut down cycle falls within an acceptable range may comprise determining whether the previous shut down occurred in accordance with recommended protocol. Determining whether the previous shut down cycle falls within an acceptable range may comprise determining whether a cleaning cycle corresponding to a shut down cycle occurred successfully. Determining whether the previous shut down cycle falls within an acceptable range may comprise determining whether the previous shut down cycle falls within a light, baseline or deep clean range. Advantageously, determining one or more parameters of the method responsive to a cleaning and/or shutdown history of the print head provides for reliable operation of the printer combined with efficiency of cleaning. The one or more parameters of the method may comprise an amount of cleaning fluid supplied to the print head. The one or more parameters of the method may comprise a time period during which cleaning fluid is supplied to the print head. The one or more parameters of the method may comprise a time period for drying the print head. The one or more parameters of the method may comprise a drying method for drying the print head. The one or more parameters of the method may comprise a number of repeat cycles for the providing a supply of cleaning fluid to the print head and/or drying the print head steps. The one or more parameters of the method may comprise a number of repeat cycles of the method of cleaning the print head. The one or more parameters may comprise a plurality of the aforementioned parameters. There are a number of different parameters of the method which can be determined in response to the input variables. An amount of cleaning fluid supplied to the print head refers to a liquid volume of cleaning fluid supplied to the print head during the providing a supply of cleaning fluid step. In some embodiments, this may comprise the amount of cleaning fluid supplied through the print head (e.g. for a self-cleaning print head) or an amount of cleaning fluid sprayed onto the print head (e.g. for a wash station). An amount of cleaning fluid supplied to the print head is preferably greater for a deep cleaning cycle than for a light cleaning cycle. 69726509-2 A time period during which cleaning supplied to the print head may refer to a period of time for which the providing cleaning fluid to the print head step occurs. Fluid may be supplied to the print head for less time when a light cleaning method is used, and for more time when a deep cleaning method is used. A time period for drying the print head refers to a period of time over which the drying the print head stage occurs. The print head may be dried for a longer period of time in a deep cleaning cycle, and for less time in a light cleaning method. The method used for drying the print head may also be modified. This includes modifying a drying power (e.g. where a resistive heater is used, a greater temperature may be reached by the heater) or by incorporating one or more alternative drying methods (e.g. activating a _{gutter pump to reduce a pressure within the print head) to improve drying time. The} _{method used for drying the print head may also be modified by modifying a ramp} response of a heating element (e.g. such that a heating element reaches a target temperature more quickly). A number of repeat cycles for the providing a supply of cleaning fluid step and/or the drying the print head may also be modified. For example, for a deeper cleaning method the number of cycles of supplying the cleaning fluid may be increased. Finally, a number of repeat cycles of the overall method of cleaning the print head may be modified. For example, for a deeper cleaning method the overall method may be run multiple times. Alternatively, for a lighter cleaning method the method may only be run once, and optionally each step for a reduced period of time in contrast to a baseline cycle. Advantageously, determining one or more parameters of the method in accordance with the above means that the cycle time may be reduced desirably while still providing a high quality of clean. _{The method may further comprise a soaking stage which precedes the drying of the print} head. The one or more parameters of the method may comprise a time period over which the soaking stage occurs. The one or more parameters of the method may comprise agitating the cleaning fluid during the soaking stage. The one or more parameters may comprise a plurality of the aforementioned parameters. 69726509-2 The method further comprises an optional soaking stage. The soaking stage may be referred to as a dwell stage in which cleaning fluid remains applied to the print head and/or constituent components within. For example, for a self-cleaning print head the soaking stage refers to a dwell period in which the chamber remains at least partially filled with cleaning fluid. For a wash station, the soaking stage may refer to a stage during which cleaning fluid again remains applied to the print head within the wash station, before the drying step takes place. The soaking stage allows time for the cleaning fluid to act upon the deposits and build-ups on the print head. A number of variables associated with the soaking stage can be adjusted. One of these is a time period over which the soaking stage occurs. For a deeper cleaning method a comparatively greater time period may be used for the soaking stage. Where only a lighter clean is needed, the time period of soaking may be comparatively reduced. A further parameter of the method, associated with the soaking stage, which can be modified is the optional incorporation of agitation. Agitation refers to the movement of cleaning fluid, by way of: percolating air or other gas through a chamber, for example; and/or mechanical vibration of the print head. Agitation increases the ability of the cleaning fluid to remove deposits from the print head. Where a comparatively deeper clean is needed, the incorporation of agitation may be desirably used. Alternatively, where only a better clean is needed, the agitation may be omitted. Advantageously, incorporation of a soaking stage provides for an improved efficiency clean. Determination of one or more parameters associated with the soaking stage can improve the efficiency of cleaning whilst providing a desirable efficiency of the cleaning cycle. _{According to an eleventh aspect of the invention there is provided a continuous inkjet} printer comprising: a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; and a controller in electrical communication with the print head; 69726509-2 the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the controller is configured to determine one or more parameters of a method of cleaning the print head responsive to one or more input variables. The one or more input variables may comprise an orientation of the print head. The one or more input variables may comprise an ambient condition. The one or more input variables may comprise a type of ink and/or cleaning fluid. The one or more input variables may comprise a dimension of a fluid flowpath of the printer. The one or more input variables may comprise a cleaning and/or shutdown history of the print head and/or _{printer. The one or more input variables may comprise a plurality of the aforementioned} input variables. The print head may be a self-cleaning print head. The print head may comprise a cleaning chamber, optionally selectively sealable by a sealing mechanism. The at least one electrode may be disposed in the chamber. The one or more input variables may be determined by a sensor in electrical communication with the controller. The one or more input variables may be read from data stored on a chip of an ink and/or solvent cartridge. The one or more input variables may be input via an interface panel of the printer body, the interface panel in electrical communication with the controller. The one or more input variables may be read from a memory of the printer. A sensor in electrical communication with the controller may comprise a temperature sensor, such as a thermocouple, and/or a humidity sensor and/or an orientation sensor. Where input variables are read from data stored on a chip of an ink and/or solvent cartridge, the data is preferably indicative of the type of ink and/or solvent in the cartridge. _{When the cartridge is connected to a corresponding connector in the printer body, an} 69726509-2 electrical connection is preferably made which the data on a smart chip can be read. This can provide an automatic indication of the type of ink and/or solvent in the system. The interface panel of the printer body may be a touch screen or other control panel. Through this interface panel an operator, for example, may manually input one or more input variables associated with the printer. These include any one or more of a type of cleaning cycle, one or more ambient conditions, an orientation of the print head, a type _{of ink and/or cleaning fluid, a dimension of a fluid flow path of the printer, and/or a} shutdown history of the printer. Where the input variables are read from the memory of the printer, this preferably refers to a cleaning and/or shutdown history of the print head and/or printer. It will be appreciated that one or more of the aforementioned input variable determination methods may be automatic (e.g. not requiring an operator input) and/or manually determined (e.g. input by an operator). Advantageously, determining one or more input variables based on the above methods can provide for reliable reading of the input variables in a convenient manner for an operator. The one or more parameters may comprise an amount of cleaning fluid supplied to the print head. The one or more parameters may comprise a time period during which cleaning fluid is supplied to the print head. The one or more parameters may comprise a time period for drying the print head. The one or more parameters may comprise a drying method for drying the print head. The one or more parameters may comprise a number of repeat cycles for the providing a supply of cleaning fluid to the print head and/or drying the print head steps. The one or more parameters may comprise a number of repeat cycles of the method of cleaning the print head. The one or more parameters may comprise a plurality of the aforementioned parameters. _{According to twelfth aspect of the invention there is provided a wash station for a print} head, comprising: a housing for receiving the print head; and 69726509-2 a controller, wherein the is configured to determine one or more parameters of a method of cleaning the print head responsive to one or more input variables. The one or more input variables may comprise an orientation of the print head. The one or more input variables may comprise an ambient condition. The one or more input variables may comprise a type of ink and/or cleaning fluid. The one or more input variables may comprise a dimension of a fluid flowpath of the printer. The one or more input variables may comprise a cleaning and/or shutdown history of the print head and/or _{printer. The one or more input variables may comprise a plurality of the aforementioned} one or more input variables. Any one of the optional features set out in connection with the eleventh aspect of the invention may be used in combination with the twelfth aspect of the invention. Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as _{set out in the accompanying claims. 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, where appropriate. For example, it will be appreciated that each of the first, second and third aspects of the invention may be combined with one another. Similarly, optional or preferred features of each of the first, second and third aspects of the _{invention may be applicable to one another. The fourth aspect of the invention may be} carried out using any of the first, second or third aspects of the invention. The method according to the fifth aspect of the invention may be carried out using the sixth or seventh aspects of the invention. The method according to the ninth aspect of the invention may be carried out using the eighth aspect of the invention. The method according to the tenth aspect of the invention may be carried out using the eleventh or twelfth aspects of the invention. Any one of the methods according to the fourth, fifth, ninth and tenth aspects of the invention may be combined with one another. Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a continuous inkjet (CIJ) printer, comprising a self-cleaning print head, according to an embodiment of the invention; 69726509-2 Figure 2 is a CIJ printer another embodiment, the printer comprising a wash station; Figure 3 is a schematic cross-section side view through part of the self-cleaning print head of the printer of Figure 1; Figure 4 is a schematic cross-section side view through part of the print head of the printer of Figure 2; Figure 5 is a flowchart showing steps of a method of cleaning the self-cleaning print head of Figure 3; Figure 6 is a flowchart showing steps of a method of cleaning the print head of Figure 4; Figure 7 is a schematic illustration of a CIJ printer according to another embodiment, the printer comprising a plurality of heating elements; Figure 8 is a schematic cross-section side view through a self-cleaning print head _{of the printer shown in Figure 7, the self-cleaning print head comprising a heating} element; Figure 9 is a schematic cross-section plan view of the self-cleaning print head of Figure 8; Figure 10 is a schematic cross-section plan view of a self-cleaning print head according to another embodiment, the self-cleaning print head comprising a plurality of infrared LEDs; Figure 11 shows a method of cleaning a print head according to an embodiment of the invention; Figures 12 to 15, 17, 18 and 20, 21 are flowcharts showing steps of a print head drying stage of the method of Figure 11; Figure 16 is a self-cleaning print head modified for carrying out the method shown in Figure 15; Figure 19 is a schematic illustration of a printer modified for carrying out the method shown in Figure 18; Figure 22 is schematic illustration of a printer according to another embodiment; Figure 23 is a flowchart showing steps of a method of using the printer of Figure 22 to test a dryness of the print head; Figure 24 is a graph showing voltage with respect to time, indicating an electrical response of a deflection electrode in connection with the method in Figure 23; Figure 25 is a flow chart showing steps of a method which covers a number of different ways in which the deflection electrode, of the printer of Figure 22, can be used; 69726509-2 Figure 26 is a schematic of a method according to another embodiment, showing input variables which may affect one or more parameters of the method; Figure 27 is a schematic illustration corresponding to the method shown in Figure 26, showing parameters of the method which can be modified responsive to the one or more input variables shown in Figure 26; F_{igure 28 is a schematic cross-section side view through an alternative print} head, suitable for use with the CIJ printer of Figure 7; F_{igure 29a is a plan view of the low voltage electrode assembly shown in Figure} 28; and F_{igure 29b is a view of the underside of the low voltage electrode assembly of} Figure 29a. Figure 1 schematically illustrates a continuous inkjet (CIJ) printer 1 according to an embodiment of the invention. The printer 1 comprises a printer body 2 (which may be referred to as a cabinet) connected to a print head 3 by an umbilical cable 4. The printer body 2 houses an ink system 5 and a printer controller 6. The printer body 2 also has an interface 7 (e.g. a display, keypad, and/or touch screen) for use by an operator. Although the controller 6 is disposed in the printer body 2 in the illustrated embodiment, in other embodiments the controller 6 may be disposed in the print head 3. In either case, the controller 6 is provided in electrical communication with the print head 3, and preferably also the printer body 2. The print head 3 is arranged to print on a substrate provided adjacent to the print head 3. The printer 1 typically comprises two cartridge connections for engagement with respective fluid cartridges. In particular, the printer 1 comprises an ink cartridge connection for engagement with an ink cartridge 8 and a (separate) solvent cartridge connection for engagement with a solvent cartridge 10. The cartridge connections typically each comprise a fluid port arranged to connect to a fluid pathway within the printer 1 to allow fluid to flow between the cartridges 8, 10 and other parts of the inkjet printer 1, such as the ink system 5 and the print head 3 (via the umbilical 4). The solvent _{cartridge 10 comprises unused solvent.} In operation, ink from the ink cartridge 8 and solvent from the solvent cartridge 10 can be mixed within the ink system 5 to generate printing ink of a desired viscosity that is 69726509-2 suitable for use in printing. This ink is to the print head 3 and unused ink is returned from the print head 3 to the ink system 5 (via the umbilical 4). When unused ink is returned to the ink system 5 from the print head 3, air may be drawn in with ink from a gutter of the print head 3. The air may then become saturated with solvent in the gutter line. In operation, ink is delivered under pressure from the ink system 5 to the print head 3 and recycled back via flexible tubes (e.g. conduits) which are bundled together with other fluid tubes and electrical wires (not shown) into the umbilical cable 4. In order to maintain correct consistency of the ink, the ink system 5 may be operable to mix ink removed from _{the cartridge 8 with solvent removed from the cartridge 10 and to mix them together to} obtain an ink having the correct viscosity and/or density for a particular printing application. In accordance with the invention, the print head 3 can be cleaned. In the illustrated example, the print head 3 is a self-cleaning print head. Without operator intervention, the print head 3 can be sealed, and a cleaning fluid (e.g. fresh and/or used solvent, or a fresh and/or used blend of solvents) be flushed through at least part of the print head 3, in order to clean the print head 3. The cleaning fluid circulates through the printer 1 from the printer body 2 to the print head 3, and then returns to the printer body 2 after. Self- cleaning print heads are advantageous for a number of reasons including, but not limited to: repeatable cleaning cycles, in-situ cleaning, and not needing operator intervention. The ink system 5 is also operable to store cleaning fluid and supply cleaning fluid to the print head 3 (e.g. in isolation of ink). This is particularly advantageous for a self-cleaning print head 3, in which cleaning fluid is circulated through the printer 1 to clean the printer 1 (e.g. specifically a chamber, and associated components, within the print head 3). Alternatively, a continuous inkjet printer may comprise an ink system for storing ink and supplying ink to the print head, and a separate system (e.g. cleaning fluid system) for storing cleaning fluid and supplying cleaning fluid to the print head. In other embodiments, the print head may not be a self-cleaning print head, but be cleaned using a wash station. 69726509-2 Turning to Figure 2, a continuous inkjet printer 1a according to such an embodiment is schematically illustrated. The printer 1a shares many features in common with the printer 1 shown and described in connection with Figure 1, and corresponding _{components are denoted using the same numerals. The printer 1a comprises a wash} station 12. The wash station 12 is for cleaning print head 3a, and specifically for cleaning _{one or more components of the print head 3a. As shown in Figure 2, the print head 3a is} placed into the wash station 12 when it is desired to clean the print head 3a (e.g. in a cleaning configuration). The print head 3a may be described as being docked in the wash _{station 12 in this configuration.} _{With the print head 3a inserted into the wash station 12, the print head 3a can be cleaned} in a number of different ways. In one embodiment, and as shown in Figure 2, one or more fluid outlets 14, 16, 18, disposed around the wash station 12, can eject a cleaning _{fluid into and/or onto the print head 3a in order to clean the print head 3a and/or} _{constituent components thereof. In other embodiments, with the print head 3a placed} _{into a wash station, the print head 3a can be cleaned by virtue of ejecting cleaning fluid} _{through a nozzle of the print head 3a itself. The used cleaning fluid can then be captured} _{by the wash station (or, in some embodiments, by the print head). It will be appreciated} that either embodiment may further comprise various features and functionalities, for _{example the ability to drain used cleaning fluid and/or dry the print head after cleaning.} By way of a further example, it will be appreciated that the wash station need not be coupled to the printer body itself. Instead, the wash station could be an entirely separate component to the printer body. As envisaged in the embodiment of Figure 2, it may be an operator that manually places _{the print head 3a into the wash station 12. Alternatively, in further variants, the print head} may automatically (e.g. by way of a robot arm) be placed into a wash station. _{Turning to Figure 3, a schematic cross-section side view through part of the self-cleaning} _{print head 3, as shown in Figure 1, is provided. Figure 3 shows the print head 3} comprising a nozzle body 20, charge electrode 24, chamber 26, low voltage electrode _{28, deflection electrode 30, gutter 32 and sealing mechanism 34. An ink jet 36 (e.g. a} stream of ink droplets), not deflected by deflection electrode 30, is also schematically indicated in Figure 3. 69726509-2 Briefly stepping through each of the aforementioned components in turn: the nozzle body 20, as mentioned, defines the nozzle 22. The nozzle 22 is for generating and ejecting a _{stream of ink droplets for printing. The ink jet 36 is shown being expelled by the nozzle} 22, although these ink droplets would not be used for printing because they pass straight into the gutter 32. Downstream of the nozzle and nozzle body 20, 22, the charge electrode 24 is provided. As the stream of ink droplets 36 is directed past the charge electrode 24, they are selectively and separately given a pre-determined level of charge by the charge electrode 24. Downstream of the charge electrode 24, low voltage and deflection electrodes 28, 30 are _{provided. The low voltage electrode 28 may otherwise be described as a grounded, or} _{negative potential, electrode. The deflection electrode 30 may be described as a high} voltage electrode. The electrodes 28, 30 may collectively be described as a pair of electrodes. An electric field is selectively generated between the low voltage and deflection electrodes 28, 30 for guiding the stream of ink droplets 36 away from the gutter _{32 and towards an ink aperture for printing onto a substrate in use. The ink aperture is} _{labelled 38. The ink aperture 38 may be described as being selectively opened and} closed by the sealing mechanism 34. _{Downstream of the electrodes 28, 30, the gutter 32 is provided. The gutter 32 comprises} _{a gutter aperture through which droplets of ink not used for printing (e.g. of ink jet 36) are} received and subsequently recirculated back into the ink system. Also shown in Figure 3 is a sealing mechanism 34. The purpose of the sealing _{mechanism 34 is to selectively seal the chamber 26 within the print head 3. The chamber} 26 is thus a selectively sealable volume which can be at least partly filled with cleaning fluid, and subsequently drained, in order to clean one or more components disposed within the chamber 26. As indicated in Figure 3, components disposed within the _{chamber 26 include the gutter 32 and electrodes 28, 30. Although the chamber 26 is} schematically shown as not including the charge electrode 24, fluid within the chamber _{26 can also enter the charge electrode 24. The charge electrode 24 can thus also be} _{cleaned by filling the chamber 26 with cleaning fluid. In some interpretations a cavity} 69726509-2 defined by the charge electrode 24 may considered to form part of the chamber 26. The chamber 26 may be described as a cleaning chamber, or a cleaning volume. The chamber 26, in the case of a self-cleaning print head, is a sealable internal volume. The sealing mechanism 34 may otherwise be described as a closure. The sealing mechanism 34 may take one of a number of different forms. The sealing mechanism 34 _{may comprise: a rotatable sealing mechanism (e.g. a rotatable body that rotates about} _{an axis to selectively open/seal chamber 26), a slidable sealing mechanism which} selectively opens/seals the chamber 26, an inflatable balloon seal that selectively opens/seals the chamber 26, or slidable housing pieces which selectively change the volume of the chamber. _{Turning to Figure 4, a schematic cross-section side view through part of the print head} 3a, shown in Figure 2, is provided. As will be appreciated by comparing Figure 4 with Figure 3, many of the features are shared in common and will therefore not be described _{in detail. However, of note, for the print head 3a the sealing mechanism 34 of Figure 3} is omitted. As such, the chamber 26 in Figure 4 is not sealable by a sealing mechanism _{which forms part of the print head 3a itself. Save for this difference, all features are the} same as that shown in Figure 3. _{Also of note, the chamber 26 shown in the Figure 4 embodiment may not be a strictly} defined chamber (e.g. a volume). Instead, the chamber 26 may indicate a zone onto which cleaning fluid is sprayed, during a cleaning cycle, to clean constituent components of the print head 3a. In one example, the chamber 26 may represent a zone of the print head 3a which is exposed when an outer cover (e.g. sheath) of the print head 3a is _{removed. When docked in a wash station, the combination of the wash station} (specifically a housing thereof) and the print head 3a may be described as defining a volume (e.g. a chamber). _{Although not illustrated in Figures 3 or 4, one or more ports, preferably a plurality of ports,} _{may be disposed in fluid communication with the chamber 26. These ports may provide} _{one or more of: a supply of cleaning fluid for cleaning the chamber, a supply of air for} _{pressure balancing (e.g. during printing, to replenish fluid drawn out of the chamber by} the gutter), drainage of used cleaning fluid from the chamber, and a supply of air for _{drying the chamber. One or more of the gutter 32 and the nozzle 22 may also provide} 69726509-2 _{the aforementioned port functionalities, in preferred embodiments the gutter 32} and nozzle 22 are not used to provide the chamber with such filling, draining or drying _{functionalities (the chamber 26 instead comprising one or more ‘dedicated’ multifunction} fill/drain/dry ports). Turning to Figure 5, steps of a method 50 are shown illustrating a cleaning cycle for the _{self-cleaning print head 3. The method 50 comprises a fill stage 52, soak stage 54, drain} stage 56 and a dry stage 58. During the fill stage 52, the chamber 26 is at least partly filled with cleaning fluid. By virtue of the chamber 26 being partly filled with cleaning fluid, components within the _{chamber 26 which are reached by the liquid level of the cleaning fluid are contacted by} the cleaning fluid. In the soaking stage 54, the cleaning fluid is held in the chamber. As suggested by the _{name, the soaking stage 54 provides a dwell period, (e.g. a period of time) in which the} _{cleaning fluid acts to remove deposits/build-up from the components and the chamber} _{26 itself. The soaking stage 54 may comprise percolating air or otherwise disturbing} (e.g. agitating) the cleaning fluid in the chamber 26 to improve the clean. In the draining stage 56, the used cleaning fluid from within the chamber 26 is drained. _{The chamber 26 is thus emptied of used cleaning fluid (and any deposit/build-up} entrained within the used cleaning fluid). In the drying stage 58, the chamber 26, and any components provided in fluid communication with the chamber 26, are dried. Although there are a number of different ways in which the drying can take place, one such example is that a supply of air be provided through one or more ports in communication with the chamber 26. _{It will be appreciated that the method 50 may be modified in various different ways, and} may be repeated in multiple cycles to provide a deeper clean. For example, the method _{50 may run multiple times in succession for a deeper clean of the print head 3a. It will} also be appreciated that a sealing step, in which the sealing mechanism sealing the chamber, precedes the fill stage 52. 69726509-2 Turning to Figure 6, steps of a method shown illustrating a cleaning cycle for the _{print head 3a (e.g. a print head used with a washing station). The method 80 comprises} _{a docking stage 82, spray stage 84, soak stage 86 and a drying stage 88.} In the docking stage 82, the print head 3a is docked in the wash station 12. Print head 3a may otherwise be described as being inserted into the wash station 12. The motion _{of inserting, or docking, the print head 3a into the wash station 12 may also create a seal} around the print head 3a. Said seal may contain cleaning fluid, used in the cleaning cycle, within the washing station 12 (e.g. reducing the risk that cleaning fluid escape between the print head 3 and the wash station 12). In the spray stage 84, cleaning fluid is sprayed (e.g. ejected) onto and/or into the print head 3a, specifically a chamber thereof and any constituent components which are exposed. The cleaning fluid acts to remove deposits/build-up from the components and the chamber. In the soaking stage 86, the cleaning fluid is left ‘applied’ to the print head for a dwell period (e.g. a period of time). During this time the cleaning fluid acts to remove deposit build-up from the print head 3a. _{In the drying stage 88, the print head 3a, the chamber and any constituent components} _{are dried. The drying can take a variety of different forms.} Like the method 50, the method 80 may be modified in various different ways and may _{be repeated multiple times to provide a deeper clean. For example, the drying stage 86} may be omitted entirely. Similarly, the soaking stage 86 may be omitted. It will be appreciated that the docking stage 82 need not be repeated, where multiple cycles are _{run in succession, for a deeper clean of the print head 3a. That is to say, the print head} 3a may remain docked, in-situ, such that the method 80 only be partially repeated (e.g. the spray and dry stages 84, 86 may be repeated). Turning to Figure 7, a schematic illustration of a CIJ printer 100 according to another embodiment is provided. The printer 100 shares many features in common with the printer 1 shown in Figure 1, and like features are provided with like reference numerals. 69726509-2 Like Figure 1, the printer 100 comprises head which is a self-cleaning print head, labelled 103. The printer 100 incorporates modifications for facilitating drying the _{chamber of the print head 103 (e.g. see chamber 26 of print head 3 in Figure 3). These} modifications take the form of first and second heating elements 106, 108. Both heating elements 106 and 108 may be described as being for drying the chamber of the print _{head 103. For the first heating element 103, this preferably takes place by way of a} _{direct, local heating of the print head 103. For the second heating element 108, this} preferably takes place by way of an initial direct heating of a fluid flow (e.g. convective _{heating), for a fluid flowing from the printer body 2 to the print head 103. Thermal energy} _{from the heated fluid flow is then subsequently transferred to the print head 103 (e.g. by} convection) once the flow reached the print head 103. Of note, whilst first and second heating elements 106, 108 are shown, either heating element may be omitted (e.g. such that there is only one heating element) in other embodiments. Advantageously, the heating elements 106, 108 provide a heating, and so a drying, _{functionality for the print head 103. The print head 103, the constituent chamber, and} components within that chamber, which may be wetted during a cleaning cycle, can thus be dried swiftly during a cleaning cycle. This advantageously reduces the cycle time of a cleaning cycle, meaning the printer 100 can return to printing more swiftly. Whilst Figure 7 shows the printer 100 comprising the self-cleaning print head 103, it will be appreciated that the heating concepts described herein apply equally to a print head which is not self-cleaning (e.g. a printer comprising a wash station). Furthermore, the heating concepts could be implemented in a wash station in isolation. For all of the drying methods and concepts described herein, it is particularly desirable that at least walls between the deflection electrode 30 and low voltage electrode 28 can be dried. This is for at least the reason that these walls provide insulation between the deflection electrode 30 and low voltage electrode 28. These walls may be described as at least partly defining the chamber. With the walls between the deflection electrode 30 and low voltage electrode 28 dry, it may be possible for deflection electrode 30 and low voltage electrode 28 to remain wet and still operational. That said, it is preferable that all components in the chamber, and including the chamber, wetted during a cleaning cycle, e.g. including the deflection electrode 30 and low voltage electrode 28, are dried. 69726509-2 Turning to consider the various forms heating elements can take: firstly the first heating element 106 will be considered. _{As mentioned, the first heating element 106 is disposed in the print head 103 itself. The} _{first heating element 106 can be constituted by a component within the print head 103} which is not necessarily a dedicated heater. For example, any one or more of a: nozzle body, charge electrode, low voltage electrode, and deflection electrode can be used to provide such heating. This could take the form of providing a power supply to one or _{more of these components, so as to create an effective resistive heating effect. That is} _{to say, the component increases in temperature, due to a resistance of the component} to the passage of electrons. A heating effect then results, by way of a direct heating of the component itself, or that heat being transferred to another component (e.g. by way of conduction, convection or radiation). Alternatively, or in combination, a dedicated resistive heater could instead be used. This could, in one form, take the form of a resistor _{which increases in temperature when current flows across it. In one particular} embodiment, as will be described in detail in connection with Figures 28 to 29b, a heating element (in the form of a heating resistor) is provided in thermal communication with the low voltage electrode. Activation of the heating element heats the low voltage electrode, the low voltage electrode being exposed to, and optionally defining at least part of a wall of, the chamber 26. _{An ink heater (not illustrated) is one example of a first heating element 106. The ink} _{heater is otherwise used to control a temperature of the ink (e.g. to control a viscosity} _{thereof) at, or upstream of, the nozzle body, during printing. The ink heater can be used} to heat the ink, increasing the viscosity of the ink. In some embodiments the ink heater may be coupled to the nozzle body. This may be described as a nozzle heater, or a nozzle body heater. The nozzle body can thus be heated in different ways. Where the _{nozzle body is used as the heating element, the nozzle body can be provided with power} to increase the temperature of the nozzle body (and provide a heating effect). Where the ink heater is coupled to the nozzle body, the nozzle body may be heated by activation of the ink heater (e.g. heated by conduction). For either option, the nozzle body can then transfer heat to fluid passing through the nozzle body (and so nozzle), and/or heat other components in thermal communication with the nozzle body, to provide a drying functionality. The ink heater may be a resistive heater. 69726509-2 _{Turning to Figure 8, a schematic cross- side view through the print head 103 of} _{Figure 7 is provided. Features of the print head 103 which are common to the print head} 3 shown in Figure 3 are provided with the same numerals. Of note, the low voltage and _{deflection electrodes 28, 30 are shown in a dashed line in Figure 8 to improve the} legibility of the Figure. In Figure 8 the first heating element 106 is shown adjacent a wall of a housing (e.g. chamber housing) which defines the chamber 26. Put another way, the first heating element 106 is separated from the chamber 26 by a first wall 110 of a chamber housing _{112 (see also Figure 9, which shows a schematic cross-section plan view through the} print head 3). The first heating element 106 may be described as coupled to the first wall 110. Advantageously, providing the first heating element 106 adjacent the chamber 26 in this manner means that the heating effect from the first heating element 106 can be more readily transferred to the chamber 26 and the components disposed within (e.g. the _{deflection electrode 30). In other embodiments the first heating element may be} embedded within the first wall. _{With continued reference to Figure 9, a thickness 114 of the wall 110 between the heating} element 106 and volume defined by the chamber 26 is reduced locally. Put another way, a wall thickness 114 proximate the heating element 106 is less than surrounding walls (e.g. compared to wall thickness 116). The inventors have found that a reduced wall _{thickness 114 of around 2 mm is desirable, but similar effects can be obtained with a} wall thickness of less than around 5 mm. This reduced wall thickness advantageously _{improves the conductive heat transfer from the first heating element 106 to the chamber} _{26 and components within the chamber.} _{Also shown in Figure 9 is a further heating element 118 (which may be referred to as a} second heating element 118, at least in connection with the present Figures). The _{second heating element 118 is provided adjacent a second wall 120. The second wall} 120 is disposed opposite the first wall 110. The above description, provided in connection with the reduced thickness 114 of the first wall 110 proximate the first heating element 106, also applies equally to a reduced thickness of the second wall 120 proximate the second heating element 118. 69726509-2 _{It will also be appreciated that further heating elements may also be disposed in further} positions around the chamber 26. For example, a heating element may be provided adjacent each of four walls which define a main cuboidal volume of the chamber 26. Where first and walls 110, 120 define a first pair of opposing walls, a corresponding second pair of opposing walls, defined by third and fourth walls (not labelled), may each comprise a respective heating element. Although the reduced wall thickness has been found to improve the conductive heat transfer from the first and second heating elements 106, 118, it will be appreciated that the first and second heating elements 106, 118 would still provide a heating effect in the absence of a local narrowing, or thinning, of the surrounding walls. The reduced thickness walls are thus an optional feature, which may be omitted in some embodiments. _{For the print head 103 shown in Figures 8 and 9, and indeed any other print head} described in this document, a further modification which has been found to increase the speed of drying is to manufacture the chamber housing 112 from a thermally conductive plastic. Thermally conductive plastic refers to a plastic, otherwise an insulator of heat, doped with a conductive substance to improve the thermal conductivity. For example, the chamber housing 112 can be manufactured from a polymer doped with aluminium nitride. Aluminium nitride provides high thermal conductivity but also desirable electrical insulation properties. Manufacturing the chamber housing 112 from a thermally conductive plastic means that the desirable manufacturing properties and electrical insulating properties of plastic can be utilised, along with the desired thermal conductivity for improved drying. Increased thermal conductivity is desirable for reasons of improved heat transfer through and across the chamber housing 112 to the chamber 26 and components disposed therein. It will be appreciated that manufacturing the chamber housing from a thermally conductive plastic may be used in isolation of any other concepts described in this document, or alternatively may be used in combination with any of the heating concepts described herein to improve the thermal transfer. 69726509-2 Turning to Figure 28, a schematic side view through an alternative print _{head 150, suitable for use with the CIJ printer 100 of Figure 7, is provided. Features of} _{the print head 150 which are common to the print head 3 shown in Figure 3 are provided} with the same numerals. In Figure 28, the geometry of the chamber 26 is different to that shown in the preceding Figures. In particular, the chamber 26 is partly defined by the low voltage electrode 28. Put another way, the low voltage electrode 28 (specifically a first face 28a thereof) defines at least part of a wall of the chamber 26. The low voltage electrode 28 is thus directly exposed to the chamber 26. As described above, the low voltage electrode 28 may otherwise be described as a grounded, or negative potential, electrode. At least the first face 28a of the low voltage electrode 26 may comprise an earth plate. _{The low voltage electrode 28 forms part of a low voltage electrode assembly 29 (which} may otherwise be described as a phase detector assembly). The low voltage electrode assembly 29 further comprises a heating element 31. The heating element 31 is a resistive heater in the illustrated embodiment. The heating element 31 is coupled to the low voltage electrode 28 (specifically to a second face 28b thereof). The heating element _{is specifically thermally coupled to the low voltage electrode 28. A conductive thermal} pathway thus exists between the heating element 31 and the low voltage electrode 28. Of note, whilst the first face 28a of the low voltage electrode 28 is directly exposed to the chamber 26, the second face 28b of the low voltage electrode 28 is not. Put another way, the second face 28b of the low voltage electrode 28, and components mounted thereto (e.g. the heating element 31), is shielded from the chamber 26 and the contents that pass through the chamber 26 (e.g. cleaning fluid, ink etc.). In use, activation of the heating element 31 increases the temperature of the heating _{element 31. This, in turn, (directly) heats the low voltage electrode 28. Given the direct} exposure of the low voltage electrode 28 to the chamber 26 (by virtue of the low voltage electrode 28 defining at least part of the chamber 26), the chamber 26 is, in turn, heated. _{A drying effect is thus provided, and the chamber 26, and components therein, can be} _{dried. This drying occurs more quickly than if, for example, there was no heating. A} _{cleaning cycle can thus be carried out swiftly and reliably. The aforementioned drying is} particularly beneficial for ambient conditions where drying could otherwise take an excessively long time (e.g. on a printing line in a frozen food factory, where the ambient 69726509-2 temperatures are low). A further of the low voltage electrode 28 being exposed to the chamber 26 is that the low voltage electrode 28 has a comparatively larger surface area than the heating element 31. As such, a greater convective heating effect is realised by providing the low voltage electrode 28 in direct exposure to the chamber 26. For the avoidance of doubt, it is envisaged the heating element 31 be activated during the drying steps 56, 88 for the methods 50, 80 illustrated in Figures 5 and 6 respectively (e.g. as part of a cleaning cycle). The heating element 31 may be activated during an entirety of the aforementioned drying steps 56, 88. Alternatively, the heating element 31 may be activated during only a portion of the drying steps 56, 88. For example, the heating element 31 may be activated, deactivated, then reactivated a plurality of times (e.g. pulsed on and off). In a further example, the activation of the heating element 31 may be supplemented by a further drying action. For example, the activation of the heating element 31 may be combined with any one, or more, of the drying methods illustrated and described in connection with Figures 12 to 21. In a particularly desirable embodiment, a flow of air may be provided through the chamber 26 during at least a _{portion (preferably all, or substantially all) of the time the heating element 31 is activated.} This provides an increased convective heat transfer through the chamber 26, further increasing the speed of drying. Turning to Figure 29a, a plan view of the low voltage electrode assembly 29 is provided (e.g. showing the first face 28a of the low voltage electrode 28). Figure 29a shows the first face 28a of the low voltage electrode 28 defining most of the (exposed) surface area of the low voltage electrode assembly 29 in this (plan) view. Also visible in Figure 29a are first and second phase sensors 33, 35, which are coupled to the low voltage electrode 28 (specifically to the first face 28a thereof). The first and second phase sensors 33, 35 _{are used to detect the phase of charged ink droplets in operation. Hence, the low voltage} electrode assembly 29 may otherwise be described as a phase detector assembly. Like the low voltage electrode 28, the first and second phase sensors 33, 35 are also directly exposed to the chamber 26. Turning to Figure 29b, a view of the underside of the low voltage electrode assembly 29 is provided (e.g. showing the second face 28b of the low voltage electrode 28). The second face 28b of the low voltage electrode 28 may be defined by a PCB, to which 69726509-2 _{several other components are mounted. the low voltage electrode assembly} _{29 further comprises a controller 37, a thermal cut-out 39, and further components 41} _{(e.g. resistors etc.). The controller 37 and thermal cut-out 39 are mounted to the second} _{face 28b of the low voltage electrode 28. One or more further components 41 may also} be mounted to the second face 28b of the low voltage electrode 28. _{Beginning with the controller 37 (which may be referred to as a microcontroller), the} controller 37 is in operative communication with the heating element 31. In particular, the controller 37 provides closed loop control of the temperature of the heating element 31. A computer program stored in the controller 37 provides the control. When activation of the heating element 31 is desired, the controller 37 initiates a control sequence. In the illustrated embodiment, the control sequence is a proportional–integral–derivative (PID) _{control sequence, in which the heating element 31 is ramped to a target temperature.} The ramp may be variable, such that in, for example, cooler ambient conditions, the ramp gradient is steeper (e.g. so that the heating element 31 reaches a target temperature more swiftly). In more typical ambient conditions, the ramp gradient may be shallower (e.g. so that the heating element 31 reaches a target temperature more slowly). Described generally: the ramp may be variable and may be influenced by one or more input variables, such as the input variables 395, and more detailed input variables 397, _{shown in Figure 27 (described in further detail below). Similarly, the ramp (e.g. the ramp} response) is a further example of a parameter of the cleaning cycle (e.g. like those labelled 422 in Figure 27) which can be adjusted responsive to one or more input variables 395. The way in which the heating element 31 is controlled by the controller 37 _{may be described as a ramp response. The ramp response is specifically an example of} adjustment that can be made to a method for drying the print head (e.g. parameter 430 in Figure 27). The ramping described above may take the form of controlling a voltage applied to the heating element 31 (e.g. resistive heater). In other embodiments, the target temperature of the heating element 31 may be adjusted based upon one or more input variables. For example, the target temperature may be _{increased in cooler ambient conditions. The target temperature may be reduced in} warmer ambient conditions. Returning to Figure 29b, the thermal cut-out 39 provides an override functionality should the temperature of the heating element 31 increase beyond an upper limit. The thermal 69726509-2 _{cut-out 39 can thus disconnect the element 31 and prevent further any further} _{temperature increase. The upper limit of the heating element 31 temperature may be} indicative of a safe long-term operating temperature (e.g. an operating temperature falling within a safe operating range). Advantageously, the direct exposure of the low voltage electrode 28, and so low voltage electrode assembly 29, to the chamber 26 provides a swift and reliable heating of the chamber 26. Drying of the chamber 26 can thus be effected reliably. The low voltage electrode 28 is also an existing component of CIJ printers generally, so the _{aforementioned modifications that provide the drying do not unduly increase the} component count. Whilst the phase sensors 33, 35 are sensitive to electrical noise, produced by the heating element 31 in use, the phase sensors 33, 35 are not used contemporaneously with the heating element 31. Put another way, whilst the phase sensors 33, 35 are typically only _{used during printing operations (and not whilst cleaning), the heating element 31 is} _{typically only used during cleaning operations (and not during printing operations). The} low voltage electrode 28 thus serves three different purposes in: i) providing a low voltage electrode, facilitating directional control of charged ink droplets during printing; ii) providing a thermal bridge between the heating element 31 and the chamber 26; and iii) providing a mounting surface for the phase sensors 33, 35. The above-described heating embodiment thus provides an efficient, multi-purpose use of the low voltage electrode 28. Turning to Figure 10, a schematic illustration of a cross-section plan view of a print head _{143 according to another embodiment is provided. The print head 143 shares many} _{features in common with the print head shown in Figure 3, and the relevant description} _{will not be repeated here for brevity. Like the print head 103 described and illustrated in} _{connection with Figures 8 and 9, the print head 143 in Figure 10 also comprises a heating} element, specifically a plurality of heating elements, which take the form of infrared LEDs. _{In print head 143, a plurality of infrared LEDs 146, 148, 150, 152 are provided. The} _{infrared LEDs are separate components which, when activated, provide a heating effect.} The infrared LEDs are positioned around the chamber 26. First and second infrared _{LEDs 146, 148 are provided through a first wall 110 of the chamber housing 112. Third} 69726509-2 and fourth infrared LEDs 150, 152 are through the second wall 120 of chamber housing 112. Although the infrared LEDs are shown partly disposed within the chamber 26, it will be _{appreciated that in other embodiments the infrared LEDs may not extend into the} chamber 26. The infrared LEDs may instead be separated from the chamber 26 by one _{of the walls defining the chamber 26 (e.g. first or second walls 110, 120).} Returning briefly to Figure 7, it will be recalled that in the printer 100 there is also a second heating element 108 which is disposed in the printer body 2. As previously mentioned, this second heating element 108, which can be used in isolation or in combination with the first heating element 106, provides another way by which the _{chamber, and components within the chamber, within the print head 103, can be} _{(indirectly) heated to dry them.} Like the first heating element 106, the second heating element 108 can be a resistive heater. However, unlike the first heating element 106, the purpose of the heating element 108 is to provide a convective heating effect to a fluid which flows from the _{printer body to the print head 103 along the umbilical 4. That is to say, the second} heating element 108 is provided in thermal communication with a fluid conduit in the printer body 2. Examples of fluid which could be heated by the second heating element _{108 include cleaning fluid, such as solvent, and air. The heating element 108 may heat} fluid as it flows past the heating element 108. One type of heating element that can be used, as the first and/or second heating elements 106, 108, is a Peltier device. Peltier devices use a Peltier effect. Peltier devices are a form of thermoelectric cooling which, upon passing an electric current through the Peltier device, move heat from a cold side of the device to a warm side of the device. A Peltier device can thus be used as the second heating element 108 in the printer body 2. A further use of a Peltier device is that of a combined heating and dehumidifying effect. Given that the Peltier device has a warm side and a cold side, if a fluid to be used for _{drying, such as air, is first passed across the cool side of the device, the amount of} moisture which can be retained in the fluid is reduced. Moisture in the fluid thus 69726509-2 condenses, reducing the moisture of the fluid. Put another way, the fluid is _{dehumidified. The dehumidified fluid can then be directly passed to the print head 103} _{or instead then passed along the warm side of the Peltier device. Passing the} _{(dehumidified) fluid along the warm side of the Peltier device acts to increase the} _{temperature of the fluid, increasing the moisture capacity of the fluid, such that the fluid} can carry more moisture. When the dehumidified and heated fluid is then passed to the _{print head 103, the fluid desirably has a lower moisture content due to having been} _{dehumidified, and can therefore absorb more moisture from the print head 103. The fluid} can absorb further moisture still because the increased temperature means that the capacity of the fluid to absorb more moisture is increased beyond that of a lower _{temperature example. Using a Peltier device as described could be used to form a} _{closed loop drying circuit in which drying fluid is dehumidified on a cold side of the Peltier} device, and then warmed up on a warm side of the device, and then continuously circulated through the printer system. In some embodiments it may also be possible to use a Peltier device already present in the device, such as a Peltier device disposed between a mixer tank and a solvent tank in the ink system 5. For any examples of heating elements described above, particularly those where a _{resistive heater is used, a PTC (positive temperature coefficient) element may be used.} _{A PTC is an electrical component with a resistance that varies with temperature, and} which is effectively self-regulating. Put another way, it is not necessary to use a feedback _{loop because a PTC is a failsafe heater. That said, in other embodiments a feedback} loop could be incorporated so that the temperature of the print head, the chamber of the print head, or one or more components within the chamber, can be monitored and the _{heating element adjusted accordingly. This applies not only to PTC heaters, but to any} other variety of heater disclosed herein (e.g. a feedback loop may be desirably used in combination with any variety of heater). Alternatively, the temperature of the heating element itself could be monitored and incorporated in a feedback loop (e.g. to control the temperature of the heating element). Similarly, for any embodiments of heating elements, particularly resistive heating _{elements, described above, it has been found that it is desirable to maintain the heating} element at a constant temperature so that the heating element, and any surrounding 69726509-2 components, are warm when required. may be described as maintaining a constant temperature even during periods of non-use. The inventors have found that it is possible _{to maintain the print head in particular at a constant temperature using resistive heaters} _{with a power output of as low as 1 watt to maintain a temperature, and up to 3 watts to} heat to the required temperature. _{Similarly, for any of the embodiments described above, or embodiments below in} _{connection with heating fluid, it is desirable to thermally couple the heating element to a} _{heat exchanger, such as a spreader plate (e.g. a reverse heat sink). This has been} found to improve the convective heat transfer from the heating elements to surrounding fluid. This may be achieved by way of increasing the surface area available for heat transfer. Alternatively to the continuously maintained temperature, heating elements described herein may be selectively activated based on one or more external factors, which will be described in further detail below. For example, a heating element may only be activated in certain ambient conditions during a drying cycle. Turning now to Figure 11, a further concept directed to improving the drying of a print _{head will be described.} _{Figure 11 shows a shortened method 160 for cleaning a print head according to an} embodiment of the invention. The method 160 is a generalised version of the methods _{50, 80 shown in connection with Figures 5 and 6 to a self-cleaning print head and a non-} _{self-cleaning print head. The method 160 can thus be carried out in connection with or} _{on any of the printers, or print heads, previously described.} Returning to Figure 11, shortened method 160 comprises a first step of providing a _{cleaning fluid 162 followed by a second step of drying the print head 164. Providing the} cleaning fluid 162 may comprise at least partly filling the chamber 26 of a self-cleaning _{print head 3 or may comprise spraying cleaning fluid onto the print head 3a via one or} more fluid outlets 14, 16, 18 of a wash station 12 (see Figure 2). _{The drying of the print head 164 may comprise locally drying the print head (e.g. for the} _{self-cleaning print head 3) or may comprise directly drying the print head by a fluid flow} 69726509-2 _{from a printer body (e.g. for the print or also for the self-cleaning print head 3).} The embodiments shown and described in connection with Figures 7 to 10 could all be used in connection with the method 160, although the method 160 also covers _{embodiments that do not necessarily incorporate a heating element. The method 160} _{may thus be described as providing options for drying a print head not necessarily} requiring the use of a heating element. These may be broadly described as a manipulation of fluid properties other than temperature. _{Turning to Figure 12, a first specific example of the dry print head stage 164 of Figure 11} is provided. The method 170 comprises an initiation of drying stage 172, followed by activation of a gutter pump 174. With brief reference to Figure 3, activation of the gutter pump, with the sealing mechanism 34 in the sealed position, with chamber 26 being an enclosed volume, will act to draw fluid through the gutter 32, specifically a gutter aperture thereof. Activating the gutter pump in this manner is advantageous because a pressure _{within the volume of the cleaning chamber 26 will begin to reduce. This may be} described as reducing a pressure in and/or around the print head, although in this _{example it is specifically reducing a pressure in the print head 3. Reducing the pressure} _{within the print head 3, specifically the chamber 26 thereof, means cleaning fluid, such} _{as solvent, can be more readily evaporated in the chamber 26. Put another way, the} _{cleaning fluid is more likely to change state from a liquid to a gas, aiding in the drying of} the chamber 26 and associated components. This phase change may also extract heat from the surroundings, and so is aided by the availability of heat, such as by one of the heating options described earlier in this document. _{Returning to Figure 12, an optional further drying step 176 is indicated after the activation} of the gutter pump step 174. The further drying step 176 could be the activation of a heater or other option for facilitating drying. However, this stage may be omitted in some _{embodiments. Finally, the drying stage ends at stage 178.} _{Turning to Figure 13, a further method 180 with an example of the drying print head stage} 164 of Figure 11 is shown. In the Figure 13 method 180, after initiating the drying stage _{182, an open sealing mechanism stage 184 is carried out. With reference to Figure 3,} this involves opening the sealing mechanism 34 to expose the chamber 26 to atmosphere (e.g. through the ink aperture 38). Returning to Figure 13, the drying step 186 then follows the opening of the sealing mechanism stage 184. The drying step may 69726509-2 _{further include pumping or providing a of air to the print head 3 to dry the chamber} thereof, potentially further incorporating a heating method as previously described. Finally, the drying stage terminates at stage 188. The open sealing mechanism method 180 has been found to be particularly advantageous when the further drying step 186, _{which could also precede the open sealing mechanism stage 184, comprises providing} a supply of fluid using a pump. Opening the sealing mechanism reduces the pressure _{drop across, or through, the print head 3, and so can increase air flow and also reduce} _{wear on the pump.} _{Turning to Figure 14, a further method 180 exemplifying the drying print head stage 164} _{shown in Figure 11 is provided. After an initial initiation of drying stage 192, a first burst} of fluid is provided at stage 194. This burst of fluid is a fluid which is used to facilitate _{drying of the print head. The fluid is preferably a gas, such as air. The first burst of fluid} refers to a flow of fluid which is provided for a period of time. The period of time may be, for example, around 10 seconds, around 30 seconds, or around 60 seconds. The burst _{of fluid is preferably provided at a comparatively high velocity through the print head.} _{This may otherwise be described as purging fluid through the print head. High velocity} gas, resulting from a high pressure, has been found to be particularly effective for drying _{the print head. Purging fluid may otherwise be described as puffing fluid.} In a subsequent stage 196 a further burst of fluid is provided. This may be the same as for step 194, or may be different (e.g. a different time period and/or pressure and/or flow velocity). A combination of these burst steps may be described as ‘purging’ (or ‘puffing’) _{high velocity gas, which has been found to decrease drying time. At the subsequent} stage 198 one or more further bursts of fluid may be provided. It will be appreciated that between each of steps 194, 196 and 198 a pause may be incorporated. At the final stage 200 the drying stage is terminated. Turning to Figure 15, a further method 210 exemplifying the drying stage 164 in Figure _{11 is provided. The method 210, after an initiation of drying stage 212 is completed,} _{provides a subsequent step 214 in which a supply of fluid is provided to a targeted} _{component of the print head. Put another way, a fluid flow is provided to dry one or more} _{specific components within the print head, as opposed to just drying the chamber more} generally. This could be achieved by way of one or more valves which selectively provide a fluid flow via one or more ports of the chamber which are directed at said components. 69726509-2 It may be a single component which is in step 214, or a plurality of components may be targeted. Examples of components which may be targeted include (with _{reference to Figure 3) the deflection electrode 30 and/or low voltage electrode 28, among} others. Walls of the chamber, e.g. between the deflection electrode 30 and low voltage electrode 28, are also desirable components/features to target for drying. The charge electrode’s 24 path to ground is another desirable area to target for drying. Turning to stage 216, an optional step is provided in which a targeted supply of fluid is provided to further components. Like step 214, step 216 may be applied to one or more components. These are preferably different components to that in step 214. Components may be cleaned sequentially (e.g. dried one by one) or alternatively a plurality of components may be dried simultaneously. In a final stage 218 the drying stage is terminated. _{Turning to Figure 16, a self-cleaning print head 220 modified for carrying out the method} 210 described and illustrated in connection with Figure 15 is shown. Many of the features _{of the print head 220 shown in Figure 16 are common to that of the print head 3 as shown} in Figure 3, and like features are provided with like numerals. _{As schematically indicated in Figure 16, the print head 220 further comprises first and} _{second ports 220, 224. Both of these ports 222, 224 are provided in fluid communication} with the chamber 26. The chamber 26 may be described as comprising the first and _{second ports 222, 224. Each of the first and second ports 222, 224 is positioned to target} _{different components of the print head 220. Specifically, the first port 222 is positioned} _{for directing fluid at the low voltage electrode 28. The second port 224 is positioned for} directing fluid at the deflection electrode 30. The first port 222 is shown schematically in _{fluid communication with a first conduit 226. The second port 224 is shown in fluid} communication with a second conduit 228. Provided along each of the first and second conduits 226, 228 are respective first and second valves, 230, 232. The first and second valves, 230, 232 are selectively opened and closed to place the first and second conduits 226, 228, and so first and second ports 222, 224, in fluid communication with a third conduit 234. Third conduit 234 may be described as a supply line. The third conduit 234 may be provided in fluid communication with, for example, a fixed or variable speed air pump. 69726509-2 By selective activation of the first and valves 230, 232, a supply of fluid can be _{provided to targeted components within the print head 220. For example, if it is desired} _{to target the low voltage electrode 28, at least the first port 222 can be placed in fluid} communication with the third conduit 234 by opening the first valve 230. If it is desired _{to target the deflection electrode 30, at least the second port 224 is placed in fluid} _{communication with the third conduit 234 by opening the second valve 232.} _{Alternatively, both first and second ports 222, 224 can simultaneously provide a supply} of fluid by opening both first and second valves, 230, 232. Whilst two ports and two corresponding valves are shown illustrated in Figure 16, it will be appreciated that more, or fewer, valves and ports could be used in order to provide more, or fewer, targeting _{options with in the print head 220. It will also be appreciated that references to fluid, in} connection with drying, are preferably specific references to a gas (e.g. air). Turning to Figure 17, a further method 240, exemplifying the drying step 164 of the _{method 160 of Figure 11, is provided. In the method 240 again the method is initiated} with the drying stage initiation step 242. This is followed by a step 244 in which an unstable fluid flow is provided. Unstable fluid flow is intended to mean an irregular fluid _{flow (e.g. not a constant fluid flow, and not even a cyclical fluid flow [e.g. a repeating} ‘pattern’]). One example of implementing an unstable fluid flow would be incorporating _{a compliant membrane along a fluid flowpath between the printer body and the print} head. As fluid flows across the compliant membrane, the membrane moves and/or _{deforms (e.g. in a sail-like manner) which has a corresponding effect on the fluid flow in} _{the print head. The compliant membrane could take the form of a duckbill e.g. a silicon} duckbill. An unstable flow has been found to improve the drying of the chamber 26 of a _{print head and components within. An optional further drying step 246 then follows step} 244, although this may be omitted in some embodiments. The drying stage then terminates at step 248. _{Turning to Figure 18, a further method 250 exemplifying the drying step 164 as shown} in the method of Figure 11 is provided. Upon initiation of the drying stage 252, a subsequent step of providing a supply of drying fluid from a canister or a factory air supply 254 is initiated. In this method the canister refers to a consumable container which holds a volume of gas used for drying. Examples _{include carbon dioxide, nitrogen and dry air (e.g. air that has been dehumidified). These} 69726509-2 _{are all gases which are advantageous use in drying the print head. In a similar} _{manner to the ink and solvent cartridges, it is envisaged that the canister be periodically} replaced to replenish the drying fluid as it is used in day to day cleaning cycles. An alternative to the use of a canister is the use of a factory air supply. Typically printing lines are located in factories which have a readily available supply of compressed air. _{This compressed air could equally be used for the drying of the print head and constituent} components. The factory air supply is a supply which is generally present in factories for the reasons mentioned previously, and it can therefore readily be supplied to the print _{head at pressures and velocities to facilitate drying. Finally, the drying stage terminates} at step 256. _{Turning briefly to Figure 19, a schematic illustration of a printer 260 modified for} implementing the method 250 is shown. By comparing the printer 260 of Figure 19 with _{the printer 1 of Figure 1 it will be appreciated that many of the features are common to} the printer 1 and these will not be described again in detail. However, in addition the printer 260 comprises a canister 262 and a conduit 264 for connecting the printer 260 to a factory air supply. It is noted that the printer 260 shows both the canister 262 and the conduit 264 for connection to the factory air supply. It is envisaged that in practice only one of these options would be implemented, although it will equally be appreciated that both options could be used. Although not shown in Figure 19, it will be appreciated that each of the canister 262 and conduit 264 (and so factory air supply) would be provided _{in fluid communication with the print head 3, specifically a chamber thereof, via the} umbilical 4 and other fluid connections within the printer 260. Turning to Figure 20, a further method 270 is provided exemplifying the drying stage 164 shown in the method of Figure 11. After a drying stage is initiated at 272, the method of _{270 moves to provide a supply of dehumidified fluid 274. The supply of dehumidified} _{fluid refers to the provision of fluid which has a reduced moisture level after it has} undergone a dehumidification process. For example, and as previously described, a Peltier device could be used to reduce the temperature of a flow, to reduce the moisture content within the flow. This is one form of dehumidification. The flow could then (optionally) subsequently be heated to increase the capacity of the fluid to take on moisture. 69726509-2 _{With the dehumidified fluid then the print head and constituent components,} the dehumidified fluid is readily able to absorb moisture from within the chamber and constituent components to provide an improved drying effect. Following stage 274, 276 indicates an optional further drying step. For example, the dehumidified fluid could be _{pumped into the print head using a fixed or variable speed air pump. Alternatively, the} _{fluid could be drawn into the print head by another means, such as activation of the gutter} _{pump and/or being entrained by a running jet. Following the above, the drying stage} terminates at stage 278. Turning to Figure 21, a further method 280 exemplifying the drying step 164 shown in Figure 11 is provided. The method 280 shown in Figure 21 will be described with _{reference to the print head 3 shown in Figure 3. As previously described, in a first step} the drying stage is initiated at 282. In a second stage 284, the nozzle is activated to _{generate a first fluid stream. With reference to Figure 3, a nozzle is labelled 22, defined} by nozzle body 20. An example of a first fluid stream generated by the nozzle 22 is the _{ink jet 36 as shown in Figure 3. However, a stream of cleaning fluid, solvent or air could} otherwise be used. At step 286 the gutter is activated to receive the first fluid stream. With reference to Figure 3, this involves activating gutter 32, by way of activating a gutter pump connected _{to the gutter 32, such that the first stream is generated (e.g. ink jet 36 received by the} _{gutter 32). A first fluid stream thus actively passes through the chamber 26 from the} _{nozzle 22 to the gutter 32. In the subsequent step 288, a second fluid is drawn through} _{the print head. With reference to Figure 3, this second fluid refers to a fluid stream other} _{than the first fluid stream (e.g. other than the ink jet 36). An example of a second fluid} _{flow is a flow of air which is drawn through leakage paths within the print head 3 and} drawn into the chamber 26 by virtue of the first fluid stream. For example, when the ink _{jet 36 is running, the ink jet is generated and ejected by the nozzle 22 and into the gutter} _{32, the inkjet 36 has a tendency to entrain (e.g. draw other fluids through) the chamber} 26. This represents another mechanism by which a fluid flow can be generated in the chamber 26 so as to dry the chamber 26 and components there within. In a final stage 290, the drying stage ends. It will be appreciated that all of the methods described and illustrated in connection with Figures 1 to 21 may be used individually or in combination with one another. Pauses 69726509-2 may be provided between individual and additional steps may otherwise be _{provided between said steps. As previously described, multiple drying stages may be} used to provide a multi-stage drying cycle. Turning to Figure 22, a schematic illustration of a printer 300 according to another _{embodiment is provided. The printer 300 is a continuous inkjet printer comprising a} _{printer body 302 and a (self-cleaning) print head 304. Although not shown in Figure 22,} _{the printer 302 and print head 304 are coupled to one another by way of an umbilical.} Figure 22 will be used to describe a system and method by which the voltage achieved _{at a deflection electrode, and corresponding current leak/draw, can be used to determine} _{that the print head 304 is dry and/or implement an (electrostatic) drying process.} Although not labelled or described in detail, the printer 300 may share many features in common with the printer 1 shown and described in Figure 1. _{Continuing to describe the printer 300, in the printer body 203 a controller 306 is provided} _{in electrical communication with a voltmeter 308 and a (high) power supply 310. The} _{voltmeter 308 is connected in series around a first resistor 312. The first resistor 312 is} electrically connected, via a cable 314, to a second resistor 316. The second resistor _{316 is disposed in the print head 304 and is for the print head 304. The second resistor} _{316 is connected to a deflection electrode 318. Also labelled is a low voltage electrode} 320. As previously described, in operation an electrical field is selectively generated between _{the deflection electrode 318 and the low voltage electrode 320. In normal operation the} _{deflection electrode 318 is electrically isolated from the low voltage electrode 320. The} _{low voltage electrode 320 is grounded. Various other electrical components are omitted} in Figure 22. The system shown in Figure 22, as will be described below in connection with method _{330, can be used to determine whether a dryness of the print head 304 falls within an} _{acceptable range. This provides a useful test to determine that the print head 304 is dry} _{and that the print head 300 can once again be used for printing (e.g. following a cleaning} _{cycle). This is of particular relevance where the print head 304 is a self-cleaning print} _{head, as shown in Figure 22.} 69726509-2 An area which is of particular concerning drying is a region between the _{deflection electrode 318 and the low voltage electrode 320. Although not shown in} _{Figure 22, from similar figures (e.g. Figure 8) it will be recalled that walls of a chamber} _{housing extend between the deflection electrode and the low voltage electrode. If,} _{following a cleaning cycle, these walls are still wet (e.g. with cleaning fluid) the deflection} electrode 318 will short to ground through the low voltage electrode 320. Put another way, the liquid present within the chamber can create a conductive path which will short _{the deflection electrode 318 when a voltage is supplied. This presents not only a safety} risk but also means that an electric field cannot be generated between the two electrodes because the electrons will take the path of least resistance to ground. _{When a system is working properly, when a supply voltage of, for example, 8 kV is} _{provided to the deflection electrode 318 via the power supply 310, the voltage at the} deflection electrode 318 should correspond to the supply voltage (i.e.8 kV). That voltage _{should be maintained at the deflection electrode 318. Similarly, the voltmeter 308 should} _{read 0 because there should be no voltage drop across the resistor 312, and so no} _{current drawn. However, if the region between the deflection electrode 318 and low} _{voltage electrode 320 is wet, a significant voltage drop across resistor 312 will be} _{observed, and a corresponding current draw be detected using voltmeter 310 (i.e. the} voltage drop divided by the resistance of first resistor 312). This indicates the region is not dry (e.g. a short). Turning to Figure 23, a method 330, which can optionally follow the drying print head stage 164 of Figure 11 is indicated. At step 332 a drying test is initiated. It may otherwise be described as starting a dryness testing method. Initiating the drying test may comprise modifying a baseline deflection electrode trip response to avoid the system shutting down should wetness be determined. _{In subsequent step 334 the deflection electrode 318 is supplied with a known supply} voltage. As previously mentioned, this may be 8 kV in some examples. Alternatively, other voltages could be used. 69726509-2 _{In subsequent step 336 the electrical of the deflection electrode 318 is} _{monitored. This may comprise monitoring the voltage drop across the first resistor 312} _{(e.g. using voltmeter 308) and/or the current drawn (e.g. again using voltmeter 308, but} calculating the current from the known voltage drop and resistance value). With reference to Figure 22 this could take the form that the voltage at the voltmeter 308 is monitored by the controller 306. _{At step 338, which follows, it is determined whether the electrical response of the} deflection electrode 318 falls within an acceptable range. This may comprise determining _{whether the voltage drop and/or current draw are within an acceptable range. This} acceptable range may refer to a voltage drop which is monitored over a period of time, or a current draw over a period of time. If these criteria fall within an acceptable range, _{the method proceeds to step 340, ending the dryness test. This is generally taken to} _{indicate that the dryness of a region between the deflection electrode 318 and low} voltage electrode 320 is acceptable, and that the printer 300 is therefore ready for use. Put another way, it has not identified or determined that a path to ground from the _{deflection electrodes 318 readily exists.} Should the electrical response of the deflection electrode 318 (e.g. voltage drop and/or current draw) fall outside of an acceptable range, the method proceeds to step 342. This is indicated as an action step. This could result in the test being temporality paused, e.g. _{for a period of time such as 10 seconds, 30 seconds, 60 seconds or more, and then the} test re-running. Alternatively, or in combination, the action step 342 could result in a _{repeat drying cycle (e.g. one or more of the methods described in Figures 11 to 21 could} _{be initiated, potentially for a second time). Subsequently, the dryness test may be re-} initiated. Step 338 may be described more generically as determining whether a dryness of a _{region between the deflection electrode 318 and the low voltage electrode 320 falls within} an acceptable range. With brief reference to Figure 22, the controller 306 may be described as being _{configured to receive a signal from the deflection electrode 318. The controller 306 may} _{be described as processing the signal to determine whether the print head 304 is dry.} 69726509-2 _{Turning to Figure 24, a graph 350 is An X axis 352 shows a time, in seconds.} On the Y axis 354, a Voltage is shown. The plot 350 thus shows voltage with respect to _{time (e.g. the variation of voltage with time).} Three lines are plotted on a graph 350. A first line 356 corresponds to a supply voltage. _{At a known time, T1, as indicated by line 356, supply voltage V1 is supplied to the} _{deflection electrode. For a dry print head (e.g. where a region between the deflection} electrode and the ground electrode does not have significant cleaning fluid built-up _{thereon) a voltage response of the deflection electrode is indicated by second line 358.} _{Second line 358 shows that the deflection electrode does not reach the supply voltage} _{V1 in a stepwise manner, like the first line 356. Instead, there is a slight build-up of the} voltage with time. However, by time T2, a greater time than T1, the known supply voltage _{V1 is reached by the deflection electrode. This indicates that the dryness of the print} _{head, specifically a region between the deflection electrode and the low voltage} electrode, falls within an acceptable range. Put another way, the supply voltage can be _{maintained at the deflection electrode (e.g. without the deflection electrode shorting to} _{ground). This indicates that there is no undesirable grounding of the deflection electrode} _{(e.g. by any cleaning fluid lingering on the chamber surfaces) and also indicates that} _{there is no current drawn by the deflection electrode. If this response by the deflection} _{electrode is observed, the print head, and printer more generally, can be determined to} _{be dry and ready for operation. This may be described as a positive drying test.} _{If, on the other hand, the voltage response of the deflection electrode corresponds to a} _{third line 360, this indicates that the dryness of the region between the deflection} _{electrode and the low voltage electrode falls outside of an acceptable range. The third} line 360 shows that it is not until time T3, a greater time than T1 and T2, that a voltage _{response of the deflection electrode reaches the supply voltage V1. In contrast to the} _{second line 358, third line 360 does not reach the supply voltage V1 at the first peak.} _{Instead, the voltage response by the deflection electrode undulates over a period of time.} _{This voltage response is indicative of the deflection electrode initially failing to reach the} supply voltage V1, suggesting the deflection electrode voltage has shorted to a local ground, for example by way of lingering cleaning fluid. This may also be described as _{the deflection electrode failing to maintain the supply voltage. A current draw would also} be observed at the deflection electrode, owing to this voltage drop. 69726509-2 Whilst Figure 24 shows the voltage on the Y axis 354, it will be appreciated that the current response could alternatively be monitored. For a current response the _{expected current draw of the deflection electrode would be zero, and any non-zero} _{current draw readings indicate that there is local grounding of the deflection electrode,} _{and the system is not dry.} _{Also of note, whilst the reading(s) shown in Figure 24 may be described as forming part} _{of a dryness testing method, by providing a voltage to the deflection electrode, even} _{when the deflection electrode is not dry, any cleaning fluid at the deflection electrode,} _{and in the region between the deflection electrode and the ground electrode, is} _{electrostatically atomised/dispersed/aerosoled upon supply of voltage to the deflection} electrode. Put another way, any lingering cleaning fluid will form field lines to local _{grounds when the voltage is provided. As such, the dryness testing method and} _{corresponding response can, itself, constitute a method of drying a print head owing to} this radiating of cleaning fluid. Turning to Figure 25, a flow chart for a method 370 is provided. The method 370 is a _{broad method which covers a number of different ways in which the deflection electrode} can be used. Method 330 shown and described in connection with Figure 23 is one specific example of the method 370. Returning to the Figure 25, in a first step 372 a drying control code mode is initiated. The drying control mode refers to a different mode of operation of the _{deflection electrode, specifically a trip functionality thereof in normal operations. Trip is} another way of describing an unexpected ‘grounding’, or ‘shorting’, of the deflection electrode. _{Typically, when a trip event is detected, indicative of a fault, the printer is shut down. In} _{accordance with the invention, upon initiation of the drying control mode, the trip} _{functionality is shut down (e.g. the typical printer response to shut down the printer, upon} detection of a trip event, is prevented). The drying control mode instead utilises the _{response of the deflection electrode to inform the user (e.g. of a dryness of the deflection} _{electrode) or provide another functionality (e.g. to dry a region between the deflection} electrode and the low voltage electrode). 69726509-2 _{In a subsequent step 374, the deflection is provided with a supply voltage. This} is preferably from the high voltage power supply. In some embodiments the supply _{voltage corresponds to a known supply voltage used for the deflection electrode in} _{operation, such as 8 kV. It will be appreciated that other, e.g. lower, supply voltages} could otherwise be used, however. _{The supply deflection electrode with supply voltage step 374 in Figure 25 may} correspond to the step 334 in Figure 23. The method 370 can be used as a method of drying the print head, whereby the supply _{of the deflection electrode with a voltage radiates, or spreads, cleaning fluid so as to dry} the print head. Alternatively, or in combination, the method 370 can form part of a _{dryness test in which the electrical response of the deflection electrode to the supply} voltage is monitored with respect to time to determine if the dryness falls within an acceptable range. This was as described in connection with Figures 23 to 24. Turning to Figure 26, a schematic illustration of a method according to another embodiment is provided. On the right hand side of Figure 26 a method of cleaning a _{print head is shown schematically and labelled 390. The method 390 comprises two} _{steps: providing cleaning fluid 392, followed by drying a print head 394. The steps 392,} 394 correspond to the two steps shown in method 160 in Figure 11. A distinction of the _{method 390 is that, in this embodiment, one or more parameters of the method are} determined in response to one or more input variables. Of note, Figure 26 only shows _{part of the overall method 390, with the variations of the method (i.e. the parameters of} _{the method determined responsive to the input variables shown in Figure 26) shown in} Figure 27. The method shown in Figures 26 and 27 may be carried out by a printer comprising a self-cleaning print head (e.g. printer 1 of Figure 1), or by a printer comprising a wash station (e.g. printer 1a of Figure 2), or by a wash station in isolation. Returning to Figure 26, the method 390, specifically one or more parameters thereof, is _{determined in response to one or more of: an orientation of the print head 396, an} ambient condition 398, a type of ink and/or cleaning fluid 400, a dimension of a fluid flow _{path 402, and a cleaning and/or shutdown history of the print head and/or printer 404. It} will be appreciated that any one, or more, of these input variables may be used to determine one or more parameters of the method 390. These input variables may be 69726509-2 _{referred to generally by numeral 395. any one or more of these input} _{variables may be omitted from the selected criteria (e.g. the ‘orientation of print head’} 396 may be omitted in some embodiments). _{Turning to consider some of the input variables 395 in further detail (e.g. indicated 397} in Figure 27), beginning with the ambient condition 398, the ambient condition 398 may _{comprise one or more of: temperature 406, humidity 408, ink temperature 410, and} cleaning fluid temperature 412. The temperature 406 refers to a general temperature of the printer and/or print head. The temperature 406 may be described as an ambient _{temperature (e.g. a temperature of the surroundings, such as the printing line on which} the printer is disposed). The temperature 406 may be determined at the printer body or _{at the print head. Similarly, humidity 408 refers to an ambient humidity in the environment} _{in which the printer and print head are located. As expected, ink temperature 410 and} cleaning fluid temperature 412 refer to the temperatures of the ink and cleaning fluid in the printer. Temperatures may be determined by temperature sensors, such as _{thermocouples, or by other temperature sensors.} Turning now to describe the dimension of fluid flow path 402 in more detail, two examples of dimensions of a fluid flow path which can affect the cleaning method include: fluid conduit length 414 and nozzle diameter 416. The fluid conduit length 414 refers to a length of a fluid conduit extending between the printer body and the print head. For example, with reference to Figure 1, a fluid conduit length would be at least as long as the umbilical 4. Returning to Figure 26, for a longer length of fluid conduit, there is a greater risk that ink and other deposits dry within a fluid conduit, which can necessitate a deeper cleaning cycle. Regarding nozzle diameter 416, this dimension refers to a diameter of the opening defined by the nozzle. A smaller diameter of nozzle is more liable to block, which may therefore necessitate a deeper cleaning cycle. _{Turning finally to the cleaning and/or shutdown history of print head and/or printer 404,} _{this variable can be broken down into: analysis of previous cleaning cycles 418 and,} separately, analysis of previous shut down cycle 420. Beginning first with the general cleaning and/or cleaning history step 404, the inventors have identified that consideration of this data in determining parameters of the method is of interest because the regularity of cleaning of the printer and/or print head, and the 69726509-2 previous shut down cycle of the printer, be indicative of the current cleaning status of the printer and/or print head. Put another way, in taking the previous cleaning cycles 418 as a specific example, if it can be observed that the printer has a healthy history of _{cleaning cycles (e.g. regular servicing) this may mean that only a comparatively lighter} cleaning cycle is needed. In contrast, if the previous cleaning cycles have not been carried out or have not been carried out to an acceptable level, this may necessitate a deeper cleaning cycle. Regarding the shut down cycle 420, there is similar logic to that _{described in connection with step 418: if it is observed that the previous shutdown cycle} _{occurred successfully, possibly incorporating a cleaning cycle, this may mean that only} a light cleaning cycle is needed. Alternatively, if the previous shut down cycle did not _{occur successfully (e.g. fell outside of an acceptable range) this may necessitate a} deeper clean of the printer/print head. One or more of the input variables 395, 397 may be determined in a number of different ways. For conditions such as temperature and humidity, these input variables may be determined by a sensor (e.g. a thermocouple) in electrical communication with a _{controller. Similarly, the orientation of the print head 396 may also be determined by a} sensor in electrical communication with the controller. Alternatively, the orientation of _{the print head may be manually input by an operator at an interface panel of the printer} body (e.g. the interface panel being in electrical communication with the controller). The type of ink and/or cleaning fluid 400 may be read from data stored on a chip of an ink and/or solvent cartridge. Alternatively, the type of ink and/or cleaning fluid may be inputted by an operator through an interface panel at the printer body. The dimension of a fluid flow path variables 402 are preferably input via an interface panel of the printer body, but could equally be read from data stored on a chip (e.g. the chip being provided on a component associated with the printer). The cleaning and shut down histories (e.g. _{404) are preferably read from a memory of the printer. Data indicative of the historic} _{cleaning cycles, and shutdown cycles, is preferably written to a memory of the printer} during shutdown and/or cleaning. This data can therefore be recalled, or read, by the _{controller as required at a later date. One or more of the input parameters may thus be} _{determined automatically, or may be manually input (e.g. by an operator).} Turning to Figure 27, a further schematic illustration is provided corresponding to the method 390 shown in Figure 26. Whereas Figure 26 shows the input variables which 69726509-2 one or more parameters of the method determined in response to, Figure 27 shows the one or more parameters of the method which can be modified in response to those input variables. The parameters are generally labelled 422. Stepping through each of these parameters in turn: A first parameter of the method which can be modified is the amount of cleaning fluid supplied 424. Where it is determined that a deep cleaning cycle is required, for example, it may be desirable to provide a greater amount of cleaning fluid. This might be by way _{of filing the chamber of a self-cleaning print head to a greater extent, or entirely, or may} comprise providing more cleaning fluid through the rinse stage of a wash station cleaning cycle. It will be appreciated that, generally speaking, providing a greater amount of cleaning fluid corresponds to a deeper clean. The greater amount of cleaning fluid may correspond to a greater liquid volume. A further parameter which can be modified is the time period of cleaning fluid supply 426. In some ways the time period of cleaning fluid supply 426 is similar to the amount of _{cleaning fluid supplied 424 in that, where a deeper clean is desired, a cleaning fluid} supply is provided for a longer period of time. Save for the variable used to monitor the cleaning fluid supply being the time period, rather than the amount of cleaning fluid, the description provided above in connection with 424 generally applies here. _{A time period for drying the print head 428 is a further parameter which can be modified.} Whereas steps 424 and 426 are primarily directed to providing a deeper clean (e.g. _{where ink deposits and build-ups are more difficult to remove), corresponding to a filling} _{or rinsing stage, the time period for drying the print head 428 corresponds to the drying} stage. Particularly where certain ambient conditions occur, such as low temperatures, it _{may be comparatively challenging to dry the print head using a baseline cycle. A greater} _{time period for drying the print head may therefore be utilised in a deeper cleaning cycle.} Similarly, where ambient conditions are comparatively warm, for example, less time may _{be needed to dry the print head. Being able to vary the time period used to dry the print} _{head is therefore a useful parameter in being able to improve a cleaning cycle which} _{provides a dry, yet clean, print head.} _{Somewhat similar to the above, another parameter which can be modified is the method} for drying 430. As described in earlier Figures, for example in the method shown in 69726509-2 _{Figures 12 through 21, there are ways by which the print head can be} dried, or by which a drying intensity can be varied. It may therefore be desirable to be _{able to activate one of these particular methods to change how the print head is dried.} _{A further way in which the drying method can be changed (e.g. another parameter of the} _{method) could be changing a drying intensity. A drying intensity may be determined by,} for example, the power supplied to a heating element, such as a resistive heater or _{infrared LED, which is used to provide a heating effect. Where it is determined that a} greater drying effect is required, it may be desirable to increase the drying intensity. As described in connection with Figures 28 to 29b, a ramp response of a heating element 31, activated to dry the print head (e.g. the chamber 26 thereof), is a further example of a method for drying the print head that can be adjusted. Adjusting the ramp response is another example of adjusting a drying intensity. _{A further parameter modification which can be used is to change the number of repeat} _{cycles of providing cleaning fluid 392 or drying the print head 394 (either or both being} captured by parameter 432). The method 390 could thus be partially repeated to provide an improved cleaning and/or drying effect. This may be used in combination with, or in _{isolation of, the aforementioned parameter modifications to the cleaning and drying} stages 424, 426, 428, 430. A further parameter which can be varied is the number of cycles of the cleaning method 390 itself, as indicated by 434. Put another way, the entire method 390 may be rerun a _{plurality of times, based upon one or more input variables and a consequently} determined method. Finally, and shown with a dashed line to indicate an optional parameter, a time period of the soaking stage 436 may be varied. It is noted that the method 390 does not include a soaking stage as shown in Figure 27. However, it will be recalled that the method 390 _{is a generalised version of the methods 50, 80 shown in Figures 5 and 6 (relating to a} self-cleaning print head, and a wash station, cleaning cycle respectively). Both of these _{methods show a soaking step where, after cleaning fluid is applied (e.g. by way of a filling} _{step 52 or a spraying step 84, there is a dwell period (e.g. a time period of soaking). This} time period of soaking (e.g. between application of cleaning fluid and drying) can be varied. For example, where a comparatively deeper clean is needed, the time period of the soaking stage can be increased. Conversely, where a deeper clean is not required, 69726509-2 _{and a lighter clean will suffice, the time of the soaking stage may be reduced (or} the soaking stage be eliminated altogether). Any one or more of these method parameters may be omitted from the list of method parameters determined in response to the one or more input variables (e.g. the amount of cleaning fluid supplied 424 may be omitted in some embodiments). _{Returning to Figure 27, a further parameter associated with the soaking stage that can} be varied is the agitation of cleaning fluid during the soaking stage as shown in 438. The agitation may take the form of a mechanical agitation (e.g. vibration) or may be achieved by percolating gas (such as air) through an at least partly filled chamber (e.g. for a self- _{cleaning print head). The agitation improves the intensity of the clean and increases the} likelihood of dislodging ink and other debris from the chamber and surrounding surfaces. _{The parameters 422 can be controlled, or implemented, in a number of different ways.} _{For the amount of cleaning fluid 424, time period of cleaning fluid supply 426 and method} _{for drying a print head 430, the controller can start a countdown clock which times these} _{processes and terminates them after a certain time period has elapsed (e.g. passed).} Selective actuation of valves and/or pumps can be used to implement these parameter adjustments (e.g. where the time period of cleaning fluid supply is to be increased, a corresponding cleaning fluid supply valve may be opened for a greater period of time). The amount of cleaning fluid 424 may be monitored based upon a liquid level at a point _{within the fluid circuit. The method for drying the print head 430 can be activated} dependent upon the method in question. For example, this may comprise activating a gutter pump, opening a sealing mechanism, providing bursts of fluid or providing a targeted supply of fluid to components (to name just some examples). The number of _{repeat cycles of either the entire method 434 or of the cleaning fluid and/or drying stages} _{432 may be repeated based upon operation of valves (e.g. as controlled by a controller).} The time period of the soaking stage 436 may be determined again by a clock or timer _{within the controller. Agitation of the cleaning fluid 438 may be controlled by the selective} activation of one or more actuators, such as a value or mechanical vibration source, to provide the agitation. _{The printer, specifically a controller thereof, may incorporate a ‘baseline’ (e.g. standard)} version of the method 390. This may be referred to as a baseline cleaning method, or a 69726509-2 _{standard cleaning cycle. The baseline method is preferably used where one or} _{more (or all, for example) input parameters 395, 397 fall within a baseline cleaning cycle} _{range. For example, where an ambient temperature falls within a baseline cleaning cycle} _{range of between 20-40°C (for example), a standard cleaning cycle is implemented.} Alternatively, where the temperature falls outside of that baseline cleaning cycle range (e.g. the temperature is comparatively hot or cold), the method, specifically a parameter _{thereof, may be adjusted accordingly.} _{An input variable falling outside of a baseline range may be described as a condition} _{falling within a light clean cycle range or a deep clean cycle range. An input variable} falling within the deep clean cycle range may necessitate that a deeper cleaning cycle _{occur. An input variable falling within the light clean cycle range may mean a light} cleaning method is used. For example, for a printer with a healthy history of previous cleaning cycles, only a light clean may be needed. _{It will be appreciated that one or more of the input variables 395 may be used either in} _{isolation or in combination with one another (e.g. to determine the one or more} parameters of the cleaning cycle). Similarly, one or more of the subcategories 397 may be used in combination with one another, or in combination with a different input variable 395. _{For method parameters 422, these parameters may be adjusted in isolation of one} another, or in combination with one another. For example, only one parameter 422 may be adjusted to implement a light, baseline or deep cleaning method. Alternatively, multiple parameters 422 may be adjusted to implement a light, baseline or deep cleaning method. Any one of the cleaning methods (e.g. light, baseline, deep) may comprise a nozzle backflush, as well as the chamber cleaning cycles described above. The method of cleaning 390 may occur at any point during operation of the printer. For example, it may occur during a shutdown process after printing has finished. Alternatively, the method 390 may occur on start-up, in which case again the input _{variable 395, 397 may affect one or more of the output parameters 422 used in the} method. 69726509-2 For any embodiment described herein, the print head may be a self-cleaning print head. _{The print head may comprise a cleaning chamber, optionally selectively sealable by a} sealing mechanism. The at least one electrode may be disposed in the chamber. Any one of the methods described herein may be implemented by a controller. The controller is preferably in electrical communication with the printer body and print head. The controller is preferably disposed in the printer body, but may otherwise be disposed in the print head. Unused solvent may otherwise be described as fresh, or virgin, solvent. 69726509-2

Claims

CLAIMS: _{1. A print head for a continuous inkjet printer, comprising:} a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; and a heating element for drying the print head. _{2. The print head according to claim 1, wherein the heating element comprises one} _{or more of: an ink heater; a nozzle body, which defines the nozzle; the charge electrode;} a low voltage electrode; and a deflection electrode. _{3. The print head according to claims 1 or 2, wherein the heating element comprises} a resistive heater. _{4. The print head according to claim 3, wherein the print head comprises a cleaning} chamber, the at least one electrode disposed in the cleaning chamber. _{5. The print head according to claim 4, wherein the print head further comprises a} low voltage electrode, and the cleaning chamber is at least partly defined by the low voltage electrode. _{6. The print head according to claim 5, wherein a first face of the low voltage} electrode is exposed to the cleaning chamber. _{7. The print head according to claims 5 or 6, wherein the resistive heater is thermally} coupled to the low voltage electrode. _{8. The print head according to claims 6 and 7, wherein the low voltage electrode} _{defines a conductive thermal pathway between the resistive heater and the cleaning} chamber. _{9. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a print head; 69726509-2 an umbilical coupling the print to the printer body, the umbilical comprising _{one or more fluid conduits and electrical wires;} the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; f_{urther comprising a heating element for drying the print head.} _{10. The continuous inkjet printer according to claim 9, wherein the heating element} is a resistive heater. _{11. The continuous inkjet printer according to claims 9 or 10, wherein one or more of} _{the printer body and the print head comprises the heating element.} _{12. A method of cleaning a print head of a continuous inkjet printer, comprising:} _{providing a supply of cleaning fluid to the print head; and} _{heating at least part of the print head to dry the print head.} _{13. The method of claim 12, wherein heating at least part of the print head comprises} activating a heating element. _{14. The method of claim 13, wherein activating the heating element comprises} activating a heating element disposed in the print head. _{15. The method of claim 14, wherein activating the heating element comprises} _{activating a resistive heater that heats a cleaning chamber of the print head.} _{16. The method of claim 15, wherein activating the resistive heater comprises heating} a low voltage electrode thermally coupled to the resistive heater. _{17. The method of claim 16, wherein the low voltage electrode defines at least part} of the cleaning chamber, and wherein heating the low voltage electrode heats the cleaning chamber to dry the cleaning chamber. 69726509-2

_{18. The method of any one of to 17, further comprising ramping, based} upon one or more input variables, the heating element to a target temperature, the one or more input variables optionally comprising one or more ambient conditions such as temperature and/or humidity. _{19. A method of cleaning a print head of a continuous inkjet printer, comprising:} _{providing a supply of cleaning fluid to the print head; and} drying the print head by one or more of the following: i_{. activating a gutter pump;} _{ii. opening a sealing mechanism of the print head and exposing a chamber of} the print head to atmosphere; i_{ii. providing a plurality of bursts of fluid flow to the print head;} _{iv. directing a supply of fluid to targeted components of the print head;} _{v. providing an unstable fluid flow;} _{vi. providing a supply of drying fluid from a canister or factory air supply;} _{vii. providing a supply of dehumidified fluid; and} _{viii. activating a nozzle, of the print head, and ejecting a fluid stream therefrom} to draw fluid through the print head. _{20. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising _{one or more fluid conduits and electrical wires;} a controller in electrical communication with the print head; the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; w_{herein the controller is configured to, upon initiation of a drying step of a} cleaning cycle, one or more of: i_{. activate a gutter pump, in the printer body, to draw fluid through the gutter} in the print head; 69726509-2 _{ii. open a sealing mechanism the print head to expose a chamber of the} print head to atmosphere; i_{ii. provide a plurality of bursts of fluid flow;} _{iv. direct a supply of fluid to targeted components of the print head;} _{v. provide an unstable fluid flow;} _{vi. provide a supply of drying fluid from a canister or factory air supply;} _{vii. provide a supply of dehumidified fluid; and} _{viii. activate the nozzle to generate and eject a fluid stream to draw fluid through} the print head. _{21. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising _{one or more fluid conduits and electrical wires; and} _{a controller in electrical communication with the print head;} the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the controller is configured to: i_{nitiate a drying control mode; and} supply the deflection electrode with a supply voltage. _{22. The printer according to claim 21, wherein the controller is configured to initiate} a drying step of a cleaning cycle. _{23. The printer according to claims 21 or 22, wherein the controller is configured to:} initiate a dryness test; supply the deflection electrode with a supply voltage; receive a signal from the deflection electrode; and process the signal to determine whether a dryness of a region between the deflection electrode and the low voltage electrode falls within an acceptable range. 69726509-2 _{24. The printer according to claim 23, wherein if the dryness of a region between the} _{deflection electrode and the low voltage electrode falls outside of the acceptable range,} the controller initiates a drying step of a cleaning cycle. _{25. A method of using a print head of a continuous inkjet printer, comprising:} initiating a drying control mode; and supplying a deflection electrode of the print head with a supply voltage. _{26. The method according to claim 25, wherein the method is a method of drying the} print head. _{27. The method according to claims 25 or 26, wherein the method is a dryness testing} method for determining whether a print head of a continuous inkjet printer is dry, the method further comprising: m_{onitoring an electrical response of the deflection electrode over time; and} determining whether a dryness of a region between the deflection electrode and _{the low voltage electrode falls within an acceptable range, based upon the electrical} response of the deflection electrode. _{28 The method according to claim 27, wherein if the dryness of the region between} the deflection electrode and the low voltage electrode falls outside of the acceptable _{range, a drying step of a cleaning cycle is initiated.} _{29. A method of cleaning a print head of a continuous inkjet printer, comprising:} providing a supply of cleaning fluid to the print head; and drying the print head; wherein one or more parameters of the method are determined responsive to one or more input variables: i_{. an orientation of the print head;} _{ii. an ambient condition;} _{iii. a type of ink and/or cleaning fluid;} _{iv. a dimension of a fluid flowpath of the printer; and} _{v. a cleaning and/or shutdown history of the print head and/or printer.} 69726509-2

_{30. The method according to claim wherein the method of cleaning occurs at} start-up. _{31. The method according to claims 29 or 30, wherein the one or more input variables} are automatically detected. _{32. The method according to claims 29 or 30, wherein the one or more input variables} are manually input. _{33. The method according to any one of claims 29 to 32, wherein a baseline cleaning} _{method is used for one or more input variables falling within a baseline range.} _{34. The method according to any one of claims 29 to 33, wherein a deep cleaning} method is used for one or more input variables falling within a deep clean range. _{35. The method according to any one of claims 29 to 34, wherein a light cleaning} method is used for one or more input variables falling within a light clean range. _{36. The method according to any one of claims 29 to 35, wherein the ambient} condition comprises one or more of: i_{. temperature;} _{ii. humidity;} _{iii. ink temperature; and} _{iv. cleaning fluid temperature.} _{37. The method according to any one of claims 29 to 36, wherein the dimension of a} fluid flowpath of the printer comprises one or more of: i_{. a length of a fluid conduit extending between a printer body and the print} _{head; and} _{ii. a diameter of a nozzle of the print head.} _{38. The method according to any one of claims 29 to 37, wherein determining one or} _{more parameters of the method responsive to a cleaning and/or shutdown history of the} print head and/or printer comprises: 69726509-2 _{i. analysing data entries to one or more previous cleaning} cycles, and determining whether the one or more previous cleaning cycles fall within an acceptable range; and/or i_{i. analysing data entries corresponding to the previous shutdown cycle, and} determining whether the previous shutdown cycle falls within an acceptable range. _{39. The method according to any one of claims 29 to 38, wherein the one or more} _{parameters of the method comprise one or more of:} _{i. an amount of cleaning fluid supplied to the print head;} _{ii. a time period during which cleaning fluid is supplied to the print head;} _{iii. a time period for drying the print head;} _{iv. a drying method for drying the print head;} _{v. a number of repeat cycles for the providing a supply of cleaning fluid to the} _{print head and/or drying the print head steps; and} _{vi. a number of repeat cycles of the method of cleaning the print head.} _{40. The method according to any one of claims 29 to 29, wherein the method further} comprises a soaking stage which precedes the drying of the print head, wherein the one or more parameters of the method comprise one or more of: i_{. a time period over which the soaking stage occurs; and} _{ii. agitating the cleaning fluid during the soaking stage.} _{41. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a print head; an umbilical coupling the print head to the printer body, the umbilical comprising _{one or more fluid conduits and electrical wires; and} a controller in electrical communication with the print head; the print head comprising: a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; 69726509-2 wherein the controller is to determine one or more parameters of a method of cleaning the print head responsive to one or more input variables: i_{. an orientation of the print head;} _{ii. an ambient condition;} _{iii. a type of ink and/or cleaning fluid;} _{iv. a dimension of a fluid flowpath of the printer; and} _{v. a cleaning and/or shutdown history of the print head and/or printer.} _{42. The continuous inkjet printer according to claim 41, wherein the one or more input} variables are: i_{. determined by a sensor in electrical communication with the controller; or} _{ii. read from data stored on a chip of an ink and/or solvent cartridge; or} _{iii. input via an interface panel of the printer body, the interface panel in electrical} communication with the controller; or i_{v. read from a memory of the printer.} _{43. The continuous inkjet printer according to claims 41 or 42, wherein the one or} more parameters comprise one or more of: i_{. an amount of cleaning fluid supplied to the print head;} _{ii. a time period during which cleaning fluid is supplied to the print head;} _{iii. a time period for drying the print head;} _{iv. a drying method for drying the print head;} _{v. a number of repeat cycles for the providing a supply of cleaning fluid to the} print head and/or drying the print head steps; and v_{i. a number of repeat cycles of the method of cleaning the print head.} 69726509-2