Industrial inkjet printer with current consumption measurement for ink contamination detection

Abstract

The present invention relates to a circuit for a CIJ printer, said circuit comprising: - a power supply (5) for providing at least one deflection voltage to a deflection electrode for deflecting ink drops; - an electrically conductive ink detection unit (5, 10) for detecting the presence of residual dry or liquid electrically conductive ink on or in contact with said deflection electrode, said unit comprising: * a current detector (14) for detecting the current provided by said power supply when applying said at least one deflection voltage; and * a calculator (10) programmed to calculate at least one first value derived from said current over a period of time and to detect the presence of residual dry or liquid electrically conductive ink on or in contact with at least one of said deflection electrodes based on said at least one derived value.

Description

Technical Field

[0001] This invention relates to the detection of ink contamination on or in contact with the deflection electrode of an industrial continuous inkjet printer. Background Technology

[0002] Industrial continuous inkjet printers are known in the fields of coding and industrial marking of various products, such as for marking barcodes or expiration dates directly on the production line and at high speed on food.

[0003] Continuous inkjet printers are divided into two categories: – On the one hand, multi-deflection continuous jet printers, in which each droplet of a single jet (or multiple jets) can be sent on various trajectories corresponding to different deflection commands for each droplet, thereby enabling scanning of the area to be printed along the direction of deflection; On the other hand, a binary continuous jet printer, in which multiple jets arranged side by side each have only one trajectory for printing; by synchronously controlling all jets at a given time, a pattern that roughly reproduces the nozzle distribution on the nozzle plate can be printed on the medium.

[0004] In both cases, the other direction used to scan the area to be printed is covered by the relative displacement of the print head and the medium to be printed.

[0005] These printers have several typical sub-components found in most commercially available industrial continuous inkjet printers. In practice, when these machines are used on production lines, they are typically equipped with small printheads, which allows them to be integrated into a smaller space.

[0006] Specifically, deflection or deviation from electrode 4 (in) Figure 1A (As shown above) This allows charged ink droplets to be deflected as they enter between these electrodes. The magnitude of the deflection depends on the charge and velocity of the droplets. The deflected droplets strike the medium to be printed, while undeflected droplets are collected by grooves so that they can return to the ink loop for recycling.

[0007] During printer operation, ink may deposit on deflection electrode 4 and may dry due to effects such as deflected jets or splattering. This is in Figure 1B As shown in, Figure 1B In this process, electrode 4 is stained by ink 7. This affects the ability of electrode 4 to properly deflect ink droplets and renders the printhead unusable until it is cleaned. Because the ink is typically dark, the electrode holder or active plate 23 (on which the electrode is typically mounted or attached) is typically dark gray, and there is almost no contrast between the ink and the ink-laden active plate, making the ink contamination virtually invisible and difficult for the operator to detect.

[0008] For the same reason, ink 7a can also be placed between the holding plate 23 of each electrode 4 and the electrode itself (e.g., Figure 1C (As shown) the ink is deposited and dried, in which case the operator cannot see the ink. This also affects the electrode's ability to properly deflect the ink droplets.

[0009] There are no methods or equipment to detect this contamination on the deflection electrode.

[0010] Furthermore, the ink is conductive, and inks formulated with black carbon pigments (for demanding applications where adhesion is critical) remain conductive even after drying. This conductive ink residue leads to leakage currents at high voltage potentials.

[0011] Therefore, it is necessary to easily detect this ink contamination in CIJ printers and stop the printer when it is detected.

[0012] It is also necessary to examine the temporal evolution of this ink contamination in CIJ printers in order to predict printer malfunctions. Summary of the Invention

[0013] This invention first relates to a circuit for one or more deflection electrodes in a single-jet or multi-jet continuous inkjet printer, the circuit comprising: - A power supply for providing at least one deflection voltage to the deflection electrodes of the printer for deflecting ink droplets; - A conductive ink detection unit for detecting the presence of residual dried or liquid conductive ink on or in contact with at least one of the deflection electrodes, the unit comprising: * A current detector that detects the current supplied by the power source when the at least one deflection voltage is applied; and * A calculator or computing device programmed to calculate at least one first value derived from the current during a first time period, and to detect the presence of residual dried or liquid conductive ink on or in contact with at least one of the deflection electrodes based on the at least one derived value.

[0014] The CIJ printer may include a printhead comprising an ink droplet generator for forming ink droplets, at least one electrode for charging the ink droplets, and the one or more deflection electrodes for deflecting the ink droplets. It may also include a controller, with all or part of the circuitry according to the invention forming part of the controller or part of the printhead.

[0015] In the circuit according to the invention, the at least one derived value may include the current or a statistical value of the time derivative of the current.

[0016] The calculator can be programmed to compare the first derived value with at least one first threshold.

[0017] In a particular embodiment, the at least one derived value includes the current and a statistical value of the time derivative of the current, and the calculator is programmed to compare the time derivative with at least one second threshold to detect the presence of residual dried or liquid conductive ink on or in contact with the deflection electrode.

[0018] In the circuit according to the invention, the calculator can be programmed to calculate at least one second derived value of the current during a second time period different from the first time period (e.g., the second time period is longer than the first time period), and to detect the temporal evolution of the presence of residual dried or liquid conductive ink on or in contact with the deflection electrode based on the at least one second derived value. The calculator can be programmed to compare the second derived value with at least one third threshold.

[0019] In the circuit according to the invention, the calculator can be programmed to detect current and compare the current with a threshold, and when the current is higher than the threshold, for example for safety reasons, to interrupt the power supply to the off-electrode.

[0020] In the circuit or method according to the present invention, the first derived value and / or the corresponding second derived value may include at least: - The maximum value of the current during the first time period and / or correspondingly the second time period, and / or - The minimum value of the current during the first time period and / or correspondingly the second time period, and / or - The difference between the maximum and minimum values ​​during the first time period and / or the corresponding second time period, and / or - The change in current during the first time period and / or correspondingly the second time period, and / or - The average value of the current during the first time period and / or the corresponding second time period.

[0021] In the circuit according to the invention, the conductive ink detection unit can be programmed to trigger a signal when the presence of residual dried or liquid conductive ink is detected on or in contact with at least one of the deflection electrodes.

[0022] The signal can trigger the cleaning of at least one of the deflection electrodes.

[0023] The calculator can also be programmed to calculate a third derived value of the current supplied by the power source after cleaning at least one of the deflection electrodes, in order to detect the presence of residual dried or liquid conductive ink on or in contact with at least one of the deflection electrodes based on the at least one third derived value within a third time period.

[0024] The third derived value may include the current or a statistical value of the time derivative of the current (as defined above).

[0025] The calculator can be programmed to compare the third derived value with at least one fourth threshold.

[0026] The circuit according to the present invention may further include: - At least one memory for storing data of the current supplied by the power supply, the current supplied by the power supply for deflecting ink droplets, varying with temperature in the printhead, and a means for measuring the temperature; - Possibly, a means for comparing the measured current supplied to the electrode with a stored value of the current at the temperature.

[0027] In the circuit according to the invention, the power supply is capable of providing a voltage between 1kV and 10kV or between -1kV and -10kV.

[0028] The present invention also relates to a method for controlling a single-jet or multi-jet continuous inkjet printer or for controlling the deflection electrodes of the printer, the method comprising: - Apply at least one deflection voltage to the deflection electrode; and - The presence of residual dried or liquid conductive ink on the deflection electrode is detected by the following method: *Measure the current supplied to the deflection electrode when the at least one deflection voltage is applied; * Calculate a first value derived from the current during the first time period (e.g., a statistical value of the current or the time derivative of the current). - The presence of residual dried or liquid conductive ink on the deflection electrode is detected based on the first derived value.

[0029] In the device or method according to the invention, the CIJ printer may include a printhead comprising an ink droplet generator for forming ink droplets, at least one electrode for charging the ink droplets, and one or more deflection electrodes for deflecting the ink droplets.

[0030] In the apparatus or method according to the invention, the ink is formulated, for example, with black carbon pigment. Attached Figure Description

[0031] Figures 1A to 1C This is an example of a deflection electrode and ink contamination deposited on it.

[0032] Figure 2 The method according to the present invention is shown.

[0033] Figure 3 This is an illustrative example of a system according to the present invention.

[0034] Figure 4A and Figure 4B This is an example of the current detected according to the present invention.

[0035] Figure 5A and Figure 5B These are examples of circuits that can be implemented within the framework of this invention.

[0036] Figure 6 This is an example of a CIJ printer to which this invention can be applied. Detailed Implementation

[0037] Figure 2 This is a schematic diagram of the deflection electrode 4 of the CIJ printer. The power supply 5 provides a high voltage V to the electrode 4, for example, between +1kV and +10kV.

[0038] When the deflection voltage is applied, a current I is also supplied to electrode 4 through the power supply. If electrode 4 is clean, the current I is equal to the current I1 flowing in the electrode. Due to contamination, such as one or more droplets 7 of dried conductive ink and / or liquid conductive ink deposited on electrode 4, the current I is altered: an additional current I2 flows in parallel with the current I1 in electrode 4 within the conductive ink 7. It then flows further to the ground or into the cap of the printhead.

[0039] The current I can be measured, for example, continuously or periodically, and any change in the measured value of the current indicates the presence of one or more drops of ink and / or dry ink on or against the electrode.

[0040] This also applies to any value calculated from the current I, i.e., so-called derived values, such as the average value of the current I and / or the time derivative of the current dI / dt and / or any other statistical value, such as: - The maximum and / or minimum values ​​of the current during a given time period, and / or - The difference between the maximum and minimum values ​​during the stated time period, and / or - The average value of the current during the time period.

[0041] One or more of these values ​​can be compared to one or more thresholds. For example, the average current over a time period can be compared to a first threshold, and the time derivative of the average can be compared to a second threshold that is different from the first threshold.

[0042] Different situations can be detected based on the time period, for example: - Detection within the first time period can indicate the presence of contamination on the electrode; - Detection during a second time period longer than the first time period can indicate the formation of contamination on the electrode.

[0043] Therefore, one or more of the above values ​​can be: -Measured or calculated at different time periods, such as a first (shortest) time period T1 (e.g., 5 minutes) and a second time period T2 (longer than T1, e.g., T2 = 24 hours). - Compare with appropriate different thresholds, such as a first threshold and a second threshold (different from the first threshold).

[0044] If one or more of the values ​​exceed one or more of the thresholds, a signal can be triggered indicating that the electrode needs to be cleaned: for example, the printer can be stopped and / or a warning can be displayed on the display device to notify the operator that cleaning is required, or the signal can trigger an automatic cleaning step.

[0045] Following the cleaning step of electrode 4, a step may be taken to measure or calculate one or more of the aforementioned values ​​and compare them with corresponding thresholds to determine whether cleaning was performed appropriately and whether no contamination remained on the electrode. This threshold may differ from the threshold before cleaning because there may be some hysteresis effect. Based on the comparison results, one or more additional cleaning steps may be performed.

[0046] Figure 3 A system according to the present invention is shown, for example, to implement the above-described method. The system includes: - Power supply device 5 (or voltage supply device) for supplying appropriate voltage to electrode 4. - Electronic device 10, such as a microprocessor or microcontroller; - Circuit 14 for measuring current I, which is equal to the sum of current I1 in electrode 4 and additional current I2 flowing in parallel with I1 in conductive ink 7.

[0047] The power supply device 5 provides the voltage to the circuit 14, and the circuit 14 sends a signal to the electronic device 10 indicating the current I = I1 + I2.

[0048] Programming electronic device 10 (e.g., microprocessor or microcontroller): - To receive the value of the current I measured by circuit 14, and compare the value and / or one or more of the derived values ​​calculated based on the current I with one or more corresponding thresholds; - To provide a signal to stop the printer, and / or a signal indicating contamination on the electrodes, the signal notifying the operator that cleaning is required, and / or a signal to trigger an automatic cleaning step; - Possibly receive and / or send more information to the power supply unit 5 via one or more communication links 25.

[0049] One or more thresholds may be stored in the memory of the electronic device 10, for example, at the factory, before any use of the printer, during a calibration step, or after the first use of the printer.

[0050] Temperature sensor 12 may also be included in the system to provide information about the temperature of the printhead to the electronics 10. In fact, changes in current I or any of its derived values ​​may not indicate contamination, but rather be caused by temperature changes. The correlation between changes in I and / or any of its derived values ​​and temperature changes can indicate that changes in I or any current-based value are caused by said temperature changes rather than by contamination of the electrodes.

[0051] Figure 4A and Figure 4B The results of a test performed on a CIJ printer are shown, in which an undesirable interruption of the ink jet occurred, resulting in contamination of the deflection electrode.

[0052] like Figure 4A As shown (in the case of contamination with standard dye liquid ink), the current I gradually increases until it reaches the threshold It (at t1), which stops the printer. After the ink has dried, the printer can be restarted (at t2), but the electrodes are still stained by the dried ink.

[0053] Figure 4B The experiment demonstrates a test involving two consecutive cleaning operations on an electrode on which black carbon ink has been deposited. The consecutive cleaning resulted in a decrease in the level of current I.

[0054] These results confirm that the present invention can detect ink contamination on the deflection electrode.

[0055] Figure 5A and Figure 5B An electronic device for implementing a circuit of the present invention is illustrated schematically. These devices particularly include: - Power supply 16, such as a PWM-controlled DC-DC converter; the power supply output and voltage V 测试(See below) A comparison is made, and the comparison result drives power supply 5; - Microcontroller 10, which is capable of or can be programmed to compare a measured current I = I1 + I2 (measured by circuit 14, see below) with a threshold and / or calculate one or more derived values ​​of the current over one or more time periods, and may compare any of the values ​​with one or more other thresholds; as explained above, microcontroller 10 may generate a default signal, which is triggered, for example, by one or more of the values ​​mentioned above exceeding one or more thresholds; - High-voltage power generator device 5, which allows the generation of several kilovolts of voltage to be applied to the deflection plate 4 (only one such voltage is generated and applied to the plate 4). Figure 5A On one of the electrodes, two voltages, +V and -V, are generated and applied to... Figure 5B On electrodes 4a and 4b in the middle). - Including circuit 14, such as resistors or a resistor bridge, for measuring the current consumed by the voltage multiplier 54; providing the measured current value to the microcontroller 10; - Voltage divider 17 is used to measure a voltage (e.g., between 0 and 5V) based on or representing the voltage supplied to the deflection electrode 4, and the output of the voltage divider is provided to comparator 18. - Circuit 51 measures the current absorbed by the voltage supply device 52; the measured current value is provided to the microcontroller 10, which reads the current value and adjusts the frequency of the transformer 53 accordingly to minimize current consumption and thus minimize printhead heating. Circuit 52 provides a voltage value between 0 and 5V to transformer 53, the value being determined by the output V of circuits 16 and 17. 测试 Control. As already explained, this may further include a temperature sensor (not shown) capable of measuring the temperature within the printhead. The output value of the temperature sensor may be provided to the microcontroller 10.

[0056] Figure 6 A detailed example of a CIJ printer to which the present invention can be applied is shown. The CIJ printer includes a printhead 1, which is remotely deployed relative to the printer body 20 (also referred to as a console), typically several meters apart, and the hydraulic and electrical functions required to operate and control the printhead are detailed herein. Reference numeral 11 is the medium to be printed using ink droplets produced by the CIJ printer.

[0057] Therefore, the control console includes an ink circuit 100 and a controller 110, which drives the printer and is connected to the printhead via an umbilical cable 15. Alternatively, as disclosed in WO2011 / 098345, electronics may be included in the printhead.

[0058] The umbilical cable 15 connects the console 20 to the printhead 1 and includes hydraulic and electrical connections for supplying hydraulic fluid (ink, solvent) and appropriate voltage and signals to the printhead.

[0059] The printhead 1 includes a set of devices for generating and controlling the jet, namely, an ink droplet generator 2, a charging electrode 7, a possible device for detecting ink droplets 8, a set of deflection electrodes 4, and a groove 3 for collecting ink droplets.

[0060] Starting from the droplet generator 2, conductive pressurized ink supplied from the ink circuit 100 is discharged through at least one calibration nozzle 5, thereby forming at least one ink jet 9.

[0061] Under the action of a periodic excitation device (not shown) controlled by a signal from the controller, the ink jet is interrupted at a specific position downstream of the nozzle at regular time intervals corresponding to the period of the excitation signal.

[0062] This forced break in the ink jet typically occurs at the so-called "interruption" point in the jet. The most commonly used excitation device is a piezoelectric ceramic placed in the ink upstream of the nozzle.

[0063] At the so-called "breakpoint" of the jet, the continuous jet transforms into a sequence 9 of identical and regularly spaced ink droplets. This sequence of ink droplets travels along a trajectory corresponding to the jet axis of the ink droplets, which, through the geometry of the printhead, essentially reaches the center of the recovery groove 3.

[0064] A separate charging electrode 7 for each jet is located near the point of interruption in the jet. The charging electrode is designed to selectively charge each of the formed ink droplets to a predetermined charge value. To this end, a specific voltage is applied to the charging electrode 7 while the ink is held at a set potential in the droplet generator; this voltage is different for each ink droplet.

[0065] The amount of charge generated on the jet upstream of the jet interruption point due to electrostatic interaction based on the voltage level of electrode 7 is absorbed by the ink droplet the instant it leaves the jet. The charging voltage to be applied to each jet can be generated by controller 110 (explained in more detail below) and delivered toward printhead 1. It can be noted that this charging control is individual for each jet present in the multi-deflection continuous inkjet head. In fact, the timing of the signal and the charging sequence are different for each jet.

[0066] The charging signal is synchronized with the excitation signal, but has a phase lag specific to each jet, as determined by the device described below.

[0067] Device 8 for detecting ink droplets can be located downstream of charging electrode 7, providing a signal to controller 110 that allows the controller to measure the actual charge applied to the ink droplets and the velocity of these droplets in the printhead. Device 8 senses a current caused by capacitive effects as a particular charged ink droplet passes near the sensing surface of one or more electrostatic sensors. An example of this type of device is described in Markem-Imaje's patent FR 2 636 884.

[0068] This signal can be sent to the controller.

[0069] Downstream of the charging electrode, deflection electrodes 4 are placed on either side of the droplet trajectory. Both plates are brought to a fixed relative potential of ± several kilovolts, thereby generating an electric field Ed substantially perpendicular to the droplet trajectory. This potential difference can be generated at the control console 110 and transmitted to the printhead with suitable electrical insulation. These electrodes 4 may be contaminated by ink, such as by... Figure 1A and Figure 1B The explanation given.

[0070] Therefore, the electric field Ed can deflect the charged ink droplets entering between plates 4. The magnitude of the deflection depends on the velocity and charge of these ink droplets. These deflected trajectories 10 detach from the grooves 3 to impact the printing medium 11.

[0071] The placement of ink droplets within the impact matrix of ink droplets to be printed on the medium 11 is achieved by combining individual deflection of the jet ink droplets with relative displacement between the printhead and the medium 11 to be printed.

[0072] The groove 3, used to collect unprinted ink droplets, captures unused ink so that it returns towards the ink circuit 100 for recycling. Unprinted ink droplets are those that are uncharged, or those for which the charge is too small to deflect the droplet and guide it away from the groove.

[0073] Such a device may also include one or more hydraulic components for hydraulic switching, and / or fluid distribution and / or protection components. Some of these components may be passive, such as valves, conduits, or filters. Others may be active, such as solenoid valves, and require electrical control, which may be detailed at controller 110 and transmitted to printhead 1 via umbilical cable 15.

[0074] Different functions of the device can be connected to the controller 110 via conductors, which themselves also pass through the umbilical cable 15.

[0075] The printer control console 21 mainly includes an ink circuit 100, a controller 110 for controlling the printer, and a user interface 120 that allows interaction with the printer.

[0076] Ink circuit 100 mainly performs the following functions: *Supply pressurized ink of sufficient quality and concentration to the droplet generator of printhead 1 (by mixing recycled ink and solvent). *Recover and recycle fluid that was not used for printing and returned from the grooves of printhead 1. *Used for suction and purification of the ink droplet generator located in printhead 1. *Provide solvent to printhead 1 for rinsing during printhead maintenance operations.

[0077] In addition to the functions mentioned above, pressurized air can also be provided to pressurize the printhead, which is useful for protecting the printhead from external contamination.

[0078] Each of these five functions is associated with a conduit that connects the ink circuit 100 and the printhead 1.

[0079] The controller 110 may consist of one or more electronic cards and onboard software packages, which ensure the driving of the ink circuit 100 and the printhead 1.

[0080] Regarding the drive of the printhead, different electronic analog and logic functions can be implemented on the card of the controller 110, and these functions can be used to activate the components of the printhead via the umbilical cable 15.

[0081] In the variant disclosed in WO2011 / 098345, the analog and logic electronics for driving the printhead 1, as well as one or more power supply devices, are implemented by electronic circuitry in the actual printhead 1. In this case, the ink circuit 100 essentially includes the above-described combination. Figure 6 The apparatus already described is designed to ensure the same functions: providing ink, recovering and recycling unused fluid, purifying the droplet generator 2 by suction, providing solvent to the printhead for rinsing, and optionally providing pressurized air for pressurizing the printhead 1.

[0082] This invention offers the following advantages: - Compared to a printer and a circuit that detects the printer's current individually and compares the current with a single threshold, the present invention has increased sensitivity and, for safety reasons, cuts off the power supply to the off-electrode when the current exceeds the threshold. - This invention has the capability to detect (residual) contamination after cleaning operations, shutdowns, or any other operations, before restarting the jet, and to request, recommend, or initiate maintenance procedures. - This invention can detect and analyze the evolution of contamination during the printing process, alert operators that a cleaning process will be needed soon, and allow operators to plan the cleaning process at the optimal time on the production line, rather than suddenly stopping the printer.

Claims

1. A circuit for one or more deflection electrodes (4) in a single-jet or multi-jet continuous inkjet printer, the circuit comprising: - Power supply (5) for providing at least one deflection voltage to the deflection electrode to deflect the ink droplet; The circuit is characterized in that it further includes: - A conductive ink detection unit (5, 10) for detecting the presence of residual dried or liquid conductive ink on or in contact with the deflection electrode, the unit comprising: * Current detector (14), which detects the current supplied by the power source when the at least one deflection voltage is applied; and *Calculator (10), the calculator is programmed to calculate at least one first value derived from the current during a first time period, and to detect the presence of residual dried or liquid conductive ink on or in contact with at least one of the deflection electrodes based on the at least one derived value.

2. The circuit according to claim 1, wherein the at least one derived value includes the current or a statistical value of the time derivative of the current.

3. The circuit according to claim 1 or 2, wherein the calculator (10) is programmed to compare the first derived value with at least one first threshold.

4. The circuit according to any one of claims 1 to 3, wherein the at least one derived value includes the current and a statistical value of the time derivative of the current, and the calculator (10) is programmed to compare the time derivative with at least one second threshold to detect the presence of residual dried or liquid conductive ink on or in contact with the deflection electrode.

5. The circuit according to any one of claims 1 to 4, wherein the calculator (10) is programmed to calculate at least one second derived value of the current during a second time period different from the first time period, and to detect the temporal evolution of the presence of residual dried or liquid conductive ink on or in contact with the deflection electrode based on the at least one second derived value.

6. The circuit according to claim 5, wherein the calculator (10) is programmed to compare the second derived value with at least one third threshold.

7. The circuit according to claim 5 or 6, wherein the second time period is longer than the first time period.

8. The circuit according to any one of claims 1 to 7, wherein the first derived value and / or correspondingly the second derived value at least include: - The maximum value of the current during the first time period and / or correspondingly the second time period, and / or - The minimum value of the current during the first time period and / or correspondingly the second time period, and / or - The difference between the maximum and minimum values ​​during the first time period and / or the corresponding second time period, and / or - The change in current during the first time period and / or correspondingly the second time period, and / or - The average value of the current during the first time period and / or the corresponding second time period.

9. The circuit according to any one of claims 1 to 8, wherein the conductive ink detection unit is programmed to trigger a signal when the presence of residual dried or liquid conductive ink on or in contact with at least one of the deflection electrodes is detected.

10. The circuit according to claim 9, wherein the signal triggers cleaning of at least one of the deflection electrodes (4).

11. The circuit of claim 10, wherein the calculator is programmed to calculate a third derived value of the current supplied by the power source after cleaning at least one of the deflection electrodes (4), in order to detect the presence of residual dried or liquid conductive ink on or in contact with at least one of the deflection electrodes based on the at least one third derived value.

12. The circuit according to claim 11, wherein the calculator (10) is programmed to compare the third derived value with at least one fourth threshold.

13. The circuit according to any one of claims 1 to 12, further comprising: At least one memory is used to store data of the current supplied by the power source, which is used to deflect ink droplets and vary with temperature in the printhead. And a device (12) for measuring the temperature.

14. The circuit of claim 13, further comprising means (10) for comparing a measured current supplied to the electrode with a stored value of the current at the temperature.

15. A method for controlling a single-jet or multi-jet continuous inkjet printer, the printer comprising a droplet generator for forming ink droplets, at least one electrode for charging the ink droplets, and a deflection electrode for deflecting the ink droplets, the method comprising: - Apply at least one deflection voltage to the deflection electrode; as well as - The presence of residual dried or liquid conductive ink on the deflection electrode is detected by the following method: *Measure the current supplied to the deflection electrode when the at least one deflection voltage is applied; *Calculate the first value derived from the current during the first time period; - The presence of residual dried or liquid conductive ink on the deflection electrode is detected based on the first derived value.

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