Device for detecting an air inclusion in a printhead

Abstract

A device (101) for detecting an air inclusion in a printhead assembly (203) of a print bar (102) of an inkjet printing device (100) is described. The device (101) is configured to determine resistance information relating to the internal resistance of one or more ink supply channels of a printhead assembly (203) of the print bar (102) and, based on the resistance information, to determine whether the printhead assembly (203) has an air inclusion or not.

Description

[0001] The invention relates to a device that enables the efficient and reliable detection of an air inclusion in the printhead of a print bar of an inkjet printing device. Such a device according to the preamble of claim 1 is described in publication JP 2013-28 040 A.

[0002] An inkjet printing device for printing onto a recording medium can comprise a print bar with one or more printheads, each with one or more nozzles. The nozzles are each configured to eject ink droplets to print pixels of an image onto the recording medium. The individual printheads of a print bar are supplied with ink by an ink supply system.

[0003] During operation and / or maintenance of a printhead, air can be drawn into the printhead, particularly into the ink chambers of one or more nozzles, through one or more nozzles. Air entrapment in a printhead can impair the print quality of the printing device.

[0004] This document addresses the technical problem of detecting air entrapment in a printhead early and reliably in order to efficiently improve the print quality of a printing device. This problem is solved by the features of independent device claim 1.

[0005] According to one aspect, a device for detecting a printhead assembly of a printbar of an inkjet printing device that has an air inclusion is described. The device is configured to determine resistance information with respect to the internal resistance of one or more ink supply channels of a printhead assembly of the printbar and, based on the resistance information, to determine whether the printhead assembly has an air inclusion or not. Furthermore, the printbar has N different printhead assemblies, with N ≥ 2.

[0006] The device is further configured to sequentially determine resistance information regarding the internal resistance of one or more ink supply channels of exactly one printhead group of the N different printhead groups of the printhead assembly; and, based on the resistance information of the respective printhead group, to determine whether the respective printhead group has an air inclusion or not. The printhead assembly also has a supply valve for each of the N different printhead groups, configured to open or close a printhead supply line from an inlet-side distribution unit to the respective printhead group. The printhead assembly also has a discharge valve for each of the N different printhead groups, configured to open or close a printhead discharge line from the respective printhead group to an outlet-side distribution unit.The device is designed to selectively open the inlet valve and the outlet valve for a specific printhead group in order to determine the resistance information for that specific printhead group; and to close the inlet valve and the outlet valve for the other N-1 printhead groups.

[0007] Furthermore, a method for detecting an air entrapment in a printhead assembly of an inkjet printer is described. The method includes determining resistance information regarding the internal resistance of one or more ink supply channels of a printhead assembly within the printhead assembly. The method further includes determining, based on this resistance information, whether the printhead assembly contains an air entrapment or not.

[0008] Exemplary embodiments of the invention will now be described in more detail with reference to the schematic drawing. These show: Fig. 1 a block diagram of an exemplary inkjet printing device; Fig. 2 an exemplary ink supply system for one or more printheads of a print bar of an inkjet printing device; Fig. Three exemplary pressure measurements for different printheads of a print bar; and Fig. 4 A flowchart of an exemplary procedure for detecting a printhead affected by air entrapment.

[0009] The in Fig. The printing device 100 shown in Figure 1 is designed for printing onto a sheet-shaped, flat, plate-shaped, or web-shaped recording medium 120. The recording medium 120 can be made of paper, cardboard, carton, metal, plastic, textiles, a combination thereof, and / or other suitable and printable materials. The recording medium 120 is guided through the printing unit 140 of the printing device 100 along the transport direction 1, indicated by an arrow.

[0010] In the illustrated example, the printing unit 140 of the printing device 100 comprises two printing bars 102, each printing bar 102 being usable for printing with ink of a specific color, e.g., black, cyan, magenta, and / or yellow, and optionally MICR ink. Different printing bars 102 can be used for printing with different inks. Furthermore, the printing device 100 typically includes at least one fuser or drying unit, which is not integrated into Fig. 1 is shown and is set up to fix a printed image printed on the recording medium 120.

[0011] A print bar 102 can comprise one or more print heads 103, which may be arranged side by side in several rows to print the pixels of different columns 31, 32 of a print image onto the recording medium 120. In the Fig. In the example shown, a print bar 102 comprises five printheads 103, each printhead 103 printing the pixels of a group of columns 31, 32 of a print image onto the recording medium 120. The number of printheads 103 of a print bar 102 can be, for example, 5, 10 or more.

[0012] Each printhead 103 of the printing unit 140 comprises in the Fig. In the embodiment shown in Figure 1, several nozzles 21, 22 are provided, each nozzle 21, 22 being configured to fire or propel ink droplets onto the recording medium 120. For example, a printhead 103 of the printing unit 140 can comprise several thousand effectively used nozzles 21, 22 arranged along several rows transverse to the transport direction 1 of the recording medium 120. By means of the nozzles 21, 22 of a printhead 103 of the printing unit 140, pixels of a line of a printed image can be printed onto the recording medium 120 transverse to the transport direction 1, i.e., along the width of the recording medium 120.

[0013] The printing device 100 further comprises a control device 101, e.g. a control hardware and / or a controller, which is configured to control the actuators of the individual nozzles 21, 22 of the individual printheads 103 of the printing unit 140 in order to apply the printed image to the recording medium 120 depending on print data.

[0014] The printing unit 140 of the printing device 100 thus comprises at least one printing bar 102 with K nozzles 21, 22, which can be arranged in one or more printheads 103 and which can be controlled with a specific line rate to print one line at a time, running transversely to the transport direction 1 of the recording medium 120, with K pixels or K columns 31, 32 of a printed image onto the recording medium 120, e.g. with K>1000. In the illustrated example, the nozzles 21, 22 are fixed in the printing device 100, and the recording medium 120 is moved past the stationary nozzles 21, 22 at a specific transport speed.

[0015] Fig. Figure 2 shows an exemplary ink supply system 200 configured to supply one or more printheads 103 of a print bar 102 with ink 212. One or more printheads 103 can be grouped together to form a printhead group 203, wherein the one or more printheads 103 of a printhead group 203 are supplied with ink 212 via a common ink path, in particular via a common printhead supply line 205 and / or via a common printhead return line 206.

[0016] The ink supply system 200 comprises an ink reservoir 211 for ink 212. Ink 212 can be pumped from an ink reservoir (not shown) into the ink reservoir 211 by means of a pump 210, e.g., a gear pump. Ink 212 from the ink reservoir 211 can be conveyed via a supply line 213 to an inlet-side distribution unit 221. A filter unit 214 for filtering, in particular for cleaning, the ink 212 can be arranged on the supply line 213. Furthermore, a supply valve 215 can be arranged on the supply line 213, which can be opened or closed to change the volume flow of ink 212. The supply valve 215 can be designed such that the degree of opening of the supply valve 215 can be changed continuously, for example between 0% and 100%. The supply valve 215 can be a proportional valve.

[0017] The ink supply system 200 includes an input-side pressure sensor 223, which is configured to detect pressure measurements relating to the physical pressure of the ink 212 in and / or at the input-side distribution unit 221.

[0018] Starting from the input distribution unit 221, the ink 212 can be routed to the individual printhead groups 203. A printhead supply line 205 can run from the input distribution unit 221 to each printhead group 203 to supply ink 212 from the input distribution unit 221 to the respective printhead group 203. Each printhead supply line 205 can be opened or closed by a supply valve 201.

[0019] Furthermore, each printhead branch 206 can lead from the individual printhead groups 203 to an output distribution unit 223, in which the ink 212 from the individual printhead groups 203 is collected. The individual printhead branches 206 can each be opened or closed by a branch valve 202.

[0020] In Fig. Figure 2 shows, by way of example, the printhead supply lines 205, the supply valves 201, the printhead outlets 206, and the outlet valves 202 for two printhead groups 203. Typically, the ink supply system 200 has one printhead supply line 205, one supply valve 201, one printhead outlet 206, and one outlet valve 202 for each printhead group 203 of the print bar 102.

[0021] The ink supply system 200 can include an output-side pressure sensor 224, which is configured to detect pressure measurements relating to the physical pressure of the ink 212 in and / or at the output-side distribution unit 222.

[0022] Ink 212 can be pumped from the output distribution unit 222 into the ink reservoir 211 via a line 226 by means of a (vacuum) pump 225, e.g. a gear pump.

[0023] As previously explained, air may become trapped in a printhead 103 or in a printhead group 203 during operation and / or maintenance of the printing device 100. Such air entrapment has been observed to lead to an increase in the resistance value, i.e., the internal resistance, of the affected printhead 103, or more generally, the affected printhead group 203. The control device 101 of the printing device 100 can be configured to determine resistance information regarding the resistance values, i.e., the internal resistances, of each printhead group 203 for the flow of ink 212 into, through, and / or out of the respective printhead group 203. Based on this resistance information, one or more printhead groups 203 with air entrapment can be identified. In particular, it can be determined that one or more printhead groups 203 have an increased resistance value.exhibit internal resistance that, for example, exceeds a predefined resistance threshold. Based on this, it can be determined that one or more printhead groups 203 contain an air inclusion.

[0024] If a printhead group 203 is identified as having an air inclusion, one or more regeneration measures can be performed specifically for that identified printhead group 203, each aimed at eliminating the air inclusion. For the one or more other printhead groups 203 in which no air inclusion was detected, the one or more regeneration measures can be omitted. This allows for a particularly resource-efficient regeneration of the printhead bar 102.

[0025] Examples of regeneration measures include: • a flushing of the identified printhead group 203 with ink 212; • an increase in the physical pressure of the ink 212 in the identified printhead group 203; and / or • causing one or more specific ejection pulses of the nozzles 21, 22 of the identified printhead group 203 to expel the trapped air from the chambers of the nozzles 21, 22 of the identified printhead group 203.

[0026] The control device 101 can be configured to operate a printhead 102 in a verification mode designed to identify one or more printhead groups 203 that have an air inclusion. The verification mode can be performed, for example, following a maintenance procedure for the printhead 102 to verify that the maintenance was carried out correctly. Alternatively or additionally, the verification mode can be performed between different printing phases and / or before the start of a printing phase of the printing device 100.

[0027] When air is trapped in a printhead 103, the internal resistance of one or more ink supply channels of the printhead 103 increases. This is because the air acts as resistance in the cavities of the printhead 103. The ink supply system 200 can be used to detect an air entrapment in a printhead 103, or more generally, in a group of printheads 203.

[0028] The printhead assembly 102 under investigation has N different printhead groups 203, with N ≥ 1, in particular N ≥ 2, and typically N ≥ 4. Each printhead group 203 can have one or more printheads 103 arranged parallel to each other with respect to ink supply. The ink supply system 200 comprises a supply valve 201 and a discharge valve 202 for each individual printhead group 203.

[0029] The valves 201 and 202 of the N printhead groups 203 can initially be closed for the verification mode. A specific, in particular constant, verification pressure of the ink 212 can be set in the inlet-side distribution unit 221 of the ink supply system 200. For this purpose, pressure readings from the inlet-side pressure sensor 223 can be acquired. The pump 210 can be operated based on the pressure readings from the inlet-side pressure sensor 223, in particular using a control loop, to set the specific verification pressure in the inlet-side distribution unit 221. Furthermore, the supply valve 215 can be set to a specific, in particular constant, degree of opening.

[0030] Following the setting of the verification print, the inlet valve 201 and the outlet valve 202 can be selectively opened for exactly one printhead group 203 in order to verify that printhead group 203. As a result, ink 212 flows from the inlet distributor 221 through the printhead group 203, specifically through the one or more ink supply channels of the printhead group 203, to the outlet distributor 222.

[0031] The (vacuum) pump 225 on the output distributor unit 222 can be operated to adjust the physical pressure of the ink 212 in the output distributor unit 222 to a specific target pressure. For this purpose, pressure readings from the output pressure sensor 224 can be acquired. The pump 225 can be operated based on the pressure readings from the output pressure sensor 224, in particular using a control loop, to adjust the specific target pressure in the output distributor unit 222.

[0032] The inlet pressure sensor 223 can be used to measure the ink pressure in the inlet distribution unit 221. If the printhead assembly 203 under investigation has no air entrapment and therefore a relatively low internal resistance, the ink pressure in the inlet distribution unit 221 will be relatively low. Conversely, if the printhead assembly 203 has an air entrapment and consequently an increased internal resistance, the ink pressure in the inlet distribution unit 221 will rise. This can be detected based on the pressure readings from the inlet pressure sensor 223. Furthermore, the pressure increase typically leads to a reduction in the delivery rate and / or the rotational speed of the pump 210, which can be used as an alternative or supplementary indicator of the presence of an air entrapment.

[0033] In a corresponding manner, the N different printhead groups 203 of the print bar 102 can be checked sequentially. Fig. Figure 3 shows exemplary pressure measurements 310 of the input-side pressure sensor 223 for the N different printhead groups 203 of the print bar 102, where the different printhead groups 203 are identified by the index n, with n=1,..., N. The one or more pressure measurements 310 recorded for a printhead group 203 n can be compared with a pressure threshold value 311. Based on the comparison, it can be determined whether the respective printhead group 203 has an air inclusion or not. In the Fig. In the example shown in Figure 3, the printhead group 203 identified with index 301 has an air inclusion, in particular because the one or more pressure readings 310 for this printhead group 203 are greater than the pressure threshold 311.

[0034] If a printhead group 203 is identified as having air entrapment, the drain valve 202 of the identified printhead group 203 can be closed to perform one or more regeneration measures for that group. These one or more regeneration measures can be performed individually for each identified printhead group 203, so that they do not need to be performed for all N printhead groups 203 of the printhead bar 102.

[0035] Fig.Figure 4 shows a flowchart of an exemplary, optionally computer-implemented, method 400 for detecting a printhead assembly 203 of a print bar 102 of an inkjet printing device 100 that has an air inclusion. The method 400 comprises determining 401 resistance information relating to the internal resistance of one or more ink supply channels of a printhead assembly 203 of the print bar 102. The one or more ink supply channels of the printhead assembly 203 may be configured to convey ink 212 from the ink inlet of the printhead assembly 203 to the ink outlet of the printhead assembly 203. The internal resistance may refer to the resistance for ink 212 flowing through the one or more ink supply channels of the printhead assembly 203.The resistance information can include one or more pressure readings 310, in particular one or more pressure readings 310 relating to the pressure of the ink 212 in the input distributor unit 221. The resistance information can be determined while the printing device 100, the print bar 102 and / or the ink supply system 200 are operated in a specific verification mode designed to check the one or more printhead groups 203, in particular the N printhead groups 203, of the print bar 102 for the presence of an air inclusion.

[0036] Method 400 further comprises determining, based on the resistance information, whether the printhead assembly 203 has an air inclusion or not. In particular, it can be determined whether the internal resistance of one or more ink supply channels of the printhead assembly 203 is greater or less than a specified (resistance) threshold. If the internal resistance is greater than the specified threshold, it can be determined that an air inclusion is present. Conversely, it can be determined that no air inclusion is present.

[0037] A (control) device 101 for detecting a printhead group 203 of a print bar 102 of an inkjet printing device 100, which has an air inclusion, is thus described. The (control) device 101 can be part of the printing device 100. The print bar 102 can have N different printhead groups 203, with N≥1 or N≥2, in particular N≥4. The individual printhead groups 203 can each have one or more printheads 103, which can be arranged parallel to each other with respect to the ink supply.

[0038] The individual printhead groups 203 can each have one or more ink supply channels configured to direct ink 212 through the respective printhead group 203 in order to supply the nozzles 21, 22 of the respective printhead group 203 with ink 212. The ink 212 can be supplied at an inlet of the one or more ink supply channels and can then flow through the one or more ink supply channels. At least some of the ink 212 can be supplied again at the outlet of the one or more ink supply channels.

[0039] The printing device 100 can have an ink supply system 200 configured to supply ink 212 to the N printhead groups 203 of the print bar 102. The ink supply system 200 of the printing device 100, in particular of the print bar 102, can have an inlet-side distribution unit 221 configured to supply ink 212 to the inlet of the one or more ink supply channels of the N different printhead groups 203 of the print bar 102. Alternatively or additionally, the ink supply system 200 of the printing device 100, in particular of the print bar 102, can have an outlet-side distribution unit 222 configured to receive ink 212 from the outlet of the one or more ink supply channels of the N different printhead groups 203 of the print bar 102.

[0040] The pressure bar 102 can have a supply valve 201 for each of the N different printhead groups 203, configured to open or close a printhead supply line 205 from the inlet distributor unit 221 to the respective printhead group 203. Furthermore, the pressure bar 102 can have a discharge valve 202 for each of the N different printhead groups 203, configured to open or close a printhead discharge line 206 from the respective printhead group 203 to the outlet distributor unit 222. The supply valves 201 and / or the discharge valves 202 of the N printhead groups 203 thus enable a selective supply of ink 212 to the individual printhead groups 203.

[0041] The ink supply system 200 can include an input pressure sensor 223 configured to detect one or more pressure readings 310 relating to the pressure of the ink 212 in the input distribution unit 221. Alternatively or additionally, the ink supply system 200 can include an output pressure sensor 224 configured to detect one or more pressure readings relating to the pressure of the ink 212 in the output distribution unit 221.

[0042] The ink supply system 100 can include a supply valve 215 configured to change the volume flow of ink 212 into the inlet-side distributor unit 221 by changing the degree of opening of the supply valve 215. The supply valve 215 is preferably configured such that the degree of opening can be adjusted, in particular substantially continuously, between 0%, i.e., completely closed, and 100%, i.e., completely open.

[0043] The ink supply system 100 can include an inlet pump 210 configured to deliver ink 212, in particular via and / or from an ink reservoir 211 and / or via the supply valve 215, into the inlet distribution unit 221. This ensures a reliable supply of ink 212 to the N printhead groups 203.

[0044] The ink supply system 100 can have an output pump 225 configured to pump ink 212 out of the output distributor unit 222, and in particular into the ink reservoir 211. This ensures a reliable flow of ink 212 through the N printhead groups 203.

[0045] The (control) device 101 is configured to determine resistance information relating to the internal resistance of one or more ink supply channels of a printhead group 203 of the print bar 102. The resistance information can be determined while the print bar 102 is operated in a specific verification mode.

[0046] The device 101 can be configured to selectively open the supply valve 201 and the discharge valve 202 for a specific printhead group 203 in order to determine its resistance information. The device 101 can also be configured to close the supply valve 201 and the discharge valve 202 for the other N-1 printhead groups 203. Thus, to determine the resistance information for a specific printhead group 203, ink 212 can be supplied exclusively through the one or more ink supply channels of the specific printhead group 203, and not through the one or more ink supply channels of the other N-1 printhead groups 203. In this way, the resistance information for the specific printhead group 203 can be determined with particular precision.

[0047] The device 101 is further configured to determine, based on the resistance information, whether the printhead group 203 has an air inclusion or not.

[0048] The device 101 can be configured to sequentially and / or successively determine resistance information regarding the internal resistance of one or more ink supply channels of exactly one printhead group 203 of the N different printhead groups 203 of the print bar 102. Thus, resistance information for the individual printhead groups 203 of the print bar 102 can be determined successively. For this purpose, the supply valve 201 and / or the discharge valve 202 of the respective printhead group 203 can be selectively opened, while the supply valve 201 and / or the discharge valve 202 of the N-1 other printhead groups 203 are closed.

[0049] Based on the resistance information of each printhead group 203, it can be determined whether the respective printhead group 203 has an air inclusion or not. In particular, the one or more printhead groups 203 that have an air inclusion can be identified from the N printhead groups 203.

[0050] By determining and taking into account resistance information, an air inclusion in a printhead group 203 can be detected in a particularly efficient and reliable manner.

[0051] The device 101 can further be configured to selectively perform one or more regeneration measures to regenerate the one or more identified printhead groups 203. In particular, the one or more identified printhead groups 203 can be selectively flushed with ink 212 to eliminate air entrapment, while no regeneration measures are performed for the other one or more printhead groups 203. This allows for particularly efficient regeneration of the printhead bar 102.

[0052] The device 101 can be configured to test a specific printhead group 203 by generating a predefined pressure differential between the inlet and outlet of one or more ink supply channels of the specific printhead group 203. This can be achieved by operating the inlet pump 210 and / or the outlet pump 225.

[0053] The device 101 can further be configured to determine volumetric flow information regarding the volumetric flow rate of ink 212 from the inlet to the outlet of one or more ink supply channels of the specific printhead group 203. This can be determined, for example, based on the rotational speed of the inlet pump 210 and / or on the opening degree of the supply valve 215. The resistance information can then be determined based on the volumetric flow information, in particular based on the ratio between the predefined pressure differential and the volumetric flow rate.

[0054] Alternatively or additionally, the device 101 can be configured to test the specific printhead group 203 by causing a predefined volume flow of ink 212 from the inlet to the outlet of one or more ink supply channels of the specific printhead group 203. This can be achieved, for example, by operating the inlet pump 210 and / or by adjusting the opening degree of the supply valve 215.

[0055] The device can further be configured to determine pressure information relating to the pressure differential between the inlet and outlet of one or more ink supply channels of the specific printhead group 203. The pressure information can be determined based on one or more pressure readings from the inlet-side pressure sensor 223 and / or the outlet-side pressure sensor 224. The resistance information can then be determined based on the pressure information, in particular based on the ratio between the pressure differential and the predefined volumetric flow rate.

[0056] The device 101 can be configured to determine the resistance information in order to adjust the pressure of the ink 212 in the output distribution unit 222 to a specific target pressure. The output pump 225 can be operated, in particular depending on one or more pressure readings of the ink 212 pressure in the output distribution unit 222, i.e., in particular depending on one or more pressure readings from the output pressure sensor 224, in order to adjust the pressure of the ink 212 in the output distribution unit 222 to the target pressure.

[0057] The device 101 can further be configured to operate the supply valve 215 for determining the resistance information in such a way that the volume flow of ink 212 into the inlet-side distribution unit 221 is essentially constant. Alternatively or additionally, the opening degree of the supply valve 215 for determining the resistance information can be kept essentially constant.

[0058] The device 101 can further be configured to detect at least one pressure measurement 310 of the pressure of the ink 212 in the input-side distribution unit 221, in particular by means of the input-side pressure sensor 223. The resistance information relating to the internal resistance of the one or more ink supply channels of the respective printhead group 203 can then be determined in a particularly efficient and precise manner based on the pressure measurement 310. The resistance information can in particular include or correspond to the pressure measurement 310.

[0059] The device 101 can, for example, be configured to compare the pressure measurement 310 of the ink pressure 212 in the input-side distribution unit 221 with a pressure threshold value 311. It can then be determined, based on this comparison, whether the printhead assembly 203 has an air inclusion or not.

[0060] Alternatively or additionally, the device 101 can be configured to determine the resistance information based on the rotational speed of the input pump 210, while ink 212 is conveyed from the input distributor unit 221 through the one or more ink supply channels of the respective printhead group 203 to the output distributor unit 222.

[0061] Alternatively or additionally, the device 101 can be configured to adjust the pressure of the ink 212 in the inlet distribution unit 221 to a target pressure and to effect a specific volume flow of ink 202 at the line 226 from the outlet distribution unit 222, in particular by operating the outlet pump 225. One or more pressure measurements of the ink 212 in or at the outlet distribution unit 222 can then be recorded, and the resistance information can be determined based on these one or more pressure measurements.

[0062] Furthermore, this document describes an inkjet printing device 100 with an ink supply system 200, wherein the printing device 100 comprises the control device 101 described in this document. Reference symbol list 1. Transport direction (of the recording medium) 21, 22 nozzle Columns 31 and 32 (of the printed image) 100 printing device 101 (Control) device 102 pressure bars 103 Printhead 120 recording media 140 printed works 200 ink supply system 201 Supply valve 202 Drainage valve 203 Printhead group 205 Printhead supply 206 Printhead derivation 210 inlet pump 211 ink tanks 212 ink 213 Supply line 214 filter unit 215 Supply valve 221 input-side distribution unit 222 output-side distribution unit 223 Input pressure sensor 224 output side pressure sensor 225 output-side (vacuum) pump 226 Derivative 301 Index (Printhead Group) 310 Printhead reading 311 Pressure threshold 400 methods for detecting a printhead with air entrapment 401-402 Procedure steps

Claims

[1] Device (101) for detecting a printhead assembly (203) of a print bar (102) of an inkjet printing device (100) with an air inclusion; wherein the device (101) is configured, - To determine resistance information relating to an internal resistance of one or more ink supply channels of a printhead group (203) of the print bar (102); and - to determine, based on the resistance information, whether the printhead assembly (203) has an air inclusion or not - the pressure bar (102) has N different printhead groups (203), with N ≥ 2; and - the device (101) is set up, -- sequentially determine resistance information relating to the internal resistance of one or more ink supply channels of exactly one printhead group (203) of the N different printhead groups (203) of the print bar (102); and -- to determine, based on the resistance information of the respective printhead group (203), whether the respective printhead group (203) has an air inclusion or not, characterized by , that - the pressure bar (102) for the N different printhead groups (203) each has a supply valve (201) which is designed to open or close a printhead supply line (205) from an input-side distributor unit (221) to the respective printhead group (203); - the pressure bar (102) for the N different printhead groups (203) each has a drain valve (202) which is designed to open or close a printhead drain (206) from the respective printhead group (203) to an output-side distributor unit (222); and - the device (101) is set up to determine the resistance information for a specific printhead group (203) -- selectively open the inlet valve (201) and the outlet valve (202) for the specific printhead group (203); and - to close the inlet valve (201) and the outlet valve (202) for the N-1 other printhead groups (203). [2] Device (101) according to claim 1, wherein the device (101) is configured, - to cause a predefined pressure difference between an input and an output of the one or more ink supply channels of the printhead group (203); - To determine volume flow information relating to a volume flow of ink (212) from the inlet to the outlet of the one or more ink supply channels of the printhead assembly (203); and - to determine the resistance information based on the volume flow information; and / or - to effect a predefined volume flow of ink (212) from the inlet to the outlet of the one or more ink supply channels of the printhead group (203); - To determine print information relating to a pressure difference between the input and output of one or more ink supply channels of the printhead group (203); and - to determine the resistance information based on the pressure information. [3] Device (101) according to one of the preceding claims, wherein - an ink supply system (200) of the printing device (100) comprising an inlet-side distribution unit (221) configured to supply ink (212) to an inlet of the one or more ink supply channels of the printhead assembly (203) of the print bar (102); - the ink supply system (200) of the printing device (100) comprises an output-side distribution unit (222) configured to receive ink (212) from an output of the one or more ink supply channels of the printhead assembly (203) of the print bar (102); and - the device (101) is set up, -- to adjust the pressure of the ink (212) in the output distribution unit (222) to a target pressure; -- to record a pressure measurement (310) of the pressure of the ink (212) in the input-side distribution unit (221); and -- to determine the resistance information relating to the internal resistance of one or more ink supply channels of the printhead group (203) based on the print measurement value (310). [4] Device (101) according to claim 3, wherein the device (101) is configured, - to compare the pressure measurement (310) of the ink pressure (212) in the inlet distribution unit (221) with a pressure threshold value (311); and - to determine, based on the comparison, whether the printhead assembly (203) has an air inclusion or not. [5] Device (101) according to one of claims 3 to 4, wherein - the ink supply system (200) comprises a pump (225) configured to pump ink (212) out of the output-side distribution unit (222), and in particular into an ink reservoir (211); and - the device (101) is set up to operate the pump (225), in particular depending on one or more pressure readings of the pressure of the ink (212) in the output distribution unit (222), in order to adjust the pressure of the ink (212) in the output distribution unit (222) to the target pressure. [6] Device (101) according to any one of claims 3 to 5, wherein - the ink supply system (200) comprises a supply valve (215) configured to change the volume flow of ink (212) into the inlet-side distribution unit (221) by changing the degree of opening of the supply valve (215); and - the device (101) is set up, -- to operate the supply valve (215) for determining the resistance information in such a way that the volume flow of ink (212) into the inlet-side distribution unit (221) is essentially constant; and -- to keep the degree of opening of the supply valve (215) essentially constant for determining the resistance information. [7] Device (101) according to any one of claims 3 to 6, wherein - the ink supply system (200) comprises a pump (210) configured to deliver ink (212), in particular via an ink reservoir (211) and / or via a supply valve (215), into the inlet distribution unit (221); and - the device (101) is set up to determine the resistance information based on the rotational speed of the pump (210) while ink (212) is conveyed from the inlet distribution unit (221) through the one or more ink supply channels of the printhead assembly (203) to the outlet distribution unit (222).

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