Method and device for correcting a printing pattern for printing containers

Abstract

Direct printing method for printing a container (102) with a print image (109) by means of a direct printing device (108) comprising a direct printhead (107) with at least one row of print nozzles (105) and an ink mist extraction system (106), wherein for at least one pixel of a print template for the print image, a pixel offset is determined based on a model for a print deviation (113, 118) caused by the ink mist extraction system along the row of print nozzles from a normal print value (111), wherein a corrected print template is generated based on the determined pixel offset, and wherein the print image is applied to the container by means of the direct printing device based on the corrected print template.

Description

[0001] The present invention relates to methods for correcting a printing template for printing on containers according to independent claims 1, 7 and 10, and to corresponding devices for correcting a printing template for printing on containers according to independent claims 5, 9 and 13. State of the art

[0002] Correcting a printing template to avoid distortions of a printed image applied to a container surface based on the printing template is known from the prior art.

[0003] For example, it is known to control the ejection time of ink droplets from different print nozzles of a direct printing device based on the surface shape of the container to be printed. This allows for compensation of different distances to the container surface for different print nozzles and prevents any resulting distortion of the printed image.

[0004] German patent DE 10 2017 215 429 A1 discloses a direct printing method for a direct printing machine for printing on containers, particularly shaped containers, using direct printing. In this method, a 3D printing model is created from 3D data of the containers, a printing path of the direct printing machine, and printing parameters of the direct printing machine to predict the representation of a print graphic template onto the containers as a direct print. Using the 3D printing model, a macroscopic correction and a microscopic correction are then determined, the macroscopic correction comprising the inverse of a distortion of the print graphic template on the containers and the microscopic correction comprising a nozzle correction. The print graphic template is then corrected with the macroscopic correction and stored in a corrected print graphic, from which a print raster image is generated using a raster image processor.The printed halftone image is then corrected based on microscopic correction and stored as a corrected printed halftone image and printed directly onto the containers using the direct printing machine.

[0005] While methods known from the prior art allow for the correction of a printing template to compensate for certain effects that cause distortions in the printed image, other effects that are also responsible for distortions of the printed image are not addressed in the known prior art, so distortions of the printed image may remain. Task

[0006] Starting from the prior art, the problem to be solved by the present invention is to provide a method and a device for correcting a printing template in order to compensate for undesirable distortions of a printed image applied to a container surface caused by various interfering effects. Solution

[0007] The object of the invention is achieved by the methods for correcting a printing template for printing on containers according to claims 1, 7 and 10, and the corresponding devices for correcting a printing template for printing on containers according to independent claims 5, 9 and 13. Preferred embodiments are specified in the dependent claims.

[0008] In the direct printing method according to the invention for printing a container with a print image by means of a direct printing device comprising a direct print head with at least one row of print nozzles and an ink mist extraction system, a pixel offset is determined for at least one pixel of a print template for the print image based on a model for a pressure deviation from a normal pressure value caused by the ink mist extraction along the row of print nozzles, a corrected print template is generated based on the determined pixel offset and the print image is applied to the container by means of the direct printing device based on the corrected print template.

[0009] This process can be used to print on various types of containers, preferably bottles made of glass, plastic, or fiber-based materials used in the beverage industry. However, the process is not limited to the aforementioned types of containers and can also be used, for example, to print on cups, glasses, cans, or tubes such as those used in the beverage, pharmaceutical, healthcare, or food industries, or any other container suitable for holding a liquid or pasty medium.

[0010] The term "pressure value" can refer, for example, to the position (coordinate) of a pressure point applied to the container surface by means of a pressure nozzle of the direct printing device. Alternatively, it can also refer to the pressure (atmospheric pressure) applied to a pressure nozzle of the direct printing device.

[0011] The term "normal pressure value" refers to a reference pressure value, which can be the position of a print point applied by one of the print nozzles of the direct printing device without ink mist extraction (or with ink mist extraction switched off) onto a reference surface (for example, a container surface). The normal pressure value can be described, for example, by normal pressure value coordinates. In one embodiment, the normal pressure values ​​for the print nozzles of a print nozzle array or the print nozzles of the direct printhead can be described by a normal pressure value function, by means of which an associated normal pressure value can be determined for any print nozzle position of the print nozzle array or the direct printhead.Alternatively, the normal pressure value can also refer to normal air pressure applied to a print nozzle of the print nozzle series without ink mist extraction (or with ink mist extraction switched off).

[0012] The term "print template" can refer, for example, to a raster image of the print design, which is to be applied to the container surface using a direct printing device. The raster image can be generated, for instance, using a rasterization process based on the print design, whereby the print design itself can be either a raster or vector print design.

[0013] Ink mist extraction refers to an extraction device that can remove the ink mist generated by the direct printing device during printing from a printing area, thus preventing contamination of the direct printing device or the container surface by the ink mist. The ink mist comprises ink droplets that preferably have a significantly smaller volume than the ink droplets ejected by the print nozzles to create the printed image. Significantly smaller volume means, for example, a volume that is at least one order of magnitude smaller than the volume of the ink droplets intended to create the printed image.

[0014] The model refers in particular to a mathematical relationship that assigns to at least one of the print nozzles of the direct printhead, and thus to at least one of the pixels of the print template, a pressure deviation of a corresponding print point applied to the container surface from a standard pressure value, caused by ink mist extraction. This pressure deviation can be a relative displacement Δx of the print point (or its position or coordinate) with respect to the standard pressure value x (or the standard pressure position or coordinate). For example, the relative displacement can be a vector. If the displacement occurs along a specific preferred direction, it can also be a scalar.For example, the mathematical relationship could be a pressure deviation function, based on which a corresponding pressure deviation of a print point applied to the container surface from a standard atmospheric pressure value can be determined for a specific print nozzle coordinate. Alternatively, if the pressure value is an atmospheric pressure value, the model could describe a mathematical relationship that assigns an atmospheric pressure deviation from standard atmospheric pressure to at least one of the print nozzles of the direct printhead, caused by ink mist extraction. From this, a pixel offset and / or the corrected print template can then be determined.

[0015] Thus, based on the model of the pressure deviation of a print point applied to the container surface (or its coordinate or position) caused by the pressure extraction from a normal pressure value, or an air pressure deviation from a normal air pressure value caused at a print nozzle and the pixel offset determined from this, a deflection of the trajectory of the ink droplets ejected by the direct printing device caused by the ink mist extraction and a resulting distortion of the printed image can be corrected and a high-quality printed layer can be produced on the container surface.

[0016] In one embodiment, the pressure deviation model is determined based on a maximum pressure deviation from the normal pressure value at a position in the nozzle array, a first pressure deviation from the normal pressure value at a first nozzle located at one end of the nozzle array, and a second pressure deviation from the normal pressure value at a second nozzle located at the other end of the nozzle array. The maximum pressure deviation is the pressure deviation with the largest magnitude of all pressure deviations. A nozzle located at one end of the nozzle array preferably refers to one of the two outermost nozzles in the array, i.e., a nozzle with only one neighbor.In one embodiment, however, it can also be provided that an end refers to an outer region of the nozzle array, which may comprise a specific number of nozzles, such as three or five, arranged at one end of the nozzle array. Since only three parameters are required for modeling, the pressure deviation model can be determined in a particularly efficient manner. In particular, it is not necessary to determine the pressure deviations along each of the nozzles in the nozzle array.

[0017] In a further development of this embodiment, if the maximum pressure deviation lies at a position between the first and second print nozzles, the pressure deviation along the print nozzle array is determined in a first region of the print nozzle array by linear interpolation between the first pressure deviation and the maximum pressure deviation, and in a second region of the print nozzle array by linear interpolation between the second pressure deviation and the maximum pressure deviation. By dividing the pressure deviation into two regions and by linear interpolation between the first pressure deviation and the maximum pressure deviation, as well as between the second pressure deviation and the maximum pressure deviation, the actual pressure deviation along the print nozzle can be approximated with sufficient accuracy.

[0018] In a further development of one of the preceding embodiments, the pixel offset is determined based on the printing deviation model for at least one pixel row of the print template. This allows for a particularly time-efficient determination of the pixel offset, since the pixel offset does not have to be determined individually for each pixel position.

[0019] According to the invention, a direct printing device for printing on a container is also provided, wherein the direct printing device comprises a direct printhead with a plurality of print nozzles, an ink mist extraction system and a control unit, wherein the print nozzles are arranged in at least one print nozzle row and the control unit is configured to carry out the method according to one of the preceding embodiments.

[0020] Based on the pixel offset determined using the model of the pressure deviation from a normal pressure value and the correspondingly corrected print template, the direct printing device according to the invention can apply a distortion-free and high-quality printed image to the container surface and thus compensate for the offset of print points caused by the ink mist extraction.

[0021] In a further development of this embodiment, the ink mist extraction system is arranged on a side surface of the direct printhead. This arrangement of the ink mist extraction system allows for particularly efficient extraction of the ink mist and minimizes any influence on the trajectory of the ink droplets ejected through the print nozzle openings.

[0022] In a further direct printing method according to the invention for printing on an irregular container, at least one pixel line with a pixel number n of a print template for a print image based on a shape of a surface area of ​​the irregular container is extended by a pixel number m and the information contained in the original pixel line is scaled to the extended pixel line, wherein a corrected print template is generated based on the at least one extended pixel line and the print image is applied to the surface area of ​​the irregular container by means of a direct printing device with a plurality of printing nozzles based on the corrected print template.

[0023] A pixel row is understood to be a series of pixels arranged along any direction in the print template. Preferably, the pixel row is a series of pixels arranged either along a horizontal or a vertical direction in the print template.

[0024] An irregular container is defined as a container whose surface deviates from an ideal shape, such as an ideal cylinder. This includes, for example, a container whose surface has at least a partial conical shape, such as a container with a cylindrical base and a conical shoulder. Containers with embossing or debossing can also be classified as irregular containers.

[0025] The shape of the surface area refers to the three-dimensional structure of the surface area onto which the printed image is to be applied. The shape of the surface area can, for example, be described by a multitude of surface coordinates and may deviate from the ideal shape for an irregular container.

[0026] By extending a pixel line based on the shape of a surface area of ​​the irregular container and generating a corrected print template, distortions in the printed image caused by the irregular surface of the container can be compensated for and the quality of the applied printed image can be increased.

[0027] In one embodiment, scaling the information contained in the original pixel row to the extended pixel row involves interpolation between two adjacent pixels of the original pixel row. Thus, the pixel row of the print template can be extended relatively easily without adversely affecting the quality of the printed image through scaling.

[0028] Another direct printing device according to the invention for printing on an irregular container comprises a direct print head with a plurality of print nozzles, wherein the print nozzles are arranged in at least one print nozzle row, and a control unit, wherein the control unit is configured to carry out the method according to one of the preceding embodiments of the direct printing method for printing on the irregular container.

[0029] The direct printing device thus allows a high-quality print image to be applied to the container surface based on the corrected print template, which was generated based on the extended pixel line, and which in particular does not have any distortions caused by the irregular container surface.

[0030] In a further direct printing method according to the invention for printing on a container, a pixel offset is determined for at least one pixel of a print template for a print image based on an offset of a first print nozzle arranged on one side of a direct printhead comprising print nozzles and a second print nozzle arranged on an opposite side of the direct printhead with respect to a print plane, wherein a corrected print template is generated based on the determined pixel offset, wherein the print image is applied to the container by means of the direct printing device based on the corrected print template.

[0031] The term "printing plane" preferably refers to a plane which, in the case of a specific standard orientation of the direct printhead relative to a surface to be printed, either runs exactly parallel to the directions along which a first ink droplet is ejected by the first and a second ink droplet by the second print nozzle of the direct printhead, or is exactly perpendicular to these two directions. Consequently, an offset between the first and second print nozzles and the printing plane only exists if the printhead is rotated or tilted relative to its specific standard orientation.

[0032] Based on the offset, a pixel offset can be determined for at least one pixel of the print template, and a corrected print template can be generated based on this pixel offset. Using the corrected print template, a print image error caused by a tilting or rotating printhead can be corrected, thus improving the quality of the printed image applied to the container surface.

[0033] In a further embodiment, the print nozzles of the direct printhead can be arranged in at least one print nozzle row, and the pixel offset can be determined based on an offset of a first print nozzle located at one end of a print nozzle row and a second print nozzle located at the other end of the print nozzle row with respect to the print plane, and / or the pixel offset can be determined based on an offset between a first print nozzle of a first print nozzle row located at one end of the direct printhead and a second print nozzle of a second print nozzle row located at the other end of the direct printhead with respect to the print plane. Since the offset with respect to the print plane is greatest in these areas of the direct printhead, the accuracy of the determined pixel offset can be increased, and thus the quality of the corrected print image can be further improved.

[0034] In a further development of one of the two preceding embodiments, the pixel offset is determined based on the maximum number of print nozzles of the direct printhead and the position of the pixel. The use of these additional parameters enables the most accurate possible determination of the pixel offset and thus the most precise correction of the printed image.

[0035] According to the invention, a direct printing device for printing on a container is further provided, wherein the direct printing device comprises a direct print head with a plurality of print nozzles and a control unit, wherein the print nozzles are arranged in at least one row of print nozzles and the control unit is configured to carry out the method for printing on a container according to one of the three preceding embodiments.

[0036] Thus, the direct printing device can compensate for pixel offset caused by tilting or twisting, ensuring the application of a high-quality printed image to the container surface.

[0037] In one embodiment of the previously discussed direct printing methods, the print template can be divided into different color layers, and a corrected print template can be created for each color layer. This allows for distortion-free application of colored print images. Brief character description

[0038] Fig. 1a and b: Method for determining a pixel offset to correct a print deviation caused by ink mist extraction according to one embodiment Fig. 2: Method for pixel expansion to correct an irregular container surface according to one embodiment Fig. 3Method for correcting a print template in case of misalignment of a direct printhead Detailed character description

[0039] Figure 1a and b Figure 1 shows a printing device 100, and a printed image applied to a container surface by the printing device 100, as well as a model of a print deviation 110 caused by ink mist extraction from the direct printing device according to an embodiment.

[0040] According to the invention, it is provided to determine a pixel offset for at least one pixel of a print template based on the model for the print deviation from a normal print value 111 caused by the ink mist extraction 113, 118 along a print nozzle row 105 of a direct print head 107 of a direct printing device 108.

[0041] Based on the determined pixel offset, a corrected print template can be generated, whereby in the corrected print template an offset of the print points of the print image caused by the ink mist extraction 106 is compensated and based on the corrected print template a distortion-free print image can be applied to a surface 101 of a container 102.

[0042] Container 102 is preferably a bottle made of glass, plastic, or fiber-based material used in the beverage industry. Alternatively, it could also be, for example, a cup, glass, can, or tube such as those used in the beverage, pharmaceutical, healthcare, or food industries, or any other container suitable for holding a liquid or pasty medium.

[0043] As in connection with the Figure 1aAs shown, the direct printing device 108 can comprise a direct printhead 107 with a plurality of print nozzles 104, wherein the print nozzles are arranged along a print nozzle row 105 and are configured to eject ink droplets 103. The direct printing device 108 can include a control unit (not shown here) configured to control the print nozzles 104 of the direct printing device 108 based on a print template and to produce a printed image 109 on a surface 101 of a container 102. In the embodiment shown here, the print nozzle row 105 is aligned parallel with respect to a longitudinal axis 119 of the container, such that a print line 109 applied to the container surface 101 by the print nozzle row 105 runs exactly parallel to the container's longitudinal axis 119. However, this alignment between the print nozzle row 105 and the container's longitudinal axis 119 is to be understood as exemplary.The print nozzle array 105 can, for example, also be positioned at an angle α with respect to the longitudinal axis 119 of the container, which can increase the print resolution when applying a print image along the circumference of the container.

[0044] To apply a printed image along the circumference of the container 102 onto its surface 101, the container can, in one embodiment, be rotatably mounted about its longitudinal axis 119 relative to the direct printing device 108. For this purpose, the container 102 can, for example, be arranged on a rotary table by means of which the container can be rotated about its longitudinal axis 119. The rotary table can, for example, be driven by a servo motor. Alternatively, the rotary table can also be configured as a container holder for a rotary machine of a container treatment system, and the direct printing device 108 can be arranged stationary along the periphery of the rotary machine. It is also possible for the direct printing device 108 to be associated with the container holder.In another alternative embodiment, it can be provided that the direct printing device 108 is movably arranged with respect to the container surface 101 and can be moved around the container surface 101 to apply the printed image 109.

[0045] The direct printing device 108 can be configured to print different types of inks, such as white, CMYK colors, varnishes, and spot colors. Preferably, the inks are UV printing inks, although inks of any other type can also be used. The direct printing device can optionally include a curing unit with a light source for emitting UV radiation. Other types of light sources, such as a light source operating in the visible wavelength range, are also conceivable. In particular, the light source can be selected based on the type of ink printed by the direct printing device.

[0046] The direct printing device 108 can further comprise an ink mist extraction system 106, which can be arranged on a side surface of the direct printhead 107. The ink mist extraction system 106 allows the ink mist generated by the direct printing device during the printing process to be extracted from the printing area, thus preventing contamination of the container surface 101, the applied printed image 109, and the direct printing device 108 itself. By arranging the ink mist extraction system 106 on a side surface of the direct printhead 107, efficient extraction of the ink mist generated by the direct printing device 108 can be achieved while simultaneously minimizing any impact on the trajectory of the ink droplets 103 ejected by the print nozzles.

[0047] Since, as described above, the airflow generated by the ink mist extraction system 106 not only extracts the ink mist produced by the direct printing device 108, but also influences the trajectory of the ink droplets 103 ejected from the print nozzle openings of the direct printing device 108, the operation of the ink mist extraction system 106 can lead to an undesirable shift in the point of impact of an ink droplet 103 on the container surface 101. This, in turn, results in a distortion of the printed image 109 applied to the container surface 101 compared to the intended printed image and a deterioration of the print quality.

[0048] To compensate for this effect, the inventive method provides for determining a pixel offset of at least one pixel in a print template based on a model for a print deviation caused by ink mist extraction, and for generating a corrected print template based on the determined pixel offset. Based on the corrected print template, in which the displacement of the print points caused by the ink mist extraction 106 is taken into account, a distortion-free print image 109 can then be applied to the container surface 101.

[0049] As described above, the direct printing device 108 can include a control unit for carrying out the method, wherein the control unit can, for example, comprise a processing unit (processor) and volatile or non-volatile memory. The print image and / or the print template can be stored in the memory of the control unit. Furthermore, the model of the print deviation from a normal value caused by the ink mist extraction system 106 can be stored in the memory of the control unit. In one embodiment, a plurality of models can also be stored in the memory unit, with each of the models being assigned to a specific operating stage of the ink mist extraction system 106.For example, the ink mist extraction system 106 may be designed to operate in several (e.g., five) different operating stages, with different extraction capacities assigned to each stage. Consequently, a pressure deviation model can be stored in the control unit's memory for each of the ink mist extraction system's operating stages 106.

[0050] The control unit can also exchange data with the ink mist extraction system 106, so that the control unit can automatically load a corresponding model of the print deviation from memory based on the operating stage of the ink mist extraction system 106.

[0051] The control unit can be configured, as described above, to determine the pixel offset for at least one pixel of a print template based on the print model and, based on this pixel offset, to generate a corrected print template and to control the direct printing device 108 based on the corrected print template, so that a print image 109 is produced on the container surface 101 in which the displacement of the print points caused by the ink mist extraction 106 is corrected. Thus, a high-quality and, in particular, distortion-free print image 109 can be produced on the container surface 101.

[0052] The related to Figure 1aThe described embodiment of the direct printing device 108 is to be understood as exemplary. In particular, the direct printhead 107 can also comprise any other number of print nozzles 104, and the print nozzles 104 can also be arranged in more than one print nozzle row 105. The design and arrangement of the ink mist extraction system 106 discussed in this context is also to be understood as non-limiting. In an alternative embodiment, the ink mist extraction system 106 can, for example, also be arranged above or below the print nozzle row or at any other position suitable for extracting the ink mist generated by the direct printing device 108.

[0053] The printing model for a pressure deviation from a normal printing value along a print nozzle row caused by the ink mist extraction system 106 is described below in connection with the one described in the Figure 1bThe printed image 110 shown, comprising a first 111 and second printing line 112, is explained in more detail below.

[0054] The one in Figure 1b The first pressure line shown, 111 (normal pressure value line), encompasses a multitude of normal pressure values, which are determined, for example, by the pressure associated with the Figure 1a The print nozzle array 105 of the direct printhead 107 shown may have been applied to the surface 101 of the container 102. The print line 111 represents a print line that was applied to the surface 101 of the container 102 with the ink extraction system deactivated (switched off). As in connection with the Figure 1a As described, the row of pressure nozzles 105 can be aligned parallel to the longitudinal axis 119 of the container. In this case, the one described in the Figure 1bThe first pressure line 111 shown is aligned parallel to the longitudinal axis of the container. In an alternative embodiment, in which the row of pressure nozzles 105 is positioned at any angle relative to the longitudinal axis 119 of the container, the first pressure line 111 can also be arranged at any angle relative to the longitudinal axis 119 of the container 102.

[0055] Also shown is a second pressure line 112 (pressure deviation) with a multitude of pressure deviation values. The second pressure line 112 can also be used in connection with the Figure 1a described print nozzle array of the direct printhead, but with activated ink mist extraction, applied to the container surface 101.

[0056] Between the application of the in the Figure 1bIn the first print line 111 and the second print line 112 shown, no relative movement occurred between the direct print head 107 and the container surface 101, so that a relative displacement Δx 114 between the two print lines is caused solely by the influence of the ink mist extraction 106. The relative displacement Δx 114 depends on the position of the print nozzle, by means of which a print point of the second print line, corresponding to a specific displacement Δx, was applied.

[0057] Also shown is the model of pressure deviation 113, 118 which represents an approximation of the second pressure line 112.

[0058] In one embodiment, the pressure deviation model can be determined by defining the pressure deviation based on a maximum pressure deviation 116 at a position of the nozzle array from the standard pressure value 111, a first pressure deviation 115 from the standard pressure value 111 at a first nozzle located at one end of the nozzle array, and a second pressure deviation 117 from the standard pressure value 111 at a second nozzle located at the other end of the nozzle array. The maximum deviation is understood here to be the maximum displacement Δx 114 of a pressure point 116 of the second pressure line 112 with respect to the corresponding standard pressure value of the first pressure line 111.

[0059] In connection with the in the Figure 1bIn the described embodiment, the maximum deviation occurs at pressure point 116, and thus at the position of the row of pressure nozzles, or the corresponding pressure nozzle, by which pressure point 116 was generated. Furthermore, pressure points 115 and 117 correspond to those caused by the pressure points at the two outermost ends of the pressure points associated with the pressure point 116. Figure 1a The pressure points generated by the pressure nozzles arranged in the row 105 shown are, according to the embodiment described above, referred to as the first 115 and second pressure deviation 117 to determine the pressure deviation model. The three pressure points 115, 116 and 117 are shown only for the sake of clarity. Figure 1b represented as thicker dots.

[0060] In one embodiment, the pressure deviation model can be determined in a first printing range by linear interpolation 113 between the first pressure deviation 115 and the maximum pressure deviation 116, and in a second printing range by linear interpolation between the second pressure deviation 117 and the maximum pressure deviation 116. This allows for a particularly simple determination of the pressure deviation model, as no complicated and computationally intensive methods are necessary. This takes into account the fact that in a printhead, a pixel offset is only possible in integer multiples of the pixel size and / or the distance between nozzles in a nozzle row. This discrete subdivision is sufficiently large to achieve an improvement in the printing result when using linear interpolation.

[0061] Based on the model of the pressure deviation, the control unit can then determine a pixel offset for at least one pixel of the print template and generate a corrected print template based on this pixel offset. Based on the corrected print template, the print image 109 can then be applied to the container surface 101 by the direct printing device 108.

[0062] In one embodiment, the control unit may include a recognition device, such as a camera, and be configured to determine the print model.

[0063] For this purpose, it may be provided that in a first pressure run on a test container, the pressure associated with the Figure 1aThe direct printing device 108 described above applies a first print line 111 with at least one normal pressure value to the container surface 101. In the first printing pass, the ink mist extraction 106 can be deactivated or switched off, so that the first print line 111 corresponds to a reference print line.

[0064] After the first print line 111 has been applied, a second printing pass may involve activating the ink mist extraction system 106 and applying a second print line 112 to the container surface 101, without any relative movement occurring between the container surface 101 and the print nozzle array 105 of the direct printing device 108 between the first and second printing passes. Consequently, the second print line 112 is shifted by a value Δx 114 relative to the second print line 112 solely due to the airflow generated by the ink mist extraction system 106, depending on the printing position.

[0065] In a next step, the control unit can determine the pressure deviation model according to one of the previously discussed embodiments, based on an image of the first and second pressure lines 111, 112 applied to the container surface 101 that was captured by the detection device.

[0066] An embodiment of a further method according to the invention for printing on an irregular container is related to the Figure 2 shown.

[0067] In the embodiment described here, it is provided according to the invention that at least one pixel row with a pixel number n of a print template for a print image based on the shape of a surface area of ​​an irregular container is extended by a pixel number m, and the information contained in the original pixel row is scaled to the extended pixel row. Based on the at least one extended pixel row, a corrected print template is generated, and based on the corrected print template, the print image is applied to the surface area of ​​the irregular container by means of a direct printing device with a plurality of print nozzles.

[0068] An irregular container is defined as a container whose surface deviates from an ideal shape, such as a cylinder. This includes, for example, a container whose surface has at least a partial conical shape, such as a container with a cylindrical base and a conical shoulder. Containers whose surface (considering the overall geometric shape of the container) has at least a partial rounded, angular, conical, or elliptical shape can also be considered irregular. Furthermore, containers with embossing or debossing can also be classified as irregular.

[0069] Regarding possible designs of the direct printing device, reference is made here to those related to the Figure 1adescribed embodiment of the direct printing device 108 is referenced. As also already mentioned in connection with the Figure 1a As described, the direct printing device 108 can include a control unit which is configured to carry out the process steps according to the invention described above.

[0070] In connection with the Figure 2In the discussed embodiment of a pixel row extension 200, a pixel row 201 of a print template is shown, comprising ten pixels. In the embodiment discussed here, the pixel row 201 can be a row of pixels arranged along a horizontal direction of the print template. Alternatively, it can also be a row of pixels arranged vertically in the print template or along any other direction in the print template. Each of the ten pixels represents image information, with each pixel in the embodiment shown here representing either a white pixel 204 or a black pixel 205.

[0071] Based on the shape of a container surface onto which pixel line 201 of the print template is to be printed, the control unit can adjust pixel line 201 by a specific number of pixels in step 203. m ∈ ℕ (in the example shown, m=4). The number of pixels m by which pixel row 201 is extended, and also the pixel positions 206, 207, 208 and 209 at which the additional pixels are inserted into the extended pixel row 202, can be chosen, in particular, based on the shape of the container surface onto which the pixel row is to be applied.

[0072] For example, the surface area of ​​the container to be printed (e.g., an embossed design) can be compared to the surface area of ​​the corresponding ideal shape (e.g., a cylinder). From the ratio of these areas, it can then be determined how many more pixels (m) need to be added to preferably achieve a print resolution on the container surface that is equal to, or only deviates from, the resolution on a container surface with an ideal shape by a maximum of 5% or 10%.

[0073] The shape of the container surface refers to a three-dimensional structure of the container surface, which can be described, for example, by coordinates of a large number of container surface positions.

[0074] By extending the original pixel line 201 to the extended pixel line 202 and creating a corrected print template, distortions caused in particular by an irregular container surface, which would have occurred when applying the print image based on the print template with the original pixel line 201, can be compensated for or prevented.

[0075] In the embodiment shown here, based on a shape of the container surface to be printed, four additional pixels are inserted into the extended pixel row 202 at positions 206, 207, 208 and 209.

[0076] In connection with the Figure 2In the described embodiment, the image information of the added pixels 206, 207, 208, and 209 is determined based on the image information of the two neighboring pixels in the original pixel row 201, between which the additional pixels in the extended pixel row 202 were inserted. In the embodiment shown here, the color value of the inserted pixels 206, 207, 208, and 209 was determined by interpolating the color values ​​of the two neighboring pixels in the original pixel row 201, between which the pixel for the extension was inserted. For example, the two neighboring pixels of the inserted pixel 206 are black, so the interpolated color value of pixel 206 is also black. The neighboring pixels of pixel 207 are, in turn, black and white, so the color value of the interpolated pixel 207 corresponds to a mixture of black and white and thus to a gray color value.The two neighboring pixels of pixel 208 are white, so the interpolated pixel 208 is also displayed as a white pixel. The neighboring pixels of pixel 209, however, are white and black, so interpolating the color values ​​of the two neighboring pixels results in a gray color value for pixel 209.

[0077] This explanation serves only to clarify the invention and does not limit it. In general, a color value (or other parameter) of the pixel 206, 207, 208, 209 to be added can be determined by averaging the corresponding parameters of neighboring pixels in one or two dimensions, wherein the neighboring pixels can include the nearest neighbors of the pixel to be added and / or the next-but-next neighbors of the pixel to be added.

[0078] By extending pixel row 201 by a specific number of pixels 206, 207, 208, 209, and by inserting these pixels at specific pixel positions in the extended pixel row 202 based on the shape of the surface of the container being printed, a corrected print template can be created. When the print nozzles are controlled by the control unit based on the corrected print template, distortions in the printed image caused by the irregular shape of the container, or by the shape of the surface of the irregular container, can be compensated for, thus improving the quality of the printed image applied to an irregular container.

[0079] The related to Figure 2The described embodiment is to be understood as exemplary. The pixel row 201 can also comprise any other number of pixels. Furthermore, the extended pixel row 202 can also be extended by any other number of pixels, whereby the pixels can also be inserted at any other position in the extended pixel row 202. In an alternative embodiment, the pixels of the pixel rows can, for example, also represent colors, and the pixels inserted into the extended print template can represent interpolated color values.

[0080] The related to Figure 2 The described embodiment can be compared with the embodiment of Figure 1 can be combined.

[0081] Another embodiment of a method according to the invention for generating a corrected printing template for printing on a container is related to the Figure 3 depicted.

[0082] According to the invention, it is provided that for at least one pixel of a print template for a print image, a pixel offset is determined based on an offset of a first print nozzle arranged on one side of a direct printhead comprising print nozzles and a second print nozzle arranged on an opposite side of the direct printhead with respect to a print plane, a corrected print template is generated based on the determined pixel offset, and the print image is applied to the container by means of the direct printing device based on the corrected print template.

[0083] This allows for the compensation of printing errors in the printed image applied to the container surface, particularly those caused by tilting or rotating the direct printhead relative to the printing plane.

[0084] Regarding the design of the direct printing device, reference is made to the explanations in connection with the Figure 1a Reference was made to the above. In particular, the direct printing device can also include a control unit which is configured to carry out the process steps according to the invention.

[0085] Figure 3 This shows a printed image 300 applied to a container surface, which can be used, for example, with the print nozzle series 105 of the [product / service] in connection with the [product / service]. Figure 1a The described direct printhead 107 was applied to the surface 101, 301 of a container 102.

[0086] The one in Figure 3The printed image shown comprises a first print line (reference print line) 303, which was applied to the container surface by means of the direct print head 107 in a specific standard orientation. Also shown is a second print line 305, wherein the direct print head 107 is rotated by an angle α relative to the standard orientation when applying this second print line 305. Rotation here refers to a rotation of the print head in a print plane that is perpendicular to the directions along which the ink droplets 103 were dispensed from the print nozzles 104 of the direct print head 107 to generate the print line 303 on the container surface 101, 301.

[0087] The rotation of the printhead when applying the second print line 305 leads to a corresponding rotation of the second print line 305 relative to the first print line 303, and thus to an offset 302 between a print point of the first and the second print line applied by the first print nozzle of the direct printing device. A corresponding offset can also be observed between the print points of the first 303 and the second print line 305 applied by the second print nozzle of the direct printing device.

[0088] In the embodiment discussed here, the first pressure nozzle is located at the first outermost end of the assembly associated with the assembly described in the Figure 1aThe first and second print nozzles are arranged in the print nozzle row 105 shown, and the second print nozzle is arranged on the opposite side of the direct print head 107 at the other outermost end of the print nozzle row 105. This arrangement of the first and second print nozzles is to be understood as exemplary.

[0089] In an alternative embodiment, the first and second print nozzles may also be arranged in two end regions of the print nozzle array 105 on opposite sides of the direct printhead 107, wherein an end region may comprise a specific number of print nozzles, such as the three outermost or the five outermost print nozzles of the print nozzle array. If the direct printhead 107 comprises, for example, several print nozzle arrays 105, the first print nozzle may also be arranged, for example, in a first print nozzle array and the second print nozzle in a second print nozzle array, wherein the two print nozzle arrays may be arranged on opposite sides of the direct printhead.

[0090] Based on the specified offset 302, 304, the control unit can, for example, determine a pixel offset for at least one pixel of the print template and generate a corrected print template based on this determined pixel offset. Based on the corrected print template, the control unit can then actuate the print nozzles 104 of the direct printing device 108 in such a way that the pixel offset generated by the rotation of the direct print head is compensated and an aligned print image is applied to the container surface 101.

[0091] In one embodiment, the pixel offset can be based on a number N D of the print nozzles of the direct printhead, an offset V of the print pixel at the top and bottom positions of the print line in units of pixels and the position of the pixel to be corrected PThis allows for a precise determination of the pixel offset and thus an accurate correction of the misalignment of the printed image on the container surface 101, 301 caused by a rotation of the direct printhead 107.

[0092] The pixel offset for at least one pixel of the print template can then preferably be based on the context Δ P = P Korr N D V ∗ 2 − V , will be calculated.

[0093] Based on the pixel offset determined in this way, at least one pixel position of the print template can then be determined. P a corrected pixel position P' = P + Δ P The values ​​are calculated and a corrected print template is generated based on this calculation.

[0094] If a printed image is now applied to the container surface using the printing device based on the corrected print template, the error in the printed image caused by the twisting can be compensated for and the quality of the generated printed image can be further improved.

[0095] The related to Figure 3 The described embodiment can be used with all those related to the Figures 2 and 3 The described embodiments can be combined.

[0096] Furthermore, it can be used for each of the items related to the Figure 1 , 2 and 3In the discussed embodiments, it is provided that the print template is divided into individual color layers before the pixel offset is determined, and the methods according to the previously discussed embodiments or their combination are applied to each of the color layers, so that a corrected print template (also referred to as a color layer print template) is generated for each of the color layers. To apply a colored print image, for example, several of the methods associated with the Figure 1a The direct printing devices shown are arranged one behind the other along the circumference of the container, and each of the printing devices applies a color print image to the surface of the container based on one of the corrected color layer print templates.

Claims

1. Direct printing method for printing a container (102) with a print image (109) by means of a direct printing device (108) comprising a direct printing head (107) with at least one row of print nozzles (105) and an ink mist extraction system (106), wherein a pixel offset is determined for at least one pixel of a print template for the print image based on a model for a print deviation (113, 118) from a normal print value (111) caused by the ink mist extraction system (106) along the row of print nozzles (105), wherein a corrected print template is generated based on the determined pixel offset, wherein the print image (109) is applied to the container (102) by means of the direct printing device (108) based on the corrected print template.

2. Direct printing method according to claim 1, wherein the model of the pressure deviation (113, 118) is determined based on a maximum pressure deviation (116) at a position of a print nozzle row from the normal pressure value, a first pressure deviation (115) from the normal pressure value at a first print nozzle arranged at one end of the print nozzle row and a second pressure deviation (117) from the normal pressure value at a second print nozzle arranged at the other end of the print nozzle row.

3. Direct printing method according to claim 2, wherein, in the event that the maximum printing deviation (116) is located at a position between the first printing nozzle and the second printing nozzle, the printing deviation along the printing nozzle row is determined in a first region of the printing nozzle row by linear interpolation (112) between the first printing deviation (115) and the maximum printing deviation (116) and in a second region of the printing nozzle row by linear interpolation (118) between the second printing deviation (117) and the maximum printing deviation (116).

4. Direct printing method according to one of claims 1 to 3, wherein the pixel offset is determined based on the model of the printing deviation (113, 118) for at least one pixel row of the printing template.

5. Direct printing device for printing a container, comprising a direct printing head (107) with a plurality of printing nozzles (104), wherein the printing nozzles (104) are arranged in at least one printing nozzle row (105), an ink mist extraction system (106) and a control unit, wherein the control unit is designed to carry out the method according to one of claims 1 to 5.

6. Direct printing device according to claim 5, wherein the ink mist suction (106) is arranged on a side surface of the direct printing head (107).

7. Direct printing method for printing on an irregular container, wherein at least one pixel line (201) with a pixel number n of a print template for a print image is expanded by a pixel number m based on a shape of a surface area of ​​the irregular container, wherein the information contained in the original pixel line (201) is scaled to the expanded pixel line (202), wherein a corrected print template is generated based on the at least one expanded pixel line (202), wherein, based on the corrected print template, the print image (109) is applied to the surface area of ​​the irregular container by means of a direct printing device (108) having a plurality of print nozzles (104).

8. Direct printing method according to claim 7, wherein scaling the information contained in the original pixel line (201) to the extended pixel line (202) comprises an interpolation between two adjacent pixels of the original pixel line (201).

9. Direct printing device (108) for printing an irregular container, comprising a direct printing head (107) with a plurality of printing nozzles (104), wherein the printing nozzles are arranged in at least one printing nozzle row (105), and a control unit, wherein the control unit is designed to carry out the method according to claim 7 or 8.

10. Direct printing method for printing on a container, wherein a pixel offset is determined for at least one pixel of a print template for a print image (109) based on an offset (302, 304) of a first print nozzle arranged on one side of a direct print head (107) comprising print nozzles (104) and a second print nozzle arranged on an opposite side of the direct print head (107) with respect to a printing plane, wherein a corrected print template is generated based on the determined pixel offset, wherein the print image (109) is applied to the container by means of the direct printing device (108) based on the corrected print template.

11. Direct printing method according to claim 10, wherein the print nozzles (104) of the direct print head (107) are arranged in at least one print nozzle row (105) and the pixel offset is determined based on an offset (302, 304) of a first print nozzle arranged at one end of a print nozzle row (105) and a second print nozzle arranged at the other end of the print nozzle row (105) with respect to the printing plane and / or wherein the pixel offset is determined based on an offset between a first print nozzle of a first print nozzle row arranged at one end of the direct print head (107) and a second print nozzle of a second print nozzle row arranged at the other end of the direct print head with respect to the printing plane.

12. The direct printing method according to claim 10 or 11, wherein the pixel offset is determined based on the maximum number of print nozzles (104) of the direct print head (107) and the position of the pixel.

13. Direct printing device (108) for printing a container, comprising a direct printing head (107) with a plurality of printing nozzles (104), wherein the printing nozzles (104) are arranged in at least one printing nozzle row (105), and a control unit, wherein the control unit is designed to carry out the method according to one of claims 11 to 14.

14. Direct printing method according to one of claims 1-4, 7-8 or 10-12, wherein the printing template is divided into different color layers and a corrected printing template is created for each color layer.

Images