Method for printing paper and digital printing device

Abstract

The invention relates to a method for printing non-paper objects (16) by means of a digital printing device having a plurality of paint application tools (6) for applying printing inks of different colors, in which method a paint carrier element (8, 28) passes through the paint application tools (6) in a feed direction (10, 26), wherein the digital printing apparatus has a device (2, 26) configured and adapted to prevent or reduce the formation of condensation on the paint application tool (6), and by means of the device (2, 26), the formation of condensation on the paint application tool (6) is prevented or reduced, and wherein the device (2, 26) has a temperature controller and an electrical controller, wherein the temperature controller is arranged to influence the temperature of the paint application tool (6) and the electrical controller is arranged to control the temperature controller such that the paint application tool (6) has different temperatures wherein the temperature of the paint application tool (6) increases in a feed direction (10, 26), the temperatures of two adjacent coating application tools (6) differ from each other by at least 0.5 DEG C, at most 1.5 DEG C, and wherein the temperature between the first coating application tool (6) in the feed direction (10, 26) and the last coating application tool (6) in the feed direction (10, 26) differs by at most 10 DEG C.

Description

Technical Field

[0001] The invention relates to a method for printing a non-paper object by means of a digital printing device, the digital printing device having a plurality of coating application tools for applying printing inks of different colors to paper, wherein in the method, a coating carrier element passes the coating application tools in a feed direction, wherein the device has a temperature controller and an electrical controller, wherein the temperature controller is arranged to influence the temperature of the coating application tools, and the electrical controller is arranged to control the temperature controller so that the coating application tools have different temperatures. The invention also relates to a digital printing device, which is arranged and suitable for printing paper with the method. Background Art

[0002] Printing on non-paper objects has been known from the prior art for many years. In the production of laminates, for example for the production of floor panels or wall and ceiling coverings, as well as furniture panels, the top part that is visible in later use is provided with a decoration. This can be printed on a decorative paper, which then has to be connected to a core, i.e. the actual panel, such as a wood-based panel, alternatively, an object, such as a laminate or a part thereof, such as a core of a laminate, can be printed with ink. In the prior art, it is known to apply printing ink directly to an object, for example using roller printing. Direct printing on wood-based panels, in particular in this field of application, has proven to be difficult and in many cases incompatible with the high demands on print quality and reproducibility. In the case of direct printing, the coating carrier is the object.

[0003] Therefore, in this case, indirect printing is often used. In this case, the coating carrier element to which the printing ink is applied is, for example, a printing cylinder, from which the printing ink applied to the printing cylinder via a coating application tool is applied to an application roller, which prints the actual object to be printed. Alternatively, a printing belt can also be used. The printing belt is tensioned and started by at least two rollers, for example a printing roller (which can also be called a printing cylinder, and a transfer roller, which can also be called an application roller). The coating application tool prints the ink onto the printing belt, which in this case forms the coating carrier element. From there it is transferred to the actual object to be printed.

[0004] Digital printing devices for printing paint carrier elements have also long been known. So-called single-pass digital printing devices are used, for example, in the packaging industry to print packaging materials such as cartons, wherein the ink carrier element to be printed only passes through the printing device once. In this case, however, the requirements placed on the printing and quality of the decoration produced thereby are significantly lower than, for example, in the case of production of decorations for the above-mentioned purposes. This applies both to the quality of the individual printings of the decoration and to the reproducibility of the decoration, which is usually required for large-scale production. In addition, items with the same decoration are usually produced in batches at relatively large time intervals, which places higher demands on reproducibility.

[0005] It is known from the prior art that various parameters influence the quality of the decoration produced. This relates, for example, to the paint carrier element used and the object to be printed, the amount and type of printing ink applied, the amount and type of any primer (also called inner lacquer) used, as well as environmental influences such as humidity and temperature. These parameters cannot usually be optimized independently of one another, but influence each other, not only on the paint carrier element to be printed and possibly on the object to be printed, but also on the digital printing device used for printing. For example, it is known that condensation may form on the print head. This can influence the quality of the printing result. Condensation on the print head can be incorporated into and clog individual nozzles on the print head from which ink is discharged. This can lead to malfunctions of the entire print head. In order to prevent this, more intensive cleaning is required to remove the condensation that forms. In addition, such cleaning leads to the need and consumption of cleaning fluids for cleaning, thus increasing production costs. Printing ink is also consumed during the cleaning process, which can also have a negative effect.

[0006] If condensation is not detected and removed promptly, it may result in scrapped products, which can increase production costs and the cost of necessary materials, leading to longer downtime of printing equipment and increased maintenance and repair costs. Summary of the invention

[0007] Therefore, the object of the present invention is to propose a method for better achieving safe and continuous production.

[0008] The object is achieved by a method of printing a non-paper object by a digital printing device according to the present invention, wherein the digital printing device has a plurality of coating application tools for applying printing inks of different colors to paper, wherein in the method, a coating carrier element passes through the coating application tool along a feed direction, wherein the device has a temperature controller and an electrical controller, wherein the temperature controller is configured to influence the temperature of the coating application tool, and the electrical controller is configured to control the temperature controller so that the coating application tool has a different temperature, wherein the digital printing device has a device, which is configured and suitable for preventing or reducing the formation of condensation on the coating application tool, and the formation of condensation on the coating application tool is prevented or reduced by the device, and the method is unique in that the temperature of the coating application tool increases in the feed direction, and the temperature difference between two adjacent coating application tools is at least 0.5°C and at most 1.5°C, wherein the temperature difference between the first coating application tool in the feed direction and the last coating application tool in the feed direction is at most 10°C.

[0009] Thus, the coating carrier element to be printed passes through various coating application tools in a digital printing device. The printing ink applied by the respective coating application tools is applied to the coating carrier element. After the coating carrier element has passed through all the existing coating application tools, the coating carrier element is thus printed with the desired decoration. In indirect printing, this decoration is subsequently transferred to the object to be printed, wherein the coating carrier element is rolled onto the object. In direct printing, the coating carrier element is the object.

[0010] Instead of having to remove the condensation produced in the prior art and / or maintain, clean or repair the printing device, the invention solves the problem by reducing or completely preventing the formation of condensation. According to the invention, a device is provided for this purpose, which is preferably part of a digital printing device and is configured and suitable for preventing or reducing the formation of condensation. In the method of the invention, it also takes on this task. This means in particular that less condensation is produced in a digital printing device with the device than in a digital printing device without the device. This is especially true if the same parameters are used.

[0011] According to the invention, the device has a temperature controller and an electrical controller. The temperature controller is arranged to influence the temperature of the paint application tool. This can occur in different directions. The temperature controller preferably comprises a heater, which is configured to increase the temperature of the paint application tool. Particularly preferably, the heater is arranged to increase the temperature of the paint application tool independently of each other. Alternatively or additionally, the temperature controller preferably has a cooling device, which is arranged to reduce the temperature of the paint application tool. Particularly preferably, the cooling device is arranged to reduce the temperature of the paint application tool independently of each other.

[0012] The electrical controller is arranged to control the temperature controller. In a preferred embodiment, the digital printing device has at least one temperature sensor. Particularly preferably, the digital printing device has at least one temperature sensor for each paint application tool. The temperature sensor is arranged to transmit measurement data to the electrical controller, the measurement data containing information about the temperature of the corresponding paint application tool. Thus, the temperature can be measured. The electrical controller is preferably arranged to access an electronic data storage device in which a target temperature value of the corresponding paint application tool is stored. The electrical controller is or preferably includes an electronic data processing device. The electrical controller compares the temperature of the paint application tool measured by the sensor with the target temperature stored in the electronic data storage device, and is arranged to control the temperature controller based on the comparison result. If the measured temperature deviates from the target temperature by more than a predetermined value, the electrical controller sends a control signal to the temperature controller, and then the temperature controller changes the temperature of the paint application tool. If the measured temperature is greater than the stored target temperature, the cooler of the temperature controller is controlled by the control signal and reduces the temperature. If the measured temperature is lower than the stored target temperature, the heater of the temperature controller is controlled by the control signal.

[0013] According to the invention, the electrical controller is arranged to control the temperature controller so that the coating application tool has different temperatures. Particularly preferably, the temperature of the coating application tool increases in the feed direction. This design is based on the recognition that the amount of liquid printing ink applied to the coating carrier element increases in the feed direction. This also increases the risk of condensation of the applied liquid amount. The higher the temperature of the coating application tool, the lower the probability that liquid located in the vicinity of the coating application tool will condense on the coating application tool. Therefore, it is generally advantageous if the temperature of the coating application tool increases in the feed direction.

[0014] The temperatures of two adjacent coating application tools differ by at least 0.5° C., preferably at least 0.7° C., particularly preferably at least 1.0° C. The temperatures of two adjacent coating application tools differ by at most 1.5° C., preferably at most 1.3° C., particularly preferably at most 1.0° C.

[0015] In a specific embodiment, for example, the digital printing system has four coating application tools, whose temperatures increase in the feeding direction. In this specific embodiment, the temperature of the first coating application tool is 29°C, the temperature of the second coating application tool is 30°C, the temperature of the third printing tool is 31°C, and the temperature of the fourth printing tool is 32°C.

[0016] On the one hand, it is advantageous if the temperature between the coating carrier element to be printed and the print head is as low as possible in order to reduce the risk of condensation formation. Since the coating carrier element is also heated when passing through the digital printing device, it is advantageous if the temperature of the coating application tool also increases in the feed direction. On the other hand, the amount of printing ink applied by the respective coating application tool increases with the temperature of the coating application tool. It is therefore advantageous to limit the overall temperature difference between the first and the last coating application tool. The temperature difference between the first coating application tool in the feed direction and the last coating application tool in the feed direction is at most 10° C., preferably at most 7° C., particularly preferably at most 5° C.

[0017] Preferably, the digital printing device has a cooling device, which is configured to cool the paint carrier element. This is particularly advantageous if an indirect printing method is used. In this case, as previously described, the printing ink is transferred from the paint application tool to the paint carrier element and from the paint carrier element directly or indirectly to the object. Therefore, the paint carrier element rotates within the digital printing device and passes the paint application tool several times. However, it is a single-pass system, because all the paint for printing is applied to the paint carrier element in a single pass. The paint carrier element heats up slightly during each cycle, so that the temperature of the paint carrier element increases during the operation of the digital printing device. In order to reduce the associated risks of condensation formation, a cooling device is provided. Preferably, the device has an additional temperature sensor, which is configured to determine the temperature of the paint carrier element. The measured value determined by the additional sensor is transmitted to an electrical controller, preferably an electronic data processing device, in which the measured value is preferably compared with a stored target value. According to the comparison result, the electrical controller controls the cooling device.

[0018] In a preferred embodiment, the device has at least one air flow deflector, which is arranged between two paint application tools and is configured and suitable for deflecting the air flow from the paint application tool to the adjacent paint application tool. Therefore, in the absence of an air flow deflector, the air flow flows from one paint application tool to the adjacent paint application tool and is subsequently deflected by the air flow deflector. The air flow deflector can be designed in the form of a wall or a plate, for example, which is placed or positioned in the path of the actual air flow. This is particularly advantageous in order to prevent the printing ink spray generated when the printing ink is ejected from the paint application tool from being guided or blown by an air flow from one paint application tool to an adjacent paint application tool, the air flow may, for example, come from a moving part of a digital printing device, from a paint carrier element moved by the digital printing device and / or from an air flow in the environment (Halle) in which the method is performed. This also reduces the amount of liquid in the adjacent paint application tool position, which also reduces the risk of condensation.

[0019] Particularly preferably, the device has at least one air flow deflector between each two adjacent paint application tools. This means that whenever two paint application tools are arranged adjacent to each other, at least one air flow deflector is located between the two paint application tools.

[0020] Preferably, the device has at least one air extractor, which is arranged between two adjacent paint application tools and is suitable and configured to suck the air between the two paint application tools. Particularly preferably, the device comprises at least one air extractor between each two adjacent paint application tools. This means that whenever two paint application units are arranged adjacent to each other, at least one air extraction device is located between the two paint application tools. The air extractor sucks the ink spray generated when the printing ink is ejected from the paint application tools. The air extractor is preferably part of a cooler of a temperature controller.

[0021] Advantageously, the device has a housing surrounding the coating application tool. Thus, moisture, spray and other factors that accelerate or contribute to the formation of condensation can be kept away from the print head of the coating application tool.

[0022] In a preferred embodiment, the digital printing device has a monitoring unit configured to detect condensation formation of at least one coating application tool.

[0023] The invention also achieves the stated object by a digital printing device of the type described herein, which is arranged and adapted to print non-paper objects using the method described herein.

[0024] In a particular embodiment, the digital printing device comprises at least one four-color set, preferably a five-color set for printing. The ink sequence is optimized for decoration printing (for example for a color set containing five colors: blue-red-yellow-red-green-yellow-black). The created waveform, i.e. the drop shape produced at the coating application tool, allows an adjustable temperature tolerance of the print head of at least 3°C, preferably 6°C, particularly preferably 10°C, without requiring the recognition of significant color deviations in the decoration.

[0025] Digital printing equipment is calibrated and profiled according to its chemical and physical properties and the object to be printed. Here, it is necessary to determine the maximum amount of ink applied and limit the ink consumption to the required level.

[0026] The printing data is generated from a determined printing profile, and the version X generated thereby is rasterized in the printing press. The amount of paint applied is determined by the printing software based on the rasterized data.

[0027] First, the top surface to be printed of the panel to be printed (e.g. ROH HDF panel, 2070 x 2800 mm) is sanded. Next, a melamine resin primer is applied and dried at 210°C, preferably 200°C. Thereafter, multiple layers of white (e.g. a solution of water and titanium dioxide) are applied. Drying is carried out inline after each application of the coating, and the dryer temperature is gradually reduced by 190°C from the first application to the last application. In the next step, a primer (e.g. a reactive primer) is applied to the top surface of the panel to be printed and dried. Producing 22 g / m 2 , preferably 20g / m 2 The coated, ready-to-print panel is cooled in a cooling cycle machine from 57° C. to 38° C., preferably to 36° C., before the digital printing of the panel.

[0028] The optimized panels are printed online at a system speed of 80 m / min, preferably 85 m / min. For this purpose, an aqueous ink system is used. From a constructional point of view, the separation of the printing unit from the printed material (i.e. the panel to be printed) is accomplished by one or more application rollers or drive belts. Indirect application is a temperature buffer that is adapted to the production requirements by cooling and heating with air conditioning.

[0029] The housing is installed near the coating application tool to limit environmental influences. The theoretical ink volume determined by the printed decoration on the panel digital printer is used to control the temperature grading of the individual printing tools. The coating tools increase by 1°C from tool 1 to tool 4 or tool 5 respectively. Particularly preferred: 29°C for the first coating tool; 30°C for the second coating tool; 31°C for the third coating tool; 32°C for the fourth coating tool and 33°C for the fifth coating tool.

[0030] Automatic monitoring of condensation is achieved by laser detection. If the laser detects condensation at an early stage, the application of coating (Einschub) is automatically stopped. Appropriate time intervals are inserted in the ongoing production process for cleaning the head. Preferably, the plate buffer is filled in a preceding cooling cycler. After cleaning, the panels are fed back into the printing process. The intervals can thus be determined in a decoration-specific manner based on the recorded data related to the production volume. Particularly preferably, the cleaning takes place at the best possible point in time, for example when changing the decoration or when another required production interruption (e.g. changing the sanding belt) is required.

[0031] Air flow deflectors with suction function remove moisture-saturated air from the machine's print head area during production without affecting the ink flow. The printed panels are coated with melamine resin and dried again and cooled to 30°C in a cooling tower. They are then sent to the crane warehouse for aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Some embodiments of the present invention are explained in more detail below with the aid of the accompanying drawings. In the drawings:

[0033] Figures 1 to 3 Schematic diagrams showing different embodiments of a digital printing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] Figure 1 A digital printing device is shown, which has a printing unit 2 surrounded by a housing 4. The printing unit has four coating application tools 6, each of which can apply a color of printing ink. A fifth coating application tool 6 is shown with a dotted line. This indicates that the additional coating application tool 6 is optional. The coating application tool 6 applies the printing ink to a printing cylinder 8, which forms a coating carrier element in this embodiment. The printing cylinder rotates in the direction of arrow 10 so that the printing cylinder 8 passes the coating application tool 6. Therefore, in the illustrated embodiment, the direction of movement indicated by the arrow 10 forms the feed direction of the coating carrier element. The printing cylinder 8 is in contact with an application roller 12 rotating in the direction of arrow 14. By bringing the application roller 12 into contact with the printing cylinder 8, the printing ink applied by the coating application tool 6 is transferred from the printing cylinder 8 to the application roller 12.

[0035] The application roller 12 rolls on the object to be printed 16. It moves in a transport direction 18. For this purpose, a transfer unit 20 is provided. After the surface of the application roller 12 has rolled up on the object to be printed 16, it comes into contact with a washing unit 22, the rollers of which remove residues from the surface of the application roller 12. The washing unit 22 has a drying unit 24, which dries the rollers of the washing unit 22 and thus prepares them for further absorption of printing ink remaining on the application roller 12.

[0036] In the housing 4 of the printing unit 2, between each two adjacent coating application tools, a device 26 is arranged, which is configured to reduce or completely prevent the formation of condensation at the coating application tools 6. In the embodiment shown, the device 26 is an air aspirator and air flow deflector, which are only schematically shown. The housing 4 also ensures that the formation of condensation at the coating application tools 6 is low and is therefore also part of the device 26.

[0037] Figure 2 Another embodiment of a digital printing device is shown. This digital printing device also has coating application tools 6, wherein a fifth coating application tool is shown in dashed lines and is therefore marked as optional. Between each two adjacent coating application tools 6 there is again a device 26 for reducing condensation formation. However, in contrast to Figure 1 In contrast, the coating material carrier element is not a printing cylinder 8, but a printing belt 28 that circulates in the direction of arrow 30. Therefore, in the embodiment shown, the direction of arrow 30 forms the feed direction of the coating material carrier element. The printing belt 28 runs around the printing cylinder 8 and the conveyor roller 32, and the printing belt 28 in the embodiment shown is also moved by the printing cylinder 8 and the conveyor roller 32. Other arrangements and details correspond to Figure 1 The embodiments in .

[0038] Figure 3 Another embodiment of a digital printing device according to an embodiment of the present invention is shown. Figure 2 The embodiment shown is different. Figure 3 The middle printing belt 28 not only runs around the printing cylinder 8 and the transfer roller 32, but also around the upper cleaning aid 34. This is part of the washing unit 22, which has two cleaning blades 36 in the embodiment shown. This embodiment also has a cleaning device such as Figure 1 and Figure 2 Device 26 of an embodiment of the present invention.

[0039] Reference numerals list

[0040] 2 printing units

[0041] 4 Shell

[0042] 6Paint application tools

[0043] 8 Printing Cylinders

[0044] 10 Arrows

[0045] 12 Shi Jiakun

[0046] 14 Arrows

[0047] 16 Objects

[0048] 18 Transportation Directions

[0049] 20Transmission units

[0050] 22 washing units

[0051] 24 drying units

[0052] 26 devices

[0053] 28 Printing tape

[0054] 30 arrows

[0055] 32 Transmission

[0056] 34 Cleaning roller

[0057] 36. Clean the scraper.

Claims

1. A method for printing a non-paper object (16) by means of a digital printing device, the digital printing device having a plurality of coating application tools (6) for applying printing inks of different colors, wherein in the method, a coating carrier element (8, 28) passes the coating application tool (6) in a feed direction (10, 26), wherein the digital printing device has a device (2, 26) configured and suitable for preventing or reducing the formation of condensation on the coating application tool (6), and the formation of condensation on the coating application tool (6) is prevented or reduced by the device (2, 26), wherein the device (2, 26) has a temperature controller and an electrical controller, wherein the temperature controller is arranged to influence the temperature of the coating application tool (6), and the electrical controller is arranged to control the temperature controller so that the coating application tool (6) has different temperatures, characterized in that The temperature of the coating application tool (6) increases in the feed direction (10, 26), and the temperatures of two adjacent coating application tools (6) differ from each other by at least 0.5°C and at most 1.5°C, wherein the temperature difference between the first coating application tool (6) in the feed direction (10, 26) and the last coating application tool (6) in the feed direction (10, 26) is at most 10°C.

2. The method according to claim 1, characterized in that The temperatures of two adjacent coating application tools ( 6 ) differ by at least 0.7° C., particularly preferably by at least 1.0° C., and by at most 1.3° C., particularly preferably by at most 1.0° C.

3. The method according to claim 1 or 2, characterized in that: The temperature of the first coating application tool (6) in the feed direction (10, 26) and the last coating application tool (6) in the feed direction (10, 26) differs by at most 7°C, in particular at most 5°C.

4. The method according to any one of the preceding claims, characterized in that The device (2, 26) has at least one air flow deflector, which is arranged between two paint application tools (6) and is designed and suitable for deflecting the air flow from the paint application tool (6) to the adjacent paint application tool (6).

5. The method according to claim 4, characterized in that The device (26) has at least one air flow deflector between every two adjacent paint application tools (6).

6. The method according to any one of the preceding claims, characterized in that The device (26) has at least one air extractor, which is arranged between two paint application tools (6) and is designed and suitable for sucking air between the two paint application tools (6).

7. The method according to claim 6, characterized in that The device (26) has at least one air extractor between every two adjacent paint application tools (6).

8. The method according to any one of the preceding claims, characterized in that The device (2) has a housing (2) surrounding the paint application tool (6).

9. The method according to any one of the preceding claims, characterized in that The digital printing device has a monitoring unit which is arranged to detect the formation of condensation on at least one coating application tool (6).

10. The method according to any one of the preceding claims, characterized in that The coating material carrier element (8, 28) is the object (16) to be printed.

11. The method according to any one of claims 1 to 9, characterized in that The coating material carrier element (8, 28) is a transport element, for example a transport roller (8) or a transport belt (28).

12. A digital printing device adapted and arranged to print a non-paper object (16) by means of a method according to any one of the preceding claims.

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