JP5156431B2 - Inkjet painting method - Google Patents

Description

  The present invention relates to an industrial inkjet coating apparatus that performs inkjet coating with a stationary coating head while conveying an object to be coated.

  Conventionally, in the above-described coating apparatus, when a spray nozzle for spraying paint or paint breakage occurs, a line omission defect or a color defect in which a correct color cannot be reproduced occurs on the painted surface. As an example of the prior art that attempts to solve this problem, the following patent documents 1 to 3 are outlined.

  That is, Patent Document 1 includes a line-type fixed inkjet head and a repair head, and in advance, whether or not there is a non-ejection nozzle by an imaging unit by ejecting ink from these heads onto an ink droplet landing position evaluation jig. A configuration is disclosed in which a defective nozzle of a fixed inkjet head is corrected with a normal nozzle of a repair head based on the detection result. In this configuration, even when a non-ejection nozzle or a beam bending nozzle is generated in the fixed inkjet head, it is possible to form a film without defects such as white stripes and uneven thickness.

  Further, in Patent Document 2, a test pattern for each color is printed on a test print area on a recording paper by each print head, and this test pattern is read by a sensor provided immediately after each print head. A configuration for detecting an ejection failure nozzle is disclosed. With this configuration, it is possible to detect a defective ejection nozzle immediately after printing, and it is possible to relieve an image at an early stage.

In Patent Document 3, the feeding mechanism for moving the medium, the first nozzle for ejecting droplets to the medium fed by the feeding mechanism, and the ejection of droplets by the first nozzle are defective. A configuration has been disclosed that includes a detection unit that detects a discharge failure location that is a location on a medium and a second nozzle that discharges a droplet to the discharge failure location when the detection unit detects the discharge failure location. The first nozzle and the second nozzle are provided on the same ejection head. In this configuration, it is possible to form a desired recording film or wiring by performing correction discharge toward the defective discharge location using the correction nozzle based on the result detected by the detection unit.
JP 2005-185978 JP JP 2005-096447 JP 2004-358353 A

  However, in Patent Document 1 described above, even if there is a defective nozzle in the fixed inkjet head, the object to be coated can be painted without causing defective line omission by correcting with the nozzle of the repair head. It is necessary to grasp in advance the defective nozzle. Therefore, even if this technique is adopted in an industrial coating apparatus, it is difficult to repair a defective portion without interrupting the painting process when nozzle clogging or paint breakage occurs during painting.

  Moreover, the said patent document 2 does not teach the technique of repairing the printing surface by the detected ejection failure nozzle. Therefore, even if the technique of Patent Document 2 is employed in an industrial coating apparatus, it is not possible to repair line omissions that occur during painting of an object to be coated.

  In the said patent document 3, since the 1st nozzle and the 2nd nozzle were provided on the same discharge head, it employ | adopted for the coating apparatus of the structure which coats while conveying a to-be-coated article to one direction. In this case, there is a problem that the structure becomes complicated because the ejection head itself must be movable in order to move the second nozzle to the ejection failure location. Further, since the ejection head moves when repairing a defective ejection location, the ejection head cannot be maintained while painting.

  The present invention has been proposed in view of such circumstances, and repairs a defective portion without interrupting the painting process even when nozzle clogging or paint breakage occurs during painting in an industrial coating apparatus. It is intended to allow the operator to maintain the painting head while painting.

  In order to achieve the above object, the present invention is a method of inkjet coating while moving an object to be coated relative to a coating head, which is distributed in advance between a first coating head and a second coating head. A step of simultaneously operating the first and second coating heads in accordance with the coating data and coating the object to be coated; and a step of photographing a painted surface immediately after being painted by the first coating head by a photographing means And the image of the painted surface photographed by the photographing means and the coating data previously assigned to the first painting head, and if there is a defective portion on the painted surface, the defective portion is repaired. For generating the repair data, and a step of further operating the second coating head in accordance with the repair data to paint the defective portion.

  The photographing unit is preferably downstream of the first painting head in the moving direction of the object to be coated. However, the photographing unit is configured integrally with the first painting head. Also good. In addition, it is desirable that the second coating head is on the downstream side in the moving direction of the object to be coated with respect to the photographing means.

  The second coating head may reduce the moving speed of the object to be coated when the defective portion is repaired by the second coating head.

  In the present invention, the first painting head and the second painting head are simultaneously operated to coat the object to be coated, so that the painting process is speeded up. In addition, when the painted surface immediately after being painted by the first painting head is photographed, if there is a defective portion on the painted surface, repair data is generated, and the second painting head is operated according to the repair data. Since the defective portion is repaired, the coating failure does not occur even when the nozzle is clogged or the paint is cut off in the first coating head while the object is being painted. It is also possible to maintain the first painting head while painting.

  In addition, when the photographing unit and the first painting head are integrated, the positional relationship between the first painting head and the photographing unit becomes precise, so that accurate repair data can be generated. For this reason, the repair of the painted surface by the second painting head is finished more beautifully.

  When the defective portion is repaired by the second coating head, in the configuration in which the moving speed of the object to be coated is reduced, the time for repairing the defective portion can be secured by decreasing the moving speed of the object to be coated. Therefore, it is not necessary to operate the second coating head at a high speed, and the control becomes simple.

  Embodiments of the present invention will be described below with reference to the drawings. INDUSTRIAL APPLICABILITY The present invention can be suitably applied to an industrial coating apparatus configured to perform inkjet coating with a stationary coating head while conveying an object to be coated, but a coating apparatus configured to move the coating head with respect to a stationary object It can also be applied to. That is, it is only necessary that the article 20 and the painting head are relatively movable. Further, the present invention is not limited to an industrial coating apparatus, but can be applied to general household inkjet printers that form images on recording paper.

  FIG. 1 is a schematic diagram showing the basic principle of an inkjet coating apparatus for carrying out the method of the present invention.

  The coating apparatus 1 includes, for example, a transport unit 11 that transports an object 20 such as a plate material according to a predetermined trajectory, and first and second coating heads 12 and 13 that perform coating by spraying droplets of paint or the like. The photographing means 14 for photographing the painted surface coated by the painting head 12 and the control means 17 for controlling the painting heads 12 and 13 are provided. The control means 17 is connected to detection means 16 for detecting the passage of the object 20 to be coated. Note that the coating heads 12 and 13 and the photographing unit 14 are supported by the supporting unit 15 provided so as to cross the upper part of the conveying unit 11 so as to drop downward above the conveying unit 11.

  The conveying means 11 is constituted by a belt conveyor, for example, and is driven at a constant speed by an electric motor (not shown).

  The coating head 12 is of a line type that is wider than the width of the coating to be applied to the workpiece 20. On the lower surface side of the coating head 12, a plurality of spray nozzles for spraying the paint by an ink jet method are arranged in the longitudinal direction, and are transported by the transport means 11 toward the object 20 to be coated passing under the coating head 12. The paint surface can be formed by spraying the paint. The ejection nozzles 12a to 12d are, for example, nozzles corresponding to colors Y, M, C, and K, respectively, but actually, a very large number of nozzles are provided instead of only four. The coating head 12 may be compatible with either single color coating or full color coating. The coating head 13 also has similar injection nozzles 13a to 13d.

  The imaging means 14 is composed of a line-type optical unit in which a plurality of imaging elements respectively corresponding to the spray nozzles 12 a to 12 d of the coating head 12 are arranged in the longitudinal direction, and is a predetermined distance from the coating head 12. It is on the downstream side of the moving direction of the article 20 with a gap. By arranging in this way, it becomes possible to sequentially photograph the painted surface immediately after being painted by the painting head 12.

  The control means 17 holds coating data obtained by converting a coating pattern to be applied to the object 20 to be coated, and allocates the coating data to the coating heads 12 and 13 in advance. Then, the passage timing of the object to be coated 20 is acquired by the detection means 16, and the coating heads 12 and 13 are simultaneously operated according to the coating data distributed in advance to the first coating head and the second coating head. Then, the object 20 that is passing under the coating heads 12 and 13 is painted. Here, if the coating heads 12 and 13 share portions that do not overlap each other, for example, odd lines and even lines, the odd lines and even lines are coated at the same time. The conveyance speed of the article 20 can be increased.

  In parallel with this, the painted surface immediately after being painted by the painting head 12 is sequentially photographed by the photographing means 14, and the image of the photographed painted surface is compared with the data for painting. If there is a part, repair data for repairing the defective part is generated, and further, a repair process for repairing the defective part is performed by operating the coating head 13 according to the repair data. In this case, the coating head 13 needs to operate on both the even lines that should be painted and the odd lines that need to be repaired. Therefore, it is desirable to reduce the conveying speed of the portion to be coated 20. By reducing the moving speed of the object to be coated 20, time for repairing the defective portion is secured, so that it is not necessary to operate the coating head 13 at high speed, and the control is simplified.

  The defect of the paint surface occurs, for example, because the spray nozzle provided in the paint head 12 is clogged due to intrusion of foreign matters such as dust, or the paint has run out. For example, if a specific injection nozzle is clogged with a single color coating, a line missing defect occurs, and if a specific color paint is cut off with a color paint, a color defect in which a correct color is not reproduced in the painted portion of the color paint occurs.

  The control means 17 identifies the type and coordinates of such a defective portion and generates repair data by image processing for comparing the image obtained by photographing the painted surface painted by the painting head 12 and the painting data. To do. This repair data is, for example, a painting pattern for painting only the part of the line missing when the line missing defect as described above is specified. In addition, when a color defect as described above is specified, a paint that is not applied is determined from the color of the defective part on the painted surface, and a coating pattern for applying only the paint to the defective part is obtained.

  In the configuration in which the coating heads 12 and 13 are moved relative to the stationary object 20, the photographing means 17 and the coating head 13 move following the coating head 12 on the downstream side in the moving direction. .

  FIG. 2 is a flowchart for explaining the basic processing of the method of the present invention.

  In this basic process, the control means 17 stands by until the article 20 is conveyed (step 101). And if the front-end | tip of the to-be-coated object 20 is detected by the detection means 16, the following process will be started after predetermined time progress.

That is, the coating heads 12 and 13 are simultaneously operated according to the coating data allocated to the coating heads 12 and 13 in advance, and the portion of the article 20 that passes directly under the coating head 12 and the coating head 13. Paint the part that passes directly under and immediately after,
When the painted surface immediately after painting by the painting head 12 comes directly below the photographing means 17, the painted surface is photographed (steps 102 and 103).

  Next, the photographed image of the painted surface is compared with the painting data assigned to the painting head 12, and if there is a defective portion on the painted surface, repair data for repairing the defective portion is generated (step 104). ).

  Then, when the painted portion including the defective portion passes directly under the coating head 13, the coating head 13 is operated according to the repair data to repair the defective portion (step 106). Thereafter, it is determined whether or not the entire coating has been completed. If it has not been completed, the above process is repeated. If it has been completed, the process is terminated (step 107).

  With the configuration as described above, there is an effect that even if the clogging of the nozzle or the paint out occurs in the coating head 12 while the workpiece 20 is being coated, coating failure does not occur. In addition, an operator can maintain the painting head 12 while painting.

  FIG. 3 is a schematic view showing a modified example of the ink jet coating apparatus for carrying out the method of the present invention. The same reference numerals are given to the same components as those in FIG. 1, and the description will be omitted.

  This coating apparatus 1A is different from the coating apparatus 1 in that a scanning type coating head is provided as the coating heads 12 and 13. That is, the coating heads 12 and 13 are configured to move along the support means 15 in the direction of the arrow in the figure. This movement is possible by a timing belt or the like, and is controlled by the control means 17. When such a scanning type coating head is used, the number of spray nozzles is small, and it is possible to deal with a wide range of painted surfaces that are difficult to paint with a line type coating head.

  In this configuration, the conveying means 11 conveys the object to be coated 20 while repeating the advance and stop using the width of the coating head 12 as a step. The coating by the coating head 12 is performed by spraying the coating material while moving the coating head 12 along the support means 15 while the conveyance is stopped. In addition, photographing of the painted surface by the photographing means is also performed by scanning and photographing the painted surface immediately after being painted by the painting head 12 while moving the photographing means along the supporting means 15 while the conveyance is stopped. Made. The mechanism of the painted surface repair process is the same as that of the coating apparatus 1 described above.

  FIG. 4 is a schematic view showing another modified example of the ink jet coating apparatus for carrying out the present invention. The same reference numerals are given to the same components as those in FIG. 1 and the description will be omitted.

  The coating apparatus 1B is characterized in that the coating head 12 and the photographing means 14 are integrally configured. With such a configuration, the positional relationship between the coating head 12 and the photographing means 14 becomes more precise, so that accurate repair data can be generated. For this reason, the repair of the painted surface by the painting head 13 is finished more beautifully.

It is the schematic diagram which showed the basic principle of the inkjet coating apparatus for enforcing the method of this invention. It is a flowchart explaining the basic process of the method of an Example. It is the schematic diagram which showed the modification of the inkjet coating apparatus for implementing this invention. It is the schematic diagram which showed the other modification of the inkjet coating apparatus for implementing this invention.

Explanation of symbols

12 First painting head 13 Second painting head 14 Imaging means 20 Object to be painted

Claims (3)

In the method of inkjet coating while moving the object to be coated relative to the coating head,
A step of coating the object to be coated by simultaneously operating the first and second coating heads according to the coating data distributed in advance between the first coating head and the second coating head;
Photographing the painted surface immediately after being painted by the first painting head by photographing means;
Comparing the image of the painted surface photographed by the photographing means with the coating data allocated in advance to the first painting head, and if there is a defective portion on the painted surface, for repairing the defective portion A process of generating repair data;
An ink jet coating method comprising a step of further operating a second coating head different from the first coating head in accordance with the repair data to paint the defective portion. In claim 1,
An inkjet coating method in which the photographing means is on the downstream side in the moving direction of the object to be coated with respect to the first coating head. In claim 1 or 2,
An inkjet coating method for reducing a moving speed of the object to be coated when the defective portion is repaired by the second coating head.

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