Method for printing on a vehicle body part

Abstract

Method for printing a motor vehicle body part (14) with a body part printing arrangement (10) for printing a motor vehicle body part (14) with a target pixel pattern (M24) which has: a print head (30) that can be moved relative to the vehicle body part (14) and that can print a body part surface (16) pixel by pixel, a print image memory (24) in which the target pixel pattern (M24) is stored, a control camera (40) that captures the actual pixel pattern (M40) printed by the print head (30), wherein the control camera (40) is fixedly connected to the printhead (30), is aligned in the printing direction (x) with the printhead (30) and moves synchronously with the printhead (30), a correction module (26) which determines a difference pixel pattern (M26) from the difference between the target pixel pattern (M24) and the actual pixel pattern (M40), and a printhead correction control (28) which is connected to the correction module (26) via a data connection and which can instruct the printhead (30) to print the difference pixel pattern (M26) over the actual pixel pattern (M40) already printed on the body part surface (16), with the following process steps: Printing an actual pixel pattern (M40) by the print head (30) moving in the printing direction (x) according to the target pixel pattern (M24) onto the body part surface (16), Tracking of the actual pixel pattern (M40) by the control camera (40) in the direction of printing, Determining the difference pixel pattern (M26) in the correction module (26) from the difference between the target pixel pattern (M24) and the actual pixel pattern (M40), and The printhead (30) is instructed by the printhead correction control (28) to print the difference pixel pattern (M26) on the printed actual pixel pattern (M40) so that missing color pixels are added, with a maximum of 30 seconds elapsed between printing the actual pixel pattern (M40) and the difference pixel pattern (M26).

Description

[0001] The invention relates to a method for printing a motor vehicle body part with a body part printing arrangement for printing a motor vehicle body part with a desired pixel pattern.

[0002] For the individualization of motor vehicles, an image can be printed onto a base coat of paint on a vehicle body part, which in the simplest case is, for example, a single-color stripe. A printing arrangement for this purpose is known from DE 10 2012 006 370 A1. The printing is carried out with a printhead that has an array of offset print nozzles in a multitude of rows, so that the printed image can be applied with a resolution of, for example, 300 dpi.

[0003] In larger areas, missing pixels, i.e., color pixels that were accidentally not printed, become noticeable and are therefore undesirable.

[0004] From DE 10 2012 209 305 A1 it is known to print a relief-like surface on a plastic article a second time if the first print was incomplete.

[0005] The object of the invention is therefore to create a method for printing a bodywork component with high print quality.

[0006] This problem is solved according to the invention by a method for printing a body part with the features of claim 1.

[0007] The body panel printing arrangement according to the invention for printing a vehicle body panel with a desired pixel pattern comprises a printhead that is movable relative to the vehicle body panel and can print a body panel surface pixel by pixel. The desired pixel pattern is stored in a print image memory. Furthermore, the printing arrangement comprises a control camera that captures the actual pixel pattern printed by the printhead almost immediately after the actual pixel pattern has been printed by the printhead.

[0008] A correction module is provided that determines a differential pixel pattern from the difference between the target pixel pattern and the actual pixel pattern. A printhead correction control is also provided, which is connected to the correction module via a data link and promptly instructs the printhead to print the differential pixel pattern precisely over the actual pixel pattern already printed on the body panel surface. The printing of the differential pixel pattern preferably occurs so soon after the printing of the actual pixel pattern that the ink pixels of the actual pixel pattern on the body panel surface are still sufficiently fluid for the subsequently applied ink pixels, according to the differential pixel pattern, to blend seamlessly with the ink pixels of the already printed actual pixel pattern.

[0009] In this way, missing color pixels are added through the correction print. Accidentally overlapping color pixels cannot be corrected in this way, but are not as visually significant as missing color pixels compared to the intended pixel pattern.

[0010] The control camera is directly or indirectly connected to the printhead and is aligned with the printhead in the printing direction, for example, centered. The control camera moves synchronously with the printhead and preferably lags behind it. Particularly preferably, two control cameras can be provided, so that the actual pixel pattern can be printed in both opposing printing directions, and one of the two control cameras is always lagging behind the printhead.

[0011] This arrangement enables very timely capture of the printed actual pixel pattern, which in turn enables very timely printing of the difference pixel pattern, so that the color pixels from the correction run can blend or merge with the still fluid color pixels of the actual pixel pattern.

[0012] According to the method claim for printing a motor vehicle body part using the body part printing arrangement, the following method steps are provided: First, an actual pixel pattern is printed onto the surface of the vehicle body part by the printhead, which moves across the body panel in the printing direction, according to the target pixel pattern. The printhead receives the control instruction to print a pixel pattern according to the target pixel pattern. However, the printhead always prints an actual pixel pattern that does not necessarily correspond completely to the target pixel pattern, but may, in particular, contain missing pixels due to various causes, especially mechanical ones.

[0013] With only a short delay, the control camera captures the actual pixel pattern, lagging behind in the printing direction. The control camera does not capture the trajectories of the color pixels before they hit the body panel surface, but rather captures only the body panel surface itself with the already printed actual pixel pattern.

[0014] The correction module then determines the difference pixel pattern from the difference between the target pixel pattern and the actual pixel pattern.

[0015] Finally, the printhead correction control instructs the printhead to print the difference pixel pattern precisely over the already printed actual pixel pattern. In this way, the pixels missing in the actual pixel pattern are added, thus preventing noticeable color pixel gaps.

[0016] The time between printing the actual pixel pattern and the difference pixel pattern is a maximum of 30 seconds, preferably less than 15 seconds. The entire correction print run therefore always takes place immediately after printing the target or actual pixel pattern, which can be printed in one pass by the print head, and not only after the entire image to be printed has been completed.

[0017] An embodiment of the invention is explained in more detail below. The figures shown are: Fig. 1 schematically a body part printing arrangement with a printing unit comprising a print head, a control camera and a print control unit, and Fig. 2 a schematic representation of a target pixel pattern, an actual pixel pattern and a difference pixel pattern.

[0018] In the Fig. Figure 1 schematically depicts a body panel printing arrangement 10 for printing an image or a target pixel pattern M24 onto a vehicle body panel 14. A target pixel pattern, as used here, is always understood to be a pixel pattern that can be printed by a print head 30 in one pass. An image is composed of a multitude of target pixel patterns. Typical images in the automotive sector are simple, monochrome geometric patterns, especially stripes, etc.

[0019] As an example, a vehicle body part 14 of a motor vehicle 12, lying essentially in a horizontal plane xy, is printed with a simple image, for example, a longitudinal stripe on the hood. The image is composed of a multitude of target pixel patterns M24, which are stored in a print image memory 24. The vehicle body part 14 has a body surface 16 that is already painted with a base color.

[0020] The body panel printing arrangement 10 has a motor-driven print unit 20 that is movable in all spatial axes x, y, z and comprises a print head 30, a control camera 40, and a print unit controller 22. The print head 30 typically has a resolution of 16–800 dpi and can print at a maximum speed of approximately 1000 mm / s in the x-direction. The distance of the print head 30 from the body panel surface 16 is typically 3 to 50 mm.

[0021] The control camera 40 has a detection area 42 which, in the static state, does not overlap with the actual pixel pattern M40 printed simultaneously by the print head 30.

[0022] The control camera 40 is aligned centrally with the printhead 30 with respect to the printing direction x and moves in perfect synchronicity with the printhead 30. The resolution of the control camera 10 is several times the resolution of the printhead, preferably at least five times the resolution of the printhead.

[0023] The print engine control unit 20 has a correction module 26, which is connected via a data connection to the print image memory 24 and to a correction module 26. The correction module 26 determines a difference pixel pattern 26 from the actual pixel pattern M40 captured by the camera and the desired target pixel pattern M24 by subtraction.

[0024] The printhead correction control 28 promptly instructs the printhead 30 to print the difference pixel pattern M26 exactly over the actual pixel pattern 40 already printed on the body part surface 16 after a positive finding of a correction requirement, i.e., in the case of a positive difference pixel pattern M26, so that the resulting pixel pattern finally corresponds to the target pixel pattern M24.

[0025] The printing of the difference pixel pattern M26 occurs so quickly, within a maximum of a few seconds, after the printing of the actual pixel pattern or after the actual pixel pattern 40 has been captured by the control camera 40, that the color pixels of the actual pixel pattern M40 are still sufficiently fluid for the color pixels of the subsequently printed difference pixel pattern M26 to align with the color pixels of the already printed actual pixel pattern M40. Only a few seconds elapse between the printing of the actual pixel pattern M40 and the difference pixel pattern M26.

Claims

[1] Method for printing a motor vehicle body part (14) with a body part printing arrangement (10) for printing a motor vehicle body part (14) with a desired pixel pattern (M24) comprising: a print head (30) that can be moved relative to the vehicle body part (14) and that can print a body part surface (16) pixel by pixel, a print image memory (24) in which the target pixel pattern (M24) is stored, a control camera (40) that captures the actual pixel pattern (M40) printed by the print head (30), wherein the control camera (40) is fixedly connected to the printhead (30), is aligned in the printing direction (x) with the printhead (30) and moves synchronously with the printhead (30), a correction module (26) which determines a difference pixel pattern (M26) from the difference between the target pixel pattern (M24) and the actual pixel pattern (M40), and a printhead correction control (28) which is connected to the correction module (26) via a data connection and which can instruct the printhead (30) to print the difference pixel pattern (M26) over the actual pixel pattern (M40) already printed on the body part surface (16), with the following process steps: Printing an actual pixel pattern (M40) by the print head (30) moving in the printing direction (x) according to the target pixel pattern (M24) onto the body part surface (16), Tracking of the actual pixel pattern (M40) by the control camera (40) in the direction of printing, Determining the difference pixel pattern (M26) in the correction module (26) from the difference between the target pixel pattern (M24) and the actual pixel pattern (M40), and The printhead (30) is instructed by the printhead correction control (28) to print the difference pixel pattern (M26) on the printed actual pixel pattern (M40) so that missing color pixels are added, with a maximum of 30 seconds between printing the actual pixel pattern (M40) and the difference pixel pattern (M26).

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