EP1892107A1 - Apparatus for printing a pattern on workpieces - Google Patents

Abstract

The device (1) has a workpiece carrier device (20) carrying a workpiece (2) to be patterned. A detection device (40) detects a relative position and distance between an ink-jet printing device (10) and a surface of the workpiece to be patterned, during printing, where the detection device is placed in a preset and fixed relationship to the printing device. A control device is arranged such that nozzles (12) of the printing device are selectively connected and disconnected in dependent of a detection result of the detection device and that nozzles are adjustable in groups by an actuating unit. An independent claim is also included for a method for patterning of workpieces.

Description

Technical area

The invention relates to a device for patterning workpieces, which are preferably at least partially made of wood, wood-based materials or the like, according to the preamble of claim 1.

State of the art

A device of the type mentioned is, for example, from the DE 100 31 030 B4 known and has sensors for coarse detection of the contour and thickness of the workpieces to be printed, which are mounted on a conveyor or on a portal. However, it has been found that the workpieces printed with such devices often have an inferior print image.

Furthermore, the not yet published European patent application filed by the Applicant concerns EP 05 009 326.9 also a device according to the preamble of claim 1.

Presentation of the invention

It is therefore an object of the present invention to provide a generic device for patterning of workpieces, which allows an improved print image quality.

This object is achieved by a device according to claim 1. Particularly advantageous developments of the invention are specified in the dependent claims.

The invention is based on the finding that impairments of the printed image in the case of workpieces arise primarily from the fact that, in known devices, the print head and the work piece are not in a sufficiently precise relative position relative to one another and are thereby printed with inaccurate "passer". This sometimes also causes some areas of the workpiece to be double-printed or oversprayed, i. E. printing is performed beyond a free edge of the workpiece and ink mist is deposited on an adjacent surface of the workpiece.

Against this background, it is provided according to the invention that the detection device is arranged and arranged to be in a predetermined, fixed relationship to the ink-jet printing device at least during printing and / or at least the distance between the ink-jet printing device and to detect at least one surface to be sampled of the respective workpiece to be sampled.

The invention thus provides, within the common concept of improving relative positioning, two alternative (and also combinable) solutions to the above common problem. In any case, an improvement of the printed image is achieved by optimizing the relative positioning between the workpiece and printing device according to the invention.

By arranged in a predetermined, fixed relationship to the printing device detecting any deviations, for example, by Conveying movements of the conveyor, temperature fluctuations or the like result, are eliminated, so that the accuracy of the relative positioning and thus the print quality can be significantly increased. This applies analogously to the measure according to the invention, not only the contour or position of the workpiece, but also to detect its distance from the printing device. In this way, either the relative position can be corrected to a desired value, or the operation of the printing device can be adapted to the detected actual value of the distance.

Although the use of at least one ink-jet printing device is preferred within the scope of the invention, other printing devices may alternatively or additionally be used.

In the context of the invention, it is in principle possible to arrange the ink-jet printing device stationary and feed the workpieces to be sampled along it using the conveying device. It is also possible to make the printing device movable, or to provide a combination of both, i. that both the workpieces and the printing device are moved during the printing process using the conveyor.

Although the detection device may be located anywhere within the scope of the present invention, it has proven to be advantageous in view of the predetermined, fixed relationship with the pressure device that the detection device is arranged at least partially on the pressure device. As a result, possible deviations can be minimized particularly effectively, in particular if sensors of the detection device, which will be discussed in more detail below, are arranged in the region of the nozzles of the pressure device.

In addition to the detection device discussed above, the device according to the invention according to an embodiment of the invention further comprises a coarse detection device, which is preferably arranged stationary. In this way, the contour and position of the respective workpiece can first be detected using the coarse detection device, before a substantially more precise relative position can then be determined with the (fine) detection device, which is arranged in a fixed relationship to the printing device. This two-stage construction of the device enables rapid operation with high print quality.

According to one development of the invention, the detection device and / or the coarse detection device each have a plurality of sensors, in particular distance sensors. It is particularly preferred that at least one of the sensors is arranged rotatable about at least one axis and / or movable. As a result, the sensors can not only be used variably, but it is also possible to detect a minimum or maximum distance by rotating and / or moving the sensors with a plurality of measurements.

With regard to the predetermined, fixed arrangement of the detection device with respect to the printing device is provided according to a development of the invention that at least one of the sensors is arranged on the printing device. In contrast, in the case of the coarse detection device, it is preferred that at least one of the sensors is arranged on the workpiece support device. In this way, optimal detection results can be achieved in each case, which are matched to the purpose of the respective (coarse) detection device.

In the case of the sensors arranged on the pressure device, it has proved to be advantageous that at least one sensor is arranged such that it detects in the direction in which which ejects the ink drops of at least one nozzle. In this way, the detection results of the detection device can be evaluated in an optimal manner for the printing operation.

Furthermore, according to a further development of the invention, it has proven to be advantageous for at least one sensor to be arranged on the pressure device via a movable and / or pivotable element and thus preferably to be brought into a position in which the sensor detects in a direction which substantially is orthogonal to the direction in which the ink drops of at least one nozzle are ejected. Due to the pivotability or movability of the distance sensor, this can be used for different types of measurement, for example, for a pure distance measurement and for a thickness measurement, which will become more apparent from the detailed description below.

The type and configuration of the respective sensors is not particularly limited in the context of the present invention. For example, these may be ultrasonic sensors, laser pointers and a further large number of sensors. In addition, according to a further aspect of the invention, it is provided that the detection device and / or coarse detection device respectively has at least one image detection sensor, which is preferably arranged on the printing unit. The provision of an image acquisition sensor opens up completely new possibilities, not only to capture the geometry of the workpiece, but also numerous other properties such as the nature and quality of the applied print image and evaluate it for further operation. In particular, not only locally or locally geometry data are acquired by the image acquisition sensor, but an image section is obtained which contains a wealth of information and can be evaluated as a whole. The thus gained Information can be used not only for the relative positioning discussed above, but also for a general check of the print result and for a calibration of the print head, so that the quality of the print result can be further improved in this regard.

In order to be able to respond quickly and precisely to detection results of the detection device and / or coarse detection device on the part of the print head, it is provided according to a development of the invention that at least the nozzles of the printing device are adjustable at least in groups via adjusting means, in particular piezoelectric adjusting means.

According to one embodiment of the invention, the device further comprises at least one beam-like guide device, in particular a portal or a boom. Such a guide device is particularly well suited for attaching and guiding the printing device, wherein the printing device can be moved, for example, in the longitudinal direction of the guide device and the guide device itself in turn can also be moved.

Furthermore, according to a development of the invention, it is provided that at least one bar-like guide device has at least one spindle unit, which is preferably movable along the bar-like guide device and / or pivotable about an axis. Such a spindle unit can be assigned many tasks in the context of the present invention. On the one hand, it can serve to accommodate the printing unit, and for example, also to record in and interchangeable. Alternatively or additionally, the spindle unit can also serve to accommodate machining tools and / or processing units that are used in the processing and finishing of workpieces of the type in question here come. These can be simple drills or milling cutters, but also complex aggregates such as edge banding units or the like.

Furthermore, the invention provides a method of patterning workpieces using a device according to the invention comprising the features of claim 13. The essence of the method is to selectively change nozzles of the ink-jet printing device based on a detection result of the detector. H. especially on or off. As a result, it is extremely easy and flexible to respond to possible target / actual deviations during operation of the device, so that the print quality can be improved in a simple and reliable manner.

Brief description of the drawings

Fig. 1

shows schematically a perspective view of a device for patterning workpieces according to an embodiment of the invention;

Fig. 2

shows schematically a partial plan view of the device shown in Figure 1;

Fig. 3

shows schematically a partially cutaway front view of the device shown in Figure 1;

Fig. 4

shows further details of the printing device in Fig. 1 apparatus shown;

Fig. 5

shows further details of the printing device of the device shown in Fig. 1;

Fig. 6

illustrates the operation of the device shown in Fig. 1.

Detailed description of preferred embodiments

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

An apparatus 1 for patterning workpieces as a preferred embodiment of the present invention is shown schematically in FIG. 1 in a perspective view. The device is used for patterning of workpieces 2, which in the present embodiment at least partially made of wood, wood materials, plastics or the like, as they are often used in the field of furniture and kitchen.

The device 1 comprises an ink-jet printing device 10, which operates in the present embodiment according to the drop-on-demand principle. As best seen in Fig. 4, the ink-jet printing apparatus 10 includes a plurality of nozzles 12 from which ink droplets may be ejected and which are arranged in a plurality of rows in the present embodiment, each row for ejecting a predetermined one Color is provided, for example, the colors cyan, magenta, yellow and black.

Furthermore, drying units 14, for example UV dryers, are provided on the printing device 10, which are used to rapidly dry the ink applied by the printing device in order to prevent possible distortions or smearing of the printed image.

The printing device 10 is provided in the present embodiment on a spindle unit 6 or in this, although this is not shown in detail in Fig. 1. The spindle unit is preferably such a spindle unit, which is also used for receiving and exchangeable machining tools or Processing units is suitable. The spindle unit 6 is provided in the y-direction movable on a portal 4, which in turn can be equipped to be movable in the x-direction. In this case, two portals 4 are provided in the present embodiment, each of which may carry one or more spindle units 6, which may optionally be arranged on opposite sides of the respective portal 4. It should be noted that the portals 4 may optionally be designed as a boom. The spindle units 6 can be fitted automatically or manually via tool magazines (not shown here in detail) with machining tools and / or machining units and one or more printing devices 10.

Below the gantries 4 extends in the present embodiment, a workpiece table 20 for supporting the respective workpiece to be sampled 2, which is movable in the x-direction shown in Fig. 1. The workpiece table 20 can be designed in various ways and, for example, also be formed by a circulating conveyor belt or the like. Due to its movability, the workpiece table 20 simultaneously forms a workpiece carrying device and a part of the conveying device according to the present invention.

The arrangement of a plate-shaped workpiece 2 on the workpiece table 20 is shown in more detail in Fig. 2 in a plan view. In the present embodiment, the workpiece table 20 has extendable stop bolts 22, to which the workpiece 2 can be applied for coarse positioning. Further, a plurality of distance sensors 52 are arranged on the workpiece table 20, which are part of a coarse detection device 50. The distance sensors shown in Fig. 2 are adapted to detect the distance between the sensors and a side surface (narrow surface) of the respective workpiece 2. In this case, the sensors 52 are in the present embodiment to an axis orthogonal to the surface of the workpiece table 20 extending axis and optionally movable parallel to the surface. The coarse detection device 50 thus serves for coarse detection of the geometry and positioning of the respective workpiece 2.

Further details of the workpiece table 20 are shown in Fig. 3, which shows a partially sectioned front view of the device shown in Fig. 1. There, it can be seen that the respective workpiece 2 can be fixed on the workpiece table 20, for example via vacuum cups 24. It is also possible to integrate corresponding suction or suction openings in the workpiece table or a workpiece band.

Furthermore, the device 1 according to the invention comprises a detection device 40 for detecting the relative position of the ink-jet printing device 10 and the respective surface of a workpiece 2 to be patterned. The detection device 40 in the present embodiment has several types of sensors 42, 46 which are arranged in the Figures 3, 4 and 5 are best seen. First, in the present embodiment, the detection device 40 includes three distance sensors 42 disposed on the pressure device 10 adjacent to the nozzles 12 and measuring in a direction substantially parallel to the ink ejection direction of the nozzles 12 (FIG. 4). On the one hand, the absolute distance between the pressure device 10 and the workpiece 2 can be determined with these distance sensors, but beyond that, it is also possible to deduce the exact contour of the respective workpiece 2 from the distance data obtained.

As can best be seen in FIGS. 3 and 5, further distance sensors 42 are each arranged on the printing device 10 via an element 44 pivotable in the present embodiment. By the swiveling Element 44, the respective sensor in an extended position can be brought, which is best seen in Fig. 5. In this position, the sensors 42 shown in FIG. 5 measure in a direction that is substantially orthogonal to the ink ejection direction of the nozzles 12. As a result, the thickness or height of the respective area to be printed can be detected and an "overspray" avoided.

Moreover, on the printing device 10 adjacent to the ink ejection nozzles 12 in the present embodiment, an image sensing sensor 46 is arranged, which also measures in a direction substantially parallel to the ink ejection direction of the nozzles 12. The image-capturing sensor 46 can be, for example, a CCD camera or the like, which can produce a complete image of a region of the respective workpiece 2 to be printed or already printed.

Although not shown in the figures, on the one hand all sensors and on the other hand the pressure device and preferably also the other operating components of the device 1 are connected to a control device which evaluates the respective data detected by the sensors and on this basis the operation of the device, in particular the Printing device controls. The operation of the device can be represented as follows.

First, a workpiece 2 is roughly positioned over the stopper pins 22 on the workpiece table 20 and fixed via the vacuum cups 24. Subsequently, the positioning and / or contour of the workpiece 2 are detected on the workpiece table 20 by the sensors 52 and passed this data to the control device.

Then, the workpiece table 20 is moved in the x direction, so that the workpiece 2 by substituting in the spindle units 6 tools, aggregates or printing units can be processed or finished. In this case, the operation of the printing device takes place, for example, as follows.

On the basis of the data from the sensors 52, the printing device 10 is moved with the corresponding spindle 6 along the portal 4 to the workpiece 2 to be printed. The sensors 42, 46 continuously perform a measuring operation, so that the presence and optionally the distance of the respective workpiece and beyond (by the image detection sensor 46) also further information about the workpiece 2 can be obtained. Based on these data, the controller outputs pressure signals to the respective nozzles 12 (or the associated piezoelectric actuators or thermocouples) so that the workpiece 2 is printed. Depending on the detection data of the sensors 42, 46, individual nozzles or nozzle groups can be switched on or off in order to compensate for dimensional, position or other tolerances or deviations of the workpiece 2. Alternatively or additionally, within the scope of the invention it is equally possible for individual or multiple nozzles of the printing device 10 to be produced via piezo-adjusting means or the like in order to adapt their position or ejection direction to the workpiece 2.

When printing a large side surface of a workpiece 2 in addition to the image detection sensor 46 primarily the sensors 12 arranged next to the nozzles 12, which are best seen in FIG. For printing on a narrow surface of the workpiece 2, alternatively or additionally, the sensors 42 are used, which are extendable via pivotable elements 44 in order to detect the height of the narrow surface and thus to prevent overspray.

After printing on a surface section, it may optionally be dried by the drying units 14, possibly also simultaneously with the printing operation.

The travel paths of the printing device 10 and / or of the workpiece 2 are shown schematically in FIG. The left-hand drawing in FIG. 6 shows an operation in the so-called transverse pressure, in which the printing device 10 moves back and forth along the portal 4 in the y-direction together with the spindle unit 6 and the workpiece 2 continues through the workpiece table 20 in the x-direction is clocked.

Alternatively, it is also possible to use the printing scheme shown on the right in FIG. 6, which can be referred to as longitudinal printing. In this case, the printing device 10 is substantially stationary during the printing process itself, and the workpiece 2 is reciprocated with the workpiece table 20 in the x-direction. The printing device 10 thus only needs to be clocked in the y-direction after the printing of a web has been completed. In addition, in the context of the present invention, combinations of both operations are possible, and it can be printed, for example, obliquely arranged tracks or the like.

Claims (13)

Device (1) for patterning workpieces (2), which are preferably at least partially made of wood, wood-based materials or the like, comprising: a printing device (10) which is preferably designed as an ink-jet printing device with a plurality of nozzles (12) from which ink droplets can be ejected, a workpiece carrying device (20) for carrying the workpiece (2) to be sampled, a conveying device for causing a relative movement between the workpiece (2) to be sampled and the printing device (10), and a detection device (40) for detecting the relative position between the ink-jet printing device (10) and at least one surface to be sampled (2 ') of the respective workpiece (2) to be sampled, characterized in that the detection device (40) is arranged and set up so as to be in a predetermined, fixed relationship to the ink-jet printing device (10) at least during the printing and / or at least the distance between the ink-jet printing device (10). and at least one surface to be patterned (2 ') of the respective workpiece (2) to be patterned. Apparatus according to claim 1, characterized in that the detection device (40) is at least partially disposed on the ink-jet printing device (10). Apparatus according to claim 1 or 2, characterized in that it further comprises a coarse detection means (50), which is preferably arranged stationary. Device according to one of the preceding claims, characterized in that the detection device (40) and / or the coarse detection device (50) each have a plurality of sensors (42, 52), in particular distance sensors. Apparatus according to claim 4, characterized in that at least one of the sensors (52) is arranged rotatable about at least one axis and / or movable. Apparatus according to claim 4 or 5, characterized in that at least one of the sensors (42, 52) on the workpiece support means (20) and / or at least one of the sensors on the printing device (10) is arranged. Apparatus according to claim 6, characterized in that at least one sensor (42) is arranged on the printing device such that it detects in the direction in which the ink drops of at least one nozzle are ejected. Apparatus according to claim 6 or 7, characterized in that at least one sensor (42) is arranged on the printing device via a movable and / or pivotable element (44) and is preferably brought into a position in which the sensor detects in one direction, which is substantially orthogonal to the direction in which the ink drops of at least one nozzle are ejected. Device according to one of the preceding claims, characterized in that the detection device (40) and / or the coarse detection device each having at least one image detection sensor (46) which is preferably arranged on the printing device (10). Device according to one of the preceding claims, characterized in that at least the nozzles of the printing device (10) are adjustable at least in groups by adjusting means. Device according to one of the preceding claims, characterized in that it further comprises at least one bar-like guide device (4), in particular a portal or a boom. Apparatus according to claim 11, characterized in that at least one bar-like guide means comprises at least one spindle unit (6) which is preferably along the bar-like guide means (4) movable and / or pivotable about an axis. Process for patterning workpieces (2), which preferably consist at least partly of wood, wood-based materials or the like, using a device (1) according to one of the preceding claims, characterized in that the nozzles of the ink-jet printing device (10) in Depending on a detection result of the detection device (40) are selectively changed.

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