Machine and method for applying at least one graphic to a wooden stick

Abstract

The machine and method for applying at least one graphic to a wooden stick has a printing unit with at least one printhead for a printing medium such as ink. To design the machine and method in such a way that the production of printed wooden sticks is simple and cost-effective, at least one pretreatment unit is installed upstream of the printing unit and / or at least one post-treatment unit is installed downstream. Within the machine, the wooden stick is pretreated or post-treated before and / or after the printing process.

Description

The invention relates to a machine for applying at least one graphic to a wood bar according to the preamble of claim 1 and to a method for applying at least one graphic to a wood bar according to the preamble of claim 10.In order to apply a graphic to wood bars, the graphic is printed on a sheathing material, with which the wood bars are subsequently sheathed. A protective layer, for example a clear lacquer, is then applied to the sheathing material in order to protect the graphic against external influences.Different machines are required for the printing process, the sheathing and the application of the protective layer, which not only makes production for printed wood bars considerably more expensive, but also very complicated.The object of the invention is to design the machine of the generic type and the method of the generic type such that the production of printed wood bars is possible in a simple and cost-effective manner.This object is achieved in the generic machine according to the invention with the characterizing features of claim 1 and in the generic method according to the invention with the characterizing features of claim 10.In the machine according to the invention, not only is the printing of the wood bar carried out within the machine, but a pretreatment and / or a posttreatment is carried out on the wood bar depending on the requirements. For this purpose, the machine is equipped, in addition to the printing unit, with at least one pretreatment unit and / or at least one aftertreatment unit. Thus, with the machine according to the invention, the wood rod can be printed very easily in such a way that it no longer requires any further aftertreatment after it has exited the machine, but can instead be used directly for the intended purposes of use.The pretreatment unit advantageously has at least one print head for applying a coating of the wood bar. This makes it possible to prepare the top side of the wood bar to be printed before the printing operation in such a way that the graphic can be applied perfectly to the wood bar.The pretreatment unit is advantageously provided with at least one drying device. It is possible with it to dry the top side to be printed to such an extent before the printing operation that a perfect print job is subsequently ensured.The post-treatment unit is preferably provided with at least one means for applying a cover layer to the printed graphic. The top layer formed a protective layer to protect the graphic on the wood bar.It is advantageous if the post-treatment unit has at least one drying device. It is then possible to dry the wood bar before leaving the machine to such an extent that it can be treated without problems immediately upon leaving the machine.The printing unit is advantageously designed such that it can be used to apply a multicolor print to the wood rod. For this purpose, corresponding print heads for printing inks of different colors are provided.In order to achieve optimum print quality, the print heads are advantageously adjustable relative to the wood bar. This makes it possible to optimally adjust the distance of the print heads from the top side to be printed in such a way that an exact, sharp and clean printed image is obtained.The adjustability of the print heads also makes it possible to adapt them, for example, to upper sides to be printed provided on the wood bar at different slopes. Thus, the wood rod can have, for example, obliquely lying surface parts which can be printed perfectly owing to the adjustability of the print heads. The adjustability of the print heads also makes it possible to print, for example, all the longitudinal sides of a wood bar.Finally, the advantageous adjustability of the print heads makes it possible for two upper side regions arranged at different slopes to be printed on the wood bar at the same time. This keeps the number of printheads within a reasonable range.The print heads are preferably adjustable in a controlled manner. This makes it possible to adjust the print heads during the printing and / or treatment process with respect to the upper side of the wood bar to be treated / printed. Thus, it is possible, for example, to print reliably upper sides which are curved or obliquely running in the transport direction of the wood bar, because the print heads can be tracked in a targeted manner as a result of the control.For this measure, it is advantageous if the position and orientation of the upper side of the wood bar to be printed is previously detected by means of sensors, camera systems and the like and the corresponding signals are fed to a controller which, according to these signals, controls the print heads such that they come into their respective printing / treatment position.In an advantageous embodiment, the machine is provided with at least one transport device, with which the wood bar is transported through the machine. With the transport device, the wood bar can be reliably guided through the machine in order to carry out the required processes on the wood bar.The transport device extending through the machine can be advantageously regulated so that a desired transport speed of the wood bar can be reliably set during passage through the machine so that the graphic can be applied with high accuracy.In the method according to the invention, the wood rod is treated or post-treated within the machine before and / or after the printing operation. As a result, the wood rod can be printed in a simple manner, so that it no longer requires any further aftertreatment after it has exited the machine. The wood bar can be directly used for its purpose.In an advantageous method procedure, the wood rod is provided with a filler and / or a primer and / or a base coating before printing. In this way, the top side to be printed can be pretreated in such a way that the graphic can subsequently be attached to the wood bar with high accuracy.A further advantageous procedure results if the wood rod is dried or dried on its upper side to be printed before printing. Then, the subsequent application of the printing medium is possible without any problem, so that a clean printed image is obtained. The wood rod is preferably dried or dried after printing and / or provided with a protective layer on the printed side. The protective layer protects the printed upper side of the wood bar during its further handling. The drying or drying of the wood bar on the printed side ensures that the print job after the printing operation is not impaired during further handling.An optimum procedure results when the wood rod is printed in a continuous process. Between the individual method steps, the wood bar therefore no longer has to be positioned. This not only affects the accuracy of the pre / post treatment and the printing operation, but also results in shortened processing times.In this case, it is advantageous if the wood bar is transported at constant speed. Then, the feed speed of the wood bar can be optimally adjusted.It is advantageous if the contour shape of the wood bar is detected by sensors and / or camera systems. As a result, the position and orientation of the upper side of the wood bar to be printed can be determined exactly.The signals of the sensors and / or camera systems are advantageously fed to a controller, which adjusts the print heads relative to the upper sides of the wood bar to be printed on as a function of the signals.The subject matter of the application results not only from the subject matter of the individual patent claims, but also from all the details and features disclosed in the drawings and the description. Although they are not the subject matter of the claims, they are claimed as essential to the invention, provided they are novel, individually or in combination, compared with the prior art.Further features of the invention are evident from the further claims, the description and the drawings.The invention is explained in more detail with reference to an exemplary embodiment shown in the drawings. They show FIG. 1.1 shows a schematic illustration of three process steps in the application of a graphic to a wood rod, FIG. 1.2 shows a schematic illustration similar to FIG. 1.1 of other process steps during the application of a graphic to a wood bar, FIG. 1.3 shows, in a representation corresponding to FIG. 1.1, another sequence of process steps during the application of a graphic to a wood rod, FIG. 2 shows a schematic illustration and in front view two print heads with which a wood rod is printed, FIG. 3 shows a schematic illustration of a machine according to the invention for applying a graphic to a wood rod passing through.With the procedure described below, it is possible to print a wood rod directly with an upper side. This can be done by applying a graphic, which can be, for example, a sketch, a photograph or the like. The printed wood bars can then be assembled into a final product, such as a board, frame and the like. In this case, the wood bars are printed in such a way that the desired graphic is formed on the end product. The printing of the wood bars is advantageously effected by a digital printing press which is known per se and therefore also will not be explained in more detail. The printing press is designed such that it prints the wood bars in the required manner when they are transported past one or more print heads of the printing press.Digital printing is to be understood as ink jet printing methods or inkjet methods.Preferably, the wood bars are transported through the printing press during the printing operation. However, it is also possible for the wood bars to be stationary and for the print heads of the printing press to move with respect to the wood bars, i.e. to be moved past them. The relative movement between the wood bars and the print heads can also be achieved in that both move relative to one another during the method such that the wood bars are printed to the desired extent.The wood bars can consist of solid wood or of wood materials, for example MDF.The wood bars are printed successively in such a way that the end product, after the wood bars have been assembled or arranged, has the desired graphic.On the other hand, the printing on the wood bars is not dependent on the fact that a graphic is formed with them on a final product. In principle, the procedure is also suitable when, for example, each wood bar has its own graphic which is not part of an entire graphic on the end product.Fig. 1.1 schematically shows a wood bar 1 having an elongate extension and being transported in its longitudinal direction through a machine 2 in which different process steps are carried out for printing on the wood bar 1. Thus, different machines are not necessary for the different process steps, which machines would also have to be linked to one another by corresponding transport devices.In a first process step I, the wood bar 1 is pretreated in the machine 2. In the subsequent last process step III, the wood rod 1 is subjected to a post-treatment.In process step I, a filler 3 can be applied to the wood bar 1. It can be used to provide a highly absorbent surface of the wood bar 1 with a liquid basecoat which is printable and gives the wood bar 1 a desired surface structure and property. This property can consist, for example, in forming a closed, non-absorbent or only slightly absorbent surface on a strongly absorbent surface, as is usually present in a wood rod, so that the subsequent pressure is perfectly successful.In process step I, a primer 4 can then be applied, which can be used as adhesion promoter between the different materials of the wood bar 1 and the subsequent coating.Two separate print heads can be provided for the application of the filler 3 and of the primer 4. However, it is also possible to use a combined print head for the application of the filler 3 and the primer 4. The use of a combined print head is possible because filler 3 and primer 4 are chemically combined as a substance. With the print heads, a corresponding quantity can be applied with the corresponding liquid to the wood rod 1 on its printable side in the digital printing method. Depending on the nature of the upper side of the wood rod 1 to be printed, the filler 3 and the primer 4 can be applied one after the other. Depending on the surface condition, however, it is also sufficient to apply only the filler 3 or only the primer 4.In the ideal case, it is not necessary to subject the top side of the wood bar 1 to be printed to an abrasive process step, such as grinding.If required, the side of the wood bar 1 to be printed which has been pretreated with the filler 3 and / or the primer 4 can be provided with a base coating 21. Thus, a white basecoat can be applied, for example by an inkjet method. This process stage is optional and not absolutely necessary.For the application of the filler 3 and the basecoat 21, or for the application of the primer 4 and the basecoat 21, a combined print head can be used if, as in the case of filler 3 and primer 4, filler 3 and basecoat 21, or primer 4 and basecoat 21, are chemically combined as a substance.In process step I, subsequent to the application of filler 3 and / or primer 4 and / or basecoat 21, a pinning method 5 may be carried out. This pinning method 5 serves to dry the upper side of the wood rod provided with the filler 3 and / or the primer 4 and / or the basecoat 21 to such an extent that the printing process can take place immediately subsequently in process step II.In the exemplary embodiment, a print head is provided for each filler 3, primer 4 and basecoat 21. In principle, more than one print head can be provided for the filler 3 and / or the primer 4 and / or the base coating 21, in order, for example, to apply a plurality of layers or to achieve better coverage.For the pinning method, a corresponding unit is provided, which is installed in the printing press 2 in a similar manner to the print heads and has at least one drying unit, such as a UV or LED unit. Such units are known and will therefore not be explained in more detail.The pinning method 5 can advantageously be carried out by means of UV lighting means. Other suitable energy sources for the drying process are also conceivable. The pinning method 5 is matched to the entire printing process and the printing medium used, such as ink.Pinning process 5 can be carried out after application of filler 3 or primer 4 or basecoat 21, as necessary.During further transport through the printing press 2, the wood rod 1 reaches the digital printing area II, in which the desired decoration is applied to the wood rod 1, advantageously in a four-color printing process. The decor can be, for example, a graphic, an image or a pattern.By way of example, FIG. 1.1 shows that the decor is printed with four print heads / colors 6 to 9, of which, by way of example, the color 6 is black, the color 7 is yellow, the color 8 is magenta and the color 9 is cyan. With these four colors 6 to 9, a very high image quality can be produced in four-color printing.Depending on requirements, special colors can also be used for printing, such as neon colors. The printing press 2 can also have at least one further color with which the color space can be expanded. In this case, the decoration is applied to the wood rod 1 not in four-color printing but in multicolor printing.Corresponding further print heads are used for the special color and / or the further color.More than one print head can be provided for each of the colors in order to obtain repeated printing and / or better registration.Following four-color or multicolor printing, a pinning method 5 can again be used in order to dry the ink applied to the wood rod 1. As a result, it is possible to supply the wood bar 1 to the post-treatment according to process step III immediately after the printing process in process step II.In process step III, a protective layer is first applied to the printed side of the wood bar 1 in a coating process 10. In this coating process, the coating is advantageously applied by the inkjet process. The coating method 10 can be used to change the surface property of the printed wood rod 1. Thus, for example, with the cover layer, a matt finish of the printed upper side or, for example, a certain degree of gloss can be achieved. A further possibility for the coating is to form it in such a way that the printed side of the wood bar 1 feels more valuable, for example, which can be achieved by a corresponding haptic configuration of the coating.In particular, the coating serves to protect the printed upper side of the wood bar 1 against external influences. In this case, the coating serves as mechanical protection of the printed side.Furthermore, the coating can also be formed in such a way that a lotus effect is achieved therewith, i.e. a water-repellent effect is achieved.The coating can also serve to protect the printed side against chemicals, such as cleaning agents, or against UV radiation.At this stage of the method, further protection mechanisms can be set with the corresponding print head and the color management.In process step III, a drying process 11 can be connected to the coating process if the printing medium applied to the wood bar 1 should not yet be completely dry as the machine 2 exits. For the drying process, a corresponding unit is used, which is inserted into the printing press 2 like the print heads.It follows from FIG. 1.2 that not all method steps are necessary in order to print on the wood bar 1 during its passage through the printing machine 2. In the method according to FIG. 1.2, process step III is not provided for the post-treatment of the printed wood rod 1. In this case, it is sufficient to pretreat the wood rod 1 in process step I in the described manner and to print it in process step II in the described manner.FIG. 1.3 shows that, in the case of a different method implementation, process step I can be dispensed with. In this case, the wood bar 1 passing through the printing machine 2 in its longitudinal direction is printed in process step II and after-treated in process step III. Process steps III have been described with reference to FIG. 1.1, so that reference can be made to this.FIG. 2 shows, in an end view or in a section transversely to the transport direction 20 of the wood bar 1 through the printing press 2, schematically the possibility of providing the print heads of the printing press 2 in an adjustable manner, so that obliquely lying upper sides 13, 14 of the wood bar 1 can also be treated or printed with them. Representative of the described print heads 3 to 11, 21, the one print head 12 is shown in FIG. 2.The upper sides 13, 14 of the wood bar 1 can also be inclined differently in the example shown.Each top side 13, 14 is assigned the corresponding print heads, which have been described with reference to FIGS. 1.1 to 1.3. The double arrows in FIG. 2 indicate the different adjustment directions of the print heads 12. They can then be adjusted both in the vertical direction and in the horizontal direction transversely to the transport direction 20 of the wood bar 1 through the printing machine 2. In addition, the print heads can be pivoted about an axis 15 parallel to the transport direction 20 of the wood bar 1. Due to the different possibilities, the respective print head 12 can be optimally adjusted to the position of the top side of the wood bar 1 to be printed or treated.The print heads 12 can be adjusted into a vertical position, so that it is possible, for example, if necessary to also treat or print on the vertical longitudinal sides 16, 17 of the wood bar 1, which in the exemplary embodiment run parallel to one another in the transport direction 20 of the wood bar 1.Due to the vertical adjustment possibility, the distance of the print heads 12 from the wood bars 1 to be printed can be adjusted. The adjustment of the position of the print heads 12 to the timber rod 1 can be effected automatically. Thus, for example, it is possible to provide sensors when the wood bar 1 enters the printing machine 2, which sensors detect the contour shape of the wood bar 1. The sensors send corresponding signals to a control system with which the print heads can be adjusted into the position necessary for printing on the wood bar. Instead of individual sensors, the cross-sectional shape of the wood bar 1 can also be captured by camera systems.However, the print heads 12 can also be adjusted manually into the required printing position.For adjusting the print heads 12, an electric motor is advantageously provided, which can bring the individual print heads exactly in position into the position required for printing or for treating the wood bar 1.A protective device (not shown) in the inlet region 19 (FIG. 1.1) of the printing press 2 prevents the wood bar 1 from being transported into the printing press 2 already when the print heads are not yet in their correct position.FIG. 3 shows the digital printing press 2 in schematic and perspective illustration. The wood bar 1 passes through the machine 2 in its longitudinal direction in the transport direction 20, and the described print heads for the different method steps 3 to 11, 21 are arranged in two rows. The lower or front row of print heads 3 to 11, 21 in FIG. 3 is assigned to the oblique top side 14 and the upper or rear row of print heads 3 to 11, 11, 21 is assigned to the horizontal top side 18 of the wood bar 1.Advantageously, the two rows of print heads are adjustable, as has been described with reference to FIG. 2. For this purpose, the print heads of each row can be arranged on a common carrier. The two carriers can be adjusted independently of each other. It is also possible to provide at least one, preferably all, print heads in at least one of the two rows in an adjustable manner.In contrast to FIG. 3, the two rows of print heads can be arranged in the printing press 2 in accordance with the embodiment according to FIG. 2 in such a way that, for example, two oblique longitudinal sides 13, 14 lying on different sides of the wood bar 1 can be treated, as has been explained with reference to FIG. 2.In principle, only one row of print heads can be provided for each of the various method steps 3 to 11, 21. This is the case in particular when the wood bars 1 passing through the machine 2 are to be treated and printed only on one side. In this case, too, it is advantageous if these print heads are adjustable relative to the wood bar 1, so that different positions on the wood bar can be treated and printed on wood bars 1 transported successively through the machine 2.It is also possible to use not only one, but two or more print heads for a single method step 3 to 11, 21. This is advantageous, for example, in order to achieve high coverage or in order to apply a plurality of layers.In order that the decoration can be applied to the wood rod 1 in a positionally accurate manner, it is ensured that the wood rod 1 is always positioned with respect to the print heads in such a way that the printed image is not adversely affected. In particular, the wood bar 1 is positioned or guided exactly transversely to the transport direction 20.The wood bar 1 is guided on a guide (not shown) during passage through the machine 2. This guide can consist of one or more rails which run through the machine 2 in the transport direction 20 and on which a carriage or also a plurality of carriages can be moved, on which the wood bar 1 is fixed. In order to ensure accurate positioning of the wood bar 1 on the carriage, the wood bar is first aligned transversely to its longitudinal direction, for example with the aid of a side stop or side guide extending in the transport direction 20. Once the wood bar 1 is thus aligned on the carriage, it is clamped in a known manner so as to reliably maintain its position on the carriage during the passage through the machine 2.After the last method step 11 in the machine 2, the wood bar 1 is released from being fixed on the carriage and the wood bar 1 is discharged from the printing machine 2 either manually or automatically.The carriage or carriages can (can) be driven by motor. For transporting the wood bar 1 through the machine 2, other drive means can also be used, such as a treadmill, a pushing device and the like.An exact positioning of the wood bar 1 during passage through the machine 2 can be dispensed with if the print heads can be adjusted in a controlled manner into their respective printing position. If the position of the upper sides to be printed on the wood bar 1 is detected by means of sensors or by means of camera systems before entering the machine 2, the position and orientation of the upper side to be printed on the wood bar 1 is known at least when entering the machine 2. The signals transmitted by the sensors or the camera systems of the controller are then used to position the print heads in accordance with the orientation of the top side.In such a particularly advantageous embodiment, it is even possible to adjust the print heads transversely to the transport direction 20 during the passage of the wood bar 1 through the machine 2 such that the desired printed image can be produced on the respective top side. It is thus possible to provide upper sides, which run curved in the transport direction 20, with exactly one decoration. The respective print head is tracked in accordance with the curvature running in the transport direction 20.In the same way, by controlling the print heads, it is possible to treat and print height differences exactly in the upper side of the wood bar 1 to be printed. The sensors or camera systems are designed such that they can also detect height differences in the top side of the wood bar 1 to be printed, so that the respective print heads can be adjusted accordingly in the height direction.Since the print heads can be adjusted both in the height direction and in the horizontal direction and also about the pivot axis 15 (FIG. 2 ), the print heads can always be aligned exactly with respect to the top side of the wood bar 1 to be printed.Relatively high feed speeds can be achieved with the machine 2, for example of about 40 m / min. A throughput of at least 15 running meters per minute can be achieved over the entire production time.With the machine 2, it is possible to print the wood bar 1 only on one side or also on several sides.As can be seen by way of example from FIG. 2, the two rows of print heads 12 shown there can be used not only to print on the obliquely lying upper sides 13, 14 but also to print on the horizontally lying upper side 18.In principle, it is also possible, for example, to use three rows of print heads for each method step 3 to 11, 21. Then three sides of the wood bar 1 can be printed, which are at an angle to each other.In the embodiment shown and described, two or more sides of the wood bar 1 are printed simultaneously. For this purpose, in the exemplary embodiment, corresponding print heads are at the same height, i.e. in principle next to one another, with respect to the transport direction 20. However, it is also possible to arrange the print heads for the individual workpiece sides one behind the other in the transport direction 20, so that the different sides of the wood bar 1 are printed one after the other in time.In an advantageous refinement, the print heads 3 to 11, 21 can be adjustable transversely to the transport direction 20 during the passage of the wood bar 1. It is then also possible to print or treat sides of the wood bar 1 which are wider than the working range of the print heads 3 to 11, 21. In principle, however, the individual print heads are designed such that they can print the complete width of the respective surface.Depending on the profile design of the wood bar 1, it is also possible to print two different sides of the wood bar 1 simultaneously using a print head. This is possible, for example, when the two sides are inclined only slightly with respect to one another.

Claims

Machine for applying at least one graphic to a wood rod (1) having a printing unit with at least one print head (12) for printing medium, such as ink, characterized in that at least one pretreatment unit is connected upstream of the printing unit within the machine (2) and / or at least one aftertreatment unit is connected downstream.Machine according to claim 1, characterized in that the pre-treatment unit comprises at least one print head (21) for applying a coating of the wood bar (1).Machine according to claim 1 or 2, characterised in that the pre-treatment unit comprises at least one drying device (5).Machine according to any one of claims 1 to 3, characterised in that the post-treatment unit comprises at least one device (10) for applying a covering layer to the printed graphic.Machine according to one of Claims 1 to 4, characterized in that the aftertreatment unit has at least one drying device (11).Machine according to one of Claims 1 to 5, characterized in that the printing unit for multicolor printing has a plurality of print heads (12) for different coloured printing inks.Machine according to one of claims 1 to 6, characterised in that the print heads (12) are adjustable relative to the timber rod (1).Machine according to claim 7, characterised in that the print heads (12) are adjustable in a controlled manner.Machine according to one of Claims 1 to 8, characterized in that the machine (2) has at least one transport device, by means of which the wood bar (1) can be transported through the machine (2).Method for applying at least one graphic to a wood bar (1), in particular with a machine according to one of Claims 1 to 9, characterized in that the wood bar (1) is pretreated or after-treated within the machine before and / or after the printing operation.Method according to claim 10, characterised in that the wood rod (1) is provided with a filler (3) and / or a primer (4) and / or a base coating (21) before the printing.Method according to claim 1 or 11, characterised in that the wood rod (1) is dried on its upper side (13, 14; 16 to 18) to be printed before the printing.Method according to one of Claims 10 to 12, characterized in that the wood rod (1) is dried after printing and / or is provided with a protective layer on the printed side.Method according to one of Claims 10 to 13, characterized in that the wood rod (1) is printed in a continuous process.Method according to one of Claims 10 to 14, characterized in that the wood bar (1) is transported at constant speed.Method according to one of Claims 10 to 15, characterized in that the contour shape of the wood bar (1) is detected by sensors and / or camera systems.Method according to Claim 16, characterized in that the signals of the sensors and / or camera systems are fed to a controller which adjusts the print heads (12) relative to the upper sides (13, 14); 16 to 18) to be printed on as a function of the signals.

Images