DE102022114231A1 - Method for sampling a workpiece - Google Patents

Abstract

The invention relates to a method for sampling a workpiece (2), which preferably consists at least in sections of wood, wood material or plastic, with the steps: providing a workpiece (2) and a coating material (4), attaching the coating material (4) to the Workpiece (2), in particular in the area of a narrow surface (2') of the workpiece (2), and printing the coating material (4) with a printing material by means of at least one printing unit (10, 20), which operates according to the drop-on-demand printing principle works, with the printing material having matt properties.

Description

Technical area

The invention relates to a method for sampling a workpiece, which preferably consists at least in sections of wood, wood material or plastic, and to a device for carrying out the method.

State of the art

In the furniture and component industry, workpieces, which are usually made of wood, wood-based materials, plastic or various composite materials, are usually coated and patterned on their surface. The pattern can either be present on the coating material in advance or can only be applied to the coating material after or in the course of the coating process.

For this purpose, various devices for printing workpieces are known. For example, this reveals EP 1 867 488 A a device for patterning the surface of workpieces, in which a printing unit prints a coating material while it is fed to a workpiece to be coated. The device includes a large number of conveyor and pressure rollers.

The workpieces are often decorated with natural patterns that imitate a wood or stone look.

There is a desire for such sampled workpieces to have an appearance that is as realistic as possible.

For this purpose, the EP 1 990 204 A a method and a device for influencing the degree of gloss of the patterned surface. However, it has been shown that such methods and devices involve a comparatively high level of effort, for example through additional components or additional process steps.

Presentation of the invention

The invention is based on the object of providing a method and a device for sampling a workpiece, which enable a natural or desired appearance of the workpiece to be sampled with little effort.

This object is achieved according to the invention by a method for sampling a workpiece according to claim 1 and by a device for carrying out the method according to claim 11. Particularly preferred developments of the invention are specified in the dependent claims.

By using a matt printing material according to the invention, a matt and therefore particularly natural appearance of the sampled workpiece can be achieved in a particularly simple and direct manner. This results in an overall matt appearance of the sampled workpiece, which most closely corresponds to the natural appearance of most natural materials such as wood or stone. In contrast, common printing processes that work according to the drop-on-demand printing principle have not yet enabled matt printing materials and therefore require complex additional measures that can be dispensed with thanks to the invention. The result is a method for patterning a workpiece, which in itself enables a matt and therefore natural appearance of the patterned workpiece and reduces the process effort.

The degree of dullness of the printing material can be suitably selected by the person skilled in the art within the scope of the invention. However, a particularly natural appearance of the sampled workpiece results if, according to a further development of the invention, the printing material, at least in the hardened or dried state with a substantially uniform layer thickness, has a gloss level according to ISO 2813 of at most 70 GU, preferably at most 50 GU, particularly preferably at most 30 GU having.

According to a further development of the invention, it is further provided that the printing material has ink and/or varnish, so that diverse and lasting optical effects can be achieved. The method according to the invention becomes particularly variable if the printing material is transparent, since it is then possible to work with several printing layers in order to finally produce the desired mattness using a matt and transparent printing material. In addition, transparent printing material can be produced particularly well as a matt printing material.

According to a further development of the invention, the printing material is cured after printing by means of a curing unit, preferably by irradiation such as in particular by UV radiation. On the one hand, this results in a high level of durability of the applied printing material, but on the other hand, the process flow can also be accelerated and successive process steps can be carried out in a quicker sequence. The use of radiation has proven to be particularly simple and effective, especially in the case of UV radiation.

Although the present invention enables a natural and matt appearance of the patterned workpiece through the selection of the printing material, additional measures can also be used within the scope of the invention which support the mattness of the patterned workpiece or increase the variability of the mattness. Against this background, according to a further development of the invention, it is provided that a first workpiece is irradiated with a first wavelength spectrum and/or intensity and a subsequent second workpiece is irradiated with a second wavelength spectrum and/or intensity, so that the printed area of the first workpiece has a different one Gloss level than the printed area of the second workpiece.

In addition, according to a further development of the invention, it is provided that excimer radiation is at least partially used during curing, which preferably has a wavelength in the range of 150 - 190 nm. By using excimer radiation, the (matt) level of gloss of the patterned surface can be additionally influenced in a targeted manner, which further increases the variability of the method according to the invention and allows the desired level of gloss to be set particularly precisely.

Furthermore, according to a further development of the invention, it is provided that the hardening of the printing material after printing takes place at least partially in an inert environment, in particular in a nitrogen environment. This means that curing can be carried out particularly quickly and homogeneously, especially when using excimer radiation. Thanks to the homogeneous curing, a particularly uniform appearance with a homogeneous matting results.

In order to be able to influence the level of gloss in an additional targeted manner, according to a further development of the invention it is provided that the surface of the printing material is provided with a topography after printing and/or during printing. This measure allows, among other things: create particularly matt surfaces. In addition, the surface can also have haptic properties.

It is particularly preferred that the topography is carried out by irradiation and/or mechanical processing of the surface of the printing material.

According to a further development of the invention, it is provided that the coating material is printed several times in succession with a printing material according to the drop-on-demand printing principle and that matt printing material is used in at least one printing process, in particular the last printing process. This process can create special visual effects and a particularly high-quality appearance. For example, the first printing process can be carried out with a particularly high-quality, highly pigmented and possibly glossy printing material in order to provide the desired colors with high intensity. Subsequently, for example, in a second or final printing process, matt and preferably transparent printing material can be used in order to give the previously applied printed image a matt appearance. The advantages of different printing concepts can thus be combined, with a first printing concept being able to bring in, for example, a particularly high resolution, color brilliance or the like, while the other printing process ultimately ensures the desired (matt) level of gloss.

A device for carrying out the method according to the invention is the subject of independent claim 11. By using this device, the advantages described above can be achieved particularly effectively.

According to a further development of the invention, the device has a curing unit for curing the printing material after printing, which preferably emits radiation, in particular UV radiation. The resulting advantages have already been described above.

Alternatively or additionally, according to a development of the invention, it is provided that the device has a joining device for attaching the coating material to the workpiece. This results in an integrated machine concept in which raw workpieces can be both coated and sampled on one machine, thereby reducing the number of devices required and increasing throughput. The coating material can be printed before, during and/or after the coating process using the joining device.

According to a further development of the invention, it is further provided that the device has at least two printing units which are set up to print the coating material one after the other, with at least the printing unit set up for the last printing process having access to matt printing material. This allows first achieve the advantages that were described above for carrying out several printing processes one after the other. In addition, the provision of several printing units enables even greater flexibility, since in addition to matt patterns, glossy patterns can also be carried out, for example by only working with one printing unit for glossy patterns, while the other printing unit, which works with matt printing material remains deactivated in this case.

Furthermore, according to a further development of the invention, it is provided that the device has a detection unit which is set up to detect at least the degree of gloss of the printed and preferably at least partially cured coating material. This allows the sampling result to be reliably checked, for example with regard to the level of gloss actually achieved, so that appropriate measures can be taken on this basis if necessary.

In this regard, according to a further development of the invention, it is provided that the device has a control device which is connected to the at least one printing unit and the detection unit and is set up to control the at least one printing unit on the basis of a detection result of the detection unit. This means that the printing process can be controlled or regulated particularly precisely, which means that particularly high-quality workpieces can be produced and waste can be minimized.

Brief description of the drawings

• 1 shows schematically a top view of a device for sampling a workpiece according to an embodiment of the invention.

Detailed description of preferred embodiments

Preferred embodiments of the invention are described in detail below with reference to 1 described, which schematically illustrates a device 1 for sampling a workpiece 2 in a top view.

The workpiece 2 can be plate-shaped or strip-shaped and consist, for example, of wood, wood-based material, plastic or other comparable materials. Such workpieces are widely used in the furniture and component industry, for example as body parts, furniture fronts, doors, etc.

As in 1 As can be seen, such workpieces 2 are often provided with a coating material 4, which can also consist of wood, wood material or plastic, but also of other suitable materials such as metal, etc. Such coating materials 4 are particularly common in the area of the narrow surface of the workpiece 2 is used and is then usually referred to as an edge. In the present embodiment, the device 1 is used to pattern the coating material 4, but is in principle also suitable for patterning various other surfaces of the workpiece 2.

In the present embodiment, the device 1 comprises two printing units 10, 20 for printing the coating material 4 with a printing material, which will be described in more detail below.

Furthermore, the device 1 comprises a conveyor unit 6, which transports the workpiece 2 and possibly subsequent workpieces 2 'in a flow direction (from right to left in 1 ) conveys along the print heads 10, 20. For this purpose, the conveyor device 6 can have, for example, conveyor troughs, conveyor chains and various other conveyor elements.

Although in 1 not shown, the conveyor device 6 can also serve to guide the printing units 10, 20 and possibly other units along a stationary workpiece 2. For this purpose, the printing units 10, 20 and optionally further units can be arranged on a support which can be moved in the plane of the workpiece 2 and rotated about an axis running perpendicular to the plane of the workpiece. Mixed forms of both concepts are also possible within the scope of the invention.

The printing units 10, 20 each have a print head 12, 22. These work according to the drop-on-demand printing principle, in which individual drops of printing material can be ejected as needed. For example, piezo print heads, thermal print heads or other suitable print heads can be used for this purpose.

Furthermore, the printing units 10, 20 each have a printing material supply 14, 24, in which suitable printing material is stored and is fed to the print heads 12 and 22, respectively. At least the supply 24 of the second printing unit 20 contains a printing material that has matt properties. The supply 14 of the first printing unit 10 can also contain corresponding printing material or other types of printing material, possibly glossy. Furthermore, it should be noted that the respective supply 14 or 24 can also contain several similar or different printing materials, for example different colors such as preferably cyan, magenta, yellow and black or also transparent printing materials. Furthermore, the printing materials can be, for example, inks, varnishes and various other printing materials that can have different colors and can be both transparent and opaque. In any case, the printing material stored in the second print supply is preferably matt and transparent.

In the present embodiment, in the cured or dried state with a substantially uniform layer thickness, the matt printing material has a gloss level according to ISO 2813 of at most 70 GU, although, depending on the application, significantly lower gloss levels of, for example, at most 50 GU up to values of less than 30 GU are also useful could be. The uniform layer thickness for determining the level of gloss inherent in the printing material can be achieved, for example, by applying the printing material to a substrate using a squeegee, then completely or partially curing or drying it and determining the level of gloss according to ISO 2813. Alternatively, the uniform layer thickness can also be achieved by setting the printing process to be as uniform as possible and then carrying out a measurement according to ISO 2813 and determining the level of gloss. The matt printing material is therefore a material that has a low gloss level of, for example, a maximum of 70 GU according to ISO 2813, even without additional measures - such as roughening, targeted topography or the like.

In order to achieve this material property of the printing material, the printing material can, for example, have particles that are as large as possible, which lead to a matt material property of the printing material due to their reduced reflection behavior compared to small particles. At the same time, the particles should not become too large so that the printing material can continue to be processed using the drop-on-demand printing process, which is usually based on a small droplet size and small nozzle outlet openings.

Furthermore, the device 1 in the present embodiment comprises a curing unit 30 for curing the printing material after printing, which in the present embodiment has one or more UV emitters. The curing device 30 and the adjacent area in which the curing process takes place may be shielded by an enclosure 32 within which a nitrogen environment or other suitable inert environment prevails. The residual oxygen content in the inert environment can, for example, be at most 1%, preferably at most 0.5%.

The hardening of the printing material applied by the printing units 10, 20 can be done by simple irradiation with UV radiation. If necessary, the curing unit 30 can also be operated with different wavelengths or wavelength spectra and, if necessary, with different intensities, so that the gloss level of the printed area of successive workpieces 2, 2 'can be specifically influenced by different operating parameters of the curing unit 30.

Alternatively or additionally, the curing unit 30 can also be set up to allow various other radiations to act on the printing material. For example, excimer radiation can also be used, which can have a wavelength of 172 nm, for example. For example, the excimer radiation can be used to harden a surface layer of the applied printing material and, in the subsequent step, to harden the entire printing material using UV light. This measure results in a different deformation behavior in the surface layer than in the underlying layers, which leads to a topography in the top layer and thus to a reduced level of gloss. In this way, the (matt) gloss level of the applied printing material can be further reduced and influenced in a targeted manner.

Within the scope of the invention, other measures for influencing the level of gloss or for achieving a topography of the applied printing material are also possible, for example other types of irradiation, mechanical action or even targeted operation of the printing units 10 or 20 in such a way that a topography is established. Such settings are particularly useful when particularly low levels of gloss are desired.

As in 1 As can be seen, the device 1 in the present embodiment further comprises a joining device 40 for attaching the coating material 4 to the workpiece 2. However, it should be noted that the joining device 40 is optional and can also be provided in a separate device, for example. In the present embodiment, the joining device 40 includes a pressure roller 42 and an energy source 44, such as a hot air source, a laser, an infrared source, a microwave source, a plasma source or the like. The energy source 44 can serve to provide the energy to activate (make adhesive) the side of the coating material 4 facing source 44. For this purpose, the coating material 4 can be pre-coated with a corresponding adhesive or consist of a suitable material that develops adhesive properties when energy is applied.

Alternatively or additionally, the joining device 40 can also have an adhesive application roller 46, by means of which an adhesive such as hot melt can be applied to the side of the coating material 4 facing the workpiece 2'. The energy source 44 can then either be passive or used to keep the applied adhesive activated or further activated. The pressure roller then serves to press the coating material 4 supplied with an activated adhesive onto the workpiece 2' and thus attach it.

Furthermore, the device 1 in the present embodiment also includes a detection unit 50 for detecting the degree of gloss of the printed and at least partially cured coating material 4. The detection unit 50 can be, for example, a camera or a sensor that is suitable for parameters such as To record the degree of gloss, the color spectrum, etc. of the printed coating material 4.

The detection unit 50 is connected to a control device 60, for example a machine control, which in turn can also be connected to the conveying unit 6, the printing units 10, 20 and the curing unit 30. In this way, the control device 60 is enabled to control the printing units 10, 20 based on a detection result of the detection unit 50. This makes it possible not only to record the actual gloss levels or color spectra of the sampled coating material 4, but also to act on at least one of the printing units 10, 20 and/or the curing unit 20 in the event of target/actual deviations. If necessary, other machine parameters can also be corrected, such as the conveying speed of the conveying unit 6.

Overall, a workpiece 2 can therefore be conveyed into the device according to the invention by means of the conveyor unit 6 and provided with a coating material 4 in the area of the joining unit 40. The workpiece 2 then reaches the printing units 10, 20 and is patterned there in the area of the coating material 4 with one or more printing materials, with at least the second (last) printing unit 20 outputting a matt and preferably transparent printing material. The applied printing material is then cured or dried in the area of the curing unit 30, whereupon, for example, the level of gloss of the applied printing material is recorded by means of the detection unit 50. The detection result of the detection unit 50 is passed on to the control unit 60, which controls the further operation of the device 1 on this basis.

In a next step, a subsequent workpiece 2' basically goes through the same process, whereby other parameters can be used as required in order to give the subsequent workpiece 2' the desired pattern. For example, other printing materials can be used, or if necessary, only the first printing unit 10 can be used, so that glossy patterns can also be applied if necessary. Furthermore, the curing unit can also work with different operating parameters in order to bring about different properties, in particular levels of gloss, for different workpieces and, if necessary, within individual workpieces.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1867488 A [0003]
• EP 1990204 A [0006]

Claims (16)

Method for sampling a workpiece (2), which preferably consists at least in sections of wood, wood material or plastic, with the steps: providing a workpiece (2) and a coating material (4), attaching the coating material (4) to the workpiece (2) , in particular in the area of a narrow surface (2 ') of the workpiece (2), and printing the coating material (4) with a printing material by means of at least one printing unit (10, 20), which works according to the drop-on-demand printing principle that the printing material has matt properties. Procedure according to Claim 1 , in which the printing material, at least in the hardened or dried state with a substantially uniform layer thickness, has a gloss level according to ISO 2813 of at most 70 GU, preferably at most 50 GU, particularly preferably at most 30 GU. Procedure according to Claim 1 or 2 , in which the printing material has ink and / or varnish and is preferably transparent. Method according to one of the preceding claims, in which the printing material is hardened after printing by means of a curing unit (30), preferably by irradiation, in particular by UV radiation. Procedure according to Claim 4 , in which a first workpiece (2) is irradiated with a first wavelength spectrum and/or intensity and a subsequent second workpiece (2') is irradiated with a second wavelength spectrum and/or intensity, so that the printed area of the first workpiece (2) has a different level of gloss than the printed area of the second workpiece (2'). Procedure according to Claim 4 or 5 , in which excimer radiation is at least partially used during curing, which preferably has a wavelength in the range from 150 to 190 nm. Procedure according to one of the Claims 4 until 6 , in which the curing of the printing material after printing takes place at least partially in an inert environment, in particular in a nitrogen environment. Method according to one of the preceding claims, in which the surface of the printing material is provided with a topography in order to reduce its level of gloss and/or to influence the feel. Procedure according to Claim 8 , in which the topography is achieved by irradiation and/or mechanical processing of the surface of the printing material. Method according to one of the preceding claims, in which the coating material (4) is printed several times in succession with a printing material according to the drop-on-demand printing principle and matt printing material is used in at least one printing process, in particular the last printing process. Device (1) for carrying out the method according to one of the preceding claims, which has: at least one printing unit (10, 20) for printing the coating material (4) with a printing material, which works according to the drop-on-demand printing principle, a conveyor unit (6) for bringing about a relative movement between the at least one printing unit (2) and the coating material (4), characterized in that at least one printing unit (20) has a supply (24) of printing material which is used by the printing unit (20) for printing can be used and has matt properties. Device according to Claim 11 , in which a curing unit (30) is provided for curing the printing material after printing, which preferably emits radiation, in particular UV radiation. Device according to Claim 11 or 12 , in which a joining device (40) is provided for attaching the coating material (4) to the workpiece (2). Device according to one of the Claims 11 until 13 , in which at least two printing units (10, 20) are provided, which are set up to print the coating material (4) one after the other, at least the printing unit (20) set up for the last printing process having access to matt printing material. Device according to one of the Claims 11 until 14 , in which a detection unit (50) is provided which is set up to detect at least the level of gloss of the printed and preferably at least partially cured coating material (4). Device according to one of the Claims 11 until 15 , in which a control device (60) is provided hen, which is connected to the at least one printing unit (10, 20) and the detection unit (50) and is set up to control the at least one printing unit (10, 20) based on a detection result of the detection unit (50).

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