Sheet material processing unit and method for evaluating alignment

Abstract

A sheet material processing unit (10) is described. It includes an upper tool (18) and a lower tool (14), wherein the upper tool (18) and the lower tool (14) are configured to interact with each other to process sheet material (26). Furthermore, a camera unit (40) is provided, arranged such that it can simultaneously capture a portion of the upper tool (18) including a first opening (28) and a portion of the lower tool (14) located behind the first opening (28) to align the tools (14, 18). The sheet material processing unit (10) further includes a first set of light sources and a second set of light sources, which are different from each other and configured to illuminate the portion to be captured sequentially. Furthermore, a method for evaluating the alignment of the upper tool (18) relative to the lower tool (14) and relative to the sheet material (26) is proposed.

Description

Technical Field

[0001] This invention relates to a sheet material processing unit, particularly for processing paper, cardboard, or plastic sheets for packaging. The sheet material processing unit includes a frame, an upper tool, and a lower tool, wherein the upper and lower tools are configured to interact with each other to process the sheet material. The upper and lower tools are mounted on the frame via respective upper and lower alignment units for aligning the upper and lower tools relative to each other and relative to the sheet material to be processed. The upper tool includes a first opening. Furthermore, a camera unit is arranged such that it can simultaneously capture a portion of the upper tool including the first opening and a portion of the lower tool located behind the first opening for aligning the upper and lower tools.

[0002] The present invention also relates to a method for evaluating the alignment of the upper and lower tools of a sheet material processing unit as described above with respect to each other.

[0003] Furthermore, the present invention relates to a method for evaluating the alignment of an upper tool of a sheet material processing unit of the type described above with respect to the sheet material disposed therein. Background Technology

[0004] Such sheet material processing units and corresponding methods are known. In this document, a sheet material processing unit may also be referred to as a sheet material processing station. Exemplary sheet material processing units or stations are stripping stations for removing waste from cut sheet material or unloading stations for removing corresponding blanks from cut sheet material.

[0005] To reliably deliver products of the desired quality, the upper and lower tools need to be aligned relative to each other. This alignment ensures that the upper and lower tools interact in the desired manner. Therefore, the relevant configuration of the alignment is when the upper and lower tools interact or engage. The alignment of the upper and lower tools relative to each other also avoids undesirable wear on these tools.

[0006] In addition, these tools, namely the upper and lower tools, need to be aligned relative to the sheet material to be processed in order to accurately process the sheet material.

[0007] This alignment is performed by an upper alignment unit connected to the upper tool and a lower alignment unit connected to the lower tool. The two alignment units are configured to adjust the position of the respective tools within a machining plane, which substantially corresponds to the plane on which the sheet material lies during machining. Sometimes this adjustment is specified as adjustment in both the X and Y directions. Furthermore, the alignment units are configured to align the rotational direction of the respective tools, meaning the tools can rotate around the Z direction at predetermined intervals. The Z direction is perpendicular to both the X and Y directions. The Z direction is also perpendicular to the machining plane. Such alignment units are known.

[0008] Clearly, alignment is required before sheet material processing begins. This means that alignment is necessary at least when one of the tools is changed and / or before a new job begins. Of course, so-called intermediate alignment is also possible, which is alignment unrelated to tool changes or job changes.

[0009] The first opening is located on the upper tool. It should be understood that the lower tool, located behind the first opening, can only be captured by the camera unit when sheet material is being removed from the sheet material processing unit. This configuration is suitable for aligning the upper and lower tools relative to each other. If sheet material is present in the sheet material processing unit (i.e., between the upper and lower tools), the camera unit can only capture images of the upper tool and the sheet material. This configuration is necessary for aligning the tools relative to the sheet material to be processed.

[0010] Since alignment is based on images captured by a camera unit, alignment accuracy depends on image quality. Image quality relates to the suitability of the image used to accurately evaluate the alignment. Image quality includes sharpness, resolution, and the visibility of alignment marks and / or edges. Image quality depends to some extent on the optical properties of the tool surface and / or the surface of the sheet material being aligned. Summary of the Invention

[0011] Therefore, the objective of this invention is to generally improve alignment accuracy by enhancing image quality, particularly by reducing dependence on the optical properties of the surfaces involved in the captured image.

[0012] Another objective of this invention is to improve the stability and repeatability of the image process, thereby improving the repeatability of alignment evaluation.

[0013] This problem is solved by a sheet material processing unit of the type described above, which includes a first set of light sources and a second set of light sources. The first set of light sources includes at least one light source for illuminating the portion to be captured, and the second set of light sources includes at least one light source for illuminating the portion to be captured. The first and second sets of light sources are different from each other and are configured to illuminate the portion to be captured sequentially. The light sources are, for example, LEDs (light-emitting diodes). By illuminating the upper tool, lower tool, and / or the portion of the sheet material to be captured, the quality of the corresponding image is improved. Furthermore, at least in terms of illumination, it is achieved that the image is unaffected by environmental conditions. Therefore, high-precision alignment can be achieved. When the portion to be captured is illuminated sequentially using two different sets of light sources, i.e., first illuminating the portion using only the first set of light sources and then illuminating the portion using only the second set of light sources, the image quality can be further enhanced. This is especially true when images are captured under each of the above-described illumination conditions and the information contained in the two images is combined. Doing so can compensate for, for example, undesirable reflections from very glossy surfaces. At a given location, such reflections may only occur under one illumination condition. Therefore, features of the captured image that are otherwise undetectable can be detected from the combination of at least two images. Thus, the accuracy of alignment is further improved.

[0014] Preferably, the first and second groups of light sources do not intersect (or are equivalent to being separate), that is, they do not have any common light source.

[0015] The basic idea of ​​this invention can be summarized as replacing a single image captured under given lighting conditions with at least two images captured under different, specially created lighting conditions. Information contained in the at least two images is then combined. Different lighting conditions, in particular, result in different distributions of light and shadow in the at least two images. By combining these images, the effects of undesirable reflections or deflections are compensated for.

[0016] Of course, in other variations, more than two different (or non-overlapping) light sources can be used, such as four sets of light sources. Each set of light sources is used to create specific lighting conditions, and an image is captured under each lighting condition. The information contained in the images is then combined.

[0017] In this paper, the camera unit is understood as a system for capturing images. Therefore, the camera unit may also include additional optical components, such as lenses or mirrors. The mirror is particularly suitable for tilting the optical axis so that the camera unit can be installed in a limited space.

[0018] In a preferred embodiment, these light sources are arranged on the camera unit. Therefore, the camera unit and these light sources form a structural unit that is compact and can be easily installed within the sheet material processing unit.

[0019] Preferably, both the upper and lower tools are replaceable, meaning they can be replaced with other tools used for other tasks. Therefore, the sheet material processing unit can be used to perform a variety of tasks.

[0020] Preferably, a first mark is provided on the portion of the lower tool located behind the first opening. The first mark is preferably implemented as a feature on the surface of the lower tool that can be easily detected by the camera unit. This allows for quick and accurate alignment because alignment relies on the mark rather than less prominent surface features.

[0021] The camera unit is movably supported on the frame via a linear drive unit, allowing it to be moved along the width of the upper tool. This width corresponds to the lateral direction of the sheet material processing unit, i.e., the direction perpendicular to the movement direction of the sheet material to be processed. Therefore, the camera can be moved to a suitable position to capture an image for alignment. Consequently, image quality and alignment accuracy are improved. This movably supported camera unit also gives the sheet material processing unit flexibility relative to the different tools used within it. Different types of tools can provide corresponding initial openings at different locations. The camera unit can always be moved to a position where high-quality images can be captured.

[0022] According to one embodiment, a second opening is provided on an upper tool including a first opening. A camera unit can be moved by a linear drive unit, enabling it to simultaneously capture a portion of the upper tool including the second opening and a portion of a lower tool located behind the second opening. Therefore, the upper tool includes two openings, namely the first opening and the second opening. To align the upper and lower tools relative to each other, and to align the upper tool relative to the sheet material to be processed, the camera unit can capture images at two positions corresponding to the first and second openings, respectively. This results in improved alignment accuracy. In particular, capturing images at both positions allows the upper and lower tools to be pivotally aligned relative to each other or relative to the sheet material to be processed, for example, by rotation about the Z direction. When only an image captured at one position is used, only the positions along the X and Y directions can be measured. In this case, it can only be assumed that there is no pivot misalignment.

[0023] A second mark can also be provided on the portion of the lower tool located behind the second opening. Furthermore, the second mark is preferably implemented as a feature on the surface of the lower tool that can be easily detected by the camera unit. This allows for quick and accurate alignment because alignment relies on the mark rather than less prominent surface features.

[0024] As previously mentioned, the alignment of the upper and lower tools relative to each other is crucial when the upper and lower tools interact or engage. However, during job changes, the upper and lower tools must be aligned before use (i.e., before interaction or engagement). According to one aspect of the invention, a calibration method using calibration marks is provided. This calibration allows the position of the upper tool relative to the lower tool when the upper and lower tools are engaged to be calculated from the position of the upper tool relative to the lower tool when the upper tool is separated. In other words, this calibration can predict the position of the upper tool when it is in its lower engaged position from its position when it is in its upper separated position. This calibration method is performed during the machine setup phase.

[0025] In the absence of calibration data, it is assumed that the positions of the upper tool along the X and Y directions measured at the upper part separation position are equal to the X and Y positions of the upper tool at the lower part engagement position.

[0026] In one variant, the calibration marks are located on the upper tool or on a corresponding tool holder connected to the upper tool. The calibration marks can be detected by the camera unit, particularly where the surface of the calibration marks is made of a material that reflects light diffusely. In other variants, multiple calibration marks are used, for example, four calibration marks distributed on the upper tool. Materials that reflect light diffusely produce less interfering reflections than other materials. Therefore, the quality of the image captured by the camera unit is improved.

[0027] The calibration mark is associated with a movable upper tool used for processing sheet materials.

[0028] Because of the calibration mark, alignment of the upper and lower tools at their engagement position can be achieved by capturing corresponding images of the upper and lower tools in their separated positions. The upper tool is in the upper position when separated and in the lower position when engaged. To do this, the upper and lower tools are first moved to interact or engage, and an image of the calibration mark is captured. Then, the upper and lower tools are moved to the position used for calibration, and an image of the calibration mark is captured again. By analyzing the two images of the calibration mark, the coordinates of the engagement position of the tools can be accurately determined relative to the position of the tools being aligned there. These coordinates, or more generally, the calibration results, can be used for alignment. Therefore, the calibration mark has high alignment accuracy.

[0029] According to one variant, calibration uses a first calibration image and a second calibration image, in which the upper tool is located at its upper position in the first calibration image and at its middle position in the second calibration image. The upper position of the upper tool corresponds to the position used for the alignment method. The middle position is lower than the upper position but still higher than the engagement position. By using the corresponding heights (i.e., Z positions) of the upper, middle, and lower positions combined with the XY positions of the upper tool at its upper position, the X and Y coordinates of the upper tool at the engagement position can be extrapolated from the X and Y positions of the upper tool at the middle position. To ensure sufficient accuracy, the (vertical) travel of the upper tool between the upper and middle positions should be at least 30%, preferably 80%, of the total travel between the upper and lower positions.

[0030] Calibration markers can comprise multiple marker elements arranged in a predefined layout. Marker elements are, for example, points or other relatively simple geometric elements. For instance, they are arranged in a rectangular array with a known grid size. In a preferred example, 36 marker elements are arranged in a 6x6 square array. For such calibration markers, their position in three-dimensional space is easily detected by the camera unit. If the position of the camera unit is known, the position of the calibration markers in the detection plane can be deduced from their position in the image. By analyzing the deviation of the grid size in the image from the known grid size, the position of the calibration markers along the Z direction perpendicular to the detection plane can be derived. In other words, the scaling factor or scale of the markers is analyzed. Therefore, calibration markers allow for precise detection of the position of the relevant tool.

[0031] A cap can be provided for selectively covering and removing the calibration marks. This prevents the marks from being covered by dust or other unwanted particles. By keeping the marks as clean as possible, the accuracy and speed of detection can be maintained at a high level.

[0032] The upper tool includes at least one calibration mark, but preferably multiple calibration marks.

[0033] Advantageously, the upper tool is connected to the vertical drive unit, while the lower tool is essentially fixed within the frame, allowing the upper tool to move vertically relative to the lower tool for processing sheet material. This tool configuration has proven highly suitable for processing sheet material. In this paper, the fact that the lower tool is fixed pertains to the operational state of the sheet material processing unit. This means that the fixed tool remains movable for alignment purposes.

[0034] According to a preferred embodiment, the first group of light sources consists of a single light source, and the second group of light sources also consists of a single light source. This group of light sources has a simple and robust structure.

[0035] Furthermore, this problem is solved by a method for evaluating the alignment of the upper and lower tools of the sheet material processing unit according to the present invention relative to each other, the method comprising the following steps:

[0036] a) Position the camera unit so that it can simultaneously capture a portion of the upper tool including the first opening and a portion of the lower tool located behind the first opening;

[0037] b) Activate a first group of light sources, including at least one light source, while deactivating the remaining groups of light sources, and capture a first image including a portion of an upper tool with a first opening and a portion of a lower tool located behind the first opening and including a first mark.

[0038] c) Activate a second group of light sources, including at least one light source, while deactivating the remaining groups of light sources, and capture a second image including a portion of the upper tool with the first opening and a portion of the lower tool located behind the first opening and including the first mark.

[0039] d) Determine the positions of at least two edges of the first opening by combining analysis of the first and second images, and deduce the position of the upper tool including the first opening from the positions of the at least two edges.

[0040] e) Determine the position of the first marker by combining analysis of the first and second images, and deduce the position of the lower tool including the first marker from the position of the first marker.

[0041] f) Calculate the positional offset between the upper tool and the lower tool.

[0042] It is understood that this method is performed when there is no sheet material in the sheet material processing unit (especially between the upper and lower tools). The activation of the first and second sets of light sources produces different illumination conditions. Certain features of the portion to be captured are better visible or detectable under one illumination condition than under another. Therefore, the positions of at least two edges and the position of the first mark can be identified with high accuracy and reliability. Therefore, the positions of the upper and lower tools can also be derived with high accuracy and reliability. Therefore, the positional offset, as a quality indicator of alignment, can be determined with high precision. This positional offset can be used to determine whether one of the tools should be moved to improve alignment. Since alignment defines the relative orientation of the upper and lower tools relative to each other, it is technically sufficient for one of the tools to be equipped with an alignment unit. However, as will be explained later, it is preferable that both tools are equipped with alignment units. This method is performed each time a tool is changed, when the tool set is stationary. Doing so ensures the correct alignment of the upper and lower tools relative to each other. This method can be performed in a fully automated manner. Subsequent alignment of these tools can also be fully automated.

[0043] Furthermore, this problem is solved by a method for evaluating the alignment of an upper tool of a sheet material processing unit according to the invention with respect to a sheet material disposed therein, the method comprising the following steps:

[0044] a) Position the camera unit so that it can simultaneously capture a portion of the upper tool including the first opening and a portion of the sheet material located behind the first opening.

[0045] b) Activate a first group of light sources, including at least one light source, while deactivating the remaining groups of light sources, and capture a first image including a portion of the upper tool with a first opening and a portion of the sheet material located behind the first opening and including sheet markings.

[0046] c) Activate a second group of light sources, including at least one light source, while deactivating the remaining groups of light sources, and capture a second image including a portion of the upper tool with the first opening and a portion of the sheet material located behind the first opening and including sheet markings.

[0047] d) Determine the positions of at least two edges of the first opening by combining analysis of the first and second images, and deduce the position of the upper tool including the first opening from the positions of the at least two edges.

[0048] e) Determine the location of the sheet markings by combining the analysis of the first and second images, and deduce the location of the sheet material from the location of the sheet markings.

[0049] f) Calculate the positional offset between the position of the upper tool including the first opening and the position of the sheet material.

[0050] It is understood that this method can only be performed when the sheet material is present in the sheet material processing unit. The sheet markings can be cut, stamped, or printed. Preferably, the sheet markings are cut. Activation of the first and second sets of light sources creates different illumination conditions. Some features of the portion to be captured are better visible or detectable under one illumination condition than under another. Therefore, the positions of at least two edges and the sheet markings can be identified with high accuracy and reliability. Consequently, the position of the upper tool can also be derived with high accuracy and reliability. This also applies to the position of the sheet material. Therefore, the positional offset, a quality indicator of alignment, can be determined with high precision. This positional offset can be used to determine whether the tool should be moved relative to the sheet material to improve alignment. For this purpose, both the upper and lower tools are equipped with their own alignment units, which are adapted to move the tools relative to the sheet material without requiring the tools to move relative to each other. This method is performed each time a tool is changed, when the tool set is stationary. This ensures correct alignment of the upper and lower tools relative to the sheet material. This method can be performed in a fully automated manner. Subsequent tool alignment can also be fully automated.

[0051] When the edge of the first opening is straight, the advantage of identifying the positions of at least two edges is that it allows determination of the positions along the X and Y directions. The same result, i.e., the positions along the X and Y directions, can be achieved by identifying a single curved edge. Therefore, in the sense of this application, the two portions of a curved edge are considered as two edges.

[0052] Both methods can be performed when the upper tool is in its upper separated position, wherein the calibration results are used to calculate the alignment of the upper tool with respect to its lower engagement position. As already described for the sheet material processing unit according to the invention, the calibration results essentially include the coordinates of the lower position of the upper tool relative to its upper position. In other words, the calibration results include the spatial difference or vector between the upper and lower positions. Therefore, the alignment associated with the lower position can be readily derived from the alignment evaluated in the upper position using the calibration results. In particular, the calibration results are generated by employing the following method steps.

[0053] Preferably, in the active state, a first set of light sources, including at least one light source, and / or a second set of light sources, including at least one light source, illuminate the upper tool and the lower tool or sheet material, causing at least one edge of the first opening to be projected onto the portion located below the first opening. Therefore, the edge can be detected with high precision. This is because the shadow generated directly adjacent to the edge appears as a dark area in the captured image, while the portion adjacent to the edge of the corresponding tool including the first opening appears as a bright area in the captured image. Alternatively, the illumination can also be configured such that both edges project onto the portion located below the first opening. Such edges are preferably adjacent edges. In both alternatives, the position of the edge and therefore the corresponding tool can be detected with high precision.

[0054] In one variation, a second opening is provided on the upper tool including the first opening, and the method is performed when the imaging unit is positioned such that it can simultaneously capture a portion of the upper tool including the second opening and a portion located behind the second opening. Preferably, in conjunction with such a second opening, a second mark is provided on the portion of the lower tool located behind the second opening and / or a further sheet mark is provided on the sheet material located behind the second opening. The second opening provides substantially the same effects and advantages as described in conjunction with the first opening. However, the accuracy of detection can be further improved when the first and second openings are used to evaluate the alignment of the upper and lower tools relative to each other or to evaluate the alignment of the upper tool relative to the sheet material. In other words, when using the first and second openings, the alignment is evaluated at two different locations.

[0055] The sheet material processing unit according to the invention can be calibrated, particularly before performing step a), the calibration comprising the following steps:

[0056] a) Move the upper tool to its upper position and capture the calibration marks associated with the upper tool using the camera unit, wherein the calibration marks include multiple mark elements arranged according to a predefined layout.

[0057] b) Calculate the first position of the calibration mark in the horizontal plane associated with the upper position of the upper tool.

[0058] c) Move the upper tool to its central position and capture the calibration marks associated with the upper tool using the camera unit.

[0059] d) Calculate the second position of the calibration mark in the horizontal plane associated with the intermediate position of the upper tool, and

[0060] e) Calculate the calibration result including the vector connecting the first and second positions.

[0061] The calculation of the position of the upper tool associated with the calibration mark has been explained in detail using the sheet material processing unit according to the invention. Therefore, the position of the calibration mark can be detected in three-dimensional space. The effects and advantages mentioned in the sheet material processing unit also apply to the method steps used for calibration.

[0062] Based on this, the angle by which the actual direction of motion of the upper tool deviates from the optical axis of the camera between the middle and upper positions can also be calculated. As previously explained, when images of the calibration marks are captured at the upper and middle positions, the spatial difference, or vector, between these positions can be calculated. This spatial difference can also be referred to as the calibration result. If the upper position of the upper tool is known, this calibration result can be used to predict the lower position of the upper tool.

[0063] After the sheet material processing unit has been installed, calibration can be performed. Preferably, calibration should also be performed frequently (e.g., periodically) as needed to ensure the stable operation of the sheet material processing unit.

[0064] Preferably, calibration is performed at multiple locations on the camera unit, with a calibration mark set at each location. For example, calibration uses four, six, or nine calibration marks and is performed at four, six, or nine corresponding locations. This further improves the accuracy of the calibration. Attached Figure Description

[0065] Advantageously, the middle position of the upper tool is the lower position of the upper tool. In other words, the middle position corresponds to the position where the upper and lower tools are engaged. The invention will now be described with reference to the accompanying drawings. In the drawings,

[0066] - Figure 1 A partial cross-sectional side view of a sheet material processing unit according to the invention is schematically shown, wherein the upper tool is indicated in an upper position, wherein the sheet material is arranged within the sheet material processing unit, and wherein the upper tool is projected onto the sheet material.

[0067] - Figure 2 A partial cross-sectional side view of a sheet material processing unit according to the invention is schematically shown, wherein its upper tool carries calibration marks, and the angle between the actual directions of movement of the upper tool at its lower and upper positions is indistinguishable from the optical axis of the camera unit.

[0068] - Figure 3 schematically shown Figure 2 In the sheet material processing unit, for illustrative purposes, the misalignment between the actual movement direction Z' between the lower and upper positions of the upper tool and the optical axis of the camera unit is exaggerated.

[0069] - Figure 4A schematic top view is shown. Figure 1 The sheet material processing unit, in which the sheet material has been removed.

[0070] - Figure 5 Shown in a separate representation Figures 1 to 4 Calibration marks of the sheet material processing unit

[0071] - Figure 6 It is shown under the first lighting conditions Figures 1 to 4 A portion of the upper tool and a portion of the lower tool of the sheet material processing unit.

[0072] - Figure 7 It is shown under the second lighting conditions Figures 1 to 4 A portion of the upper tool and a portion of the lower tool of the sheet material processing unit.

[0073] - Figure 8 It shows the third lighting condition Figures 1 to 4 A portion of the upper tool and a portion of the lower tool of the sheet material processing unit.

[0074] - Figure 9 It shows the fourth lighting condition Figures 1 to 4 A portion of the upper tool and a portion of the lower tool of the sheet material processing unit.

[0075] - Figure 10 It shows Figures 1 to 4 An image showing a combination of a portion of the upper tool and a portion of the lower tool of a sheet material processing unit, wherein first to fourth lighting conditions have been combined.

[0076] - Figure 11 A portion of the upper tool and a portion of the lower tool of a sheet material processing unit according to an alternative embodiment are shown. Detailed Implementation

[0077] Figures 1 to 4 A sheet material processing unit 10 is shown, which in this embodiment is a peeling station for cardboard sheets.

[0078] The sheet material processing unit 10 includes a frame 12.

[0079] The lower tool 14 is mounted on the frame via the lower alignment unit 16.

[0080] Except for possible movement caused by the alignment unit 16, the lower tool 14 is fixed within the frame 12.

[0081] In addition, the upper tool 18 is mounted on the frame 12 via the upper alignment unit 20.

[0082] The upper tool 18 is further connected to the vertical drive unit 22, such that the upper tool 18 is movable relative to the lower tool 14 in the vertical direction 24 for processing the exemplary sheet material 26 placed on the lower tool 14 (see Figure 1 ).

[0083] exist Figure 2 and Figure 3 In the diagram, the upper tool 18 and related components are indicated in upper and lower positions. To distinguish between these two positions, components located in the upper position are indicated by the suffix "u", and components located in the lower position are indicated by the suffix "l".

[0084] The upper tool 18 and the lower tool 14 are configured to interact with each other to process the sheet material 26, in this embodiment to perform a peeling operation. Since peeling itself is well known in the art, a detailed description will be omitted.

[0085] The upper tool 18 and the lower tool 14 can be aligned relative to each other and relative to the sheet material 26. For this purpose, alignment units 16 and 20 can be used, which allow the respective tools 14 and 18 to move in the X and Y directions within predefined intervals. In addition, alignment units 16 and 20 allow the respective tools 14 and 18 to rotate about the Z direction.

[0086] In addition, the upper tool 18 includes a first opening 28 having a basic rectangular shape (see Figure 4 ).

[0087] Furthermore, a second opening 30 is provided on the upper tool 18. The second opening 30 also has a basically rectangular shape, substantially the same as the first opening 28. However, the second opening 30 is moved relative to the first opening 28 in the Y direction (see...). Figure 4 ).

[0088] When positioned above the upper tool 18, the lower tool 14 can be seen through the first opening 28 and the second opening 30.

[0089] A first mark 32 is provided on a portion of the lower tool 14 located behind the first opening 28.

[0090] A second mark 34 is provided on a portion of the lower tool 14 located behind the second opening 30.

[0091] Both the first mark 32 and the second mark 34 are optically detectable marks.

[0092] In the illustrated embodiment, the first mark 32 and the second mark 34 are formed in a cross shape.

[0093] The calibration mark 36 is substantially square and comprises multiple mark elements 38 arranged in a predefined layout. In the illustrated embodiment, the calibration mark 36 comprises nine mark elements 38 arranged in a square array according to a constant grid size. For better readability, only some mark elements 38 are labeled with reference numerals (see Figure 1). Figure 5 ).

[0094] In addition, the surface of the calibration mark is made of a material that reflects light in a diffuse manner.

[0095] The sheet material processing unit 10 also includes a camera unit 40, which is movably supported on the frame 12 by a linear drive unit 42 (see [link]). Figure 4 This allows the camera unit 40 to be displaced along the width of the upper tool 18 and the lower tool 14, which corresponds to the Y direction.

[0096] In this embodiment, the camera unit 40 includes a reflector 40a for redirecting an incident light beam, which is substantially oriented along the vertical direction 24, onto the lens 40b.

[0097] Lens 40b is positioned adjacent to mirror 40a in a substantially horizontal direction. Image detector 40c is positioned behind the lens and receives the light beam transmitted by lens 40b.

[0098] As explained regarding the alignment method, the camera unit 40 is arranged such that it can simultaneously capture a portion of the upper tool 18 including the first opening 28 and a portion of the lower tool 14 located behind the first opening 28 including the first mark 32.

[0099] Furthermore, the camera unit 40 can be moved to a position where the camera unit 40 can simultaneously capture a portion of the upper tool 18 including the second opening 30 and a portion of the lower tool 14 located behind the second opening 30 and including the second mark 34.

[0100] In addition, the calibration mark 36 can be detected by the camera unit 40.

[0101] Furthermore, the sheet material processing unit 10 includes four sets of non-intersecting light sources, each set of light sources containing exactly one light source 44a, 44b, 44c, 44d for illuminating the portion to be captured by the camera unit 40.

[0102] In the following text, each of light sources 44a, 44b, 44c, and 44d will represent the light source of the corresponding group.

[0103] Please note that in this embodiment we use non-intersecting groups of light sources, but we might typically use four different groups of light sources, each sharing some light sources with its adjacent groups. In fact, this can happen when using LED rings, where each illumination represents slightly more than a quarter ring (the same logic applies when using a ring as two groups of light sources).

[0104] Light sources 44a, 44b, 44c, and 44d are configured to illuminate these portions sequentially, meaning they are not activated at the same time. This will be explained below with reference to the method according to the invention.

[0105] To achieve high-quality processing results, specifically to accurately and reliably peel the sheet material 26, the upper tool 18 and the lower tool 14 need to be precisely aligned when the upper tool 18 is in its lower position. Only in this position do the upper tool 18 and the lower tool 14 interact with each other. Furthermore, the upper tool 18 and the lower tool 14 need to be carefully aligned with the sheet material 26 to be processed.

[0106] However, it has been found that it is more convenient to assess alignment when the upper tool 18 is in its upper position than when it is in its lower position.

[0107] This is feasible if the sheet material processing unit 10 is correctly calibrated.

[0108] To this end, the upper tool 18 is moved to the middle position, which in the example shown corresponds to its lower position, and the image of the calibration mark 36 is captured by the camera unit 40.

[0109] Since the position of the camera unit 40 is known, the position of the calibration mark 36 in the plane extending in the X and Y directions can be calculated by analyzing the captured image.

[0110] Furthermore, the vertical position of the calibration mark 36, i.e., its position in the Z direction, can be calculated by analyzing the captured image and combining it with the known position of the camera unit and the known predefined layout. Since the layout is known, the scaling factor can be calculated by analyzing the image, and the position along the z direction can be derived from the scaling factor.

[0111] Subsequently, the upper tool 18 is moved to its upper position, and the image of the calibration mark 36 is captured by the camera unit 40.

[0112] At the same location on the upper tool 18, by analyzing the captured image and combining it with the known position of the camera unit 40, the position of the calibration mark 36 in the plane extending in the X and Y directions can be calculated.

[0113] As above, the position of calibration mark 36 in the Z direction can also be calculated by analyzing the captured image and combining the known position of the camera unit with the known predefined pattern.

[0114] Using the above positions, the spatial difference between the upper and lower positions of the upper tool 18 can be calculated. The spatial difference can be represented in vector form.

[0115] By evaluating the above positions, the angle α between the actual movement direction Z' of the upper tool 18 and its lower and upper positions and the optical axis 25 can also be calculated (see...). Figure 3 ).

[0116] Because of this calibration, the lower position of the upper tool 18 can be calculated based on the known upper position of the upper tool 18.

[0117] It is understood that only one calibration mark 36 is provided in this embodiment, so calibration is performed only at one position of the camera unit 40. However, it is understood that the above calibration steps can also be performed at multiple positions of the camera unit 40, wherein a calibration mark 36 is provided at each position.

[0118] Once calibration is complete, with the upper tool 18 in its upper position, the alignment of the upper tool 18 and the lower tool 14 relative to each other can be evaluated. As explained above, the lower position of the upper tool 18 can be calculated using the calibration results described above. The lower position is indeed relevant for calibration purposes.

[0119] The camera unit 40 is positioned such that it can simultaneously capture a portion of the upper tool 18, including the first opening 28, and a portion of the lower tool 14 located behind the first opening 28. This portion of the lower tool 14 includes a first mark 32.

[0120] Then the first light source 44a is activated, while the remaining light sources 44b, 44c, and 44d are not activated. Therefore, the first light source 44a illuminates the upper tool 18 and the lower tool 14, causing an edge 46a of the first opening 28 to cast a shadow 48a on a portion of the lower tool 14 located below the first opening 28 (see...). Figure 6 ).

[0121] The camera unit 40 captures a first image, which includes a first opening 28 and a portion of a lower tool 14 located below the first opening 28 and including a first mark 32.

[0122] Subsequently, the second light source 44b is activated, while the remaining light sources 44a, 44c, and 44d remain inactive. Therefore, the second light source 44b illuminates the upper tool 18 and the lower tool 14, causing an edge 46b of the first opening 28 to cast a shadow 48b on a portion of the lower tool 14 located below the first opening 28 (see...). Figure 7 ).

[0123] The camera unit 40 captures a second image, which includes a first opening 28 and a portion of a lower tool 14 located below the first opening and including a first mark 32.

[0124] Then, the third light source 44c is activated, while the remaining light sources 44a, 44b, and 44d are not activated. Therefore, the third light source 44c illuminates the upper tool 18 and the lower tool 14, causing an edge 46c of the first opening 28 to cast a shadow 48c on a portion of the lower tool 14 located below the first opening 28 (see...). Figure 8 ).

[0125] The camera unit 40 captures a third image, which includes a first opening 28 and a portion of a lower tool 14 located below the first opening 28 and including a first mark 32.

[0126] Finally, the fourth light source 44d is activated, while the remaining light sources 44a, 44b, and 44c remain inactive. Therefore, the fourth light source 44d illuminates the upper tool 18 and the lower tool 14, causing one edge 46d of the first opening 28 to cast a shadow 48d on a portion of the lower tool 14 located below the first opening 28 (see...). Figure 9 ).

[0127] The camera unit 40 captures a fourth image, which includes a first opening 28 and a portion of a lower tool 14 located below it and including a first mark 32.

[0128] Then, by combining the analysis of the four images, the corresponding positions of the edges 46a, 46b, 46c, and 46d of the first opening 28 are determined. Figure 10 An image combining the four images described above is shown.

[0129] As can be seen from the figure, due to the continuous illumination from the four light sources 44a, 44b, 44c, and 44d, the edges 46a, 46b, 46c, and 46d can be clearly identified as the boundary lines between the relatively bright areas of the upper tool 18 and the relatively dark areas of the cast shadows 48a, 48b, 48c, and 48d.

[0130] Therefore, the position of the first opening 28 can be deduced from these images.

[0131] Since the position of the first opening 28 within the upper tool 18 is known, the position of the upper tool 18 can also be easily derived.

[0132] Furthermore, by combining and analyzing the four images as described above, the position of the first marker 32 can be identified with high precision.

[0133] Since the position of the first mark 32 relative to the lower tool 14 is known, the position of the lower tool 14 is easily derived.

[0134] By using the positions of the upper tool 18 and the lower tool 14, the positional offset between tools 14 and 18 can be calculated.

[0135] This position offset is an indicator of the alignment of the upper tool 18 and the lower tool 14 relative to each other.

[0136] In a further step, the camera unit 40 is positioned such that it can simultaneously capture a portion of the upper tool 18, including the second opening 30, and a portion of the lower tool 14 located behind the second opening 30. This portion of the lower tool 14 includes a second mark 34.

[0137] For this purpose, the camera unit 40 is moved along the Y direction using a linear drive unit 42.

[0138] Subsequently, the steps of activating the four light sources 44a, 44b, 44c, and 44d sequentially, as explained in the context of the position of the camera unit 40 associated with the first opening 28, are repeated. Please refer to the explanation above.

[0139] Based on this, another positional offset between tools 14 and 18 is calculated.

[0140] If one or both position offsets are outside the desired range, the alignment of tools 14 and 18 can be adjusted by moving one or more of the tools 14 and 18 using the respective alignment units 16 and 20.

[0141] Therefore, the upper tool 18 and the lower tool 14 are aligned with each other.

[0142] The alignment of the upper tool 18 and the lower tool 14 relative to the sheet material 26 can now be evaluated. It is important to note that the alignment of tools 14 and 18 relative to each other remains unchanged throughout this document. In other words, the relative positions of tools 14 and 18 are maintained.

[0143] To accomplish this task, sheet material 26 needs to be placed between upper tool 18 and lower tool 14. Thus, when viewed from above upper tool 18, lower tool 14 is covered by sheet material 26, with corresponding portions of sheet material 26 behind the first opening 28 and the second opening 30, each portion including sheet markings 50.

[0144] Since the evaluation of the alignment of the upper tool 18 and the lower tool 14 relative to the sheet material 26 is very similar to the evaluation of the alignment of the upper tool 18 and the lower tool 14 relative to each other, it will be referred to again. Figures 6 to 10 .exist Figures 6 to 10 In the text, sheet material 26 is indicated as a replacement for lower tool 14, and one of the sheet markings is indicated as a replacement for first marking 32.

[0145] The camera unit 40 is positioned such that it can simultaneously capture a portion of the upper tool 18 including the first opening 28 and a portion of the sheet material 26 located behind the first opening 28. This portion of the sheet material 26 includes sheet markings 50.

[0146] Then, the first light source 44a is activated, while the remaining light sources 44b, 44c, and 44d are not activated. Therefore, the first light source 44a illuminates the upper tool 18 and the sheet material 26, causing one edge 46a of the first opening 28 to cast a shadow 48a on a portion of the sheet material 26 located below the first opening 28 (see...). Figure 6 ).

[0147] The camera unit 40 captures a first image, which includes a first opening 28 and a portion of sheet material 26 located below the first opening 28 and including sheet markings 50.

[0148] Subsequently, the second light source 44b is activated, while the remaining light sources 44a, 44c, and 44d remain inactive. Therefore, the second light source 44b illuminates the upper tool 18 and the sheet material 26, causing one edge 46b of the first opening 28 to cast a shadow 48b on a portion of the sheet material 26 located below the first opening 28 (see...). Figure 7 ).

[0149] The camera unit 40 captures a second image, which includes a first opening 28 and a portion of sheet material 26 located below the first opening 28 and including sheet markings 50.

[0150] Then, the third light source 44c is activated, while the remaining light sources 44a, 44b, and 44d are not activated. Therefore, the third light source 44c illuminates the upper tool 18 and the sheet material 26, causing one edge 46c of the first opening 28 to cast a shadow 48c on a portion of the sheet material 26 located below the first opening 28 (see...). Figure 8).

[0151] The camera unit 40 captures a third image, which includes a first opening 28 and a portion of sheet material 26 located below the first opening 28 and including sheet markings 50.

[0152] Finally, the fourth light source 44d is activated, while the remaining light sources 44a, 44b, and 44c remain inactive. Therefore, the fourth light source 44d illuminates the upper tool 18 and the sheet material 26, causing one edge 46d of the first opening 28 to cast a shadow 48d on a portion of the sheet material 26 located below the first opening 28 (see...). Figure 9 ).

[0153] The camera unit 40 captures a fourth image, which includes a first opening 28 and a portion of sheet material 26 located below it and including sheet markings 50.

[0154] Then, by combining the analysis of the four images, the corresponding positions of the edges 46a, 46b, 46c, and 46d of the first opening 28 are determined. Figure 10 An image combining the four images described above is shown.

[0155] As can be seen from the figure, due to the continuous illumination from the four light sources 44a, 44b, 44c, and 44d, the edges 46a, 46b, 46c, and 46d can be clearly identified as the boundary lines between the relatively bright areas of the upper tool 18 and the relatively dark areas of the cast shadows 48a, 48b, 48c, and 48d.

[0156] Therefore, the position of the first opening 28 can be deduced from these images.

[0157] Since the position of the first opening 28 within the upper tool 18 is known, the position of the upper tool 18 can also be easily derived.

[0158] Furthermore, by combining and analyzing the four images as described above, the position of the sheet marking 50 can be identified with high precision.

[0159] Since the position of the sheet mark 50 relative to the sheet material 26 is known, the position of the sheet material 26 can be easily derived.

[0160] Using the position of the upper tool 18 and the position of the sheet material 26, the corresponding positional offset can be calculated.

[0161] This positional offset is an indicator of the alignment of the upper tool 18 and the lower tool 14 relative to the sheet material 26.

[0162] In the next step, the camera unit 40 is positioned such that it can simultaneously capture a portion of the upper tool 18 including the second opening 30 and a portion of the sheet material 26 located behind the second opening 30. This portion of the sheet material 26 also includes one of the sheet markings 50.

[0163] For this purpose, the camera unit 40 is moved along the Y direction using a linear drive unit 42.

[0164] Subsequently, the steps of activating the four light sources 44a, 44b, 44c, and 44d sequentially, as explained in the context of the positions of the camera unit 40 and the first opening 28, are repeated. Please refer to the explanation above.

[0165] Based on this, another positional offset between the upper tool 18 and the sheet material 26 is calculated.

[0166] If one or two positional offsets are outside the desired range, the alignment of tools 14 and 18 relative to the sheet material 26 can be adjusted by moving tools 14 and 18 together using their respective alignment units 16 and 20.

[0167] Therefore, the upper tool 18 and the lower tool 14 are aligned with respect to the sheet material 26.

[0168] Figure 11 A sheet material processing unit 10 according to an alternative embodiment is shown.

[0169] This variant differs from the previously described implementation in that it provides only two sets of non-intersecting light sources 44a and 44b, with each set containing exactly one light source.

[0170] Its first light source 44a is configured to illuminate a portion of the upper tool 18 including the first opening 28 and a portion of the lower tool 14 located below the first opening 28 or a portion of the sheet material 26 located below the first opening 28, such that the two edges 46a, 46c simultaneously cast shadows 48a, 48c on the lower tool 14 or the sheet material 26.

[0171] Its second light source 44b is configured to illuminate a portion of the upper tool 18 including the first opening 28 and a portion of the lower tool 14 or sheet material 26 located below the first opening 28, such that the two edges 46b, 46d simultaneously cast shadows 48b, 48d on the lower tool 14 or sheet material 26.

[0172] For the remaining features, their corresponding effects and advantages, please refer to [link / reference]. Figures 1 to 10 The implementation method shown.

[0173] It should be noted that in all the above embodiments, the first opening 28 and the second opening 30 are disposed in the upper tool 18, and the camera unit 40 is positioned above the upper tool 18. Obviously, this solution can also be kinematically reversed, such that the first opening 28 and the second opening 30 are disposed in the lower tool 14, and the camera unit 40 is arranged below the lower tool 14.

Claims

1. A sheet material processing unit (10) for processing paper sheets, cardboard sheets, or plastic sheets for packaging, comprising: A frame (12), an upper tool (18), and a lower tool (14), wherein the upper tool (18) and the lower tool (14) are configured to interact with each other to process sheet material (26), the upper tool (18) and the lower tool (14) are mounted on the frame (12) by respective upper alignment units (20) and respective lower alignment units (16), the upper alignment units (20) and the respective lower alignment units (16) being used to align the upper tool (18) and the lower tool (14) relative to each other and relative to the sheet material (26) to be processed, wherein the upper tool (18) includes a first opening (28). A camera unit (40), arranged such that it can simultaneously capture a portion of an upper tool (18) including a first opening (28) and a portion of a lower tool (14) located behind the first opening (28), for aligning the upper tool (18) and the lower tool (14), and The first set of light sources includes at least one light source (44a, 44b, 44c, 44d) for illuminating the portion to be captured. The second set of light sources includes at least one light source (44a, 44b, 44c, 44d) for illuminating the portion to be captured. The first group of light sources and the second group of light sources are different from each other and are configured to illuminate the portion to be captured sequentially, so as to obtain a first image when the first group of light sources is enabled and a second image when the second group of light sources is enabled. The location of the first opening is detected by combining information about the shadows contained in the first and second images.

2. The sheet material processing unit (10) according to claim 1, characterized in that, A first mark (32) is set on a portion of the lower tool (14) located behind the first opening (28).

3. The sheet material processing unit (10) according to claim 1 or 2, characterized in that... The camera unit (40) is movably supported on the frame (12) by a linear drive unit (42), so that the camera unit (40) can be moved along the width of the upper tool (18).

4. The sheet material processing unit (10) according to claim 3, characterized in that... A second opening (30) is provided on the upper tool (18) including the first opening (28), wherein the camera unit (40) is movable by a linear drive unit (42) such that the camera unit (40) is able to simultaneously capture a portion of the upper tool (18) including the second opening (30) and a portion of the lower tool (14) located behind the second opening (30).

5. The sheet material processing unit (10) according to claim 4, characterized in that... A second mark (34) is set on a portion of the lower tool (14) located behind the second opening (30).

6. The sheet material processing unit (10) according to claim 1 or 2, characterized in that... The calibration mark (36) is positioned on the upper tool (18) or on the corresponding tool holder to which the upper tool (18) is attached, and the calibration mark (36) can be detected by the camera unit (40).

7. The sheet material processing unit (10) according to claim 6, characterized in that, The surface of the calibration mark (36) is made of a material that reflects light in a diffuse manner.

8. The sheet material processing unit (10) according to claim 6, characterized in that... The calibration mark (36) includes multiple mark elements (38) arranged in a predefined layout.

9. The sheet material processing unit (10) according to claim 1 or 2, characterized in that... The upper tool (18) is connected to the vertical drive unit (22) and the lower tool (14) is substantially fixed within the frame (12) so that the upper tool (18) is movable relative to the lower tool (14) in the vertical direction (24) to process sheet material (26).

10. The sheet material processing unit (10) according to claim 1 or 2, characterized in that... The first group of light sources consists of individual light sources (44a, 44b, 44c, 44d), and the second group of light sources consists of individual light sources (44a, 44b, 44c, 44d).

11. A method for evaluating the alignment of an upper tool (18) and a lower tool (14) of a sheet material processing unit (10) according to any one of claims 1 to 10 relative to each other, comprising the steps of: a) The positioning camera unit (40) is configured to simultaneously capture a portion of the upper tool (18) including the first opening (28) and a portion of the lower tool (14) located behind the first opening (28). b) Activate a first group of light sources including at least one light source (44a), while the remaining groups of light sources are not activated, and capture a first image of a portion of the upper tool (18) including the first opening (28) and a portion of the lower tool (14) located behind the first opening (28) and including the first mark (32). c) Activate a second group of light sources including at least one light source (44b), while the remaining groups of light sources are not activated, and capture a second image of a portion of the upper tool (18) including the first opening (28) and a portion of the lower tool (14) located behind the first opening (28) and including the first mark (32). d) By combining the analysis of the first and second images, determine the positions of at least two edges (46a, 46b, 46c, 46d) of the first opening (28), and deduce the position of the upper tool (18) including the first opening (28) from the positions of the at least two edges (46a, 46b, 46c, 46d). e) By combining the analysis of the first and second images, the position of the first mark (32) is determined, and the position of the lower tool (14) including the first mark (32) is derived from the position of the first mark (32). f) Calculate the positional offset between the position of the upper tool (18) and the position of the lower tool (14).

12. A method for evaluating the alignment of an upper tool (18) of a sheet material processing unit (10) according to any one of claims 1 to 10 with respect to a sheet material (26) disposed therein, comprising the steps of: a) The positioning camera unit (40) is configured to simultaneously capture a portion of the upper tool (18) including the first opening (28) and a portion of the sheet material (26) located behind the first opening (28). b) Activate a first group of light sources including at least one light source (44a), while the remaining groups of light sources are not activated, and capture a first image of a portion of the upper tool (18) including the first opening (28) and a portion of the sheet material (26) located behind the first opening (28) and including the sheet mark (50). c) Activate a second group of light sources including at least one light source (44b), while the remaining groups of light sources are not activated, and capture a second image of a portion of the upper tool (18) including the first opening (28) and a portion of the sheet material (26) located behind the first opening (28) and including the sheet mark (50). d) By combining the analysis of the first and second images, the positions of at least two edges (46a, 46b, 46c, 46d) of the first opening (28) are determined, and the position of the upper tool (18) including the first opening (28) is derived from the positions of the at least two edges (46a, 46b, 46c, 46d). e) The position of the sheet mark (50) is determined by combining the analysis of the first and second images, and the position of the sheet material (26) is deduced from the position of the sheet mark (50). f) Calculate the positional offset between the position of the upper tool (18) and the position of the sheet material (26).

13. The method according to claim 11 or 12, characterized in that, The method is performed with the upper tool (18) in its upper position, wherein the calibration results are used to calculate the alignment of the upper tool (18) with respect to its lower position.

14. The method according to claim 11 or 12, characterized in that, In the active state, the first set of light sources, including at least one light source (44a), and / or the second set of light sources, including at least one light source (44b), illuminate the upper tool (18), the lower tool (14), or the sheet material (26), such that at least one edge (46a, 46b, 46c, 46d) of the first opening (28) casts a shadow (48a, 48b, 48c, 48d) on the portion located below the first opening (28).

15. The method according to claim 11 or 12, characterized in that, A second opening (30) is provided on the upper tool (18), and the method according to any one of claims 11 to 12 is performed when the camera unit (40) is positioned such that it can simultaneously capture a portion of the upper tool (18) including the second opening (30) and a portion located behind the second opening (30).

16. The method according to claim 11 or 12, characterized in that, The sheet material processing unit (10) according to any one of claims 1 to 10 is calibrated, the calibration comprising the following steps: a) Move the upper tool (18) to its upper position and capture the calibration mark (36) associated with the upper tool (18) by the camera unit (40), wherein the calibration mark (36) includes a plurality of mark elements (38) arranged according to a predefined layout. b) Calculate the first position of the calibration mark (36) in the horizontal plane associated with the upper position of the upper tool (18). c) Move the upper tool (18) to its middle position and capture the calibration mark (36) associated with the upper tool (18) through the camera unit (40). d) Calculate the second position of the calibration mark (36) in the horizontal plane associated with the intermediate position of the upper tool (18), and e) Calculate the calibration result including the vector connecting the first position and the second position.

17. The method according to claim 16, characterized in that, The sheet material processing unit (10) is calibrated before performing step (a).

18. The method according to claim 16, characterized in that, The middle position of the upper tool (18) is the lower position of the upper tool (18).

Images