punching machine

Abstract

Punching machine (10) for processing material in sheet form, in particular for processing cardboard sheets (12), with a transport mechanism (20, 36) for transporting sheets (12) one after the other from a feed side of the machine (10) via at least one processing station (22, 26, 30) to an ejection side along a transport path (TP), wherein the machine (10) has a recording system (42) with at least one high-speed camera (44) which is assigned to the blanking tool (32) for recording a plurality of images of a representative section of the sheets (12) transported along the transport path (TP), a memory for storing recorded images and a processing system (67) for processing the stored images.

Description

[0001] The invention relates to a die-cutting machine for processing material in sheet form, in particular for processing cardboard sheets, with a transport mechanism for transporting sheets one after the other from a feed side of the machine via at least one processing station to an ejection side along a transport path.

[0002] Die-cutting presses play a crucial role in the printing and packaging industries, serving as essential equipment for die-cutting, creasing, embossing, and other processing operations on sheet-fed materials. These machines are designed to handle materials such as cardboard, cardstock, and various types of paper, transforming flat sheets into the complex shapes and designs required for packaging, promotional materials, and other applications. Operating a die-cutting press involves the sequential processing of sheets, which are transported at high speed through multiple stations. This transport is typically facilitated by gripper bars driven by chains. The gripper bars securely hold the leading edge of each sheet to guide it precisely through the die-cutting and creasing stations.

[0003] In high-speed production environments, ensuring the integrity and precise positioning of each sheet throughout the entire process is crucial. However, a common challenge is the tendency of the sheets to deform as they move through the machine.

[0004] Factors such as rapid acceleration and deceleration, as well as aerodynamic effects, can cause the sheets to bend or become wavy. This deformation affects the sheet's flatness and leads to misalignment when the sheet undergoes punching or creasing operations.

[0005] A deformation of the sheet can have two serious consequences: firstly, premature detachment of pre-cut blanks from the rest of the sheet, and secondly, misalignment of the subsequent sections of the sheet in relation to the blank separation tools or creasing knives.

[0006] Premature separation can occur if the leading edge of a pre-cut blank is caught by the airflow and subjected to such force that the connection between the pre-cut blank and the rest of the sheet (the so-called "holding points," which are narrow material bridges left behind during the pre-cutting process) breaks. The leading edge of the blanks is exposed to the airflow when the sheet bends and the leading edge is located at the tip of a flute. Should the blank separate from the rest of the sheet at a location other than the intended ejection or collection point, it can fall into the machine and cause blockages, bringing the press to a standstill. Such interruptions reduce productivity.

[0007] Misalignment occurs when a sheet is processed in a processing station while still in a wavy state. The wavy state can result from the sheet slowing down considerably upon reaching the processing station. Due to the wavy shape of the sheet, the contact points between the sheet and the blanking tools or creasing knives change. Generally, the overall length of a wavy sheet is less than the length of a flat sheet, causing sections at the trailing end of the sheet to be positioned closer to the leading end than expected. This leads to incomplete cuts or unintended pressure on certain areas.

[0008] Modern die-cutting machines use sensors strategically positioned along the sheet's path to continuously monitor its condition and the desired processing. If a problem occurs, such as a blank unintentionally detaching from the sheet, the machine stops.

[0009] For machine operators, identifying and diagnosing the cause of sheet detachment is a significant challenge. The rapid movement of sheets through the printing press makes it virtually impossible to visually monitor each sheet in real time. Operators often have no choice but to determine the causes of blockages after they occur, which can lead to repeated downtime as they make adjustments through trial and error. Without a clear understanding of when and where the deformation occurs, it is difficult to implement effective countermeasures, thus prolonging the production process interruption.

[0010] The invention offers a solution to this problem by providing a system that enables operators to determine the cause of the machine stopping. In particular, the invention consists of identifying the cause of a failed cutting ejection.

[0011] For this purpose, the invention provides a machine as described above, wherein the machine has a recording system with at least one high-speed camera assigned to the blanking tool for recording several images of a representative section of the sheets transported along the transport path, a memory for storing recorded images and a processing system for processing the stored images.

[0012] The recording system allows for the recording of the specific location and extent of deformation. This real-time data enables immediate analysis and reveals patterns that may indicate underlying problems. By accurately determining the exact stage at which a problem occurs, operators can quickly identify the necessary adjustments to resolve it.

[0013] Furthermore, the system can be programmed to automatically adjust certain machine parameters in response to detected problems, thereby further improving the efficiency of corrective actions.

[0014] In general terms, the idea of ​​the invention is to place a camera near the recorded blanking tool inside the machine in such a way that the blanking ejection in the blanking station is recorded.

[0015] The key points of interest are the braking phase and the beginning of the processing phase. During the braking phase, the sheet is clearly visible because the upper tool is in a high position, and if something goes wrong, the cause might be apparent at this stage. The beginning of the processing phase allows you to see whether the sheet and the blanks formed within it are correctly aligned.

[0016] The recordings can also be used to determine whether each blank is correctly positioned before separation by the blanking tool. For this purpose, a model of the sheet (e.g., in PDF format) is used, and the processing system analyzes the recorded images to verify that each blank is in its intended position.

[0017] Another embodiment of the invention comprises a display to provide an operator with an image sequence that is representative of a problem that occurs. Providing the operator with an image sequence representative of the problem improves troubleshooting capabilities. By visualizing the problem as it occurs, operators can diagnose problems more effectively and take appropriate corrective action immediately.

[0018] The recording system can be designed to capture multiple images of a representative section of the sheets synchronously with the machine cycles, enabling the analysis or display of a selected image sequence for any sheet in relation to the machine cycle timeline. This reduces the time required by an operator to retrieve the relevant images and also decreases the required storage capacity for the images, as only relevant images are captured.

[0019] Preferably, the display is designed to show a sequence of images in relation to the timeline of the machine cycle, thereby reducing the time required by an operator to understand what caused the machine to stop.

[0020] In one embodiment, the at least one high-speed camera is arranged such that its optical axis is directed into the space between an upper depaneling tool and a lower depaneling tool of the machine, so that the camera can record an arc arranged between the upper and the lower tool.

[0021] Preferably, several high-speed cameras are used, in particular two or more on opposite sides of the depaneling tool. By using multiple cameras, it is possible for each camera to record only a portion of the top surface of the sheet, so that each camera has a better view of "its" portion of the top surface than in an arrangement with a single camera that has to record the entire surface of the sheet.

[0022] In one embodiment, the high-speed camera is arranged above the plane in which the sheet is held in the depaneling tool, with a mirror provided so that the camera can record the sheet. This makes it possible to arrange the camera(s) above the depaneling tool at a location where more space is available than to the side of the depaneling tool.

[0023] The high-speed camera is equipped with a cleaning system to remove dust and dirt from the camera lens.

[0024] To improve the quality of the images recorded by the high-speed camera(s), a lighting system can be assigned to the high-speed cameras.

[0025] In one embodiment, the processing system includes an image evaluation unit for determining a deviation of a recorded section of the sheet from a predefined position or configuration, making it easier for an operator to identify the cause of a problem.

[0026] The processing system is preferably designed to perform homography of the recorded images in order to convert an image recorded at an oblique viewing angle into an image taken in a top view.

[0027] Preferably, the machine is designed to To transport the sheet with the gripper bar from the feed side of the machine via at least one processing station to an ejection side, to record several images of at least one representative section of the arc using the recording system, where the recording with the recording system is synchronized with the machine cycle in order to track the position of the image in relation to the timeline of the cycle, to store the recorded images in a buffer of limited size in order to retain a record of the images in relation to the timeline of the cycle for only a limited number of cycles, In the event of a machine stoppage, the recording system should be stopped to preserve the multiple images that were stored in the buffer before the machine stopped. to display a sequence of images selected in relation to the timeline of the cycles.

[0028] By recording an image sequence that depicts a representative section of the sheets synchronously with the machine cycles, synchronization allows the operator to analyze the behavior of a selected subsequence of the processing. For example, the operator can select to visualize the movement and position of the sheet immediately after it is placed in the register. Synchronizing the recording with the machine cycle makes it very easy for the operator to select to visualize the movement of the next or previous sheet (or any other sheet) immediately after it is placed in the register, as it is sufficient to jump to the position of the recorded images separated in time by an integer multiple of the machine cycle.By synchronizing the recording with the machine cycle, some metadata can also be inserted into the recording, for example, by adding the time the register device closes in the feed station or the time of transfer to the gripper bar. This time can be a timestamp if the action takes almost no time, or a time interval indicating the start and end of the action.

[0029] Preferably, the image sequence is selected to show the sheet arranged on the lower blanking tool before and after the blanking step. Images taken before the blanking step can detect any misalignment of the sheet or damage to the blanks at the time the sheet reaches the blanking station. Images taken after the blanking step can identify which blank was not ejected correctly, allowing the blanking tool to be checked for potential problems. Preferably, at least two different image sequences with the same relationship to the cycle timeline are displayed, enabling an operator to easily compare two sequences of the sheet being picked up by the register and its transfer to the gripper.

[0030] The recorded images can be stored in a ring buffer, thus eliminating the need for large storage capacities to hold large amounts of data. In practice, only a limited number of the most recent processing cycles are relevant for identifying a problem. A typical number of recent cycles stored in the ring buffer is ten sheets.

[0031] An embodiment of the invention will now be described with reference to the accompanying drawings. These drawings show... Fig. 1 schematically a punching machine, Fig. 2 the speed of a sheet being advanced from a first to a second processing station, Fig. 3 a bow that is advanced at high speed using a gripper rod, Fig. 4 schematically a utility separation station of the machine Fig. 1 in a front view, Fig. 5 in a top view an arc with several cutouts, Fig. 6 schematically two cameras arranged on one side of the arc, with the cameras on the opposite side not shown, Fig. 7 schematically, that with one of the cameras from Fig. 6 recorded images, Fig. 8 schematically the one with the other of the cameras from Fig. 6 recorded images, Fig. 9 schematically the image reconstructed by homography, Fig. 10 schematically the high-speed camera with a cleaning system provided for it in cross-section, Fig. 11 schematically the high-speed camera from Fig. 10 in a top view, and Fig. 12 schematically an image recording system which is an alternative to the embodiment from Fig. 4 represents.

[0032] Fig. Figure 1 schematically shows a die-cutting machine 10, which is designed to transform sheets 12 (usually made of cardboard) into pre-cut flat boxes. These boxes are then folded and glued using another machine.

[0033] The process of producing the pre-cut flat boxes (hereinafter referred to as "cutouts 14") consists of cutting out shapes from flat cardboard sheets 12 in the die-cutting machine 10. The sheets pass through several stations, including an infeed station 16, where sheets 12 are individually removed from a stack; a feed station 18 with a feed table 19, on which sheets 12 are aligned and gripped by a gripper bar 20; a press station 22, where the sheets 12 are punched and scored by a punch press 24; a waste ejection station 26, where unwanted parts of the sheet 12 are removed with an ejection tool 28; a blanking station 30, where the pre-punched blanks 14 are removed and stacked with a blanking tool 32; and an ejection station 34, where the remaining parts of the sheet 12 are released by the gripper bar 20 and removed via a belt 40.

[0034] The transport of the sheets 12 through various processing stations is carried out by a chain drive system and a gripper bar mechanism. The chain drive consists of endless chains 36 that run the length of the machine 10 and ensure synchronized and precise movement of the gripper bars 20 attached to the chains. The gripper bars 20 securely hold the leading edge of each sheet 12.

[0035] On the feed table 19, the sheets 12 are aligned by a register device 50 (described in more detail below) to ensure correct positioning and then gripped by the gripper bar 20. The gripper bar 20 firmly grasps the leading edge of the sheet 12 so that it can be transported precisely through the subsequent stations of the machine. The movement of the gripper bar 20 is synchronized with the action of the tools in the press station 22, the eject station 26, and the blanking station 30.

[0036] The movement of the arcs 12 from one station to the next comprises several different phases (viewed in direction A, in which the arcs are transported along a transport track TP by the machine 10): acceleration a, constant high-speed travel t, deceleration d and standstill s (see Fig. 2) The entirety of these phases constitutes a complete machine cycle MC.

[0037] To achieve a high throughput of approximately three large sheets 12 per second, the time required to transfer a sheet 12 from one station to the next should be as short as possible. Accordingly, a high transport speed must be achieved, which requires strong acceleration so that the sheet 12 reaches this speed as quickly as possible. Conversely, strong deceleration is also necessary so that the sheet 12 can be transported at this high speed for as long as possible. Two phases of the sheet 12 transport cycle are critical: the high-speed phase and the strong deceleration phase. Furthermore, the transfer of the sheet 12 from the feed table to the gripper bar 20 is critical.

[0038] Due to the high speed at which the sheets 12 are gripped by the gripper bars 20 and then travel through the machine, it is impossible for an operator to visually identify the cause of interruptions. The core idea is to use at least one high-speed camera 44 to monitor specific points where the sheets 12 move within the machine. The camera(s) 44 is / are strategically positioned in the blanking station 30 where deviations of the sheet 12 from the expected path are critical and misaligned or otherwise defective blanking tools are critical. This will now be demonstrated using the Fig. 3 to 9 explained.

[0039] In Fig. Figure 3 shows a sheet 12 being transported at high speed along a conveyor track by the gripper bar 20 immediately before the panel separation station 30. Due to the high speed, the sheet 12 is wavy.

[0040] The gripper bar 20 transports the sheet 12 with the blanks 14 into the blanking station 30, where the sheet 12 is stopped so that it is positioned between an upper blanking tool 32A and a lower blanking tool 32B. By moving the upper blanking tool 32A downwards, the remaining holding points connecting the blanks to the rest of the sheet 12 and to adjacent blanks 14 are severed, and the blanks 14 are pushed downwards by the lower blanking tool 32B.

[0041] The machine is equipped with a recording system 42 for recording images of the sheet 12 within the blanking station 30. The recording system 42 has high-speed cameras 44 arranged to "look into" the blanking tool 32, which comprises an upper blanking tool 32A and a lower blanking tool 32B.

[0042] As in Fig. As can be seen in Figure 4, the high-speed cameras 44 are arranged on opposite sides of the travel track of the arch 12. The cameras 44 are mounted on a machine frame 49 with a downwardly angled viewing axis. This allows the field of view of each camera to cover the arch 12 from its respective side to approximately the middle of the arch 12.

[0043] As in Fig. As can be seen in Figure 5, two high-speed cameras 44 are arranged at a distance from each other on each side of the arc 12.

[0044] The high-speed camera 44 records all phases of the machine cycle at a high frame rate (> 50 frames per second). Each film segment recorded in this way begins in the braking phase of the sheet 12 in the blanking station 30. The points of interest are the braking phase and the beginning of the processing phase. In the braking phase, the sheet is clearly visible because the upper tool is in a high position, and if something goes wrong, the cause could be seen in this phase. The beginning of the processing phase makes it possible to see whether the sheet / blank is correctly aligned.

[0045] Each recorded film segment can stop at the point where the upper delimiter 32A is closed, so that no relevant information would be recorded if the film were to continue. However, the film segment can include the phase in which the upper delimiter 32A is moved upwards, as the framework of the sheet 12 is then visible, which could provide relevant information if some blanks are not properly separated from the framework. To reduce the size of the film segment, images recorded during the phase with the delimiter 32 closed can be hidden.

[0046] The Fig. 6 and Fig. Figure 7 shows examples of the images recorded by the cameras 44. When the cameras 44 capture the arc 12, each camera 44 records a perspective projection of the arc 12 onto the camera sensor. Therefore, the cropped images 14 appear distorted.

[0047] The pattern of the cuts 14 is subjected to a homography transformation to reconstruct the image of the arc as if it had been taken from above, thus facilitating the visual analysis of the arc alignment.

[0048] Since arch 12 is captured by several cameras 44, the images are combined to form a single image showing the entire arch 12. Alternatively, it is possible to record the video from each camera individually.

[0049] The homography, which relates the geometry of the sheet and its projection onto the camera, can be calculated by identifying four reference points printed on the lower depaneling tool 32B (or on a calibration plate / sheet used at the lower tool position). Since the camera's position relative to the lower tool does not vary, this calibration only needs to be performed once.

[0050] Assuming that the reference point is denoted as Pi, expressed in the coordinate system of the arc, and Pi(1) as the coordinates of the same reference point, but expressed in the coordinate system of camera number 1, then homography is the transformation that relates Pi to Pi(1). As many homographies are calculated as there are cameras. Subsequently, it is possible to reconstruct the images of the arc by taking the coordinates Pi of each pixel in the image of the arc and determining its coordinate in camera n: Pi(n).

[0051] If this coordinate is within the image boundaries, the pixel value of the arc can be retrieved by determining the pixel value at the coordinate Pi(n) in the images of camera n.

[0052] If it is assumed that Pi(n) lies outside the bounds, this can be tried again with all other available cameras until the pixel value is obtained or it is determined that the pixel corresponds to an area not recorded by any of the cameras. In practice, some areas are covered by more than one camera, so the image is reconstructed by selecting the camera from which the value is to be obtained.

[0053] These reconstruction techniques are known in the fields of image composition and photogrammetry.

[0054] It is also possible to use the cameras to determine whether each blank is correctly positioned before separation by the blanking tool. For this purpose, a model of the sheet (PDF) is used that identifies each blank on the sheet and stores its position. Using the image from one camera, which has been rectified with homography transformation to obtain its representation in the sheet's coordinate system, it is then possible to identify the blanks (provided their shape is known) and verify whether their position corresponds to the intended one. This can be done either in the images from each individual camera or in the reconstructed image.

[0055] As in the Fig. 10 and Fig. As shown in Figure 11, the cameras 44 are combined into a module 45, which can be pre-assembled outside the machine 10 and then installed in the machine 10.

[0056] Module 45 includes a mounting rod 46 in which the cameras 44 are held. The mounting rod 46 can be formed from separate segments arranged one after the other.

[0057] Each camera 44 is positioned so that its lens 48 is directed towards the travel track TP of the arch 12.

[0058] A lighting system 51 is provided to direct light onto the arches 12.

[0059] A cleaning mechanism 52 is provided to maintain the optimal performance of the camera 44 in the dusty environment of the punching machine 10. The cleaning system 52 includes air ducts 54 and air outlets 56.

[0060] An air duct 54 is integrated into the camera mounting rod 46, and each camera lens 48 of the recording system is assigned one of the air outlets 56.

[0061] Each camera 44 has a bypass 60 to supply compressed air to the next downstream air outlet 56.

[0062] Alternatively, the camera mounting rod 46 can have as many air channels as there are cameras 44, in order to supply each outlet 56 with air individually.

[0063] Compressed air from an air supply can be periodically directed from a supply 61 into the air duct 54 and discharged via the air outlet 56 to remove dust and particles from the surface of the camera lenses 48.

[0064] The mounting rod 46 can be designed as a single-piece element, possibly 3D-printed, which integrates the mounting structure for the cameras 44, the air ducts 54, and the air outlets 56. A 3D-printed mounting rod allows for the implementation of complex shapes for the air outlet 56 at the locations of the camera lenses 48.

[0065] The high-speed camera 44 is connected to a memory 62 for storing the recorded images of the arc 12.

[0066] Memory 62 is a ring buffer used to store recordings of a specific number of machine cycles. An example of this specific number is ten. In other words, ring buffer 62 allows the retrieval of images from the last ten machine cycles.

[0067] Additional elements of machine 10 are a control unit 64 and a display 66, which are located in Fig. 5 are shown schematically.

[0068] The control unit 64 includes an image processing system 67.

[0069] When the machine 10 is in operation, the high-speed camera 44 records images of the edge areas of each sheet 12, which is picked up in the register device 50 and transferred to the gripper bar 20. The images are stored in the ring buffer 62, from which they can be retrieved and shown to an operator in slow motion.

[0070] To reduce the amount of data to be processed, the recording of images is synchronized with the work steps of the die-cutting machine. Camera 44 captures a series of images when the sheet is, or should be, within the camera's field of view.

[0071] In general, the image processing system 67 within the controller 64 processes the recorded images so that they are made available to an operator. This processing can include adding a timestamp, a reference to the machine cycle, which allows browsing and / or comparing "identical" images from different machine cycles. The processing can also include extracting an image sequence for different machine cycles, all starting at the same reference point within a machine cycle. Finally, the processing can also include determining whether any sheet is being recorded in the register device at all.

[0072] The processing system can evaluate the video segments and determine if there is a deviation from the expected state. The controller 64 can then retrieve the relevant video segment from the buffer 62 and display the sequence on the screen 66, which consists of the last partial frames of the recorded images, thus showing the operator the state of the last sheet. The extracted video is shown to the operator in slow motion. This slow-motion playback allows the operator to observe the sheet in detail, which is not possible at normal operating speeds.

[0073] The video sequence allows an experienced operator to decide on appropriate adjustments to the die-cutting machine settings to prevent the observed problems. This not only improves output quality but also reduces machine downtime, as problems can be resolved more quickly. Specifically, the operator can adjust the machine's blanking tool 32 once the position of the sheet causing the problem is known.

[0074] There are additional countermeasures that the control unit 64 can either initiate automatically or propose to the operator for approval.

[0075] One of these countermeasures is to reduce the machine's speed. This can be done iteratively. Control unit 64 reduces the transport speed to a level at which the critical condition disappears.

[0076] These automatic adjustments not only improve the quality of the finished products but also increase the efficiency of the stamping process by reducing downtime due to machine jams. The system's ability to react to detected problems in real time enables continuous operation at optimal speeds while maintaining product integrity. Furthermore, by minimizing manual intervention, the system reduces operator workload and the risk of human error.

Claims

[1] Die-cutting machine (10) for processing material in sheet form, in particular for processing cardboard sheets (12), with a transport mechanism (20, 36) for transporting sheets (12) successively from a feed side of the machine (10) via at least one processing station (22, 26, 30) to an ejection side along a transport path (TP), wherein the machine (10) has a recording system (42) with at least one high-speed camera (44) assigned to the blanking tool (32) for recording several images of a representative section of the sheets (12) transported along the transport path (TP), a memory for storing recorded images and a processing system (67) for processing the stored images. [2] Machine (10) according to claim 1, wherein the processing system (67) comprises a display (66) to provide an operator with a sequence of images that is representative of a problem that has occurred. [3] Machine (10) according to one of the preceding claims, wherein the recording system (42) is designed to record multiple images of a representative section of the sheets (12) synchronously with the machine cycles, so that the analysis or display of a selected image sequence for any sheets with respect to the timeline of the machine cycle is possible. [4] Machine according to any of the preceding claims, wherein the display (66) is designed to display an image sequence in relation to the timeline of the machine cycle. [5] Machine (10) according to one of the preceding claims, wherein the at least one high-speed camera (44) is arranged such that its optical axis is directed into the space between an upper depaneling tool (32A) and a lower depaneling tool (32B) of the machine (10). [6] Machine (10) according to claim 5, wherein several high-speed cameras (44) are used, in particular two or more on opposite sides of the depaneling tool (32). [7] Machine (10) according to claim 5, wherein the high-speed camera (44) is arranged above the plane in which the sheet (12) is received in the blanking tool (32), wherein a mirror (70) is provided so that the camera (44) can record the sheet (12). [8] Machine according to one of the preceding claims, wherein the high-speed camera (44) is associated with a cleaning system (52). [9] Machine (10) according to one of the preceding claims, wherein a lighting system (50) is associated with the high-speed camera (44). [10] Machine (10) according to one of the preceding claims, wherein the processing system (67) comprises an image evaluation unit for determining a deviation of a recorded section of the sheet (12) from a predefined position or configuration. [11] Machine (10) according to any of the preceding claims, wherein the processing system (67) is designed to perform a homography of the recorded images. [12] Machine (10) according to any of the preceding claims, wherein the machine is designed to - to transport the sheet (12) with the gripper bar (20) from the feed side of the machine (10) via at least one processing station (22, 26, 30) to an ejection side, - to record several images of at least one representative section of sheet (12) using the recording system (42), - wherein the recording with the recording system (42) is synchronized with the machine cycle in order to track the position of the image in relation to the timeline of the cycle, - to store the recorded images in a buffer of limited size in order to retain a record of the images in relation to the timeline of the cycle for only a limited number of cycles, - to stop recording with the recording system (42) in the event of a machine stoppage, in order to retain the multiple images that were stored in the buffer before the machine stopped, - to display a sequence of images selected in relation to the timeline of the cycles. [13] Machine according to claim 12, wherein the image sequence is selected to show the sheet (12) arranged on the lower depaneling tool (32B) before and after the depaneling step. [14] Machine according to claim 12 or 12, wherein at least two different image sequences with the same relationship to the timeline of the cycles are displayed.

Images