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 feed side 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 punching 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 die-cutting 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 machine downtime. In particular, the invention consists of identifying the cause of a misaligned sheet at the inlet of the punch press on the feed table, even when a register system is in place that tracks alignment marks and corrects misalignments.

[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 record several images of a representative section of the sheet transported along the transport path on the feed side, 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, the idea of ​​the invention is to place a camera above the feed table and record inside the machine how the sheet is captured by a register device.

[0015] The critical moment is just before the sheets are gripped by the gripper bar. This occurs during the processing phase, when the sheets move along the feed table and are picked up by the grippers of the power register.

[0016] Because the register device uses alignment marks, the machine stops if the misalignment is outside the range that the power register can handle. In this case, the system typically doesn't know the sheet's position, as the alignment mark most likely wasn't detected. This can happen, for example, if the alignment mark is outside the field of view of the sensor that reads it. So, it's known that the sheet is misaligned, but it's not known how or what caused the problem. The images captured by the camera provide a deeper understanding of why the alignment mark was outside the sensor's field of view.

[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, at least one high-speed camera is arranged adjacent to a feed station of the machine. This high-speed camera makes it possible to detect potential problems if the sheet is not fed correctly from a feed station to the gripper bar.

[0021] The high-speed camera can be mounted on a machine frame and aligned with a register device of the feeding station. Positioning the camera centrally above the register device ensures an unobstructed view of the area where a sheet is inserted into the register device and gripped by the gripper bar.

[0022] 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.

[0023] Preferably, the machine is designed to

[0024] 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 retain the multiple images stored in the buffer before the machine stopped, and a sequence of images selected in relation to the timeline of cycles should be displayed.

[0025] 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 its positioning in the register system. 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 its positioning in the register system, as it is sufficient to jump to the position of the recorded images separated 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 the transfer to the gripper bar. The time can be a timestamp if the action takes almost no time, or a time interval indicating the start and end of the action.

[0026] By selecting the image sequence that shows the passage of the front end of the sheet or the gripper bar through the field of view of the high-speed camera, it is possible to identify problems specifically in the phase in which the sheet is picked up in the register device and transported to the gripper bar.

[0027] Preferably, at least two different image sequences with the same relationship to the timeline of the cycles are displayed, so that an operator can very easily compare two sequences of the sheet received in the register device and the transfer to the gripper bar.

[0028] 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.

[0029] 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 feed station of the machine Fig. 1 in a front view, Fig. 5 a perspective view of the feed station of the machine Fig. 1 used register device, and Fig. 6 the punching machine according to the invention in a perspective view.

[0030] 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.

[0031] The process of producing the pre-cut flat boxes (hereinafter referred to as "cutouts 14") consists of cutting out shapes from flat cardboard sheets 10 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.

[0032] 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.

[0033] On the feed table 19, the sheets 12 are aligned by a register device 50 (described in 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.

[0034] 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.

[0035] To achieve a high throughput of approximately three large arcs 12 per second, the time required to transfer an arc 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 arc 12 reaches this speed as quickly as possible, while also requiring strong deceleration so that the arc 12 can be transported at this high speed for as long as possible.

[0036] Two phases of the transport cycle of the sheets 12 are critical: the high-speed phase and the rapid deceleration phase. Furthermore, the transfer of the sheets 12 from the feed table to the gripper bar 20 is critical.

[0037] Due to the high speed at which the sheets 12 are picked up 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 ejection station 34 where deviations of the sheet 12 from the expected travel path are critical. This will now be demonstrated using the Fig. 3 to 5 explained.

[0038] In Fig. Figure 3 shows a bow 12 being transported at high speed along a conveyor track by the gripper bar 20 immediately before the ejection station 34. Due to the high speed, the bow 12 is wavy.

[0039] Immediately after entering the discharge station 34, the gripper bar 20 releases the sheet 12. More precisely, since the blanks have already been removed, the remainder of the sheet is released, sometimes referred to as waste, grid, or matrix. For simplicity, the term "grid" will be used below to refer to the remainder of the sheet from which blanks have been cut and which is transported by the gripper bar 20 to the discharge station 34.

[0040] In Fig. Figure 4 shows a high-speed camera 44, which is assigned to the feed station 18.

[0041] The high-speed camera 44 is mounted on a machine frame 46, preferably centrally above the travel path of the sheet 12. Its field of view is directed towards the center of the feed table 19 and the gripper bar 20.

[0042] 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 with the approach of an arc to a Fig. 5 Register device shown 50.

[0043] The register device 50 comprises movable teeth 52 which can interact with projecting parts of a movable tray 54. The tray 54 is mounted on a carrier 56 which, during operation, performs a back-and-forth movement from a rear position, in which a sheet 12 is picked up, to a front position, in which the sheet 12 is to be transferred or handed over to the gripper bar 20.

[0044] To position each sheet 12 individually with respect to the gripper bar 20, the support 54 can be moved both in the direction of travel of the sheets 12 and transversely to it, so that despite tolerances in the position in which each sheet 12 is picked up between the teeth 52 and the support 54, the leading end of each sheet 12 is fed to the gripper bar 20 in exactly the same position. The register device 50 as such is known as the "power register".

[0045] The camera 44 can easily measure the position of the arch 12 recorded between the teeth 52 and the tray 54 by performing a line detection between the teeth 52 of the register device 50.

[0046] In the Fig. In the embodiment shown in Figure 6, the camera 44 can also view the feed table 19 through a window 59. In this embodiment, the lighting is arranged above the sheet 12 but below the window 59 to avoid reflections, provided that additional lighting is arranged outside the frame to illuminate the feed table 19. The camera 44 can capture the center of the sheet 12 through the window 59.

[0047] The high-speed camera 44 is connected to a memory 62 for storing the recorded images of the arc 12.

[0048] 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.

[0049] Additional elements of machine 10 are a control unit 64 and a display 66, which are located in Fig.5 are shown schematically.

[0050] The control unit 64 includes an image processing system 67.

[0051] When the machine 10 is in operation, the high-speed camera 44 records images of the edge sections 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 displayed to an operator in slow motion.

[0052] 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.

[0053] 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.

[0054] The captured images are processed to precisely identify the edge of the arc. Once edge E has been identified, a parameter is extracted that measures the maximum curvature of the edge.

[0055] For each parameter determined by evaluating the images, a threshold value is stored in the control unit 64. This threshold value is set on the basis of empirical data that relate certain curvatures to operational aspects, such as the speed of belt 40.

[0056] If the parameter calculated by controller 64 exceeds the predefined threshold, controller 64 determines that a critical condition exists. Controller 64 then triggers a countermeasure.

[0057] A first example of a countermeasure is that the controller 64 retrieves the relevant video segment from the buffer 62 and displays the sequence from the last partial frames of the recorded images on the display 66 to show the operator the condition of the edges of the last arc. The extracted video is presented to the operator in slow motion. The slow-motion playback allows the operator to examine the deformation in detail, which is not possible at normal operating speeds.

[0058] The video sequence allows an experienced operator to decide on appropriate adjustments to the die-cutting machine's settings to avoid the observed problems. This not only improves output quality but also reduces machine downtime, as problems can be resolved more quickly. Specifically, once the position of the sheet causing the problem is known, the operator can adjust machine components such as brushes, blades, blowers, and wheels.

[0059] There are additional countermeasures that the control unit 64 can either initiate automatically or propose to the operator for approval.

[0060] 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.

[0061] Alternatively, the display 66 can show the operator a message that the current transport speed is causing problems in the steps for picking up the sheets 12 in the register device 50 and in the transfer to the gripper bars 20, and that the speed should be reduced.

[0062] 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] A 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 track (TP), wherein the machine (10) has a recording system (42) with at least one high-speed camera (44) assigned to the feed side for recording several images of a representative section of the sheets (12) transported along the transport track (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 adjacent to a feed station (18) of the machine (10). [6] Machine (10) according to claim 5, wherein the high-speed camera (44) is arranged on a machine frame and is aligned with a register device of the feed station (18). [7] 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. [8] Machine (10) according to one of the preceding claims, wherein a window (59) is provided through which the camera (44) can receive the sheet (12) on the feed side of the machine (10). [9] 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. [10] Machine according to claim 9, wherein the image sequence is selected to show the transition of a front end of a sheet from a register device to a gripper bar (20) in the field of view of the high-speed camera (44). [11] Machine according to claim 9 or 10, wherein at least two different image sequences with the same relationship to the timeline of cycles are displayed.

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