Coiled material double-side alignment printing system

Abstract

A double-sided alignment printing system for coiled materials comprises a printing platform, a paper conveying mechanism, a light source, an industrial camera and a controller. The printing method comprises the following steps: (1) making a makeup file; (2) printing on the first surface of the coiled material; (3) printing on the second surface of the coiled material; the coiled material subjected to second surface printing passes through the space between the light source and the industrial camera, and the first alignment identification symbol and the second alignment identification symbol are displayed on the same surface of the coiled material after being irradiated by the light source; the industrial camera photographs the display areas of the first alignment identification symbol and the second alignment identification symbol, the controller processes the image and then calculates the coordinate deviation value between the first alignment identification symbol and the second alignment identification symbol, and whether the paper conveying speed is adjusted or not is determined after the coordinate deviation value is compared with a preset tolerance value. According to the invention, the position error between the image-text on the second surface and the image-text on the first surface can be controlled within an allowable error range, so that the image-texts on the two surfaces are accurately aligned.

Description

Technical Field

[0001] This invention relates to the field of printing technology, and more specifically, to a roll-to-roll double-sided alignment printing system. Background Technology

[0002] Currently, ordinary roll-to-roll printers used in the graphic arts, advertising, and imaging industries can only print on one side. However, there is a significant market demand for double-sided printing products. To achieve printing on both sides of a roll of paper, the solution is to first print the image on the first side (e.g., the front) and then print on the second side (e.g., the back), thus achieving double-sided printing. Double-sided printing products typically require accurate alignment of the image on both sides of the roll. However, current roll-to-roll printers on the market have an error (approximately ±0.2%) in the length direction. If this error is not corrected in time, a large cumulative error will occur after printing a considerable length, resulting in a significant positional error between the image on the second side and the image on the first side. If this error exceeds the allowable error range, defective or scrap products will be produced. For example, a 30-meter roll of paper, after being assembled and printed, may have an error of about 0.2% when printing the second side after the first side is printed. The error between the two sides will be 2 mm when printing the first meter of the second side, and the cumulative error will reach 4 mm when printing the second meter of the second side; and so on, reaching a cumulative error of 60 mm when printing the last meter of the second side. Therefore, to ensure product quality, errors should be reduced or eliminated promptly when printing the second side, keeping the positional error within the allowable range, so that the text and images on the second side are accurately aligned with those on the first side.

[0003] Chinese invention patent application CN106739546A discloses a double-sided printer, comprising: a frame, a feed roller, a take-up roller, a first printing platform, a vision recognition device, a second printing platform, and a control box. The feed roller and take-up roller are mounted on the same side of the frame. The first and second printing platforms are arranged in the same direction. The first printing platform prints position coordinate graphics and a target pattern on the first side of the material it passes over, and the second printing platform prints position coordinate graphics and a target pattern on the second side of the material it passes over. The vision recognition device is located in front of the feed end of the second printing platform and is used to detect the position coordinate graphics, obtain the coordinate offset, and send it to the control box. The control box is located inside the frame and is used to adjust the printing start position of the second printing platform according to the coordinate offset to print on the second side of the material it passes over.

[0004] When the aforementioned duplex printer is operating, one side of the printing material is printed by the first printing platform (also known as the front printing platform), printing the position coordinate graphic and the target pattern (or finished image). A visual recognition device detects the position coordinate graphic printed by the first printing platform, first determining the image's correctness. Once the position coordinate graphic is detected as correct, the device accurately positions the initial position of the image, obtains the coordinate offset, and sends this offset to the control box. The control box adjusts the starting position of the second printing platform based on the coordinate offset, printing the second side of the printing material. Specifically, the printer's central processing unit in the control box calculates the coordinate offset, determining the lateral and longitudinal changes of the soft material, calculating the material's deviation on both sides and its elasticity, thus understanding the material's deformation value. This generates a control signal that the PLC controller controlling the second printing platform can recognize, and sends it to the PLC controller to control the starting position of the second printing platform, printing on the other side of the printing material. After each print is completed, the visual recognition device rereads the position coordinate graphic to confirm the actual fabric feeding accuracy and the accuracy of the position coordinate graphic, making real-time adjustments to ensure the precise alignment of the entire roll of material and the accuracy of the printed length. The aforementioned duplex printer uses a visual recognition device to detect the position coordinate graphic, obtains the coordinate offset based on the graphic, adjusts the printing start position of the second printing platform, and adjusts the second printing platform's start position according to the printing position of the first side and the real-time status of the printed material, thus ensuring precise alignment during duplex printing.

[0005] However, when printing the second side of the printed material, the aforementioned duplex printer adjusts the starting position of the second printing platform based on the coordinate offset of the first side. This method ensures relatively accurate duplex printing alignment when the continuous length of each target image is small. However, when the continuous length of the target image is large, if only the starting position of the second printing platform is adjusted before printing the second side, a significant positional deviation will occur at the rear end of the target image after printing (for example, the Qingming Scroll, which is approximately 528 cm long, will show a positional deviation of about 10 mm at the rear end after printing). The larger the continuous length of the target image, the greater the positional deviation at the rear end, resulting in inaccurate alignment between the two sides. Furthermore, if the first printing platform prints a position coordinate graphic at regular intervals on the first side of the printed material, and the continuous length of the target image on the second side exceeds the interval between two adjacent position coordinate graphics, printing the second side in the above manner will continuously update the starting position based on the position coordinate graphics of the first side during the printing process, causing discontinuities in the target image. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a roll-to-roll double-sided alignment printing system. This system can print images and text on both the first and second sides of the roll-to-roll material, controlling the positional error between the images and text on the second side and the first side within an allowable range. This ensures accurate alignment between the images and text on the second side and the first side, guaranteeing product quality. The technical solution adopted is as follows: A roll-to-roll duplex printing system includes a printing platform, a paper feeding mechanism, an industrial camera, and a controller. The industrial camera is electrically connected to the corresponding input terminal of the controller. The system is characterized by further including a light source, and the controller is equipped with a machine vision system. Based on the aforementioned roll-to-roll double-sided alignment printing system, roll-to-roll double-sided alignment printing is achieved according to the following steps: (1) Create a layout file: Lay out the first target images and texts to be printed on the first page, and add multiple first alignment identification symbols to form a first layout file; Lay out the second target images and texts to be printed on the second page, and add multiple second alignment identification symbols to form a second layout file; In the first imposition file, each first alignment identification symbol is arranged sequentially along the paper feeding direction. In the second imposition file, each second alignment identification symbol is arranged sequentially along the paper feeding direction. The number of second alignment identification symbols is the same as that of first alignment identification symbols, and their positions correspond one-to-one. (2) The paper feeding mechanism feeds the roll material, and the printing platform prints each first target graphic and the first alignment identification symbol on the first side of the roll material according to the first layout file; (3) After the first side of the roll is printed, the paper feeding mechanism delivers the roll, and the printing platform prints the second target graphics and the second alignment identification symbol on the second side of the roll according to the second layout file; the roll that has been printed on the second side passes between the light source and the industrial camera, and after being illuminated by the light source, the first alignment identification symbol and the second alignment identification symbol are both displayed on the same side of the roll; the industrial camera takes pictures of the display area of ​​the first alignment identification symbol and the second alignment identification symbol, and transmits the acquired image to the controller; after processing the image, the controller obtains the coordinates of the first alignment identification symbol and the second alignment identification symbol, calculates the coordinate deviation value between the first alignment identification symbol and the second alignment identification symbol, and then compares the coordinate deviation value with the preset tolerance value; If the coordinate deviation exceeds the preset tolerance value, the controller sends a control signal to adjust the paper feeding speed; if the coordinate deviation is within the preset tolerance value, the current paper feeding speed is maintained.

[0007] The aforementioned paper feeding mechanism is used for conveying rolls (i.e., paper rolls), and the paper feeding speed refers to the speed at which the paper feeding mechanism conveys the rolls (i.e., paper rolls).

[0008] As the roll material passes between the light source and the industrial camera, the first alignment mark (or second alignment mark) on the side of the roll material facing the camera can be captured by the camera. The light source illuminates the roll material from one side, allowing the light to pass through and clearly reveal the second alignment mark (or first alignment mark) on the side of the roll material facing away from the camera; this second alignment mark can also be captured by the camera. Thus, under the illumination of the light source, both the first and second alignment marks are displayed on the side of the roll material facing the camera, allowing the camera to simultaneously capture both (and these marks are also visible to the naked eye of the operator).

[0009] In the display area of ​​the first and second alignment identification symbols (the area captured by the industrial camera), if the second alignment identification symbol lags behind the first alignment identification symbol in the paper feeding direction, it means that the paper feeding speed on the second side of the roll is too high relative to the printing speed of the printing platform. If it exceeds the allowable range, the paper feeding speed should be reduced. If the second alignment identification symbol leads the first alignment identification symbol in the paper feeding direction, it means that the paper feeding speed is too low relative to the printing speed of the printing platform. If it exceeds the allowable range, the paper feeding speed should be increased.

[0010] The coordinate deviation between the first and second alignment symbols can be positive or negative. A positive deviation indicates whether the paper feed speed is too high or too low when printing the second side of the roll. This should be determined in conjunction with the paper feed direction of the roll at the location of the industrial camera. For example, if the paper feed direction is from top to bottom at the location of the industrial camera, and the camera is directly shooting at the display area of ​​the first and second alignment symbols, then a positive deviation indicates that the paper feed speed is too low when printing the second side of the roll (in this case, the second alignment symbol is below the first alignment symbol and is ahead of it in the paper feed direction). A negative deviation indicates that the paper feed speed is too high when printing the second side of the roll (in this case, the second alignment symbol is above the first alignment symbol and is behind it in the paper feed direction). After adjusting the paper feed speed, maintain that speed until the next time the coordinate deviation value is determined to exceed the preset tolerance value. In this way, by adjusting the paper feed speed when printing the second side of the roll, the coordinate deviation value is basically controlled between the positive and negative values ​​of the preset tolerance value, thus keeping the positional error between the graphics on the second side and the graphics on the first side within the allowable error range. Since the preset tolerance value range is very small, the paper feed speed is only fine-tuned, the paper feed speed and printing speed are still basically matched, the printing length of each second target graphic changes slightly, and the printing quality of each second target graphic is basically unaffected.

[0011] Typically, by using mechanical structures to limit the transverse direction of the roll material (transverse direction refers to the direction perpendicular to the paper feeding direction), it can be ensured that the deviation of the printing area in the transverse direction is minimal and meets the requirements for alignment printing in the transverse direction. Therefore, by solving the alignment printing problem in the paper feeding direction, the graphics on the second side can be accurately aligned with the graphics on the first side.

[0012] The light intensity of the aforementioned light source is typically adjustable. Adjusting the light intensity based on the translucency of the roll material is ideal, ensuring that both the first and second alignment identification symbols are clearly visible on the side of the roll material facing the industrial camera. This allows the industrial camera to capture clear images of the areas where the first and second alignment identification symbols are visible. Generally, the lower the translucency of the roll material, the higher the light intensity of the light source. For roll materials of the same type, translucency decreases as the roll thickness increases.

[0013] Typically, the first alignment identification symbols are arranged at equal intervals along the paper feeding direction, and the second alignment identification symbols are arranged at equal intervals along the paper feeding direction. Preferably, the spacing between two adjacent first alignment identification symbols and the spacing between two adjacent second alignment identification symbols are both 20-100 cm.

[0014] Typically, the preset tolerance value is set within ±2 mm, preferably ±0.2 mm to ±2 mm (e.g., ±1 mm, ±0.5 mm, ±0.2 mm). The smaller the spacing between two adjacent first alignment symbols (the spacing between two adjacent second alignment symbols), the smaller the preset tolerance value can be set.

[0015] Typically, during the printing process on the first side of the roll material, the paper feeding speed of the paper feeding mechanism remains constant, meaning there is no need to adjust the paper feeding speed.

[0016] In one specific scheme, the same printing platform and paper feeding mechanism are used to print the first and second sides of the roll material; after the roll material is installed, the paper feeding mechanism delivers the roll material, the printing platform prints on the first side of the roll material and rewinds it; after the first side is printed, the rewound roll material is installed, and then the same paper feeding mechanism delivers the roll material, and the printing platform prints on the second side of the roll material.

[0017] In another specific scheme, a first printing platform is used to print the first side of the roll material, and a second printing platform is used to print the second side of the roll material. After the roll material is installed, the first paper feeding mechanism delivers the roll material, and the first printing platform prints on the first side of the roll material and rewinds it. After the first side is printed, the rewound roll material is installed, and then the second paper feeding mechanism delivers the roll material, and the second printing platform prints on the second side of the roll material.

[0018] In another specific embodiment, a first printing platform is used to print the first side of the roll material, and a second printing platform is used to print the second side. A paper feeding mechanism sequentially transports the roll material to the first and second printing platforms. After the roll material is installed, the paper feeding mechanism transports the roll material, and the first printing platform prints on the first side. Subsequently, the paper feeding mechanism transports the roll material to the second printing platform, where it prints on the second side. Since the paper feeding speed at the first and second printing platforms may differ, a roll material storage device can be installed between the two printing platforms to prevent interference. The roll material storage device can refer to a storage device disclosed in authorization announcement number CN206751027U. After the roll material comes out from the first printing platform, it passes through the roll material storage device and is then sent to the second printing platform. When the paper feeding speed of the roll material when it passes through the first printing platform is greater than the paper feeding speed when it passes through the second printing platform, the length of the roll material stored in the roll material storage device (i.e., the roll material wound between each moving guide roller and each fixed guide roller) gradually increases. When the paper feeding speed of the roll material when it passes through the first printing platform is less than the paper feeding speed when it passes through the second printing platform, the length of the roll material stored in the roll material storage device (i.e., the roll material wound between each moving guide roller and each fixed guide roller) gradually decreases.

[0019] In a preferred embodiment, the paper feeding mechanism is electrically connected to the corresponding output terminal of the controller; in step (3), if the coordinate deviation value exceeds the range of the preset tolerance value, the controller sends a control signal to the paper feeding mechanism to adjust the paper feeding speed. This solution is suitable for situations where the printing platform only has printing functions.

[0020] Typically, the aforementioned paper feeding mechanism includes an unwinding mechanism, a roll traction mechanism, and a rewinding mechanism. The roll traction mechanism is located between the unwinding and rewinding mechanisms. The unwinding mechanism is used to mount the roll of paper, the rewinding mechanism is used to rewind the printed roll of paper, and the roll traction mechanism is used to pull and transport the roll of paper. The roll traction mechanism is electrically connected to the corresponding output terminal of the controller, and the speed at which the roll of paper is transported by the roll traction mechanism is the paper feeding speed. In addition, the aforementioned paper feeding mechanism may also include several guide rollers, each guide roller located between the unwinding and rewinding mechanisms, for guiding the transport of the roll of paper.

[0021] As a first preferred embodiment of the roll material traction mechanism, the aforementioned roll material traction mechanism includes a servo motor, an active paper feed roller, and a pressure roller. The power output shaft of the servo motor is connected to the active paper feed roller. The roll material passes between the pressure roller and the active paper feed roller, and the pressure roller and the active paper feed roller together clamp the roll material. The servo motor's power output shaft drives the active paper feed roller to rotate, thus conveying the roll material. The servo motor is electrically connected to the corresponding output terminal of the controller. The paper feeding speed is adjusted by regulating the rotational speed of the servo motor's power output shaft. Fine-tuning of the paper feeding speed can be achieved by fine-tuning the rotational speed of the servo motor's power output shaft. The servo motor's power output shaft can be connected to one end of the active paper feed roller via a coupling, or it can be connected to the active paper feed roller via a transmission mechanism (such as a synchronous belt or gear set).

[0022] As a second preferred embodiment of the roll material traction mechanism, the aforementioned roll material traction mechanism includes a servo motor, an active paper feed roller, and multiple pressure rollers. The power output shaft of the servo motor is connected to the active paper feed roller. The roll material passes between the pressure rollers and the active paper feed roller, and the pressure rollers and the active paper feed roller together clamp the roll material. The servo motor's power output shaft drives the active paper feed roller to rotate, thus conveying the roll material. The servo motor is electrically connected to the corresponding output terminal of the controller. The paper feeding speed is adjusted by regulating the rotational speed of the servo motor's power output shaft. Fine-tuning of the paper feeding speed can be achieved by fine-tuning the rotational speed of the servo motor's power output shaft. The servo motor's power output shaft can be connected to one end of the active paper feed roller via a coupling, or it can be connected to the other end of the active paper feed roller via a transmission mechanism (such as a synchronous belt or gear set).

[0023] In another preferred embodiment, the printing platform employs a printer with a built-in adjustable-speed paper feeding mechanism and a touchscreen. The paper feeding speed of the built-in paper feeding mechanism can be adjusted by operating the touchscreen. The roll-to-roll duplex printing system also includes a robotic arm capable of operating the touchscreen. The robotic arm is electrically connected to the corresponding output of the controller. When paper feeding speed adjustment is required, the robotic arm, under the control of the controller, operates the touchscreen to set the adjustment range. The touchscreen transmits the setting information to the printer's built-in controller, which then sends control signals to its built-in paper feeding mechanism to adjust the paper feeding speed. This method is suitable for modifying printers with built-in adjustable-speed paper feeding mechanisms (such as the Canon PRO-526) to form the roll-to-roll duplex printing system of this invention, which helps to fully utilize existing equipment and reduce equipment costs.

[0024] The machine vision system installed on the aforementioned controller typically includes an image acquisition program and an image processing program. After acquiring the image transmitted from the industrial camera, the controller processes the image, obtains image information, and calculates the coordinates (usually X and Y coordinates, where the Y coordinate is the vertical coordinate (i.e., the coordinate in the paper feeding direction) and the X coordinate is the horizontal coordinate (i.e., the coordinate in the direction perpendicular to the paper feeding direction)) of the first and second alignment symbols. Image information typically includes image size, shape, center point position, etc.

[0025] Typically, the industrial camera is positioned directly above the display area of ​​the first and second alignment identification symbols when taking a picture. To facilitate subsequent image processing, the Y-axis of the industrial camera is parallel to the paper feeding direction, and the X-axis is parallel to the surface of the display area and perpendicular to the Y-axis.

[0026] The aforementioned controller can be an industrial computer.

[0027] The aforementioned first alignment identification symbol includes at least one first alignment image block, and the second alignment identification symbol includes at least one second alignment image block. The aforementioned first and second alignment image blocks can be circular, rectangular, triangular, or cross-shaped blocks, or blocks of other shapes. Taking a circular image block as an example, the image information typically includes the size, roundness, and center position of the circle, and the coordinates of the first and second alignment identification symbols are determined by the center position.

[0028] In one specific embodiment, the second alignment identification symbol consists of two second alignment blocks, and the first alignment identification symbol consists of one first alignment block. When the second alignment identification symbol corresponds to the first alignment identification symbol, the two second alignment blocks are located on either side of the first alignment block. After illumination by a light source, the central first alignment block and the second alignment blocks on the left and right sides can be seen on the side of the roll facing the industrial camera. The industrial camera can simultaneously capture the central first alignment block and the second alignment blocks on the left and right sides.

[0029] In another specific embodiment, the second alignment identification symbol consists of one second alignment image block, and the first alignment identification symbol consists of two first alignment image blocks. When the second alignment identification symbol corresponds to the first alignment identification symbol, the two first alignment image blocks are located on either side of the second alignment image block. After being illuminated by a light source, the middle second alignment image block and the first alignment image blocks on the left and right sides can be seen on the side of the roll material facing the industrial camera. The industrial camera can simultaneously capture the middle second alignment image block and the first alignment image blocks on the left and right sides.

[0030] This invention continuously compares the position and deviation of the images on both sides during the printing process of the second side, and adjusts accordingly to reduce the deviation, achieving a double-sided alignment effect. Regardless of the continuous length of the target pattern, the solution of this invention ensures that the positional error between the images on the second side and the first side remains within an acceptable range.

[0031] The roll-to-roll double-sided alignment printing system of the present invention can print images and text on the first and second sides of the roll-to-roll material respectively. During the printing process of the images and text on the second side, the system continuously monitors the positional deviation between the images and text on the second side and the images and text on the first side. When the positional deviation is too large, the system adjusts the paper feeding speed to reduce the positional deviation, thereby controlling the positional error between the images and text on the second side and the images and text on the first side within the allowable error range. This ensures that the images and text on the second side are accurately aligned with the images and text on the first side, thus ensuring product quality. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the roll-to-roll double-sided alignment printing system in preferred embodiment 1 of the present invention; Figure 2 This is a partial schematic diagram of the first layout file in the preferred embodiment 1 of the present invention; Figure 3 This is a partial schematic diagram of the second layout file in the preferred embodiment 1 of the present invention; Figure 4 This is an image obtained by taking pictures of the display areas of the first alignment identification symbol and the second alignment identification symbol by an industrial camera in the preferred embodiment of the present invention, as well as a schematic diagram of the coordinates of each alignment identification symbol. Figure 5 This is a schematic diagram of the cooperation between the robotic arm and the touch screen in the preferred embodiment 3 of the present invention; Figure 6 This is a schematic diagram showing the changes in the touchscreen's user interface in a preferred embodiment 3 of the present invention; Figure 7 This is a schematic diagram of the pressing device in the preferred embodiment 3 of the present invention. Detailed Implementation

[0033] Example 1, such as Figure 1 As shown, this roll-to-roll duplex printing system includes a printing platform 1, a paper feeding mechanism 2, a light source 3, an industrial camera 4, and a controller (not shown). The industrial camera 4 is electrically connected to the corresponding input terminal of the controller, and the controller is equipped with a machine vision system. The controller uses an industrial computer.

[0034] The paper feeding mechanism 2 includes an unwinding mechanism 21, a roll traction mechanism 22, and a rewinding mechanism 23. The roll traction mechanism 22 is located between the unwinding mechanism 21 and the rewinding mechanism 23. The unwinding mechanism 21 is used to install the roll 5, the rewinding mechanism 23 is used to rewind the printed roll 5, and the roll traction mechanism 22 is used to traction and transport the roll 5. The speed at which the roll traction mechanism 22 transports the roll is the paper feeding speed. In this embodiment, the roll material traction mechanism 22 includes a servo motor 221, an active paper feed roller 222, and a pressure roller 223. The power output shaft of the servo motor 221 is connected to the active paper feed roller 222. The roll material 5 passes between the pressure roller 223 and the active paper feed roller 222, and the pressure roller 223 and the active paper feed roller 222 together clamp the roll material 5. The power output shaft of the servo motor 221 drives the active paper feed roller 222 to rotate, thus conveying the roll material. The servo motor 221 is electrically connected to the corresponding output terminal of the controller. The paper feeding speed is adjusted by regulating the rotation speed of the power output shaft of the servo motor 221. By fine-tuning the rotation speed of the power output shaft of the servo motor 221, the paper feeding speed can be fine-tuned. The power output shaft of the servo motor 221 can be connected to one end of the active paper feed roller 222 via a coupling, or it can be connected to one end of the active paper feed roller 222 via a transmission mechanism (such as a synchronous belt or gear set).

[0035] The paper feeding mechanism 2 also includes several guide rollers 24 (e.g. Figure 1 The paper feeding mechanism shown includes two guide rollers 24, each guide roller 24 being located between the unwinding mechanism 21 and the winding mechanism 23, for guiding the feeding of the roll material 5.

[0036] Based on the above roll-to-roll double-sided alignment printing system, roll-to-roll double-sided alignment printing is achieved according to the following steps: (1) Creating the layout file: Refer to Figure 2 The first target images 61 to be printed on the first page are assembled, and multiple first alignment identification symbols 62 are added to form the first assembly file 6; (Refer to...) Figure 3 The second target images 71 that need to be printed on the second side are assembled, and multiple second alignment identification symbols 72 are added to form a second assembly file 7; In the first layout file 6, each of the first alignment identification symbols 62 is arranged sequentially along the paper feeding direction. In the second layout file 7, each of the second alignment identification symbols 72 is arranged sequentially along the paper feeding direction. The number of the second alignment identification symbols 72 is the same as that of the first alignment identification symbols 62, and their positions correspond one-to-one. (2) The paper feeding mechanism 2 feeds the roll 5, and the printing platform 1 prints each first target graphic 61 and the first alignment identification symbol 62 on the first surface of the roll according to the first layout file 6 (during the printing platform 1 printing on the first surface of the roll 5, the paper feeding speed of the paper feeding mechanism 2 remains unchanged, that is, there is no need to adjust the paper feeding speed). (3) After the first side of the roll 5 is printed, the paper feeding mechanism 2 feeds the roll 5, and the printing platform 1 prints the second target graphics 71 and the second alignment identification symbol 72 on the second side of the roll 5 according to the second imposition file 7. The roll 5, which has been printed on the second side, passes between the light source 3 and the industrial camera 4. After being illuminated by the light source 3, the first alignment identification symbol 62 and the second alignment identification symbol 72 are both displayed on the same side of the roll 5. The industrial camera 4 takes pictures of the display area of ​​the first alignment identification symbol 62 and the second alignment identification symbol 72 and transmits the acquired image to the controller. After processing the image, the controller obtains the coordinates of the first alignment identification symbol 62 and the second alignment identification symbol 72, calculates the coordinate deviation value between the second alignment identification symbol 72 and the first alignment identification symbol 62, and then compares the coordinate deviation value with the preset tolerance value. If the coordinate deviation value exceeds the range of the preset tolerance value, the controller sends a control signal to adjust the paper feeding speed. If the coordinate deviation value is within the range of the preset tolerance value, the current paper feeding speed is maintained.

[0037] In this embodiment, the paper feeding mechanism 2 is electrically connected to the corresponding output terminal of the controller; in step (3), if the coordinate deviation value exceeds the range of the preset tolerance value, the controller sends a control signal to the paper feeding mechanism 2 to adjust the paper feeding speed.

[0038] In this embodiment, the same printing platform 1 and paper feeding mechanism 2 are used to print the first and second sides of the roll 5. After the roll 5 is installed, the paper feeding mechanism 2 feeds the roll 5, and the printing platform 1 prints on the first side of the roll 5 and rewinds it. After the first side is printed, the rewound roll 5 is installed, and the paper feeding mechanism 2 feeds the roll 5 again, and the printing platform 1 prints on the second side of the roll 5.

[0039] In this embodiment, when the roll 5 passes between the light source 3 and the industrial camera 4 (typically, the portion of the roll 5 with the second alignment identification symbol 72 printed on it passes between the light source 3 and the industrial camera 4), the second side of the roll 5 faces the industrial camera 4, and the first side of the roll 5 faces the light source 3. The second alignment identification symbol 72 on the side of the roll 5 facing the industrial camera 4 can be captured by the industrial camera 4. The light source 3 illuminates the roll 5, and the light passes through the roll 5, making the first alignment identification symbol 62 on the side of the roll 5 facing away from the industrial camera 4 clearly visible and also visible by the industrial camera 4. Thus, when illuminated by the light source 3, both the first alignment identification symbol 62 and the second alignment identification symbol 72 are visible on the side of the roll facing the industrial camera 4, and the industrial camera 4 can simultaneously capture both the first alignment identification symbol 62 and the second alignment identification symbol 72.

[0040] In this embodiment, the first alignment identification symbols 62 are arranged at equal intervals along the paper feeding direction, and the second alignment identification symbols 72 are arranged at equal intervals along the paper feeding direction. The spacing between two adjacent first alignment identification symbols 62 is equal to the spacing between two adjacent second alignment identification symbols 72, both being 20-100 cm (e.g., 50 cm).

[0041] The first alignment identification symbol includes at least one first alignment block, and the second alignment identification symbol includes at least one second alignment block. The first and second alignment blocks can be circular, rectangular, triangular, or cross-shaped blocks, or other shapes. (Reference) Figure 2 and Figure 3 In this embodiment, the second alignment identification symbol 72 is composed of two second alignment blocks 721, and the first alignment identification symbol 62 is composed of one first alignment block 621. The first alignment block 621 and the two second alignment blocks 721 are all circular blocks (the diameter of the three circular blocks in the imposition file is the same, for example, they can all be 1mm; during imposition, the coordinates of the two second alignment blocks 721 in the paper feeding direction are consistent). When the second alignment identification symbol 72 corresponds to the position of the first alignment identification symbol 62, the two second alignment blocks 721 are respectively located on both sides of the first alignment block 621. After being illuminated by the light source 3, the first alignment block 621 in the middle and the second alignment blocks 721 on the left and right sides can be seen on the side of the roll 5 facing the industrial camera 4. The industrial camera 4 can simultaneously capture the first alignment block 621 in the middle and the second alignment blocks 721 on the left and right sides.

[0042] The machine vision system installed on the controller includes image acquisition and image processing programs. After acquiring images transmitted from the industrial camera, the controller processes the images, obtains image information, and calculates the coordinates (including X and Y coordinates, where the Y coordinate is the vertical coordinate (i.e., the coordinate in the paper feeding direction) and the X coordinate is the horizontal coordinate (i.e., the coordinate in the direction perpendicular to the paper feeding direction) of the first and second alignment symbols. Image information may include image size, shape, center point position, etc.

[0043] When the industrial camera 4 takes a picture, it faces the display area of ​​the first alignment identification symbol 62 and the second alignment identification symbol 72. The Y-axis of the industrial camera 4 is parallel to the paper feeding direction, and the X-axis is parallel to the surface of the display area and perpendicular to the Y-axis. In this embodiment, at the location of the industrial camera 4, the paper feeding direction of the roll 5 is from top to bottom. The industrial camera 4 is directly facing the display area of ​​the first alignment identification symbol 62 and the second alignment identification symbol 72. A positive coordinate deviation value indicates that the paper feeding speed is too low when printing the second side of the roll (at this time, the second alignment identification symbol 72 is below the first alignment identification symbol 62 and is ahead of the first alignment identification symbol 62 in the paper feeding direction). A negative coordinate deviation value indicates that the paper feeding speed is too high when printing the second side of the roll (at this time, the second alignment identification symbol 72 is above the first alignment identification symbol 62 and is behind the first alignment identification symbol 62 in the paper feeding direction). After adjusting the paper feeding speed, this paper feeding speed is kept constant until the next time the coordinate deviation value is determined to exceed the preset tolerance value.

[0044] refer to Figure 4 After the industrial camera 4 takes pictures of the display areas of the first alignment identification symbol 62 and the second alignment identification symbol 72, it obtains an image composed of three circles: the first alignment block 621 and the two second alignment blocks 721. The obtained photo contains three circles with a diameter of 1mm. The middle circle is the first alignment identification symbol 62 (displayed on the side of the roll facing the industrial camera when illuminated by a light source). The circles on the left and right sides together form the second alignment identification symbol 72 (the Y coordinates of the left and right circles are consistent when the roll is assembled). The controller processes the image to obtain information such as the size, roundness, and center position of the circles. It determines the coordinates of the first alignment block 621 and the two second alignment blocks 721 based on the center position, obtaining the center coordinates of the three circles (including X and Y coordinates, where the Y coordinate is the coordinate in the paper feeding direction and the X coordinate is the coordinate in the direction perpendicular to the paper feeding direction). The coordinates of the left point are A(x1,y1), the coordinates of the right point are B(x2,y2), and the coordinates of the middle point are P(x0,y0).

[0045] The machine vision system calculates the average value (y1+y2) / 2 of the Y-coordinates y1 and y2 of the centers of the two left and right circles. Then, it calculates the deviation of the Y-coordinate y0 of the center of the middle circle from this average value and compares it to a preset tolerance value. If the Y-coordinate of the center of the middle circle is greater than the average value, the deviation is positive; if the Y-coordinate is less than the average value, the deviation is negative. With the preset tolerance value set to ±1 mm, if the deviation exceeds the preset tolerance value (greater than 1 mm or less than -1 mm), a control signal is sent to the paper feeding mechanism to adjust the paper feeding speed, thereby adjusting the actual printing size of the second side of the roll material to achieve double-sided printing. If the deviation value does not exceed the preset tolerance value (i.e., -1 mm ≤ coordinate deviation ≤ 1 mm), the paper feeding speed is not adjusted.

[0046] If the Y-coordinate deviation is greater than 1 mm, it means the paper feeding speed is too low and needs to be increased; if the Y-coordinate deviation is less than -1 mm, it means the real-time paper feeding speed is too high and needs to be decreased.

[0047] Example 2 differs from Example 1 in that the method for calculating the coordinate deviation value is different. This is mainly because the industrial camera may tilt slightly when taking pictures, resulting in a slightly larger difference in the Y coordinates of the centers of the two circles.

[0048] In this embodiment, after the controller obtains the center coordinates of the three circles, the machine vision system draws a straight line passing through the centers of the left and right circles. The distance *d* from the center of the middle circle to this straight line is calculated as the coordinate deviation value and compared with a preset tolerance value (e.g., ±1 mm). If the coordinate deviation value exceeds the preset tolerance value (greater than 1 mm or less than -1 mm), a control signal is sent to the paper feeding mechanism to adjust the paper feeding speed, thereby adjusting the actual printing size of the second side of the roll material to achieve double-sided alignment printing. If the center of the middle circle is on the straight line, or the coordinate deviation value does not exceed the preset tolerance value, the paper feeding speed is not adjusted. When the center of the middle circle is above the straight line (at which point the second alignment identification symbol is ahead of the first alignment identification symbol in the paper feeding direction), the coordinate deviation value is positive; when the center of the middle circle is below the straight line (at which point the second alignment identification symbol is behind the first alignment identification symbol in the paper feeding direction), the coordinate deviation value is negative. At the location of the industrial camera, the paper feed direction of the roll is from top to bottom. If the Y-coordinate deviation is greater than 1 mm, it means that the paper feed speed is too low and should be increased. If the Y-coordinate deviation is less than -1 mm, it means that the real-time paper feed speed is too high and should be decreased.

[0049] The formula for calculating the distance d from the midpoint to the line passing through the left and right points is: Given that the coordinates of the left point are A(x1, y1), the coordinates of the right point are B(x2, y2), and the coordinates of the middle point are P(x0, y0), then the distance d from the middle point to the line passing through the left and right points is:

[0050] Example 3, Reference Figure 5 The printing platform uses a printer with a built-in adjustable paper feeding mechanism and a touch screen 8 (such as the Canon PRO-526). The paper feeding speed of the built-in paper feeding mechanism can be adjusted by operating the touch screen 8. The roll-to-roll duplex printing system in this embodiment also includes a robotic arm 9 capable of operating the touch screen. The robotic arm 9 is electrically connected to the corresponding output terminal of the controller. When the paper feeding speed needs to be adjusted, the robotic arm 9 operates the touch screen 8 under the control of the controller to set the adjustment range of the paper feeding speed. The touch screen 8 transmits the setting information of the paper feeding speed adjustment range to the printer's built-in controller, which then sends control signals to its built-in paper feeding mechanism to adjust the paper feeding speed. Compared with Embodiment 1, there is no need to set up a separate paper feeding mechanism 2. Furthermore, the adjustment of the paper feeding speed is performed by the printer's built-in controller, which performs image acquisition, image processing, and motion control of the robotic arm 9.

[0051] In this embodiment, the robotic arm 9 includes four pressing devices 91, 92, 93, and 94; (See reference...) Figure 7 Each pressing device includes a pressing block 911 and a pressing block position switching mechanism 912 (specifically, a pressing block position switching cylinder or a pressing block position switching electric cylinder) capable of driving the pressing block 911 to reciprocate. The pressing block 911 is mounted on the power output end of the pressing block position switching mechanism 912 (for example, mounted on the piston rod of the pressing block position switching cylinder or the push rod of the pressing block position switching electric cylinder). When the pressing block position switching mechanism 912 drives the pressing block 911 to reciprocate once, the pressing block 911 is pressed once on the operation interface of the touch screen 8.

[0052] In this embodiment, the robotic arm 9 is configured according to the characteristics of the touchscreen interface of the Canon PRO-526 printer. Four pressing devices 91, 92, 93, and 94 correspond to the areas on the touchscreen 8's interface that need to be pressed, simulating manual pressing operations on the touchscreen 8's interface. (Reference) Figure 6When it is necessary to adjust the paper feeding speed (increase or decrease), the process of the robotic arm 9 operating the touch screen 8 and the changes in the touch screen 8's operating interface is as follows: After the pressing device 91 clicks the "Maintenance" area 811 on the first interface 81, it enters the second operating interface 82; then, after the pressing device 92 clicks the "Paper Feed Fine Adjustment" area 821 on the second operating interface 82, it enters the third operating interface 83; then, the pressing device 93 presses the area 831 where the upward arrow is located on the third operating interface 83, or the pressing device 94 presses the area 832 where the downward arrow is located on the third operating interface 83, to set the adjustment range of the paper feeding speed (each time the pressing device 93 presses the upward arrow, the paper feeding speed increases by one unit; each time the pressing device 94 presses the downward arrow, the paper feeding speed decreases by one unit).

[0053] The aforementioned robotic arm can also employ other structures. For example, the robotic arm includes a pressing block and a pressing block position switching mechanism. The pressing block position switching mechanism includes a lifting mechanism, a lifting seat, a translation mechanism, and a translation seat. The lifting mechanism is mounted on a frame and can drive the lifting seat to move up and down. The translation mechanism is mounted on the lifting seat and can drive the translation seat to move horizontally. The pressing block is mounted on the translation seat. Alternatively, the pressing block position switching mechanism includes a translation mechanism, a translation seat, a lifting mechanism, and a lifting seat. The translation mechanism is mounted on a frame and can drive the translation seat to move horizontally. The lifting mechanism is mounted on the translation seat and can drive the lifting seat to move up and down. The pressing block is mounted on the lifting seat. In this configuration, the translation mechanism switches the pressing block's position in the horizontal direction, allowing the pressing block to reach directly above the corresponding position on the touchscreen; the lifting mechanism drives the pressing block to move up and down, thus realizing the action of pressing a button.

[0054] In other implementation schemes, a first printing platform is used to print the first side of the roll material, and a second printing platform is used to print the second side of the roll material. After the roll material is installed, a first paper feeding mechanism delivers the roll material, and the first printing platform prints on the first side of the roll material and then rewinds it. After the first side printing is completed, the rewound roll material is installed, and then the second paper feeding mechanism delivers the roll material, and the second printing platform prints on the second side of the roll material. This scheme is actually the same as the method used in Embodiment 1.

[0055] In other implementations, a first printing platform can be used to print the first side of the roll material, and a second printing platform can be used to print the second side. A paper feeding mechanism sequentially feeds the roll material to the first and second printing platforms. After the roll material is installed, the paper feeding mechanism feeds the roll material, and the first printing platform prints on the first side. Subsequently, the paper feeding mechanism feeds the roll material to the second printing platform, where it prints on the second side. Since the paper feeding speed at the first and second printing platforms may differ, a roll material storage device can be installed between the two printing platforms to prevent interference. The roll material storage device can refer to a storage device disclosed in authorization announcement number CN206751027U. After the roll material comes out from the first printing platform, it passes through the roll material storage device and is then sent to the second printing platform. When the paper feeding speed of the roll material when it passes through the first printing platform is greater than the paper feeding speed when it passes through the second printing platform, the length of the roll material stored in the roll material storage device (i.e., the roll material wound between each moving guide roller and each fixed guide roller) gradually increases. When the paper feeding speed of the roll material when it passes through the first printing platform is less than the paper feeding speed when it passes through the second printing platform, the length of the roll material stored in the roll material storage device (i.e., the roll material wound between each moving guide roller and each fixed guide roller) gradually decreases.

[0056] In other embodiments, the roll material traction mechanism may also include a servo motor, an active paper feed roller, and multiple pressure rollers. The power output shaft of the servo motor is connected to the active paper feed roller. The roll material passes between the pressure rollers and the active paper feed roller, and the pressure rollers and the active paper feed roller together clamp the roll material. The servo motor's power output shaft drives the active paper feed roller to rotate, thus conveying the roll material. The servo motor is electrically connected to the corresponding output terminal of the controller. The paper feeding speed is adjusted by regulating the rotational speed of the servo motor's power output shaft. Fine-tuning of the paper feeding speed can be achieved by fine-tuning the rotational speed of the servo motor's power output shaft. The servo motor's power output shaft can be connected to one end of the active paper feed roller via a coupling, or it can be connected to the active paper feed roller via a transmission mechanism (such as a synchronous belt or gear set).

Claims

1. A web double-sided alignment printing system, comprising a printing platform, a paper feeding mechanism, an industrial camera and a controller, the industrial camera is electrically connected with the corresponding input end of the controller, characterized in that Also include a light source, the controller is installed with a machine vision system; Based on the double-sided alignment printing system of the roll material, the double-sided alignment printing of the roll material is realized by the following steps: (1) Making a layout file: layout each first target image and text to be printed on the first side, and add a plurality of first alignment identification symbols to form a first layout file; Layout each second target image and text to be printed on the second side, and add a plurality of second alignment identification symbols to form a second layout file; Each first alignment identification symbol in the first layout file is arranged in sequence along the paper feeding direction, and each second alignment identification symbol in the second layout file is arranged in sequence along the paper feeding direction. The number of the second alignment identification symbols is the same as that of the first alignment identification symbols, and the positions of the second alignment identification symbols correspond to those of the first alignment identification symbols one by one; (2) The paper feeding mechanism transports the roll material, and the printing platform prints each first target image and text and the first alignment identification symbol on the first side of the roll material according to the first layout file; (3) After completing the printing on the first side of the roll material, the paper feeding mechanism transports the roll material, and the printing platform prints each second target image and text on the second side of the roll material according to the second layout file; the roll material that has been printed on the second side passes between the light source and the industrial camera, is irradiated by the light source, and the first alignment identification symbol and the second alignment identification symbol are both displayed on the same side of the roll material; the industrial camera photographs the display area of the first alignment identification symbol and the second alignment identification symbol, and transmits the obtained image to the controller; after processing the image, the controller obtains the coordinates of the first alignment identification symbol and the second alignment identification symbol, calculates the coordinate deviation value between the first alignment identification symbol and the second alignment identification symbol, and compares the coordinate deviation value with a preset tolerance value; If the coordinate deviation value exceeds the range of the preset tolerance value, the controller sends a control signal to adjust the paper feeding speed; if the coordinate deviation value is within the range of the preset tolerance value, the current paper feeding speed is maintained.

2. The web roll double-sided registration printing system of claim 1, wherein: Each first alignment identification symbol is arranged at equal intervals along the paper feeding direction, and each second alignment identification symbol is arranged at equal intervals along the paper feeding direction.

3. The web roll double-sided register printing system according to claim 1 or 2, characterized in that: The interval between the two adjacent first alignment identification symbols and the interval between the two adjacent second alignment identification symbols are both 20-100 cm.

4. The double-sided alignment printing system of the roll material according to claim 1 or 2, characterized in that: The same printing platform and paper feeding mechanism are used to print on the first side and the second side of the roll material; after the roll material is installed, the paper feeding mechanism transports the roll material, and the printing platform prints on the first side of the roll material and performs winding; after completing the printing on the first side, the wound roll material is installed, and the paper feeding mechanism transports the roll material, and the printing platform prints on the second side of the roll material; Alternatively, a first printing platform is used to print on the first side of the roll material, and a second printing platform is used to print on the second side of the roll material; After the roll material is installed, a first paper feeding mechanism transports the roll material, and a first printing platform prints on the first side of the roll material and performs winding; after completing the printing on the first side, the wound roll material is installed, a second paper feeding mechanism transports the roll material, and a second printing platform prints on the second side of the roll material; Alternatively, the first printing platform is used for printing the first surface of the roll material, and the second printing platform is used for printing the second surface of the roll material, and the paper feeding mechanism sequentially feeds the roll material to the first printing platform and the second printing platform; after the roll material is installed, the paper feeding mechanism feeds the roll material, the first printing platform prints on the first surface of the roll material; then the paper feeding mechanism feeds the roll material to the second printing platform, and the second printing platform prints on the second surface of the roll material.

5. The roll material double-sided alignment printing system according to claim 1 or 2, characterized in that: the paper feeding mechanism is electrically connected with the corresponding output end of the controller; in step (3), if the coordinate deviation value exceeds the range of the preset tolerance value, the controller sends a control signal to the paper feeding mechanism to adjust the paper feeding speed; the paper feeding mechanism comprises a roll unwinding mechanism, a roll material traction mechanism and a roll winding mechanism, the roll material traction mechanism is arranged between the roll unwinding mechanism and the roll winding mechanism, the roll unwinding mechanism is used for installing the roll material, the roll winding mechanism is used for winding the printed roll material, and the roll material traction mechanism is used for traction and feeding of the roll material; the roll material traction mechanism is electrically connected with the corresponding output end of the controller, and the speed of the roll material traction mechanism feeding the roll material is the paper feeding speed.

6. The roll material double-sided alignment printing system according to claim 5, characterized in that: the roll material traction mechanism comprises a servo motor, a driving paper feeding roller and a paper pressing roller, the power output shaft of the servo motor is in transmission connection with the driving paper feeding roller, the roll material passes between the driving paper feeding roller and the paper pressing roller, the driving paper feeding roller and the paper pressing roller clamp the roll material together, and the driving paper feeding roller rotates to feed the roll material when the power output shaft of the servo motor rotates; the servo motor is electrically connected with the corresponding output end of the controller, and the paper feeding speed is adjusted by adjusting the rotating speed of the power output shaft of the servo motor; alternatively, the roll material traction mechanism comprises a servo motor, a driving paper feeding roller and a plurality of paper pressing wheels, the power output shaft of the servo motor is in transmission connection with the driving paper feeding roller, the roll material passes between the driving paper feeding roller and the paper pressing wheels, the driving paper feeding roller and the paper pressing wheels clamp the roll material together, and the driving paper feeding roller rotates to feed the roll material when the power output shaft of the servo motor rotates; the servo motor is electrically connected with the corresponding output end of the controller, and the paper feeding speed is adjusted by adjusting the rotating speed of the power output shaft of the servo motor.

7. The web roll double-sided registration printing system of claim 1 or 2, wherein: the printing platform adopts a printer with an adjustable-speed paper feeding mechanism and a touch screen, and the paper feeding speed of the self-provided paper feeding mechanism can be adjusted by operating the touch screen; the roll material double-sided alignment printing system further comprises a mechanical hand capable of operating the touch screen, and the mechanical hand is electrically connected with the corresponding output end of the controller; when the paper feeding speed needs to be adjusted, the mechanical hand operates the touch screen under the control of the controller to set the adjustment range of the paper feeding speed, the touch screen transmits the setting information of the paper feeding speed adjustment range to the built-in controller of the printer, the built-in controller of the printer sends a control signal to the self-provided paper feeding mechanism to adjust the paper feeding speed.

8. The web roll double-sided registration printing system of claim 1 or 2, wherein: When the industrial camera takes a picture, the Y-axis direction thereof is parallel to the paper feeding direction, and the X-axis direction thereof is parallel to the surface of the display area and perpendicular to the Y-axis direction.

9. The web roll double-sided registration printing system of claim 1 or 2, wherein: The first alignment identification symbol comprises at least one first alignment block, and the second alignment identification symbol comprises at least one second alignment block.

10. The web double-sided alignment printing system of claim 9, wherein: The second alignment identification symbol comprises two second alignment blocks, and the first alignment identification symbol comprises one first alignment block, when the second alignment identification symbol is in position with the first alignment identification symbol, the two second alignment blocks are respectively on the two sides of the first alignment block. Alternatively, the second alignment identification symbol comprises one second alignment block, and the first alignment identification symbol comprises two first alignment blocks, when the second alignment identification symbol is in position with the first alignment identification symbol, the two first alignment blocks are respectively on the two sides of the second alignment block.

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