A color printing bag tracking system and method for a bag making machine

Abstract

The present invention discloses a color printing bag tracking system and method for a bag making machine, which uses a servo motor to drive the traction at a fixed length and uses two sensors to detect the positions of the color mark and the cutting knife respectively. The second sensor for detecting the position of the cutting knife is used as the starting signal for traction to control the second motor to drive the traction roller to perform fixed-length traction. Moreover, the fixed-length traction is combined with the color mark detection to dynamically assign a value to the traction bag pulling length in the next cycle, so that the traction bag pulling length is dynamically adjusted between the maximum bag length and the minimum bag length allowed. Here, the color mark signal is used as the judgment signal for assigning a value to the variable L of the bag pulling length during traction, rather than the signal for stopping the traction of the traction roller. In this way, high-speed traction is performed in any traction bag pulling cycle, significantly improving the bag making speed of the color printing bag.

Description

Technical Field

[0001] The present invention relates to the technical field of bag-making machinery, in particular to a color-printed bag tracking system and method for a bag-making machine. Background Art

[0002] Plastic bag making machine is a mechanical equipment that uses plastic film as raw material to make various packaging bags. It is usually divided into blank bags and color-printed bags according to whether the film is printed with patterns. Both types of packaging bags need to be cross-cut after bag making to cut the connected packaging bags into independent individual packaging bags. Generally, blank bags are cut by fixed-length traction rollers, that is, when the traction roller is pulled to the set length, the cutter cuts once. Color-printed bags use a color mark sensor to detect the color mark position. When the color mark sensor detects the color mark, the traction is paused and waits for the cutter to perform a cutting action. Since the color mark sensor has a response time requirement, it cannot obtain the color mark signal when pulling the material at high speed. Therefore, the traditional pulling method is to pull the material at high speed for a length L1 and then slow down to a low speed for a length L2. When the color mark signal is detected during L2, the pulling is stopped, where L1+L2=Lmax, L1 <Lmin,即在这个过程中为了防止传动系统惯性导致的牵引过冲现象,同时为了给色标传感器留有足够的响应时间,在一个牵引拉袋周期的末段需要设置一段低速牵引,在上述过程当中,由于末段是低速状态,相比牵引同样长度的空白袋,彩印袋需耗费更长时间,也就是在相同一段时间内,彩印袋的制袋速度低于空白袋制袋速度,导致制袋机的生产速度低,限制了制袋机在制作彩印袋时生产效率的提升。 Summary of the Invention

[0003] The object of the present invention is to provide a color-printed bag tracking system and method for a bag-making machine, so as to solve the problems in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solution: a color-printed bag tracking system for a bag-making machine, comprising a controller, characterized in that it also includes:

[0005] An unwinding device 16 for unwinding the film 1 printed with the color mark 5;

[0006] A feed roller 3 is connected to the first motor and is used to pull the film 1 on the unwinding device 16 forward;

[0007] The traction roller 7 is connected to the second motor and is used to tractionally convey the film 1 conveyed by the feeding roller 3 to the cutting assembly according to a set length;

[0008] The tension roller 4 is arranged on the traveling path of the film 1 between the feeding roller 3 and the traction roller 7, and is used for buffering the film 1 conveyed by the feeding roller 3 and maintaining the tension of the film 1 between the feeding roller 3 and the traction roller 7;

[0009] The cutting assembly includes a cutter 8, a transmission device 14 for driving the cutter 8 to cut the film 1, and a second sensor 13 for detecting the position of the cutter 8;

[0010] The first sensor 6 is arranged in front of the feeding end of the traction roller 7, and is used for detecting whether the color mark 5 is in place when the traction roller 7 completes one traction of the set length.

[0011] Further, an intermediate guide roller 2 is arranged between the unwinding device 16 and the feeding roller 3, and the intermediate guide roller 2 is used for horizontally guiding the film 1 into the feeding roller 3.

[0012] Further, the cutting assembly further includes a tool holder 10 for mounting the cutter 8. The two ends of the tool holder 10 are respectively connected to vertical guide columns 9. The lower ends of the guide columns 9 are connected by a connecting plate 11. The transmission device 14 is in transmission connection with the connecting plate 11 through a pull rod 12. An anvil 15 is arranged below the cutter 8 to cooperate with the cutter 8.

[0013] Further, the second motor is a servo motor, and the first motor is a speed-regulating motor or a servo motor or a general motor.

[0014] As another aspect of the invention, the present technical solution also provides a method for tracking color-printed bags of a bag-making machine, which is applied to the above-mentioned color-printed bag tracking system of the bag-making machine, and includes the following steps:

[0015] Step 1: Set the bag length parameters, including at least the minimum bag length Lmin and the maximum bag length Lmax, store the above parameters in the controller, and the controller initializes the bag length variable L: L = (Lmin + Lmax) / 2;

[0016] Step 2: Start the operation of the bag-making machine. The controller issues an operation signal. The transmission device drives the cutter to act. The second sensor detects the position of the cutter and sends the position signal to the controller. When the cutter is in the position of cutting the film, the signal sent by the second sensor to the controller is the pulling stop signal. When the cutter is in the high position allowing the film to pass, the signal sent by the second sensor to the controller is the pulling start signal;

[0017] Step 3: The controller judges whether it receives the pulling start signal. If it receives the pulling start signal, it enters Step 4. If it does not receive the pulling start signal, the second motor does not act and continues to wait;

[0018] Step 4: The controller controls the second motor to start, driving the traction roller to rotate at a high speed to perform fixed-length traction and bag pulling on the film. When the traction and bag pulling length value = L, the second motor pauses. At this time, the cutter 8 descends to perform a cutting action on the film. During the traction and bag pulling process, steps 401 and 402 are sequentially executed. The specific content of step 401 is that the material pulling cut-off signal is enabled simultaneously when the traction and bag pulling starts; the specific content of step 402 is that during the traction and bag pulling process, the controller checks the material pulling cut-off signal. If the material pulling cut-off signal is not detected, it enters step 5. If the material pulling cut-off signal is detected, it enters step 11;

[0019] Step 5: If the fixed-length traction and bag pulling in step 4 are completed and the controller in step 402 does not detect the material pulling cut-off signal, the controller masks the current material pulling cut-off signal and enters step 6;

[0020] Step 6: The controller determines whether a color mark is detected according to the signal sent by the first sensor. If a color mark is detected, it enters step 7. If no color mark is detected, it enters step 8;

[0021] Step 7: The controller assigns a value to the bag length variable L: L = Lmin as the traction and bag pulling length value for the next cycle, and enters step 9;

[0022] Step 8: The controller assigns a value to the bag length variable L: L = Lmax as the traction and bag pulling length value for the next cycle, and enters step 9;

[0023] Step 9: The controller checks whether the running signal continues to exist. If the running signal exists, it enters step 3 to perform fixed-length traction and bag pulling for the next cycle. If the running signal does not exist, it enters step 10;

[0024] Step 10, execute the normal shutdown procedure;

[0025] Step 11, execute the overspeed shutdown procedure.

[0026] Furthermore, in step 1, the bag length adjustment length parameter A can also be set.

[0027] Furthermore, when the bag length adjustment length parameter A is set in step 1, if the controller determines that a color mark is detected in step 6, it enters step 701. If no color mark is detected, it enters step 801;

[0028] Step 701, the controller assigns a value to the bag length variable L: L = L - A as the traction and bag pulling length value for the next cycle, and enters step 702;

[0029] Step 801, the controller assigns a value to the bag length variable L: L = L + A as the traction and bag pulling length value for the next cycle, and enters step 802;

[0030] Step 702: The controller determines whether L > Lmin holds after the bag length variable L is assigned. If L > Lmin holds, go to Step 9; if L > Lmin does not hold, go to Step 12;

[0031] Step 802: The controller determines whether L < Lmax holds after the bag length variable L is assigned. If L < Lmax holds, go to Step 9; if L < Lmax does not hold, go to Step 12;

[0032] Step 12: Execute the color mark misalignment alarm program.

[0033] Advantages of the present invention: The color printing bag tracking system and method for a bag making machine provided by the present invention use a servo motor for fixed-length driving and traction, and two sensors are used to detect the positions of the color mark and the cutting knife respectively. The second sensor for detecting the cutting knife position is used as the starting signal for traction to start the second motor to drive the traction roller for fixed-length traction. The fixed-length traction is combined with color mark detection to dynamically assign a value to the traction and pulling bag length in the next cycle, so that the traction and pulling bag length is dynamically adjusted between the maximum allowable bag length and the minimum bag length. Here, after the fixed-length traction and pulling of the bag is completed, when the traction roller pauses, the first sensor detects whether the color mark reaches the first sensor position, that is, detects the color mark signal. The color mark signal is used as a judgment signal for assigning a value to the pulling bag length variable L during traction, rather than a signal for stopping the second motor (i.e., the signal for the traction roller to stop traction). Therefore, in this technical solution, the detection of the color mark is after the material pulling is completed, without a low-speed color mark searching process. The bag making speed of the color printing bag is the same as that of the blank bag. Compared with the traditional color mark searching method for bag making of color printing bags, the bag making machine applying this technical solution has a significant improvement in the bag making speed when producing color printing bags. This technical solution has the advantage of high-speed traction in any traction and pulling bag cycle, significantly improving the bag making speed of color printing bags. Description of the Drawings

[0034] Figure 1 It is a schematic structural diagram of the color printing bag tracking system for the bag making machine of the present invention;

[0035] Figure 2 It is a schematic diagram of the cutting component of the color printing bag tracking system for the bag making machine of the present invention;

[0036] Figure 3 It is a flowchart of the first embodiment of the color printing bag tracking method for the bag making machine of the present invention;

[0037] Figure 4 For Figure 3 Partial enlarged view of Steps 1 to 3 in

[0038] Figure 5 For Figure 3 Partial enlarged view of Steps 4, 5, 401, 402, and 11 in

[0039] Figure 6 for Figure 3 A partial enlarged view of steps 6 to 10;

[0040] Figure 7 This is a flow chart of a second embodiment of the method for tracking color-printed bags of a bag-making machine according to the present invention;

[0041] Figure 8 for Figure 7 A partial enlarged view of steps 1 to 3;

[0042] Figure 9 for Figure 7 Partially enlarged views of steps 4 to 6, step 401, step 402, and step 11;

[0043] Figure 10 for Figure 7 A partial enlarged view of steps 701 to 12. Implementation Method

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] See also Figures 1 - 10 A color-printed bag tracking system for a bag-making machine includes a controller, an unwinding device 16, a feed roller 3, a traction roller 7, a tension roller 4, a cutting assembly, and a first sensor 6. The unwinding device 16 is used to unwind a film 1 printed with a color mark 5; the feed roller 3 is connected to a first motor for pulling the film 1 on the unwinding device 16 forward; the traction roller 7 is connected to a second motor for pulling the film 1 conveyed by the feed roller 3 to a set length to the cutting assembly; the tension roller 4 is provided on the film 1 travel path between the feed roller 3 and the traction roller 7, and is used to buffer the film 1 conveyed by the feed roller 3 and keep the feed roller 3 from moving. 3 and the traction roller 7; the cutting assembly includes a cutter 8, a transmission device 14 for driving the cutter 8 to cut the film 1, and a second sensor 13 for detecting the position of the cutter 8; the first sensor 6 is arranged in front of the feeding end of the traction roller 7. When the traction roller 7 completes a set length of traction, the first sensor 6 is used to detect whether the color mark 5 is in place; here, the feed roller 3 and the traction roller 7 both adopt a double-roller roller group structure, that is, a driving roller and a pressure roller structure arranged in parallel. The driving roller is connected to the corresponding motor for transmission, and the pressure roller is used to press the film 1 against the driving roller to ensure stable traction.

[0046] Preferably, an intermediate guide roller 2 is provided between the unwinding device 16 and the feed roller 3. The intermediate guide roller 2 is used to guide the film 1 horizontally into the feed roller 3, so that the film 1 can be fully flattened to avoid wrinkles and ensure the quality of bag making.

[0047] Preferably, the cutting assembly also includes a knife seat 10 for mounting the cutter 8, the two ends of the knife seat 10 are respectively connected to the vertical guide column 9, the lower end of the guide column 9 is connected by a connecting plate 11, the transmission device 14 is connected to the connecting plate 11 through a pull rod 12, and an anvil 15 is provided below the cutter 8 to match the cutter 8. Here, the transmission device 14 is driven by an independent servo motor or a speed regulating motor, so that the cutting speed can be conveniently adjusted to cooperate with the traction of the traction roller 7. Figure 1 and Figure 2 The transmission device of this embodiment adopts a crank connecting rod structure to achieve faster cutting and reset speeds, and realizes high-speed bag making and cutting of the bag making machine with the cooperation of the traction roller 7.

[0048] Preferably, the second motor is a servo motor, and the first motor is a speed-regulating motor, a servo motor, or an ordinary motor. The second motor adopts a servo motor to accurately control the traction length of the traction roller 7 and can adjust the traction length of the traction roller according to the instruction of the controller. The start and stop of the first motor is controlled by the tension signal of the tension roller 4. Therefore, the first motor can adopt any one of the speed-regulating motor, the servo motor, or the ordinary motor. Figure 1 The tension roller 4 of this embodiment adopts a swing roller tension roller structure, which can control the tension of the traveling film 1 and play the role of buffering the material. In this way, the feed roller 3 can pull at a uniform speed to make the unwinding device 16 unwind at a uniform speed, and it can also ensure that a section of film 1 is temporarily stored for the traction roller 7 to be quickly pulled by the traction roller 7. When the traction roller 7 is paused, the material sent by the feed roller 3 is swung downward by the tension roller 4, and the traveling path of the film 1 becomes longer to perform buffering and storage. In this way, the bag making speed is further improved.

[0049] Here, the unwinding device 16 in this technical solution can be directly replaced by an output device after the longitudinal sealing and / or transverse sealing of the bag making machine, so that this technical solution and the longitudinal sealing and / or transverse sealing device of the bag making machine become an integrated structure.

[0050] As another aspect of the invention, the present technical solution further provides a method for tracking color-printed bags of a bag-making machine, which is applied to the above-mentioned color-printed bag tracking system of the bag-making machine, and comprises the following steps:

[0051] Step 1: Set the bag length parameters, including at least the minimum bag length Lmin and the maximum bag length Lmax, and store the above parameters in the controller. The controller will initially assign the bag length variable L: L=(Lmin+Lmax) / 2;

[0052] Step 2: Start the operation of the bag-making machine. The controller sends a running signal, which is maintained during normal operation. The transmission device 14 drives the cutting knife 8 to act. Generally, during normal operation, the cutting knife 8 operates at a constant speed. The second sensor 13 detects the position of the cutting knife 8 and sends the position signal to the controller. When the cutting knife 8 is in the position of cutting the film, the signal sent by the second sensor 13 to the controller is the material-pulling cut-off signal. When the cutting knife 8 is at the high position allowing the film to pass through, the signal sent by the second sensor 13 to the controller is the material-pulling start signal;

[0053] Step 3: The controller determines whether it has received the material-pulling start signal. If it has received the material-pulling start signal, it enters Step 4. If it has not received the material-pulling start signal, the second motor does not act and continues to wait;

[0054] Step 4: The controller controls the start of the second motor, driving the traction roller 7 to rotate at a high speed to perform fixed-length traction and bag pulling on the film 1. When the traction and bag-pulling length value = L, the second motor pauses. At this time, the cutting knife 8 descends to perform a cutting action on the film. During the traction and bag-pulling process, Steps 401 and 402 are sequentially executed. The specific content of Step 401 is that the material-pulling cut-off signal is enabled simultaneously when the traction and bag-pulling starts; the specific content of Step 402 is that during the traction and bag-pulling process, the controller checks the material-pulling cut-off signal. If the material-pulling cut-off signal is not detected, it enters Step 5. If the material-pulling cut-off signal is detected, it enters Step 11;

[0055] During the execution of Step 4, Steps 401 and 402 are sequentially executed. Its function is to form an electronic interlock effect on the traction and bag-pulling and the action of the cutting knife 8, that is, if the material-pulling cut-off signal appears during the traction and bag-pulling process, it means that during the traction and bag-pulling process, the cutting knife 8 has descended to perform a bag-cutting action, that is, the bag body has been cut and a waste bag appears. At this time, the bag-making machine is stopped by executing Step 11 to avoid continuous appearance of waste bags. Then, the operator can make the following adjustments according to the specific situation to match the traction and bag-pulling speed of the traction roller 7 with the running speed of the cutting knife 8: First, the rotation speed of the second motor during traction can be increased to increase the fixed-length traction and bag-pulling speed to meet the cutting speed of the cutting knife 8. Second, the rotation speed of the drive motor of the transmission device 14 can also be reduced, thereby reducing the cutting speed of the cutting knife 8 to match the traction speed of the traction roller 7;

[0056] Step 5: If the fixed-length traction and bag-pulling in Step 4 is completed and the controller does not detect the material-pulling cut-off signal in Step 402, the controller shields the current material-pulling cut-off signal and enters Step 6. Here, shielding the current material-pulling cut-off signal means that at this time, the current material-pulling cut-off signal does not work during the current fixed-length bag-pulling cycle to smoothly execute the subsequent steps;

[0057] Step 6: The controller determines whether a color mark is detected according to the signal sent by the first sensor 6. If a color mark is detected, it proceeds to Step 7; if no color mark is detected, it proceeds to Step 8;

[0058] Step 7: The controller assigns a value to the bag length variable L: L = Lmin as the pulling bag length value for the next cycle, and proceeds to Step 9;

[0059] Step 8: The controller assigns a value to the bag length variable L: L = Lmax as the pulling bag length value for the next cycle, and proceeds to Step 9;

[0060] Through the settings of Step 6, Step 7, and Step 8, taking the currently actually measured color mark position as the judgment benchmark, the pulling bag length for the next cycle is set, that is, the pulling bag length is adjusted autonomously and intelligently, which is an intelligent adaptive dynamic adjustment technology, completely avoiding the deficiency of the traditional traction drive system that requires a low-speed traction section, resulting in low bag-making efficiency for color-printed bags, and completely overcoming the defect of inaccurate cutting positions caused by the traction overshoot phenomenon;

[0061] Step 9: The controller checks whether the running signal persists. If the running signal exists, it proceeds to Step 3 for the fixed-length pulling bag in the next cycle; if the running signal does not exist, it proceeds to Step 10;

[0062] Step 10, execute the normal shutdown procedure;

[0063] Step 11, execute the overspeed shutdown procedure.

[0064] Preferably, to further precisely control the cutting accuracy, in Step 1, a bag length adjustment length parameter A can also be set, where the value of A is less than the difference between Lmax and Lmin, and the difference between Lmax and Lmin is preferably an integer multiple of A.

[0065] Preferably, when the bag length adjustment length parameter A is set in Step 1, if the controller determines that a color mark is detected in Step 6, it proceeds to Step 701; if it determines that no color mark is detected, it proceeds to Step 801.

[0066] Step 701: The controller assigns a value to the bag length variable L: L = L - A as the pulling bag length value for the next cycle, and proceeds to Step 702;

[0067] Step 801: The controller assigns a value to the bag length variable L: L = L + A as the pulling bag length value for the next cycle, and proceeds to Step 802;

[0068] Step 702: The controller determines whether L > Lmin holds after assigning a value to the bag length variable L. If L > Lmin holds, it proceeds to Step 9; if L > Lmin does not hold, it proceeds to Step 12;

[0069] In step 802, the controller determines whether L < Lmax holds after the bag length variable L is assigned. If L < Lmax holds, step 9 is entered; if L < Lmax does not hold, step 12 is entered.

[0070] In step 12, the color mark misalignment alarm program is executed.

[0071] By setting step 701, step 801, step 702, and step 802, the assignment of the fixed length variable L is progressive and the assignment is verified, effectively avoiding large fluctuations in the bag length during fixed length traction and bag pulling, which is beneficial to improving the running stability of the bag making machine. At the same time, the consistency of the cut finished bags is better and the bag making quality is high.

[0072] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0073] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "front", "both ends", "lower end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0074] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for tracking color-printed bags of a bag-making machine, which is applied to a color-printed bag tracking system of a bag-making machine. The color-printed bag tracking system of the bag-making machine includes a controller and further includes: An unwinding device (16) for unwinding a film (1) printed with a color mark (5); A feeding roller (3) is drivingly connected to a first motor for forwardly feeding the film (1) on the unwinding device (16); A pulling roller (7) is drivingly connected to a second motor for pulling and conveying the film (1) conveyed by the feeding roller (3) to a cutting assembly according to a set length; A tension roller (4) is arranged on the traveling path of the film (1) between the feeding roller (3) and the pulling roller (7) for buffering the film (1) conveyed by the feeding roller (3) and maintaining the tension of the film (1) between the feeding roller (3) and the pulling roller (7); The cutting assembly includes a cutter (8), a transmission device (14) for driving the cutter (8) to perform a cutting action on the film (1), and a second sensor (13) for detecting the position of the cutter (8); A first sensor (6) is arranged in front of the feeding end of the pulling roller (7). When the pulling roller (7) completes a set-length pulling, the first sensor (6) is used to detect whether the color mark (5) is in place; It is characterized in that it includes the following steps: Step 1: Set bag length parameters, including at least a minimum bag length Lmin and a maximum bag length Lmax, store the above parameters in the controller, and the controller initializes the bag length variable L: L = (Lmin + Lmax) / 2; Step 2: Start the operation of the bag-making machine. The controller issues an operation signal, the transmission device drives the cutter to act, the second sensor detects the position of the cutter, and sends a position signal to the controller. When the cutter is in the position of cutting the film, the signal sent by the second sensor to the controller is a pulling stop signal. When the cutter is in the high position allowing the film to pass, the signal sent by the second sensor to the controller is a pulling start signal; Step 3: The controller judges whether it receives a pulling start signal. If it receives a pulling start signal, it enters Step 4. If it does not receive a pulling start signal, the second motor does not act and continues to wait; Step 4: The controller controls the second motor to start, drives the pulling roller to rotate at a high speed to perform fixed-length pulling on the film to pull the bag. When the pulling length value = L, the second motor pauses. At this time, the cutter 8 descends to perform a cutting action on the film. During the pulling process of the bag, Step 401 and Step 402 are sequentially executed at the same time. The specific content of Step 401 is that the pulling stop signal is enabled at the same time as the pulling of the bag starts; the specific content of Step 402 is that during the pulling process of the bag, the controller checks the pulling stop signal. If the pulling stop signal is not detected, it enters Step 5. If the pulling stop signal is detected, it enters Step 11; Step 5: If the fixed-length pulling of the bag in Step 4 is completed and the controller does not detect the pulling stop signal in Step 402, the controller shields the current pulling stop signal and enters Step 6; Step 6: The controller determines whether a color mark is detected according to the signal sent by the first sensor. If a color mark is detected, go to Step 7; if no color mark is detected, go to Step 8; Step 7: The controller assigns a value to the bag length variable L: L = Lmin as the traction bag pulling length value for the next cycle, and go to Step 9; Step 8: The controller assigns a value to the bag length variable L: L = Lmax as the traction bag pulling length value for the next cycle, and go to Step 9; Step 9: The controller checks whether the running signal persists. If the running signal exists, go to Step 3 for the fixed-length traction bag pulling in the next cycle. If the running signal does not exist, go to Step 10; Step 10, execute the normal shutdown procedure; Step 11, execute the overspeed shutdown procedure.

2. A method for tracking color-printed bags of a bag-making machine according to claim 1, characterized in that: In Step 1, the bag length adjustment length parameter A can also be set.

3. A method for tracking color-printed bags of a bag-making machine according to claim 2, characterized in that: When the bag length adjustment length parameter A is set in Step 1, in Step 6, if the controller determines that a color mark is detected, go to Step 701; if no color mark is detected, go to Step 801; Step 701: The controller assigns a value to the bag length variable L: L = L - A as the traction bag pulling length value for the next cycle, and go to Step 702; Step 801: The controller assigns a value to the bag length variable L: L = L + A as the traction bag pulling length value for the next cycle, and go to Step 802; Step 702: The controller determines whether L > Lmin holds after the value of the bag length variable L is assigned. If L > Lmin holds, go to Step 9; if L > Lmin does not hold, go to Step 12; Step 802, the controller determines whether L < Lmax holds after the value of the bag length variable L is assigned. If L < Lmax holds, go to Step 9; if L < Lmax does not hold, go to Step 12; Step 12, execute the color mark misalignment alarm procedure.

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