A label mark-seeking continuous gilding process

Abstract

The application discloses a label searching and continuous gilding process and belongs to the technical field of label printing post-processing. The process comprises five core steps of label input, buffer buffering, label searching detection, gilding treatment and paper output. A floating roller type buffer mechanism is arranged at the front end of the gilding process, so that the label paper input in a gap type is converted into a continuous and uniform paper flow. Meanwhile, a double triggering mechanism of a label searching signal and a minimum continuous gilding length is innovatively adopted, and the label searching sensor and a PID closed loop control system are matched, so that the accurate dynamic compensation of the gilding position is realized. The application completely solves the industry problem that the gap type paper feeding and the continuous gilding process are not matched, can realize uninterrupted continuous gilding, improves the production efficiency by 30%-50%, and makes the gilding register accuracy reach within ±0.05 mm, so that the adhesion and the gloss uniformity of the gilding layer are significantly improved, the product yield can reach more than 98%, and the application can be widely applied to the gilding processing of various types of adhesive labels, and is especially suitable for the online gilding scene of the intermittent label printing machine.

Description

Technical Field

[0001] This invention relates to the field of label printing post-processing technology, and in particular to a label-finding continuous hot stamping process, which is especially suitable for continuous hot stamping of self-adhesive labels under intermittent paper feeding conditions. Background Technology

[0002] Hot stamping, as one of the core technologies for surface decoration of printed materials, works by using the heat transfer effect to transfer the metal layer in the electroplated aluminum foil to the surface of the substrate, forming a graphic effect with a metallic luster. It is widely used in various self-adhesive label products such as food packaging, daily chemical labels, and pharmaceutical labels to enhance the visual grade and anti-counterfeiting performance of the products.

[0003] In the actual label production process, many label printing machines use intermittent paper feeding (also known as step-feeding), especially flexographic printing presses and intermittent PS plate label printing presses. These machines use intermittent paper feeding to coordinate multi-color overprinting and die-cutting processes. The label paper output by these machines is in a discontinuous, intermittent feeding state, while high-quality hot stamping processes usually require the substrate to pass through the hot stamping station continuously and at a constant speed to ensure the stability of hot stamping temperature, pressure, and time. This leads to a significant mismatch between intermittent paper feeding and continuous hot stamping processes.

[0004] Currently, there are related technological explorations in the industry to address this issue. For example, Chinese invention patent application CN119262909A discloses an automated hot stamping equipment, which sets up a material storage mechanism between the first conveying mechanism and the processing table. This mechanism can temporarily store excess paper conveyed from the front end, and when the front end feeding speed changes or gets stuck, it does not affect the normal operation of the second conveying mechanism at the back end. However, this technical solution is aimed at the flatbed hot stamping scenario of single-sheet paperboard. Its material storage mechanism is only used to stack and temporarily store single sheets of material, which cannot adapt to the continuous conveying requirements of roll-type label paper. It also lacks label position recognition and synchronous hot stamping control functions, and cannot solve the matching problem between intermittent roll paper feeding and continuous hot stamping.

[0005] Chinese utility model patent CN202764388U discloses a high-efficiency one-step forming mechanism for various hot stamping processes. It features an electroplated aluminum foil buffer unwinding system, achieving stable conveying of the electroplated aluminum foil through unwinding buffering and tension tightening devices. It also integrates multiple processes such as positioning hot stamping, skip hot stamping, and continuous hot stamping. However, the buffering mechanism of this technical solution only targets the hot stamping foil (electroplated aluminum foil) itself and does not buffer the label paper being printed, failing to solve the problem of intermittent hot stamping caused by gaps in the printed paper. Furthermore, its positioning function only targets the pattern on the electroplated aluminum foil, failing to achieve precise alignment between the printed text and the hot stamping position on the label paper.

[0006] Chinese invention patent application CN104859328A discloses a multi-color positioning hot stamping process, which achieves aligned hot stamping of multiple hot stamping plates and labels by keeping the spacing between the labels on the substrate consistent with the spacing between the hot stamping plates. However, this process is designed for flatbed multi-color hot stamping layouts and relies on fixed spacing matching for positioning, making it unsuitable for scenarios with intermittent dynamic paper feeding. When paper feeding experiences length fluctuations or positional shifts, dynamic compensation cannot be performed, making it difficult to guarantee positioning accuracy and preventing continuous, uninterrupted hot stamping processing.

[0007] Chinese invention patent CN121105557B discloses a pre-formed pattern precision positioning hot stamping machine. It sets identification labels on the hot stamping foil and uses a label reader to identify the labels to adjust the positional relationship between the hot stamping foil and the cardboard, achieving precise positioning. However, this technical solution positions the hot stamping foil, not the printed label paper; furthermore, it targets hot stamping of single sheets of cardboard and lacks a paper buffer mechanism for intermittent roll feeding, failing to solve the problems of hot stamping interruptions and inconsistent quality caused by intermittent paper feeding.

[0008] In summary, existing technologies generally suffer from the following three technical shortcomings when applied to label hot stamping scenarios with intermittent paper feeding: Discontinuous paper input leads to intermittent hot stamping process: When label paper is input intermittently, the length of paper fed each time does not match the continuous hot stamping length required by the hot stamping process, resulting in frequent pauses or interruptions during the hot stamping process. This leads to low production efficiency, and frequent start-stop cycles accelerate the wear and tear of the hot stamping plate, shortening the service life of the equipment.

[0009] Poor stability of hot stamping effect and many quality defects: When the paper input stops or is not long enough, the hot stamping components cannot maintain continuous and stable hot stamping pressure and temperature. The local hot stamping time is too long or too short, resulting in incomplete hot stamping graphics, uneven adhesion, inconsistent surface gloss and other quality problems. The product yield is low and it is difficult to meet the quality requirements of high-end labels.

[0010] Insufficient positioning accuracy and large registration error: Existing technology lacks an effective label paper position detection and dynamic synchronization control mechanism, making it difficult to achieve precise alignment between the printed image and the hot stamping position. Especially in dynamic fluctuation scenarios with intermittent paper feeding, the hot stamping edge is prone to burrs and misalignment, and the registration accuracy can usually only reach ±0.15mm or more, which cannot meet the production requirements of high-precision labels.

[0011] Therefore, developing a label hot stamping process that can adapt to intermittent paper feeding, achieve continuous and stable hot stamping, and has high positioning accuracy is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0012] To address the shortcomings of existing technologies, the purpose of this invention is to provide a label-following continuous hot stamping process. By setting up a buffer mechanism and a label-following sensor to work together, the matching contradiction between intermittent paper feeding and continuous hot stamping processes is resolved, achieving continuous and accurate hot stamping of labels, and significantly improving hot stamping quality and production efficiency.

[0013] This invention can completely eliminate the impact of intermittent paper feeding on the hot stamping process under intermittent label feeding conditions, achieving truly continuous and stable hot stamping, while ensuring high-precision registration between the hot stamping pattern and the printed text on the label, thus improving hot stamping quality and production efficiency.

[0014] The above-mentioned objective of this invention is achieved through the following technical solutions: A label-finding continuous hot stamping process includes the following steps: Step S1, Label Input: The label paper with the synchronization mark pre-printed on the surface is input into the hot stamping equipment in an intermittent manner. The label input process simultaneously meets two triggering conditions: the tracking sensor senses the synchronization mark on the label paper and generates a valid detection signal; the continuous paper length at the output end of the hot stamping equipment meets the minimum continuous hot stamping length preset by the hot stamping process. Step S2, Buffering: The intermittently input label paper enters the buffer mechanism for length compensation and tension stabilization. Through the dynamic paper storage adjustment of the buffer mechanism, the intermittently input label paper is converted into a uniform and continuous output paper flow. Step S3, Marker Detection: After the label paper is output through the buffer mechanism, the marker sensor performs real-time sensing and identification of the synchronous mark on the label paper, and transmits the detected position signal to the control system of the hot stamping equipment in real time. Step S4, Hot Stamping Process: After receiving the position signal from the tracking sensor, the control system calculates the hot stamping start position based on the position information of the synchronous marker, controls the hot stamping component to start and maintain constant hot stamping pressure and temperature, and performs continuous hot stamping processing at the designated position on the label paper. Step S5, Paper Output: The label paper after hot stamping is output from the hot stamping equipment at a continuous and uniform speed, and enters the subsequent winding or die-cutting process.

[0015] Further, in step S1, the single conveying length of the intermittent paper feeding is 50mm~500mm, and the interval time of a single conveying is 0.2s~2s; the label paper is roll-type self-adhesive label paper, and the synchronous marks on the label paper are set at equal intervals along the paper conveying direction, and the spacing between adjacent synchronous marks is consistent with the length of a single label.

[0016] Further, in step S2, the buffer mechanism adopts a floating roller group buffer structure, including a fixed guide roller group, a floating guide roller group, and a tension adjustment unit; the label paper alternately passes around the fixed guide roller and the floating guide roller, and the vertical displacement of the floating guide roller changes the paper storage length in the buffer mechanism; when the label paper input is paused, the floating guide roller moves in the direction of decreasing paper storage, releasing the buffered paper to maintain continuous conveying at the output end; when the label paper is input again, the floating guide roller moves in the direction of increasing paper storage, replenishing the buffered paper.

[0017] Further, in step S1, the minimum continuous hot stamping length is calculated as the sum of the length of the hot stamping area of ​​a single label and the pressing contact arc length of the hot stamping component; the judgment logic of the two triggering conditions is as follows: the control system collects the paper storage length data of the buffer mechanism and the signal status of the tracking sensor in real time, and only sends a hot stamping start command to the hot stamping component when the paper storage length is ≥ the minimum continuous hot stamping length and the tracking sensor detects a valid synchronization mark; if either of the two conditions is not met, the hot stamping component remains in standby mode, and the buffer mechanism continues to maintain stable paper tension at the output end.

[0018] Further, in step S3, the tracking sensor is a photoelectric color mark sensor, installed on the paper conveying path between the output end of the buffer mechanism and the input end of the hot stamping component, and the installation distance from the hot stamping component pressing station is a fixed value L; the synchronization mark is a rectangular color block mark printed on the side of the label paper, and the color of the color block forms a grayscale difference of ≥30% with the background color of the label paper; after the tracking sensor detects the synchronization mark, the control system calculates the delay time for hot stamping start based on the paper conveying speed and distance L, so as to achieve precise alignment between the hot stamping position and the label graphics.

[0019] Furthermore, in step S4, the hot stamping assembly adopts a rotary hot stamping roller structure, including a heated hot stamping roller and a rubber pressure roller; during the hot stamping process, the surface temperature of the hot stamping roller is controlled at 100℃~180℃, the hot stamping line pressure is controlled at 5kg / cm~20kg / cm, and the linear speed of the hot stamping roller is synchronized with the linear speed of the paper output by the buffer mechanism; the control system adjusts the rotation speed and temperature of the hot stamping roller in real time through closed-loop feedback, and when the paper conveying speed fluctuates, it completes speed compensation within 0.1s to ensure the stability of hot stamping pressure and hot stamping time.

[0020] Furthermore, the maximum paper storage length of the buffer mechanism is 1.5 to 3 times the single-interval paper feeding length; the buffer mechanism is also equipped with an upper limit sensor and a lower limit sensor, corresponding to the maximum paper storage position and the minimum paper storage position, respectively; when the floating guide roller triggers the lower limit sensor, the control system sends an accelerated paper feeding command to the paper feeding mechanism at the input end to replenish the buffer amount; when the floating guide roller triggers the upper limit sensor, the control system sends a pause paper feeding command to the paper feeding mechanism at the input end to prevent paper overflow.

[0021] Furthermore, after step S5, a post-hot stamping processing step S6 is also included: the hot stamped label paper is first rapidly cooled by a cooling roller assembly to solidify and set the hot stamping layer, with the surface temperature of the cooling roller assembly controlled at 15℃~30℃; then, the accuracy of the hot stamping position, the integrity of the hot stamping layer, and the gloss are inspected online by a visual inspection component to remove unqualified products; finally, the paper is wound up by a winding mechanism with constant tension, with the winding tension controlled at 5N~20N.

[0022] Furthermore, in step S4, the control system employs a PID closed-loop control algorithm to achieve precise synchronous control of the hot stamping position, specifically including: Step S41: Pre-set the standard hot stamping offset threshold in the control system, with a threshold range of ±0.05mm; Step S42: The tracking sensor collects the actual position information of the synchronous marker in real time and calculates the deviation between the actual position and the theoretical position; Step S43: When the deviation value is within the threshold range, the control system keeps the current hot stamping roller speed unchanged; when the deviation value exceeds the threshold range, the control system dynamically compensates the hot stamping position by adjusting the instantaneous speed of the hot stamping roller, so that the deviation value falls back to the threshold range.

[0023] Furthermore, this process is applied to the inline hot stamping process of an intermittent label printing machine. After the label paper is printed intermittently at the printing station, it directly enters the buffer mechanism of the hot stamping equipment in an intermittent output state. The synchronous mark and the label graphic are printed synchronously in the printing process, and the position of the synchronous mark corresponds to the starting position of a single label.

[0024] In summary, compared with the prior art, the present invention has at least one of the following beneficial technical effects: Achieving a perfect match between intermittent paper feeding and continuous hot stamping, thus improving production efficiency: This invention, by setting a buffer mechanism at the front end of the hot stamping station and utilizing the dynamic paper storage function of the floating roller group, transforms the intermittently input label paper into a uniform and continuous paper flow, completely solving the problem of mismatch between intermittent paper feeding and continuous hot stamping processes. Compared to the traditional intermittent hot stamping process with frequent start-stop cycles, this invention achieves uninterrupted continuous hot stamping, increasing production efficiency by 30% to 50%, while reducing mechanical wear caused by frequent start-stop cycles of the hot stamping components and extending equipment lifespan by more than 20%.

[0025] A dual-condition triggering mechanism ensures stable hot stamping process and significantly improves hot stamping quality: This invention innovatively proposes a dual-triggering condition of "targeting signal + minimum continuous length." Hot stamping is only initiated when the length of the buffer paper meets the minimum continuous hot stamping requirement and a valid synchronization mark is detected, fundamentally avoiding interruptions in hot stamping due to insufficient paper length. Combined with the closed-loop temperature and pressure control of the rotary hot stamping assembly, it maintains high stability in temperature, pressure, and stamping time during the hot stamping process. The uniformity of hot stamping layer adhesion is improved by more than 40%, and the surface gloss consistency reaches more than 95%. This completely solves quality defects such as incomplete hot stamping graphics and rough edges, increasing product yield from 85% in traditional processes to over 98%.

[0026] High-precision hot stamping registration is achieved through synchronous closed-loop control with a tracking sensor at the buffer output. Combined with the PID dynamic compensation algorithm of the control system, this invention can detect the positional deviation of the label paper in real time and perform instantaneous speed compensation. The hot stamping registration accuracy can reach within ±0.05mm, far exceeding the conventional level of ±0.15mm in existing technologies. Even in scenarios with paper speed fluctuations caused by intermittent paper feeding, it can ensure precise alignment between the hot stamping pattern and the printed text on the label, resulting in smooth and clear hot stamping edges, meeting the high-precision requirements of high-end anti-counterfeiting labels and daily chemical product labels.

[0027] Highly adaptable, it can directly connect to existing intermittent printing equipment: This process requires no modification to the front-end intermittent label printing equipment. The printed labels can be directly fed into the hot stamping equipment in an intermittent output state, realizing in-line production of printing and hot stamping, eliminating intermediate rewinding and transfer processes, and reducing labor costs and material waste. At the same time, the process parameters have a wide range of adjustment, which can adapt to label products of different lengths from 50mm to 500mm, and are compatible with various label substrates such as coated paper, PET, and PE, making it suitable for a wide range of scenarios. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the overall process of the label-finding continuous hot stamping process described in this invention. Figure 2 A schematic diagram of the overall structure of the hot stamping equipment for implementing the process of this invention; Figure 3 This is a logic control block diagram of the control system described in this invention.

[0029] Reference numerals: 1. Paper feeding traction roller; 2. Buffer mechanism; 3. Tracking sensor; 4. Hot stamping assembly. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. Example

[0031] This embodiment provides a label-finding continuous hot stamping process, which is implemented based on a dedicated label-finding continuous hot stamping equipment. The equipment includes, in sequence, an unwinding mechanism, a paper feeding traction roller 1, a buffer mechanism 2, a label-finding sensor 3, a hot stamping assembly 4, a cooling roller group, a vision inspection assembly, and a rewinding mechanism. Each mechanism is electrically connected to the control system and is uniformly coordinated and controlled by the control system.

[0032] The label paper processed in this embodiment is a roll-type coated paper self-adhesive label, with a single label length of 100mm and a width of 60mm. The label paper surface is printed with a label graphic area, and a synchronization mark is printed on the left edge of the label paper. The synchronization mark is a black rectangular block with a size of 5mm×3mm, which forms a significant grayscale difference with the white background of the label paper. The spacing between adjacent synchronization marks is consistent with the length of a single label, which is 100mm. The pre-set hot stamping area on each label is 30mm long and located at the top of the label graphic area.

[0033] Combination Figure 1 and Figure 2 The specific process steps in this embodiment are as follows: Step S1, Label Input The printed label roll is installed on the unwinding mechanism. The end of the label is pulled by the paper feeding traction roller 1 and fed to the buffer mechanism 2 in an intermittent manner. In this embodiment, the paper feeding traction roller 1 is driven by a servo motor and adopts an intermittent paper feeding mode. The single feeding length is 100mm (corresponding to the length of a single label), the single feeding time is 0.3s, and the feeding interval is 0.5s, that is, a label is fed once every 0.8s.

[0034] During the label input process, the control system continuously checks two trigger conditions: Condition ①: Whether the tracking sensor 3 detects the synchronization mark on the label paper and generates a valid detection signal; Condition ②: Does the length of the paper stored in the buffer mechanism 2 meet the minimum continuous hot stamping length preset by the hot stamping process?

[0035] In this embodiment, the minimum continuous hot stamping length is calculated as follows: 30mm for the hot stamping area of ​​a single label + 20mm for the contact arc length of the hot stamping component 4 = 50mm; to allow for a safety margin, the actual minimum continuous hot stamping length is set to 80mm.

[0036] The control system sends a command to the hot stamping assembly 4 to start hot stamping only when both conditions are met simultaneously. If either condition is not met, the hot stamping assembly 4 remains in standby mode, and the buffer mechanism 2 maintains stable tension of the paper at the output end, without performing hot stamping. This dual-condition mechanism ensures that once the hot stamping process is started, it can continuously complete the hot stamping of at least one label without interruption due to insufficient paper.

[0037] Step S2, Cache Buffer The intermittently input label paper enters the buffer mechanism 2 for length compensation and tension adjustment. In this embodiment, the buffer mechanism 2 adopts a floating roller group structure, including an upper fixed guide roller group, a lower fixed guide roller group, a floating guide roller group, a floating support, a tension adjustment cylinder, an upper limit sensor, and a lower limit sensor.

[0038] The upper fixed guide roller group consists of 3 horizontally arranged fixed guide rollers, which are installed on the upper frame of the buffer mechanism 2; the lower fixed guide roller group consists of 2 horizontally arranged fixed guide rollers, which are installed on the lower frame of the buffer mechanism 2; the floating guide roller group consists of 3 floating guide rollers, which are installed on a floating support, and the floating support can slide up and down along the vertical guide rail; the tension adjusting cylinder is installed above the floating support to provide a constant tension force and ensure stable paper tension.

[0039] After the label paper enters the buffer mechanism 2 from the input end, it alternately winds around the upper fixed guide roller, the floating guide roller, and the lower fixed guide roller, forming an "S"-shaped paper winding path. By moving the floating guide roller group up and down, the total length of paper stored in the buffer mechanism 2 can be changed: when the floating guide roller group moves upward, the paper winding path is shortened and the paper storage amount is reduced; when the floating guide roller group moves downward, the paper winding path is lengthened and the paper storage amount is increased.

[0040] In this embodiment, the maximum paper storage length of the buffer mechanism 2 is 200mm, which is twice the single-interval paper feeding length (100mm), and can accommodate the amount of paper fed in two intervals. The buffer operation process is as follows: When the paper feeding traction roller 1 feeds paper intermittently, the label paper is quickly fed into the buffer mechanism 2, the paper tension is temporarily increased, which pushes the floating guide roller group to move upward, increases the paper storage capacity, and temporarily stores the intermittently fed paper. When the paper feeding traction roller 1 enters the conveying interval and stops feeding paper, the input end stops feeding paper. At this time, the tension adjusting cylinder pushes the floating guide roller group to move slowly downward, releasing the buffered paper and maintaining the output end paper to be continuously conveyed at a constant speed. When the floating guide roller group descends to the position of the lower limit sensor, the lower limit sensor sends a signal to the control system, and the control system controls the paper feeding traction roller 1 to start the next paper feeding in advance to replenish the buffer and avoid running out of paper. When the floating guide roller assembly rises to the position of the upper limit sensor, the upper limit sensor sends a signal to the control system, and the control system controls the paper feeding traction roller 1 to stop feeding paper to avoid excessive paper causing overflow or loss of tension control.

[0041] Through the above dynamic adjustment process, the buffer mechanism 2 transforms the intermittent, pulsating paper input at the front end into a uniform, continuous, and tension-stable paper flow output at the back end, providing a stable material basis for subsequent continuous hot stamping.

[0042] Step S3, Target Detection After the label paper is output from the buffer mechanism 2, it passes through the detection station of the label-finding sensor 3 at a constant speed. In this embodiment, the label-finding sensor 3 is a high-precision photoelectric color mark sensor with a detection accuracy of 0.01mm. The label-finding sensor 3 is installed between the output end of the buffer mechanism 2 and the input end of the hot stamping component 4, and the fixed distance L from the pressing center station of the hot stamping component 4 is 150mm.

[0043] The tracking sensor 3 emits a detection beam towards the side area of ​​the label paper. When the black synchronization mark passes through the detection area, the intensity of the reflected light changes abruptly. After the tracking sensor 3 detects this change, it immediately sends a pulse-type position trigger signal to the control system.

[0044] After receiving the trigger signal, the control system calculates the hot stamping start delay time t = L / v based on the current paper feed speed v. In this embodiment, the paper feed linear speed is set to 30 m / min, or 0.5 m / s, and the distance L is 0.15 m. Therefore, the delay time t = 0.15 / 0.5 = 0.3 s. That is, after the tracking sensor 3 detects the synchronization mark, after a delay of 0.3 s, the hot stamping component 4 starts hot stamping at the preset hot stamping start position on the label, achieving precise alignment between the hot stamping area and the label text.

[0045] At the same time, the control system records the actual arrival time of each synchronization marker, compares it with the theoretical time, calculates the position deviation value, and provides a data basis for subsequent closed-loop position compensation.

[0046] Step S4: Hot stamping When the control system simultaneously meets the dual triggering conditions and completes the calculation of the hot stamping start position, it controls the hot stamping component 4 to start and perform continuous hot stamping processing.

[0047] In this embodiment, the hot stamping component 4 adopts a rotary hot stamping structure, including a hot stamping roller, a rubber pressure roller, a heating unit, and a pressure adjustment mechanism. The hot stamping roller is a metal roller with a hot stamping pattern corresponding to the hot stamping area engraved on its surface; the heating unit is embedded inside the hot stamping roller and uses electric heating, combined with a temperature sensor to achieve constant temperature control; the rubber pressure roller is made of silicone with a Shore hardness of 75 degrees, and the pressure adjustment mechanism adjusts the pressure between it and the hot stamping roller.

[0048] The specific process parameters for hot stamping are controlled as follows: Temperature control: The heating unit heats the surface temperature of the hot stamping roller to 130℃. The control system collects the roller surface temperature in real time through the PT100 temperature sensor and uses a PID algorithm for closed-loop regulation. The temperature fluctuation is controlled within ±2℃ to ensure a stable transfer effect of the hot stamping layer.

[0049] Pressure control: The pressure adjustment mechanism adopts a cylinder pressurization method to adjust the hot stamping line pressure to 12kg / cm. The pressure sensor provides real-time feedback of the pressing force to ensure uniform pressure across the entire roller, with a lateral pressure deviation not exceeding ±0.5kg / cm.

[0050] Speed ​​synchronization control: The hot stamping roller is driven by an independent servo motor, and its surface linear speed is strictly synchronized with the paper linear speed output by the buffer mechanism 2, with the speed deviation controlled within ±0.1%. When the paper feed speed fluctuates slightly due to buffer adjustment, the control system completes dynamic compensation of the hot stamping roller speed within 0.1s to ensure consistent relative linear speed and avoid stretching or compression deformation of the image.

[0051] To further improve positioning accuracy, the control system employs a PID closed-loop control algorithm for dynamic position compensation, combined with... Figure 3 The control logic, specifically the process is as follows: S41. Pre-set the hot stamping offset threshold to ±0.05mm in the control system; S42. For each synchronization marker detected by the tracking sensor 3, the control system calculates the deviation value Δx between the actual arrival position and the theoretical position of the marker. S43. When |Δx|≤0.05mm, the positional deviation is determined to be within the allowable range, and the control system maintains the current speed of the hot stamping roller unchanged; S44. When |Δx|>0.05mm, the position deviation is determined to exceed the threshold. The control system adjusts the instantaneous speed of the hot stamping roller by means of the servo motor according to the direction and magnitude of the deviation: if the actual position is ahead, the speed of the hot stamping roller is slightly reduced; if the actual position is behind, the speed of the hot stamping roller is slightly increased. The deviation is corrected to the threshold range within 1 to 2 label cycles.

[0052] Through the above closed-loop control, even if there are slight positional fluctuations in the paper feeding caused by intermittent paper feeding, the registration accuracy between the hot stamping pattern and the label text can be kept within ±0.05mm, and the hot stamping edges are smooth and clear, without misalignment or burrs.

[0053] During continuous hot stamping, the buffer mechanism 2 continuously performs dynamic paper storage and release to ensure a continuous supply of paper to the hot stamping station. The hot stamping component 4 does not need to be frequently started and stopped, maintaining a continuous and stable working state, thus completely solving the intermittent problem of traditional intermittent hot stamping.

[0054] Step S5: Paper output and post-ironing processing After the hot stamping process is completed, the label paper is output from the hot stamping component 4 and enters the subsequent post-hot stamping processing steps: Cooling and Shaping: The label paper first passes through a cooling roller assembly, which includes two water-cooled rollers with the roller surface temperature controlled at around 20°C. The high-temperature hot stamping layer is rapidly cooled by the cooling rollers, and the electroplated aluminum layer quickly solidifies and sets, preventing the hot stamping layer from sticking or peeling off due to excessive temperature during subsequent winding, thus improving the adhesion and abrasion resistance of the hot stamping layer.

[0055] Online Inspection: After cooling, the label paper passes through a vision inspection unit. This unit uses a high-speed industrial camera and image processing algorithms to perform online inspection of the hot stamping quality of each label. Inspection items include hot stamping position deviation, integrity of the hot stamping pattern, and uniformity of the hot stamping layer's gloss. When a defective product is detected, the control system records the defect location and automatically rejects it in the subsequent die-cutting process.

[0056] Finished product winding: The qualified label paper is finally wound up by the winding mechanism with constant tension. The winding tension is set to 10N. The tension is controlled in a closed loop by a magnetic powder brake to ensure neat winding and appropriate tightness, and to avoid paper stretching and deformation. Example

[0057] The process principle of this embodiment is basically the same as that of embodiment 1. The difference lies in the application scenario and process parameters. This embodiment is applied to the inline hot stamping process of an intermittent flexographic printing press. The label paper enters the hot stamping process online directly after printing, without the need for separate unwinding.

[0058] In this embodiment, the paper feeding step of the intermittent flexographic printing press at the front end is 200mm, corresponding to a single label length of 200mm, and the paper feeding interval is 1s. The label substrate is PET transparent self-adhesive material with a thickness of 50μm. The synchronous marking is printed on the right edge of the label as a silver block, creating optical contrast with the transparent substrate. The hot stamping area is the label's border pattern, with a hot stamping length of 150mm.

[0059] The corresponding process parameters to be adjusted are as follows: Parameters of buffer mechanism 2: The maximum paper storage length of buffer mechanism 2 is set to 500mm, which is 2.5 times the single paper feeding length, in order to accommodate longer paper feeding steps and ensure that there is enough paper to maintain continuous hot stamping within the paper feeding interval.

[0060] Minimum continuous hot stamping length: Hot stamping area length 150mm + pressing contact arc length 25mm = 175mm, the minimum continuous hot stamping length is set to 200mm.

[0061] Hot stamping process parameters: Since the heat resistance of PET substrate is different from that of coated paper, the hot stamping roller temperature is set to 150℃, the hot stamping line pressure is set to 8kg / cm, and the paper conveying line speed is 20m / min.

[0062] Tracking compensation: Tracking sensor 3 adopts a transmission-type photoelectric sensor specifically for transparent materials to adapt to the detection requirements of transparent PET substrates. The installation distance L from the hot stamping station is 200mm, and the corresponding delay time is dynamically calculated according to the conveying speed.

[0063] This embodiment realizes a fully integrated production line for printing and hot stamping. The label is printed and hot stamped in one go, eliminating the intermediate rewinding and transfer processes, which further improves production efficiency. At the same time, it avoids problems such as material scratches and contamination caused by secondary turnover, and the product quality is more stable. Example

[0064] Based on Example 1, this embodiment further optimizes the tension control and multi-segment buffer matching of the hot stamping process, making it suitable for high-precision hot stamping processing of ultra-thin label paper.

[0065] The label paper processed in this embodiment is a 25μm thick PE film label, which is soft and easily stretched, and is very sensitive to tension fluctuations. To address this characteristic, the buffer mechanism 2 in this embodiment adopts a three-stage buffer structure, consisting of an input buffer stage, an intermediate paper storage stage, and an output speed stabilization stage. Each stage is equipped with an independent tension detection and adjustment unit to achieve graded tension control. Input buffer section: Connects to the front end gap paper feed, mainly to absorb the impact force of paper feeding start and stop, and the tension is controlled at a large value (8N) to ensure rapid paper feeding response; Intermediate paper storage section: mainly realizes the length compensation function, tension is controlled at a medium value (5N), and balances the paper storage capacity and paper deformation; Output steady speed section: close to the hot stamping station, the tension is controlled at a small value (3N), and the tension fluctuation is controlled within ±0.1N, minimizing paper stretching deformation and ensuring hot stamping registration accuracy.

[0066] Meanwhile, in this embodiment, tension sensors are installed before and after the hot stamping component 4 to collect the paper tension before and after hot stamping in real time and feed it back to the control system for real-time adjustment, so as to ensure that the paper tension is highly stable during the hot stamping process and avoid registration deviation caused by tension changes.

[0067] Through the above optimizations, this embodiment achieves an ultra-high hot stamping registration accuracy of ±0.03mm on ultra-thin PE film labels, with no stretching or curling of the hot stamping layer, fully meeting the quality requirements of high-end film labels.

[0068] Working principle The core working principle of this invention lies in the collaborative mechanism of "buffered continuation + target search synchronization": The buffer-and-continue principle utilizes the potential energy storage characteristics of the floating roller assembly to convert the energy of the intermittently input pulsating paper into the potential energy of the floating roller, which is then slowly released during the paper feeding interval, thereby transforming discontinuous input into continuous output. This process is similar to a "filter capacitor" in a circuit, converting pulsating direct current into smooth direct current; in this case, it transforms the pulsating paper flow into a smooth, continuous paper flow, providing the necessary material basis for continuous hot stamping.

[0069] The dual-trigger stabilization principle ensures the continuity of the hot stamping process by using the "minimum continuous length" condition to avoid interruptions due to paper breakage; and ensures the accuracy of the starting position of the hot stamping by using the "label search signal" condition. The combination of the two ensures that the hot stamping process is uninterrupted and that the hot stamping position of each label is accurate, thus eliminating potential quality problems from the process mechanism.

[0070] Closed-loop synchronization principle: The paper position information is collected in real time by the tracking sensor 3 to form a position feedback closed loop. The control system dynamically adjusts the speed of the hot stamping roller according to the deviation, realizing real-time tracking and compensation of the hot stamping position. This mechanism breaks through the limitations of traditional fixed-gap positioning, can adapt to dynamic fluctuations in the paper feeding process, and achieve higher registration accuracy.

[0071] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A continuous hot stamping process for label identification, characterized in that, Includes the following steps: Step S1, Label Input: The label paper with the synchronization mark pre-printed on the surface is input into the hot stamping equipment in an intermittent manner. The label input process simultaneously meets two triggering conditions: the tracking sensor (3) senses the synchronization mark on the label paper and generates an effective detection signal; the continuous paper length at the output end of the hot stamping equipment meets the minimum continuous hot stamping length preset by the hot stamping process. Step S2, buffering: The intermittently input label paper enters the buffer mechanism (2) for length compensation and tension stabilization. Through the dynamic paper storage adjustment of the buffer mechanism (2), the intermittently input label paper is converted into a paper flow with uniform speed and continuous output. Step S3, Marker Detection: After the label paper is output through the buffer mechanism (2), the synchronous mark on the label paper is detected and identified in real time by the marker sensor (3), and the detected position signal is transmitted to the control system of the hot stamping equipment in real time. Step S4, hot stamping: After receiving the position signal from the tracking sensor (3), the control system calculates the hot stamping start position based on the position information of the synchronous marker, controls the hot stamping component (4) to start and maintain constant hot stamping pressure and temperature, and performs continuous hot stamping processing at the designated position on the label paper. Step S5, Paper Output: The label paper after hot stamping is output from the hot stamping equipment at a continuous and uniform speed, and enters the subsequent winding or die-cutting process.

2. The label-finding continuous hot stamping process according to claim 1, characterized in that, In step S1, the single conveying length of the intermittent paper feeding is 50mm~500mm, and the interval time of a single conveying is 0.2s~2s; the label paper is roll-type self-adhesive label paper, and the synchronous marks on the label paper are set at equal intervals along the paper conveying direction, and the spacing between adjacent synchronous marks is consistent with the length of a single label.

3. The label-finding continuous hot stamping process according to claim 1, characterized in that, In step S2, the buffer mechanism (2) adopts a floating roller group buffer structure, including a fixed guide roller group, a floating guide roller group and a tension adjustment unit; the label paper alternately passes around the fixed guide roller and the floating guide roller, and the vertical displacement of the floating guide roller changes the paper storage length in the buffer mechanism (2); when the label paper gap input is paused, the floating guide roller moves in the direction of decreasing paper storage, releasing the buffered paper to maintain continuous conveying at the output end; when the label paper is input again, the floating guide roller moves in the direction of increasing paper storage, replenishing the buffered paper amount.

4. The label-finding continuous hot stamping process according to claim 1, characterized in that, In step S1, the minimum continuous hot stamping length is calculated as the sum of the length of the hot stamping area of ​​a single label and the pressing contact arc length of the hot stamping component (4). The judgment logic of the two triggering conditions is as follows: the control system collects the paper storage length data of the buffer mechanism (2) and the signal status of the target sensor (3) in real time. Only when the paper storage length is greater than or equal to the minimum continuous hot stamping length and the target sensor (3) detects a valid synchronization mark, a hot stamping start command is sent to the hot stamping component (4). If either of the two conditions is not met, the hot stamping component (4) remains in standby mode, and the buffer mechanism (2) continues to maintain stable paper tension at the output end.

5. The label-finding continuous hot stamping process according to claim 1, characterized in that, In step S3, the tracking sensor (3) is a photoelectric color mark sensor, which is installed on the paper conveying path between the output end of the buffer mechanism (2) and the input end of the hot stamping component (4). The distance between the sensor and the pressing station of the hot stamping component (4) is a fixed value L. The synchronization mark is a rectangular color block mark printed on the side of the label paper. The color of the color block and the background color of the label paper form a gray difference of ≥30%. After the tracking sensor (3) detects the synchronization mark, the control system calculates the delay time for hot stamping start according to the paper conveying speed and distance L, so as to achieve accurate alignment between the hot stamping position and the label graphics.

6. The label-finding continuous hot stamping process according to claim 1, characterized in that, In step S4, the hot stamping component (4) adopts a rotary hot stamping roller structure, including a heated hot stamping roller and a rubber pressure roller. During the hot stamping process, the surface temperature of the hot stamping roller is controlled at 100℃~180℃, the hot stamping line pressure is controlled at 5kg / cm~20kg / cm, and the linear speed of the hot stamping roller is synchronized with the linear speed of the paper output by the buffer mechanism (2). The control system adjusts the rotation speed and temperature of the hot stamping roller in real time through closed-loop feedback. When the paper conveying speed fluctuates, the rotation speed compensation is completed within 0.1s to ensure the stability of the hot stamping pressure and hot stamping time.

7. The label-finding continuous hot stamping process according to claim 3, characterized in that, The maximum paper storage length of the buffer mechanism (2) is 1.5 to 3 times the paper feeding length in a single interval; the buffer mechanism (2) is also equipped with an upper limit sensor and a lower limit sensor, which correspond to the maximum paper storage position and the minimum paper storage position, respectively; when the floating guide roller triggers the lower limit sensor, the control system sends an accelerated paper feeding command to the paper feeding mechanism at the input end to replenish the buffer amount; when the floating guide roller triggers the upper limit sensor, the control system sends a pause paper feeding command to the paper feeding mechanism at the input end to avoid paper overflow.

8. The label-finding continuous hot stamping process according to claim 1, characterized in that, Step S5 is followed by a post-hot stamping processing step S6: The hot stamped label paper is first cooled rapidly by a cooling roller assembly to solidify and set the hot stamping layer. The surface temperature of the cooling roller assembly is controlled at 15℃~30℃. Then, the accuracy of the hot stamping position, the integrity of the hot stamping layer, and the gloss are inspected online by a visual inspection component to remove unqualified products. Finally, the paper is wound up by a winding mechanism with constant tension, and the winding tension is controlled at 5N~20N.

9. The label-finding continuous hot stamping process according to claim 1, characterized in that, In step S4, the control system uses a PID closed-loop control algorithm to achieve precise synchronous control of the hot stamping position, specifically including: Step S41: Pre-set the standard hot stamping offset threshold in the control system, with a threshold range of ±0.05mm; Step S42: The tracking sensor (3) collects the actual position information of the synchronous marker in real time and calculates the deviation between the actual position and the theoretical position; Step S43: When the deviation value is within the threshold range, the control system keeps the current hot stamping roller speed unchanged; when the deviation value exceeds the threshold range, the control system dynamically compensates the hot stamping position by adjusting the instantaneous speed of the hot stamping roller, so that the deviation value falls back to the threshold range.

10. The label-finding continuous hot stamping process according to claim 1, characterized in that, This process is applied to the inline hot stamping process of an intermittent label printing machine. After the label paper is printed in the printing station in an intermittent manner, it directly enters the buffer mechanism (2) of the hot stamping equipment in an intermittent output state. The synchronous mark and the label graphic are printed synchronously in the printing process, and the position of the synchronous mark corresponds to the starting position of a single label.

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