High scrap rate in cigarette pack hot stamping; improving this device can effectively reduce it!
Currently, in the company where I work, during the 3D hot stamping process of cigarette pack products, the machine often needs to be stopped due to pressure being too high or too low. The stamping base has to be pulled out repeatedly to adjust the pressure. Additionally, when searching for the position where the pressure needs adjustment and the specific adjustment method, a certain amount of time is consumed, which generates hot stamping scrap. Moreover, because operators cannot directly locate the pressure compensation areas, they need to repeatedly search and stop the machine for adjustment. During this process, the stamping temperature changes, resulting in hot stamping scrap, as shown in Figure 1. The above factors directly affect the production efficiency and finished product yield of cigarette pack production.
Figure 1 Foil Stamping Waste
Problems with Existing Methods
The current method of three-dimensional foil stamping pressure compensation mainly involves directly attaching the pressure-compensation paper to the back of the resin mold ① in Figure 2, and then using glue to attach it to the foil stamping base plate ②, thereby achieving pressure adjustment (pressing) during the foil stamping process. If the pressure during the foil stamping process does not meet the process requirements, the entire resin mold needs to be lifted. Then, according to a comparison of the product's foil stamping effect with the area of pressure that needs adjustment, the corresponding position is found. Next, the pressure-compensation paper is attached to the back of the resin mold ①-2 and glued to the foil stamping base plate ② to achieve pressure compensation.
Figure 2 Schematic diagram of the original three-dimensional stamping compensation pressure device
During this process, the position of the resin base mold and the stamping die may change, so it is necessary to repeatedly check and adjust the position, resulting in a long adjustment time and an increased likelihood of stamping defects due to inaccurate positioning. At the same time, due to repeated adjustments, the bottom layer paper can also become deformed and damaged, which affects the overall stamping effect. The side view of the original three-dimensional stamping compensation pressure device is shown in Figure 3.
Figure 3 Side view of the original three-dimensional hot stamping pressure compensation device
Additionally, due to differences in the technical skills of operators, the timing and effectiveness of three-dimensional hot stamping pressure compensation may vary.
Feasibility Analysis and Verification
During the use of the original positioning device, taking the "Seven Wolves (Blue)" cigarette pack small box as an example, there are a total of 36 stamping positioning devices for an 18-piece product. Adjusting the pressure generally takes 7–9 hours or even longer. Each adjustment can cause misalignment between the resin bottom mold and the stamping base plate, requiring repositioning and adjustment, which is time-consuming. Meanwhile, during the stamping process, the stamping pressure directly affects the stamping quality. If the pressure is too high or too low, defective stamps are produced, such as stamping pitting, incomplete stamping, or gold fly-off. Therefore, machine stoppage is required to identify areas needing pressure adjustment and make corresponding adjustments. The area to be stamped usually accounts for a small proportion of the overall product surface, meaning the adjustment area is small and changes frequently, requiring considerable patience for repeated pressure adjustments. Repeated stoppages of the hot stamping machine directly affect equipment temperature, and if the temperature is too high or too low, defective stamping will occur. Therefore, the chosen device materials must be heat-resistant, stable, and not easily deformed or damaged during repeated flexible adjustments and movements.
By analyzing the above-mentioned problems, the project team optimized and upgraded the original resin materials and product performance. It is planned to use a resin material positioning device that allows rapid pressure adjustment, which uses a composite structure to fix part of the positioning structure material, while changing the core area into a movable or flexible mechanism. The overall structure is based on a fixed part as the base, with a movable part embedded within it. This allows three-dimensional hot stamping pressure compensation during the pressure adjustment process, effectively shortening pressure adjustment time and reducing machine adjustment waste.
Additionally, to solve the problem of repeatedly identifying areas for pressure compensation adjustments, the device needs to incorporate basic pattern lines of the stamping design. Based on these considerations, in the overall material selection, in addition to the fixed resin bottom mold, the project team also uses frequently used cardboard for cigarette packaging as the base fixed part (the overall design is mainly trapezoidal to ensure the connection between fixed and embedded structures), prepares a certain amount of translucent tracing paper (with the content to be stamped printed on its surface), as well as a copper sheet buffer layer. Finally, this forms an embedded device capable of rapid compensation for three-dimensional hot stamping process pressure. The material breakdown diagram and the actual application perspective views are shown in Figures 4 and 5.
图4 嵌入式快速补偿立体烫印工艺压力装置的材料分解图
Figure 5 Perspective View of the Actual Application of the Embedded Rapid Compensation Three-Dimensional Hot Stamping Process Pressure Device
In Figures 4 and 5, material ①, the resin mold base layer, has an overall frame size consistent with ④ cardboard or the base paper to be stamped. Its main function is to ensure the first layer fully bonds and aligns with the base layer, protecting the embedded devices and material properties of ② and ③.
Material ②, the tracing paper layer, is absorbent and can absorb moisture generated from heat during the stamping process while ensuring it does not deform or get damaged. At the same time, the tracing paper material layer needs to be printed or drawn according to the pattern on the resin mold. Depending on the presentation effect of the product's stamping area, it can directly locate the areas where pressure adjustment is needed, reducing search and adjustment time, lowering scrap rates, and improving production efficiency.
Material ③, the copper sheet, has a certain toughness and can act as a buffer during the stamping process. It protects the resin mold from cracking and facilitates the removal and insertion of the tracing paper layer.
Material ④, the cardboard or base paper to be stamped, is designed with cutouts. The cutout areas correspond to the appearance areas of materials ② and ③, forming a complete embedded slot design with ④, keeping the position fixed without shifting or deforming. The overall adaptability of material ④ better matches the requirements of the stamping process. After the first-time attachment based on registration with the stamping plate, this material layer is no longer moved or operated during subsequent pressure adjustments and can be directly fixed on the stamping base plate.
Actual Effectiveness of the Improved Scheme
The improved positioning device first solves the issue caused by the conventional pressure compensation method, where lifting the resin mold overall leads to repeated adjustments and misalignment with the stamping plate, reducing scrap due to misaligned stamping. Secondly, the embedded structure, while ensuring overall alignment stability, allows for the copper sheet and tracing paper to be pulled out for corresponding pressure compensation, reducing the time required to adjust alignment and locate areas needing pressure adjustment. Moreover, the overall embedded design, based on material selection, can minimize the need to remanufacture the positioning device due to water absorption, improving device utilization.
The disassembly diagram of the embedded rapid compensation three-dimensional hot stamping pressure device is shown in Figure 6, with specific functions as follows: using an embedded approach and the embedded structure of different material layers for flexible pull-out (pull-out part expanded in Figure 7), the composite structure of tracing paper (with stamped text and images) and copper sheet can be directly pulled out according to adjustment needs for corresponding adjustments, achieving ease of operation and repeatable use. The synthesis diagram of the embedded rapid compensation three-dimensional hot stamping pressure device is shown in Figure 8.
Figure 6 Exploded View of the Pressure Device for Embedded Rapid Compensation Stereoscopic Hot Stamping Process
Figure 7 Pull-out Section Expanded View
Figure 8 Schematic Diagram of the Embedded Rapid Compensation Stereo Hot Stamping Process Pressure Device
In the actual production process, the resin base film material layer and the cardboard portion constitute a fixed trapezoidal area. When pulling the composite structure of the sulfuric acid paper and the copper sheet, pressure compensation on the sulfuric acid paper can be adjusted according to the quality of the stamping area on the product. Material characteristics such as the water absorbency of the sulfuric acid paper and the toughness of the copper sheet are not easily deformed or damaged during repeated pulling, protecting the resin base mold from cracking while maximizing the stability of the overall stamping device effect. Additionally, the fixed trapezoidal area ensures the positional accuracy of the entire device, preventing misalignment.
After a period of stable operation, the new positioning device (as shown in Figure 9) has been applied in the production process of the company's "Seven Wolves (Blue)" cigarette pack small boxes. The positioning device demonstrates significant effect, with pressure adjustment time stabilized at 2–3 hours, representing a reduction of approximately 71.43% compared to the previous time, achieving the expected goal and improving efficiency.
Figure 9 Schematic Diagram of the Overall Installation of the Embedded Rapid Compensation 3D Hot Stamping Pressure Device
In addition, in practical application of the device, because the pressure is stable and the pressure adjustment time is reduced, the temperature changes caused by shutdown during hot stamping are minimized, and hot stamping waste has been significantly reduced, improving the yield. The annual hot stamping waste proportion of the "Septwolves (Blue)" cigarette pack small boxes among all waste decreased from a peak of 24.87% to 4.75% in 2025, effectively reducing the hot stamping waste rate.
The above practice demonstrates that the embedded rapid compensation 3D hot stamping pressure device has advantages such as reasonable structure, low manufacturing cost, and simple installation and operation. This device can also be applied to other scenarios, showing certain promotional value in the hot stamping process.