Gold stamping
Gold stamping process
Gold Stamping Technology is a special printing process without the use of ink. The term "gold stamping" refers to the process of applying an electro-aluminum foil to the surface of the substrate under certain temperature and pressure conditions. The gold stamping machine is the equipment that completes the gold stamping process.
Gold stamping principle
The main principle of this process is based on the heat transfer principle. Under the action of compression, the electro-aluminum comes into contact with the stamping plate and the substrate. Due to the heating of the electro-heating plate, the stamping plate acquires certain heat, and the electro-aluminum is heated, causing the thermoplastic dye resin layer and adhesive to melt. The adhesive force of the dye resin layer decreases, while the special heat-sensitive adhesive melts and increases its adhesion. The aluminum layer is peeled off from the electro-aluminum base film and transferred to the substrate at the same time. With the removal of the pressure, the adhesive rapidly cools and solidifies, and the aluminum layer is firmly attached to the substrate, completing the gold stamping process. From the composition of the electro-aluminum and the mechanism of stamping, to achieve the ideal gold stamping effect, the electro-aluminum foil used for stamping must meet the following requirements: the base coating is uniform without obvious color differences, color stripes, and color spots; the base coating layer is uniform, smooth, white, and free of impurities, with no obvious stripes, sand spots, or oxidation phenomena; good gloss; strong adhesion; high clarity; correct model.
Due to the quality, specifications, and models of the electro-aluminum foil, it will affect the stamping quality. Therefore, scientifically and reasonably selecting the electro-aluminum foil is the prerequisite for improving the quality of the gold stamping process.
Determining factors
The perfect gold stamping effect mainly depends on the level of coordination among temperature, pressure, and stamping speed. Therefore, to control the gold stamping quality, it is necessary to master the reasonable temperature, pressure, and stamping speed. This creates favorable conditions for gold stamping and can ultimately ensure the quality of gold stamping.
Gold stamping machine temperature
Temperature has a very important influence on stamping. The temperature must be controlled within the corresponding range to ensure that the dye resin layer and adhesive are moderately melted, so that the aluminum layer can be transferred well. If the temperature is too high, the melting is excessive, and the electro-aluminum in the surrounding area of the stamped image also melts and falls off, resulting in a smudging plate. At the same time, high temperature will cause chemical changes in the electro-aluminum dye resin and the aluminum layer, reducing the brightness and metallic luster of the stamped product, and even causing fogging or blistering of the print. However, if the temperature is too low, the melting is insufficient, which will also cause the stamped image not to be printed or not to be firmly attached, resulting in unstable prints, easy detachment, or missing strokes, blurring of the print.
Gold stamping machine environment
The machine should be installed in a dry, ventilated, well-lit, and easily operable place.
Gold stamping Machine Pressure
The transfer of the aluminum layer during gold stamping must be completed through pressure. The size of the Stamping Pressure affects the adhesion strength of the electro-aluminum. Even if the temperature is appropriate, if the pressure is insufficient, the electro-aluminum cannot be well transferred to the substrate, resulting in problems such as weak prints, plate smudging, etc. On the contrary, if the pressure is too high, the compression deformation of the backing and the substrate is too large, and the print will become coarse, even sticking together, smudging, etc. Generally, the stamping pressure should be appropriately reduced to ensure no color fading and good adhesion. Adjusting the stamping pressure should be comprehensive considering the substrate, stamping temperature, speed, and the electro-aluminum itself. Generally, for paper with strong texture, high smoothness, thick ink layer, and higher stamping temperature and slower speed, the stamping pressure should be smaller; conversely, it should be larger. The stamping pressure must be uniform. If it is found that the stamping does not occur or is not firmly attached, it is likely that the pressure is too low at that location. A thin sheet of paper should be placed on the plate to make the pressure balanced. The influence of the backing on pressure is also significant. A hard backing can make the print elegant, suitable for strong and smooth paper such as coated paper and glass card paper; while a soft backing is the opposite, the print is coarse, suitable for large-scale stamping, especially for paper with uneven surface, poor flatness, and roughness. At the same time, the installation of the stamping foil should not be too tight or too loose. Too tight will cause missing strokes and broken lines; too loose will make the print unclear, smudging, etc.
Gold stamping machine speed
The stamping speed actually reflects the contact time between the substrate and the stamping foil during the stamping process, which directly affects the stamping durability. If the stamping speed is too fast, it may result in incomplete stamping or a blurring effect on the printed image; if the stamping speed is too slow, it will not only affect the stamping quality but also the production efficiency. During the stamping process, the speed, pressure, and temperature are mutually restrictive, and the process parameters are always determined in the order of stamping speed, pressure, and temperature. First, the stamping speed is determined. Generally, it is treated as a constant and is not easily changed. Then, the corresponding stamping pressure and stamping temperature are found, which can simplify the operation procedure and make it easier to control the stamping quality. In addition, during the stamping process, the suitability of the substrate, stamping plate, stamping machine, fixtures, and backing plate should also be considered. Finally, the environmental conditions, including indoor temperature and humidity, substrate temperature, and the cleanliness of the indoor air (dust content), should also be studied. In conclusion, stamping is a complex technical process. Only by grasping these issues during the stamping process can satisfactory stamping results be achieved.
The heat-pressed foil and holographic aluminum foil are composed of multiple layers. These layers include a polyester isolation layer, a release layer, several layers of paint, a mirror layer, a metal layer, and an outer adhesive layer. During the stamping process, a heated Stamping Mold presses the foil firmly onto the substrate, which is supported by the plate or corresponding rollers. Due to the combined effect of pressure and adhesive activation, the foil adheres to the substrate. In addition, the heat-melt release layer also plays a role in this process. The majority of the stamping modules are made of brass and are etched or carved by hand or through a CNC system.
All stamping machines can be independent offline devices or connected to printing machines or other devices. The stamping machine mainly accepts single-sheet feed, and some high-speed stamping machines accept roll paper feed. Whether it is a sheet or roll paper feed, a complex control system is required to position the substrate and foil between the plate or roller. This allows the stamping mold to be clamped and a reverse force to be applied.
The operation of the flat-flat stamping machine is similar to that of the flat-pressing die cutting machine. Some equipment can have interchangeable functions, while others can only be used for stamping printing. In flat-flat stamping, the stamping film plate is not attached to a honeycomb plate (with different positions) but is fixed at a fixed position on a metal plate to repeat the task. Regardless of which film plate is used, the paper and aluminum foil will be brought into the position between the film plate and the lower plate for alignment. It either lies flat for planar stamping or is placed in the corresponding part of the module for concave-convex stamping. This machine combines the upper and lower parts and applies uniform and consistent pressure throughout the sheet.
