At present, the production of hot stamping plates mainly uses photographic etching technology and electronic carving technology, with commonly used materials being copper or zinc plates. The copper plate material is delicate, and the surface smoothness and heat transfer effect are better than zinc plate. Using high-quality copper plate can improve the glossiness and outline clarity of hot stamping images and texts. The traditional photo etching technology for making hot stamping plates is simple and cost-effective, mainly used for text, bold lines, and general images; For fine-grained and unevenly sized hot stamping plates, secondary etching or electroengraving technology should be used. The production of electroengraving hot stamping plates can express rich and delicate hierarchical changes, greatly expanding the packaging performance ability. This process is beneficial for environmental protection, but the investment in electroengraving equipment is relatively large, and the depth of engraving is not ideal enough, which can easily cause hot stamping "pasting". The production technology requirements for holographic anti-counterfeiting hot stamping plates are relatively high. Previously, they were mainly produced in Taiwan or abroad, with a longer plate making cycle and were only used for packaging fixed and large quantities of products. At present, there are several units in China, including Shanxi Yuncheng, Beijing, and Shanghai, that can produce.
2、 To do a good job in ironing equipment, one must first sharpen the tool
The selection of stamping equipment is a key factor in determining the quality of stamping. There are three types of sheet metal stamping machines: flat press, circular press, and circular press. Currently, the most widely used are flat press machines, mainly including Shanghai Yahua Printing Machinery Co., Ltd.'s tym series die-cutting and stamping dual-purpose machines, Tangshan Yuyin Group Company's tyml020 automatic stamping and die-cutting machines, and Tianjin Youheng Machinery Industry Company's mk series automatic stamping and die-cutting machines, with a maximum stamping speed of 5000 sheet hours. The German Stona Folljetfbrl04 hot stamping machine is a representative of circular stamping. Using the design concept of offset printing machines, the maximum hot stamping speed can reach 10000 sheet hours. Currently, it is the fastest single sheet hot stamping equipment in the world. The three stamping methods of round stamping, round flattening and flat flattening have their own advantages and disadvantages: round stamping and round flattening hot stamping are performed under linear pressure, with low Total pressure. Large area field gilding can be easily completed with relatively small pressure. The movement is stable, and the round stamping production efficiency is high, which is especially suitable for large quantities of live parts gilding. However, because the processing of the copper plate arc surface is difficult, the production cost is high, and the heating drum is also more difficult than the plane heating. The flat pressing operation is flexible and convenient, making it more suitable for short version products. Compared with imported stamping equipment, domestic stamping equipment has a significant advantage in terms of functional price. The price of domestic machines is only equivalent to 15-14% of the price of similar foreign products. However, the printing accuracy, stability, and functionality of imported machines are significantly better than domestic machines, and they are also more durable and suitable for processing fixed batch high-end packaging products. Therefore, product type and batch size are the key factors determining the selection of stamping equipment. Possessing high-end hot stamping die cutting equipment such as BObst has become the preferred prerequisite for customers in the industry.
3、 Stamping suitability
The adaptability of the flat press die-cutting machine refers to the selection of the model of anodized aluminum and the matching between factors such as stamping speed, temperature, and pressure. Accurately grasping the suitability of stamping is the most important means to improve the quality of stamping when hardware such as equipment is fixed. Below is an analysis of some quality issues reflected in actual operation, in order to scientifically grasp the suitability of hot stamping.
1. Inadequate or inaccurate hot stamping is related to various factors such as the surface characteristics of the printed piece, the properties of anodized aluminum, hot stamping temperature and pressure.
Excessive powder spraying on the surface of the printed piece or the presence of additives such as adhesive remover and gloss paste on the surface will hinder the adsorption of anodized aluminum on the paper. Solution: Surface powder removal treatment or solution in printing process. Improper selection of anodized aluminum directly affects the fastness of hot stamping. Based on the size of the hot stamping area and the characteristics of the hot stamping material, a comprehensive consideration should be given to which model of anodized aluminum should be selected. The domestically produced anodized aluminum is mainly the Peacock series produced by Shanghai Shenyong Hot stamping Materials Co., Ltd. The imported anodized aluminum is mainly the PM and LK series from Kurz, Germany, the A, K, H series from Japan, and the SP series from Kolon, South Korea. According to our practice and testing, the selection of anodized aluminum can mainly refer to the following categories: the hot-stamping anodized aluminum on ordinary products can be classified into 88-1 type and Kurz pm type; There are 88-2 types of gilded anodized products for thick ink printed products such as cigarette packs and cosmetics (including gold and silver printing); There are 88-3, 88-4, and PM288 types of anodized aluminum used for fine handwriting hot stamping on cigarette labels, cosmetics packaging, and other products; There are 88-4 types, k series, lk series, and sp series of hot stamping anodized products suitable for paper overlaid with OPP or PET, as well as paperboard and glossy paper with UV ink. Failure to accurately grasp the matching between hot stamping equipment, hot stamping time, and hot stamping temperature affects the fastness of hot stamping and the clarity of image and text contours. Due to different equipment and materials used for hot stamping, the hot stamping time and temperature vary. For example, if a high-speed circular pressing machine is fast and the printing line is in contact, the hot stamping temperature should be higher than that of circular pressing or flat pressing. In general, the temperature for round stamping is between 190 ℃ and 220 ℃, for round stamping, it is between 130 ℃ and 150 ℃, and for flat stamping, it is between 100 ℃ and 120 ℃. Of course, the hot stamping time, hot stamping temperature, and production efficiency are largely constrained by the transfer function of anodized aluminum.
2. Pull back refers to the process of removing printing ink or varnish from printed parts by anodizing after hot stamping. The main reason is that the ink on the surface of the printed product is not dry or the surface of the printed product is not properly processed, resulting in poor adhesion between the ink, UV oil, and the surface of the paper. Solution: Wait for the printed product to dry before hot stamping. Additionally, anodized aluminum with low separation power and excellent heat transfer properties can be selected.
3. Paste and discoloration of anodized aluminum after hot stamping are mainly caused by poor production of the hot stamping plate, loose installation of anodized aluminum, or inaccurate foil walking of anodized aluminum. The discoloration of anodized aluminum after hot stamping is mainly caused by excessively high hot stamping temperature. In addition, wrinkling of anodized aluminum can also cause uneven color stacking and discoloration during hot stamping, which can be solved by appropriately lowering the temperature. For round press flat models, a fan can be installed at the foil feeding point to keep the foil flowing and prevent the anodized aluminum from touching the hot stamping plate and scorching before hot stamping.
4. Improper process layout has damaged the surface gloss of anodized aluminum, resulting in blurry graphics and text contours. For hot stamping that requires lamination processing, people often worry about the gold foil being easily rubbed off and then hot stamping before lamination, which can easily cause:
① Thin films (especially matte films) can damage the surface gloss of anodized aluminum, so it is not advisable to use water-soluble adhesive to cover the film, otherwise it will cause the surface of anodized aluminum to blacken, and it is also easy to cause gold powder to stick to the edges of the image and text, causing the phenomenon of blurring.
② After hot stamping, the depression is caused by pressure, and in addition, the glue is not easy to penetrate and seep out of the surface of the anodized aluminum, which can easily cause the separation of OPP and paper at the hot stamping area and affect product quality. The accurate process is to first cover the film before hot stamping, and choose the anodized aluminum that matches the OPP.
In short, there are many factors that affect the quality of hot stamping. Making high-quality hot stamping plates and accurately grasping the suitability of hot stamping are the key to improving the quality of hot stamping.