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The development and thinking of the unit type flexographic printing machine

1 the development direction of flexographic printing machine it has been no problem for the flexographic printing machine to reach the accuracy of 0.5 level in the experimental machine capital since it entered China in the 1990s. Due to the flexographic printing machine used 6 Poly (aryl ether nitrile): it is a water-based ink with high temperature resistance and high mechanical properties, so it has less environmental pollution; Moreover, flexographic plate making process is simple and fast, which has obvious advantages over gravure plate making in efficiency. It is suitable for printing medium and small batches of substrates with various varieties, and has obvious competitive advantages in the production of packaging prints. And its printing products are bright in color and far less toxic than other printing products, so it is widely used in the pharmaceutical, food, tobacco and alcohol industries, and has a rapid development momentum. It has been 8 years since Xi'an Heiniu Machinery Co., Ltd. began to develop the unit type flexographic printing machine in 1996. In June, 1998, the company first exhibited domestic models in Beijing and Shanghai, and then several domestic manufacturers gradually appeared, which greatly promoted the localization of flexographic printing machines and competed in the competition. Because the company has strong research and manufacturing capabilities, it has made many bold attempts and practices in the structural performance and functions of flexographic printing machines. Based on the eight years of practice and experience, I would like to talk about the development and thinking of unit flexographic printing machines. When you visit shopping malls and supermarkets, a wide range of goods have a beautiful outer package, ranging from the whole package of cartons to the small subcontracting boxes to the trademark descriptions inside, which are almost all good at flexographic printing machines. Due to the wide variety and size of commodity packaging, the content printed on it is based on visually striking color block patterns and certain instructions. In order to effectively prevent counterfeiting and resist counterfeiting, high-tech anti-counterfeiting means are adopted, such as hot stamping laser, non detachable technology, invisible ink technology, texture technology, code random combination anti-counterfeiting and so on. Therefore, as a process method for producing the above packaging products, it can be said that it has been or is possible to use some or all of the existing offset printing, gravure printing, flexographic printing and silk screen printing in the industry, with bronzing and laser transfer, followed by line indentation, die cutting and collection. Almost all packaging and printing products in the production process have gradually transitioned from the original segmented division of labor to the continuous use of web paper. Large carton printing is not the content of this article. I want to talk about how flexo printing technology should adapt to the production of packaging prints on a variety of small boxes and trademark production. Our company has been engaged in the production and manufacturing of unit type flexographic printing machines in recent years. Among flexographic printing machines, there is a kind of special machine, namely professional production flexographic printing machine. ① Flexo printing machine for playing card production. It is characterized by the need for positive and negative face printing, accurate alignment, and must be equipped with a non-stop uncoiling system to ensure a yield of more than 97%, reduce costs, and efficient output. ② A color flexographic printing machine for printing 0.8 ~ 1.5mm thick iron sheet. Since the iron sheet joint is about 2.0mm thick and has burrs, it can only be printed by a special mechanism with an automatic distance of 4.0mm from the press. ③ Flexographic printing machine specializing in the production of dairy packaging boxes. In addition to the non-stop structure, each group needs to be equipped with UV light source to adapt to the printing of UV ink, and there is a reverse printing group to print sealing glue. ④ Flexographic printing machine that produces anti-counterfeiting trademarks. It requires lamination and self-adhesive internal printing. ⑤ The flexographic printing machine with high-speed camera function can produce texture anti-counterfeiting trademarks. ⑥ Flexo printing machine for export pharmaceutical packaging. It requires four groups of flexographic printing and one group of gravure printing. The back side is coated with EVA hot melt adhesive and there is a 12m oven. In addition, each manufacturer requires different number and width of color decks, and more customers propose to have bronzing unit and flat die-cutting unit. Through the research and analysis of the use requirements of the customer group, if you want to professionally produce a specific product, the manufacturer can professionally design it; However, for customers who use flexographic machines with versatility and multiple specifications, flexographic machines should have modular and rapid combination functions to meet the diverse needs of customers' production. Through the production practice of the unit flexographic press, I believe that the imported Heidelberg jieras flexographic press is a typical structure in terms of modular structure. Because the printing unit on each power workstation of the gelas machine is a drawer structure, if we need offset printing, gravure printing, hot stamping, punching, reverse printing and other functions, we can produce packaging prints with multiple process requirements by selecting any combination between the units. When the China Flexible Printing Association held a technical seminar in Kunming in 2002, I made a speech, talking about that the unit type flexographic printing machine should be like the processing center of a modern machining workshop, as long as it is programmed and equipped with tools, it can do anything, and put forward the concept that the processing capacity of the flexographic printing machine is a "processing center for packaging and printing". I think the general unit flexographic printing machine should be developed in the direction of modularization, integration, generalization and multi-function, which is the development direction of the unit flexographic printing machine. The development direction of flexographic press in function has been discussed above. Now let's talk about my own thinking and the company's thinking on the function and structure of flexographic press. 2. Some opinions on the function and structure of flexo printing machine. Flexo printing machine must choose the production mode of non-stop. Flexo printing machine now mostly adopts the single station uncoiling mode, that is, it needs to stop when replacing new printing materials after using up printing materials. In addition, the waste of head and tail printing materials in re setting and some operation errors reduce the efficiency of flexo printing machine, resulting in a great waste of printing materials, especially thick printing materials. In addition, due to the flexographic press is a relief printing method, the layout must be cleaned every time it stops, which brings trouble to the operator and increases the labor intensity. Therefore, we believe that the production mode without shutdown is a required function. Moreover, gravure printing is now carried out in a non-stop manner, and flexo printing machines will significantly reduce their competitive advantage if they do not learn from the advantages of gravure printing. The transmission of 3 printing rollers (plate roller, ink transfer roller and impression roller) driven by helical gears must be stable. If any group of gears in the 3 rollers has poor accuracy, it will produce ink bars on the printed matter, which will seriously affect the quality of the printed matter. For example, the helical gear transmission of the printing 3 roll can make the transmission more stable, which is conducive to the solution of the problem. The way to avoid installing the printing plate through the shaft. According to theoretical calculation and practice, if we adopt the way of fixing the through mandrel in the printing 3 roll, it will increase the radial runout or cause vibration, seriously affect the printing quality, produce ink bars, and make the point reduction worse, resulting in the decline of the quality of the printed matter or directly unqualified products. Therefore, I think that the way of threading the shaft to fix the cylinder should be improved and changed to the method of direct bearing, which will ensure the rotation accuracy of the printing 3 roll and maintain the accuracy for a long time. Accurately control the printing material tension 15. Overload protection: automatic protection when exceeding 10% of the maximum load; At present, two-stage tension control has been widely used in flexographic printing machines to stabilize the printing registration accuracy, but many of their designs will still have the problems of registration deviation or slow registration return when the mechanical speed is increased and decreased. I think that in addition to the closed-loop control, the two-stage tension control should learn from the advantages of the four-stage control of the gravure press, so that the tension fluctuation before entering the printing is ≤ 1%, and when there is an increase or decrease speed after the optimization design, the tension is ≤ 2%. In short, the response should be more sensitive and reliable, so that the machine can still meet the requirements of overprint accuracy when accelerating and decelerating. The drying system for rapid replacement of infrared and ultraviolet devices flexographic printing machines often encounter full UV printed prints, and their drying systems should be able to be exchanged quickly to meet the requirements of different inks and different prints. It is required to carry out integrated and modular design and manufacturing of the drying system, which has the use performance of rapid combination. In addition, the electrical control should be input by speed and gear to match the printing and drying power. Multifunctional printing process unit because flexo printing machines need to print all kinds of packaging materials, and all kinds of packaging materials need different processes, it is necessary to develop and install multi-functional printing processing units on flexo printing machines, such as positive and negative printing, perforated folding, gravure printing, gravure sanding, foaming, round wire printing, ordinary bronzing and laser positioning ironing, UV transfer printing, flattening and circular die cutting. Each power workstation of the shaftless flexographic press is driven by an independent AC servo motor, and at the same time, according to the printing phase requirements, it automatically completes the timely correction of the plate quantity in motion. Adopting shaftless transmission makes modularization and flexible assembly more convenient and fast, which is the development direction of flexographic printing machine in the future. After adopting shaftless transmission module unit, customers can choose to increase or decrease at will in the development, which greatly improves the positioning accuracy of customers' choice, and also provides convenience for customers' future development

3 our company has improved the design of flexographic printing machines for many years. The unwinding mechanism of flexographic printing machines produced at home and abroad is mostly single station unwinding, that is, when each roll of printing materials is exhausted, it needs to stop and change the roll. Such a method is time-consuming and wasteful. When restarting, the operator is in a hurry and runs at normal speed after registration. The head and tail losses of each roll are not negligible, which wastes printing materials, ink, electricity, mechanical efficiency, and the feelings of operators. Especially when the flexographic printing machine uncoiles and prints prototype materials in a single station, the accumulated losses can reach hundreds of thousands of yuan every year. Although waste lies in users, it hurts our manufacturers. Demand is the market. Our company has rapidly developed a double station uncoiling system without stopping. The problem of continuous operation of flexographic printing machine is solved, and the users of flexographic printing machine reduce waste and improve efficiency. The non-stop uncoiling mechanism not only matches the flexographic printing machines produced by the company, but also configures more than ten sets of flexographic printing machines imported by domestic printing enterprises. The combination of gravure printing and flexographic printing. Because the flexographic printing machine uses the ceramic corrugated roller as the ink transfer quantitative roller, the metal ink cannot transfer the metal powder in the metal ink well due to the limitation of the hole size. Due to the lack of ink load, it is far from being compared with the ink load of gravure printing, so the effect of flexo printing gold and aluminum is very poor, and the gloss is not strong or even black, which cannot be compared with gravure printing. Yunnan Dali Yixiang company and Yunnan Kunming color printing factory respectively invested in flexographic printing machine to print cigarette packaging, and the substrate is tipping paper. Because cigarette tipping paper needs to be printed with continuous single gold wire and double gold wire, and with small metal ink text, the quality requirements of products cannot be met by flexographic printing machine. Entrusted by the two companies, our company has added gravure printing units on one yajiafa machine and one mcandi machine respectively. Since the imported original machine cannot be disassembled and transformed, we adopt the synchronous operation mode of shaftless electronic transmission. When flexo printing and gravure printing are stopped, the way of moistening the plate is different, so the version memory technology is adopted to solve the quality problem of the two tipping paper printing. Our company also equipped gravure printing units for yajiafa and jieras flexographic printing machines of Baoji and tianwai enterprises for gravure printing on their printed materials. Gravure printing foaming process in flexo printing foaming products are printed with special UV foaming ink through silk printing, which can meet the requirements of thicker ink layer. If the gravure plate is made into a large ink printing plate by corrosion method, can it achieve the effect of frosted foaming? I