People in the printing industry are relatively clear that the ink used in flexo printing machines is water-based ink, which has less environmental pollution, and its packaging and printing products are beautiful and bright. Especially the customers in the food and pharmaceutical industries must use flexible printing to print their packaging. Because the flexo printing machine has the advantages of the above two aspects, it is squeezing the share of the offset printing market, and it competes with gravure printing because of its rapid plate making. However, the printing method used by the flexo printing machine determines that its ink load is lower than that of gravure and silk screen. Although the quality is significantly better than offset printing when printing large solid pattern color blocks, when printing gold and silver ink, due to the amount of ink Insufficient, the printed product is dull and dull, and can not be compared with gravure printing.
1 Solved the quality requirements when printing gold, silver and ink
Yunnan Dali Yixiang Company imported a Canadian flexographic printing machine from Jakarta to print cigarette tipping paper. Because it is necessary to print continuous single gold lines or double gold lines on cigarette tipping paper with gold ink, and print gold lettering next to the gold line, but flexo printing has long been unable to compare with the gravure printing in brightness of gold printing ratio. Due to the thin ink layer, the metallic luster of the printed gold ink is not strong and black. When the product quality requirements cannot be met, a gravure printing unit has to be added to the flexo printing machine to print gold.
Our company has undertaken this research and manufacturing task. Generally it is not very complicated to add a gravure printing unit to a flexo printing machine, but because domestic companies add gravure printing units to imported equipment, there are several technical problems that need to be solved: the original machine structure and relative position cannot be disassembled and changed, only the unit The space between the additional units is increased; the increased unit power cannot be obtained from the original machine power, and only the AC servo motor can be used to achieve shaftless synchronous rotation; in addition to printing synchronization with the original unit, the gravure printing group should also be equipped with an automatic version matching function.
Because the flexo printing machine stops during normal work, the host does not drive after the pressure is released, and only the ceramic ink transfer roller is performing ink leveling; during the second pressing operation, the phase of each printing plate remains unchanged before the printing operation can be performed. When the gravure printing machine is depressurized, the gravure plate must slowly rotate the dampening plate. Although the gravure plate rotates when the multi-color gravure printing machine is depressurized, they are all synchronized. Register. In the combined printing of flexo printing machine and gravure printing machine, a procedure must be set, that is, no matter how long the operation is stopped, the gravure printing group must be returned to the phase before the shutdown after the dampening group is transferred to the printing before printing. This can ensure that the registration state is not destroyed by dampening.
After careful planning and design, the company carried out processing and installation, and the effect of Yixiang Company is very good. The company subsequently made the same technical transformation for Kunming Color Printing Factory, Baoji Cigarette Factory and Huzhou Tianwai Printing Enterprise.
2 Solve the needs of frosted foaming process and dark flower transfer polishing process
The practice of adding a gravure printing unit to the flexo printing machine of domestic customers has proved that gravure printing is a supplement to flexo printing, which is very necessary for the printing of thicker ink layers. Therefore, in the flexo printing machine produced by our company Added gravure printing unit. In addition to the normal gravure printing process, it also addresses the need for frosting, foaming processes, and the need for glaze transfer.
Judging from the current development of domestic packaging and printing, many packaging and printing adopt the matte and foaming process, and the latest UV varnish laser dark flower transfer process has appeared. These process requirements put forward higher process requirements for flexographic printing machines. Therefore, our company's technicians believe that modern flexo printing machine should not only have flexo printing function, but also become a packaging and printing processing center that integrates reverse printing, gravure printing, dark pattern transfer, matte, foaming, and in-line bronzing functions. Among the functions discussed above, in addition to meeting the needs of thick ink layer printing, the gravure printing process can also perform several functions of frosting and foaming, and dark transfer printing. It is an indispensable workstation for flexo printing machines.
The frosting and foaming process of packaging printed matter was first completed in the flat screen printing process. Because the UV foam ink can produce a raised effect under the irradiation of ultraviolet rays, it will produce many strange effects, so it is widely used in packaging printed matter, especially in 1997-1998. However, since the screen works under intermittent operations, its production efficiency is far from comparable to flexo and gravure. Later, foreign countries introduced round screens. It can be used for silk screen units on flexo printing machines, such as the Dutch Stocker. In addition to the 120,000 euros required for this unit, due to the high manufacturing cost of the round screen version, and the lack of popularization in the country, and the screen printing durability of the screen version cannot exceed 30,000 rpm, and the flexo version of 1 million rpm and concave Inability to match 10 million revolutions will also reduce efficiency and increase costs, so we believe that although the round screen screen is successful in the process, it is limited to the technical test stage. Large-scale high-efficiency is popular in the printing industry. It's far away.
Our company has made a bold exploration on the use of gravure frosting and foaming ink. The gravure foaming operation used in Huzhou Tianwai enterprises has been successful, and the company has conducted a moderate degree of gravure with high ink load in the factory. The frosted foam test was also successful. Through the test, we believe that it is feasible to use the gravure printing unit for frosted foam printing operations, micro-foaming and moderate foaming. Proper adjustment of UV intensity can also achieve matching with flexo printing speed. The gravure has a long service life, which can be matched with other printing plate groups, which does not affect the printing efficiency, and at the same time greatly simplifies the foaming process, which greatly reduces the cost. In addition to printing with a large amount of ink, the replacement of the heater can also be used for frosting and foaming. This method has better applicability than the circular screen process and is worthy of promotion.
Shenzhen Weichengye took the lead in introducing the dark flower transfer process in China. In this process, when the printed matter is glazed, the PET film with the laser pattern is directly coated on the un-dried UV varnish. Because the PET film is transparent and has little effect on the penetration of ultraviolet rays, pass After the UV drying, the PET film is stripped off. The dried print surface is formed with dark flowers due to the transfer of laser indentation. It has beautified packaging and an effective anti-counterfeiting function within a certain period. This function can be added if the functions of unwinding and rewinding of the laser film are added before and after the gravure printing unit of the flexo printing machine, and an ultraviolet drying device of appropriate strength is added at the same time.
In summary, adding a gravure printing unit to a modern flexo printing unit can make the product suitable for different process requirements and achieve the expected quality effect of the product. Our company will launch a newly designed flexographic printing press in mid-2004. The machine adopts a two-stage closed-loop tension control system to make the registration more accurate, the lifting speed returns quickly, and each workstation can be quickly changed, so that flexo printing, gravure printing, dark pattern transfer, frosting, foaming, reverse printing, round Various methods of modern printing operations such as round hot stamping can be realized at will in the new flexo printing machine. The whole machine adopts modular design and wireless remote control, making it a processing center for packaging and printing. Gravure printing assumes several of these functions and is one of the essential stations in flexo printing units.
Puyang Optimus Household Products Co., Ltd , https://www.magicspongecn.com