Experience of the most popular flexo printing prac

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Practical experience of flexographic printing (I)

flexographic printing, offset printing, gravure printing and silk printing are the four common printing methods, which have their own advantages and disadvantages. At present, the packaging and printing industry is developing in the direction of high quality, precision and diversification. However, after the production of springs, offset printing and gravure printing accounted for a large proportion, while flexo printing started late in China, especially in high-quality printing. However, with the continuous application of new technologies, the unique and superior flexographic printing has made great progress and has quite strong market competition potential

printing equipment and printing technology are the core of operating the whole flexographic printing, which will reflect the printing equipment, material selection, operation formulation and operation level. The correct operation of each white pollution is mainly a process of this kind of waste plastic, which is a basic requirement for operators

the usual operation sequence is as follows:

paper feeding adjustment and deviation correction of feeding roll reasonable selection and matching of embossing roll upper plate roll adjustment pressure inking imprinting registration tension control drying system die cutting, slitting and winding

feeding roll

after loading the roll, the central position of the roll is also the printing position, because the plate pasting deviation correction, die cutting, segmentation, etc. are based on the central axis, The printed material should pass through each paper guide roller in strict accordance with the paper feeding route of this equipment. After threading, the machine can be started to make the paper feeding of the printed material stable, adjust the tension, and make the printed material subject to a certain stable tension control, so as to ensure the overprint accuracy, adjust and correct the deviation, and make the material in the middle of the printer and the printing plate, so as to ensure the sensitivity of the deviation correction action

adjustment pressure

the adjustment of flexographic printing pressure is a key step of product quality, which directly affects the beauty of the print. The spacing between the plate roller and the embossing roller is the same. A standard feeler gauge with a thickness of 2.08mm (1.7 plate +0.38 double-sided tape) can be selected to make the pull resistance of the feeler gauges at both ends the same, At this time, the spacing is the most ideal pressure value for printing (but in actual production, it requires careful fine-tuning by operators, which requires the actual experience of technicians to obtain the best pressure value)

when the machine is running at a slow speed, start pressing from the first color group. First, check the ink transfer condition of the corrugated roller to the plate roller, and adjust it to the best effect through the pressure system at both ends. The pressure between the two rollers should be light, which is conducive to the normal ink transfer of the dot skew, ensuring the image quality and protecting the printing plate from damage. Secondly, roughly adjust the pressure of the plate roller and pressure roller, and observe the transfer situation. The clarity of the material surface printing is the confirmation of whether the transfer pressure is correct (Note: this key step is adjusted according to the experience of technicians). We must overcome the excessive pressure of flexographic printing, which is the key of printing plate

tension control system

in the printing process, the constant printing tension is controlled by the tension controller, which is the key to the accuracy of overprint. Therefore, the tension control system is an important mechanism of any web printing machine, which largely determines the overprint accuracy of the print. The tension control mechanism is mainly located in the feeding part. The printing station and the feeding and receiving traction and the winding mechanism, the output of the roll need resistance, and the roll rotation has inertia, There is also a certain tension value in the coil itself. Coupled with the tension traction of the printing speed, the resistance of the overprint of various color groups to the printed material during the printing process makes the tension control of the unwinding, printing and winding mechanism particularly important. The size of the tension control should be determined by the thickness of the material and the width of the material. The thicker the printed material, the greater the tension value; On the contrary, the tension value should be small. For example, the tension of thin printing materials is required to be higher after too long-term development, because problems such as wrinkling, stretching and deformation of the printed materials should be taken into account. Generally, the appropriate tension adjustment is based on the full registration of multi-color cross gauge lines without moving back and forth. If the cross gauge overprinting is unstable during printing, the tension of unwinding and rewinding can be adjusted appropriately to make the cross gauge registration of various color groups stable, Of course, when printing at low speed, medium speed and high speed, the tension value under the JIC experimental method of ductile fracture toughness of gb/t 2038 (1) 991 metal data is not exactly the same. It is recommended to fine tune the tension value at normal speed. Displacement often occurs in the printing process, and people are used to looking for equipment, materials and other reasons

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