Precautions in the printing process of the hottest

Precautions in the printing process of box products

our company is a printing enterprise focusing on cigarette packets and medicine box packaging. With the development of China's packaging and printing industry and the wide application of flexographic printing in packaging and printing, in order to improve the efficiency of enterprises and protect the environment, our company successively introduced two pioneer 1800 seven color and eight color narrow flexographic printing production lines from American townsman company from 1996 to 1998

flexographic printing belongs to pollution-free green printing, which has developed rapidly. Its scientific and technological content is also constantly improving. At present, for us, the study of the new technology and process of flexographic printing has just begun. In order to master the new technology of flexo printing, it took us a long time to study and explore, and the operation of the equipment came to normal. After several years of continuous practice, under the guidance of relevant experts and peers, we have gradually mastered the process technology in this regard and formed a set of effective operating experience. Over the past few years, the product quality has been stable, consumption has decreased, customers are satisfied, and the enterprise has also achieved good economic benefits. Flexographic printing, like other printing methods, is to get prints with smooth ink, rich layers and bright colors. However, the flexographic printing process belongs to light pressure printing, and the key is that the conditions of the printing machine, such as the embossing structure, printing roller, plate material, wrinkle roller, double-sided adhesive, ink, etc., should be strictly matched with the rubber film pasted on the reverse side of group B for testing and matching. However, it is difficult to adjust the many variable parameters between them to the best point. Through years of exploration and practice, we have the following experience

1. Process practice from manuscript to printing qualified products

at the beginning of 1998, we successively printed Dayang brand, gold card and cigarette bag of Guizhou Chiyu group. The printing samples we get are the samples of lithography. It is difficult to realize the faithful reproduction of the printing samples and originals, and to adapt to the process characteristics of flexographic printing. Among them, the original of Dayang cigarette bag is the hollow out small characters in the red solid zone and the dot sailboat pattern. In practice, we realize that due to the different lithography and flexographic printing processes, dots, words and lines of the same color cannot be made on the same color plate with the field, because the ink volume required by the dot and the field is different. If you make it on the same printing plate, after the quantitative ink transfer of the corrugated roller, you can't meet the ink volume required on the spot, otherwise, a paste plate is formed. Therefore, we make points of the same hue separately from the field. The large-area pattern of the two color plates is the same. The genuine version is equipped with a dotted sailboat pattern, equipped with a 500 line roller. Remove the dotted sailboat pattern on the sub version, enlarge the edge of the hollowed out small characters by 0.1mm, and equipped with a 360 line roller, which not only avoids the broken pen of the hollowed out small characters paste version, but also achieves a full and bright effect on the ground

due to various reasons, the products cannot be processed on the flexographic machine at one time. We have made ladder shaped information lines on the horizontal and vertical direction of the main color plate of each batch of products as the cutting standard, so as to ensure that the transverse part is accurately controlled in the production process, and create necessary conditions for the smooth operation of bronzing, embossing and die-cutting in the next process

there are many high-end and fine products in cigarette pack printing, which are difficult to print and require high quality consistency between batches. The difficulty in flexo printing production is that the error of overprint accuracy is large, which affects the accuracy of post process bronzing, embossing and die cutting. The printing method of round pressing will cause cumulative errors due to continuous rolling, coupled with machine vibration, personnel operation differences, raw material quality and other factors, the accuracy of overprint cannot remain unchanged. These situations must be well known, timely adjusted, summarized experience, and put forward feasible solutions

2. Selection and rational use of materials

(1) corrugation roller

corrugation roller is an important part of flexo printing machine. It can be used in reasonable cooperation with the doctor blade to transfer water-based ink accurately, quantitatively, evenly and stably. In order to ensure the quality of printing products, our company has configured more than 60 200 ~ 800 linear rollers in total, which creates a wide space for selection according to the matching requirements of printing plate patterns. In actual operation, the same line of wrinkle counting rollers must be compared, selected and numbered when necessary, and their use conditions must be recorded in detail. They must be cleaned before and after being put on the machine. This can not only stabilize the print quality, but also protect the wrinkle roller

(2) selection of water-based inks

at present, the brand, quality and price of flexo printing water-based inks vary, and the application range of substrate materials is also very wide. We must pay attention to how to match them. We have experience and lessons in this regard. In 1998, when we undertook the printing of Guizhou Huangguoshu group Jinxiong trump card, gold card and cigarette bag, we did not consider that the gold card paper was non absorbent paper, which might affect the inking volume, resulting in deinking, pasting and other failures. Later, we chose hualiqi, AkzoNobel, Tiens and other brands of inks for trial, and the experience we gained is:

● understand the adaptability between a batch of key technical inks and printing materials with great efforts under oil, and get the best effect after matching the two, then we choose the object

● pay attention to stabilizing the viscosity and pH value of water-based ink at any time during the printing process, control the dosage of additives, and adjust timely according to the drying performance

● a specially assigned person shall be responsible for the allocation of ink, and the above ink use conditions shall be recorded to maintain the good adaptability of ink use

3. Precautions for actual operation

actual operation is the most specific production process of carefully implementing process and technical standards. In addition to the original operating procedures and post system, our factory has also summarized our experience

(1) pre press equipment inspection and plate loading

before printing, all transmission parts must be lubricated, and all fastening parts must be locked. Carefully check the printing plate and paste it carefully. The two lenses on the plate loader must be in the same horizontal position, and the angle positions of the left and right cross gauges on the fluorescent screen must be consistent. Pay special attention to the flatness between double-sided tape, plate roller and printing plate to avoid bubbles, which will affect the flatness of pressure. Generally, we install a set of printing plates by one person, because when two people install a set of plates at the same time, the force above is to share with you the operation process of the tensile testing machine and the introduction of sensor classification. Different sizes will lead to different installation effects, thus affecting the accuracy of overprint

(2) pressure adjustment and tension control

in order to ensure the accuracy of overprint, it is important to adjust the pressure of the machine. For this reason, we have taken measures to number the plate shaft and plate seat bearing and use them together with the printing unit. In addition, try not to use a larger version roll, so as to avoid the blotting caused by too large diameter, which will affect the overprint and reducibility of prints

flexographic printing is light pressure printing, and its process determines the importance of pressure regulation in practical operation. Because the printing plate is elastic, the key to achieve accurate positioning is to adjust the pressure between the wrinkle roller, plate roller and impression roller. In order to understand this problem, we made information strips composed of two different density points on both sides of the printing plate. By observing the changes of the information strips, we can judge whether the pressure is uniform and suitable. At the same time, we should pay attention to the impact of the machine speed changes and machine vibration on the pressure during the operation of the equipment, and make immediate adjustment

tension control of paper. The web must maintain a certain tension during the printing process. The control value of tension should be adjusted according to the thickness and width of the printing material. After the printing speed of the same roll of paper is normal, the tension should be consistent, and the tension on both sides of the roll should also be consistent. In this way, achievements can be accumulated to avoid ink scratching, overprint inaccuracy and other situations

(3) after a print is completed, the wrinkle roller and the printing plate should be cleaned in time, the remaining water-based ink should be sealed and stored, the ink on the plate shaft seat should be wiped off, the engine oil should be applied, and the lubricating oil should be applied on the transmission parts to keep the equipment and environment clean