With the continuous development of the flexible packaging industry, many products are undergoing packaging reforms, forming diversified, multi-functional, multi-color, unique and unique packaging. From color printing to forming, although there are many processes, but to get a beautiful package, the first process must be first: color printing is perfect, the colors are dazzling, the patterns are clear, the layers are clear, and the three-dimensionality is strong. , To achieve the ideal packaging.
Many manufacturers have just entered the plastic printing industry. Due to the poor foundation and low level, color printing cannot be effectively controlled. There are also many manufacturers to add high-end equipment in order to improve the grade. Although the equipment grade has been improved, the grade of printing quality has not been improved. This is a common problem in the plastic color printing industry. Based on years of experience, the author has compiled a "plastic gravure printing recipe" for plastic gravure printing, which will be mastered, understood, and used by printing workers.
Plastic and gravure printing recipes, the inside and outside of the table printing determines the temperature and humidity dryness is very important, the balance of the plate roller, carefully find the scraper angle, master the ink viscosity, adjust the pressure of the rubber roller at any time, keep in mind the printing speed oven, and ignore the tension. Printing determines whether the printing should be surface printing or inside printing before printing. Whether the materials used are surface printing or inside printing. Namely: film, plate roller, ink. The key is ink. Because inks are the most distinguishable, various types of inks require various types of thinners. If the wrong thinner is used, it will cause adverse consequences or economic losses. There are many types of inks, including benzene-soluble, alcohol-soluble and other special ones. Choose the ink and thinner you need according to the determined print sample; the film should also determine what kind of film, BOPP, PET, PA, PE, PVC, etc. In the plate making process, the plate making manufacturer determines the plate making and plate making tension according to the requirements. Therefore, it is very important to determine whether it is surface printing or internal printing before printing.
Second, temperature, wetness and dryness are very important. In plastic gravure, many manufacturers do not pay much attention to the temperature and wetness of the workshop, failing to take effective measures in time, and many problems have arisen, neglecting the requirements of the printing workshop temperature and humidity. If the temperature in the printing workshop is too high and the humidity is too high, it will be easy to appear sticking back, fading, color transfer, blocking, poor firmness, and will also cause ink decomposition, printing and other printing quality problems. If it is too dry and the machine speed is fast, static electricity will be generated, causing the ink to move upstream of the film; if the machine speed is slow, the printed matter will be dull, dry, and blocked. Generally, the workshop temperature should be controlled at 18 ℃ -25 ℃, and the dry humidity should be between 55% -75%, especially for high-end cooking packaging and medical packaging, the environmental requirements are more stringent. A little carelessness will cause serious losses to the enterprise.
Third, the balance of the plate roller is carefully found. Generally speaking, the balance of the printing plate roller is determined by the printing machinery and the plate making roller. But when installing the plate roller, we must set the position of each color and the balance of both sides to achieve the best balance. The positioning of the plate roller should be determined according to the registration line on the plate roller and the length of the plate roller. The plate roller without key groove must be tightened. Be careful when installing the plate roller. Damage, causing unnecessary trouble and loss.
4. Scraper Angle Mastering the squeegee blade plays a very important role in the entire gravure printing machine. It has to scrape off the excess ink on the plate roller. Therefore, when installing the squeegee, you must master the balance and adjust the squeegee and plate. The angle of the roll. Generally speaking, the angle between the doctor blade and the plate roller is between 45 ° -65 °, and it should be further adjusted according to the depth of the mesh of the plate and the machine speed. When adjusting, the distance between the scraper and the pressure roller should be matched with the machine speed. At the same time, it is necessary to give appropriate pressure to make the doctor blade penetrate the ink layer and contact with the plate roller to play the role of doctor ink. The size of the pressure of the doctor blade can be adjusted according to the graphic depth of the printing plate hole and the order of overprinting. It is also necessary to prevent the appearance of wire filaments. Generally speaking, hard blades have more wire filaments than soft blades. The hardness of the blade should be determined according to the hardness of the plate roller.
5. The viscosity of the ink can be adjusted at any time during the printing process. The ink needs to add thinner to achieve the required working viscosity. One is to adjust the ink viscosity and drying speed according to the printing speed. If the machine speed is high, the fast-drying thinner should be selected. If the machine speed is slow, the slow-drying thinner should be selected. The second is that in the normal printing process, the thinner needs to be added again due to the volatilization of the thinner. When the thinner is added, it is best to mix it with the ink and add it to the ink fountain, so as to ensure the consistency of the printed matter and reduce the waste rate. Because the viscosity of the ink is high, the relative color density is high, whereas the viscosity of the ink is low, and the relative color density is low. This shows that the change in ink viscosity can directly affect the color of the printed product. Therefore, the work of adjusting the viscosity of the ink is very important.
6. The pressure of the rubber roller should be kept in mind, which is also a key part of the printing quality. The quality of the rubber roller is poor, and it is difficult to print a good product. If the imprinting rubber roller is not flat, there will be missed printing and uneven coloring. Excessive pressure of the embossed rubber roller will cause the ghost image (double eyelid) of the printed material pattern to be unclear and dull. If the pressure is too low, the shallow screen of the printed matter will not be colored, and the text will not be clear. The softness and hardness of the rubber roller should also be determined according to the thickness of the printed film and the depth of the plate roller. Generally speaking, the requirements for the pressure of the rubber roller are that small characters can be printed clearly or light screens can be colored. High-end printers with pressure gauges should be controlled between 2-3.
7. The printing speed oven is matched with the drying system to determine the printing speed of the gravure printing machine. From low-end to high-end printing presses, their drying systems are different devices. From single oven to double oven and multi-function oven, drying tunnel. The main purpose is to increase the speed of the printing machine, and secondly to dry the printed material thoroughly, improve the firmness of the ink on the film and allow the thinner in the ink to dry completely. Prevent false stemming. Causes the phenomenon of back sticking or odor after bag making. Therefore, the drying system should be well coordinated with the speed of the printing machine, and then the oven temperature and air volume should be fully adjusted according to the pattern area of ​​the substrate. The temperature of the oven must be determined according to the material of the substrate. Such as: printing OPP film and printing PET film, the temperature of the oven is different.
8. Ignore the performance of the tension register gravure printing machine, the key is tension. The tension is automatically and manually adjusted by the tension control roller. In order to facilitate printing and increase the speed of the printing machine, the manufacturer has installed magnetic powder tension on the upper film and the lower film to automatically control. Some high-end printing machines have installed computer tracking and automatic control systems in various colors to control the tension for various color sets. The tension of each color of the computer register printing machine must be adjusted manually. The adjustment can be carried out according to the speed of the machine and the size of the tension, so that the color registration is accurate and satisfactory prints are obtained. It can be seen that the key to the accuracy of color registration is the control of tension, which should be strictly controlled.
In summary, in order to print a good product, it is necessary to master the above eight elements so that each link can not be ignored, and the above elements should be mastered according to the performance of its own printing press.
Yantai Meixin Ink Co., Ltd. Sun Shutong Address: Shandong Longkou High-tech Industrial Park Postcode: 265718
Phone 13905458576
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