Application of soft gravure printing technology in

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The application of flexible gravure printing technology in plastic upholstery printing (Part 2)

the printing mechanism is different

in flexographic printing, the ink is transferred to the printing plate through the embossing roller and then to the printing substrate, while gravure printing is directly inked by the plate cylinder and then transferred to the printing substrate. Therefore, the inking amount of flexo printing is determined by the roller, while the inking amount of gravure printing is determined by the printing plate

due to the limitation of processing technology, the number of lines of the embossing roller cannot reach a particularly high level at present, so the dot of flexographic printing is too large and the line is slightly thick, which is not comparable with gravure printing. At the same time, because the hole depth and density of each part of the embossing roller are the same, for the dark hanging plate, the field part and the hanging part must be separated, otherwise it can only be the field is not solid, the color is light, or the hanging part often has dirty spots, and the printing effect of the field part and the hanging part cannot be taken into account

gravure printing has relatively few restrictions in this regard, but for a large area of small percentage of dark hanging plates, the field part and hanging part should also be separated, otherwise the hanging part is prone to pitting, which is also difficult to control. Therefore, in plate making, compared with offset printing, whether flexo printing or gravure printing, there may be an increase in the number of printing plates. It is not simple to say that there are fewer gravure color plates, but flexo printing must increase the number of color plates. The number of color plates depends not only on the original image, but also on the requirements and acceptability of customers, as well as the technical level and equipment level of the printer

different degrees of difficulty in operation

the common faults of flexographic printing are relatively few. The main faults are white spots on the field, dirty spots on the line, and the probability of other faults is relatively small. Therefore, in general, flexo printing is a relatively economical printing process

gravure printing has more random faults, mainly including knife line ink dragging, blocking water marks, zebra marks, etc. the operation is more complex, so the scrap rate is relatively high

however, the gravure machine has a short ink path and strong manual operability, so the version change time is relatively short. Due to the need to install the plate before printing, and the need for mechanical hanging plate, coupled with the long ink path, the version change time is relatively long, but for large orders, because the probability of failure is greatly reduced, the time to complete the order is relatively short, and the yield is high

substrate is different

in plastic flexible packaging printing, there are many films that can be used as substrate

gravure printing machine can print PE, CPP, 0PP, pet, 0n and other films

flexo printing machine can print PE, CPP, 0PP and other films

it should be noted that for the tensile material PE, gravure printing can only print relatively thick materials with more low-pressure materials. Flexographic printing can be used to print materials of various thicknesses and proportions. This is mainly due to the different printing mechanisms of the two: the gravure adopts the unit printing method, which will lead to the inconsistent deformation rate of the printing material after passing through the drying oven and multiple guide rollers, resulting in overprint deviation: due to the satellite arrangement of the flexo press, there is only one embossing roller, and the deformation rate of the printing material on each color deck is consistent, so the overprint accuracy is high

when choosing to bear the decline in the overall cost of solar power generation, the packaging users with different No. 20 seamless steel pipe materials should not only examine the equipment and technical capabilities of the manufacturers, but also consider that the polyolefin substrate they choose plays a very important role in our daily life. Only when they choose the appropriate substrate can they obtain satisfactory prints

the contribution to environmental protection is different

flexo printing uses alcohol based inks, and gravure printing uses mostly benzene containing inks. Flexo printing has incomparable advantages in this regard. Although in recent years, gravure printing is also trying to use alcohol based inks, but the effect is not particularly ideal, and the inks suitable for printing on and pet must be benzene based inks, so it is unrealistic to completely transform gravure printing in a short time. In short, in the field of flexible packaging printing, gravure printing and flexographic printing have different markets. If you can make appropriate choices from them, it is not difficult to obtain satisfactory prints. The key is that packaging users should understand the respective characteristics of the two printing methods, and do not blindly pursue something that cannot be achieved, and do not mention requirements that exceed standards. Whether it is printers or packaging users, the ultimate goal is to pursue satisfactory packaging

comparison of advantages and disadvantages between gravure printing and flexographic printing

an important advantage of flexographic printing system is that the contact between the printing plate and the material belt is only in the protruding area, which allows the second color to be printed on it when the first color is half dry. It is not required that the ink between the two color groups must be completely dry, as in gravure printing machines. Flexographic printing allows a certain degree of "wet on wet" printing. The drying length can be as short as several centimeters, so the 8 ~ 10 color printing color deck can be distributed around a central drum that will develop in the direction of self-control production line. This large cylinder becomes the common impression cylinder of all printing color groups, thus ensuring the necessary rigidity of precision overprint and printing extensible film

in gravure printing, there must be a certain linear pressure on the engraving cylinder, and the material belt is tensioned mechanically. The ink must be completely dry before the material belt enters the next printing color deck. Each printing color deck must be completely dry operated. The length of the material strip of the color deck is large. From the perspective of energy saving, the cost of this process is high

this leads to an increase in the difficulty of protecting the accuracy of registration, which requires the installation of Opto electromechanical adjustment devices (registration control devices). Another problem involves the processing of printing plates. Gravure printing cylinder is expensive, but at the same time it is very strong. It can be used for long-term printing and can be reused without adjustment changes. On the other hand, the flexographic printing plate can be easily installed on or removed from the drum, and its size can be the same as the effective printing area. For small prints, small plates can be independent of the size of the drum. However, in gravure printing, the entire drum needs to be prepared in the width and circumferential direction (today's electromechanical system weakens this advantage: small printing surfaces require less engraving time). In the past, it was often seen that flexo never accurate the circumference value to the fourth decimal place. However, due to technological progress, significant progress has been made in obtaining infinitely variable repetition length. However, it is still not as significant as the progress of gravure printing

in flexographic printing, the contact pressure between the inking roller and the printing plate, and the contact pressure between the platen and the material belt must be the minimum. This means that this kind of equipment must operate very accurately, and the adjusting device must have a fine-tuning mechanism. The allowable eccentricity of the central large roller of a 6-color machine should be 8000 ~ 10000 parts of a millimeter. The thickness difference of the halftone printing plate must be less than 2/10 mm, which means that the jumping of 3 ~ 5 parts of a millimeter between the ink roller and the printing plate will damage the printing quality

in the past, people always believed that flexographic printing could never reach the level of satisfying the performance of small characters, such as Japanese and Chinese characters. However, with the adoption of ultra-fine detail and laser technology, flexographic printing has entered the market field that used to be considered as gravure printing. Due to the new design of printing machine manufacturers, gravure printing in the United States, Europe and parts of Southeast Asia has regained a large number of its territory. They have effectively changed the situation of the industry, making it have the following advantages over flexographic printing:

If an 8-color (central impression cylinder) Cl printer is used, it will take at least 1.5 hours to change the printing plate, color matching and re-enter the production situation, while an 8-color gravure printer only takes 30 minutes to complete the same work, including cleaning, adjustment, color matching and registration

Another major advantage of gravure printing is that it can handle 2.5 micron PE film, 5 micron aluminum foil and other light materials, up to 46 mils of plastic sol, light tin plate, thick aluminum foil and major industrial products. In addition, the lengthened dryer can be used for cold sealing and heat sealing, hot melt waxing, wire slitting, flat pressing and round pressing wire molding, wire cutting and indentation, wire compounding, etc

the comparison between the above gravure printing and flexographic printing systems can be summarized as follows:

1. Printing quality: gravure printing is better on the whole

2. control registration: flexographic printing is easier when the control device is not used

3. cost of printing plate: comparing the same printing area, the cost is equivalent

4. plate storage: it is easy to handle flexible plates, which can be removed from the plate cylinder and flattened for later reuse. The gravure cylinder requires a lot of space and expensive transportation and storage equipment

5. printing plate life: the service life of gravure metal drum is very long

6. inking: the size and depth of inking holes are variable, which undoubtedly provides a better means of halftone control for gravure printing

7. structure: gravure printing can use many kinds of solvents and resins, and the drum in contact with ink and bright oil will not be damaged, while the rubber and photosensitive resin will be damaged

8. repetition length: in flexographic printing, the repetition length is limited by the size of gear teeth

9. maximum printing color number: in flexographic printing, the maximum printing color number is 8 colors. In gravure printing, 10 to 12 color groups can be arranged. If enough space is reserved in advance, the color deck can be expanded even after installation

1o. drying: in flexographic printing, the drying system with simple structure sometimes limits the printing speed. In gravure printing, the size of the dryer of each color group can be determined according to speed, solvent solid content, etc

information source: export commodity packaging

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