Flexographic printing, an emerging printing process, has been developing rapidly and steadily in many printing factories and achieved good economic benefits through the unremitting efforts of people of insight in the printing industry in China for several years. In terms of product packaging, high-quality flexo products can be seen everywhere, and they often awesome printing experts. There are indeed many excellent prints: cigarette packets, beer labels, etc .; stickers are more, and a lot of them are drugs that enter China's famous joint ventures. , Food, daily chemical products, industrial products labels, shopping mall lottery, etc .; there are also wine box, medicine box, hamburger box, bowl noodle seal, toothpaste tube, battery label and other packaging; more food, women and children, daily chemical BOPP , PET, PVC film and other flexible packaging, and corrugated boxes. At the 4th Shanghai International Flexogravure Printing Technology and Equipment Exhibition in June this year, there will be more exquisite flexo products displayed. We can confidently believe that the quality of our flexographic printing is comparable to that of lithographic printing and gravure printing. The situation has been formed, and the market development space is very broad. Few people now doubt the feasibility of flexographic printing, and give its full affirmation of its advantages. A considerable number of printing companies, especially packaging color printing companies, have included flexographic printing in the company's development direction as the company's new economic growth point.
The main reason for the normal development of flexographic printing is that its related equipment, materials, and technology are becoming more mature in technology, and the localization of supporting equipment is becoming more and more perfect. Application. Because flexographic printing is a new technology, it must be mastered by humans, and the technical quality of enterprise personnel plays a particularly important role in flexographic printing. The technical qualities are embodied in the proficiency of equipment operation, the reasonable selection of materials, the correct formulation of processes, and the orderly production management. As long as the configuration of the equipment, the performance of the materials, and the key points of the process technology are effectively implemented in the print production process, qualified products can be produced, the quality can be recognized by users, and the business market of the enterprise can be expanded. The economic benefits of flexographic printing can also be guaranteed.
However, there are still some printing manufacturers that have introduced flexo printing equipment. Due to the lack of certain technical support, the equipment is difficult to operate normally, the product quality cannot be guaranteed, and the economic benefits cannot be discussed. The reason for analysis is actually obvious: there is a certain gap between the overall technical quality of such printing manufacturers in flexo printing and the actual production needs. The effective use of equipment configuration, the correct selection of flexo materials, the reasonable formulation of printing processes, and operation The operation level of personnel, etc., have not yet reached the basic level of normal production, thus affecting the normal production of flexographic printing. This is a stage that many manufacturers engaged in flexographic printing have experienced. Facts have proved that if such printing companies can be targeted to provide effective technical support to help solve some weak points, the level of flexographic printing of these companies will soon be improved, and the economic benefits will rise significantly.
So, how to make flexographic printing develop healthily in China! We believe that improvement in process technology is the key. In response to this problem, the main points of manuscript, process and technology in flexographic printing are now presented, and some brief introductions will be made in conjunction with the actual production. I believe that it will be helpful to colleagues who are engaged in flexographic printing or will be engaged in flexographic printing. In order to make printing manufacturers take less or no detours in the development of flexographic printing, this is the purpose of this article.
1. Printed manuscript
Printed manuscripts are the basis and basis of printing plate making. The patterns, texts, and colors on the printed manuscript need to be conceived and designed according to the sales characteristics of the product, and then be plated and printed to reflect the practical effect of the product packaging.
1. Feasibility
Whether it is a user's manuscript, a design company's manuscript, or a manuscript, the printing manufacturer must put forward the requirements of the manuscript to the designer: in the design process, you must fully understand the characteristics of flexographic printing; you must fully consider the manuscript delivery plate making, printing The feasibility of the process operation. The so-called feasibility: the designer's choice of patterns, text, and colors in the manuscript must first meet the production requirements of flexographic plate making and printing; second, it must be suitable for the actual level of equipment, materials, and operations of the printing manufacturer; The specific practical standards of packaging are the only way to ensure that the original manuscript design and the printing of flexo products meet the ideal quality standards.
It needs to be pointed out that most of the current printed manuscripts are designed by computer. In order to obtain the brilliant visual effect of the manuscript, more color pictures are often used, and the functions of color printing, gradation, puzzle, and deformation are added, especially Like a rainbow pattern. If we choose the lithographic printing method, such printed manuscripts rarely have plate-making and printing problems. When choosing the flexographic printing method, you need to discuss with the designer the feasibility of the color plate or rainbow effect in the plate making and printing process.
2. Choose less color photos
Flexographic printing is not yet able to reproduce the colorful tones of color photos as patterns as well as lithographic printing. If you copy an exquisite artistic picture, such as a calendar, picture book, sample, etc., that is not the specialty of flexographic printing. Although various very delicate flexographic printing samples have appeared, they are only at the stage of proof printing, and there is still a large gap compared with lithographic printing in actual production. Color pictures and color inkjet printing are made by gradation screen printing through color separation and plate making, and 3 to 4 colors with halftone changes. Because flexographic printing is letterpress printing, when using screen gradation printing, the highlight part is difficult to reproduce, while the dark tone part does not change significantly, so it is difficult to reflect the natural color transition and rich layering. Moreover, flexographic printing is most forbidden to "de-screen" (dot percentage is less than 1%). Manuscript designers should be asked to avoid excessive highlights as much as possible. In the transition of the hierarchical network, the highlights of the transition of the dots should be as much as possible, and it should be directed to the "extension of the design draft (bleeding area), that is, to prevent the level from changing. In the design manuscript, if the highlight part is really needed in the manuscript, the designer should be persuaded: according to the current plate quality and plate-making technology, the plate maker should be allowed to retain 1% to 2% of the dots in the highlight part to obtain The effect is close to highlights. Which color dots to keep depends on the main color of the manuscript.
3. Multipurpose spot colors
We have to tell designers that we should consider using spot colors as much as possible when conceiving artwork. In the design of packaging and decoration, spot color has a unique decorative effect. For packaging products, it is a product logo, brand logo, purchase logo, and has a strong advertising effect. Reasonable and clever use of spot colors can add a finishing touch to the decoration design. Whether it is lithography, gravure printing, spot color printing is still quite a lot of choices. Printing spot color is the strength of flexographic printing, its color saturation is far superior to lithographic printing, and no less inferior to gravure printing, which is an important factor that flexographic printing is widely accepted in packaging products.
4. Non-printed originals
It must be pointed out that there are a considerable number of printing factories. The "printed manuscript" he obtained is a real sample of printed matter, with lithographic or gravure printed real samples. Using this real sample as a printed manuscript for flexographic plate-making companies to make plates is really "difficult" for them. For such "manuscripts", it is necessary to go through the hands of the designer and the computer to "copy" a printed manuscript before it can be used for plate making and printing. How to make this manuscript exactly the same as the original print, but also to meet the flexographic printing process, this is a more troublesome job. In this regard, the printing manufacturer should carefully analyze the printing process of the actual sample of the printed matter. According to the points on the printed manuscript mentioned above and the process points that will be discussed below, discuss with the technical staff of the plate-making company to complete the plate-making. From the perspective of process technology, we do not advocate the use of such printed "manuscripts".
5. Establishment of craftsmen
It is recommended that the printing factory establish a craftsman, and it is very necessary for the craftsman to control the quality of the printed manuscript. Because the craftsman knows the company's product requirements, equipment status, process characteristics, raw material characteristics, staff technical level, post-press processing and user requirements, etc. Technicians can combine the company's situation to make printed manuscripts meet production quality standards in plate making and printing. The work of a craftsman cannot be replaced by others.
Second, the main points of the process
After the printed manuscript is determined, the craftsman will develop the color separation process of the printing plate according to the characteristics of the printing process of the factory, and provide reference for the plate-making company, so as to ensure the production quality of the flexographic products. Professional plate-making companies generally accept the printed manuscripts, and if the printing manufacturer does not put forward technical requirements, it will separate the plates according to the usual process. Due to the different understanding of the printed manuscripts, the familiarity with the flexo process, and the degree of understanding of the actual use, it will cause a large unrealistic situation between the printing plate production and the printing production, and Things that cause repeated revisions or re-productions often happen, which results in a waste of materials and time. Therefore, it is up to the craftsman to formulate the color separation process and hand it to the plate-making company for plate-making. If you do n’t understand, you can communicate and discuss with each other to ensure a successful plate-making process, which is beneficial to both parties.
Technicians need to pay attention to several points in the process of formulating the process:
1. The four-color screen version, text lines, and full-field version should be distinguished.
Technicians need to know the production principle of the four-color color separation version, and also need to know the lines of other text and the color separation requirements of the full version on the ground. It is not like lithographic printing or gravure printing. Four-color screen lines and text lines of the same color cannot be made on the same color printing plate as the field. Of course, dots cannot be made on the same color printing plate as the field. This is because the amount of ink required for the text lines and the field is different. If it is done on the same printing plate, after the quantitative ink is transferred by the anilox roller, the ink volume (small amount) needs of the dots and text lines cannot be met. Demand for large amounts of ink on the ground. In turn, to meet the needs of the field, the lines of the text must be paste. Therefore, on the same color plate, the text lines and the ground should be divided into two plates. Small text, thin lines, large text, and thick lines should also be divided into two plates. That is to say, the color group configuration of the flexographic printing machine is better than that of other printing. There are many reasons. Of course, it is also necessary to provide color separation opinions on the chromatic fonts used in the design of printed manuscripts, hook lines, adjacent colors, spot colors, post-press processing such as hot anodized aluminum, and indentation.
2. If the color separation can use spot colors, use spot colors as much as possible.
If, like lithography, spot colors are often overprinted with four-color dots, it will cause great trouble to flexo platemaking and printing, which we do not advocate. Even for lithographic printing, spot color printing is not rare in packaging printing. The use of spot color printing for flexo plates is its main feature. For some products with special eye-catching requirements, special colors can also be used for overprinting. The spot color of flexographic printing is obviously different from the lithographic printing in the vividness and saturation of the color, and the gravure printing method is superior. We must make full use of the remarkable feature of flexographic printing.
3. Special eye-catching spot colors can also be used for color stacking.
For flexographic printing spot colors, generally one color can meet its color requirements. For some special color products that require special eye-catching, you can also use special color overprinting. Separation pieces of two stacked color plates should be separately produced. The superimposed parts of the large-area graphics of the two superimposed versions are the same, and there are some differences in some parts, such as large text, empty graphics, and solid blocks that bring small text and lines. One of them should consider enlarging the first line or reducing the first line: about 0.05 to 0.1mm, and there are also those that enlarge or reduce the second line, about 0.10 to 0.2mm. At the same time, it is necessary to consider that in the color selection, there must be one main color of the overprint color version and another sub-color of the overprint color version. Such a color arrangement is very necessary. You can consider choosing text, lines, dots, etc. that need a small amount of ink to be brought into the picture from one of the two overlapping color plates. As the picture and text were brought into one of the multi-color printing plates, the purpose of multi-coloring was achieved, and the text, lines, or screen printing plates were also advanced. In fact, the number of colors in the printing plate was not increased.
4. The size of the imposition depends on the product structure.
Technicians must arrange the size of the printing plate according to the size of the finished product, and they must consider both the vertical and horizontal dimensions. The longitudinal direction determines the circumference of the plate cylinder, and the transverse direction determines the width of the printing format. Flexographic printing is converted from the repeated perimeter of the imposition of the printed matter to the perimeter of the plate cylinder, which is customarily converted into the number of teeth of the plate roller. Regardless of the flexo printing machine produced in Europe and America, or the domestic flexo printing machine, the British CP gear system is now used for size calculation: 8 teeth per inch = 25.4 mm long, 1 tooth is 3.175 mm pitch arc length. Selecting the number of teeth of the plate roller is to determine the repeating circumference as an integer multiple of 3.175 mm. The determination of the size of the imposition is generally based on the intermediate value of the repetition circumference of the plate cylinder of about 80 to 100 teeth.
It is recommended that the craftsman should not make the repeated perimeter of the imposition of the printed matter bigger. Practice has proved that the larger the repetition perimeter, the larger the plate area, and the larger the plate cylinder. Large printing plate rollers make it inconvenient for the staff to operate; at the same time, the relative rotation speed of the large printing plate cylinder becomes slow during printing, and the water-based ink is easy to dry on the printing plate; large-area printing plates will also increase the cost of plate making. The product registration difficulty of the multi-panel imposition is not good.
5. Printing color sequence technicians should know that the color sequence of flexographic printing is basically the same as that of letterpress printing, but the color sequence method of lithographic printing must not be used. When determining the printing color sequence, the printed color of the four-color screen printing plate should be analyzed for the pattern color. The commonly used color sequence is yellow, magenta, cyan, and black. There are also color orders for yellow, black, magenta, and cyan. Because the water-based ink has high color density, strong coverage, thick ink layer, bright colors and low light transmittance. The color sequence of the four-color screen cannot be changed at will.
For spot color printing, the order of light to dark is generally used. Light ink is printed first, which can make dark ink superimposed and bright. For spot colors printed by the superimposed method, the color sequence of the primary color and secondary color is that the secondary color is printed first, and the primary color is printed later.
6. Printing
Flexographic printing usually adds a color water-based printing or UV printing at the end of the color sequence, which is completed by the printing unit. In addition to enhancing the gloss of the imprint, it is also to enhance the physical properties of the imprinted surface to meet the needs of post-press online processing and the practical requirements of commodity packaging, and has become an indispensable process.
There are two types of flexographic printing light, water-based varnish and UV varnish, which can be arbitrarily selected according to product needs.
Printing is divided into full version printing and partial printing.
â‘ The full plate printing is printed by a special printing roller (rubber roller, seamless printing plate).
â‘¡Partial printing needs to be made into a printing plate, glazing according to the required parts of the printing.
It is necessary to point out that many packaging prints must use partial printing to meet the requirements of post-print processing of products.
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