Gravure front-end production

From the wide variety of styles and colorful packaging, we can find that nowadays commodity packaging has not only pursued practicality and commerciality, but also its artistic quality can not be ignored. As the mainstream technology of packaging and printing, gravure printing, especially gravure printing plates, should also enhance communication and develop simultaneously with packaging. This article will only share some of the lessons I have learned in the prepress production of gravure plates, share them with peers and learn from them.

Plastic bag classification

There are many kinds of plastic bags and their specifications are uncertain. Therefore, the design and production staff often overlook the bag-making method. As a result, although the design drafts are exquisite, the resulting finished product packaging is unsatisfactory and even becomes a waste product. Experience tells us that only by understanding the types of commonly-used packaging products can we make full use of design ideas, eliminate design items that do not meet the bag making process, and design a practical and perfect finished product package.

Plastic bags can be divided into three sides seals, middle bottom seals, three-dimensional seals and sheet materials according to bagging methods.

The three side seals are sealed around the packaging bag. The front and back dimensions are all finished dimensions. It has a certain overall sense, and the design is not restricted, and the front and rear designs have a certain degree of consistency. Because the front and back dimensions are the same, the front can be designed to allow the back and front to echo. At the time of plate making, they are arranged on the same platen roller.

The bottom seal is sealed on the back, the front size is the finished product size, the back is divided into two equal parts, and the sum of its width is equal to the width of the front surface. Usually, the front and back sides are unfolded during design, and the integrated design is implemented. Each plus 1cm edge, front and back are also on the same platen roller.

The three-dimensional seal is based on the mid-bottom seal, plus three-dimensional sides on both sides, the front and back sides are also on the same platen roller.

Due to the limitation of the printing material, the sheet material must be designed separately on the front and back sides, separately from the plate making, and cannot be on the same plate cylinder at the same time.

Color design basis and color specification

Because plastic printing and paper printing are different, if you want to print bright and colorful packaging, you need to understand the color characteristics of plastic printing when designing colors on the front end. First of all, we must look at the process sheet, understand the customer's intentions and their requirements for color, and specify the printing requirements for the post-process.

(1) Substrates

Understand whether the substrate is a film, PA nylon film or heat sealing film, set the appropriate tone value, it should be noted that the color and the level of reduction in India is better than the table printing.

(2) Ink characteristics

The printing ink sequence in the ink is first deep and shallow, and the surface ink is shallow and deep. To master the performance of various inks, specify the color shift characteristics of various inks. Usually, the magenta ink has good color rendering; the blue ink has magenta; the yellow ink has good brightness, but it is easy to paste, and the tone value is usually reduced by 5% to 8%.

Color processing points

Line version

A considerable part of the gravure printing is line printing. The line version is composed of lines and solid color blocks. It wins with the shape and creates visual impact with the spot (special spot color) to highlight the advantages of the line version. Plates according to the characteristics of the gravure printing machine, generally not more than 6 colors, and try to use spot colors, and with color marking, in order to print when the color.

A set of line version can be used to form a series of products with different combinations. When designing, a color matching scheme can be designed for users to choose. Because the line version does not have a sense of layering, color-to-color should pay attention to overlap color processing, in order to meet the registration requirements caused by the substrate expansion and contraction.

2. Mesh revision

There are extremely rich levels and ever-changing colors, but no matter how complicated the level is, it consists of four colors: cyan, magenta, yellow, and black (special circumstances need to increase the spot color). Highlights, shadows, and midtones.

Therefore, we must first know the gray balance data of four-color inks and the printability of each level segment, grasp the rule of dot change, summarize the image layer processing method, and make the product visually achieve the best results.

(1) Adjustment of gray balance

(2) High tone and highlight tone adjustment

For the highlight part, the first step is to adjust the highlights of the three primary colors to 0, as the brightest part of the image tone, if necessary, can increase the scope of the highlight part; second is to adjust the height of the white area of ​​the required level to the smallest printable tone The value is determined based on multiple tests and the minimum dot value is C6%, M5%, and Y5%.

(3) Intermediate tone processing

Midtones are the most important thing in the entire image. The level of intermediate tone should achieve the best visual brightness, for which it can deepen the overall saturation or reduce the saturation according to the situation, but try not to affect the gray balance of the image, and only make partial adjustments to the image. Such as a plate of bright color of fruit, can handle the main colors of different fruits, the appropriate reduction of red leaves, red fruits appropriate red, yellow fruits, reduce blue, reduce red. However, after the partial locking, minor adjustments in levels and colors will be carried out to make the product more clean, smooth, and pleasing to the eye.

(4) Shadow Level Processing

In general, gravure is poorly restored to 80% of the Internet site area. In this way, the levels of the darkest part and the deepest part of the dark tone need to be opened, and the level of the second deep part should be reduced to about 60%.

Overprinting between color plates

Since the plastic film material is more flexible than paper, the overprint processing between the stencils is a link that must be considered in the production of the gravure front end. The standard for overprint processing is as follows.

(1) The text version is usually black, and it is not allowed to hollow when doing superimposition. If the text version is other colors, such as magenta, depending on the size of the word, it can be considered whether or not to overprint with the background color. When the word is less than 12 pounds, it must be overprinted with the background color, but it is still necessary to consider whether the color of the superimposed text is noticeable. If the effect of recognition is affected, color change may be considered.

(2) When light and dark colors are connected, the light-colored flanging value is generally set to 1 to 2 PIXS. Larger layout can increase the value properly.

(3) When the spot color version and the picture are connected, the spot color version can be expanded without affecting the picture edge pixels, and the value of the extended edge is usually 1 to 2 PIXS.

(4) If printing opaque inks, such as gold inks, first consider the printing order of the inks, otherwise the gold ink will cover the relevant colors. If you have to do overprinting, you should also consider the problem of darkening and not bright when gold and other inks are overprinted.

(5) Silver ink is also a special ink, light silver has a certain degree of transparency. Therefore, the use of silver ink must be determined by the design according to customer requirements and the underlying color or related colors are overprinted or hollowed out.

Conclusion

Plastic gravure platemaking is more cumbersome than paper gravure platemaking, and there are many influencing factors. The design and production personnel should have a certain amount of color knowledge, understand the printing process, and grasp the characteristics of platemaking to be able to design high-quality product packaging quickly and well.