Necessary knowledge points for intaglio printing process control

Gravure plate making is more complicated than paper gravure plate making, and there are many influencing factors. Designers and producers should have certain color knowledge, understand the printing process, and grasp the characteristics of plate making to design high-quality product packaging quickly and well.

Plate making requirements for different types of packaging bags

Plastic packaging bags can be divided into four categories according to the bag making method: three side sealing, middle bottom sealing, three-dimensional middle sealing and sheet material.

The three side seal is used to seal around the packaging bag. The front and back dimensions are both finished product dimensions, with a certain sense of integrity. The design is unrestricted, and the front and back designs have a certain degree of continuity. Since the front and back are the same size, the front can be designed first to make the back echo the front. When making a plate, the front and back should be arranged on the same set of plate rollers.

The middle bottom seal is sealed on the back. The front dimension is the size of the finished product. The back is divided into two equal parts, and the sum of their widths is equal to the width of the front. Generally, the front and back are unfolded for integrated design, and 25px edge sealing is added on the left and right respectively. The front and back are also on the same set of cylinder.

The three-dimensional middle seal is based on the middle bottom seal, and three-dimensional edges are added on both sides. The front, back and side are also on the same cylinder.

Due to the limitation of printing materials, the front and back sides of sheet materials must be designed separately to make plates separately. They cannot appear on the same set of plates at the same time.

The Key Points of Color Treatment for Line and Mesh Toner

● Line version

A considerable part of gravure printing is line printing. Line printing is composed of lines and field color blocks. It wins by modeling and creates visual impact by field (special color) to highlight the advantages of line printing. According to the characteristics of gravure printing machine, the printing plate is generally no more than 6 colors, and the spot color shall be used as far as possible, and the color code shall be provided to facilitate color matching during printing.

A set of line version can form a series of products with a variety of different combinations. When designing, you can first design a color matching scheme for users to choose. As the line version does not have a sense of hierarchy, attention should be paid to color overlapping between colors to meet the overprint requirements caused by the expansion and contraction of the substrate.

● Mesh adjustment

Mesh tone plate has extremely rich layers and ever-changing colors, but no matter how complex the layers are, they are composed of cyan, magenta, yellow and black (special cases need to add spot colors). The level of the image is divided into highlights, dark tones and middle tones.

Therefore, first of all, it is necessary to know the gray balance data of four-color ink and the printability of each level segment, master the dot change rule, and summarize the image level processing method to make the product achieve the best visual effect.

1. Adjustment of ash balance

2. Step adjustment value setting of highlight and bright area

For the highlight part, first, adjust the three primary colors of the extreme highlight to 0, as the brightest part of the image step adjustment. If necessary, increase the range of the highlight part; The second is to adjust the highlight white area of the required level to the minimum printable level value, which is determined according to multiple tests and proofing. The minimum dot values are C6%, M5% and Y5%.

3. Intermediate mediation level processing

The middle tone is the most important part of the whole image. The middle tone level should achieve the best visual brightness. To this end, the overall saturation can be deepened or the saturation can be reduced according to the situation, but try not to affect the gray balance of the image, and only make local adjustments to the image. For example, for a plate of bright colored fruits, the main colors of different fruits can be grasped during processing, and the green leaves can be appropriately reduced to red, red fruits can be appropriately added to red, and yellow fruits can be reduced to blue and red. However, after locking the local part, the micro adjustment of the level and color shall be carried out to make the product color cleaner, smoother and more pleasing to the eye.

4. Dim level processing

In general, the level restoration of gravure printing to more than 80% dot area is very poor. In this way, it is necessary to open up the level of the deepest part and the secondary part of the dark tone, and reduce the level of the secondary part to about 60%.

Overprinting between color plates

Because plastic film materials are more flexible than paper, the overprint processing between color plates must be considered in the front end production of gravure printing. The standards for overprint processing are as follows:

1. The text version is usually black, and hollowing is not allowed when overprinting. If the text plate is in other colors, such as magenta, consider whether to overprint with the background according to the size of the characters. When the word is less than 12 points, it must be overprinted with the background color, but it is still necessary to consider whether the color of the superimposed text is eye-catching. If the identification effect is affected, change the color.

2. When the light color is connected with the dark color, the edge extension value of the light color is generally set to 1~2PIXS. The value can be increased appropriately for larger layouts.

3. When the spot color plate is connected with the picture, the edge of the spot color plate can be expanded without affecting the edge pixels of the picture. The edge expansion value is usually 1~2 PIXS.

4. If printing opaque ink, such as gold ink, first consider the printing sequence of the ink, otherwise the gold ink will cover the relevant color. If you have to overprint, you should also consider the problem that gold ink and other color ink will become dark and not bright when overprinting.

5. Silver ink is also a special ink, light silver has a certain transparency. Therefore, when silver ink is used, it must be determined by design whether it is overprinted or hollowed out with the background color or related colors according to customer requirements.