One, gravure prepress design
1. Concept design
The packaging products designed by a good designer must be beautiful and elegant, and the patterns must be able to play a good role in emphasizing goods and propagating and promoting. The text should be simple and clear, and the ink must be coordinated so that people can feel bright at first glance. , read it as if immersive.
Since the designed packaging product is ultimately to be copied by the printing machine, the designer should consider the printing method, printing sequence, and the precision of the equipment before designing.
2. Problems that must be understood at design time
When designing a sheet gravure printing product, it is necessary to understand the properties of the gravure printing machine, the type of paper, the printability, the overprinting accuracy, the printing color sequence, and the reproducibility of the screen printing. (The intaglio printing machine has a limited effect on the reproduction of the screen edition.) In particular, the transitional points are easily lost in high-speed printing, and the stencil is more serious), as well as the characteristics of gravure printing. After being well-established, the designed product can be suitable for gravure printing to get a perfect reproduction.
Second, gravure prepress arrangement
1. Process review
For technologists, process reviews are extremely important. Regardless of newly-developed design products, or replica products, they should be carefully reviewed. Because it helps to open the way of thinking, preparing for the post-printing and guiding the production. The technologist must also understand the performance of the gravure printing equipment, master the urgency and urgency of the printing process, and even operate the technology, think of the customer's thoughts, hurry the customer's urgency, and orderly carry out gravure prepress technology arrangement.
2. Order arrangement
The gravure ink layer is thick. If the color sequence is not properly arranged, the ink to be printed will completely cover the previous printing ink. Therefore, in the gravure printing, the arrangement of the color sequence is particularly important. The arrangement of the color sequence should be based on the type of product, the printing effect to be obtained, the depth of the ink, the degree of hiding, and the type of ink used (pigment type, dye type, special ink).
The principle of determining the first color:
1 If the substrate is aluminum foil and the customer requires a high degree of color saturation, white should be the first color.
2 If the substrate is plain white cardboard, the background color should be the first color if there is no special requirement.
3 If the background color is dark ink and clear ink are overprinted, the dark ink should be in the first color (if the sheet is imitation metal paper).
4 If the text or pattern has a light color and trapping relationship with the background color, the light color should be used as the first color, and the dark background color should be printed later, and the text or pattern on the light-colored version should be larger than the required size 0.2. Mm, in the dark version, the words or patterns are hollowed out according to the required size to facilitate print registration.
3. Typesetting
According to the equipment's printing format, printing plate base processing drawings, refer to the sample size, reasonable layout (imposition). Generally take a tight fight, if deep processing bronzing, embossed lines, in the middle plus 5 ~ 6mm knife. Because of the long hot stamping or embossed lines, the quality of the long-line hot stamping, embossed and mat copper produced is not high. If the pressure of the stamping machine is uneven, the operator's pad (regulating pressure) is relatively time-consuming. It is longer.
Example of typesetting: The product is a clamshell cigarette pack. BOBST-820 gravure printing machine is used for on-line printing of large sheets. The cigarette factory adopts FK type packaging machine. The size of the single printing plate is 249mm x 98mm, and the imposition diagram is shown in Figure 1.
4. Platemaking requirements
According to the sample, layout, customer requirements, base processing drawings for plate making, production of gravure version of the specific process parameters requirements are as follows:
(1) Plate cylinder wall thickness is 12 ~ 15mm.
(2) The thickness of the copper plating layer is 1.2 to 1.5 mm.
(3) The hardness of the copper plating layer reaches HV190.
(4) The chromium layer hardness reaches HV950.
(5) The chromium layer surface finish reaches 8-10.
(6) The balance of the plate's dynamic balance can't exceed 0.3mm.
(7) The incremental diameter of the printing plate in the printing sequence is 0.02mm.
5. Ink formulation
Domestic from large-scale ink factory to small ink company, the production of gravure printing ink has basically been able to meet the requirements of printability. However, for the printing companies, it is not enough to satisfy the printability requirements. It needs to undergo multiple tests to meet the actual requirements. First, the hue, saturation, printability, postpress processing, friction resistance, high temperature resistance, leveling, adhesion, and resistance to folding, light, water, and bronzing of the ink should be prior to production. And so on to focus on testing. Neglecting any point may bring difficulties to production, fail to achieve an ideal input-output ratio, and may also cause difficulties for follow-up packaging, causing packaging users to feel a sense of distrust toward printing companies and even lose the market.
6. Formulation of gravure printing sheet
The gravure production process sheet plays a decisive role in guiding production. Each process item must be carefully and clearly listed (see Table 1). Only in this way, the production shop can implement the planned production according to the quality standards of the product requirements and carry out the planned production with good quality.
There are many studies in gravure prepress design and process arrangement that require serious study. There are many problems worth exploring. It needs to be flexibly changed according to different products and different requirements.