Quality control method for series of printed materials of different materials
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In the packaging and printing process, different materials are often used to print the same or similar layouts, such as the product's internal and external packaging, trademarks, specifications and other series of printed products. Generally, the color layout of the printed layout or logo is basically the same, but because The differences in the characteristics of the substrates, the printing equipment, ink properties and process forms used by some products are not necessarily the same, and customers often require that the printing color requirements of the series products be basically the same, and no obvious color difference can occur. The actual production process shows that the control of the ink quality of the series of printed materials of different materials has certain difficulty. It requires careful design of the process technology and careful control of the operation technology to obtain better printing quality effects and meet the quality requirements of customers.
1. the characteristics of series of prints and process determination methods
The so-called series of prints means that the specifications of the inner and outer packagings of the same product are different or the printed materials of the complete sets of products are different, but the layout or color of the graphic layout is the same or similar. The adaptability of the printing process is also quite different due to differences in material properties or print layout specifications. For example, corrugated boxes and color box printing materials on the outer packaging include whiteboard paper, kraft card or cardboard paper, etc. The carton packaging materials include whiteboard paper, kraft card, white card, glass card, copper plate card, and PE coated paper. Etc., flexible packaging plastic film, cellophane, tissue paper, glossy paper, copy paper, offset paper, vacuum aluminum paper, laser paper, etc. Corrugated cardboard has large thickness and flatness characteristics, as well as PE coated paper, plastic film, cellophane, tissue paper and vacuum aluminized paper printing process. It is suitable for flexographic printing from the aspects of material characteristics and safety and sanitary quality of product packaging. Printing with water-based inks can better guarantee the quality of the products. For pre-printed color box paper, color box printed white paper, kraft card; vacuum aluminized paper, laser paper and other materials, a large number of can use gravure or flexographic process, can make print quality and production costs are obtained Better balance. For whiteboard paper, kraft card, white card, glass card, copper plate card product with a quantity of about 100,000 impressions, as well as glossy paper, copy paper, offset paper, vacuum aluminized paper, and laser paper, the offset printing process is suitable. Among them, the gloss paper and copy paper are low in quantity, and are not suitable for high-speed automatic paper feeding. The low-speed 01 offset printing machine can be used for printing, so as to better ensure the overprint quality of the product.
2. we must pay attention to the process technology control of prepress layout design
Nowadays, many printed materials are provided by customers with electronic manuscripts designed and produced by their own design or advertising companies. Due to their incomplete understanding of the printing process, the manuscripts produced often fail to meet the requirements of the printing process. Taking a series of prints of the same textured structure as an example, the printed colors may vary greatly due to the different printed materials used. It is a paper disc (whiteboard paper material) and a paper cup (single-sided PE coated paper) which are also printed by the offset printing process. Since the surface smoothness of the whiteboard paper material is good, the ink absorption amount is small, and the single-sided PE coating is small. The surface of the paper is relatively rough, and the amount of ink absorbed is larger. The printing of the same layout with the two materials will result in a large difference in color. Generally, the printing color of single-sided PE coated paper is obviously lighter than that of white paper. The amount of ink and pressure adjustment often fail to overcome the chromatic aberration problem that occurs when the printing performance of the material is different. Generally, the main color dot area of the printed single-sided PE coated paper should be appropriately adjusted by the plate making design to make the printing color close. Therefore, when receiving a series of printed materials with the same texture and different printing materials, it is necessary to carefully analyze the original layout structure and the material characteristics of the substrate, and then determine a reasonable plate making design, that is, according to Material gloss, printing ink absorption performance, reasonable adjustment of the dot area of a certain product layout to ensure that the colors printed by different materials are close to each other.
3. we must pay attention to the process technology control of the imposition direction
Multi-imposition structure of printed matter, usually one piece of different types of layout on a printed sheet. If the difference of printing colors of different varieties is not taken into account, and different varieties with different color differences are spelled in the same vertical direction, then once in the vertical layout If the printing color of a certain type of layout is shallow or deep, it is difficult to locally adjust the ink output through the ink fountain to realize the ink color control of a certain type of layout of the corresponding vertical layout. The ink color adjustment often appears to be in the wrong situation. Take into account the printing color of the vertical overall layout.
Therefore, for multi-imposition paper plates, paper cups, trademarks and other products, each longitudinal position is best to match the same variety or color matching, in order to facilitate the effective adjustment of the amount of ink coating. It is forbidden to spell a product with a large contrast in color in the same longitudinal orientation. Because such imposition printing is most likely to produce chromatic aberration, even if the printing color can be controlled by adjusting the amount of ink coating, it is easy to produce chain printing quality problems, such as Draw paper, paste, dirty and other bad conditions.
4. adjust the control network size through the printing process
The main features of a series of prints are generally the same as the graphic, but the difference in size, while the material properties of the substrate are completely different. If the already created film structure is the same, you can consider the exposure time of the main color version of a certain product according to the glossiness and ink absorption of the substrate layout. Implement the adjustment of the dot size. Taking the substrate of the series products as glass and offset paper as an example, the offset paper surface is relatively rough and the ink absorption amount is large, and the exposure time of the main color plate can be appropriately shortened to achieve the purpose of increasing the dot area, so that printing The offset color of the offset paper print can be close to the ink color of the glass card print layout, and it is not prone to paste defects. However, it must be pointed out that the adjustment of the size of the outlets by the printing section is limited, and it can only be a slight adjustment. If the exposure time is too short, the darkness of the layout will be prone to deadlock, and the layout will be poor. Therefore, the exposure time adjustment should be in accordance with the appropriate degree, such as the original normal exposure should be 140S, the shortened exposure time to control between 110s ~ 120s.
5. control the printing color by adjusting the printing pressure
Printing pressure is the medium of imprint transfer. The printing pressure is directly reflected in the depth of printing ink color, especially in the letterpress printing process. The pressure has a great influence on the depth of printing ink. When the printing pressure is increased, the printing color will appear. Deepen the phenomenon, on the contrary, reduce the printing pressure, the printing color will appear shallow. For a series of prints of different substrates, when the surface of the printed material is rough, the printing pressure can be appropriately increased to deepen the printing color, so that the color of the printed materials of different materials is close. However, the printing pressure adjustment should also control a suitable degree. Excessive pressure adjustment can easily accelerate the printing plate wear, and it is easy to produce chain quality problems such as paste plate and printing plate deformation. This is a problem that should be paid attention to during the printing process. . Generally, the adjustment of the letterpress printing pressure should not exceed 30 wires. Otherwise, the printing deformation will directly affect the overprint quality of the product.
6. through the ink hue adjustment control printing color
The four-color prints are printed according to the conventional process using standard four-color inks. However, when there is a significant difference in the color of a certain color, the ink color adjustment is still not achieved by the ink amount adjustment, and the hue of the ink of a certain color may be considered. Appropriate adjustments make the ink color of the printed product meet the requirements of the original color. For example, when we print a four-color trademark at a time, there is a noticeable reddish color in the light orange color after overprinting, and the yellow hue has a distinctly insufficient feeling, which is quite different from the original color, and the amount of M color is reduced. The increase and adjustment of the Y color are limited and cannot be adjusted to the requirements of the original ink color. In this case, it seems that only by appropriately reducing the dot area of the M version and increasing the dot area of the Y version can the effect be effective. Adjusting the color effect, however, is laborious and time consuming, and increases the economic cost, which is not advisable. Through careful analysis and research on the printed samples, the author found that in addition to the overprint relationship between the Y-color partial layout of the flat screen and the M-color version of the flat screen, the M-color version has no separate monochrome color printing result, so The author germinated in the "four-color red" ink, added some "four-color yellow" ink, formed a special spot color red ink for overprinting, after this treatment, the light orange overlay printing surface, printing color instantly Achieve similar effects to the color of the sample, so that the printed color of the product finally meets the requirements of customers. By the same token, in printing a series of prints of different materials, the hue of a main color is often slightly shallow due to the difference in materials. For this reason, it is conceivable to adjust the ink hue of a certain color to achieve the printing ink color. Correction, this is also the easiest and fastest way.
7. Control printing color by using different printing process characteristics
Due to the difference in printing process, the thickness of the printed ink layer is also significantly different. For a series of printed materials with large differences in materials, according to the adaptability of the printing plate color and materials to the printing process, the appropriate process is selected for printing, and the printing color is also controlled. An effective way. The thickness of the ink layer of various printing processes is about: offset 3μm; embossing 8μm; flexo 10μm; gravure 12μm; silk screen 30μm, according to the basic properties of the substrate, surface gloss, ink absorption, and layout In the case of structure, etc., consider the selection of a printing process suitable for the ink absorption characteristics of the substrate material, as appropriate. The offset printing process is limited by the balance of ink and ink. The adjustment of ink coating amount is small, and it is suitable for printing substrates with relatively good gloss, such as coated paper, glass card, white card, offset paper, whiteboard paper, kraft card, and the like. The napkin is soft in texture, large in ink absorption, poor in tensile strength, and easy to stretch and deform, so it is more suitable for printing with low-viscosity liquid water-based ink, in order to obtain the desired printing color, and the water-based ink has great environmental advantages. Therefore, printing a napkin with a flexographic process is the best choice. The choice of printing process should consider the influence of the printing characteristics of the substrate on the printing color, as well as the printing production cost, such as the high cost of gravure and flexographic printing, which is more suitable for printing long-line products.
8. different material series print quality control methods
Due to the limitations of the scale of the printing factory, some factories only have a single flexo printing process, and some factories have a single offset printing process or gravure printing process. Many series of printed materials are often sent to several factories for printing. . Due to the cost of production, some customers have not used the proofing process, which is often the printing of a certain type of material, which is used as a reference for the color of another material, such as the first printed flexo napkin as the offset white paper. The contrast of paper or coated paper cup printing color brings certain difficulty to the printing color control, and it is often difficult for the offset printing to keep up with the black color of the flexo printing. Because the flexo ink layer is thick, and the offset ink layer can be adjusted in a relatively small range compared to the flexo printing process. Therefore, to print a series of prints with different processes, it is advisable to arrange the products printed by the offset printing process to be printed with flexo, gravure or silk screen, which is beneficial to the control of the color of the series. If the products of different materials are also printed by the offset printing process, the materials with good glossiness should be printed first, and the materials with poor glossiness should be printed. Because of the glossy material, the amount of printing ink is relatively more accurate, which reduces the chance of large deviations in printing color. It is worth mentioning that the use of printed manuscript as a control color of the printing color, pay attention to the effect of the light transmittance of the sample material on the identification of color vision, such as film prints, napkin prints with high transparency, should be placed side by side with the printed sample in the standard sample Identification on the stage.
In summary, to control the color of series of printed materials of different materials, it is necessary to pay attention to the comprehensive consideration of material characteristics, printing process technology and equipment operation adjustment, and through careful technical analysis of the original, and then determine the appropriate production process plan, so Not only can avoid the blindness of the production process, reduce the occurrence of printing defects, but also better ensure the printing quality of the product and effectively improve the production efficiency.