Prepress design for direct flexo printing of corrugated boxes
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In the past, the main function of corrugated boxes was as a transport package, and the surface printing was very simple. The reason: First, the carton factory and users do not pay attention to the packaging design of corrugated boxes, only the carton as a tool to protect and contain the products; secondly, the corrugated carton surface is relatively flat, it is difficult to print a beautiful pattern; The previous printing editions were all hand-printed, and it was impossible to reproduce fine lines and dots. Of course, there are also reasons such as insufficient number of printing units, which limit the rapid development of carton printing.
In recent years, with the rapid development of the economy and the increasing exchanges with foreign countries, people are increasingly aware of the importance of packaging and decoration, especially the influx of international supermarkets such as Wal-Mart and Carrefour, and the increasing number of domestic supermarkets. People have changed the traditional shopping habits, and at the same time, the sales function of corrugated boxes has become increasingly prominent. Users are increasingly paying more attention to the outer packaging of the carton display product and company image. At the same time, the widespread use of flexographic (photosensitive resin) and the rise of flexographic prepress technology have also given strong support for carton printing.
In the field of packaging design, the past color packaging or exquisite packaging design is mostly achieved by offset printing and gravure printing. Offset printing and gravure printing as a mature printing method, there are still many printing suitability designers need to pay attention to packaging design, flexo printing as a new printing method, in order to truly reproduce the designer's packaging design, it is more necessary for designers to Learn more about the characteristics of flexo printing. Designers must pay attention to the following points when designing prepress prints for corrugated box direct flexo printing.
First, the color number of the creative expression
Thousands of worlds, colorful, especially the eyes of designers, are good at discovering beautiful colors, and organizing them organically, creating a variety of elegant or elegant, or bold, or warm, or have a strong visual impact. works. As a packaging design, the ultimate goal is to achieve your own creative effects after printing, and to achieve industrial production. Therefore, for the packaging design of corrugated carton direct flexo printing, in terms of color application, we must first understand that our creativity is realized on several color printing machines, and clearly define our own creativity through several colors. The number of domestic corrugated box flexo printing presses is generally 2, 3, 4, and 6. Before confirming the use of several colors, on the one hand, it is necessary to consider the number of color groups of the printing machine. On the other hand, it must be considered whether the white ink is used or not, and whether the varnish is used, thereby finally determining the color number that can be used to express the creativity.
Of course, under the premise of fully expressing the design creativity, the number of printing colors should be reduced as much as possible, which is beneficial for printing operations, quality control, and cost control in mass production.
In addition, there are many manufacturers, hoping to use as many spot colors as possible to achieve the color uniformity of each batch of products, and play a certain anti-counterfeiting effect. Therefore, its packaging in the design in addition to the traditional CMYK4 color, more is the use of spot color ink. However, in practice, due to the limitations of the printing press, the manuscripts that need to be printed on the four-color machine can't be displayed in any color when they are separated. In the end, they have to communicate with the designer to make the similar colors into one color. Or make changes to the designer's work.
Since flexo printing is carried out by an anilox roller, the number of anilox roller lines determines the amount of ink transferred and the fineness of printing. In general, the mesh screen should use a high-line anilox roller to make the dot printing clear; while the solid version uses a low-line anilox roller to achieve color saturation. In a color, there are both the mesh image and the field, and when the visual is relatively prominent, the color is generally divided into a mesh version and a solid plate separately for color separation to facilitate the printing operation. Therefore, when considering the overall color number in the design process, do not ignore this feature of color separation in flexo printing.
In addition, this is often the case in practice, that is, many corrugated box presses are three-color machines, and normal four-color printing cannot be realized. Therefore, in the process of coloring the corrugated box watermark, three colors are often used. Reproduce four-color manuscripts. There are two practical situations to consider when producing black with three-color overprint:
(1) ink color cast makes three-color overprinting produce non-standard black;
(2) Three-color overprinting will make the ink layer too thick, affecting the printing quality and effect.
In the above two cases, the designer should understand the condition of the ink when processing the packaged product printed with the three-color machine. Some printers use the color cast of the ink. When processing, it is necessary to properly consider the color intensity of the partial color. Some manuscripts do not necessarily remove the black version. For example, the reproduction of the food can remove the green version, and the reproduction of the tree can remove the red version. This maximizes the style and level of the original. If the problem of printing color number is taken into account in the design, the above difficulties will not be encountered before mass production. For example, when we were designing the design of Tsingtao beer carton, we considered it to be realized by a three-color printing machine, so the corrugated carton watermark colorization printing process was smoothly realized and promoted in the market.
Second, pay attention to the use of the level
Due to the different tastes of the designers and the different characteristics of the products, there are differences in the style of the packaging design. Some pursue simplicity and clarity, and some pursue rich levels. However, if the design works are realized by flexographic printing, the application of the level in the design must attract the attention of the designer.
Since the flexible version is a relief, the material is highly elastic and easily deformed, so the dot gain is more serious after being pressed, and during the plate making process, 1% or 2% of the small dots are easily lost during the printing process, during the printing process. It can't be reproduced very well, and 3% of the dots will expand to about 10% after printing. It is impossible to achieve a gradient of 100% to 0% or a very soft layer, so the highlights and darkness of flexo products can be expressed. The level of the adjustment is relatively small, and the printed product highlights can only reproduce 8% to 10% of the outlets. Therefore, less than 8% of the dots in the design are not shown in actual printing. For example, if the gradient is used, if the dot is changed to 0%, there will be obvious boundaries or impressions at the small dot or the net, which will affect the image of the package. Although each manufacturer has its own way to overcome or solve this problem, in any case, flexo printing is not comparable to offset printing. Only when you design this time to take into account the characteristics of flexo, you can achieve your design after printing.
For another example, the edge of the image is faded. If it fades to the net, the same problem will occur. This requires the designer to consider avoiding such problems when designing the package.
In addition, as mentioned above, the number of anilox rolls used for flexographic ink transfer is different for the mesh adjustment and the solid version, and the large-area field is connected with a partial gradient, and printing is very difficult. In particular, the manuscripts with darker colors in the field took care of the part of the nets, which was printed on the spot or was light in color; taking care of the field, the part of the net was smeared and dirty. Although it can sometimes be solved by selecting the appropriate number of anilox rolls to reduce the number of screen lines in the mesh portion, it is inconsistent with the original design of the designer.
It is worth mentioning that in the packaging design, many times, gold, silver ink, etc. will be used to enrich the packaging design effect and improve the packaging grade. When using gold or silver ink, if the pattern contains mesh, it is best to leave more space in the highlights and shadows. The highlights are preferably above 20%, because such ink printing dots are easy to paste.
Third, consider printing registration
As with offset and gravure, flexographic printing also involves overprinting problems. In the design of flexo packaging, on the one hand, we must pursue the exquisite design, on the one hand, we must also consider the difficulty of printing. For example, for small texts and patterns, if they are to be overprinted, it is difficult to guarantee the accuracy of overprinting, which will inevitably lead to an increase in the scrap rate or an unattractive print pattern. This problem is usually solved by trapping. The trapping of corrugated boxes is usually 0.5 to 1 mm, and sometimes may be slightly smaller for different presses. If the printing of characters and patterns is difficult under such a large trap, it must be adjusted accordingly. In particular, the complementary color of the overprint, the two-color junction will have obvious black edges, affecting the beauty of the packaging. Relatively speaking, dark and light overprints will be much better. In addition, the printing of a set of text or color blocks by multiple units also increases the difficulty of printing. Since most of the flexo printing machines used in China are gear-driven, the arrangement of a dark, two-color or multi-color regular color block or line appearing in the packaging design will also cause difficulties in printing.
The embossed pattern on the flexographic plate is formed by brushing off the unexposed portions by the styrofoam and the brush, so the flexographic plate is required for the size of the smallest word and the thinnest line. For corrugated box printing, we recommend that the thinnest line be no less than 0.5mm, and if it is an isolated line, it should be properly widened. As for the text, the stroke thickness is preferably based on the above data. Because the stroke structure is different between the bold type and the Song type, it is not easy to uniformly set the minimum size. Pay special attention when using the "Great Song" font, because the contrast between the horizontal and vertical lines is too large.
In terms of bar code use, since the flexo is easily deformed under pressure during the printing process, the plate is flattened onto the round drum and deformed, so attention must be paid to the bar code processing. For different printing machines and different bar code sizes, each bar code must have an early reduction before the plate making to ensure that it can be detected after printing. Of course, this reduction is done by the plate making manufacturer. Here, the designer should pay attention to the direction and size of the bar code. The bar code size should refer to the standard, and the bar code direction should be as consistent as possible with the printing direction.
Fourth, pay attention to the layout effect of packaging design
In the packaging design, the general designer only pays attention to the finished product effect and the plane effect of the package, and rarely pays attention to the layout effect of the package. Printing is a mass production process that requires a single image to be arranged according to the width of the printing press and the circumference of the plate. Therefore, the layout effect must be considered in the design. In particular, when a single pattern needs to be repeatedly arranged, the color of the intersection position should be uniform or the connected pattern design should be continuous to avoid the local pattern on one package appearing adjacent to the layout in isolation due to the die-cutting deviation after printing. On the other packaging, the finished packaging is not beautiful. Avoid such typesetting as much as possible during design.
The above-mentioned problems involving typesetting are small-sized packages. In fact, many of the corrugated carton packages are large-sized, such as refrigerators, displays, etc., when designing these large packages, film output and plate-making dimensions must be considered. limitation. At present, the maximum size of the plate making size of the domestic flexo plate cannot exceed 2000mm×1320mm, and the film output is mostly within 1100mm×800mm. In the case of large-scale packaging design, these process characteristics are taken into consideration, and patterns exceeding these dimensions are preferably not designed as a continuous pattern or an overall pattern. Once this is designed, it is necessary to splicing the plates before printing, and then splicing them carefully. There will also be obvious interfaces on the printed patterns, which greatly affects the delicateness of the packaging. At the time of design, only the convenience of dismantling large-size packaging printing plates can be considered, so that the printed products can conform to the designer's creativity.
Fifth, try to use vector software when designing
At present, most designers use computers as tools to display their own ideas. The design software has vector forms, such as: Illustrator, Freehand, CorelDRAW, etc., in pixel form, such as: Photoshop, Panit, etc., do not all in the design process. Photoshop and other pixel-based software, Photoshop is best used to process images or make some special effects. Other lines, texts, and color blocks are best produced by vector software such as Illustrator, Freehand, so that the manuscript is sent to the plate-making company. The plate-making company can make some adjustments to the design draft more conveniently and quickly for the characteristics of flexographic printing, such as trapping, lowering the curve, etc., to achieve the effect of printing. When designers send their designs to electronic printers or plate-making manufacturers, it is best to convert all the texts in the design draft into a path before data storage to reduce the recipient's font changes due to incomplete fonts, etc. . If there is more text to change or no text is to be converted to a path, the corresponding font and design manuscript should be sent to the data recipient.
In short, to print good printing results through corrugated box direct flexo printing technology, we must fully consider the characteristics of corrugated box flexo printing technology from the beginning of manuscript design, which also requires designers, plate making manufacturers, printing manufacturers, end users to share Strive to negotiate.