Prepress design of direct flexo printing of the ho

Prepress design of corrugated box direct flexo printing (Part 2)

Second, pay attention to the use of levels

due to different tastes of designers and different characteristics of products, there are differences in the style of packaging design. Some pursue simplicity and lightness, while others pursue richness. However, if its design works are realized through flexographic printing, the application of levels in its design must attract the attention of designers

because the flexible version is relief, and the material has high elasticity and is easy to deform, the point increases seriously after compression. In the process of plate making, 1% or 2% of the small points are easy to be lost during plate washing, and cannot be well reproduced in the printing process. 3% of the points will expand to about 10% after printing, and it is impossible to achieve the effect of gradual change from 100% to 0% or very soft layers, Therefore, flexographic products can show relatively few levels of highlights and dark tones, and products with better printing can only reproduce 8% - 10% of the highlights. Therefore, the point smaller than 8% in the design cannot be shown in the actual printing. For example, the use of gradient color, if the point gradient to 0%, there will be obvious boundaries or impressions in the small points or absolutely places, which will affect the image of the package. Although each manufacturer has its own way to overcome or solve this problem, in any case, flexographic printing cannot be comparable to offset printing. Only by taking this feature of flexo into consideration when designing, can your design be realized after printing

for another example, if the edge of the image is diluted to the extreme, the problems mentioned above will also occur, which requires designers to consider avoiding such problems when designing packaging

in addition, as mentioned earlier, the number of wrinkle roll lines used in Flexo inking is different from that of the eye adjusted version and the field version, and the low modulus is dominant. The large area of the field is connected with the correction time is short, and the local gradient is very difficult to print. Especially for manuscripts with darker field colors, the eye tone part is taken care of, and the field printing is not real or the color is light; After taking care of the field, the eye adjustment part is pasted, which is dirty. Although it can sometimes be solved by selecting a moderate number of lines and reducing the number of lines in the eye adjustment part, it is inconsistent with the designer's original design intention anyway

it is worth mentioning that in packaging design, gold and silver ink are often used to enrich the effect of packaging design and improve the quality of packaging. When using gold and silver inks, if the pattern contains eye tones, it is best to leave more space at the highlight and dark tones, and the highlight should be more than 20%, because this kind of ink printing point is easy to paste

third, consider printing registration

like offset printing and gravure printing, flexographic printing also involves overprinting. In flexographic packaging design, on the one hand, we should pursue the exquisite pattern, on the other hand, we should also consider the printing difficulty. For example, for small words and patterns, if you want to express them through overprint, because the overprint accuracy is difficult to ensure, it is bound to increase the scrap rate or make the printed patterns unsightly. This problem is usually solved by trapping. The trapping of corrugated boxes is usually 0.5 ~ 1mm, sometimes it may be slightly smaller for different printing machines. If it is difficult to print words and patterns under such a big trap, it must be adjusted accordingly. Especially for the overprint of complementary colors, there will be obvious black edges at the junction of the two colors, which will affect the aesthetic feeling of the packaging. Relatively speaking, dark and light overprint will be much better. In addition, a group of words or color blocks are overprinted by multiple units, which also increases the printing difficulty. Since most of the flexo printing machines used in China are driven by gears, the regular color block or line arrangement of one deep one light two or more colors in the packaging design will also cause difficulties for printing

the relief pattern on the flexo is formed by brushing the unexposed part off with the plate washing liquid and brush, so the flexo has requirements for the size of the smallest words and the thinnest lines. For corrugated box printing, we suggest that the thinnest line should not be less than 0.5mm. If it is an isolated line, it should also be widened appropriately. As for text, it is best to refer to the above data for the stroke thickness. Because the stroke structures of boldface and Song typeface are different, it is not easy to uniformly set the minimum font size. Pay special attention when using "Song Dynasty" font, because the contrast between the thickness of horizontal and vertical lines is too large

in the use of bar code, because the flexo plate is easy to deform under pressure during the printing process, and the plate is pasted flat on the round cylinder, it will also deform, so we must pay attention to the bar code processing. For different printing machines and bar code sizes, each bar code must be reduced in advance before plate making, so as to ensure that it can be detected after printing. Of course, this reduction is completed by the plate making manufacturer. Here, designers should be reminded to pay attention to the direction and size of the bar code. The size of the bar code should refer to the standard, and the direction of the bar code should be consistent with the printing direction as far as possible

fourth, pay attention to the typesetting effect of packaging design

in packaging design, general designers only pay attention to the finished product effect and plane effect of packaging, and pay little attention to the typesetting effect of packaging. Printing is a mass production process, which needs to arrange the single pictures of the packaging according to the width of the printing machine and the circumference of the plate roller. Therefore, the typesetting effect must be considered in the design. Especially when a single pattern needs to be arranged repeatedly, the color of the intersection position should be consistent or the design of the connected pattern should be continuous, so as to avoid the local pattern on one package appearing in isolation on the adjacent package on the layout due to the die-cutting deviation after printing, resulting in the unsightly package of the finished product. Such typesetting should be avoided as far as possible in the design

the above-mentioned problems involving typesetting are all small-size packaging. In fact, many corrugated box packaging are large-size packaging, such as refrigerators, monitors, etc. when designing these large packaging, we must consider the limitations of film output and plate making size. At present, the maximum plate making size of domestic flexo cannot exceed 2000mm × 1320mm, film output at 1100mm × Most of them are within 800mm. When designing large-size packaging, we should take these process characteristics into account. Patterns exceeding these sizes should not be designed as continuous patterns or overall patterns. Once designed in this way, the plates must be spliced before printing. No matter how carefully they are spliced, there will be obvious interfaces on the patterns after printing, which will greatly affect the exquisite degree of packaging. In the design, only considering the convenience of large-scale packaging printing plate disassembly, can the printed product meet the designer's creativity

v. try to use vector software in design.