Analysis of the most popular offset preprint techn

In order to attract people's attention and stimulate people's desire to buy, corrugated boxes, as outer packaging, can be used in automobile interior decoration strips, door handles, rear-view mirrors, exterior decoration strips, bumper lower guard plates and other components, which have been designed more and more beautifully. Offset preprint corrugated boxes are one of the most important means to achieve these exquisite designs

the offset preprint corrugated box process is to first use the corrugated board production line to produce single-sided corrugated board, at the same time, carry out fine color eye adjustment offset printing on the surface of the face paper, then paste the face paper onto the single-sided corrugated board with adhesive, and finally complete the corrugated box forming process through die cutting/slotting, gluing/nailing

however, there are many weaknesses in this printing process, so other printing processes have developed rapidly and are likely to surpass and replace them. So, what are the disadvantages of offset preprinting and how to overcome them in the actual production process to cope with the competition of various printing processes in the market? In this regard, we interviewed several professionals from packaging and printing enterprises that produce corrugated boxes by means of offset pre printing. They are Mr. wangguoping, director of the operation Department of Wuhan Huaheng color high-end packaging Co., Ltd., Mr. wangdongjing, chief engineer of Baoding Xingliang printing factory, Mr. Kuang Fengyuan, Langfang 1206 printing factory, and Mr. Li Jun, Beijing Chaoyang welfare paper products factory, I hope that the problems and solutions they encounter in the actual production process can be used for reference and help

I. problems that should be paid attention to in carton design

when printing corrugated carton paper by offset printing, there are often problems such as the size of the carton does not meet the requirements due to improper packaging design and process design, ghost shadow, poor gold and silver printing effect, easy paste, scratch, dull printing, uneven ink layer thickness, heavy front and light rear due to improper packaging design and process design

in the interview, the following requirements were put forward for corrugated box design and process design:

(1) when designing cartons, the thickness of the corrugated board used should be considered. Generally, the finished product size given by the customer is the internal size, and the external size should be calculated and determined according to the material and thickness of the corrugated board used

(2) the layout text should not be too fine. The main function of the exquisite corrugated box is to highlight the effect of promoting commodities. The graphics and fonts should not be too small, otherwise they will not play a role in publicity. Words less than 2cm can not be seen clearly when they are 5m away, so the significance of promoting and selling goods is lost

(3) it cannot be designed as four-color large-area flat overprint, because 250g/m2 gray background white board paper is mostly used for corrugated box surface paper, which is poor in texture and easy to deform, drop slag and powder during printing

(4) the color sequence should be considered in the design. If the color sequence is improper, the printing effect will not be good

(5) gold and silver ink shall be placed at the end of printing. When printing gold or silver background color, if there is a pattern or text on it, you should first print gold or silver, otherwise it will be stewed back

II. Problems related to printing equipment

1 Printing equipment

printing equipment has the most direct impact on the printing quality of corrugated paper, and different equipment has different effects. At present, domestic offset printing machines used for corrugated paper printing are basically imported second-hand equipment (such as Heidelberg, Manroland, etc.) and domestic high-quality equipment

the imported second-hand equipment will have some problems more or less after long use, such as machine vibration, slow machine speed, inaccurate overprinting, ink bars, etc. Wuhan Huaheng color high-end packaging Co., Ltd. has two second-hand Manroland offset printing machines for printing corrugated box tissue paper. The above problems arise in production. Mr. wangguoping is very helpless about the problems of second-hand equipment, because Wuhan Huaheng color high-end packaging Co., Ltd. is mainly engaged in Budweiser beer packaging boxes, and customers have extremely strict requirements on product quality. Although domestic high-end equipment has been quite good, the printing effect is still one grade worse than that of foreign equipment on the whole. If you buy imported new equipment, the investment is quite large, The varieties that have been industrialized and have a wide range are mainly homobenzene polyimide, polyamide imide (PAI), polyetherimide (PEI) and bismaleimide (BMI). A new Heidelberg offset press will cost about 20million yuan. Therefore, we can only try to avoid these problems. Once a problem occurs, we can improve it, but we can't improve it in advance

during the printing process, Langfang 1206 printing factory has experienced equipment related failures, such as inaccurate overprinting, color difference in connection, ink rising bar, resulting in printing products' blooming, discoloration, ghosting, hair loss, peeling, etc. The first-line production personnel solve the above problems by adjusting the machine, changing the paper, adjusting the pressure and water supply

for inaccurate overprinting, Mr. wangdongjing, chief engineer of Baoding Xingliang printing plant, suggested using a four-color offset printing machine to print corrugated box paper. Because the printing can be completed at one time, the impact of paper times and pumping deformation on overprinting is avoided

unsolved problems: the printing ink of the monochrome Offset Press is full, but it is prone to inaccurate overprint; It is difficult to solve the problem that the four-color offset printing machine overprints accurately, but requires a large amount of powder, and the ink color is not full enough. For problems that cannot be overcome by the equipment itself, only different models can be selected according to needs

2. Ink

first of all, corrugated box printing is also very picky about ink. The covering power of the ink should be strong and the color should be bright. As the color of the corrugated board itself is quite dark, the ink with high color saturation and strong coloring power (such as bright red) should be selected as much as possible when selecting the printing color, otherwise the printed color will be very different from the desired color

secondly, the viscosity of the ink should be appropriate. If the ink viscosity is too high and the paper quality is not good, there will be paper sticking and depilation. At this time, it is necessary to add a certain amount of ink blending oil to dilute it

Wuhan Huaheng color high-end packaging Co., Ltd. generally selects different inks according to the requirements of different customers. Budweiser beer packing cases are mainly printed with peony brand ink, which is of good quality. In addition, the company has its own set of quality inspection system, which tests the raw materials before warehousing. If the quality of raw materials does not meet the requirements, they will not be warehoused and will be directly returned to the supplier. The company once had the problem of poor adhesion between ink and paper, so it took the method of requiring suppliers to replace them. Otherwise, the company would look for suppliers of other brands. In short, the principle is to meet the needs of customers

summarize other problems related to printing ink of all respondents when printing face paper: the ink is too thick or too thin, and the printed matter has ink skin and dirt; Ink drying too fast or too slow, drying too fast causes color change, drying too slow is easy to cause rubbing dirty. The solution is to use high-quality ink instead, that is, the ink that does not dry on the plate cylinder or on the paper, or add ink blending oil and additives

unsolved problem: I hope that some technology or company can improve the heavy metal content of ink

3. Paper

the surface paper of corrugated box shall meet the requirements of smooth surface, no dirty spots or fuzzing, accurate cutting size and vertical corners

at present, domestic paper is mainly used for corrugated box face paper. There are many problems with domestic paper, mainly including:

(1) there are many paper powders

(2) the paper is uneven and has poor flatness

(3) the water content of the paper is either too high or too low. Generally, the standard moisture content of paper is about 7%, but the moisture content of paper produced by Southern and Northern manufacturers is different. The moisture content of paper produced by Southern manufacturers is high, while that of paper produced by northern manufacturers is low. All these factors make the printed face paper fail to achieve the expected printing effect, which greatly reduces the advantage of exquisite offset printing

the corresponding solutions are as follows:

(1) during printing, install flannelette on the plane where the paper feeding part of the machine contacts the paper, and remove part of the paper powder like a broom

(2) if the paper is uneven, which makes the technical status of the equipment meet the requirements of the rules and equipment standards, the problem should be solved with the supplier. As long as the paper quality does not meet the requirements of the packaging materials, it can not be put into storage, let alone on the production line

(3) if the water content of the paper is too low, it can be stacked for several days to slowly absorb moisture, while if the water content is too high, it can only be returned

in addition, when printing corrugated paper, attention must be paid to the texture of the paper. If the corrugated paper is mounted longitudinally, the horizontal strand paper shall be used, while the horizontal corrugated paper shall be mounted longitudinally. In this way, the mounted cardboard is flat and straight

unsolved problems: the quality of domestic paper is not as good as that of imported paper. There are some problems, and the price of imported paper is too high

(to be continued)