Small carton and carton products often have various structural layouts coexisting. For example, there are layouts mainly based on field printing, as well as printing layouts with coexistence of netting, text, lines and solid patterns; both gold and silver layouts that spectral colors cannot display, and layouts with spot colors and four primary colors coexisting. If offset printing, embossing (or gravure printing, etc.) processes are used in different printing methods, the printed products each have advantageous process characteristics. Multi-process combination for printing carton, carton and other packaging products can improve the internal quality of the product. The printing effect of offset printing is good, the color is soft, the dots are clear, the printing level is rich, and the large area of ​​the printing surface is not prone to the phenomenon of sticking dirty products. The embossing and gravure printing process has the advantages of thick and full ink layer, bright colors and high gloss. Therefore, use the advantages of different printing processes to print those products that have a combination of mesh, text, lines and solid patterns, as well as layouts of various colors, combining the advantages of different printing methods, using the process "synthesis" to print the same The product can not only give full play to the utilization rate of the equipment, but also improve the product quality and economic benefits simultaneously.
Various reasonable arrangements combined with printing process
The offset printing process has light printing pressure, relatively small printing deformation value, and the product is not prone to sticking to the bottom phenomenon, so it is suitable for printing chromatographic screens, lines, fine text, negative images and large-area solid layouts.
The relief printing process can achieve a large amount of ink supply at one time, which is more suitable for printing gold, silver ink layout, solid, line or text layout. In terms of printing characteristics, the ink layer of the offset printing process is thin, the ink is also easy to dry, and the product does not produce embossed marks, which does not affect the normal overprint of the embossed printing. The ink color of the relief printing process dries slowly, which will cause some adverse effects on the normal color registration. Therefore, the overprinting sequence of the combination of offset and convex should generally be: offset printing first, then convex printing later; small printing first, large area printing later; ink with strong hiding power, ink after strong transparency Printing, such as red and yellow (with the exception of white ink dilution), black text or patterns are overlaid on the layout, the black layout can be printed first, and other colors are printed afterwards. In this way, due to the strong transparency of the overprint color, black can still show pure black Color. [next]
The technical control essentials of combining multiple processes with printing
1. Do a good job in the technical control of pre-press design
The relief solid layout should avoid the small shaded lines and text in the same color version, so as to avoid the pressure and ink supply cannot be taken into account, and it is easy to produce paste and uneven pressure, which affects the printing quality of the product. The overprinted parts of the offset printing plate should be separated as far as possible, so that there is a certain gap around the edges of the overprinted plate surface or the edges of the light-colored plated plate can be appropriately enlarged (so that the edges of the overprinted plate surface can be stacked and covered), so that slight overprinting is not allowed. It's hard to detect with the naked eye.
2. Do a good job in the technical control of the imposition process
The overprinted parts of the layout should be as close as possible to the bite and pull gauge (side gauge) to avoid the inaccurate overprint due to the expansion and contraction of the paper. In addition, the layout of the "Ghe River" (separate core) with a large layout or multi-block color registration should not be spelled as two types of processes for overprinting.
3. Pay attention to the reasonable selection of offset plates
The PS plate has a thinner plate material. After it is installed on the surface of the cylinder, its wrap angle is relatively small, and the elongation of the printing plate is also small. Moreover, it can maintain tight contact with the cylinder, which is beneficial to improve the overprinting of rubber and convex products. Accuracy, therefore, the offset printing process should choose PS version for printing.
4. Pay attention to the process technology control of the plate support
Small-sized packaging products are often printed with a letterpress machine with four-fold or half-round flattening structure. The characteristics of the base material of the printing plate have a great influence on the printing pressure, overprint accuracy and ink quality effect. effect. The traditional wooden undercarriage has poor material, squareness, flatness and stability. It is prone to bowing and deformation, and the printing quality is difficult to guarantee. Therefore, letterpress printing should use solid, flat, square, and stable aluminum or cast iron magnetic plate and other metallic materials. This is the basis for improving product registration and ink quality. [next]
5. Pay attention to close the printing pressure control technology
The printing pressure should be adjusted evenly and moderately. If the pressure is too large, the printed sheet will be stretched and deformed, causing overprinting. Therefore, the printing pressure of the embossing process must not be too large, and the lightest printing pressure should be used to meet The ideal ink is printed on the premise that the ink color on the layout is uniform and full.
6. Pay attention to close the technical control of the lining process
The liner is the medium that realizes the transfer of pressure and imprint. What its characteristics also affect the registration and ink quality of the product. Therefore, the deformation coefficient of the lining material should be as small as possible, and the material should be neutral and hard. At the same time, the thickness of the lining must be determined in strict accordance with the technical parameters of the equipment specifications. In addition, the liner must be tightly packed, and there should be no loose or bulging state. Do not repeat patching or hollowing on the embossed liner to prevent overprinting and ghosting.
7. Pay attention to close the technical control of good ink and ink balance
To control the water-ink balance in the offset printing process, it is necessary to print with the smallest amount of fountain solution supplied while maintaining the water-ink balance. The abnormal balance method of "big ink and big water" should be avoided for printing to prevent deformation due to excessive water absorption on the paper surface.
8. Pay attention to control the temperature and humidity of the printing environment
Controlling the temperature and humidity of the printing workshop is an important part of improving the accuracy of product overprinting. The temperature and humidity of the offset printing and embossing workshops should be kept relatively balanced, and there should not be a large difference between high and low, otherwise, it is easy to cause overprint . In general, most small and medium-sized printing enterprises are unable to effectively and accurately control the temperature and humidity of the production site due to the limitations of conditions. They are often controlled by simple methods such as opening and closing doors and windows or using water splashing on the ground based on experience. Certain role.
9. Pay attention to the technical control before the cardboard is put into use
Cardboard is very sensitive to changes in the temperature and humidity of the external environment, especially the white cardboard that has just been produced is most prone to expansion and contraction due to changes in temperature and humidity, resulting in inaccurate product overprinting. In order to reduce the chance of this happening, the white board that has just been produced will usually be stored for a period of time after it is shipped back to the printing plant. After the characteristics of the board are relatively stable, it will not be easy to produce overprinting after being put into use. In addition, the cut cardboard should be sent to the printing workshop immediately to balance it with the temperature and humidity of the printing workshop, and then printing is helpful to improve the registration accuracy of the product. [next]
10. Pay attention to the technical aspects of the paper cutting process
The accuracy of the specifications of the cardboard will also affect the product's overprint. Because of different machine structures, their front and pull gauge positions are not the same. In this way, if the edge of the cardboard is not cut enough to be square, and there are beveled or wavy edges, it will cause overprinting. This requires products with glue and convex joints. The sides of the cardboard must be cut at right angles and straight lines, and there must be no beveled or wavy edges. In order to improve the cutting accuracy of the cardboard, the cutting thickness must be strictly controlled, because the thicker the paper stack and the softer the paper, the more the paper surface deforms when the paper press is pressed, so the cutting thickness of each stack of cardboard The less it is, the better it is to improve the cutting precision of the cardboard. In addition, the edge of the blade should be kept sharp, and the appropriate blade angle should be selected according to the hardness of the paper, which is also an important measure to improve the cutting accuracy.
11. Pay attention to master the production cycle of product overprinting
After the previous color or colors of the printed product are printed, those that can be overprinted should immediately perform overprinting, so as to avoid the expansion and contraction of the printed product due to the long time delay, resulting in inaccurate overprinting.
12. Pay attention to the protection of printed semi-finished products
After printing, the semi-finished product should be sealed with plastic film to prevent the cardboard from absorbing external air moisture or losing moisture, so as to avoid or reduce the undesirable phenomenon of expansion and contraction of the semi-finished product.
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