Reasonable arrangement of various combined printing processes
Offset printing process with light pressure, print deformation value is relatively small, and the product is not easy to appear dirty over the bottom phenomenon, it is suitable for printing chromatogram version, lines, small text, negatives and large area layout.
The embossing process can achieve a larger amount of ink at a time, and is more suitable for printing gold, silver ink layout, field, line or text layout. According to the characteristics of printing, the ink of the offset printing process is thin, and the ink is also easy to dry, and the product does not have protrusions and does not affect the normal overprint of the stamp. The ink of the embossing process is drying slowly, which will have some negative impact on the normal color registration. Therefore, the overprinting order of adhesive-convex-bonded products should generally be: first printing on the offset printing plate, and then printing on the embossed printing plate; printing on the small layout first, printing on the large-area layout; printing on the ink with strong hiding power, and printing after the ink with strong transparency. Printing, such as red and yellow (with white ink diluting exceptions) Overprinting black text or patterns on the layout, the black layout can be printed first, and the other colors printed afterwards. In this way, due to the transparency of the overprinting color, black can still reveal a pure black color. Color.
Combination of multiple processes and printing technology control methods
1, do a good job pre-press design process technology control
Embossed on-site layout should be avoided in the same color with small lines and text, so as to avoid pressure and ink supply can not fully take into account, easy to produce paste version and pressure uneven phenomenon, affecting the product's printing quality. The position where the overprinted surface of the convex printing plate is overprinted should be as far as possible, so that there is a certain gap around the edge of the overprinting plate or the edge of the light colored platen is appropriately enlarged (so that the edge of the overprinting platen can be overlapped and covered), so that slight overprinting is not allowed. Unnoticeable to the naked eye.
2, to make the technical control of the imposition process
The part where the layout is overprinted should be as close as possible to the bite and the pull gauge (side gauge) so as to avoid overprinting and inaccurate phenomena due to the paper's expansion and contraction. In addition, layouts with “large rivers†(separate cores) with large or multi-colored layouts should not be used for overprinting with two processes.
3, pay attention to the reasonable choice of offset printing plate
The PS plate has a thin plate material. After it is installed on the roller surface, its wrap angle is relatively small, and the plate plate has less elongation, and it can maintain a close contact with the roller, which is advantageous for improving the overprint of the rubber convex product. Accuracy, therefore, offset printing process should be selected PS printing.
4, pay attention to the good technical support
Small-size packaging products are often printed on a letterpress printing machine with a four-ply or split-semi-circular structure. The characteristics of the plate's substrate are greatly affected by printing pressure, overprint accuracy, and ink quality. effect. The traditional wooden pallet, the material is not solid, squareness, flatness and stability are relatively poor, prone to bowing and deformation, printing quality is difficult to guarantee. Therefore, letterpress printing should be based on a solid, smooth, square, stable aluminum plate or cast iron metal plate, which is the basis for improving product registration and ink quality.
5, pay attention to the good printing pressure control technology
The printing pressure should be adjusted evenly and moderately. If the pressure is too high, it will easily cause the sheet to be stretched and deformed, causing overprinting. Therefore, the printing pressure of the embossing process must not be too large, but the printing pressure should be as light as possible. Perfect printing on the premise of even and full ink layout.
6, pay attention to the technical control of a good lining process
Lining is the medium for the transfer of pressure and blotting. Its characteristics, as well as the product's registration and ink quality. Therefore, the coefficient of deformation 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 lining must be tightly packed, and there must be no loosening or drumming. The relief lining should not be lining up repeatedly to make up or hollow out in order to prevent overprinting and ghosting.
7, pay attention to the technical control of good ink balance
The offset printing process controls the balance of ink and ink, which is to print with the smallest amount of dampening fluid supplied, while maintaining the balance of water and ink. It should be avoided to use the "abnormally large ink and water" imbalance balance method 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 shop is an important part of improving the accuracy of product overprinting. The temperature and humidity of the offset printing and embossing workshops should maintain a relative balance, and there can be no large gap between the high and low conditions. Otherwise, overprinting is not likely to occur. . In general, most small and medium-sized printing companies are limited by conditions and cannot effectively and accurately control the temperature and humidity at the production site. They often use experience to control the opening and closing of doors and windows or to use simple methods such as water splashing on the floor. A certain role.
9. Note the technical control of the cardboard before it is put into use
Cardboard is very sensitive to changes in the external environment of temperature and humidity, especially the white paperboard that has just been produced. It is most prone to stretching and variability due to changes in temperature and humidity, resulting in inaccurate overprinting of products. In order to reduce the chances of this happening, the white paperboard that has just been produced will generally be stored for a period of time after it is shipped back. After the characteristics of the paperboard are relatively stable, the overprinting phenomenon will not easily occur when it is put into use. In addition, the cut cardboard should be sent to the printing shop immediately, so that it can balance the temperature and humidity of the printing shop, and printing can help improve the accuracy of the product's registration.
10. Pay attention to the technology of cutting paper
The accuracy of the paperboard specification also affects the overprinting of the product. Because of the different machine structures, their front gauges and pull gauge positions are not the same, so that if the edge of the cardboard is not squarely cut and there are beveled or wavy edges, overprinting will not occur. This requires a glue-convex combination of products, the side of the cardboard must be cut into right angles, straight lines, there must be no bevel or wave edge phenomenon. In order to improve the cutting accuracy of the cardboard, the thickness of the cutting must be strictly controlled, because the thicker the paper stack and the softer the paper, the more the paper surface deforms when the paper presser presses down, so the cutting thickness of each stack of cardboard is The less, the more conducive to improve the cutting accuracy of cardboard. In addition, the edge of the blade should be kept sharp, and according to the hardness of the paper, select the appropriate blade angle, which is also an important measure to improve the cutting accuracy.
11, pay attention to master the production cycle of product overprint
After the printing of the previous color or a few colors of the printing product, the overprinting should be performed immediately to prevent overprinting due to time delay, resulting in inaccurate overprinting.
12. Pay attention to the protection of printed semi-finished products
After printing, the semi-finished products should be sealed with plastic film to prevent the cardboard from absorbing moisture or moisture from the outside air, so as to avoid or reduce the occurrence of telescopic variability in semi-finished products.
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