Adjustment and Experience of Calibrated Printing Printing Accuracy (I)

As one of many color prints, Caibao has gradually penetrated into the field of people's material and cultural life with the development of the market economy. The reasons for the overprinting of the newspapers are not only intricate, but also the forms of their expressions. The most important and common ones are the inaccurate overprinting of different colors, the inaccurate overprint of the real part, and the inaccurate overprinting of outlets (or subtle parts). .
First, the material overprint is not allowed and adjustment This is the overprinting caused by material preparation is not allowed, or that the prepress preparation stage hidden overprint is not allowed, for color newspaper printing, this overlay can not be divided into:
1. The accuracy of the original plateau version is not a precondition for ensuring accurate overprinting. In the prepress preparation process, copying a large area of ​​the original, as long as the geometry of the various colors to ensure that the stability of the same, the graphic is guaranteed. However, when many small pieces of text are to be discharged on the same film, or when several small-area graphics are printed into a large-area printing plate, special attention must be paid to the accuracy of each version. Because, if the interval error is 0.02mm-0.05mm when you fight or put in the sun, the error accumulation will be quite large after several consecutive beats. Therefore, copying of this type of manuscript is best done on a full-page imposition system and a high-precision continuous shooting, copying, or linking machine.
2. Distortion and poor quality of paper due to moisture absorption Newspapers are printed on reel newsprint. Their distinguishing features are the strong hygroscopicity of the paper and the non-circular shape of the web.
The overprint caused by the wavy bending and tight edges of the paper is not acceptable. During transportation and storage, if the external humidity (water content) is greater than the moisture content of the paper, the internal moisture will not change, so no deformation will occur. Both sides of the paper edge are hygroscopic and produce stretch (commonly known as "foliage"); conversely, if the contained part of the paper can emanate moisture, the internal moisture remains unchanged. As a result, the edge of the paper shrinks and shrinks due to moisture removal. However, the interior is bulging due to relaxation to form a tight edge of the paper. If printing is performed on these two kinds of paper, when the paper is pressed between the impression cylinder and the blanket cylinder, it will cause a part of the paper to stretch and misprint occurs. To avoid this situation, we must pay attention to the tightness of paper packaging and the control of temperature and humidity in the storage environment during transportation and storage.
Inaccurate overprint due to web quality problems Due to inconsistent elasticity of the web at the time of production or inconvenience caused by inventories, the paper roll is not round, so that the entire web is not evenly stressed during printing, and paper is printed during the printing process. The pleats are tilted so that the colors are inaccurate. In this case, it is preferable to manually round the paper roll before printing, and during the printing process, the float roller is adjusted to balance the tension on both sides of the paper to reduce overprinting errors.
3. Thicknesses of thick-base printing plates can cause natural elongation and cause registration errors. When the thick-thickness printing plate is mounted on a roller with a larger curvature to form a larger wrap angle, under the condition that the pulling force is minimum, Its graphic size has a certain natural elongation, this phenomenon is the metal cracking phenomenon.
The geometrical shape of the metal plate section is usually a positive rectangle. When it is wrapped around the roller, the plate section becomes a sector. At this time, the front and back surfaces of the plate have different radii R3 and R1, and R3. >R1. Then, when the plate is bent tightly on the roller, the stress on the entire plate is extremely uneven, and the layout image size will be elongated with the cracking of the surface of the plate base. This cracking elongation value is the plate base. The resulting graphic natural register error difference, the elongation value is:
â–³L=0.5C/(R2+0.5C)
The extension of this graphic and text size is extremely small, and it has only a minimal effect on the general product and may be omitted. However, products with high requirements for overlay accuracy must be estimated in advance and corrected in advance.
Second, the process of printing overprint is not allowed (to be continued)