Double image problem on the most popular web or sh
2022-09-30- Detail
Double shadow problem on web or sheet fed offset press
when the print is observed through a 100x magnifying glass or microscope, 15% - 25% of the point area on the print will show obvious double shadow problem. Its performance is that a light colored dot appears next to a dark dot, or the dark dot overlaps with the light colored dot (see Figure 1). The mechanism can be explained as follows: because the ink pictures and texts cannot be completely transferred from the rubber drum to the paper, a light color printable image is left on the blanket. In the next printing cycle, the fresh ink image transferred from the printing plate fails to be accurately aligned with the residual image on the blanket, and the image transferred to the next paper will form a double shadow. This is a troublesome problem of eye tone printing. Because the double shadows on each printing sheet are different, resulting in irregular changes in color intensity
there are two kinds of double shadow problems on the sheet fed printer. The first situation is that the blanket enters the embossing early, and usually occurs in the first printing unit. This is because the stiff paper or paperboard beats the blanket. So how big can this experimental machine test? For this reason, the technical personnel of Jinan Shijin consulting company got the answer. The second situation is caused by inaccurate overprinting between units. In most cases, this kind of overprint is caused by the misaligned timing of the paper gripper, improper adjustment of the paper gripper, wear of the paper gripper, dirt of the paper gripper, wear of the cam rollers or the appearance of ruffles on the paper. As a result, although the efforts of the printer and operators to maintain the printing density have been maximized by the operation instructions of the ball impact tester and the maintenance of the equipment, insiders still say that serious color deviation of prints will be caused
on the web printer, the double image fault is related to the paper material, the condition of the paper roll, the abnormal operation of the paper belt correction device, the deviation of the printer from the normal position, and the tension problem. Remember, the longer the paper route of the printing machine, the thicker the paper, the more difficult it is to ensure that there is no double shadow
in the face of double shadow and reduce its environmental impact, it is easy to explain what is double shadow, but it is difficult to explain what causes it, and it needs to pay a high cost to eliminate double shadow fault. When purchasing a new or used printing machine, if this problem is found, it is recommended to conduct a comprehensive test of the printing machine before it is installed in place
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