The flick angle refers to the phenomenon of inaccurate fit on one side of the trailing part of the printed paper. In recent years, most corner swing failures have occurred in multicolor offset printing. The main reasons are:
(1) The front gauge is not on a parallel straight line, which causes the paper to reach the front gauge with less paper on one side.
(2) The thickness of the paper varies greatly
(3) The pressure of each color group is increasing
(4) The blanket of rubber blanket is uneven
(5) There are differences in the tightness of the two sides of the impression roller gripper
(6) The individual tooth pads on both sides of the teeth of the impression cylinder are smooth or too low
(7) Due to the large blank area on both sides of the back of the printing plate, the amount of wetting fluid in this area is large, which causes the paper to attach more wetting fluid, causing the trailing portion to expand and contract, forming a flick angle.
(8) The amount of liquid used in the blank areas on both sides of the printing plate is different, and one side will also form a flick angle.
Similar failures have occurred in monochrome offset presses.
A factory uses a four-color folio offset press to print atlases, using 80g /? Offset paper. It is often found that some red and blue sleeves are not on the trailing edge, especially some special symbols, such as some city symbols are blue traps red. This phenomenon mostly occurs in the second half of the printed web.
The above example is an obvious flicker phenomenon. The main reason for this phenomenon is that the printing pressure is not decreasing enough, so the printing pressure should be re-measured and adjusted. In addition, it is also related to the tightness of the paper and the tightness of the grippers.
In the process of debugging the CP2000-CD102 machine, a factory carried out color printing tests after passing the inspection of various indicators, and added portraits of people in different positions on the black, cyan, magenta, and yellow 50% flat screens. The test results show that the coated paper and paperboard above 128g /? Are normal, and when the 80g /? Coated paper is tested, the phenomenon of "swing angle" occurs at the lower right corner of the printed matter, and the overprint of the corner gauge is not accurate.
This kind of "swing angle" failure is generally not related to the pressure of the various color groups of the feeding plate and the blanket lining. It may be related to the gripping teeth, but when checking the gripping teeth, the gripping force is normal, and then observe the double-diameter impression cylinder gripping teeth. When gripping the paper, the gripper does not grip the paper within a length of about 4mm in the lower right corner. The paper deforms slightly when pressed, resulting in a "swing angle".
Reset the position of the paper side pull gauge, adjust all related parts, and then turn on the trial printing to eliminate the fault.
Whether it is a multi-color offset printing machine or a monochrome offset printing machine, do not recklessly modify some key parts, pay more attention to the position and scope of the gripper. For harder paper, such failures are not easy to occur.
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