Inadequate production and operation adjustment of printing bars

(1) Incorrect ink roller pressure adjustment Ink roller and plate pressure are too large. When the ink roller contacts the plate roller, the ink roller impacts the edge of the plate, and the ink roller vibrates on the plate. The line speed changes instantaneously and the normal ink film is disturbed. The ink film at point A is disturbed and transferred to A' on the plate to form an ink bar, which may appear again at A" (A'A" arc length is the circumference of the inking roller).
Also in FIG. 1(b), the ink film at B may also be disturbed and transferred to the printing plates B', B" to form a bar (B'B" arc length equal to the circumference of the ink roller).
Although in order to avoid the occurrence of ink bars in the nip due to the vibration of the rubber roller, the plate cylinder is advanced by about 70mm in the design, but since a string of ink rollers is pressed against the two ink rollers, when the second ink roller jumps up, The ink fountain roller also goes up a bit, and the ink swaging roller also falls down when it falls. This run of the ink squeezing roller also affects the first ink roller at the same time; at this time, the first ink roller is already in the graphic, so it is generated. Bars, sheet-fed offset presses generally have four inking rollers and two underneath rollers, thus forming more than one tap-off. In addition, since the two inking rollers not only play an ink role on the printing plate but also play a role in collecting ink, the existence of the above phenomenon is the easiest cause of the lever, so it should be adjusted more precisely.
Ink roller with string ink roller pressure is too large. Since the ink roller is rotated by the friction of the plate cylinder and the ink roller, the pressure between the ink roller and the ink roller is too large, so that the ink roller depends on the ink roller too much, and the friction on both sides of the ink roller is not equal. There may be frictional slippage on the surface of the printing plate, which produces a bar.
In the same way, when the pressure between the water roller and the plate roller and the water roller is too heavy, it will affect the uniform transfer of the water film and cause white bars.
(2) Roller lining is excessive Because the pressure on the upper or lower pressure is too small, increase the lining of the roller lining, make the lining of the roller excessive, and intensify the speed difference and trace friction when the roller is rolling. From the microscopic point of view, the linear speed of the drum is not absolutely equal due to the influence of various factors. It is only a relative balance, and a certain degree of micro speed difference is always present. Overfilling the blanket results in excessive friction under the effect of the blanket, and there is intermittent wear and imprinting of the plate layout, resulting in a clubbing.
(3) Rubber and impression cylinders have too much pressure. Offset printing is accomplished by squeezing three rollers. There is a certain amount of squeezing force at the working face of the roller. When the drum runs to neutral, the load changes: When point B comes out of neutral, an impact occurs at point A.
Because there are tiny gaps in the roller bearing and the elastic deformation of the roller and bearing, the roller will produce slight displacement and cause vibration. The pressure between the blanket roller and the impression roller is too large, it will aggravate the vibration, and it will not roll. In the case of Pillow presses, this kind of vibration is not eliminated and produces a bar.
(4) Relaxation of rubber blanket When the blanket is too loose, due to the rolling action, the blanket slides back and forth on the surface of the drum. This relative movement will produce one or more bars.
(5) In case of over-printing in the offset printing press, too much water on the layout will affect the uniform transfer of the ink film, making the printing density too low and aggravating the emergence of bars. Therefore, for offset printing, under the premise of ensuring that the layout is not dirty, the amount of water supply should be controlled within the smallest possible range, and the amount of water supply and ink supply should be in a relatively stable state. A well-controlled ink balance is an important part of improving print quality.