Analysis of three failures of the most popular Ori

Analysis of three cases of Oriental rotary printing machine failure

at present, our factory uses the Oriental rotary printing machine to mainly print newspapers, periodicals, etc. Recently, there have been some uncommon printing faults in printing. The solutions to three of them are introduced to peers below

(1) we use the Oriental rotary machine to print, so we open four color newspapers. Once, there was a 20cm wide ink color on the green page of the fourth page of the newspaper, which was obviously lighter. Even if the ink volume was increased, it did not improve significantly, reducing the water supply of the whole page, which had a certain effect, but it was dirty and discarded in a moment. The shutdown inspection found that there was a large amount of ponding in the corresponding part of the ink bucket that could not be inked, that is, the water supply at the part that could not be inked was too large, and the excess water returned to the ink bucket along the ink return path, forming "ink" and causing the deinking failure of the ink bucket roller, affecting the ink supply of this part of the printing plate. At first, we suspected that the pressure of the water roller was inappropriate, and the effect was not obvious after adjustment. Later, replacing the new roller did not solve the problem. After careful inspection, it was found that the screw fixing the brush at the upper end of the brush roller supplying water to the water string roller was loose

the brush roller of Dongfang rotary machine adopts the spiral continuous spray water supply design. When the screw fixing one end of the brush is loosened, the brush spirally wound on the roller will shrink to the end that is not loosened. If it is not found in time, the brush radius of the seriously shrunk part will gradually increase, resulting in the increase of the contact pressure between this part of the brush and the bucket roller, resulting in the increase of the water supply to the string roller, When the water supply of other parts is normal, most of the excess water will return to the ink bucket along the ink return path, resulting in the difficulty of weighing the raw materials according to the formula and deinking with the ink bucket roller. Fix the brush again and let the electronic universal testing machine rise and fall regardless, that is, adjust the pressure when rising or falling, and the fault is eliminated

(2) for a period of time, there will be several thin black lines in the blank position of the time seam of the printed folio newspaper without newspaper seam, the length of which will not exceed the width of the newspaper seam. They are evenly arranged longitudinally at intervals of 4-5mm along the direction of a folded newspaper seam, and the position is relatively fixed. When the fault is serious, the black lines will spread, making the whole newspaper seam black. If the newspaper has seam printing, this fault does not appear. Increase the movement direction of the water beam and the opposite amount of the tensile test, the fault will be reduced, but the water volume of the text page is too large. During the shutdown inspection, it was found that there was a large amount of ink accumulation on the water roller against the plate at the corresponding gap. After erasing it and printing for a period of time, the fault will occur again, and readjusting the water roller pressure is not effective. So we focused on the ink supply part. After adjusting the ink roller pressure of the ink supply part for many times, we finally reduced the ink transfer and plate pressure of the two ink rollers by about 1/3, and the fault disappeared. After analysis, it is believed that due to excessive pressure, the ink at the gap corresponding to the printing plate ink roller cannot return to the ink bucket along the ink return path in time, but accumulates on the plate water roller, which affects the water supply from the water roller to the blank gap position of the printing plate, so the ink path and dirty fault appear

(3) for a period of time, when the two black pages of the newspaper were printed to about 10000 copies, there was a full page paste, and the seam position of the upper plate on the head and foot edge was more serious, that is, wiping the printing plate with cleaning paste did not work, and finally the printing plate had to be replaced. The analysis found that the two black plates had problems at the same time, which was unlikely to be caused by the failure of the water supply and ink supply mechanisms of the two groups of black plates. Therefore, we first took measures to make the common fountain solution, strictly controlled the amount of wetting powder, pH value of water, temperature of developer, etc., but the fault was still not eliminated. Finally, we replaced the black ink, and the fault was eliminated by ourselves. It can be seen that the fault is caused by the quality problem of the ink itself

(author/Shijiazhuang offset printing factory wuyingchun

Tangshan labor society printing factory xushifang Wang Bingyu)

source: printing technology 10/(Publishing and commercial printing)