Troubleshooting of offset press ghosting
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1. When printing labels on the J4103 offset press and 80g/m2 coated paper, irregular ghosting occurs in the middle of the paper. The first analysis may be that there is a problem with the blanket lining or blanket installation, but the ghosting failure cannot be eliminated after re-adjustment. Then the prints were taken out and re-analyzed. It was found that the paper was turned over in a place with good light, and there was a corrugated wrinkle in the middle of the paper. This may be caused by the lack of force of the rubber roller and the force of the paper. The part moved backwards, but no problems were found by inspection. Then slowly jog the machine to check the intersection of the transfer paper and the impression cylinder, and find that the impression time of the impression cylinder is ahead of the time, and the smear angle of the dent is too small, because the dental shaft and the opening and closing teeth are connected. When the positioning cone pin is loosened, the positioning cone pin is re-fastened, and the ghosting of the boot printing is eliminated.
2. A Roland 702 offset press has been used for 5 years, generally printing 90-250g/m2 coated paper and cardboard. Once in the printing, it was found that there was a ghosting fault on the driving side of the printed product, and immediately stopped. According to experience, various influencing factors were investigated:
(1) Is the blanket aging? Since there is no ghosting on the operating side of the print, the cause of the aging of the blanket can be ruled out.
(2) Is the rubber roller lining different? After updating the package, the fault still exists, indicating that the problem is not there.
(3) Is the printing pressure balanced? After inspection, the printing pressure is consistent.
(4) Is the pressure of the plate water roller and the ink roller normal? After inspection, the pressure of each of the water roller and the ink roller was normal, and the ink was normal.
(5) Is the gripper loose? After inspection, adjustment, and trial printing, it was found that there was no ghosting problem in the first few sheets. The ghosting phenomenon began from the 10th sheet, and the time was heavy and heavy, indicating that the problem was not on the paper.
(6) Is the front gauge and side gauge normal? Checking the needle position and finding that there is a needle jump in the previous picture, so we suspect that it is a problem with the front gauge. However, after inspection, the front and side rules are also normal.
Finally, it was found that the platen roller on the driving side close to the front gauge was too loose, and after the adjustment, the ghosting failure was released.