Printing failures associated with offset presses When printing offset paper on corrugated boxes with an offset press, the printing failures associated with offset presses are numerous and can be summarized as follows.
(1) Imprinting is not allowed. There are many reasons for overprinting, such as machine overprinting accuracy is not enough, should be overhauled; blanket loosened; plate plate clamps loose; paper sheet transfer between the unit is not stable; delivery paper teeth open, bad teeth closed; open Closed tooth spring breaks or oily eye, oil rust, rust: the front edge of the paper is not uniform before entering the machine, or both ends of the paper passively enter the tusks. After entering the unit, the paper that has passively entered the cavities is displayed equally.
(2) Water bars and ink bars. It is generally caused by the uneven contact pressure of the water roller and the ink roller. In addition, check whether the bearings of the ink roller and the water roller are stuck or intermittent. Printing also pay attention to the control of ink balance.
(3) Dots increase or decrease or are lost. Should start with the following aspects to check and solve: whether the pressure is right; whether the blanket is aging or rolling injury: the cylinder surface of the printing machine is worn or foreign objects such as oil stains. There may be a regular dot gain in the missing teeth of the transmission gear or iron chips between the teeth. Foreign matter: Roller bearing damage, so that the net point of the lateral bar-shaped increase, and then reduced; Blanket elasticity is not good, or printing pressure is too large, beyond the elastic limit of the blanket, the dot will appear sometimes increased, sometimes reduced or lost, The blanket and liner should be replaced. Too much ink or foreign material on the pillow or the blanket is too wide. When one end is higher than the pillow, the pressure will be unbalanced. As a result, the dot at one end increases, and the dot at one end decreases.
(4) Stick dirty flowers. Due to the high basis weight of corrugated box paper, it is generally 180g/m2 or more, high stiffness, poor winding, but strong resilience, easy to produce sticking phenomenon, therefore, in the printing unit should be positioned according to the die cutting position Anti-punching device, if necessary, can also be used to place a sponge mat on the paper transfer roller corresponding to the ink-less or less-inked part. In addition, due to the high basis weight, the phenomenon of paper falling from the tusks during printing is also more common. Therefore, when adjusting the front gauge, it must be ensured that the paper feed is smooth, and after the paper has fully entered the front gauge, it is pressed and printed again. Adjust the enthusiasm for a good collection of teeth. Because the reverse side of the carton face paper is gray-backed paper, poor flatness, pay attention to the back of the delivery and stacking paper sticky, can increase the amount of dusting, and control the pile height, so that the delivery as tidy as possible.
