Influential factors of different shades of ink before and after printing
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In offset printing, there is sometimes a phenomenon in which the ink color of the printed product is not deep before or after the front (from the pressure, the front is heavy or the light is light and the front is light and heavy), which affects the quality of the printed product. The causes of such phenomena can be analyzed from the effects of rollers, ink rollers and water rollers.
(1) The center of gravity of the drum is biased toward the middle side of the sputum. It appears shallow before the front and then light and heavy before the front; when it is biased toward the side of the tip, the front is shallow and the front is light and heavy. This is caused by the inconsistent pressure between the mouth and the tip of the roller when the roller rolls. The side of the pressure is increased, and the ink color is deep; the side of the pressure is lighter and the ink is lighter.
(2) The change of the radius of the printing surface of the drum can also cause failures, such as the lining of the drum, or the poor quality of the lining, and the thickness is inconsistent, resulting in inconsistent pressure and uneven ink color.
(3) The pressure between the inking roller and the inking roller is too light, resulting in uneven ink transfer, which is large and small. In particular, the pressure between the inking roller and the inking roller and its relationship with the printing plate must be adjusted evenly, and cannot be light on one side. It should be noted that the pressure of the inking roller and the printing plate is greater than the pressure of the inking roller and the inking roller to facilitate separation and transfer of the ink.
(4) The diameter of the inking roller should not be too small, otherwise the amount of ink transfer will not reach the demand for printed graphics.
(5) The surface of the inking roller is aged, and the capillary hole becomes a smooth surface, which causes uneven ink transfer, and is prone to failure of ink color before and after. The ink roller can be ground to a desired diameter to roughen the surface and increase the adsorption and transfer properties of the ink. Especially after printing the varnish, the ink roller should be carefully washed (the varnish remains on the ink roller, so that the surface of the ink roller is crystallized and the pores on the ink roller are filled up. In severe cases, the rubber on the ink roller is pulled out, resulting in Ink roller scrapped).
(6) The water roller and the plate pressure and the pressure adjustment of the water roller and the water roller are inconsistent, causing the water to be suddenly large and small, affecting the adsorption of the ink against the plate.
(7) The water roller is bent to cause uneven water supply and should be replaced in time.
(8) When the water jacket is installed, foreign matter is loaded, which causes the radius of the water roller to change, which affects the uneven water supply.