Solution to Color Card Printing Faults
At present, offset printing is the main printing method in printing factories. The main reasons for the delay in delivery due to the malfunction of the output system in offset printing are inaccurate overprinting, uneven ink color, and even the inability of the printing factory to proceed. This is one of the most difficult problems that printing factory workers often encounter.
1、 Printing product ink color unevenness fault
The reasons for uneven ink color in printing factory products include: (1) excessive wear on the cylindricity of rubber rollers for water, ink, uniform ink, and plate ink, wear on the shaft head of the bearing, aging of the rubber roller skin, and a decrease in ink transmission capacity; (2) The peeling of the water roller degree layer, excessive wear of the cylindricity, thin ink accumulation layer on the surface, and ink accumulation bands on the two ends, resulting in uneven ink movement of the roller; (3) The lock head that supports the water and ink rollers on the backing plate, swings the bracket, and is severely worn, causing the rubber roller to bounce when leaning against the plate, causing unstable pressure on the backing plate, resulting in ink imbalance, uneven ink color, dry plate, ink bar, old version (excessive pressure on the backing plate rubber roller), and other phenomena; (4) Aging or poor quality of the water roller fleece sleeve results in a decrease in water transfer capacity; (5) Failure to regularly check the pressure of each ink roller, plate roller, and the ink roller against the plate; (6) If the wear of the drum transmission gear exceeds the tolerance, there will be regular "gear ink bars" with the same spacing as the gears.
2、 Printing overprint fault
1. The impact of printing factory version deformation on overprinting. Metal plates have a certain degree of extensibility, and the printing factory will experience tensile deformation under the action of tension, while the tensile deformation of zinc plates is more common. When we found that overprinting was not accurate in our printing factory, we mostly adjusted it by stretching the printing plate. The greater the tensile force, the greater the stretching deformation of the layout, and the distribution of stretching deformation is uneven. The printing factory has the highest stress on the mouth edge and support edge of the layout, and its stretching deformation is also large. The inner edge has less stress, and the stretching deformation is also small. Therefore, printing factories should minimize the use of drawing plates to solve the problem of inaccurate overprinting.
2. The impact of the increase or decrease of drum liners on overprinting. During the printing process, the printing factory may use the method of increasing or decreasing the thickness of the drum liner to solve the problem of inaccurate inter diameter overprinting due to the expansion and contraction of the paper. The increase or decrease of the printing plate liner affects the stretching deformation of the printing plate. The thicker the printing plate liner, the greater the elongation of the graphic size. When reducing the plate liner and increasing the rubber drum liner, the tensile deformation of the looming fabric increases, and the radial deformation of the pattern increases. Another method is to reduce the thickness of the rubber drum while increasing the thickness of the printing plate liner, which reduces the deformation of the rubber blanket during extrusion. The latter is commonly used.
3. The effect of rubber blanket elongation on graphic overprinting. Rubber blanket has elasticity, and the tighter the blanket is stretched on the drum, the smaller the elongation and the smaller the pattern change. (1) Choose rubber cloth with low elongation. (2) During the overprinting process, try to keep the tension of the rubber blanket unchanged.
In addition to the reasons mentioned above, printing factories should also pay attention to machinery and adjustment for inaccurate overprinting
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