Proofing is the bridge between plate making and printing. Its quality is good or bad, which directly affects the quality of plate making and printing.
At present, there are many ways of color proofing, and gradually shift from traditional proofing to digital but traditional machine proofing. The following is an analysis of some common problems in traditional machine proofing.
1. Too many dots
Especially in summer, when the indoor temperature is too high, without air-conditioning equipment, it will inevitably increase the ink fluidity. The general solution is to add 2% extra oil to the ink to increase the viscosity of the ink; Decrease 1 ～ 2 ℃, increase the cohesive force of the ink, after this treatment, the increase rate of dot will be improved.
In addition, the reasons for the increase of the outlets are the following factors, which should be mastered.
(1) The pressure of the plate is too high. The platen pressure is preferably in the range of 0.1 to 0.11mm, and the paper table pressure should be in the range of 0.12 to 0.13mm, which is beneficial to improve the excessive dot increase.
(2) The aging of blankets. If the blanket is used for too long, the surface is oxidized, the elasticity is weakened, and the surface is smooth. Proofing with such a blanket has poor ink absorption and poor transfer performance, which will inevitably cause excessive dot gain. Therefore, it is necessary to replace the new blanket in time.
(3) The pressure of the ink roller is too large, the ink roller is aging, and the ink roller itself cannot catch the ink. The pressure of the ink roller should be adjusted in time according to the standard. The pressure of the ink roller and the plate should be adjusted to 6mm, and the pressure of the ink roller and the ink roller should be adjusted to 4mm. And replace the ink roller in time.
(4) The amount of ink is too large. Sometimes due to the light version, in order to chase the original, not according to the standard data operation, the amount of ink is increased too much, causing the dot to increase too much. Therefore, in any case, you must strictly follow the standard data operation, you can not borrow deep, shallow, and the original version is too shallow, you should improve the original version.
(5) Excessive moisture. If the moisture is too high, the ink will not be printed. To print the ink, the ink will be thinned and the amount of ink will be increased, which will inevitably cause the dots to increase too much. Therefore, moisture must be controlled during operation.
(6) If the cooling temperature of the plate is set too high, the cooling will not work, so that the ink cannot condense and the fluidity is large, resulting in an excessive increase in dots. Adjust the refrigeration equipment in time and master the fluidity of the ink.
2. The dots appear hollow
Sometimes the proofing dots increase too small, and the dim sum appears hollow. There are several reasons for this situation.
(1) Due to the low indoor temperature and low relative humidity in winter, the cooling of the printing plate is too low during operation, the viscosity of the ink is large, the ink solidifies on the plate due to excessive cooling, and the blanket transfers the printing plate when transferring ink The ink on the top is pulled up, the surroundings are pulled up and the center is retracted onto the printing plate, resulting in a small white dot in the center of the dot.
(2) The PS version is rough and the grit is too coarse.
(3) Unsuitable pressure, etc.
The solution is:
(1) The temperature of the platen can be increased appropriately.
(2) Add 5% desalting agent in the ink to make the ink moisturized and have proper fluidity.
(3) Use PS plates with uniform grit and moderate thickness.
3. Samples are matt
Sample matt is mainly caused by too hard ink, low fluidity, insufficient ink volume, and low color saturation. The solution is:
(1) Using "8" prefix ink, 5% of desalting agent can be added to the four main colors, so that the gloss of the sample can be improved.
(2) The amount of ink must be sufficient to achieve the best solid density, the proof will be shiny.
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