The principle of three operations that must be adhered to during the printing process

Sample check

1. Sample inspection in the initial printing stage

(1) Inspection of sample ink color. When checking the sample, start from the mouth of the paper, look at both sides and look at the direction of the tip, scan the entire screen for quality problems, and whether the ink color meets the standard proof. If the ink color of the whole picture or local area does not conform to the standard proof, it should be adjusted in time. The adjustment means can not be limited to the adjustment of the amount of ink, but also the amount of water should be considered.

(2) Inspection of sample size. After checking the ink color of the sample, you should quickly check whether the T-line on the proof sheet meets the requirements, especially the proofs printed on both the front and the back. Check the front and back T-line and the size of the mouth.

(3) Inspection of outlets. In the initial printing stage, the difference between the dotted lines between the printed proofs and the standard proofs should be compared with the magnifying glass to see if the printed dot lines are empty, whether there is a significant increase, and the quality problems such as vertical and horizontal deformation and ghosting. If similar quality problems are found, the causes should be analyzed in a timely manner and adjusted and eliminated.

(4) Inspection of other quality problems. In addition to the need to check the color, specifications and outlets of the sample, the inspection of the various quality ills that often occur is also an important task in the initial printing phase.

2. Sample inspection during normal printing stage

(1) When the ink and water balance is gradually stabilized, the sampling frequency should generally be 3 times/500 sheets. Due to the complexity and variety of physical and chemical factors in the printing process, the focus of the proofs is still the color and rules. When checking the ink color, you can compare the two sides of the sample with the middle part, or compare the sample before and after, and compare it with the sample sampled several times before; if there is any change, you can make a slight adjustment to the ink supply amount. When inspecting the rules, 2 to 3 proofs should be taken, and the mouths of the squares should be smashed and spread out to see if the T-squares are consistent. The positioning of the front and side gauges is accurate. If it is found to be inaccurate, the cause should be identified in time. And to be excluded.

(2) After continuous printing for a period of time, the paper powder, paper wool and fine ink in the ink can easily adhere to the printing plate or blanket, causing the lines or the print on the sample to become thick and hairy. Unclear, the outline is blurred. When this is the case on the proof sheet, stop the foreign matter adhering to the plate or blanket. Moreover, in order to prevent the change of the ink color caused by the shutdown, it is generally necessary to continue printing after 8 to 10 sheets of paper. If the printing quality is affected by the adhesion of foreign matter, the plate and blanket should be cleaned. At the same time, it should be observed whether the small dots on the shiny part of the plate are worn out and whether it needs to be changed.

(3) In addition, you should also pay attention to and check whether the back of the sample is sticky. In general, the sample should not be piled too high, otherwise it will cause the back to be dirty.

Control of ink balance

1. The relationship between the amount of water supply and the color of the ink

In the initial printing stage, in addition to frequent observation of the sample, the amount of water in the layout must be observed and controlled. It should be noted that the ink color cannot be adjusted simply by reducing or increasing the amount of water supplied. Experience has shown that in the actual production, under the premise of ensuring that the printing plate is not sticky, the water supply should be controlled within the smallest possible range, and the water supply amount and the ink supply amount should be relatively stable. The ink color of the printed product is consistent before and after the printing and the printing operation is stable.

2. Identification of the amount of water

In the daily printing process, the operator often identifies the amount of water by visually measuring the amount of light emitted by the layout. This method also has certain limitations. This is because of the limitation of the area of ​​the printed plate and the area of ​​the blank part, the type of the plate, the intensity of the light, the angle of the observation position, etc. different.

In addition to the above methods, it is also possible to judge from the following points that the water volume of the layout is too large: the ink knife is used to shovel the ink on the ink roller, and the ink knife has small water droplets; the ink transfer roller has fine water droplets. There are water drops in the ink fountain slot; the layout often appears to be floating. After the machine is stopped for a long time, the printing plate is still not dry; the imprint at the mouth is wavy, the ink color is dull and dull; the sample is curled, soft and weak, and the rubber roller There are small drops of water at the tip of the trailer; when printing continues after the stop, the ink color of the print is quite different from that before the stop.

3. Control ink and water balance

(1) Master the principle of less water and less ink.

(2) In general, when printing on a PS plate, a smooth surface, and printing speed, the water supply can be relatively small.

(3) The temperature and humidity of the environment cannot be ignored.

(4) Control the pH of the dampening solution to keep it at 5-6.

(5) Others. If the ink on the entire print screen is dark or light, it can be adjusted by adjusting the ink roller corner; if the ink is too dark or too light in the local area of ​​the print, it can be adjusted by adjusting the individual ink fountain screws.

All in all, in the printing process, the operator must adhere to the three-dimension operation, that is, check the proofs frequently, observe the amount of water in the dip, diligently stir the ink in the ink fountain, so that the ink balance is always in a normal stable state, so as to ensure the stability of printing quality and printing. The work went smoothly.