The pattern printed by superimposing two or more colors on a light screen intermittently appears as dotless inkless transfers, like a starry night sky. There are a few white spots here, and a few white spots there. A small circle-shaped lack of ink, it is different from lack of ink and plug. (Suppose there is a bowl with a blue light net and a red light net overprinted. If you see a small white dot like a star in the bowl, you can see that this point is a blueish or reddish color. Phase. If it is a pan-blue phase, it is a red drop point; a pan-red phase is a blue drop point)
Current color viscosity is high
2. The current color scraper angle is too small (ie the scraper is too flat)
3. High ambient temperature
4. The previous correlated color viscosity is too high
5. The front is irrelevant, but the area is large and the color viscosity is high (this situation is rare)
Reduce the viscosity of the current color ink
2. Increase the current color scraper angle
3. Reduce the ambient temperature of the printing shop (if conditions permit the use of electrostatic ink absorption devices, the effect will be better)
4. Reduce the viscosity of the ink of the previous color (such as red dots when blue and red are overprinted. If reducing the red viscosity is not effective, you can consider reducing the blue viscosity)
5. Reduce the viscosity of the unrelated but large area of the previous color [for example: Master ’s classic condensed milk flavored milk tea, blue and red spots appear on the bowl superimposed by blue, red and yellow, and the background color (the first color is pearly white ) The pattern of the bowl is hollowed out. The improvement effect was not satisfactory, whether it was reducing the blue viscosity or the red viscosity. After reducing the background color viscosity to ≤12.0 seconds, the drop point immediately improved. 】
Twelve, poor adhesion
The adhesion between the printing ink and the original film is not good, and the ink can be easily scraped off or peeled off. The common inspection method during acceptance: Use 3M tape to flatly adhere the ink on the printing surface, and remove the tape at a speed of 1m / sec. Generally, 90% of the ink does not fall off to be regarded as qualified. Scotch tape is more viscous than 3M tape, and it is cheaper. When printing, the test adhesion can generally be determined simply by using Scotch tape.
Corona treatment strength of the original film is insufficient
2. The original film has expired
3. The original film corona surface is reversed
4. Ink used incorrectly or mixed with different inks
5. Solvent use error
6. Poor drying (the ink is not completely dried)
7. The ink itself is bad and lacks adhesion
1. Detect the intensity of corona treatment, select the original film with qualified corona treatment strength
2. Outdated materials are discontinued, and materials within the validity period are selected
3. Switch the printing surface
4. Gravure printing inks are mostly used for various special purposes. Different types of inks should be placed separately to prevent misuse. The remaining ink should be clearly marked (name, type), and stored properly to avoid mixing when reused.
5. Pay attention to using the correct solvent type and ratio
6. The dryer gives heating at the right temperature
7. Change the ink with better adhesion of different batches or different manufacturers
Thirteen, water pattern
Irregularities in the length of the printed ink appear on the surface of the printed matter (especially the large area with the most obvious background color). In most cases, the appearance of the watermark is whitish (that is, lighter than the original color). Deeper
1. Poor ink stick (the length is not enough to reach the two sides of the printing plate or the ink stick has serious wear)
2. The ink tank is too high, so that the lowest point of the printing plate is too close to the ink tank, resulting in poor ink flow.
3. The paper on the back of the scraper is too long and curled, causing the ink to flow poorly.
4. Poor ink (more air bubbles or lack of fluidity)
5. Defective ink pump or air entering, causing a lot of air bubbles to blow out and collect near the printing plate dots when printing ink.
6. Improper inking method
1. Replace the better ink stick
2. Appropriately lower the ink tank (with the principle of no shortage of ink), so that the lowest point of the printing plate and the bottom of the ink tank have appropriate space
3. Shorten the back stopper so that the stopper does not curl
4. Add defoaming agent or replace ink of other manufacturers with better fluidity
5. Replace the ink pump, or block the bubbles with cardboard to prevent bubbles from converging near the printing plate dots
6. Change the middle ink to the side ink
Fourteen, throwing ink
The splash-like ink droplets appearing on the printed matter generally appear mainly on both sides of the edge of the printed matter. (However, due to the different printing models, the inking method is not the same. Some printing machines that use ink guide rollers to apply ink, or apply ink from the middle of the ink tank, will also throw ink in the middle of the printed matter.)
1. The scraper on the edge of the printing plate is seriously damaged
2. Depressed ink blocking paper is bad or broken
3. The protective film of the shaft head is damaged, and the printing ink is dropped during the printing process, so that the original printing film is splashed.
4. The air flow from the ink pump's ink outlet is too large, and the printing ink is blown onto the printing original film.
5. The ink volume of the ink tank is insufficient, which causes the ink pump to blow bubbles out of the ink outlet and blow the ink onto the original printing film.
6. The surface speed of the ink guide roller is too high (the speed is too fast)
7. The ink in the ink tank is not flowing smoothly, it is foaming and crusting, and it is brought to the plate roller (a special form of ink rejection)
Replacement with new scraper
2. Re-insert the blocking paper
3. Rewind the shaft head protective film with tape
4. Adjust the ink pump airflow
5. Add ink in time so that the ink level in the ink tank is sufficient to immerse the ink inlet of the ink pump
6. Reduce the surface speed of the ink guide roller (with the principle of no shortage of ink)
7. Add ink roller (also called ink stick) so that the ink in the ink tank always flows without foaming or crusting.
Fifteen, poor registration
Finger overprinting is inaccurate and misaligned, resulting in blurred prints. Or it should have been a single line and turned into two or three lines, with poor overall registration, poor single-sided registration, OK on both sides, and poor intermediate registration
1. Poor original film (wrinkle, single side drooping elastic side)
2. The guide roller is too dirty, and the original film is not running smoothly.
3. Insufficient platemaking accuracy
4. The impression cylinder is too long, and there is ink accumulation in the area wider than the original film.
5. Impression roller has poor roundness and uneven thickness
6. Inconsistent cylinder pressure settings at both ends of the impression cylinder
7. Imprint cylinder failure, resulting in inconsistent pressure at both ends
8. Staff negligence, not adjusted to the best position
9. The wind pressure in the drying box is unstable
Replacement of the original film
2. Wipe the guide rollers so that no foreign matter such as ink is deposited on the original film, so that the original film runs smoothly.
4. Replace the impression cylinder with a suitable width
5. Replace the embossing cylinder with better roundness (mark the embossing cylinder with poor roundness at the same time and place it separately for grinding and repairing)
6. Adjust the pressure at both ends of the impression cylinder to make them the same size
7. Ask the maintenance department to repair the cylinder of the impression cylinder
8. Strengthen the professionalism education of printing staff and improve the quality concept
9. Adjust the air pressure of the oven
The two cases of poor registration in one side, normal registration in both sides and poor registration in the middle belong to the special category of poor registration. The former 95% of cases are personal reasons and have not been adjusted in place. It can be corrected by its own color registration correction wheel on the printing equipment; of course, there are very few due to insufficient platemaking accuracy. The latter is caused by a bad impression cylinder. Generally, the wrinkle in the middle of the printing film can be seen in the color that is overprinted, and the pressure of the impression roller can be reduced to make it flat. If it is still not resolved, you can only replace the impression cylinder.