As the saying goes, "Three points look, seven points dress up!" This is true of people, especially of objects. With the improvement of human living standards, people pay more and more attention to the quality of life, and the requirements for goods have also changed from the original single focus on the internal quality to the need to have both a strong internal quality and a beautiful appearance. Beautiful and elegant external packaging is becoming more and more popular with consumers, and has greatly promoted consumption. The quality of printed matter directly affects the exquisite packaging. In this way, how to effectively control and eliminate various abnormalities in the printing process and effectively improve the printing quality has become an important issue for our printing colleagues.
In the printing process, due to many factors such as ink type, ink viscosity, doctor blade, platen roller, and original film, ink pollution, knife line, early drying, overflow, plugging, poor registration, etc. phenomenon. Based on my personal experience in gravure printing for many years, I will discuss the phenomenon, causes, and countermeasures of gravure printing abnormalities with each other.
First, paper break
Suddenly the paper or original film breaks during finger print.
1. The end face of the original film is damaged or notched
2. There are holes in the original membrane
3. The connector is not ready
4. Uneven tension (excessive)
5. If the film is always broken in a certain unit, the cylinder air pressure of the impression cylinder may be inconsistent for that unit
1. Check the end face of the original film carefully before rolling up. If it is damaged, it should be removed or replaced.
2. Re-perforate the membrane after breaking the membrane. If there are two holes in the same roll, replace the original film. Defective original film will be returned to storage.
3. Strengthen personnel technical training
4. Proper adjustment (reduction) of tension
5. Ask the maintenance department to repair the cylinder of the impression cylinder of the unit, and adjust the air pressure to make the air pressure on both sides of the cylinder consistent.
Wrinkling of the original film during printing
1. The original film itself has winding wrinkles, which leads to increased wrinkles after the guide rollers
2. Excessive printing pressure
3. Improper printing tension
4. Poor parallelism of the guide roller (including the pressure roller of the take-up section)
5. The support roller on one side of the guide roller is loose
6. Within the width of the original film, the guide roller is too dirty
7. The lack of true roundness of the impression cylinder (uneven thickness)
Replacement of the original film
2. Reduce printing pressure appropriately
3. Tension roller balance control
4. Adjust or repair guide roller parallelism
5. Have the maintenance department repair the backup roller of the guide roller
6. Stop and clean the guide rollers to ensure that the guide rollers are clean and free of ink accumulation within the original film width.
7. Replace the impression cylinder
Third, the continuous knife line
Where there were no lines, there were lines that moved left and right with the blade swinging from side to side. They were thick and thin, and sometimes there were many fine lines side by side. There is also a special case: the plate is scratched by a scraper holder or a foreign object stuck in the scraper port, resulting in a full circle of the knife line.
1. Broken scraper blade
2. Sundries (such as tape after cutting paper) are stuck in the blade
3． Ink contains hard debris
4． After cutting the paper, the tape sticks to the printing plate
5. The plate or scraper is not ground thoroughly
6. The plate is scratched by foreign objects
1. Wear anti-cut gloves and replace with new scraper
2. Exclude it with a sharpened bamboo stick (mild knife line can be excluded with a blower)
3． Filter or replace the ink with a filter (the easiest way: put stockings on the ink pump outlet and ink tank drain port for simple filtering)
4. Use a bamboo stick to remove the adhesive tape from the printing plate.
5. Regrind plate or scraper
6. Replace the backup version
特别 [Special reminder]:
It must be distinguished from the twentieth anomaly "scratch", the phenomenon is similar, and the meaning and cause are completely different.
Fourth, intermittent knife line (also known as shooting)
There are irregular, intermittent vertical stripe contamination on the printed matter (unfixed position, variable length, variable thickness, and different intervals).
1. The scraper is generated after the printing plate is worn out.
2. Squeegee pressure is too high
3. Ink has impurities (too dirty)
4. Lack of smooth surface
5. Ink itself is poor (lack of fatigue resistance)
1. Grind the scraper first with a grindstone and then with sandpaper until it is more thorough, or replace it with a new one
2. Adjust the scraper pressure appropriately
3. Use filtered ink or replace with new ink
4. Run the plate at no load before inking, and soak the plate with 1000-mesh sandpaper after soaking the solvent; intermittent cutting lines can be used in the production process.
5. Replace inks from other manufacturers
6. Recipe: Adding an appropriate amount of water to the ink also has a good effect (generally, 100ml of water can be added to a barrel of solvent-based ink with a viscosity of 20Kg that has been measured. Do not add excessively, otherwise the ink will cake. )
V. Sword Bone (also known as Sword Valley)
At the printing ink transfer ink, there is a strip-shaped blank line with no ink attached, which moves left and right as the blade swings left and right. The line where the blade is located is only missing a certain color, and it is impossible to have multiple inks missing at the same time. If multiple colors are missing at the same time, it is the ink scraping caused by the misfeed, not the blade.
1. Ink particles and debris on the blade
2. Poor ink: too dirty, many impurities, coarse particles
1. Use a bamboo stick to remove or shut down the cleaning blade
2. Dip some dry ink with your finger or a cloth without hard debris and apply it to the blade of the plate. The effect is very good.
It should be distinguished from the abnormal "scraping ink" of Article 19. The phenomenon is similar and the meaning and cause are completely different.