When printing a PET product, the black, red, and blue colors are not clean enough, and no effect can be achieved by the printer's adjustment. The measures taken are to increase the blade pressure, replace the blade, plate roller, and adjust the solvent. For this printing failure, we make the following analysis and give suggestions for improvement.
Scratching is not clean: Also called dragging. There is a big difference between scratching and cleaning.
Scrape is not clean: It is the phenomenon that the ink cannot be completely scraped locally on the plate roller, and it is directly transferred to the printing material to form local dirt.
There are six main reasons for unclean scraping:
1.Influence of ink viscosity
Ink viscosity is one of the reasons for the uncleanness. We recommend that you adjust the viscosity of the ink before production proofing. For example, the speed of the pre-start machine is controlled at 150 m / min. Then we recommend that the ink viscosity be controlled at 15 Proof in seconds. In the normal start-up production process, we must pay attention to the control of ink viscosity, the most important thing is whether the viscosity measurement method is standard, which also determines whether the viscosity value is correct. This has a big impact on print quality issues. Viscosity measurement standard: It is recommended to measure directly in the barrel. The 90-degree method measures the viscosity cup vertically. Note that when the first drop of ink flows out of the hole of the viscosity cup, press the stopwatch start button at the same time. Press the stop key at the same time to complete the entire measurement action, start reading and record. In addition, when you see the data, you should pay attention to whether it is consistent with the actual ink status. This requires some experience. The viscosity cup must be clean and no ink adheres to it. The second measurement is from light to dark. The measurement process must be focused. In addition, choosing the right ink is also critical.
2. Performance of benzene-free and ketone-free ink
There is a certain relationship between the scratching and the quality of the ink. But more is that we have to master the performance of benzene-free and ketone-free inks. The benzene-free and ketone-free inks have good printing adaptability as a whole, but also have their disadvantages, such as the low softening point of the resin. Answer) The affinity with the plate roller is better, and the more outstanding is the poor fatigue resistance of the ink as a whole. Common scrapes are not clean in black, blue, and red. For example: When we all do black ink printing, the main component of black is carbon black, and the particles are hard and thick. Usually the amount of black ink itself is not too much, and it is small on the entire printing plate. We recommend that only one third of the ink in the ink tank is needed during printing. It is enough to print on the page, but it is important to pay attention to it. Adding a small amount of new ink can effectively prevent the use of ink for a long time, causing an imbalance between the resin and the pigment, and effectively maintaining the overall printing effect of the ink, which can improve the phenomenon of uncleanness. Before production in the workshop, the filtration of the ink during production is very important. Mastering the performance characteristics of inks is critical for print operators.
3. Plate roller
The cleaning and throwing of the plate roller is very important for scratching. Regardless of the new version or the old version, there is a layer of protective oil on the surface of the plate rollers. This type of oil is better not to drip into the ink when cleaning, which will directly affect the performance of the ink. It is recommended to clean the plate with a solvent before the plate, and then clean it after the machine is installed. Do not use too much solvent. After that, we recommend using 800-1000 grit sandpaper to make a horizontal plate-throwing action. It becomes C-shaped under irradiation, everyone can try it. The detailed work of this link has a critical impact on the uncleanness.
4.Scraper assembly and lower knife angle
For example, the scraper we use on the black color sequence is a hard scraper, which is correct. But we should pay attention to the distance between the scraper and the lining, we can explore it. Our suggestion is that the extension between the scraper and the lining is more suitable at 3mm. Be careful not to have wavy or balanced ends. The lower knife angle is 55-60. It is advisable to use a scraper cylinder to press the scraper first. Usually, we should use 0. 23-0. 3mpa. Excessive pressure will not help to clean the scraper. The friction will only reduce the life of the blade and plate roller. Choosing the right scraper, the quality of the scraper is directly proportional to the price. How to choose a proper scraper is also a topic we should pay attention to. Do n’t choose expensive, just choose the right one.
After the normal proofing production, the first volume speed-up link can be started, which can be manually and appropriately pressurized. This is the captain to operate, this is the process of accumulated experience.
5. Influence of workshop humidity
The relative humidity control of the printing workshop is best within 65%. We recommend that the door of the workshop be closed during production, and the ink state of the ink basin be observed carefully. Solvents that can absorb water are: isopropanol, but do not add too much.
It is not advisable to add too much slow-drying solvent during production. In the benzene-free and ketone-free ink system, butyl ester, propylene glycol methyl ether, and n-propyl ester are slow-drying solvents. If it is recommended not to add slow-drying solvents to black inks, you can mix them with the solvent when necessary And when adding, add while stirring.