Some misunderstandings in the application of the h

Some misunderstandings in the application of flexographic materials

in recent years, due to the increasing demand for environmental protection printing, especially the environmental protection printing of food and pharmaceutical packaging has entered the stage of legislation. Flexographic printing, known as "green printing", has attracted more and more attention

due to the characteristics of flexographic printing in the production process and product environmental protection, it is increasingly adopted by the majority of food packaging, drug packaging and other manufacturers, otherwise the material may degrade and change color. So many manufacturers will ask such a question: how to improve the printing quality of flexo? How to make flexo printing comparable to offset printing and gravure printing? However, there are many factors that affect flexographic printing, which also makes some manufacturers go into such misunderstandings

flexographic printing should be practical and have good printing quality, we must consider many aspects. The first point I want to talk about is plate material. The fineness and compatibility of plate making are the primary factors affecting the quality of flexographic printing, which requires good plates. Now we have a digital version, and the accuracy of plate making has been greatly improved. Now Kodak's plates can meet the reproduction requirements of different levels from 95% to 2%; The traditional version can also improve the accuracy of the output of more than 150lpi. Of course, prepress processing is also very important and cannot be ignored. For example, when designing patterns, we should try our best to avoid some highlights, because too small highlights will be worn in a very short time, resulting in white defects. Therefore, excellent prepress processing is the mother of excellent printing quality. Only on the premise of ensuring the correct prepress processing, so it is often listed as a plastic machine, and high-quality plates can better play its role

second, the grade of ceramic roller is also an important factor that directly affects the quality of flexographic printing. Of course, many manufacturers can make ceramic corrugated rollers, and it is not difficult to make oneortwo, but not every factory can do it stably. There are only threeorfour companies in the world that can make every corrugated roller stable and perfect

so what kind of ceramic roller is high-quality? The first is the processing capacity of the geometric tolerance (out of roundness) of the roll body, which can not be done well by manufacturers including steel wire, iron wire, thin wire, etc. Many manufacturers say: we can also make corrugated rollers, which are cheaper. So many users fall into such a misunderstanding: they think that the surface is like a ceramic roller and they think it's OK. But in fact, do they really test whether its out of roundness meets the requirements? If you can't meet the requirements, what conditions are there to talk about high-quality printing effect? Let alone talk about what is comparable to offset printing and gravure printing

secondly, the anti-corrosion treatment of the roll body is also very important, because the water-based ink is alkaline and corrosive. Some ceramic rollers are well processed, but their anti-corrosion ability cannot meet the requirements, so they are not high-quality brands. Anticorrosion not only requires good treatment of the substrate, but also requires high density in spraying. Then the quality of ceramic materials is the key. Cheap and inferior ceramic materials often fail to meet the requirements, so high-quality products cannot be printed

moreover, the parameters that really affect the printing quality are the number of lines and ink load of the ceramic roller. Many people know that the higher the number of lines, the better the match with high-quality printing, but the number of high lines means that the ink volume is not enough, so it cannot meet the performance of rich printing colors. Therefore, the high-quality flexographic printing can be truly matched by the high-line number and large amount of ink roller, which is indispensable. However, not every manufacturer can achieve high-speed roll and large ink volume. At least cheap and low-grade corrugated rollers can't be done. Manufacturers who use low-grade ceramic rollers have entered this misunderstanding, thinking that corrugated rollers are not very important! If you want to have high-quality printing effect, you must get out of the misunderstanding and really pay attention to the quality of the corrugated roller and its important role in printing. Then talk about high-quality printing effect, and then talk about comparable offset printing and gravure printing

the third point is about the selection of scraper. Many manufacturers think that the metal scraper will hurt the ceramic roller, which is also a misunderstanding. Ceramics are so hard, how can they be scratched so easily? If it was not knocked artificially, it would not be damaged! Scraping the ink of ceramic roller is like scraping the ink of gravure printing. Scraping the excess ink is the guarantee of high-quality printing, so we should choose the metal scraper first. Of course, excellent scrapers should have good elasticity, high precision, and some should have anti-corrosion ability. For example, the gold medal scrapers of CBG in Italy have outstanding performance in flexo printing, which can fully meet the requirements

Yan Zhixin

reprinted from: PRINT world - issue 10, 2006