The YAG laser-engraving anilox roll seems to be best suited for UV ink systems. In the test and production process, when UV ink was used, the images obtained after printing with 1400 lpi anilox roll engraved with YAG laser were very clear, clean, and consistent. The UV ink itself is not easily "dried" in a cylindrical ink-receiving hole.
When printing with solvent-based inks, the results of the YAG laser-engraving anilox roll vary from case to case. The comparison of the 1400 lpi YAG laser engraving anilox roller with the same BCM value and the 800 lpi CO2 laser engraving anilox roller will show that the printing density of the YAG laser engraving anilox roller has decreased. This is due to the YAG laser engraving. The surface area of the anilox roller is relatively large (that is to say, the number of network walls is relatively large). Regardless of how thin these network walls are, they always have a certain amount of ink attached, so the ink scraped by the squeegee is more.
However, when the YAG laser-engraved anilox roller was used for printing, the dot shape was more perfect, and the dot gain was lower than that of the CO2 laser-engraving anilox roller with the same ink-transfer amount (BCM value). We know that low ink density means that the thickness of ink ink film is relatively thin, so the dot gain rate can be reduced. 800 lpi CO2 laser engraving anilox roller To achieve the same printing effect, it may be necessary to use an anilox roller with lower ink transfer. However, all flexo printers want to be able to achieve the maximum color density with the thinnest ink layer.
In order to objectively and comprehensively evaluate the advantages of YAG laser engraving technology, I am afraid that more and more in-depth research and testing are needed. However, we believe that the outlook is bright and beautiful. When using solvent-based ink or UV ink printing, YAG laser engraving anilox roller can indeed reduce the dot expansion and "paste", the natural transition of a large area of high light areas, the effect has been greatly improved and improved. On the contrary, when using a water-based ink system, YAG laser engraving anilox roller indeed has certain problems. Because these water-based inks can easily cause the clogging of the anilox roller ink holes over time, the YAG laser-engraved cylindrical ink holes are relatively deep, and ink release and cleaning may not be clean and thorough. This type of plugging problem is prone to occur. The CO2 laser engraved ink hole, because the shape of the ink hole is bowl-shaped, easier to clean, so the effect of water-based ink printing is better, as long as the ratio between the depth and width is appropriate.
For those users who have used YAG lasers to engrave anilox rollers and wish to print with water-based inks, an anilox roller with diagonally shaped ink holes can be used. This type of ink hole is easier to clean than a sealed ink hole. However, the 1500 lpi diagonal YAG laser has a very thin engraved anilox roll wall and its service life is relatively short. This is a problem. This issue is still being tested and studied, and it may be resolved soon.
V. Other Problems As mentioned earlier, YAG lasers cause most of the ceramic layer to be evaporated by ablation, leaving few ceramic layers (less than CO2 laser technology). In theory, this gives the squeegee the opportunity to come into contact with the original ceramic coating, rather than the second-coat ceramic layer on the wall (as is the case with the CO2 laser-engraved anilox roller). Are these original surface coatings harder, smoother, and longer lasting? This is hard to say, but if the conditions in the pressroom are not good enough to cause scratches, then any anilox roller will be scratched or damaged. However, there is currently not enough evidence to conclude that the performance of the YAG laser is therefore superior to the CO2 laser.
Another problem is "splattering." Some printing presses that use UV inks have such problems during the printing process: there are small dark stripes in the field. This is because the viscosity of the UV ink is relatively high, so that the ink continuously accumulates on the bottom of the squeegee blade, and the squeegee can only discharge these accumulated inks sporadically and discretely, and therefore, streaks are produced. The 300-angle CO2 laser-engraved anilox roller has found some solutions to this problem: engraving additional channels on the anilox roller and changing the alignment of the pattern of ink holes in the machine direction.
The third issue that needs to be considered is the thickness of the ink layer. The thickness of the ink layer is one of the main factors that determine the dot gain. The higher the number of screen lines, the more easily the size and spacing of ink droplets transferred to the surface of the printing plate. The YAG laser-engraving anilox roller with a high number of lines allows the transferred ink droplets to be slightly larger, so the printed ink layer is smoother. This allows a very high number of plate screens to be added, as outlets remain independent, stable and tidy.
VI. Advantages and Disadvantages of YAG Laser Engraving Technology
This article has already mentioned some advantages of the new YAG laser engraving technology: strong beam, deeper ink engraved hole, better ink release performance, higher screen lines, and higher ink transfer volume. And the thickness of the wall is thinner. Thanks to these advantages, YAG laser engraving technology has emerged as an exciting new method. The YAG laser beam is very strong. When focusing on a small ink hole, the energy of the laser is always kept constant. Therefore, it can combine the high mesh number with the perfect shape, thin mesh wall, and high ink transfer amount of ink. Together, the advantages are even more prominent.
Some inadequacies of the YAG laser engraving technology also have to say. For the starter, the life of the lamp is limited and the stability of the YAG laser beam is also poor, so the predictability of the YAG laser engraving technology is not so good. During use, the intensity of the lamp gradually decreases, and a certain degree of change occurs during the engraving process. Research shows that the consistency of the amount of ink transferred by the YAG laser engraving anilox roller is not as good as the CO2 laser engraving anilox roller.
If the power of the YAG laser is relatively low, in order to obtain a full-shape ink-receiving hole when engraving a low-line number of anilox rolls, multiple ablation operations are required. When one row of ink holes is ablated by the required number of times, the laser beam is automatically moved to the next row of ink holes. This may cause lines on the surface of the anilox roll. Under such conditions, some of the anilox roller's ink holes can be ablated at one time, which does not necessarily require so many ablation times, such as an anilox roller above 1000 lpi. 800 lpi and 900 lpi anilox can also be ablated at one time, however, the thickness of the web wall is larger than that of the two ablation.
Finally, when engraving an anilox roller with a very high number of screens, the quality requirements for the ceramic coating are very strict. If the ceramic coating has too many holes, the surface gap may be larger than the ink hole itself. Because the YAG laser evaporates most of the ceramic coating, there is no excess ceramic coating to fill the hole.
VII. Pros and Cons of CO2 Laser Engraving Technology
Initially, the purpose of using YAG laser engraving technology was to catch up with the engraving speed of the CO2 laser engraving system, because the CO2 laser engraving technology uses a stable, segmented, high power laser beam that remains constant throughout the engraving process. Predictable, so its repeatability and predictability are very high. Moreover, if the engraving is correct and reasonable, the ink releasing performance of the bowl-shaped ink hole formed after the CO2 laser engraving is very good, and the cleaning is also very convenient.
The disadvantage of CO2 laser engraving technology is that it is not very suitable for high-line number anilox roller engraving. Once the number of network lines exceeds 1000 lpi, it is difficult to ensure sufficient color intensity. In this respect, YAG laser engraving technology is superior to it. Even with more than 1000 lpi of screen lines, the YAG laser-engraved anilox roller can release ink and transfer ink. In addition, the YAG laser-engraved ink-receiving holes may also occupy certain advantages in terms of smoothness.
VIII. Conclusions Some of the viewpoints described in this article are for your reference only, mainly to tell you about the issues people are currently studying and considering. YAG laser engraving technology is indeed very exciting, and, as the technology matures, it will certainly be further improved and improved to obtain higher and better results. Currently, CO2 laser and YAG laser engraving technology have their own strengths and advantages in specific application fields. If you ask which method is better, the kind of engraving method that can get the best printing effect is certainly the best method.