The screen printing process looks very simple, a scraper a net. However, it is much more complicated in view of the ink transfer process and the concept of the average person, because the screen printing ink has been rotated during the printing stroke, and the rotating centrifugal force and the scraper simultaneously act on the ink pressure.
General precision silk screens do not consider these issues. Because the theory is always a lot, but practice may only be two or three steps. Many well-made masters may not have studied this issue. From practice to practice itself is also a major path to explore and develop screen printing technology. Talking about the transfer of ink during the screen printing process, we mainly discuss the ink transfer process and the key points affecting the ink transfer. If we change to the goal we are going to achieve in daily printing, it is how to accurately control the line and dot precision and use the most The best parameters to achieve this process.
First of all, the ink is squeezed from the screen printing surface with a squeegee, this problem I think is not also. There are two situations. To begin with, the offset, gravure, and resin platen technologies, including pad printing, are all designed to allow the ink layer to be in close contact with the ink to deliver the ink. Looking back at the ink transfer process of screen printing, we will also find that after the flooding knife is filled with ink in the screen surfing hole, the purpose of our scraping is to make the screen contact with the printing material. The ink at the bottom is glued to the print at the moment of contact with the print. Therefore, the main function of the screen printing doctor blade is to realize the precise line contact between the screen and the printed product, instead of using a large force to squeeze the ink through the screen. This is a theoretical basis for precise control of ink volume.
The reason for this is because the application industry of screen printing is very wide. It says that the ink must be squeezed through the screen in order to get the maximum amount of ink. The most typical is to use the round-head scraper to print the target to be achieved. We demand that the precise control of the amount of ink is not the same. In this article I look at the screen printing with a round blade in the special case.
This article mainly discusses the transfer process of ink and discusses how to precisely control the amount of ink. The ink scraping angle has a great influence on the amount of ink under the screen printing. The best squeegee angle recognized at home and abroad is 75 degrees. The same is true for Satfa. Tianyi Ink Weekly In the course of developing the Jin Dasheng ink series, Tianyi ink has done many experiments to study the interaction between blade angle hardness and ink viscosity. Get a lot of valuable data. Mr. Zhouâ€™s view is that ink must be understood thoroughly in the ink transfer process of screen printing. It is believed that the precise transfer of ink during screen printing is a product of many factors eclecticism. Through experiments, we can understand the interaction between scraper angle, scraper hardness and ink viscosity, and ink cut-off force in the transient process of scraping. Based on this, inks with the best printing power will be made. The author believes that Tianyi's point of view is correct. Ink suppliers should consider that ink parameters are very important sub-systems in the screen printing process and carry out experiments. The inks are viewed from the overall perspective of screen printing. Digression, we are really pleased to see the breakthrough made in domestic high-end inks and high-end screens in recent years.
Tianyi proposed the concept of ink pressure during the squeegee process. I would like to tell you about this concept. Why do we have the same strength and under the premise of the same hardness of the scraper? Why does the same printing speed appear? The printing angle is 60 degrees greater than the 75 degree printing angle. The experiment shows that it is mainly in printing. During the process, the ink at the angle between the doctor blade and the net cloth rotates at a high speed. The high-speed rotation generates centrifugal pressure on the side wall of the doctor blade and the net cloth. In the normal screen printing process, not only a process for letting the scraper closely contact the printed product, but also It also has to fight against the centrifugal pressure formed by the rotation of the ink and to push pressure. The formation area of â€‹â€‹the ink pressure and the pressure distribution model show. Under the same conditions, the ink pressure at the squeegee squeezing line at the squeegee is the larger the squeegee angle, and the ink pressure on the mesh cloth is relatively small, and vice versa. The formation of ink pressure also has a great relationship with ink viscosity. When the viscosity of the ink is moderate, the rotating centrifugal force will be well controlled. This process changes from high-speed rotation to flat-push movement. Therefore, when conducting precise printing, experts recommend using ink with higher viscosity.
After precision stencil printing, a layer of water-based Teflon solution with very low surface tension is often applied. After being dried, it is only one-fifth of a micron thick. It does not affect the screen parameters, but it can make the ink and silk. The friction of the net is minimized. The extremely low surface tension means that the screen printing surface also has a strong oil repellent performance, and well controls the diffusion of the ink along the opening under the mesh. At the same time, the high-viscosity ink and the lubricating mesh surface are used during the high-speed movement of the doctor blade. The form of rotary motion is changed to the maximum, and the ink to be transferred in the mesh and the excess ink on the screen are minimized to interact with each other. In the case of precision printing, the viscosity of the ink is used for precision printing. The impact is generally greater than we think, and high-viscosity inks have a great influence on the consistency of precision lines and precision dot-printing.