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Common mistakes and countermeasures in the process of screen printing
Have you ever used the ink taken out of the ink tank to print directly? Have you ever repeatedly wiped off the ink accumulated on the screen? Have you ever put inappropriate pressure on the squeegee Experience? If you answer all three questions in the affirmative, then you have committed the three taboos in the screen printing process. If you can spend a little thought on the blending of inks, while using a re-tensionable screen to control the angle and speed of the squeegee, you can easily avoid most of the problems encountered in the screen printing process.
Each of the problems mentioned above will directly affect the quality, production efficiency and credibility of printing companies. This article will discuss the blending of inks in detail.
Almost all plastisol-based inks are concentrated liquids when they leave the factory, and the degree of concentration varies depending on the manufacturer, color, and type, and some are even super concentrated. Here we will focus on the plastisol ink, because most textile printing uses this ink. Simply put, ink is composed of three main components: PVC (polyvinyl chloride plastic), pigments (color) and plasticizers (or other additives).
PVC is an adhesive that makes solid pigments adhere to the surface of textile materials after being melted. It is a dispersion resin with extremely fine particles, a bit like white sugar. When it is mixed with plasticizers or other types of additives (except for pigments), it becomes a liquid colorless and transparent substance, which can form a very thin film after coating. Stir it, you will find that it is easier to stir than the ink with Yanke, and it is easier to leave the squeegee, the viscosity is very different, it is more suitable for printing than the ink with pigment, and easier to print .
Pigment produces color. It is ground into fine particles and mixed with PVC and other additives. The ratio of it mixed with transparent PVC and other additives determines the transparency and opacity of the color. The pigment concentration of screen printing ink is higher than that of four-color printing ink. Even if the same type of ink is produced by different manufacturers, the pigment percentage is different, and the viscosity is also the same, so their printability And the color density also has a certain difference accordingly.
Let's do a simple experiment for comparison: a piece of printed matter is printed with high-saturation colors, such as blue or red, with ink directly taken out of the container. The other one is to add the same amount of transparent additives to the same ink, stir evenly for printing. You will find that for most types of inks, the colors of the two prints are the same, there is no big difference. The mixture of 50% pigment ink and 50% transparent additive can fully meet the needs of the operation, and makes the printing process easier and easier, and the cost is also reduced a lot. Now do another experiment, this time adding two parts of transparent additives to one part of the original ink. At this time, the pigment ink only accounts for 33% of the total. It can be found that the printability of this mixture has been further improved, and for most manufacturers' products, the color is still acceptable. When configuring the ink, you must test the inks of different manufacturers, their types and hue, because some inks will become lighter when mixed with 50% additives, while some will not change at all.
The additives and plasticizers used by manufacturers to formulate inks are the most important factors that cause differences in ink quality. Among them, plasticizers are the most important ingredient, and in most cases are also called reducing agents.
Adding a small amount of reducing agent to the ink will reduce the viscosity of the ink, thereby improving the printability of the ink. Generally, no reducing agent is added during four-color printing. In the screen printing process, the formation of ink dots is determined by the size of the screen mesh. If the mesh leaves the surface of the substrate, the ink dots will be deformed and the printed image will become blurred.
The reducing agent in the container is as clear and transparent as water. If you scoop up a spoonful, it will feel a bit like clean oil. When using it, strictly follow the manufacturer's instructions. If you add too much reducing agent, then no matter how much desiccant you add, how slow the printing speed, how long the time through the dryer, the ink is difficult to combine with textiles. So be cautious when adding reducing agent.
The reducing agent produced by some companies is curable. It is a mixture of reducing agent mixed with PVC and other additives in proportion, which can play a role in drying and curing. Appropriate use of reducing agent can bring benefits to the printing process, but in the actual production process, people often do not follow the manufacturer's instructions, abuse the amount of reducing agent, and evaluate whether the application is appropriate through vision and perception. Of course this approach is very harmful.
If the correct dosage is used, the printed image will either have a greasy feeling or a faded feeling. In this case, users often complain about the poor quality of the product and ignore that they use the wrong amount of additives when preparing the ink. Sometimes people think that reducing agent and diluent are the same. This concept leads to another misunderstanding.
There is a big difference between reducing agent and diluent. Among them, only reducing agent can reduce the viscosity of ink, while diluent will not affect the viscosity of ink.
If you do not add reducing agent when printing, you will find that the printed product has obvious ink accumulation, and even orange peel, the surface of the printed product is very uneven, and some small pits appear. And when the screen is lifted, part of the ink will be removed from the printing material. In the same printing, just adding an appropriate amount of reducing agent to the ink, it is found that the phenomenon of ink accumulation is significantly reduced, and the ink will not stick when the screen is lifted.
Less pigment means less dryness and less ink accumulation, and reducing agent can further improve the occurrence of ink accumulation.
What to pay attention to when using the screen printing machine