Before we start to discuss with everyone how to control the ink layer, we should first review some of the problems that we have encountered in printing in the past: 1. The color of the color block is printed in dark and light. 2. The dots are expanded during screen printing (with moire). 3. The difference in color during batch printing. When these problems are serious, it will affect the production schedule and batch returns, which brings inconvenience to the normalization of our work. So how to control and prevent these problems is worthy of discussion by our screen printing workers. The following are the variables that we should understand in printing. 1. Analyze the theoretical ink penetration: There are two methods for analyzing the screen ink penetration, one is to calculate the theoretical screen ink penetration, and the other is the actual printing ink penetration. The following formula is used to calculate the theoretical ink penetration: Opening rate: L The thickness of the wire mesh is: D The theoretical ink penetration is: M = L × D ÷ 100% The above formula is only a theoretical method for calculating the screen ink penetration. Once it is applied to practical printing, the data will change, but it is proportional. We look at the following factors: 1. The mesh number of the wire mesh (directly determine the hole width and the opening rate). The higher the mesh number of the screen, the smaller the hole width, and the opening ratio decreases accordingly. For example, the opening width of the 355 mesh screen is 31μm, the opening ratio is 26%, and the theoretical ink penetration is 14.3cm³ / m². The 305-mesh wire mesh has a hole width of 45μm and an opening rate of 35%. The theoretical ink penetration is 16.3cm³ / m². 2. The wire diameter of the wire mesh (which directly affects the mesh thickness, opening rate and mesh size). Refers to the diameter of the unwoven wire diameter. The wire diameter after weaving will become oval. Will affect the size of the mesh. The wire mesh diameter of the same mesh is different, which will also affect the opening size and opening ratio. For example: 305 mesh wire diameter 31um opening rate is 35%, hole width is 49um, mesh thickness is 49um, theoretical ink penetration is 17.2cm³ / m². The opening rate of the 305 mesh screen diameter 34um is 29.6%, the hole width is 45um, the mesh thickness is 55um, and the theoretical ink penetration is 16.3cm³ / m². 305 mesh wire diameter 40um opening rate is 20.1%, hole width is 37um, mesh thickness is 65um The theoretical ink penetration is 13cm³ / m². 3. The thickness of the screen (directly affecting the ink layer). We can use the thickness gauge to detect the screen thickness of the stretched screen. Since the wire mesh produced by each manufacturer has its own weaving process, the warp and weft have different degrees of bending. The greater the degree of bending, the wire mesh will become thinner, and vice versa. In the process of stretching the net, due to the influence of external forces, the wire diameter is stretched, which ultimately affects the thickness of the wire mesh. 4. The hole width of the screen (directly affects the amount of ink). We know that the wider the mesh, the greater the amount of ink underneath. In the process of stretching the web, the higher the tension, the lower the mesh number, and the wider the mesh, the larger the ink penetration. 5. The opening rate of the screen (directly affect the amount of ink). The so-called porosity refers to the ratio of white permeable area to the total area per unit area of ​​the screen. For example, a screen with an opening rate of 35%, the ink penetrating part is 35%, and the part that does not penetrate through the silk is 65%. The higher the opening rate, the larger the ink volume. Calculation formula: The hole width is: K The mesh is: M Inch units are: Y Opening rate: L = K × M ÷ Y² × 100% 6. The pressure plane of the wire mesh (directly affects the mesh thickness and hole width). Imported wire meshes above 355 mesh are mostly flattened. The flattened wire mesh obviously becomes thinner and the mesh becomes smaller. When the flattened silk screen stretches the net, let's look at the following examples: when the flattening plane is stretched toward the scraping surface, the ink can be saved by 10% ~ 15%, and if the flattened plane is stretched toward the substrate, the net can be saved by 15% ~ 25%. 1. The tension of the screen (affects the size of the openings, the number of screens, the wire diameter, and the thickness of the screen). During the stretching process of the wire mesh, as the tension increases, the technical parameters of the wire mesh itself will change accordingly. Firstly, the mesh number of the wire mesh is affected. The higher the tension, the greater the mesh number decreases (until the wire mesh is plastically deformed). Next, it will affect the hole width of the wire mesh, the mesh hole will become larger, the wire diameter will become thinner, and the mesh cloth will become thinner, these factors will eventually lead to changes in the amount of ink. 2. The thickness of the film layer (decide the amount of ink). If we use photoresist to make the screen, we also need to consider the solid content of the photoresist itself. After the photoresist with low solid content will make the film, the film will be volatile and the film will become thinner. Therefore, we can only use the thickness gauge to detect the overall thickness of the screen. 3. Ink type (indirectly affects ink layer thickness). We know that the solvent-based ink will evaporate after printing, and the ink layer will eventually become thinner. After the photo-curable ink is printed, the resin is cured immediately after being irradiated with ultraviolet rays, so the ink layer remains unchanged. 4. The viscosity of the ink (indirectly affects the thickness of the ink layer). The lower the viscosity of the ink in the printing process, the thicker the ink layer, because the ink itself contains less solvent, on the contrary the thinner. 5. The hardness of the squeegee (indirectly affects the thickness of the ink layer). In the printing process, the higher the hardness of the squeegee, the less likely it is to deform, and the lower the amount of ink, and the larger the opposite. 6. The tolerance of the scraper (directly affects the amount of ink). If the blade of the scraper is at a right angle, the amount of ink discharged is small. The amount of ink is large if it is obtuse. 7. Angle of scraper. (Indirectly affects the thickness of the ink layer). During printing, the smaller the angle between the doctor blade and the screen, the greater the ink drop, because the doctor blade and the screen are in surface contact. The opposite is small. 8. The pressure of the scraper (directly affects the amount of ink). During printing, the greater the pressure on the doctor blade, the smaller the ink drop, because the ink has been driven away before it is completely squeezed out of the mesh. The opposite is small. 9. The pressure of the ink return knife (direct ink volume). The greater the pressure applied to the ink return knife, the greater the ink drop, because a small amount of ink has been pushed out of the mesh by the ink return knife before being scraped. The opposite is small. 10. The speed of scraping (indirectly affecting the thickness of the ink layer). The faster the printing speed, the smaller the ink drop, because when the ink has not completely filled the mesh, the ink has been squeezed out, resulting in intermittent ink supply. 11. Printing materials. (Directly affect the thickness of the ink layer). The flatness of the substrate surface will also affect the thickness of the ink layer, and the rough surface ink will penetrate (such as woven fabric, leather, wood). The opposite is bigger. 12. Printing environment (indirectly affecting the thickness of the ink layer). One problem that we have always overlooked is the change in temperature and humidity in the printing workshop environment. If the temperature in the printing environment changes too much, it will affect the ink itself (such as the viscosity and fluidity of the ink). 3. How to calculate the thickness of the ink layer? Through the above discussion, we know that if a certain link changes during the printing process, it will eventually lead to inconsistent ink volume, so how should we calculate the thickness of the ink layer? One method is to weigh the weight of the wet ink. First, try to control each link in the printing to remain unchanged. After printing, weigh the weight of the substrate, and then subtract the original weight of the substrate. The data obtained is the wet ink. For weight, another method is to measure the thickness of the ink layer, use a thickness gauge to measure the thickness of the substrate after ink coating, and then subtract the original thickness of the substrate to obtain the thickness of the ink layer. 4. How to control the thickness of the ink layer? How to control the thickness of the ink layer has become a problem faced by screen printing workers. The first thing we need to do is to use the existing measurement equipment to ensure the accuracy and objectivity of the measured data; qualified factories can use automatic The coating machine is used to complete the gluing process to ensure the thickness of the adhesive layer. The next thing to do is to ensure that every link in plate making and printing is kept as constant as possible. Each printing parameter should be well recorded to provide ideal data for finding the appropriate ink layer thickness. Beach Rackets ,Beach Tennis Rackets,Beach Tennis Paddles,Beach Racket Ball Ningbo Sno Stationery & Sports Articles Co., Ltd. , https://www.snotoy.com
2. Actual printing ink penetration: