(Best Practice in Screen Printing) Companies that use silkscreen as a link in the manufacturing process usually treat it as a project. They want to know where the problem may be and how to overcome it. This habit is very good, if you do not do this, the printer may forget the basic principles, can not control the entire process, here, we will focus on some of the important principles associated with the silk screen variables. In the process of screen printing, the ink may have the greatest impact on the success or failure of printing. It can also be said that the number of ink-related variables faced by the printer has a significant impact on the success or failure of the printing. These variables include viscosity, shear resistance, surface tension, pigment particle size, solvent volatilization rate, and temperature. Among these variables, the printer often ignores the evaporation rate of the solvent in the ink, which determines the drying characteristics of the ink on the screen stencil. If traditional UV-curable inks are used, the volatility is not an important issue, but the focus is on shielding from excessive radiation (from sunlight, fluorescent lights, etc.) to the surrounding environment. Water-based UV inks are best treated as a solvent-based ink system because the evaporation of water and mixed solvents on the screen occurs frequently and it can successfully change the ability to transfer ink. No matter what type of ink you use, a simple but effective principle is to add only a small amount of ink to the screen at a time, but many times to maintain the correct working condition of the ink. In addition to the ink drying associated with the screen stencil, excessive ink on the screen can deflect the screen, changing the height of the off-gaps, and ultimately affecting the separation of the stencil from the substrate. Applying too much ink on a screen stencil is also wasteful, and too much ink that is not used will lose the solvent, resulting in a stencil. The purpose of the squeegee squeegee is to bring the screen stencil into contact with the substrate and allow the ink to seep out of the mesh. The other effects of the squeegee may have a negative impact on the printing process. The squeegee is a force applying device in the printing process. In essence, when the squeegee blows across the screen, a wave of waves is created in the ink layer. This wave is a set of pressure system that rolls on the screen template before the squeegee, and the pressure causes the ink to fill the open mesh and contact the substrate below the stencil. Once the ink contacts the substrate, another set of mechanisms begins to work, the relationship between the surface tension of the ink and the surface energy of the substrate. If the surface energy of the substrate is higher than the surface tension of the ink, the ink will contact the substrate. Once the screen is separated from the substrate, the ink is pulled out of the mesh of the screen and absorbed onto the substrate. Simply put, it is the substrate that is wetted by the ink. It is worth noting that if the surface of the substrate is greasy or the surface energy is very low, the ink cannot wet it, and the transfer of the ink is incomplete or no transfer of the ink can occur at all. If the mesh tension is sufficient to overcome the viscosity of the ink, efficient wetting effects can occur. If the ink film in the mesh is too long after the squeegee is scraped, only part of the ink is transferred to the substrate, and a large amount of ink will remain in the mesh, leading to ink blemishes. But at the right tension, the ink film peels off immediately after the screen moves. Only then can the ink be smoothly transferred from the top of the mesh to the substrate. When selecting and using a squeegee, the parameters to be considered include hardness, flexibility, profile, length, unsupported height, angle, speed, and pressure. For hardness alone, we recommend using a harder squeegee. It performs better than a soft squeegee because it is more stable and more durable. A softer squeegee will absorb more solvent from the ink, causing deformation. However, when the surface of the substrate is not very smooth, it is recommended to use a softer squeegee. If a harder squeegee is used at this time, the contact between the screen stencil and the substrate cannot be guaranteed. If you make the squeegee head sharper, be extra cautious. In general, the angle of the edge of the squeegee provided by the manufacturer is reasonable, and it is better than using any even the most effective squeegee device. The sharpening operation of the squeegee once it is removed from the press is also to be avoided because it creates an unstable and often uneven print edge where the edge of the squeegee will absorb more solvent from the ink. It is advisable to set aside 24 hours before sharpening them. The outline of the image on the screen and template plate can predict the amount of ink passing through each point. The accuracy of the image reproduction depends on the ability of the template to form a gasket-like seal in the image and non-image areas after the squeegee blade is scraped. In addition to the formed emulsion bridge properties between the meshes, the thickness and flatness (Rz) of the stencil also affect the edge accuracy of the printed image. If the stencil is too smooth (very low Rz), the stencil may stick to the substrate, causing the print quality to deteriorate. The geometry of the mesh (number of meshes, line diameter, etc.) determines how much ink passes through the mesh. The stencil thickness affects only the ink film thickness at the edges of the image. If the image is composed of fine mesh lines and dots, the stencil thickness has a considerable influence on the deposition of the ink. But for larger printing areas, the stencil thickness will affect the edges of the image. Mesh tension provides the potential of the entire process. The degree of wire mesh tightening should be within the wire mesh manufacturer's recommendations. Increased tension, reduced peeling time. Reducing the peeling time also reduces the image edge expansion and the image quality is improved. Tension determines the stability of the image. However, the tension is too tight to make the screen too brittle, making the mesh close to or exceeding its elastic limit, resulting in irreversible tension loss. For multicolor work, every screen used in the work should have the same tension, and the tension between the screens should be within 1 N/cm. The strength of the frame is very important, and it should be strong enough to resist the pressure that will be encountered in the tensioned screen or in the printing process without being deformed. A pressure of 20 N/cm should be applied to 1 meter (39 inches) on each side of the frame. It should also be realized that the temperature has a great influence on the mesh tension. When transforming a completely different external environment, it should be time to re-tighten. The purpose of the ink bar is to fill the mesh with ink before the squeegee exerts an action on the ink. The ink bar is basically an inhibiting squeegee. The parameters such as angle, shape, speed, contact or debonding meshes all determine the key factors for the pre-filling of the ink ribbon. The result is that a certain amount of ink is deposited in the mesh. By controlling the amount of prefill, the ink strip directly affects the print drying time. Ink bars are often misunderstood parts of the printing process. Some printers do not even use ink sticks, but allow ink sticking under the squeegee to be added to the next round of scraping. In manual printers, it is desirable that the squeegee be used both as a squeegee and as an ink stick. In manual printing, this requires an experienced printer to skillfully manipulate the squeegee to obtain satisfactory results. For most automatic and semi-automatic machines, when the ink flows through, the ink strip can only limit the amount of ink by simply touching the stencil. Here, the shape of the contact edge is an important factor. The sharp edge coating pre-fills the mesh with a small amount of ink, while the round coating coats the mesh with more ink. The ink strip off height used means that the ink is allowed to flow into the blank area of ​​the mesh itself and virtually all control is abandoned. Each press of the press (even the same make and model) has slightly different printing characteristics. In addition to the finest applications, these variables are not related to each other. In printing, 80% of all production problems are caused by improper settings. Multi-color printing on the same machine, or several machines installed on a printing line, the equipment characteristics must ideally be the same. Diversity will lead to changes in image size and ink deposition. Manually obtaining materials to support product operations is a related printing equipment concept. Be sure to collect everything you need before starting a printing process. This leads to the least preparation time and the smallest amount of waste. Finally, note that continuous operation is the most effective printing method. Shutdown stencils change the coherence of the ink flow, and if not carefully cleaned, will shorten the stencil life and reduce the printing boundary. If possible, to avoid touching the printed edge of the stencil at all, prevent the squeegee wear (which may cause a continuous ink twist) is another way to keep the printing running. Provides low squeegee pressure to reduce wear and tear. Other ideas in addition to these aspects, also need to determine the substrate is clean and pollution-free, but also to ensure a suitable printing environment, can control the temperature and humidity. By taking these steps and working hard to reduce the many variable factors mentioned earlier, the amount of waste products will be reduced and the total quality of print products will increase.