Large-format screen making skills of the screen production articles
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The absolute size of large format screens is a major step in making large format screens – mesh preparation, coating, exposure and recycling – and is also a major challenge. However, we now use multiple solutions to simplify the process of making screens. For example, manual screen making has been replaced by automated equipment in many factories, and screen coating has also been replaced by automatic coaters. Let's discuss each step and introduce some of the techniques and tools that can be used to simplify the production of large format screen plates.
Wire mesh preparation
Polyester mesh is a precision synthetic fiber. This material has excellent barrier properties and moisture resistance, which is why it is used in soda bottles and film packaging. To be precise, it is an inert plastic product that is not easily bonded.
Direct-coating emulsions are somewhat like water-based coatings. These emulsions are not easily attached to plastics and have poor adhesion properties. To produce a high quality screen with a long print life, the screen must be properly prepared so that the emulsion sticks well to the screen. Good adhesion is extremely important when using abrasive or water based inks, such as printing on glass or textiles. It is also important that some areas of the image are covered or blocked by tape and are uncovered in the next stage of printing, which avoids damage to the screen.
The screen must be cleaned to remove oil or contaminants, which prevents the emulsion from wetting the surface of the screen, and the fibers also require wetting agent treatment. This can increase the level of surface tension, or the energy of the surface of the polyester mesh, to an acceptable level so that the emulsion adheres to it. This principle is very familiar to printers that print on low-energy plastics, as is the case with polyethylene. These substrates require surface treatment to achieve a certain level of surface tension for optimum ink adhesion. A screen that has undergone a good degreasing operation and pretreatment will form a uniform, complete water film after rinsing. When the adhesion of the screen is improved, the exposure latitude and resolution can reach the highest value.
Glue
In order to achieve a stable effect, we highly recommend the use of an automatic screen coater on a large format screen printer. It is impossible to ensure a uniform coating thickness on a screen of this size by hand coating techniques. If your arm is not long enough to balance the weight of the entire wide coating tank, it is almost impossible to hand-coat a large-format screen.
When sizing, an emulsion with a high solid content should be used. This avoids shrinkage during the drying process and helps you produce high quality stencils using simple coating techniques. Today's coaters also have built-in drying units that perform exceptionally well when using large mesh screens with high mesh counts. Screens with a medium to small number of meshes will use a relatively wet emulsion to dry faster and more efficiently on the coater.
Dry
Screen drying is usually carried out in a non-polluting environment in the isolation zone and is carried out where there is a safety light. Warm and dry 100°F The hot air around (40 ° C) can be freely circulated in the drying zone to remove moisture.
Photopolymer emulsions are less affected by residual moisture and high temperatures during drying and storage. They can be exposed smoothly without being completely dry. However, diazo and dual-cure emulsions must be dried before exposure and exposed to moisture below 4%. You can use a contact gauge to accurately measure the amount of water remaining in the emulsion.
Exposure
Technological advances in the field of stencil making have challenged traditional large format imagesetters and other similar methods in terms of cost and efficiency. The computer direct screen imaging system brings efficiency to the digitization process of the screen printing plate, the film is cancelled, the exposure process and the screen processing process are also simplified, and the original large format vacuum plate printing machine is no longer needed. Finally, the time spent repairing the pinholes on the plates was greatly reduced, as there was no longer any film or glass surface to attract dust.
Although large format inkjet printers differ from computer direct screen systems, their output quality is much better for printers that often have to wait for other company films. Many screen printers use large format inkjet printers to produce in-house. Oversized positive film.
The projection exposure unit greatly reduces the cost of the film. For a photo used to make a large-format screen version, if the magnification is 10 times, the film size is only 1% of the final product. A special emulsion controls the exposure time within one minute, since the vacuum printer is not required, so the screen processing is simplified again.
You don't have to think about how you expose your plate. The most important thing is to make the exposure time long enough to ensure that the emulsion is fully cured and produces a durable, chemically resistant and scratch resistant, good adhesion. Sex printing plate. A color conversion exposure calculator was used to determine the correct exposure time for the diazo, double-cure emulsion. This method, as the last point of the color conversion process, shows the correct exposure time. For example, yellow diazonium is bleached during exposure, which changes the color of the exposed stencil. Usually the color changes from green to blue or from brown to purple.
One tool for judging the exposure value is to use a 21-stage gray scale exposure calculator, which can be used in photopolymerizable emulsions and diazo and double-cure emulsions. The ideal exposure depends on the time required to cure the 7-level grayscale after the screen is made.
Exposure is a major issue when exposing large format templates. In order to maximize the exposure latitude when exposing a large format screen, the most important thing is to choose a high resolution emulsion to improve the coating process, reduce the uneven thickness of the coating layer and pass the screen properly. Ground pretreatment improves the adhesion of the screen.
Developing
In order to achieve the best resolution, it is necessary to spray and develop on both sides of the screen with a high-pressure, evenly distributed developer. This is easy to do on small screen plates, but it is difficult on large format screen plates. Because it has certain requirements for the process and space. An effective solution is to use an automatic cleaning device that can also be developed. This requires less space and does not require design, and there are nozzles in the development tower. The best manual option is to use a pressure water gun with a minimum speed of 1000 psi with a fan spray of 3-5 gallons per minute.
Recycling
Manual cleaning of large format screens requires workers to be particularly focused and use the tools correctly to ensure work efficiency and safety. The tools used mainly consist of a brush with a long handle that can reach the far corner of the screen, as well as protective clothing – glasses, gloves, boots, etc. A separate brush is required for each step of cleaning to avoid cross-contamination between chemical containers. Please don't underestimate the importance of a good pressure water gun. Buy one of the biggest and best cleaners you can afford, it won't let you down.
Automatic screen recycling equipment can do a lot of difficult work and can reduce the possibility of workers being harmed by chemicals. Combined and online equipment can systematically remove oil from the screen, and ghost removal is still a problem because the machine is not fully operational. So even if you are using an automated system, you still have a lot of opportunities to clean yourself.
On a large screen printing machine
The emergence of large-format screen screens is closely related to the pursuit of larger and better images on different substrates. Only by constantly innovating in materials and technology can it be possible to ensure a prosperous career and ensure that screen printing is always at the center of large-format imaging.