Large-format screen-making techniques

- Mar 22, 2018 -

Large-format screen-making techniques

The appearance of large-format silk screens on large screen printers is a quest for printing larger and better images on different substrates. Only continuous innovation in materials and technology can ensure that screen printing is always at the center of large-format imaging. Manual wire mesh production has been replaced by automation equipment in many factories. Similarly, screen coating has also been replaced by automatic coating machines. This article will introduce the main steps for the production of large-format screens—mesh preparation, sizing, drying, exposure, development and recycling.

 

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1. screen mesh preparation

Polyester mesh is a sophisticated design of synthetic fibers. This material has excellent barrier properties and moisture resistance properties. It is a non-sticky, inert plastic product. Direct-coated emulsions are somewhat like water-based coatings. These emulsions are not easily adhered to plastics and have poor adhesive properties. To produce high-quality screens with a long print life, the screen mesh must be properly prepared so that the emulsion adheres well to the screen mesh. Good adhesion is of great importance when using abrasive or aqueous inks, such as printing on glass or textiles. Some areas of a color image are covered or blocked with tape, and then opened again in the next stage of printing, which can avoid the damage of the screen. The screen must be cleaned to remove oil or contaminants. This prevents the emulsion from wetting the surface of the screen. The fibers also require wetting agents. 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 commonly used for printing plants that print on low-energy plastics, such as printing on polyethylene. These substrates require surface treatment to achieve a certain level of surface tension for optimal ink adhesion. A screen mesh that has been well degreasing and pretreated will form a uniform, uniform film of water after rinsing. When the tackiness of the screen is improved, both the exposure latitude and the resolution can reach the highest value.

 

2. glue

In order to achieve a stable effect, an automatic screen coater on a large-format screen printer is recommended. Automation equipment in wire mesh workshops Large-format screen printers cannot be accurately coated by hand, the arms are not long enough, and the weight of the entire wide-width coating bath is also balanced, for large-format filaments. Hand-coating nets is almost impossible. The automated equipment guarantees a uniform and stable emulsion coating. When using high-mesh high-volume screens for sizing, high solids emulsions should be used. This avoids shrinkage during the drying process. The coating machine now also has a built-in drying device. Mesh screens with medium to low mesh counts should use moisturized emulsions to dry faster and more efficiently on the coater.

 

3. drying

Screen drying is usually performed in a non-contaminating environment within the isolation zone and is carried out in areas where there is exposure to a safe light. Warm and dry hot air of about 100°F (40°C) can be circulated freely in the drying zone to remove moisture. Photopolymer emulsions are not affected by residual moisture and high temperatures during drying and storage. They can be successfully exposed without being fully dried. However, diazo- and dual-cure emulsions must be dried before exposure and exposed with a water content of less than 4%. A contact gauge can be used to accurately measure the residual moisture content in the emulsion.

 

4. 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 digital process of making screen printing plates, the film is eliminated, the exposure process and the screen processing process are also simplified, and the large-format vacuum printing machine is no longer needed. The time to repair the pinhole on the plate is also greatly shortened because there is no more film or glass surface to attract dust. The digital template making computer direct-manufacture screen-screening system eliminates the film, reduces operating costs, simplifies prepress processing and reduces the appearance of pinholes. Many screen printing plants use large-format inkjet printers to produce oversized positive image films at the factory. The inkjet positive image film wide format ink jet printer provides an economical choice for laser imagesetters and direct screen imaging CTS systems for positive film production. The projection exposure unit greatly reduces film costs. For a photograph used to make a large-format silk screen, if the magnification is 10 times, the size of the film is only 1% of the final product. A special emulsion controls the exposure time within one minute because no vacuum squeegee is required, so screen processing is again simplified. Projection exposure equipment can save film cost, exposure time, and manpower needed to process screens, but it is important to ensure that the exposure time is long enough to ensure that the emulsion cures completely and to produce a chemical that resists chemical attack and scratches and has good adhesion Fitted durability plate. A color conversion exposure calculator was used to determine the correct exposure time for diazo, dual-cure emulsions. This method handles the correct exposure time as a color conversion. Usually the color changes from green to blue or from brown to purple. One tool for judging the exposure value is the use of a 21-step grayscale exposure calculator, which can be used for light-sensitive polymeric emulsions and diazo and dual-cure emulsions. The ideal exposure depends on the amount of time it takes to post-cure the 7 shades of gray in the screen. Exposure is a major problem when you are exposing large format templates. In order to maximize the exposure latitude when exposing large-format screens, the most important thing is to choose an emulsion that supports high resolution, perfect the coating process, reduce the uneven thickness of the coating layer, and pass through the screen properly. Ground pretreatment improves screen adhesion.

 

5. development

In order to achieve the best resolution, spray development must be performed on both sides of the screen with a high-pressure, uniformly-distributed developer. This is easy to do on small screen printing plates, but it is difficult on large format screen printing plates. Because it has certain requirements on the processing process and space. The effective solution is to use automatic, developable cleaning equipment. This requires less space and does not require design. There is a spray head in the development tower. The best manual option is to use a pressure gun with a minimum speed of 1000 psi and a fan sprayer with a flow rate of 3 to 5 gallons per minute.

 

6. recycling

Manually cleaning large-format screens requires workers to focus their attention particularly on the use of tools, so as to ensure work efficiency and safety. The tools used mainly include a brush with a long handle, which can reach the far corner of the screen, and protective clothing - glasses, gloves, boots and so on. Each step of cleaning requires the use of a separate brush to avoid cross-contamination between chemical containers. Prepare a good pressure gun and a biggest and best cleaner. Automatic screen recycling equipment can do many difficult jobs and can reduce the possibility of workers being harmed by chemical agents. Combined and on-line equipment can systematically remove oil from screens. This type of machine cannot fully remove ghosting and must be cleaned by hand.

 

Choose the suitable and high quality meshes

The printing plate is most important for screen printing, and the screen mesh is the core of the screen printing plate. No matter how good the frame is, if the mesh is not good or suitable, it will seriously affect the printing effect and customer experience. Wuxi Jinfeng Silkscreen Mesh Manufacturing Co., Ltd. specializing in the production of high quality screen mesh and filter mesh, with more than 20 years of production experience, the products throughout the country’s major mining companies and overseas. And get the praise from all the clients.

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WUXI JINFENG SILKSCREEN MESH MANUFACTURING CO., LTD.

Since 1996, as professional we manufacture high quality meshes at best price!
Address: Jinxin industrial zone, xibei town, wuxi city, jiangsu province, China 214194   
Emailalex_jfmesh@yeah.net  &  alex-jfmesh@hotmail.com

Website: www.silkscreen-mesh.com  

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