Screen printing knowledge
Screen printing knowledge
Screen printing mesh→drying→coating protective paint→sticking protective film→punching forming (high gloss processing)→inspection→packaging
In the production process, the most important are the three processes of “bottom plate”, “pre-treatment” and “screen printing”. The plate making process determines the quality of the sign.
1. Bottom production. Most of the signs and graphic plates of the signboards are photo-engraved and photo-engraved. First, the original ones are made, and then the serial printers are used to make the plates. In the imposition, the non-pitch imposition and the spacing imposition can be respectively adopted according to the precision required by the parts. If the size of the sign is not high, the non-pitch imposition can be used, as shown in Figure 4-12. After printing, it can be directly cut or cut and then stamped.
If the size accuracy of the sign is high, the spacing should be used. After the printing is completed, the punching is formed according to the position of the positioning hole. The distance between each part can be 2mm, the positioning hole can be 2mm, the hole spacing is 4mm, and the overall area can be 400. ×400mm, or depending on the process design.
If the color of the silk screen label is two or more colors, the photographic plate should have a positioning rule line, and the positioning hole can be drawn on the photographic plate of the main pattern of the label, so as to ensure the positioning accuracy when punching.
2. Positioning. The rules on the silk screen printing plate are the means to ensure the accuracy and uniformity of the graphic on the surface of the same printed workpiece and meet the requirements of color overprinting accuracy. According to the material and shape of the substrate, the positioning methods of silk screen signs are also different. The following are commonly used:
1 Positioning by the side. Applicable to straight-sided workpieces, such as nameplates, panels, various dials, etc., in the silk screen, the two right-angled sides of the workpiece can be close to the positioning bar.
2 rim positioning. It is suitable for silk screen printing of different forming workpieces. The outer frame of the workpiece can be formed by blanking. After trimming the gap, the outer frame is adhered to the position required by the platform according to the edge positioning method. When the silk screen is printed, only the shaped workpiece is placed. Just drop the frame.
3 hole positioning. The hole positioning is suitable for the imprinting silk screen of the same figure, that is, the positioning hole is punched out on the plate first, and the hole is positioned by the hole when the silk screen is printed, and finally the die blank forming is performed on the workpiece by the positioning hole.
4 coincidence positioning. Suitable for silk screen printing on transparent materials. When positioning, the second color pattern can be silk-printed on the paperboard and covered with the film printed with the first color pattern, so that the same package of the two-color pattern meets the design size requirement, and then the film and platform printed with the first color image are printed. Sticking firmly, when the second color pattern is screen printed, only the transparent workpiece printed with the first color pattern and the first color pattern on the platform are coincident to achieve the purpose of positioning.
3. Ink mixing. The requirements for screen printing inks for metal signs are strong adhesion, good wear resistance, clear graphics after printing, fast drying and no sealing. Metallic screen printing oil is generally made of synthetic resin such as alkyd or phenolic as a binder, and a special ink made by adding some pigments and additives. The ink has good printing performance, and is dried naturally after printing or baked at 120 ° C for 2 hours. The surface of the ink film is bright and has a three-dimensional effect, and is excellent in bonding strength and abrasion resistance with the aluminum plate. The ink film of this ink was tested with a JM-l type paint film abrasion tester. The rubber wheel loaded with the load of 7509 can be ground more than 500 times, and the cloth wheel can be ground up to 5000 times or more.
If the silk screen color label, you can refer to the relevant color printing ink color sample with ink, when adding ink, should add appropriate amount of varnish and desiccant. The ink desiccant is added in an amount of about 5 to 8% of the total amount of the ink, which is less likely to be dried, and the addition of the ink affects the adhesion of the ink.
4. The quality requirements of silk screen signs. The text, scale, graphics, positioning holes and colors of the screen printing signs shall comply with the drawings, and the surface of the finished product shall be free from obvious scratches.
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