Common-sign-making-process-(4)

Ink or other chemical reagents are used in conventional practices, which will certainly pollute the environment. With the advancement of science and technology, there will be better processing techniques for the production of signs.
1. Paint film carving method:
It is a kind of manual plate making method, which is relatively simple. It can print monochromatic patterns and characters that are generally not too delicate.
⑴Spray engraving paint film paper: paste the tracing paper on the flat wood plate, use a pen to adjust 1 part of rubber water (volume ratio), 1 part of gasoline, and evenly spread on the paper, dry After spraying the soft varnish 3-5 times, after each spraying, dry it in an oven at 40-50 degrees. The thickness of the paint film should be sprayed to 5-6 mm. The paint film should be bright, uniform, without bubbles, and stain.
⑵Carving graphics: Paste the paint film paper on the graphics, use a carving knife, compass knife, and ruler to carve the graphics, and gently remove the paint film.
⑶ Reposting: After engraving the graphics, it can be reposted on the screen frame made in advance. The method is to place the carved paint film under the screen frame and press it tightly, and gently rub it with cotton dampened with a little thinner until the paint film and the screen are firmly adhered. After drying for a few minutes, remove the tracing paper. If the paper is not all off, wipe it with cotton dampened with water. The blank part is coated with nitrocellulose paint to block the mesh of the screen. It can be printed after drying.
2. Carbon paper printing method:
It is also a simpler manual plate making method.
⑴Cut photosensitive paper: photosensitive paper is a kind of carbon paper made by thickly coating with oxygen and barium base paper, which is cut according to the size of the figure for use.
⑵ Sensitization: soak in a solution of 500 milliliters and 20 grams of ammonium dichromate for 3-5 minutes, take out the carbon paper, and drain the water.
(3) Exposure: Stick the carbon paper flat on the clean glass, with the glue film facing upward, cover the positive polyester film base plate on the top, and use the exposure machine for exposure. The exposure time is 8-12 minutes.
⑷Development: After exposure, soak in 40~50°C warm water for several minutes to make the film and positive plate and zinc oxide base paper separate naturally. Use warm water to develop carefully until the force-shaped characters are clear.
⑸Reposting: Put the prepared plate under the frame of the pre-stretched screen, cover several layers of newspaper on the screen, press the glass plate, and press it with a weight of 1-2 kg/cm2. At this time, the film Stick it firmly to the screen, remove the heavy objects and newspapers, use an electric oven to dry the film, and then remove the base paper, the film graphics will be transferred to the screen. Carefully check the graphics for defects. After passing the test, coat the screen around the graphics with a layer of nitro enamel for protection, and install the screen printing plate on the printing plate for printing. The scope of application of this plate-making method is the same as the paint film engraving method.
3. Photosensitive plate-making method: The printing plate used for silk-screening signs requires high precision, and generally adopts three advanced photosensitive plate-making methods: direct, indirect and direct.
A. Direct plate making method:
⑴ The post frame uses aluminum frame, and does not need to stretch the net. The air pressure is 5-6 kg/cm². The acetal adhesive net is used. The tension is measured by tension. The tension is 5-7 kg. The sink size should be Less than 2 mm.
⑵Cleaning the screen: Use washing powder, detergent, ethanol, etc. as a detergent to clean both sides of the screen, rinse with water, and dry it with hot air for use. The purpose is to make the net better bond with the photosensitive glue.
⑶Scraper (coating bucket, coater): The squeegee for coating photosensitive glue can be made of stainless steel, or it can be made of organic glass plate. Its length is generally slightly smaller than the inner diameter of the screen frame (make a set of scrapers with different lengths) B. The edge of the scraper must be thin and not edged, smooth and straight, and not allowed to have defects such as bumps, burrs, scars, etc., to affect the quality of plate making. When coating the screen photosensitive glue, dry it every three times, and it needs to be done continuously 3-4 times until the glue film reaches the required thickness before exposure.
⑷The temperature of the drying oven is preferably an adjustable temperature drying oven. The drying temperature of the photosensitive adhesive is generally controlled at about 40 degrees. If the baking time is too long or the temperature is too high, the quality of the photosensitive layer will be affected.
⑸Safety light: The lighting source of the studio generally uses orange, yellow or red light as the safety light, but from the visual point of view, the orange-yellow light source is more comfortable. Its brightness is suitable to be able to see everything clearly.
⑹Inspect the base plate: Before printing, the base plate must be carefully inspected, including dust on the plate surface, blackness of the base plate, line breaks, sand hole defects, etc. and whether the front and back of the image and text meet the requirements.
B. Indirect manufacturing method:
⑴Prepare the screen frame and photosensitive film: Wash the stretched screen frame (220-260 mesh for nylon wire) with 10% sodium phosphate aqueous solution to remove oil stains.
The wire mesh photosensitive film is a kind of photosensitive glue with polyenol glue as the main body. The film film is coated with gelatin as the main photosensitive agent on a transparent plastic base of 0.12-0.06 mm. Before use, it is connected to the size of the pattern, and each side is wide. Use a cloth to wipe off the powder dirt on the membrane.
⑵Exposure: Press the film and the bottom plate tightly in the exposure machine, and use carbon lamp or xenon lamp for exposure. The distance between the screen frame and the light source is 50-60 cm, and the exposure time is 2-6 minutes.
⑶Development: After exposure, put the phenanthrene film on a flat plate, soak the retina with warm water for 1-2 minutes, spray with a water nozzle, and dissolve the non-photosensitive part (graphic part) with the water after printing and development until the pattern So far.
⑷Film film: stick the exposed film surface on the screen, use a rubber plate or other straight board on the back of the human film, gently scrape it to make the film and the net contact firmly, immediately put it in the oven at a temperature of 55± Bake for 8-12 minutes at 2 degrees. After drying, fix the screen frame on the printing plate for trial printing.
⑹ Film removal method: In the process of exposure and development, if the plate is found to be unqualified, immediately use warm water to brush off the film and make it again. If the plate has been dried or when the film is removed after a period of production, use one part each of industrial sodium hypochlorite and water and soak for 10-20 minutes. Or the screen plate can be heated with 5% sodium hydroxide aqueous solution to remove the film.
C. Direct plate making method:
The direct method is a mixed plate-making method of the direct method and the indirect method. It is different from the indirect method in that the indirect method first applies the image on the film film and then transfers the image to the screen, while the direct method first applies the film film After reposting on the silk screen, it is exposed to make an image.