Introduction Silk screen printing

There are various methods for the pretreatment of the aluminum substrate. According to the application, there are mainly degreasing, sandblasting, wire drawing, polishing, and oxygen grease.

1. Oxidation: The surface of the aluminum plate after polishing has residual polishing soap, which is wiped off with a veil of yam and then chemically deoiled, then immersed in a nitric acid solution (1:1 ratio of nitric acid and water) and removed after 10 minutes. Then placed in an oxidation tank for electrochemical oxidation. Oxidized liquid formula: nitric acid 160-200 g/ml, temperature 10-20 degrees, time 30 minutes.

The well-oxidized aluminum plate is fully washed and air-dried, and a layer of uniform oxide layer, ie, an oxide film, is formed on the surface, and contamination of the contaminants should be avoided. Good oxidation of the aluminum plate is best to immediately print, if not immediately print, use soft paper septa wrapped or directly on the air frame, storage time can not exceed one week.

The oxide layer on the surface of the aluminum plate can adsorb dyes, moisture, and other salts, so the surface is not touched by hand or with oily material during screen printing. When the ink is printed on the oxide layer, the ink penetrates into the pores. The warming of the next step is to accelerate the ink into the pores until all the ink-covered surface pores have been filled.

The ink printed on the surface rarely spreads or does not spread, ensuring the accuracy and clarity of the text and the pattern.

2, closed: Its role is to firmly seal the ink in the pores, never overflow or spread. For areas that are not filled with ink, the function of the seal is to fill the gaps of the oxide film and make it impervious to water and enhance the corrosion resistance of the surface. Nickel sulfate solution is generally used for sealing. Formula: 10-12 ml of nickel vanadate, temperature 80-90 degrees, 10-15 minutes. After sealing the hole, touch the surface with hand or other oily thing and wash it off with a general cleaning agent.

3. Degreasing: In order to make the surface of the aluminum substrate have certain ink affinity, the oil layer and the oil stain on the surface need to be removed, and it can be wiped with cotton yarn and gasoline. Chemical degreasing can also be carried out with an alkaline solution, such as sodium sulfate 30-50 g/L, sodium phosphate 40-60 g/L, sodium silicate 10-15 g/L, dipping 2-5 at a temperature of 60-70C. Degreasing in minutes.

4, sandblasting: sandblasting is to improve the adhesion of ink and metal materials, usually using a special sandblasting machine spray treatment, if the 0.5-1 mm thick aluminum plate, sandblasting sand diameter of 0.05-0.15 mm, also Available river sand, sieved and used.

5, drawing: also known as skeining, is to use the method of mechanical friction on the surface of the aluminum plate to produce a fine straight lines. It is a relatively new surface decorative treatment process that can overcome defects such as scratches on aluminum surfaces. Improve the use of materials. There are two types of wire drawing, such as stainless steel wire brush with a diameter of 0.1 mm or a brush with a scouring pad, and nylon belts.

6, polishing: to overcome the surface defects of aluminum-based materials, improve the surface finish. Polishing is divided into mechanical polishing and chemical polishing. Mechanical polishing uses a cloth wheel polisher, and the chemical polishing is performed in an acidic solution such as sulfuric acid 15%, nitric acid 10%, temperature 90-100 degrees, and time 2-3 minutes.