The quality of the screen printing, the thickness of the ink layer are closely related to the thickness of the screen, the viscosity of the ink, the hardness of the squeegee, the angle, and the method of plate making.
1. Silk plate and positioning: aluminum plate material uses three-point edge positioning. In color printing, light color is printed first, then dark color.
2. The distance between the printing plate and the substrate is 1-2 mm, and the distance is related to the selection of the screen. The nylon screen has good elasticity and high flexibility, generally 2-3 mm.
3. Polyurethane rubber sheet for squeegee, its hardness is 70-75 degrees, thickness is 8-9 mm, the proper squeegee angle is 70 degrees when printing, and the squeegee speed should move in a straight line at a uniform speed.
4. Adhesive protective film: After printing, in order to avoid trauma during cutting and transportation, a transparent pressure-sensitive adhesive protective film should be pasted on the surface and double-sided adhesive tape on the back.
5. Cutting: With a small shearing machine, forming can be punched by hole positioning or edge positioning. Engraving signs: generally refers to the use of a rotary saw or a vertical saw to engrave text or patterns from rubber or copper or other plates. In the mid-1980s, the rubber sheet with acrylic sheet (acrylic) was a typical material at that time. But now it has developed into metal plates, copper plates, aluminum plates and other materials. In order to show the three-dimensional effect of small characters, it has been applied to acrylic (acrylic) materials. Although the engraved sign does not have the point of body lighting or font lighting, it can express the text content by itself.

According to the application, there are mainly degreasing, sandblasting, wire drawing, polishing, and oxygen grease.
1. Degreasing: In order to make the surface of the aluminum substrate have a certain degree of ink affinity, the oil layer and oil stains on the surface need to be removed, which can be wiped with cotton yarn dipped in gasoline. Alkaline solution can also be used for chemical degreasing, such as sodium sulphate 30-50 g/l, sodium phosphate 40-60 g/l, sodium silicate 10-15 g/l, immersion in temperature 60-70 degrees for 2-5 Deoil in minutes.
2. Sandblasting: Sandblasting is to improve the adhesion between the ink and the metal material. A special sandblasting machine is usually used for spraying. River sand can be used after being filtered through a sieve.
3. Wire drawing: also known as twisting, which is to process fine straight lines on the surface of the aluminum plate by mechanical friction. It is a relatively new surface decorative treatment process, which can overcome defects such as scratches on the aluminum surface. Increase the utilization rate of materials. There are two types of wire drawing: thick wire and thin wire. Generally, a stainless steel wire brush with a diameter of 0.1 mm or a scouring cloth belt brush is used, or a nylon abrasive belt can be used for processing.
4. Polishing: To overcome the surface defects of aluminum-based materials and improve the surface finish. Polishing is divided into mechanical polishing and chemical polishing. Mechanical polishing uses cloth wheel polishing machine. Chemical polishing is mostly performed in acid solution, such as sulfuric acid 15%, nitric acid 10%, temperature 90-100 degrees, and time is 2-3 minutes.
5. Oxidation: The polished surface of the aluminum plate has the remaining polishing soap, which should be wiped off by dipping in gasoline, and then chemically degreasing, then immersed in a nitric acid solution (1:1 ratio of nitric acid and water), and then taken out after 10 minutes. Then put it into an oxidation tank for electrochemical oxidation. Oxidation solution formula: 160-200 g/ml nitric acid, temperature 10-20 degrees, time 30 minutes.
The oxidized aluminum plate is fully washed and dried, and an oxide layer with uniform pores is formed on the surface, that is, an oxide film, which should avoid dirt pollution. The oxidized aluminum plate is best to be printed immediately. If it cannot be printed immediately, it should be wrapped with a soft paper septum or placed directly on the drying rack. The storage time should not exceed one week.
The oxide layer on the surface of the aluminum plate can absorb dyes, moisture and other salts, so do not touch the surface with your hands or oily objects during screen printing. When the ink is printed on the oxide layer, the ink penetrates into the pores. The heating of the next process is to accelerate the ink penetration into the pores until all the pores on the surface covered by the ink are filled.
The ink printed on the surface seldom spreads or does not spread, which can ensure the accuracy and clarity of text and patterns.
6. Sealing: Its function is to seal the ink firmly in the pores, never overflow or spread. For the parts that are not covered by ink, the function of sealing is to fill the gaps of the oxide film, make it impermeable, and strengthen the corrosion resistance of the surface. Generally, nickel sulfate solution is used for sealing. Recipe: 10-12 ml of nickel Chinese acid, temperature 80-90 degrees, 10-15 minutes. After sealing the hole, touch the surface with your hands or other oily things and wash it off with normal detergent. In today's screen printing of metal signs or non-metal plates, more printing inks can be used, but it is not easy to choose suitable inks (paints).

1. Baking enamel:
It is a single-liquid formula that cross-links when heated and has better storage performance. Can be stored for 6 months to one year. It has good finish, abrasion resistance, chemical resistance and weather resistance, so it is most commonly used. Alkyd, acrylic and polyester have these characteristics. Epoxy resin has a tendency to break and pulverize and is generally not used outdoors, but it dries quickly and has good chemical resistance. Alkyd enamels have balanced physical properties, such as chemical resistance and weather resistance, formability, hardness and gloss, and are most widely used.
2. Air drying enamel:
It is usually made of drunk acid, and it needs to use oxygen in the air to solidify through reaction. The performance of acid enamel paint depends on the type and quantity of oil used. The longer the oil drying time, the longer the drying time of the enamel paint. When the drying speed is used as the condition, paints with long drying time generally have good surface durability. These paints are mostly used for outdoor metal signs.
3. Melting and volatile ink:
Only rely on solvent volatilization to achieve drying. The final performance of the coating is determined by the inherent physical properties of the polymer before it is formulated into a liquid. Such polymers contain thermoplastic acrylic acid. Screen printing inks based on volatile properties are often damaged by dissolution. There are some acrylics that are insoluble in gasoline and alcohol, and the film surface can be in contact with them. Therefore, inks based on thermoplastic acrylic, ethylene and other soluble polymers are mostly used on plastic substrates.
4. Two-liquid ink:
Common ones are epoxy or polyurethane, although there are many others. The two-liquid system that is often used in the wood is the most sensible choice for energy saving. Its coating quality is high, but it is not convenient to mix. In addition, it is necessary to choose according to the purpose of the product. If the product may be used outdoors and has some flexibility, then use aliphatic hydrocarbon as the main urethane ink. Two-component epoxy resin ink has the same performance as baking enamel, but the formability is not good enough.
5. Ink additives:
Like other inks, metal screen printing inks also contain additives, which are a small amount of chemical agents added during production to improve the performance of the ink film. Some can accelerate or initiate curing, while others can cause bubbles to burst and ink. The quality is uniform, reducing the possibility of conjunctiva. The manufacturer mixes the additives with the ink according to the specific formula. What the printer needs is to dilute the ink to a consistency suitable for printing.

Classification of signs:
Classified according to the form of signs: 1. Horizontal signs: The entire ratio is relatively long horizontally. Generally the entire surface is used as an advertising sign. It can generally be seen on the walls of small shops and large buildings. 2. Vertical sign: The entire ratio is relatively long vertically. Generally the entire surface is used as an advertising sign. 3. Protruding signs: protruding on the wall of the building, the entire surface except the back or both sides of the wall are used as signs for advertising carriers. 4. Columnar signs: horizontal, vertical, and three-dimensional signs marked on certain fixed structures on the ground. 5. Roof signs: refers to the installation of fixed structures on the roof of a certain building and hanging on them A board-shaped, cuboidal or magical sign that is attached or pasted.

According to the classification of sign materials:
1. Smooth signs: very smooth signs with oily screen or surface.
2. Luminous material signs: use luminous material signs (that is, what we usually call neon lights).
3. Acrylic signs (acrylic): Acrylic material is used as the main material of the board. 4. Metal signs: If there is no special designation of the plate surface, metal is used as the main material of the plate surface or text.
5. Electro-optic board: a sign that uses light-emitting diodes or luminous tubes to achieve monochrome or color performance. According to the light-emitting diode and the way of expression, it can be divided into five types: luminous panel, LCD, LED, CRT, FDT.

Classified according to the purpose of use of the sign:
1. Time difference: Illumination signs: For day and night use, install luminous tubes inside the signs, install light projectors inside, and install lights and other signs outside the signs. No lighting signs: There is no single purpose for day and night use, and no signs for lighting facilities.
2. Different locations: indoor signs: signs located indoors, such as direction arrow signs, indoor reception signs, etc. Outdoor signs: Signs located in all spaces other than indoors.
3. Different purposes: commercial signs: generally refer to signs set up for commercial purposes. Public signs: Signs set in public places to announce news to the public or to announce certain information.

1. Smooth signs: very smooth signs with oily screen or surface.

2. Luminous material signs: use luminous material signs (that is, what we usually call neon lights).

3. Acrylic signs (acrylic): Acrylic material is used as the main material of the board.

4. Metal signs: If there is no special designation of the plate surface, metal is used as the main material of the plate surface or text.

5. Electro-optical board: a sign that uses light-emitting diodes or luminous tubes to achieve monochrome or color performance. According to the light-emitting diode and the way of expression, it can be divided into five types: luminous panel, LCD, LED, CRT, FDT.