Characteristics and process arrangement of screen printing

1. Screen printing process arrangement

Screen printing is a direct printing method, and there are three process arrangements: ① Cardboard → screen printing → post-printing processing, that is, screen printing is first performed on corrugated cardboard or other cardboard, and then it is made into cartons and carton products according to needs; ② Carton → screen printing, that is, screen printing directly on the corrugated boxes or other cartons and cartons that have been made; ③ secondary processing, that is, screen printing on the surface cardboard first, and then make it into corrugated cardboard as needed , and then made into cartons and carton products.

2. Screen printing features

① Wide adaptability: The screen printing format can be large or small; ② Thick ink color: In all printing processes, the screen printing ink layer is the thickest, the saturation is high, and the spot color printing effect is better; ③ Low cost: screen printing The plate making is easy and the printing process is simple; ④ The quality of the printed matter is stable; ⑤ The production efficiency is low: the screen printing speed is slow, which is not suitable for on-line production; 32 lines/cm.

3. Scope of application of screen printing

Screen printing is suitable for small batch production, packaging products with high requirements on printing appearance, unlimited cardboard thickness, and no damage to strength.

screen printing process

1. Screen printing

(1) Wire mesh selection ①Nylon wire mesh: Nylon wire mesh has high strength, high wear resistance, high alkali resistance, slightly poor acid resistance, good ink permeability, small wire diameter, good elasticity, and clear imprint; ②Polyester wire mesh: Polyester wire mesh has good stability, high strength, corrosion resistance, performance is better than nylon wire mesh, high tension, suitable for high-precision printing; ③Stainless steel wire mesh: stainless steel wire mesh has high strength, good stability, Small wire diameter, high mesh, good resistance, long life, poor elasticity, easy to break when impacted, suitable for precision printing, not suitable for curved surface printing; ④ Nickel-plated polyester screen: Nickel-plated polyester screen combines polyester screen And the advantages of stainless steel wire mesh, wide applicability, moderate price, poor corrosion resistance.

(2) Stretching the net

Screen frame has wooden frame, metal frame, plastic frame, combination frame and so on. When stretching the mesh, first clean the mesh frame. The mesh can be stretched manually, mechanically or pneumatically. After the mesh is stretched, it is bonded and trimmed. Stretching the mesh requires that the tension of the mesh is appropriate, uniform and stable, the wire direction is consistent, avoids diagonal pulling, and the warp and weft wires are parallel to each other.

(3) plate making

①Direct method: screen cleaning→coating photosensitive adhesive→printing→developing→revision. This method of gluing is time-consuming, the film thickness is adjustable, the combination is firm, the printing is durable, and the pictures and texts are prone to serrations. ②Indirect method: photosensitive film → printing plate → developing → film sticking → peeling base → revision. This method is complicated to operate, the lines are smooth, the film layer is not strong, the printing durability is low, and the film layer thickness is unchanged. ③Mixed method: screen cleaning → film sticking → printing → developing → revision. This method is easy to operate, the thickness is fixed, the lines are smoother and stronger.

(4) Screen direct plate making

Screen direct plate making is abbreviated as CTS. ①Laser ablation direct plate making: first coat the screen photosensitive glue on the metal wire mesh, burn through the photosensitive layer with laser, the mesh of the graphic part is transparent, the prepress system computer controls the ablation area, this method can only be used for metal network. ②Laser exposure direct plate making: first apply photosensitive glue on the screen, and the pre-press system computer controls the laser to image on the screen to make the screen. This plate-making method uses special photosensitive glue, the ultraviolet light wave range is narrow, and the price of the laser exposure system is high. ③Inkjet imaging system: first apply photosensitive glue on the screen, and the prepress system computer controls the inkjet system to spray the light-blocking ink on the photosensitive layer of the graphic part, and then fully exposes to ultraviolet rays. The graphic part is not photosensitive, and the photosensitive glue is washed away; the blank part is photosensitive and hardened. This method can be used with ordinary photosensitive glue, without losing the details of the image.

2. Screen printing machine

Screen printing machines include manual screen printing machines, semi-automatic screen printing machines, and automatic screen printing machines. There are also screen printing machines such as book-opening type, worktable lifting type, sliding type, cylinder type, curved type, curved type, cylinder screen type, double cylinder type, etc., which can be selected according to needs.

3. Special screen printing method

①UV imitation metal etching printing UV (ultraviolet) imitation metal etching printing is to print a layer of uneven translucent ink on the substrate with metallic mirror luster, and then cured by ultraviolet rays to produce a bright metal surface that is etched or frosted. Effect. The printed products are elegant and luxurious, and are used for high-end and exquisite packaging. This printing method uses UV-curing imitation metal etching ink, the substrate is gold cardboard, silver cardboard or composite material, and uses 70 mesh/cm to 100 mesh/cm screen. ②UV wrinkle pattern ink printing UV wrinkle pattern ink printing is to use UV wrinkle ink to print on the surface of the substrate, and then UV-cured to form a special wrinkle pattern decoration effect. This printing method uses 40 mesh/cm~60 mesh/cm screen, the ink film thickness is 20μ~30μ, and the effect is better if the thickness is larger. ③Ice flower effect printing Ice flower effect printing is to print the ice flower ink on the surface of the substrate with metallic luster by silk screen printing. The substrate of this printing method is gold and silver cardboard, using 60 mesh/cm to 100 mesh/cm screen. ④ Foaming printing Foaming printing is to use microsphere foaming ink to print on paper or other substrates with silk screen. This printing method uses 30 mesh/cm to 50 mesh/cm screen. The screen can also be used for fragrance ink screen printing, pearlescent ink screen printing, liquid crystal ink screen printing, phosphorescent ink screen printing, fluorescent ink screen printing, crystalline gloss screen printing, etc.

High-speed rotary screen printing production line

Due to the low printing speed, slow ink curing speed, difficult control of printing quality, and large consumption of printing materials, the flat screen printing method cannot meet the needs of the scale and mass production of cigarette cartons. The high-speed rotary screen printing production line is adopted, with fast printing speed, high productivity, stable quality of printed products and low consumption, which has changed the traditional flat screen printing, manual paper feeding and ink feeding methods, and is suitable for high-speed automatic and large-scale mass production. Folding carton.

Web-fed rotary screen printing uses a nickel metal round screen printing plate, a built-in squeegee, and an automatic inking system that transfers the printing ink from the round screen to the surface of the substrate supported by the impression cylinder. The entire printing process from paper feeding, ink supply, printing color registration, UV drying, etc. are fully controlled by computer.

The circular screen printing plate is suitable for large format rotary printing, the maximum speed can reach 125m/min, and the screen can be reused. Therefore, web-fed rotary screen printing can not only meet the requirements of special effects such as printing frosted and ice flowers, but also online hot stamping holographic anti-counterfeiting signs, concave-convex tooth printing, and die-cutting indentation, which is easy to realize high-speed automatic printing of cartons.