A printing method of fabric - rotary screen printing

Rotary screen printing is a printing method in which the color paste in the rotary screen is printed on the fabric by pressure using a doctor blade.

First, rotary screen printing institutions

Rotary screen printing machine usually consists of four parts: cloth feeding device, printing machine head, drying device, and falling cloth device. At present, circular screen printing machines usually have eight types of rotary screen printing machines, including eight colors, twelve colors, sixteen colors, and twenty-four colors. There are two kinds of printing machine: 640mm and 904mm. Of these, 640 mm are mostly round screen printing machines. The rotary screen printing machine has the advantages of easy operation, low labor intensity, high output, suitable for printing of various fabrics, and it is suitable for printing of multi-variety and small-batch fabrics.

(1) Feeding device Rotary screen printing machine feeding device There are two types of cloth feeding and cloth feeding. When the cloth is rolled into the cloth, the swing cloth may be pressed against the cloth roll, and the cloth may be introduced into the printing device by means of the cloth roll. When the fabric is fed into the fabric, the fabric tracks with the circulating rubber track to complete printing. This track is first coated with a layer of thermoplastic resin on the surface of the rubber roller, and the fabric can be flatly adhered. An infrared radiant heater is installed next to the rubber roller to heat the resin on the track. The thermoplastic resin can be used to process 20 to 1 million meters of fabric at a time. If you find that the viscosity is not good, you can recoat it.

(b) Printing device The rotary screen printing device includes a rotary screen, a doctor blade, a slurry supply device, and the like.

1. Round net Round net is the flower version of the printing machine. Made of nickel metal, also known as nickel mesh, hexagonal mesh. The ends of the rotary screen are fixed with bulkheads to prevent deformation of the rotary screen during printing, affecting the accuracy of the flowers, and being able to withstand the pressure of the color paste and the doctor blade during printing. In order to improve the elasticity of the circular net and reduce the pressure to bear, the round net must be installed away from the center line of the support roller, and generally it should deviate from about 16 mm. Each rotary machine base has a reading device that can display the pressure of the blade that each side receives.

2. The blade of the doctor blade rotary screen printing machine is installed on the doctor blade frame on the center line of the rotary screen. The doctor frame is equipped with a doctor blade and a feed pipe. The scraper is made of chromium, molybdenum, vanadium, and steel alloys, and has a small friction coefficient and can be adjusted to any angle. During printing, the blade of the doctor blade is tangent to the inner circle of the rotary screen. The scraper applies pressure to the color paste, and the scraper supplements the composite action.

The pressure and position of the squeegee of the rotary screen printing machine can be adjusted to suit various patterns and fabric printings of various thick and thin color pastes.

3. Printing device Rotary screen printing machine is automatic feeding. Each cylinder is equipped with a slurry system. When the color paste is supplied, one end of the plastic tube on the machine table is set on the metal feed tube, and the hose at the other end of the machine is inserted into the color paste bucket, and the rotary screen is input by the pump, and the height of the paste liquid level is automatically controlled by the electrode.

(C) Drying and Clothing Apparatus The rotary screen printing machine uses loose hot air drying. After the printing, it is separated from the rubber track, and the drying section is introduced. The loose flat is placed on the polyester web and the cloth is dried by hot air. The cloth is pulled into the cloth by the electric axle.

(4) Advantages and disadvantages of the rotary screen printing machine The rotary screen printing machine has the advantages of low labor intensity, high production efficiency, and strong adaptability to fabrics. Suitable for chemical fiber fabrics, knitted fabrics, light fabric printing. Can get the lively, bright color effect, and can avoid the spread of rickets. However, due to the limitations of the circular network structure, the effect of printing fine lines is not very satisfactory.

Second, the preparation of rotary net

(I) Process of making a net

Round Die Die --- Copper Plating --- Polishing --- Rolling Point --- Polishing --- Chrome Plating --- Insulating Insulators --- Heating --- Hardening --- Polishing ---- Cleaning - Mold Release - Nickel Wire Forming

(two) the role of the main processes

1. The copper plating can make the core mold meet the requirements of the circumference of the rotary screen, and because the copper metal texture is soft, it can be easily rolled.

2. The rolling point is rolling out the circular mesh mesh specification on the copper plating core mold.

3. Chrome plating Because of the poor adhesion of chromium and nickel, it is easy to release the nickel mesh after molding.

4. The insulator is embedded in the insulator at the mesh part so that current cannot be applied during electroplating: Nickel metal can be formed by depositing nickel metal on the unembedded part. Epoxy resin 604 and epoxy resin catalyst 650 are generally mixed in equal amounts. After curing, the insulator was cured by baking at 175°C for 7 minutes.

5. Nickel plating is performed in nickel sulfate and nickel oxide plating baths. The thickness of the nickel mesh is generally 0.10 to 0.12 mm. After meeting the requirements, the nickel mesh was released by mechanical extrusion.

Round net system

(I) Inspection and preparation of black-and-white manuscripts in the process of rotary screen manufacturing --- Circular screen selection --- Circular screen cleaning --- Photosensitive adhesive --- Exposure ---Development ---Curing --- Gel bulkhead - check for use

(II) Examination and Preparation of Black-and-white Papers Black and white papers that have been separated and depicted can be directly exposed. However, when the pattern is 1/2 and 1/3 joints, full-roll positive exposure should be used. Before the exposure, it is necessary to conduct a thorough inspection of the black-and-white drafts to prevent rickets.

(3) The circular nets are selected to choose different specifications of circular nets according to the fabric width and pattern and other factors.
1. There are 480, 640, 913, 1826mm and so on in perimeter specifications. The work width is 1280,1620,1850,2400,2800,3200mm. The length of the circular net is calculated according to the following formula. The length of the circular net = the working width + 2x59mm (59mm is the margin). At present, the most commonly used perimeter is 640mm, and the working width is 1620mm.

2. Circular screen mesh specifications Common mesh screen mesh specifications are shown in the following table

Common circular mesh specifications

Mesh No. of holes/cm2 Mesh area (mm2) Mesh hole diameter (mm) Thickness (mm) Hole area/total area (%)

25 120 0.2 0.480 0.2 24

40 290 0.07 0.285 0.11 20

60 670 0.02 0.152 0.1 18

80 1150 0.01 0.1 0.08 11

125 1630 0.006 0.083 0.080 9

3. The number of options

(1) Fine-patterned flowers and lines with a large number of meshes.

(2) Fabric Properties Thick fabrics have a large amount of pulp, and meshes with a small mesh number should be used. Pure cotton fabrics use a mesh with a smaller number of meshes, and a mesh with a larger number of meshes for chemical fibers and blended fabrics.

(3) Color paste properties The color paste has good fluidity, and a large number of meshes can be used.

(4) The speed of the printing machine is fast, and the rate of penetration of the color paste is low, and a mesh with a small mesh number is selected.

When printing a large area flower type (with wrapping line) 60 mesh net used: small area flower type (without wrapping line) 80 mesh round net: electronic-based pattern selection 80 mesh round net is better : Line-based patterns are more common with 100 mesh.

Determine the number of round meshes to integrate various conditions and choose the actual production situation. The width of the finest lines that can be printed on various screens can be seen in the table:

The relationship between the number of round meshes and the size of the lines

Number of meshes 100806040

Line size (mm)0.250.30.40.6

(d) Before cleaning the rotary screen, the rotary screen must be cleaned. The circular nets are placed on a cleaning rack, and reciprocated with 60% chromic acid, washed with water, rinsed with 10% soda ash, and finally rinsed with water. Because the flushing is from inside to outside, the flushing pressure cannot be too great. When the surface of the circular net presents a uniform water film, it can be prevented from entering the oven at a low temperature.

(5) Photosensitive adhesive

1. The prescription photosensitive liquid is composed of a photosensitive adhesive and a photosensitizer. The prescription refers to the product description.

The viscosity of the photographic solution is such that the glass rod can be drawn straight down.

2. Coating method When the coating liquid is applied, clean the waterless stained rubber scraper ring and put it on the clean lower iron ring. Pour 200-300g sensitized plastic and take the clean circular net to put the lower iron ring on and put the iron ring. And adjust the glue pressure plate pressed. Hold the ring in both hands and move it from the bottom up (250mm/s) at a constant speed so that the photosensitive liquid is evenly coated on the surface of the rotary screen. After 20 --- 25 °C bake 20 --- 25 minutes.

The coating speed should be appropriate, too slow, too much glue, back into the mesh wall, wash difficult; too fast, film is not strong, prone to bubbles. The coating liquid is generally operated under a yellow light.

(6) When the exposure is exposed, the circular screen is placed outside the inflated rubber tube, and the positive film is closely attached to the circular network for exposure. The exposure time depends on the nature of the film, the brightness of the light, the properties of the photosensitive liquid, the thickness of the adhesive layer, and the number of round meshes.

The exposure conditions are: indoor temperature 25°C, relative humidity 65%, exposure time shown in the table below:

Exposure time at 25°C and 65% relative humidity

The number of round mesh 10080604025

Exposure time (sec) 56---71015--2025

Exposure time must be strictly controlled, otherwise the exposure part will produce small holes, and even the coating will fall off, affecting the quality of the circular screen.

(7) After the development exposure, the circular screen is soaked in water of 18--28°C for 10-15 minutes to remove the unexposed parts of the adhesive layer and flushed from the inside to the outside with cold or warm water. Finally, it is easily colored with a salt base violet to facilitate inspection of rickets.

(8) Inspection and baking After careful inspection and repair, it shall be dried by hot air at 50°C and baked at 180°C for 2 to 2.5 hours.

(9) The plastic knotty round net is very thin, and it is necessary to hold the bulkhead on both sides in order to maintain the circular net shape. The round net marks the flowers and it is better to use the epoxy resin to fix the round nets and the heads.

Reprinted from: our global textile Author: juckey