I. Pattern Design and Pre - planning

1. Confirmation of Repeat Size

When undertaking any cotton fabric printing order, the primary task is to determine the repeat size. The repeat size refers to the distance in the warp direction (lengthwise) of the fabric where the same pattern repeats completely. The most common repeat size in the industry is 64 cm, which is suitable for mainstream rotary screen printing equipment. With the popularization of imported high - end rotary screen printing machines, three new specifications of 81.7 cm, 91.4 cm, and 101.8 cm have been added. If the repeat size of an order exceeds the above range, the flat - screen printing process needs to be adopted. In terms of process characteristics, although flat - screen printing has a relatively low production efficiency, it has significant advantages in presenting patterns that require rich layers, such as flowers, figures, and cloud patterns. Correspondingly, the processing cost is also higher.

2. Analysis of Color - way in Patterns

Printed patterns are usually composed of a combination of multiple colors. The number of color - ways directly affects the selection of the production process and cost accounting. For simple patterns with distinct color blocks, the number of colors can be directly counted. However, for complex patterns such as flower gradations and cloud - pattern transitions, professional technicians or factories need to use professional equipment to analyze and determine the number of color - ways. Subjective judgment should be avoided. Each color corresponds to a set of printing screens. The rotary screen printing machine can typically achieve 16 - color printing, and there is no absolute upper limit for the number of color - ways in flat - screen printing. However, limited by the factory's equipment configuration, it generally does not exceed 12 color - ways. Before accepting an order, it is necessary to confirm the equipment compatibility with the printing factory.

3. Selection of Printing Dyes

For cotton fabric printing, two main processes are reactive printing and pigment printing. They can be distinguished by a simple method: fabrics printed by reactive printing have a soft handfeel, and the pattern area has strong water absorption, with water droplets quickly penetrating. Fabrics printed by pigment printing have a stiffer handfeel, and the pattern area has better water resistance, with water droplets not easily penetrating. In addition, bleach or disinfectant can be used for auxiliary testing. If the color fades after contact with the bleach solution, it is reactive printing.

The final choice of dye type is determined by customer requirements. In terms of process cost and environmental friendliness, the reactive printing process is more complex, and the comprehensive cost is higher than that of pigment printing. However, due to meeting the global environmental protection trend, its application range is continuously expanding.

II. Screen - making Process

After determining the printing process (rotary screen or flat screen), it is necessary to enter the screen - making stage. This stage is mainly completed by the printing factory, and the core process is as follows: First, the factory performs computer color separation on the pattern sample provided by the customer to generate a complete color - effect draft. Then, a small - size screen is made for proofing. After the sample is confirmed as qualified by the customer, large - size production screens are mass - produced, completing the core preparatory work before printing.

III. Core Printing Procedures

1. Pre - treatment before Printing

Similar to the pre - treatment requirements for dyed fabrics, cotton fabrics need to complete processes such as singeing, desizing, scouring, bleaching, and mercerizing before printing. For pigment printing, mercerizing can be omitted, but it will result in a relatively large warp - way shrinkage rate of the fabric. For fabrics that have undergone mercerizing, heat - setting is required to ensure dimensional stability, and then they can enter the printing stage.

In terms of production efficiency comparison, flat - screen printing (plate screen printing or flat screen printing) is slower, with a conventional speed of 20 - 30 meters per minute and a relatively long pre - preparation time. Rotary screen printing (rotary screen printing) is more efficient, with a conventional speed of 40 - 50 meters per minute. For simple color - block patterns, the printing speed can even reach 80 meters per minute, making it the preferred process for large - scale production.

2. Differences in Post - treatment of Different Printing Processes

(1) Post - treatment of Pigment Printing

Pigment printing is a physical color - fixing process. After printing, it needs to go through a baking process. High temperature is used to make the pigment combine closely with the fabric fibers to improve color fastness. Some factories may omit the baking process to reduce costs. This has little impact on the color fastness of light - colored printed products, but dark - colored products will show obvious color fading problems. After baking, depending on customer requirements, tentering and softening treatments are carried out, and calendering, shrinking, and other processes can also be selectively carried out. Finally, finished product inspection and packaging are completed.

(2) Post - treatment of Reactive Printing

Reactive printing relies on a chemical reaction for color - fixing. The core principle is that the reactive dye groups react chemically with the cotton fiber groups under specific temperature and humidity conditions. Therefore, the first process after printing is steaming. By controlling the temperature and humidity, the dye and fiber are made to react fully. After steaming, a washing process is required to remove unreacted excess dyes, printing pastes, catalysts, and other impurities. The subsequent processes are similar to those of pigment printing, including tentering and softening, shrinking, calendering, and other conventional treatments. Functional finishing such as anti - mite and antibacterial, three - proof (water - proof, oil - proof, stain - proof), and flame - retardant can also be added according to customer requirements.

IV. Development Trends of Printing Processes

In recent years, pigment printing technology has been continuously upgraded. New materials such as super - soft pigments and high - sunlight - fastness pigments have been widely applied. Some pigment - printed products have passed the European OeKe - Tex 100 environmental protection certification, breaking the traditional perception that pigment printing is "un - environmental and has a poor handfeel." Reactive printing, due to its environmental advantages, is more suitable for fields with high safety requirements, such as clothing fabrics (especially infant clothing) and home textile bedding fabrics. The market demand for it continues to grow.

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