1、 Screen printing

Screen printing includes the preparation of a printing screen, which is made of nylon, polyester fiber, or metal fabric with fine mesh tightly stretched on a wooden or metal frame. The screen used in the printing process was once made of fine silk and was called screen printing. Although silk screens are no longer used, the name screen printing is still commonly used in the printing process. A layer of opaque non porous film should be coated on the mesh fabric. In areas with patterns, the opaque film should be removed and a fine mesh screen should be left, which is the area where the picture will be printed. Most commercial mesh fabrics are first coated with a photosensitive film, and then the film on the striped areas is removed by photosensitive method to reveal the image.

Place a screen on the fabric to be printed for printing. Pour the printing paste into the printing frame and use a scraper (a tool similar to a windshield wiper on a car) to force it through the mesh of the screen.

Each color in the printed artwork requires a separate sieve, with the intention of printing different colors separately. Example 3: Three sets of color printing require three mesh frames to separately print the three colors onto the fabric. In addition, the patterns of each color in the picture must be accurately positioned on the sieve to ensure accurate orientation of the patterns after printing, avoiding the phenomenon of the green stem of a rose being printed on the center of the red petals. Printing on flowers refers to the industrial term for accurately printing all pattern colors onto a fabric.

There are three ways to achieve screen printing, and the principles of each method are basically the same. The first type is artisanal screen printing, which was very common in the 1920s and is still widely used today. Until the mid-1950s, when modern technology empowered this technique, artisanal screen printing remained a specialized method of screen printing. The second method is called active screen printing (also known as flat screen printing and active flat screen printing). In the mid-1960s, there was further development, and the shape of sieve mesh shifted from craftsmanship and active flat mesh to circular mesh shape. The third method is called circular screen printing or circular screen printing, which is currently the most widely used screen printing method.

2、 Craft screen printing

Craftsmanship screen printing is commercially produced on a long tabletop (with a tabletop length of up to 60 yards). The printed fabric roll is smoothly laid on the tabletop, and a small amount of adhesive material is pre coated on the surface of the tabletop. Then the printing worker moves the frame continuously by hand along the entire table, printing one frame at a time until all the fabric is printed. Each mesh frame corresponds to a printing pattern. The production speed of this method is 50-90 yards per hour.

Commercial screen printing is also widely used to print cut pieces of clothing. In the garment printing process, the garment making process and the printing process are placed together. Before sewing the pieces together, customers' customized or common drawings are printed on the pieces. Due to the ability of skilled screen printing to create large mesh frames for large floral patterns, this printing method can also be used to print fabrics such as beach towels, innovative printed aprons, curtains, and shower curtains.

Handmade screen printing is also used to print limited edition, highly fashionable women's clothing and to print small batches of products for market exploration. The method of screen printing with craftsmanship is shown in Figure 9-3.

3、 Active screen printing

Active screen printing (or flat screen printing) is the same as manual screen printing except that the process is automated, so the speed is faster. The printed fabric is conveyed to the screen through a wide rubber belt, rather than being placed on a long platform (as with artisanal screen printing). Similar to artisanal screen printing, active screen printing is also an intermittent process rather than a continuous process. In this process, the fabric is moved under the screen and then stopped. The scraper on the screen performs scraping (active scraping). After scraping, the fabric continues to move under the next frame, with a production speed of approximately 500 yards per hour. Active screen printing can only be used for whole rolls of fabric, and cut pieces of clothing generally do not need to be printed in this way.

As a commercial production process, the production of active screen printing (referring to flat screen printing) is decreasing due to the preference for using circular screen printing with higher production power.

4、 Round screen printing

Circular screen printing differs from other screen printing methods in several important aspects. Round screen printing is the same as the drum printing that I will describe in my section. It is a continuous process, and the printed fabric is transported to the moving round screen flower tube through a wide rubber belt. Among screen printing, circular screen printing has the fastest production speed, exceeding 3500 yards per hour. Use seamless perforated metal or plastic mesh. The maximum circumference of the circular mesh is greater than 40 inches, so the maximum flower size is also greater than 40 inches. Round screen printing machines with over 20 colors have also been produced, and this printing method is gradually replacing drum printing.

5、 Roller printing

Roller printing, such as newspaper printing, is a high-speed process that can produce over 6000 yards of printed fabric per hour. This method is also known as mechanical printing. In roller printing, drawings are printed on the fabric by carving copper rollers (or rolls). The copper drum can be carved with exquisitely arranged fine lines, allowing for the printing of very delicate and soft paintings. For example, the precise and intricate Perisley vortex pattern printed on tweed is a type of picture printed through roller printing. The carving of the flower tube should be completely consistent with the design draft of the graphic designer, and each color requires a carving roller. In specific printing processes in the textile industry, five roll printing, six roll printing, etc. are often used to indicate five or six color drum printing.

Roller printing is the production method that uses the least amount of large-scale printing, and the output continues to decline every year. If the batch size for producing each trick is not very large, this method is not economical. In most cases, the cost and consumption of drum preparation and equipment adjustment are high, making it uneconomical to use this method for printing. However, drum printing is often used for prints with extremely fine lines, such as Petzli spiral pattern tweed prints and primary prints that are printed in many seasons. Figures 9-8 and 9-9 respectively show the side view and photos of the drum printing machine.

The size of the carved flower tube depends on the printing machine and the printed image. Most printing machines can be equipped with flower tubes with a maximum circumference of 16 inches, which means that the size of the printed pattern circulation cannot exceed 16 inches. The width of the flower tube should be slightly larger than the width of the printed fabric so that the fabric, including the edges, can be completely printed with the picture. Once ready, the printing drum can be used almost without restrictions, and there is generally no problem printing fabrics of millions of yards.

6、 Fixed color after screen printing and drum printing

Once the fabric passes through the screen or drum printing, the color is positioned on the fabric and further processing is required to fix the color.

Dyes used as printing pigments must be able to bond with fibers. Placing printed fabrics in steam at temperatures close to or sometimes exceeding the boiling point of water (high-pressure steaming) can be used for color fixation; This step is called steaming. After steaming, the fabric needs to be washed with soap to remove other substances used in the printing paste and color paste formula. Finally, the fabric undergoes several washing and drying processes.

The printing process requires a lot of water and heat energy consumption.

If pigments are used in printing instead of dyes, the fabric needs to undergo a dry heat treatment of up to about 210 ℃ to cure the resin of the fixed coating. This step is called baking and no further treatment is required. Printing with pigments instead of dyes can save a lot of water and energy.

The textile industry generally refers to fabrics printed with dyes as wet printed fabrics, while fabrics printed with pigments are called dry printed fabrics. This is because wet printed fabrics require steam steaming and subsequent water washing as part of the entire process. On the other hand, printed fabrics only need to undergo a brief dry heat baking as part of the coloring process, without the need for water washing treatment.

7、 Hot transfer printing

The principle of heat transfer printing is somewhat similar to the transfer printing method. When heat transfer printing, first use dispersed dyes and printing ink to print pictures on paper, and then store the printing paper (also known as transfer paper) for use in textile printing factories.

When printing fabrics, the transfer paper and unprinted paper are pressed face to face by a heat transfer printing machine. Under the condition of approximately 210 ℃ (400T), the dye on the transfer paper sublimates and is transferred to the fabric, completing the printing process without further processing. This process is relatively simple and does not require the necessary professional knowledge for roller printing or rotary screen printing production.

Disperse dyes are dyes that are specifically capable of sublimation and, in a sense, are dyes that are specifically capable of heat transfer printing. Therefore, this process can only be used on fabrics composed of fibers that have an affinity for these dyes, including acetate fibers, acrylonitrile fibers, and polyamide fibers (nylon)

And polyester fiber.

When hot handling printing, fabric printing factories need to purchase this type of printing paper from highly specialized printing paper manufacturers. Transfer paper can be printed according to the requirements of the game designer and the customer (ready-made drawings can also be used for transfer paper printing)

Hot transfer printing can be used to print clothing pieces (such as edge printing, chest bag embroidery, etc.), in which case special designed drawings are required. As a thorough textile printing method, heat transfer printing stands out from the printing process, thus eliminating the need for large and expensive dryers, steamers, washing machines, and tenters.

Due to the ability to inspect the printing paper before printing, it eliminates the occurrence of flower defects and other defects. Therefore, hot transfer printed fabrics rarely exhibit defective products. The production speed of continuous heat transfer printing is approximately 250 yards per hour.

8、 Eruptive printing and its development prospects

Spray printing is the process of spraying small droplets of dye onto a fabric in a precise position, using nozzles and graphics that can be controlled by a computer to create complex and accurate patterns.

Spray printing eliminates the delay and cost added by carving rollers and making mesh screens, which is a competitive advantage in the rapidly changing textile market. The eruption printing system is sensitive and fast, able to quickly transition from one trick to another. Printed fabrics are not subjected to tension (that is to say, they will not cause distortion in the picture due to stretching), and the surface of the fabric will not be rolled, thus eliminating potential problems such as fabric fuzzing or pilling. However, this process cannot print precise drawings, and the summary of the drawings is vague.

Nowadays, the eruption printing method is almost exclusively used for carpet printing and is not an important technique for clothing and textile printing. However, with the research and development of mechanical and electronic control skills, this situation may change.

Article source: Fancy Thread Manufacturer

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