Textile printing method
There are several methods of textile printing, of which there are two printing methods of commercial importance: screen printing and rotary screen printing. The third method is thermal transfer printing, the importance is relatively low. In recent years, the strong momentum of the development of digital printing, color and printing clarity is also increasing, from the original proofing mainly developed into mass production line. Other printing methods rarely used in the production of textiles include: wood stencil printing, wax valence (wax prevention) printing, yarn dyed cloth printing and anti-dye printing.
1, screen printing
Screen printing involves the preparation of a printing screen that was once made of fine silk, a process known as screen printing. At present, the silk screen is no longer used, but the printing process is still often used in the name of screen printing. Made of finely meshed nylon, polyester, or metal wire fabric tensioned on a wooden or metal frame. Mesh fabric to be coated with an opaque non-porous film. There are patterns, to remove the opaque film, leaving a fine mesh screen, this area is to print the pattern of the site. Most commercial screen fabrics are first coated with a light-sensitive film, and then remove the pattern by the Department of the film to reveal the pattern of the film. Place the screen on the fabric to be printed for printing. Pour the printing paste into the printing frame and force it to pass through the mesh of the screen with a scraper.
Each color in the print requires a separate screen for the purpose of printing different colors. For example, three sets of color printing needs three frame, the three colors were printed on the fabric up. In addition, the motif of each color in the motif must be accurately positioned on the screen so that the motif is correctly positioned after printing, avoiding the phenomenon that the green stem of a rose is printed in the middle of the red petals. Printed on flowers refers to all the colors printed on the fabric accurately industrial terms.
There are three ways to achieve screen printing, each method is basically the same application principle. The first, hand screen printing, was very common in the 1920s and is still widely used. Until the mid-1950s, manual screen printing was the only screen printing method until modern technology gave this process automation. The second method is called automatic screen printing (also known as flat screen printing and automatic flat screen printing). In the mid-1960s, with further developments, screen shapes developed from manual and automatic flat screen turning to round screen shapes. The third method is called circular screen printing or rotary screen printing, is currently the most widely used screen printing method.
2, manual screen printing
Manual screen printing is carried out on commercial long platens (platen up to 60 yards). Printed cloth roll smoothly on the platen, the platen surface pre-coated with a small amount of viscous material. The printing worker then continuously moves the screen frame by hand along the entire platen, printing one screen frame at a time until the entire printing is completed. Each mesh corresponds to a printing color. This method of production speed of 50-90 yards per hour. Commercial hand-screen printing is also widely used in printing well-cut pieces of clothing. In the garment printing process, garment processing and printing processes arranged together. Before the pieces are sewn together, the custom or unique designs are printed on the pieces. Because hand-screen printing can produce large meshes for large back flowers, fabrics such as beach towels, novel printing aprons, curtains and shower curtains can also be printed by this printing method.
Handmade screen printing is also used to print limited-fit, highly-fashioned women's apparel and print small quantities of products for market launch.
3, automatic screen printing
Automatic Screen Printing (or Flat Screen Printing) is the same as a manual screen except that the process is automated and therefore faster. The printed fabric is transported to the screen by the conveyor instead of being placed on the bench (like a hand-screen print).
As with manual screen printing, automatic screen printing is also a batch rather than a continuous process. In this process, the fabric is moved under the screen and then stopped. After the screen scraper is squeegeed and squeegeed, the fabric continues to move under the next screen with production speed of about 500 yards per hour. Automatic screen printing can only be used for the whole roll of fabric, cut a good piece of clothing generally do not have this method of printing. As a commercial process, the production of automatic screen printing (flat screen printing) is declining due to the preference for more efficient screen printing.
4, rotary screen printing
There are several important aspects of rotary screen printing that differ from other screen printing methods. Like the roll-to-roll printing, which will be described in the next section, rotary screen printing is a continuous process in which the printed fabric is conveyed by conveyor belts under moving cylinder sleeves. Screen printing, rotary printing the fastest production, greater than 3500 yards per hour. Use seamless perforated metal mesh or plastic mesh. The largest circular circle is more than 40 inches in circumference, so the largest flower size is larger than 40 inches. More than 20 sets of color rotary screen printing machine has also been produced, this printing method has gradually replaced the roller printing.
5, roller printing
Roller printing is like newspaper printing. It is a high-speed process that produces more than 6,000 yards of printed fabric an hour. This method, also known as mechanical printing, involves printing on a fabric by engraving a copper cylinder (or drum). Copper drums can be carved out of close arrangement of very fine lines, which can print very detailed and soft patterns. For example, fine, dense Pei Lisi vortex printing is a series of patterns printed by roller printing. Carved cylinder should be fully consistent with the designer's design artwork, each one needs a carved roller simple. In the textile-specific printing process, five-roll printing, six-roll printing commonly used to represent five sets of color or six sets of color roller printing.
Roller stamping is the least expensive mass-production method used, and yields have been declining each year in recent years because it is not economical if the lot size for each pattern is not very large. In most cases, roller preparation and equipment adjustments are costly and time consuming, making printing less economical with this method. However, roller printing is often used for printing with very thin line patterns such as the Paisley vortex print and the main printing pattern printed in large quantities for many seasons.
The size of the carved cylinder depends on the printing machine and the printing pattern. Most printers can be configured with a maximum perimeter of 16 inches of the cylinder, which means that the size of the printing cycle can not exceed 16 inches. The width of the cylinder should be slightly larger than the width of the printed fabric so that the fabric, including the edges, can be completely printed. Once ready, the printing cylinder can be used almost unlimitedly, generally printed millions of yards of fabric no problem.
6, Screen printing and roller printing after the fixing color processing
Once the fabric is passed through a screen or cylinder, the color is positioned on the cloth and further processing is required to fix the color.
Dye used as a printing colorant, must be able to combine with the fiber. Fix the printed fabric in a steam that is at or near the boiling point of water (autoclaving); this step is called steaming. After steaming, the fabric passes through the soap bath to remove the printing paste and other materials used in the paste formulation. Finally, the fabric after several washing and drying processes. In the printing process needs to consume a lot of water and heat.
If pigment, not dye, is used in printing, the fabric needs to be subjected to a dry heat treatment of up to about 210 ° C to cure the anchor coating resin. This step is called baking and no further treatment is required. Pigment instead of dye printing can save a lot of water and energy.
The textile industry usually refers to fabrics printed with dyes as wet printed fabrics, while fabrics printed with pigments are called dry printed fabrics. This is because wet prints require steaming and subsequent water washing. While the latter simply dry-roasted as part of the coloring process without the need for a water-washing treatment.
7, heat transfer printing
The principle of heat transfer printing is somewhat similar to the shift printing method. In heat transfer printing, a pattern is first printed on paper containing a disperse dye and a printing ink, and then the printing paper (also referred to as transfer paper) is stored for use by the textile printing plant.
The fabric is printed with a thermal transfer printing machine so that the transfer paper and the unprinted face are pasted together and passed through a machine at approximately 210 ° C (400T) at which the dye on the transfer paper sublimes and transfers To the fabric, to complete the printing process, does not require further processing. The process is relatively simple and does not require the specialized knowledge necessary in the production of cylinder printing or rotary screen printing.
Disperse dyes are the only sublimable dyes and in the sense are the only dyes that can be heat transfer-printed, so the process can only be used on fabrics that have affinity for such dyes, including acetate, propylene Nitrile fibers, polyamide fibers (nylon) and polyester fibers. At thermal transfer printing, the fabric printing plant purchases this printing paper from a highly specialized manufacturer of printing paper. Transfer paper can be printed according to the pattern designer's and customer's requirements (ready-made patterns can also be used for transfer paper printing).
Heat transfer printing can be used for printing clothing (such as border printing, chest bag embroidery, etc.), in which case to use a specially designed pattern. Heat Transfer Printing stands out from the printing process as a complete fabric printing method, eliminating the need for bulky and expensive dryers, steamers, washing machines and stenters.
As the printing paper can be tested before printing, so to eliminate the flowers and other defects. Therefore, thermal transfer printing fabric rarely appear defective.
Continuous thermal transfer printing production speed is about 250 yards per hour.
8, digital printing and its development prospects
Digital printing is the small droplets of dye jet and stay in the fabric of the exact location of the jet used to spray dye and pattern formation can be controlled by computer and can get complex patterns and accurate pattern cycle.
Digital printing eliminates the delays and costs associated with carving cylinders and making screens, a competitive advantage in the rapidly changing textile market. The digital printing system is flexible and fast and can quickly move from one pattern to another; the printed fabric is not tensioned (that is, it does not distort the pattern due to stretching) and the fabric surface is not rolled , Thus eliminating the potential problems such as fabric fluff or fleece, especially for small quantities, printing more varieties of printing patterns. With the development of technology, more and more printing color choices, higher and higher definition.