In the past ten years, my country’s printing and dyeing industry has made great progress. In 2001, the total output of printed and dyed fabrics in the country was 17.9 billion meters, and in 2010 it reached nearly 60 billion meters. Relatively speaking, the development speed of printing products is slow. Due to the high technical content of printing, there are many factors that are affected. Many customers report that there are many good printing orders, but few printing and dyeing factories that do well. There are both technical problems here. There are also management issues. For printing processing and production, being able to better express the concept and spirit of pattern design is the goal that printing workers should pursue. The key is how to improve the sample accuracy rate.
An accurate copy of the printed product and the original Rate
Textile printing is a combination of artistic creation and production technology. A designed printing pattern will become a colorful printed fabric after a certain technical process of printing production. Whether the printing effect of printed products meets the original design requirements is an important factor in determining the appearance quality of printed products. The accuracy rate can be considered from three aspects.
1. Original compliance rate
Put the paper or fabric on The pattern should be expressed on the processed fabric to the maximum extent, and it must first conform to the original spirit. To embody the spirit of the original, we not only pursue copying the original, but also strive to achieve and surpass the printing effect of the original sample according to the characteristics of different patterns. The printing process is also an artistic creation process.
Realistic patterns: Flowers are generally the main subject. Pay attention to the vividness of the flowers, the natural shape, the florets, the branches and leaves, which are flexible and full of vitality, and can be used to avoid joint obstruction.
Regular patterns: generally represented by geometric patterns and imitation color woven strips. It is usually composed of many points, lines, and surfaces of the same size and shape and arranged regularly. This type of pattern strives to have smooth, fine lines and reasonable distribution, and pay attention to vertical printing. This type of pattern has very high requirements on the weaving quality of the fabric itself.
Exaggerated patterns are generally based on cartoon animals and characters, supplemented by various object shapes. In order to increase the artistic appeal, the patterns have been exaggerated. When examining this type of pattern, pay attention to whether it reflects the boldness and flexibility of the pattern.
Hazy patterns: Generally abstract hazy patterns, such as imitation tie-dye, imitation batik, imitation water stain, and the colors are superimposed on each other. This type of pattern focuses on testing whether the overlapping effect is uniform, rich, and layered.
The color combination of the pattern also reflects the design spirit of the pattern, and the original compliance rate includes the accuracy of the color. The color light must be accurate, there are two aspects: the color difference from the original color and the color difference of itself. Generally speaking, printing pays more attention to the overall effect. Individual colors have lower requirements than dyeing, but the main color must be accurate. Large surfaces can be inspected using computerized color measurement, but at present, visual judgment is mainly relied on.
2. Printing level
From the perspective of printing production, printing The level of production can generally be measured by the amount of color given to the surface, the uniformity of the block surface, the clarity of the outline, the smoothness of the lines, the sense of layering, etc.
Surface coloring amount: Printing is surface coloring, so the coloring effect can often be measured by the level of surface coloring. The level of coloring refers to the same amount of dye printed on the fabric. The depth of the resulting surface color. There are many factors that affect the amount of color given to the surface, including dye properties, paste rheology, fabric structure, pre-treatment quality such as wool effect, smoothness, etc., printing machine operation, etc. A spectrophotometer with a reflective device can be used to measure the K/S value of the printed surface for quantitative expression.
Due to the small area of the printed pattern, it is difficult to determine the K/S value. This test method is mainly used as a basis for comparative testing when selecting dyes, pastes or printing processes. The evaluation of the apparent coloring amount of printed fabrics is mainly based on visual inspection. If the color is full and bright, the surface coloring effect is good, otherwise it will be poor.
Block surface uniformity means that the color of large blocks on the ground is uniform and there is no blooming phenomenon. Since printing is surface coloring, for dark printing on tighter fabrics, block surface uniformity is an important indicator to measure the level of printing. It mainly depends on the quality of fabric pre-treatment and the choice of paste. Since the uniformity of dyeing is much better than that of printing, the printing effect will be better if the anti-discharge printing process is used for dark all-over printing fabrics with tighter fabrics.
Outline clarity: refers to the degree to which the pattern pattern is accurately displayed on the fabric. There is no bleeding phenomenon in the pattern, and there is no third color between opposite colors such as red and blue, yellow and blue, etc. To obtain good printing contour clarity, choose a paste with good rheology and water-holding properties. Reasonable color separation should be made between opposite colors when making plates. If it is difficult to solve the problem due to equipment limitations, anti-printing or anti-pull (pull-out) methods must be used. ) dyeing process.
Line smoothness: Lines (including straight lines, diagonal lines, horizontal lines, and wrapped lines) are smooth but not empty, and there are no zigzags during screen printing. The smoothness of lines depends largely on the plate-making (engraving) technology. If screen printing is used, the mesh number must be high. Secondly, it is closely related to the rheology of the selected paste. The paste should have good shear thinning and mesh permeability. Finally, it is also related to the printing operation.
Hierarchical feeling: mainly refers to the uniform and full gradient of moiré or halftone (HalfTone), without hard edges or moire lines, reflecting a good three-dimensional effect, that is, a sense of layering, giving people a sense of layering. A beautiful enjoymentThe process conditions are inconsistent; the printing operation is not standardized; the pulp level, speed, pressure, and drying temperature in the web are unstable or even change randomly; the humidity changes greatly during steaming.
White ground contamination: The white ground or white pattern on the fabric is stained with other colors, causing the white to not be white, which directly affects the overall printing effect. The main reasons: the dye itself has a low fixation rate or the dye concentration is too high (such as green blue, scarlet, black, etc.); the dye has been left for a long time and hydrolysis occurs: the evaporation time is insufficient and the dye is not fully fixed; the post-treatment washing process is unreasonable; Not choosing the right detergent.
Many abnormalities in printed fabrics are related to plate-making methods and processes. Although traditional manual color separation has been basically eliminated, practitioners’ ability to master computer color separation software is especially important. There is a big gap in processing some complex patterns; abnormalities caused by improper plate making operations also often occur. The reasons for poor printing effects and corresponding adjustments are analyzed as follows.
① It is not allowed to match flowers
It is not allowed to match flowers except with In addition to the operating technology and the accuracy of the printing equipment, it is also directly related to color separation and plate making. If there is a regular pattern of inaccuracies in patterning, and it is related to the circumference of the rotary screen or the length of the screen frame, it may be a problem with plate making or screen making. It may also be that there is a problem with the mesh frame or the rotary screen is not round or the frame is deformed; if the pattern alignment is inaccurate and irregular, and the times are good and the times are different, it is generally caused by the small color match between colors during plate making.
Adjustment measures: Increase the temperature or extend the time when the rotary screen is restored; the blank screen of the same manufacturer should be selected for a set of patterns; the rotary screen bulkhead should be calibrated before use; check the flatness frequently Whether the net frame is denatured; align and align the cross when making the net; the relationship between colors should be reasonably handled according to the rheology of the color paste and the tissue specifications of the fabric.
② Poor pattern edge definition:
Flat screen printing (Exposure) The contact between the film and the screen printing plate is not true or the distance between the printing light source and the screen printing plate is large; the mesh number of the screen is low; the photosensitive adhesive is unevenly coated and the drying is insufficient. Adjustment measures: When printing the printing plate, increase the The vacuum air pressure value increases the closeness between the film and the screen, and reduces the distance between the printing light source and the screen; uses a high-mesh screen; improves the coating quality and coating uniformity; increases the development time, and performs adequate cleaning .
③ The pattern lines are not smooth and produce a zigzag phenomenon
Screen The mesh number is improperly selected or the exposure is insufficient, and light is diffracted during exposure; the thickness of the photosensitive film is not enough; the tension of the flat screen is uneven; the water pressure is too high when the screen is developed.
Adjustment measures: According to the accuracy of the pattern, select a screen with an appropriate mesh size. It is best to use a colored screen to prevent light diffraction during exposure; use multiple and even coatings of photosensitive glue. The method is to increase the thickness of the glue layer, but too thick will also affect the smoothness. Some studies have suggested that if the thickness of the glue film is greater than 25% of the wire diameter, the edge finish of the pattern will be better; increase the tension and uniformity of the stretch net; and reduce the flushing pressure during development.
④ Moiré is produced during the plate making process
On the flat screen When stretching the screen, use a positive stretch screen for color printing; when making the plate, the angle between the direction of the screen lines and the warp and weft wires of the screen is incorrect; the mesh number of the screen does not match the number of screen lines; the difference in the screen angle of each color plate non-compliant.
Adjustment measures: Generally, diagonal stretch mesh should be used for color printing; correctly grasp the direction of the screen dots and the angle between the warp and weft wires of the screen; the mesh number of the screen and the screen lines The number matching must be appropriate. For flat mesh, the mesh number should be 4-6 times larger than the screen line number, while for circular mesh, 1.5-2 times larger is more appropriate. For the screening angle of each color version, 45º is used for the single-color version. The main color screening angle is 45º, and the secondary color screening angle is 15º. </p
