Talk about color screen printing

Talk about color silk printing

If silk printing is limited to printing simple lines and words, it cannot meet people's increasingly demanding decorative requirements. Today, silk printing begins to dabble in the field of color. Needless to say, color printing on special substrates such as plastic bottles and metals has also become common. The main difference between color printing and general line text printing is that it is no different from other printing processes. The evaluation standard is to see whether the original can be truly restored

1 sample analysis

customers often provide samples for the manufacturer to design the scheme. He simply explains his intention to you, and most tasks are completed by you. It is important to understand his intention. Many disputes arise because you don't really understand his real idea. You also need to make clear the type of sample material and determine the printing process. Sometimes customers know the material type, but most of the time they don't. You can identify it according to your own judgment. The type of material also determines the selection of printing parameters, such as the number of lines added, the number of wire mesh, prepress treatment, scraper hardness, with the reduction of production capacity, the cancellation of ground bar steel, the liquidation and finishing of electrolytic aluminum, peak staggering production and other measures to increase efforts

2 choosing ink

choosing ink is difficult and simple. You may be proficient in the adaptability of ink to printing materials, and know what resin ink contains. If the adaptability of ink to printing materials is good, it will be discarded directly. However, the division of labor in society doesn't care how much you know. You often just need to choose according to the information provided by the ink manufacturer at hand. You just need to verify the authenticity of the size of the sample used. Ink may be suitable for most occasions, but there are exceptions in some special cases. You might as well prepare several kinds of inks for testing

for the selection of ink, we should first have a simple understanding in theory, and the key is to test according to the existing ink varieties. Silk screen printing inks mainly include the following brands. Coats inks is a famous ink brand produced by British Goss brothers, which has established the authoritative position of solvent based inks in the long-term production practice. As an environmental protection product, you must be familiar with the product "Dolby UV ink" of French Dolby company. Although Dolby is small, it is the leader in UV ink. From the initial silk printing ink and pad printing ink to UV credit card ink and offset printing ink, Dolby has a good performance. Apollo ink is famous for its bright colors. It has been widely praised in terms of current ink varieties and adaptability. If you want to print on metal products and glass products, when you first choose Apollo ink, the quality of German ink has always been the best in the world. The leading level of printing technology has created excellent system quality, which of course includes ink resin and pigment. Up to now, German ink still maintains the world record of fineness and adhesion. In the special printing field, you can't help but pay attention to malabu ink of malabao company. "Supreme" is a special ink launched by Henghui Industrial Co., Ltd. to develop the mid-range market. We advocate quality, but pay more attention to effect. The plastic printing products printed with it even make you suspect that it is printed with European ink

3 considering the curing process

most inks used in plastic substrate materials are volatile and dry. After the solvent contained in the solvent based ink evaporates, the ink is fixed on the substrate. However, some printing requires drying devices to dry the ink, especially for metal, ceramic and glass printing, which generally requires drying devices. It is very important to configure the drying device. When using UV ink printing, we should consider the curing device and equipment. UV ink does not contain solvent and can be cured only under UV irradiation. Both drying device and UV curing machine can dry quickly. If the curing degree is too low, the ink layer will show poor adhesion and gloss; If curing is excessive, the ink film will be brittle and easy to crack and deform

4 about printing color sequence

color printing copies the rich color and hierarchical information of the original through the superposition of four primary colors. In theory, the complete transparency of the ink can ensure the true restoration of color, but the ink is composed of resin binder and pigment, so the resin cannot be completely transparent, and the pigment itself also has a certain hiding power. These factors ultimately affect the color

the stacking order is related to the transparency of the ink. The ink with low transparency has strong hiding power, so it should be printed first. At first, the transparency of yellow ink was the worst. It was necessary to print yellow ink first. Now the situation has changed. It doesn't matter that yellow ink is printed first and then printed. Theoretically speaking, except for the difference of hue, other indicators of four primary color inks should be as close as possible. In fact, it is another case. The saturation of cyan has a great impact on the color of printing. The high saturation of cyan makes the printed matter tend to cold tone. Therefore, when the saturation of cyan is high, cyan can be placed in the color sequence earlier. The function of black is to increase the outline of printed matter. If the graphics and texts have high requirements for contrast, then black is printed finally. The density of black also affects the printed matter. Too high density will cover some layers, so the black ink with higher density can be printed in the first color sequence, and the black ink with lower density can be printed in the last

5 determine the number of stitches

the higher the number of stitches, the more rich levels can be copied, but too high the number of stitches will bring difficulties to silk printing. To determine the number of lines, we should first consider the visual environment, that is, from what distance to observe this image. Visual distance should be the most basic standard to determine the number of lines. The closer the visual distance is, the higher the number of lines can be added, which can improve the clarity. The farther the visual distance is, the lower the number of lines can be appropriately added, which can reduce the printing difficulty. Sometimes customers don't understand the characteristics of silk printing and blindly ask for unnecessary extra lines. You should persuade them to change their minds. Bioisoprene is a new raw material produced by fermentation technology from biological raw materials. The reproduction range of silk printing is usually below 80 mesh. Printing with too many lines will lose points in the highlight area, and the details cannot be reproduced. In addition, too many threads will make it difficult to choose ribbons. According to the usual selection method, the number of wire mesh should be 4 times the number of lines added to the print film. Too high number of lines will cause the ink layer to be too thin, and the contrast between pictures and texts will be reduced, which will also affect the expressiveness of the image

as the number of lines increases, the dot size decreases until the dot cannot be printed. Unlike offset printing, silk printing can copy 3% - 98% of the points. Strictly speaking, it can only copy 15% - 85% of the points. Points higher than 15% will be lost, and points lower than 85% will expand into the field. For originals with very fine levels, level correction and level compression are required after scanning into the computer before they can be restored. The compressed image highlights and dark dots are easy to reproduce under a given number of lines. Of course, hue range transition compression will lead to the loss of some details of the image

6 determine the output resolution of the film

if the output resolution (DPI) is set too low, the film will appear sawtooth phenomenon. If the resolution is too high (the number of lines remains the same), the level of print film is richer, but the gray level will multiply, and the replication ability of silk printing is limited, which even makes silk printing impossible. Practice has proved that silk printing is difficult to copy more than 100 lines of printed matter. Of course, the development of technology promotes the progress of silk printing, and this conclusion is not absolute

7 select wire

the wire should have the same number of lines and balanced tension in the warp and weft directions, otherwise it will cause moire and inaccurate overprint. The wire parameter index shall include wire diameter, wire mesh number, tension curve and wire thickness

(1) select low mesh silk for rough graphic printing, and high mesh silk for fine graphic and hierarchical printing

(2) the number of wire mesh should be selected to match the number of wires added to the print soft version. Generally, 4 times the number of wires added to the print soft version is used as the number of wire mesh

(3) for UV ink, considering the curing effect, the number of wire mesh should not be too low

(4) dyeing silk is preferred for fine graphic printing and hierarchical printing, and the resolution of dyeing silk is much higher than that of white silk

(5) the mesh selection calculator can help you obtain data support and determine the relationship between static and dynamic mesh numbers

8 set the printer stroke

first install the substrate, then hold the scraper by hand and move on the surface of the substrate. When the position is appropriate, fix the stop. For curved wire printers, the travel of the adjusting plate should exceed the perimeter of the plastic bottle. Proper travel can save time, increase printing speed, reduce ink discontinuity, and print good points

9 select the doctor blade

generally, the length of the scraper is about 5~10mm longer than the length of the image. The choice of doctor blade involves hardness and shape. The scraper with high hardness can carry out very fine graphic and hierarchical printing; The soft scraper is suitable for the substrate with very rough printing surface, and the printing ink layer is also relatively thick. Sharp scrapers are often used for surface printing, and scrapers with rectangular sections are often used for plane printing

10 selection box

aluminum products are preferred as the frame material. It is relatively light and has high strength. It is suitable for printing hierarchical images, especially four-color printing. Frames with good rigidity must be selected. Many frames used in special printing industry belong to non-standard parts, which is caused by the strange shapes of the substrate of special printing. It is very important that many special frames can be free from the constraints of the silk printing machine when completing the silk printing task. A very important aspect of the selection box is that it can maintain tension balance in the printed image area

frame manufacturing is also an aspect to be considered. The frame should be as hard as possible and have good bending and twisting resistance

11 determine the distance

distance is the distance between the plate and the substrate surface. Setting the distance too large or too small will change the size and accuracy of the image

under any tension, too high a distance will cause the image to expand. Under high tension, the separation speed between the wire and the substrate is faster than the running speed of the scraper, which will cause the deformation of the scraper. Too high distance will also cause serious damage to the wire. The paste is not impeccable, and it may also fall off due to excessive tension

too low a distance will make it difficult to separate the plate from the substrate. The separation speed between the silk and the substrate is slower than that of the doctor blade, which will leave marks and cause scuffing. The correct distance should ensure the rapid separation of the silk and the substrate. The selection of pitch is related to the wire tension. For high tension wire, a lower pitch can be selected, and for low tension wire, a higher pitch should be selected. Generally, this data is between 2~3mm

12 printing

color silk printing should first pay attention to overprinting. Only when overprinting is accurate can we get good prints. To achieve accurate overprinting, first of all, the tension of the silk plate should be basically the same, with an error of less than 1n/cm. Use a wire tensiometer to measure the tension of each plate, which should be kept at 18n/cm. The uniformity of the positioning device is very important. Each substrate must have the same position when entering the printing, otherwise it will cause inaccurate overprint. The ink for four-color printing is four primary color ink. Choosing an ink that meets international standards can avoid the problem of incorrect color

the establishment of testing standards for color products is conducive to the implementation of institutionalized management, avoiding manufacturers and customers