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Under the application characteristics of silk printing in metal packaging

2. Design requirements of metal packaging silk printing

the most important thing in any work is the initial basic work. The design with silk printing as the main process should not only follow the principle of economy and practicality, but also pay attention to the combination of science and technology. Under the condition of ensuring the accuracy of the contents and the reasonable layout, the decorative patterns are properly added to organically link the characteristics of silk printing with the optical color of the strain gauge sensor, which is the force sensor most commonly used in aesthetics and materials. It has become an important design idea for making the package appearance with silk printing technology

⑴ since the wire brush is not easy to express the effect of fine lines, there should be space or overlapping parts at the adjacent or joint of two colors, and the width of lines and the size of handwriting should exceed the maximum resolution of plate making by more than 0.1mm

① when designing the color block printing, on the condition that the size and shape of the inner frame are accurate, the size of the outer ink frame shall be as large as possible to ensure that the inner frame is not touched during sealing

② when the adjacent color zones do not require space, they shall be designed separately and arranged twice. These are two color zones with different shapes, and no gap is required in the middle

③ at the intersection of two color blocks, it is not easy to print very well. This situation can be compensated by overlapping design, and an outer frame is added outside the color frame. It is also necessary to design the secondary lighting separately. The surrounding size of the color block area should be slightly larger than the size required in the drawing, that is, when two colors are adjacent, the light color area should be designed to be larger and printed first, and the dark color printed later should be pressed onto the light color to prevent gaps in the middle

⑵ in case of appearance requirements with more contents, whether it is multi-level overprint or multiple color block printing, the layout will appear messy. Although it is colorful, it will lose the sense of elegance and solemnity. According to the principle that the density of points reflects the depth of hue, the adjacent parts in the complex area are printed with the same color with points of different sizes, shapes, or densities, so as to seek changes in consistency. Due to one-time design, one-time photo arrangement and one-time printing, the trouble of multiple positioning and printing is reduced and the efficiency is improved. It can not only play the role of color block division, but also make the color style of the layout conform to the aesthetic trend of the times, and skillfully integrate the functional beauty with the artistic beauty. The packaging and printing are well matched, comfortable and modern. It fully shows the value of the product

⑶ emphasize decorative effect. For those printing surfaces with simple contents and large space area, properly match with color blocks of different shapes, and add decorative decorations of lines, which will make the monotonous and boring simple contents lively and bright

⑷ select the appropriate font. Character design, Chinese, Chinese Pinyin, English and numbers are commonly used languages for packaging patterns. Character design not only requires to meet the needs of content functions, but also must have good craftsmanship and aesthetics. Most Chinese characters use Song typeface, imitated Song typeface, and wiped typeface. The Chinese phonetic alphabet and English mostly use normal typeface, long isoline typeface, flat isoline typeface, etc. Numbers are the most common symbols. The ratio of height and width directly affects the recognition effect. Height: width is generally (5:3) ~ (3:2). The commonly used Song typeface, due to its square font, obvious brush edge and unequal thickness in horizontal and vertical directions, will appear thin when printed on the metal packaging when the word body is less than 4.2mm, and the printed title will also appear light drift; The imitation Song typeface has the same horizontal and vertical thickness, clear shuttle angle, beautiful font, and good effect in printing small characters or titles. When the body of the characters is above 4.8mm, the bold characters are mostly used. The characters are dignified and generous, and the strokes are thick. The printing on the packaging looks strong and eye-catching. When the title or space is large, the square Song typeface or deformed regular script can be selected, which makes it look broad, bold and calligraphic after printing

in a word, the selection of words should conform to the process characteristics of silk printing, and after printing, it should be stable, even, thin, easy to read and easy to distinguish

(5) select standard symbols. The nominal value of some products is usually indicated by English letters or various symbols, such as kg, relevant units: mm, l, Ω φ For the sake of accuracy, we try to use standard symbols for direct mapping. Generally, the commonly used Chinese characters do not need to be handwritten. Instead, the characters on the letter board are put into a positive film as required, pasted onto the drawing, and then turned into a negative film to ensure the consistency of the whole board font

⑥ seriously treat each drawing, actively discuss with the user on the premise of respecting the user's wishes, then the embedded parts of this batch of test pieces are the re creation of the art of the unqualified manufacturer, apply the mature techniques and unified image to different products, and establish their own style

⑺ take seriously the weak links in overprint patterns. The technological level is the technical basis to ensure and express the design level, and also the guarantee to create the product texture beauty and enhance the formal beauty. Therefore, silk printing should also prevent rough manufacturing and damage the appearance image. It is often found that the same negative has different products printed by different manufacturers. There are technical differences, as well as differences in color matching and material selection, and more importantly, differences in process quality

(8) according to the design sketch provided by the user, carry out proofing drawing, engraving or mapping, and then carry out plate making. Since the microcomputer has been used in the design system, the microcomputer design and photolithography are relatively advanced technologies, and the designed dimensions are also relatively accurate. Without advanced equipment, drawing, mapping and engraving can also be used for products with low requirements

III. quality characteristics and requirements of metal packaging wire printing

in terms of technology, the printed patterns and lines must be clear and the ink layer must be full, which is related to a series of printing data such as the number of wire mesh, tension, printing pressure, printing speed, ink viscosity, etc

1. Carefully select the silk

determine the silk according to the printed characters and lines, and generally use 300~350 mesh silk. Although better printing effect can be obtained by using more than 350 meshes of silk, due to the thin ink layer, the anti-corrosion ability of the drilling plate will be weak in the subsequent process. The selected silk shall be tightened under 8 tensions, and the glued frame and glue surface shall be placed upside down on the tightened silk surface for reverse tension, so as to tighten several small pieces at the same time and save silk. The frame can also be arranged at any angle to avoid right angle tension and reduce the chance of sawtooth when printing

2. Stretching

when printing general graphics, manual stretching can be used, which saves both money and labor. When printing complex or detailed graphics, the tension first affects the printing accuracy. If the tension is too small, almost all the consequences are unclear printing. Therefore, mechanical or pneumatic tensioning must be adopted. When stretching, the tension should be gradually increased. Do not pull to the required tension at one time. The wire shall be leveled evenly. When the tension is reached, it shall be left for several minutes before bonding. It is best to let the stretched one stand for 3~4 days, place it flat on the desktop or other places that are not easy to touch, and use it after the tension is uniform

3. Silk degreasing treatment

wet the silk with running water, apply washing powder or detergent on both sides of the silk, and scrub with a brush, which can not only remove the fingers, but also coarsen the silk. The alkaline detergent must be washed under running water, otherwise it will affect the quality of plate making

4. Drying

dry the washed silk in a ventilated and dust-free place or in an oven. The drying factor should not be too high to avoid affecting the deformation of the silk

5. Plate making

as silk printing requires clear patterns and characters. The ink layer is full, which requires a high-quality version. First of all, two situations should be excluded: the first is that the photosensitive film is too thin, and the printed patterns and lines are not only unclear, but also jagged, scattered lines, and blunt edges and corners; The second is that the photosensitive film is too thick. Although great pressure is applied during printing, the ink layer is still very thin, and the lines are seriously broken, which can not withstand the corrosion of liquid medicine. Therefore, the thickness of photosensitive film on 350 mesh silk is better than that of 242 scraping method. Among them, the scraping speed and the inclination of the scraper are also the main factors affecting the film thickness. The glue scraping speed should not be fast. Moving the scraper slowly can not only eliminate the bubbles in the glue solution, but also obtain a uniform photosensitive layer. The included angle between the back of the scraper and the wire is 25 °. The force of both hands should be uniform when scraping

it is worth mentioning that the printing accuracy of plate making with photosensitive adhesive is not as high as that of capillary film, but the printing resistance of film is not as good as that of photosensitive adhesive. So immediately after the coating of photosensitive adhesive, stick a piece of polyester film on the non printing surface, and use the scraper to press and scrape twice to drive away bubbles and prevent pinholes; Then it is put into the oven for low-temperature drying, and the temperature is controlled within 40 ℃; After drying, take out the silk, remove the polyester film, and then dry it for 1~2 minutes to expose. This method of "changing" the film film with photosensitive adhesive can improve the printing accuracy of silk

6. Exposure

most of them adopt solar exposure. Exposure shall be conducted for 30~45 seconds according to the content of photosensitizer. Before exposure, the negative film shall be inspected and cleaned to remove dust and stains. If the wire is facing up and the frame is facing down, a piece of black paper or blue carbon paper shall be clamped between the liner and the wire to prevent light refraction, resulting in unclear patterns or difficult development

7. Development

after the exposure, the development shall be put into operation immediately, and the plate shall be soaked in 30 ℃ warm water for 1~2 minutes, and the unexposed film shall be sprayed with tap water until the pattern is clear

8. Drying

absorb excess water with a sponge and dry it naturally under the ventilated sun or in a 40 ℃ oven

9. Revision and sealing

proofreading and revision with negatives, closing the holes outside the pattern and drying, which can be delivered to the printing process

10. The printing

adopts self drying corrosion-resistant printing ink to keep the distance between the plate and the metal packaging surface 3~4 mm; The scraper is required to be sharp, straight and without notch, and scrape from front to back. The scraper is inclined at an angle of 45 ° and parallel. It is not suitable to scrape ink too fast. Try printing for about 10 times. If the ink leakage is normal and the pattern is clear, batch printing can be carried out. In order to reduce the workload of the patched version, it is better to check the printing quality every 10 times so as to correct it in time. Often due to the dry environment and serious dust, white spots and hazy lines appear on the printing plate, which is mainly caused by the particles in the dust and ink. Wipe the dirt with cotton wool dipped in an appropriate amount of diluent. After printing, the edition shall be cleaned in time. Generally, propionic acid cleaning solution is better. When it is irritating to the skin, the ink stuck on the surface is easy to wash away. The cleaned version shall be wrapped in time and properly placed for reuse

11. Maintenance of printed parts

the printed parts shall not be directly corroded. After the printing ink is completely dry, carefully inspect and repair the deficiencies in the printing plate by plate; The places to be filled shall be repaired with plate making glue, and the unclear characters shall be modified with iron pen; Self inspection, mutual inspection and special inspection shall be carried out to control the deficiency of printing quality at a minimum, and then the next process can be carried out

12. Reasonably select ink

for multi-color overprint in layers, the next color shall be printed only when the previous color is dry enough to resist sticking. Once the latter color is damaged, do not rub the background color when erasing it. In order to ensure the yield and reduce the repair difficulties, the ink types and diluents are screened

when the background color on the surface of metal packaging is light, UV white ink can be added to resin ink for color matching to ensure uniform color matching. After printing, the color ink particles will be firmly embedded due to the curing of UV ink. The surface will not become sticky, and the next color can be printed immediately. The next color ink can be thermosetting metal ink, which is heated and cured after printing. Not only can we get the reason

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