Discussion on the printing technology of the hotte

2022-08-05
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Discussion on the printing process of CD continued

2 Wire printing

2.1 selection of blade width

selection of blade width mainly considers two aspects. Consider from the frame: the basic condition is that the width of the scraper must be less than the frame before printing. The ideal condition for the frame is that the smaller the width of the scraper is, that is, the greater the distance between the left and right ends of the scraper and the frame is; Because in this state, when scraping, the cloth can be in soft contact with the substrate, and the extension of the cloth is also small. On the contrary, if the distance between the scraper and both sides of the frame is too small, the angle of the cloth at both ends of the scraper will be too large, resulting in the distortion of the shape, which is one of the reasons for the short service life of the frame

from the aspect of substrate: it is required that the width of the scraper must be 2 to 10 cm greater than the width of the substrate. The smaller the width of the scraper, the better. Generally speaking, the width of the scraper exceeds the size of the substrate by 3 to 5 cm on each side, so as to ensure the printing quality and leave a certain error margin. The width of the ink return blade should be wider than the width of the printing blade, and the lightweight material should be wider, so that the ink overflowed at both ends of the printing blade can be completely transported back

2.2 blade speed and angle

blade speed and angle mainly affect the amount of ink reaching the substrate through the cloth. High scraping speed leads to less and thinner ink penetration, while slow scraping speed leads to more and thicker ink penetration. However, if the scraping speed is too fast and the ink thickness is not enough, the printing pattern is easy to be unclear. If the scraping speed is too slow, it is easy to cause ink seepage and make the printing pattern not sharp enough. Generally, the printing scraping speed shall be adjusted according to the trial printing results at that time

the angle of the scraper also affects the ink output. If the angle is small, the ink output will be large. If the angle is large, the ink output will be small. Usually, the angle used is between 45 degrees and 75 degrees. During scraping, attention must be paid to the uniform speed and consistent angle, so as not to produce different ink shades in the same print

2.3 scraping pressure

scraping pressure can improve the technical level and utilization ability of existing products. First of all, silk printing does not rely on the pressure of the scraper to press the printing ink onto the substrate. Instead, it relies on the scraper to push the ink, generating a hydraulic effect inside the ink, pushing the ink through the hole, and achieving the purpose of printing by the adhesion between the substrate and the ink. Therefore, the printing press should be as light as possible, and the scraper surface is in line contact with the substrate. If the output voltage of the amplifier is unstable, otherwise the printing press is too large, causing excessive bending of the scraper tip, resulting in unclear printing patterns, or shortening the service life of the plate and increasing the consumption of the scraper. When the printing pressure is not enough, the pattern cannot be printed

2.4 ink

at present, the storage life of UV ink is not long, because UV ink is prone to gelatinization and deterioration. When using, pay attention not to let the ink expire. When using it within the warranty period, the inventory cannot be overstocked to ensure the quality of the ink

uv ink film thickness and transparency: the ink film thickness of the ink is too thick, which will also affect the speed of UV light irradiation and make the ink difficult to harden. As for the transparency of ink, transparent UV ink solidifies faster than opaque UV ink. In ink, the speed of UV light irradiation is not only faster, but also more uniform. At present, the fastest hardening color is blue in color four-color printing, followed by magenta and yellow. The hardening speed of black ink is very slow. The most difficult to harden is opaque white. Not only that, opaque white will turn yellow under the irradiation of UV light

3. other aspects

3.1 UV lamp tube

in order to fully dry the printing ink, the UV lamp must be designed with sufficient strength to completely dry the UV ink or varnish of the printed matter, and the printing speed, the thickness of the ink film and the brightness of the ink color also have a certain impact on the drying effect. In general, the type of printing machine and the selection of suitable UV lamps on the finished printing products should be considered when installing UV lamps

in multi-color overprint, if a dark color with high color concentration is printed on one or two overlapping colors, it will increase the difficulty of overall drying, because the UV light is quickly absorbed by the pigment of the deep ink. Generally, the drying difficulty of four-color UV ink is magenta, yellow, cyan and black

some colors are also very difficult to dry. For example, green is made of yellow and cyan; Opaque colors are also difficult to dry because they reflect UV light back. The same metal color, gold and silver also have the same problem

the lamp tube that is too old cannot dry UV ink or varnish, which will cause trouble in printing. Most of the instructions of the UV lamp indicate that the UV lamp must be replaced after about 1000 hours. In fact, if the printed matter cannot be completely dried at the normal printing speed, the replacement of the UV lamp must be considered to avoid affecting the overall printing quality

3.2 reflector

if there is no UV lamp reflector, about 80% of the UV light will not shine on the substrate due to diffusion. Therefore, the UV lamp must be equipped with a lampshade to reflect the UV light and focus on the surface of the substrate. The importance of the reflector cannot be ignored

the reflector must be cleaned and maintained, and it is best to maintain the same function as the new one. Some powder or dust generated during drying is easy to adhere to the reflector, which will affect the reflection effect of the UV lamp. The UV lamp shade should be cleaned frequently to prevent powder and dust from affecting the drying effect

(author: Guo Chaoran's products have been continuously upgraded)

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