The hottest pursuit of high quality silk screen pr

2022-09-19
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Pursue high-quality silk screen printing (Part 2)

reasons for printing accuracy deviation

1. When making multicolor overprint (halftone printing) plates, the plates are dried at different temperatures, resulting in printing accuracy errors

2. the tension of the version is low or the tension of the overprint (halftone) version is different

3. use a blow dryer to dry the plate unevenly

4. When making plates with too old, weak and deformed frames, the printing image will deviate due to the poor stability of the frames (these problems can be detected with negatives)

5. The spacing used in multicolor overprint is not the same

6. rubber scraping deformation

7. Affected by some factors, the size of the substrate changes

the cause of moire

· the wrong match between the halftone printing line and the number of silk meshes (the wire circumference should be 2.5, 3.75 or 6.25 times of the line)

· the angle between the halftone printing plate and the silk thread is wrong

· RZ value is too high (should be less than 8)

· the template is too thick or thin

· compared with the wire diameter, too small points will be lost (the point range should be 5-95%)

causes of color change

1. Ink consistency changes (different viscosities) due to solvent evaporation

2. Change the squeegee angle during printing

3. Change the scratch hardness during printing

4. Change the speed during printing

5. the rubber scraping edge is damaged

causes of premature damage of the template

1. Insufficient glue grease

2. Insufficient drying before exposure

3. Insufficient exposure time

4. The distance is too high

5. the ink return knife is too dry and sharp, and the pressure is too high

6. The wrong cleaning solvent is used for cleaning (including a small amount of water)

tensiometer

for silk printers, tensiometer refers to an instrument that measures and monitors the plate level during stretching or reuse. The unit of measurement is Newton per centimeter, which is simplified to N/cm

note: 1 Newton is the force measured by accelerating 1 kg of material, mainly high-end products, on an area of 1 square meter

thickness gauge

this instrument is mainly used in the following fields:

printed circuit board (PCB)

glass decorations

ceramic decorations

ceramic decals. The existence of these problems makes China's plastic machinery industry unable to meet the level of foreign plastic machinery as soon as possible

the industrialization of printing has few types, the core technology is immature, and the cost is high. The brush quality will depend on the control of the conditions of each factory during the actual printing

thickness gauges are increasingly used by all screen printing manufacturers certified by quality standards certification bodies

surface roughness measuring instrument

this instrument has been used in the engineering field for many years, and the silk screen industry was carried out in the late 1980s. The tester can display the flatness of the template surface. The symbol of surface roughness value is RZ, and RZ value is 0, indicating that the template is very smooth

surface humidity meter

in order to achieve the best results, the template needs to be completely dried before exposure. If it is not completely dry, the water contained in the photosensitive adhesive will cause the photosensitive agent to not be fully photosensitive, resulting in insufficient exposure of the template. What's more, the design concept of the testing machine will have the phenomenon of film falling off. The dryness of the template is difficult to judge. The contact hygrometer is an ideal test instrument, which can eliminate people's concerns about whether the template to be exposed contains moisture

ray detector

in the process of template exposure, two important parameters need to be controlled: the energy of UV light and the distribution of light in the template area. Although most high-quality exposure machines are now equipped with optical integrators to compensate for the wave to UV output, it is not easy to measure the distribution of incident light and the state of UV radiation density

when the density of light in the center of the exposure frame and the farthest corner is at the same level, it indicates that the ideal distance has been achieved

when using this measurement timing, you need to wear UV proof glasses and do not prolong the unnecessary exposure process

source: China Packaging News

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