The silk-drawing phenomenon of screen printing refers to the phenomenon that during the screen printing process, when the squeegee scrapes over the screen and bounces up, many thin and long ink threads appear between the screen and the substrate. These threads do not break normally, but remain on the printing surface in a filamentous form, resulting in irregular burrs or fibrous marks on the edge of the printed pattern.
Causes of the silk-drawing phenomenon
The viscosity of the ink is too high
The viscoelastic properties of the ink are the key factors leading to the silk-drawing phenomenon. When the viscosity of the ink is too high, its fluidity becomes poor. After the squeegee leaves the screen, the ink cannot rebound and break quickly, but remains on the surface of the substrate in a filamentous form, forming silk-drawing.
The ink dries too fast
The ink dries too fast, causing the ink to solidify quickly after the squeegee leaves the screen, and it cannot break normally, thus forming silk-drawing. This phenomenon is particularly obvious in high temperature or low humidity environments.
Improper pressure or angle of the squeegee
If the pressure of the squeegee is too low or the angle is improper, the ink may not be able to completely fill the holes in the screen, or the ink may be unevenly distributed during the scraping process, which may cause the silk-drawing phenomenon.
Screen tension or aperture problem
Insufficient screen tension or excessive aperture may cause the ink to not pass through the screen normally during printing, resulting in drawing. In addition, if there is foreign matter or damage on the screen surface, it may also affect the normal transfer of ink.
Environmental factors
Excessive ambient temperature or low humidity may cause the ink to dry faster, thereby increasing the probability of drawing. In addition, dust or impurities in the environment may also adhere to the screen or substrate, affecting the printing quality.
The impact of drawing
Degradation of printing quality: Wire drawing can cause irregular burrs or fibrous marks on the edge of the printed pattern, affecting the appearance quality of the printed product.
Reduced production efficiency: Wire drawing may require frequent shutdowns to clean the screen or adjust printing parameters during printing, thereby reducing production efficiency.
Increased material waste: Wire drawing may cause unqualified printed products, increase material waste and production costs.
Solution
Adjust ink viscosity
By adding diluent or selecting ink with appropriate viscosity, reduce the viscoelasticity of the ink to ensure that the ink can rebound and break quickly after the squeegee leaves the screen.
Control the drying speed of ink
Appropriately adjust the drying speed of ink to avoid premature curing of ink during printing. This can be achieved by adding slow-drying agent or adjusting the ambient temperature and humidity.
Optimize scraper parameters
Adjust the pressure and angle of the scraper to ensure that the ink can evenly fill the holes of the screen and transfer normally during the scraping process.
Check the status of the screen
Regularly check the tension and aperture of the screen to ensure that the surface of the screen is clean and free of foreign matter. If the screen is damaged, it should be replaced in time.
Improve environmental conditions
Control the temperature and humidity of the printing environment to avoid the influence of high temperature or low humidity environment on the drying speed of the ink. At the same time, keep the environment clean and reduce the interference of dust and impurities.