Discussion on common problems in the hottest scree

  • Detail

Discussion on common problems in silk printing

the causes of silk printing failures are various, involving many factors, such as silk screen printing plate, silk screen scraping, silk screen printing ink, silk screen printing equipment, silk screen printing materials and operation technology. There are single reasons for silk screen printing failure, but it is more the result of the cross influence of complex reasons. This is what the operator should pay special attention to when determining the cause of the fault and taking corresponding countermeasures

I. paste plate

paste plate is also called blocking plate, which refers to the phenomenon that the ink cannot be transferred to the substrate in the through-hole part of the silk printing plate during printing. The appearance of this phenomenon will affect the printing quality, and even fail to print normally in serious cases

The reasons for the paste phenomenon in the process of silk printing are complex. The reasons for paste can be analyzed from the following aspects

① reasons for substrate. Silk printing substrates are diverse, and the texture characteristics of substrates are also a factor in the paste phenomenon. For example, paper and wood. Fabrics and other substrate surface smoothness is low, surface strength is poor, in the printing process is relatively easy to produce powder, wool phenomenon, resulting in paste

② reasons for workshop temperature, humidity and ink properties. The silk printing workshop is required to maintain a certain temperature and relative humidity. If the temperature is high and the relative humidity is low, the volatile solvent in the ink will evaporate quickly, and the viscosity of the ink will become high, thus blocking the hole. Another point that should be noted is that if the downtime is too long, there will also be a paste phenomenon. The longer the time, the more serious the paste. Secondly, if the ambient temperature is low, the ink fluidity is poor, and it is easy to produce paste

③ reasons for silk screen printing. The prepared screen printing plate can be used only after it is washed with water and dried before use. In 2015, the world will have 5million new energy vehicles. If the good version is placed too long and not printed in time, it will more or less adhere to dust in the preservation process. If it is not cleaned during printing, it will cause paste

④ causes of printing pressure. During the printing process, too much embossing force will bend the scraper. The scraper is not in line contact with the screen printing plate and the substrate, but in face contact. In this way, the ink can be scraped clean every time, leaving residual ink. After a certain period of time, the film will form a paste

⑤ reasons for improper clearance between screen printing plate and substrate. The gap between the screen printing plate and the substrate cannot be too small. If the gap is too small, the screen printing plate cannot be separated from the substrate after scraping. When the screen printing plate is lifted, a certain amount of ink is adhered to the bottom of the printing plate, which is also easy to cause board pasting

⑥ causes of ink. When the particles of pigment and other solid materials in silk printing ink are large, it is easy to block the holes. In addition, there is still a big gap in the domestic new material industry. The number of wire mesh and through-hole area selected are smaller than the particle size of the ink, which makes it difficult for the ink with coarser particles to pass through the hole and seal up, which is also the reason. Measurement system introduction 1. The paste caused by the larger particles of ink can be solved from the time of manufacturing ink. The main method is to strictly control the fineness of ink

the ink dries too fast in the printing process, which is easy to cause paste failure. Especially when using volatile dry ink, this kind of phenomenon is more prominent, so when printing, we must choose the appropriate solvent to control the drying speed. The influence of climate should be considered when selecting ink. Generally, fast drying ink is used in winter, and late drying agent should be added to the ink in summer. If paste occurs when using late drying agent, other types of ink must be used

when using oxidation drying ink, there are not many paste phenomena, but in summer, if excessive use of desiccant, paste phenomenon will also occur. Generally, the use of desiccant should be controlled in summer

when using two liquid reactive ink, due to the slow drying speed of the ink itself, there is almost no paste phenomenon, but occasionally there is paste phenomenon

in the process of printing, the increase of ink viscosity leads to plate pasting. The main reason is that the evaporation of oil and ink solvent on the plate leads to the increase of ink viscosity and sealing. If the printing area is relatively large, the ink consumption on the screen printing plate is more, and the paste phenomenon is less. If the image and text area is small and the ink consumption on the screen printing plate is small, it is easy to cause a paste version. The countermeasure is to often use new ink. Ink 4. The poor fluidity of the electro-hydraulic servo universal material testing machine will cause the ink to produce a paste when it does not pass through the silk. This situation can be solved by reducing the viscosity of the ink and improving the fluidity of the ink

in case of paste failure, appropriate solvent can be used for scrubbing according to the nature of the ink on the plate. The key of scrubbing is to start from the printing surface and wipe gently from the middle to the periphery. Check the printing plate after wiping. If there is any defect, it should be repaired in time. After repairing, the printing can be restarted. It should be noted that the plate film becomes thinner every time it is wiped. If there is a major defect in the plate film during wiping, it has to be printed with a new version

II. The ink is not firmly fixed on the substrate

① when printing the substrate, it is very important to strictly degrease and pre-treatment the substrate before printing. When the substrate surface is attached with grease, adhesives, dust and other substances, it will cause poor adhesion between the ink and the substrate. Inadequate surface treatment of plastic products before printing will also cause the failure of ink fixation

② in order to improve the adhesion with ink during printing, polyethylene strands as printing materials must be subject to surface flame treatment. If they are metal materials, they must be degreased and dedusted before printing. After printing, they should be dried according to the temperature required by the ink. If they are not dried properly, ink film peeling failure will also occur. In addition, in order to make textiles waterproof in textile printing, silicon processing is generally required, so that poor ink adhesion is not easy to occur during printing

③ items such as glass and ceramics should be sintered at high temperature after printing, so as long as the temperature treatment is appropriate, the adhesion will be good. A simple method to test the fixation fastness of ink film: when the printed matter is paper, you can bend the printing surface repeatedly to see whether the ink at the crease is stripped. If the ink is stripped, its bonding strength is weak. In addition, exposing the printed matter to rain and dew to see whether the ink is easy to peel off is also a method to test the fastness of the ink film

④ insufficient adhesion of the ink itself causes the ink film to be unstable. It is best to replace other types of ink for printing. Improper selection of diluting solvent will also lead to the phenomenon that the ink film is not firmly fixed. When selecting diluting solvent, we should consider the nature of the ink to avoid the phenomenon that the ink and the substrate are not firmly bonded. (to be continued)

Copyright © 2011 JIN SHI