Several technical problems in screen printing of steel drums Text / Phoenix Nest In recent years, with the rapid development of the packaging industry, the requirements of users for steel drums for metal packaging containers have become increasingly higher. , New technology, in order to improve product quality. In addition to painting paint on the surface of the steel drum, users have now added advertising on the surface of the steel drum to promote their products. The traditional production process cannot meet the requirements of users. Therefore, the screen printing technology, which is beautiful, generous, easy to make plates, cheap in price, diverse in printing methods, flexible, and easy to master, was quickly applied in steel drum enterprises Has become a beautiful landscape on the steel barrel. However, since most steel drum enterprises lack the technology of screen printing, some technical problems often occur in the actual production operation. The following is an analysis of several common problems. First, it is easy to seal the plate when printing in the steel drum (blocking the net) Cover plate refers to the phenomenon that the screen printing plate image and text cannot transfer the ink to the steel drum during printing. This phenomenon will affect the quality of the screen printing of steel drums, because the text and patterns will be incomplete, making it unrecognizable. There are several reasons for this phenomenon: (1) The influence of temperature, humidity and ink properties on the production site When screen printing, there are certain temperature and humidity requirements for the printing production site. If the production site temperature is high and the relative humidity is low, the volatile solvent in the ink will quickly evaporate, and the viscosity of the ink becomes high, thereby blocking the network In addition, if the residence time is too long, the phenomenon of paste plate blocking will also occur. The longer the time, the more serious the paste plate will be. While most steel drum manufacturers use screen printing, their work sites are open air, and the temperature and humidity of their production sites are affected by the local natural climate conditions. Especially in the northwestern part of China, the natural climate is dry, the solvent in the ink evaporates quickly, and the phenomenon of blocking is easy to occur. Therefore, attention should be paid to such problems when operating. (2) The influence of the screen version The prepared silk screen is rinsed with water before use and dried before use. If it is left for a long time without printing after making a plate, dust will adhere more or less during the storage process. If it is not cleaned during printing, it will cause a cover plate. (3) Causes of pressure during printing The screen printing of steel drums is sometimes due to the small batch size and frequent plate changes. Therefore, manual printing is generally used for small batch production. In manual printing, the pressure is mainly adjusted by the operator's arm. If the embossing force is small, the printing plate cannot reach the surface of the steel drum and cannot be printed. If the embossing force is too large, the squeegee will be bent and deformed. The contact between the squeegee and the wire mesh and the steel drum is not line contact, but surface contact. The residual ink, after a certain period of time, will cause conjunctiva to form a seal. (4) The gap between the screen and the steel drum is inappropriate The gap between the screen plate and the steel barrel cannot be too small. The gap is too small. After scraping, the screen plate cannot be detached from the steel barrel, but adhered to the steel barrel. When the screen plate is lifted, the bottom of the plate is adhered A certain amount of ink, which is also easy to cause a block. (5) Influence of ink The screen printing does not require high ink, it can be applied to various types of ink. Various inks such as oily, water-based, synthetic resin type, powder, etc. can be used. Therefore, the particle size of the pigments and other solid materials in the ink are uneven. When the particles are large, it is easy for the block phenomenon. In addition, the number of screen meshes and the area of ​​the through holes selected are smaller than the particle size of the ink, making it easier for coarser particles of ink to pass through the mesh and cause the screen sealing phenomenon. For the cover plate caused by the large particle size of the ink, it can be solved by selecting an ink with better quality, small particle size and fineness. The ink dries too fast in the printing process, and it is also easy to cause a seal. The most prominent feature of printing graphics on the surface of the steel drum is that it dries faster. Therefore, it is best to use volatile and dry ink when scraping and printing images on steel drums. In order not to seal the ink, it is necessary to select the appropriate solvent to control the drying speed during printing. In the selection of inks, the influence of climatic conditions must be considered. In general, fast-drying inks are used in winter; late drying agents should be added to the inks in summer. If the blocking phenomenon still occurs after the use of late drying agents, the other must be replaced. Type ink. In the process of printing graphics in steel drums, the viscosity of the ink cannot be too high, because the viscosity is too high, the flowability of the ink is poor, and it is easy to cause the seal. The graphics on the steel drum are generally small, and the screen on the screen is The ink consumption is correspondingly small. If the ink is prepared too much at one time, the ink solvent will evaporate, which will increase the viscosity of the ink, and the screen sealing phenomenon is also easy to occur, so the amount of ink should be adjusted every time. After a screen sealing failure occurs, it is necessary to use an appropriate solvent for scrubbing according to the nature of the ink on the screen. The main point of scrubbing is to start from the printing surface and wipe gently from the middle to the periphery. After wiping, check the printing plate. If there is any defect, it should be repaired in time and can be reused after repairing. It should be noted that the screen printing plate cannot produce the blocking phenomenon many times, because the plate film becomes thinner every time it is scrubbed once. If the plate film is seriously damaged during wiping, it has to be replaced with a new plate for printing. 2. Poor adhesion of ink on steel drums When printing pictures on the surface of the steel drum, the steel drum is usually painted. Since the surface of the steel drum has been coated with paint, and even a certain amount of dust and oil stains, these will cause poor adhesion between the ink and the steel drum; in addition, the ink itself The poor adhesion will also directly cause the poor adhesion of the graphic on the surface of the steel drum. If the user has special requirements for the adhesion of graphics and text, it is best to replace the ink with strong adhesion for printing. The improper selection of diluent will also result in poor adhesion of ink film. Therefore, when selecting the dilution solvent for the steel drum ink, the nature of the ink must be considered to avoid the bond between the ink and the steel drum. 3. After printing on the steel drum, the edges of the picture and text are not regular, and there are burrs and defects After printing in steel drums, there are often jagged burrs on the edges of graphics and text, including incomplete or broken lines. There are many factors that cause such problems, but they are mainly caused by the quality of the screen version. We analyze from the following aspects: 1. The quality of the photoresist coated on the silk screen is poor, and the resolution is not high, resulting in broken or incomplete lines. 2. Insufficient exposure time or too long exposure time during plate making and insufficient development, the edges of screen-printed graphics and text will be uneven and jagged. A good screen version should have smooth and neat edges. 3. The surface of the screen is not flat. When printing, there is still a gap between the screen and the steel drum. Due to the penetrating ink penetration, burrs appear on the edges of the printing ink. 4. During the printing process, due to the expansion of the plate film after contact with the solvent, and the degree of expansion in the warp and weft directions is different, the surface of the plate film is uneven. When printing, a gap appears on the contact surface of the screen and the steel barrel, and the ink penetrates into the air, and the ink film will appear burrs. In order to prevent the appearance of jagged burrs, when making a screen and using a screen, you should do: l When making plates, choose a mesh with a higher mesh as much as possible. 2. When making a plate, choose a photosensitive material with good quality and high resolution as much as possible. 3. When applying glue to the silk screen, you must pay attention to the thickness of the glue film. If the thickness of the glue film is thin, the expansion deformation will be large. 4. Try to use the oblique cross-stretch method to stretch the net. Generally, the angle is 22.5 °. 5. If the printed graphic lines are fine, the indirect plate-making method should be used as much as possible, because the indirect plate-making method generally does not appear burrs. 6. In the process of plate making and printing, try to control the temperature expansion factor and use photosensitive materials with small expansion coefficients. 7. Improve the quality of plate making to ensure that the surface of the screen is smooth and the edges of the lines of the screen are neat. 8. Use a water spray gun to wash the screen to improve the development effect. 9. The distance between the screen and the steel drum, the scraper angle and the printing pressure should be appropriate. 4. The thickness of the ink on the surface of the steel drum is uneven The thickness of the graphic ink film printed on the surface of the steel drum is uneven, and the reasons for this phenomenon are various. As far as the ink is concerned, it is mainly due to improper ink preparation, or mixing ink into the normally prepared ink. During printing, due to the expansion and softening of the solvent, the ink penetrating mesh is blocked and the ink cannot pass through. In order to prevent this kind of trouble, the ink after preparation (especially the ink that was not used up last time) must be filtered with a net before use. After printing each time, the printing plate must be washed with thinner and dried before being stored in the warehouse. When storing screen printing plates, be sure to pay attention to dust, moisture, and collision and scratching of hard and sharp objects. In screen printing, the main functions of the squeegee are filling, leveling, scraping and embossing. Therefore, when the scraper scrapes the image and text on the steel barrel, under the action of the embossing force, the ink can not only be printed onto the steel barrel through the screen, so that the ink can be filled into the mesh of the screen, Under the effect of embossing force, the squeegee squeezes the ink and scrapes from one end of the printing plate to the other. However, due to uneven force or damage to the front edge of the squeegee, in the process of squeegee printing, there will be uneven thickness of the ink layer or a trace along the direction of the squeegee movement. Therefore, the blade at the front end of the squeegee must be well protected from damage. If there is damage, it should be repaired with a grinder or a surface grinder. 5. The size of the picture and text on the steel drum is enlarged After screen printing, sometimes the size of the image on the steel drum is enlarged. The main reason for this phenomenon is the relatively low viscosity of the ink and the excessive fluidity. In addition, the enlarged size of the screen when it is made also causes post-printing. One of the factors to enlarge the size of the text. In order to prevent the ink from flowing too much and causing the ink to overflow around after printing, resulting in a larger size of the printed text, a certain amount of thickener can be added to the ink with excessive fluidity to reduce the fluidity of the ink. Quick-drying ink can be used to speed up the drying speed of the ink after printing and reduce the flow of ink. When making the screen layout, we must strictly guarantee the quality of the screen. Sixth, after printing in steel drums, the surface ink of the graphics has cracked and split After the printing of the steel drum, the cracking of the picture and text is mainly caused by the effect of the solvent and the large temperature change. In addition, when scraping the image on the steel drum with a scraper, if the pressure of the scraper is insufficient, the viscosity of the ink is large and the flow is not smooth, which will cause the printing ink layer to be unreal and white spots. If the pressure of the scraper is too large, When the fluidity is large and the viscosity is low, the ink will penetrate between the edge of the plate and the steel drum, and the ink will easily detour inward. Under the pressure of the squeegee, when the ink transfers to the surface of the steel drum, at the moment of leaving the plate, the ink is pulled between the steel drum and the screen, divided into two parts: transferred to the surface of the steel drum and adhered to the screen. In part, the following situations will occur: 1. The ink fills the gaps in the screen. 2. The ink is contracted by the pressure of the scraper. 3. Ink that is dragged between the screen and the steel drum when leaving the plate. After the ink is pulled off, the viscoelasticity returns to its original state. This splitting phenomenon depends on the viscoelasticity, the off-plate speed, the interfacial tension between the ink and the screen plate, and the absorption of the ink by the steel drum. The phenomenon of splitting is an important factor in studying the formation state of the ink layer. In order to prevent the occurrence of cracking and splitting of the ink layer, when choosing a solvent, you must consider the nature of the ink and the solvent resistance of the steel drum surface after coating, and pay attention to the temperature and humidity of the printing site to effectively prevent ink Cracking and splitting of the membrane occurred. Seven, screen printing ink leakage When printing graphics on the surface of the steel drum, avoid mixing the dust on the surface of the steel drum with the ink. If these dusts are left untreated, the printing film will be damaged by the pressure of the squeegee, and the pinholes will be produced due to insufficient exposure during plate making. These factors will cause ink leakage in the printing film. At this time, you can use adhesive tape or the like from the back of the screen to do emergency treatment. If this operation is not very fast, the ink on the screen will be dried, and the entire surface of the screen must be wiped with a solvent. Wiping the plate is also a factor that causes the plate to peel off, so it is best to avoid it. In addition, the screen screen ink leakage often occurs in the part where the ink stays, so it is better to strengthen this part during plate making. In the process of printing pictures and texts to the steel drum by manual operation, first check whether the ink is pure and not mixed with iron filings, iron thorns and dust. In addition, check whether the surface of the steel barrel is smooth, and avoid the presence of dust and iron thorns. Because the sharp corners easily puncture the screen film, resulting in ink leakage. Therefore, the screen must be checked and reinforced before printing. In addition, we must carefully correct the graphic errors and pinholes of the film, and reinforce the surrounding of the plate. The so-called reinforcement is to force some plastic tape on the back of the screen version. Try to avoid stopping work due to screen printing plate, ink, scraper and other failures in printing. 8. Ink and flying inks for pictures and text after printing in steel drums (1) Zimo Ink moistening refers to the appearance of spots and marks on the surface of the steel drum and the gap. This phenomenon damages the printing effect. The reasons for this phenomenon are: 1. The printing speed and the drying speed of the ink are too slow. 2. The ink layer of the ink is too thin. 3. The thixotropy of the ink is too large. 4. When printing, the influence of static electricity on it. 5. The polarity of the pigment particles in the ink causes the particles to agglomerate with each other, and a color blotch appears. How can we improve and eliminate the occurrence of nourishing ink? Under normal circumstances, start from the following aspects: 1. Improve the fluidity of ink; 2. Use quick-drying solvents; 3. Print with ink with high viscosity as much as possible; 4. It is recommended to use ink made of pigments with small oil absorption; 5. Minimize the impact of static electricity. (2) Flying ink Flying ink is the drawing phenomenon of ink. The reasons for this phenomenon are: 1. Uneven grinding of ink; 2. Scraper releases slowly during printing; 3. There is little space around the printed graphics; 4. Static electricity is generated, causing ink drawing; 5. The angle of the scraper is too small. The solution is: 1. Replace the ink with better quality. When mixing the ink, be sure to stir it evenly; 2. Pay attention to the fast release speed when printing; 3. Appropriate gaps should be left when making plates; 4. Regularly check and sharpen the blade of the scraper. Shopping Bags,Custom Shopping Bags,Womens Shopping Bags,Reusable Shopping Bags Dongyang Bestway Leather Co.,Ltd , https://www.aurorafashion-cn.com