Comprehensive summary! Solve common problems in flexographic printing of film labels in one article
2025.10.17
Comprehensive summary! Solve common problems in #flexographic printing of #film labels in one article
Because of its excellent water resistance, oil resistance and durability, film label has been widely used in commodities, #food, #medicine and other fields. However, when flexo printing on #thin film materials, some problems are often encountered, affecting the printing effect and production efficiency. Below, let's look at some of the problems and solutions that we often encounter when we are flexo on thin film labels for readers. #01 Poor adhesion firmness When printing, if PE or PP thin films are not covered by surface treatment or are not ideal for surface treatment, the surface tension of the film is too low, then the adhesion of ink on the film surface will become poor. If this problem occurs, it is necessary to select the appropriate film material with surface tension, or reprocess the corona on the material surface to improve the surface tension. When printing, if the ink is too diluted, the adhesive is damaged, or the thinner is misused, will also lead to the ink adhesion strength of poor, not resistant to rubbing and friction. At this point, the thinner should be selected correctly. In addition, the ink itself on the thin film adhesion fastness is not good, will also lead to the ink falling off the problem. At this point, replace ink varieties, or negotiate with ink manufacturers to solve it is appropriate. #02 Heap version In the process of thin film printing, if there are impurities in the ink, the ink is thicker or the ink is faster, it is easy to appear pile plate problems, at this time, specific problems need to be analyzed, if there is impurities in the ink, the ink needs to be filtered or replaced with new ink; If the ink is thicker, a certain amount of thinner can be added to adjust the viscosity of the ink to the appropriate value; If the ink is drying too fast, the appropriate amount of slow drying thinner can be added to reduce the drying speed of the ink. #03 Color difference The ink viscosity changes, the printing pressure is not uniform, the roller blockage or wear will lead to the film flexure printing pattern color change, the color difference problem. Therefore, the operator should be used to stir while diluting the ink, so that the ink is fully dissolved in the solvent, and the ideal viscosity is controlled. If conditions permit, mechanical circulation pump can be added, stirring effect is better. In addition, after the use of ink for a period of time, the ink concentration should be reduced by dilution, and should be added every 30 minutes or so once, add 2~3 dilution agent, should be added at the same time part of the original ink mixing evenly, in order to avoid the ink concentration drop. #04 Mixed color Mixed color is the color of the latter one color ink is polluted by the color of the first one color ink, or the phenomenon of color diffusion and migration. The reasons for mixing colors are: (1) the first color ink is too slow to dry, or the latter color ink is too fast to dry. If this problem is encountered, appropriate solvents (the previous color ink must be dried thoroughly) should be used according to the specific situation, or the temperature of each part of the heating system should be adjusted. (2) the ink viscosity is high, can appropriately reduce the ink viscosity. (3) due to the influence of plasticizer in the film, it is also easy to produce color mixing problems. Can understand the variety of film plasticizer, matters needing attention, if not appropriate, should replace the type of film. (4) improper use of pigments and dyes in the ink causes migration phenomenon, so as to avoid the use of dyes as raw materials of ink. #05 Printed paper is attached to rewinding The reason for the adhesion of printing material rewinding is often because of the slow drying speed of ink, there are many residual solvents in printing matter; Overtension; The temperature and humidity of the space-time gas are high. If ink drying speed is slow, there are many residual solvents in the printed matter, the drying speed of the ink should be adjusted, can be appropriately added fast drying dilution or appropriately increased drying temperature, as far as possible to reduce the residual solvent; If the tension of complex winding is too large, the tension of complex winding should be appropriately reduced; If the drying temperature of the ink is too high when it is rewinding, it will lead to the high temperature of the film surface, and the accumulated heat cannot spread in time when the rewinding, or the cooling process is shorter, and the film is not cool enough. Therefore, the drying temperature of the film should not be set too high, or lengthen the cooling time. #06 Edge hair, flying edge When the thin film printing, if the pattern edge hair appears, the problem of irregular flying edge around the impression may be because the pressure between the ink transfer roller and the printing plate is not appropriate, generally because the pressure is too high, the pressure between the two should be adjusted appropriately at this time. Ink on the printing plate or roller has been dry, need to be added to the ink slow drying thinner, or ink groove cover, in order to reduce the evaporation of solvent in the ink; Ink is thick, need to grasp ink viscosity flexibly according to the condition of printing parts; Due to the influence of electrostatic, the imprinting edge has burrs and flying edges, electrostatic elimination device should be installed, or the appropriate amount of antistatic agent should be added to the ink. #07 Knife lines, ink bars There are foreign bodies or damage on the printing plate, too much pressure or wear, ink impurities in the ink and other easy to lead to the printing of knife line or ink problems. In case of such problems, the printing plate should be checked and cleaned and the printing plate should be replaced if necessary; Adjust the pressure of ink scraper, or replace the new ink scraper; Filter ink and remove impurities. #08 sticky Sticky, that is, ink transfer to the opposite of printed matter. Poor drying of ink, residual solvent in imprinting, excessive winding tension, and the use of both sides of the surface treatment of thin film materials will produce sticky problems. Can be used to dry faster ink, or use a thinner with faster evaporation speed, reduce ink viscosity to the appropriate degree, and check the drying temperature, air flow status between various ink is appropriate; Can adjust the drying temperature of the ink, or change to use a thinner with faster evaporation speed, as far as possible to reduce the amount of residual solvent in the imprinting; Rewinding tension can be appropriately reduced; Single surface film can be used to avoid unnecessary waste and cause printing failure when printing. If the above measures still occur, anti-friction powder can be used. #09 Ghost grain There are no ideas, patterns, or field patterns that appear in printed patterns that are not supposed to exist. The reasons are :(1) the ink is thin, the loss of viscosity, can be adjusted and controlled according to the requirements of the printing parts; (2) wear and tear of the roller or the Angle of the wire should be replaced in time; (3) the proportion of the number of lines of the roller and the number of lines added to the plate is not suitable, and the number of lines of the roller should be replaced. #10 Pinholes, intermittent spots The film surface is uneven or the film filler is not good, the ink does not form a continuous ink film, the printing drum has dirty or the roller wear, ink drying too fast and so easy to lead to the printing pattern there is a spot problem between pinholes or spots. Replaceable film; To increase the thickness of the ink film or increase the printing pressure; Clean the stamping drum, check the roller and plate drum, if the wear is serious, should be replaced in time; The ink viscosity is diluted to the appropriate viscosity, or the printing speed is improved. #11 The ink is too light The reasons for the printing ink color is too shallow are :(1) the ink is too thin and the viscosity is too small. Can add appropriate amount of original ink or linings, adjust ink viscosity and color force. (2) the ink is dry on the roller or plate, which cannot be transmitted on the substrate. The slow drying thinners can be added in appropriate amount to reduce the drying speed of ink. (3) the ink is mixed with water or other insoluble substances, which destroys the performance of the ink. Can replace ink, or add part of the original ink or a small amount of ester solvent, so that the performance of the ink returns to normal before printing. (4) poor adsorption of ink on the film surface. Check whether the ink type matches the film, or whether the surface tension of the film meets the printing requirements. (5) the pressure between the roller, plate roller and the stamping roller is not suitable. (6) the number of roller lines is too high, and the amount of ink transfer is low.
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