Printing FAQ

1. Pressure problem: Printing pressure has a great influence on printing quality. Maintaining a uniform and constant printing pressure in the effective printing area can not only make the ink color of the printed matter even and small, but also make the size of the print stable. The flat-bed printing machine can obtain the maximum printing pressure. However, due to the problem of the flatness of the printing plate with its manufacturing precision, and the thickness of the self-adhesive base material cannot be completely uniform, the pressure is uneven, which affects the printing quality. One of the measures to solve the uneven pressure is to make cushions, wherever the pressure is low, cushion the lower part of the workbench; the other is to appropriately reduce the hardness of the flexographic plate. However, reducing the hardness of the flexographic plate is limited. If the flexural hardness is too low, the geometric dimensions of the graphics and text will expand outward, making small fonts easy to blur. When printing a large area, the problem of printing pressure is not easy to solve. For this, we borrowed the method used in hot stamping, which is to put a layer of silicon rubber plate with 175-line mesh and 90°hardness on the worktable. , This can solve the problem of insufficient exhaust and partial pressure.

Second, the synchronization problem of die-cutting and printing: Self-adhesive label printing generally needs to be cut into a certain shape before it can be used. On a printing press where the die-cutting and printing are formed at one time, the synchronization of die-cutting and printing is very important. The up and down movement of die-cutting and the up and down movement of the printing table are driven by the main drive shaft, so there is synchronization, but the cutting position is determined by the distance of the double crank structure to control the rotation of the traction roller, so adjust the crank radius and pressure Paper wheel pressure is very critical.

3. Paste: Small texts such as fonts below No. 8 often have the phenomenon of ink drying on top of the font due to the small spacing between fine lines, which makes it impossible to distinguish the adhesion between pictures and texts. This is mainly because the ink dries too fast. When this happens, you must first look for the problem from the flexible resin version itself. It is generally required that the bottom of the resin version font has a smooth feel and should not be sticky. However, due to insufficient exposure, the bottom of the font is sticky and soft, and it is easy to stick to the ink. The ink will accumulate and dry up in the thin lines. If it is discarded, the plate will be wasted. At this time, it can be treated with a resin plate post-treatment liquid. The post-treatment liquid contains sodium hypochlorite and hydrochloric acid, which can harden the bottom of the word and eliminate the sticky problem. The most fundamental way is to find out the accurate exposure time and make a resin plate that meets the standard. It is recommended to switch to copper-zinc plate for particularly fine fonts. The ink is not easy to dry between the fonts of the copper-zinc plate, and the font is hard, which makes it easier to print clear strokes. In the operating environment, pay attention to reducing the air convection flow. If it does not work, you can add an appropriate slow-drying agent to the ink to reduce the drying speed. Properly increasing the printing speed can prevent the ink from drying too much.

4. Vignette: Sometimes a cloud-like shadow appears on the self-adhesive product, which is mainly caused by uneven ink distribution. The leveling roller of the pressure-sensitive adhesive printing machine is a chrome-plated iron roller with a diameter of 150mm that can move axially. Its function is to receive ink from the ink fountain roller and the ink transfer roller, and evenly mix the ink, and then send it to The inking roller, the inking roller loses the effect of the inking, and it is easy to form a vignetting. In addition, the inking roller is made of vulcanized soft nitrile rubber. If you do not pay attention to maintenance, the inking effect will be reduced, and it will also cause vignetting. Solving the vignetting is to solve the problem of uneven ink distribution, and the ink supply can be increased appropriately.