Problems in the processing of film self-adhesive labels
4. Printing is not allowed to overprint
1. Tension setting of printing press
The tension of the printing machine directly affects the overprint accuracy of the film material. If the tension is too small, overprinting will occur when the material is loose. On the contrary, the film material will be stretched and deformed, which will also affect the overprinting accuracy. Therefore, when printing film self-adhesive materials, the printing tension should be set to a minimum value to ensure overprinting accuracy.
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2. The temperature of the UV lamp is too high
Thin film material is significantly affected by temperature. If the temperature of the UV lamp is too high during printing, the film material will be deformed, which will affect the overprinting accuracy. At this time, the power of the UV lamp can be reduced to reduce its temperature. However, it is often contradictory in actual production. For example, the power of the UV lamp is high, the material is deformed, and the overprint is inaccurate; but the power of the UV lamp is reduced, and the overprint is accurate, but the ink is not easy to dry. Therefore, it is necessary to comprehensively solve the problem, such as priming ink, selecting ink suitable for the material, or changing the printing color sequence, and printing ink that is not easy to dry first.
3. The material is poorly cut.
When the end surface of the material is uneven, overprinting will occur during printing. If the width of the material is enough, you can cut it twice, and cut off 2mm on both sides. If the width of the material is not enough, you can only replace the material.
4. Inconsistent material tension
Film materials are very sensitive to tension. If the tension at both ends of the material is inconsistent, it is easy to deviate during the printing process, causing overprinting to be prohibited. Usually, wrinkling occurs if one side of the material is flat and the other is tight. At this time, it is recommended to use a continuous feed printer with a deviation correction device on the coating line to reduce overprint rejection.
5. Material thickness error
There is a deviation in the amount of glue applied to the self-adhesive material, and sometimes the amount of glue applied has a large deviation, which will cause thickness errors at both ends of the material, resulting in printing deviations, which will affect the overprinting accuracy. At this time, it is necessary to change the material or use a smaller size.
5. Die-cut overflow glue
1. The glue is too thick or too soft
If the glue is too hard and overflows, it will reduce the fluidity and viscosity; if it is too soft, it will easily overflow. Generally, the glue coating amount of film self-adhesive materials is 16 g/m2, too much glue will often cause glue overflow. Therefore, it is recommended to pay attention to these two points when choosing this material on the coating line.
2. High winding tension
The binding force between the film material and the glue is poor, and when the winding tension is too high, it is easy to cause glue overflow on the four sides of the label. At this time, it is necessary to reduce the winding tension.
3. Die cutter problem
Sometimes the label overflows on one or both sides, most of which are caused by the die-cutting knife, such as some parts of the die-cutting knife are severely worn. At this time, the die-cutting toolbar needs to be replaced.
