Soft bag gravure machine and paper / cardboard gravure machine difference
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Due to the different printing materials, the flexible packaging gravure press has some structural features compared to the paper/cardboard packaging gravure printing machine.
1. The flexible packaging gravure printing machine adopts the configuration type of “volume-volume”, and there are three specific configuration types:
A. Unwinding - printing - winding
B. Unwinding--Printing--Coating/Compositing--Winding
C. Double unwinding--printing--double winding (series structure)
Obviously, the configuration is simpler than the paper/cardboard packaging gravure press. The connection processing configuration is completely different from the paper gravure printing machine, mainly coating, composite, etc., and will not use the unit for cross-cutting and wire-cutting.
2. Due to the small thickness of the material, the diameter of the general discharge/rewind is not large, so the structure can be compact. Sometimes the unwinding and winding diameter can be small (if not more than 600 mm), the unwinding frame can be on the same unit as the input part, and the output part can be on the same unit as the winding frame.
3. Due to the small thickness of the material, the material is only used in the overlapping mode, and the docking method is not required.
4. The pretreatment device is different from the pretreatment device on the paper gravure printing machine. Since the ink of the film material is not as good as the paper material, the surface treatment of the material is one of the important factors for successful printing. Therefore, the following pretreatment system is often installed at the exit of the unwinding portion: a corona processor and a preheating roll (pretreatment roll). The pretreatment on the paper gravure press is usually dust removal, flattening, and temperature and humidity treatment (roller, single or double side pretreatment tank).
5. Since most of them are stretch materials, the tension of the whole machine is small, and the precision, sensitivity and stability of the tension control system are higher than those of the general paper gravure printing machine. In particular, it is necessary to have a high-precision tension control system for the unwinding portion and the input portion so that the tape before entering the first printing unit is in a very stable state. At the same time, the tension detection must use a floating roller with a large stroke.
6. Since most materials are stretch materials, the routing path is more rigorous (including the distance between the two embossing points, the wrap angle of the tape, etc.) The diameter of the transition roller is small; for the concave that may use aluminum foil In the printing machine, special consideration must be given to the structure of the transition roller, which usually requires the use of a light roller and minimizes the path.
7. Due to the small tension, the tape guide generally does not require the use of a hydraulic drive mechanism.
8. Since some flexible packaging materials are heat sensitive materials, the design of the drying and cooling system must pay special attention.
9. Since the surface is smooth and the fine layer reproduction is better, the electrostatic assisted ink transfer (ESA) system is generally not used. Although some flexible packaging gravure presses also install such devices, they are mainly for special products and may be used for paper printing.
10. Since most materials are transparent films, the tape guides generally do not use photoelectric sensors, but use pneumatic or ultrasonic sensors. For the same reason, a registration scan head, an image viewer system, etc. need to be equipped with a reflector.
11. Due to the small embossing force and tension, the general machine width is larger than that of the paper and cardboard gravure printing machine; the sleeve type plate cylinder is more than the paper gravure printing machine.
12. Since reverse printing and coating are more common, two-way unwinding/crossing paper and front and back printing units are more common.