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Reasons for inaccurate color registration and poor heat sealing strength of aluminum foil bag printing

1, The color of the aluminum foil bag is not allowedReasons: mainly due to the deviation of the diameter of the gravure cylinder; the deformation of the graphics and text due to the incorrect plate installation; the uneven spacing between the shafts, the larger or smaller gap, or the phenomenon of top teeth, resulting in inaccurate overprinting; film unwinding reel tension Unbalanced control or uneven thickness of the gravure film, ruffles; uneven pressure at both ends of the plate cylinder and the pressure cylinder or inconsistent pressure between the plates during multi-color overprinting.Gravure overprint inaccuracy is a major quality problem and can be caused by many reasons. Practical experience shows that the main reason is the mechanical equipment, because the mechanical equipment does not pay attention to the maintenance during the long-term survival and operation, resulting in the wear or obstacle of the mechanical structure parts, which will cause the overprinting to be inaccurate. This requires regular inspection and adjustment of various equipment; control of the plate making process to minimize plate errors; selection of qualified film raw materials; timely elimination of inaccurate overprinting caused by other printing accidents. 2, poor heat sealing strength of aluminum foil bags 1) Effect of heat sealing material of aluminum foil bagDifferent types of heat-sealing materials have different heat-sealing strengths, such asPP,PE/EVAInconsistent heat-sealing strength; products of the same film with different polymerization methods have different heat-sealing strengths; material thickness, uniformity, etc. will also affect the heat-sealing strength; different processing methods of heat-sealing layers, such as blow molding, cast film, etc., Both affect the heat seal strength. The preservation time of the film is too long, the precipitates increase, and the heat sealing strength is poor after corona treatment; the hygroscopic material absorbs moisture, the hot cover is delaminated, and the peel strength decreases. 2) The influence of the processing technology of the composite film of the aluminum foil bagThe printing ink has poor temperature resistance or inappropriate additives in the ink. Under the high temperature of bag making, the printing layer will be delaminated, and the heat sealing strength will decrease. The heat-sealed edge should be designed to be as patternless as possible. The selection of adhesives in the compounding process is also very important. The ratio of adhesives and the reasonableness of parameters such as viscosity will affect the sealing strength. In the extrusion lamination or coating process, the processing temperature is high, and the surface oxidation degree of the material is large, which is not conducive to heat sealing. 3) The influence of bag making processAfter heat sealing, the sealing edge is not cooled enough, the shape is insufficient, and the internal stress cannot be eliminated, which affects the strength and appearance. It should be checked in time to strengthen the cooling water circulation system. The more heat sealing times, the higher the heat sealing strength. The number of longitudinal heat sealing depends on the ratio of the effective length of the longitudinal welding knife to the length of the bag; the number of transverse heat sealing is determined by the number of combinations of transverse heat sealing devices on the machine. Good heat sealing requires at least two times of heat sealing.

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