Overprint inaccuracy is one of the common problems in gravure printing. The main influencing factors are: printing materials, printing machine performance, operation methods, printing environment, gravure suitability, etc. when problems occur, they should be checked out among the relevant factors and solved separately.
The accuracy of the printing machine itself is an important factor affecting overprint. Now the accuracy of gravure printing machine with automatic registration device is generally within 0.15mm. The higher the accuracy of the equipment, the easier it is to overcome the overprint deviation. If the accuracy decreases, the accuracy must be restored first, otherwise the overprint deviation is difficult to overcome. In operation, the causes of overprint deviation are as follows:
1. Improper adjustment of doctor blade, dirty ink at photoelectric signal end and distortion of signal received by electric eye.
2. Ink deposition on both ends or middle of gravure cylinder affects the change of pressure and feeding tension.
3. The screw was not tightened when the plate was installed, and it was loose during printing.
4. The brake axis line of the plate is not parallel to the rolling axis line or the brake axis line is not on the axis of the plate itself.
Keep the eye tracking system clean when adjusting the overprint system.
Gravure printing route is long, the substrate is affected by printing pressure, tension tension and drying temperature when it is moving. With the volatilization of liquid substances in the substrate, the fiber will shrink and deform. If it exceeds a certain amount, the overprint accuracy will be affected. If the drying time of ink is different, that is, the length of drying route is different, the color sequence position of fiber shrinkage deformation is also different, which is one reason why the overprint deviation of the same set is different each time. In addition, the larger the ink area, the greater the substrate shrinkage deformation. Different batches of substrate humidity is different, its overprint deviation is also different. The electrostatic substrate will produce burr, wood grain or flying ink when printing, which will also affect the stability of printing material. The static adsorption of moving substrate will affect the stability of tension and lead to overprint deviation. Therefore, it is necessary to increase the humidity of printing environment or use electrostatic elimination mechanism. The uneven substrate itself, uneven internal tension, edge moisture (especially photoelectric signal register end) will cause overprint deviation.
The printing factory should first ensure the stability of temperature and humidity in the printing environment; put the printing materials in the workshop three days before printing to improve its temperature and humidity adaptability and prevent sweating; timely summarize the printability of different materials, different brands of substrates and inks; for the first printing, it is necessary to coordinate tension tension, printing pressure, scraping knife position, ink ratio, diluent ratio and ink viscosity Drying temperature and press speed.
When making gravure plate roll, a certain amount of stretch should be given in advance to make up for the deformation of substrate material under the condition of stable process conditions and material shrinkage. For gravure press, the axial and circumferential direction are generally increased according to the color sequence, so it is easier to adjust the overprint problem and ensure the stability of print quality. In addition, the larger the ink area, the greater the substrate shrinkage deformation, in plate making. When arranging the printing color sequence, try to get close to the color difference required by the register, so as to reduce the influence of material deformation. For small words and patterns, the overlapping or overprinting should be avoided as far as possible, and it is better to use spot color plate; if it is necessary to register, it is necessary to make appropriate edge reduction according to the specific situation of different color phases and the accuracy of gravure printing machine.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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