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How To Solve The Problem Of Overprinting In Gravure Printing
- May 29, 2018 -

Imprinting is not one of the most frequently encountered problems in gravure printing. The main factors affecting are: printing materials, printing machine performance, operating methods, printing environment, gravure suitability, etc.. After problems occur, they must be investigated among relevant factors. , respectively, to coordinate and resolve.

The accuracy of the printing press itself is an important factor affecting the overprinting. Now the accuracy of the gravure printing press with an automatic registering device is generally within 0.15 mm. The higher the precision of the equipment, the easier it is to overcome the overprinting deviation. If the accuracy is reduced, the accuracy must be restored first, otherwise the overprint deviation is more difficult to overcome. In operation, the causes of overprint deviations are: 1 Inadequate adjustment of the squeegee, dirtiness of the photoelectric signal terminal ink, and signal distortion of the electric eye. 2 In the gravure cylinder, the ink is accumulated at both ends or in the middle, which affects the pressure and the change of the feeding tension. 3 The screws are not tightened when the plate is installed. Loose when printing. 4 The platen brake shaft line is not parallel to the platen shaft line or the platen shaft line is not on the shaft body of the printed version. When operating the printing press, it is necessary to adjust the overprint tracking system to keep the electric eye probe clean and keep the roller clean.

The gravure printing course is long and the substrate is affected by the printing pressure, tension stretching, and drying temperature during movement. With the volatilization of the liquid substance in the substrate, the fiber will be deformed after shrinkage. If it exceeds a certain amount, the accuracy of overprinting will be affected. . If the drying time of the ink is different, that is, the length of the drying route is different, the position of the color sequence of the shrinkage and deformation of the fiber is also different, which is one reason why the offset of each printing of the same platen is different from each other. In addition, the larger the ink area, the greater the amount of shrinkage of the substrate. Different batches of substrates have different humidity levels, and their overprint deviations are also different. Static-printed substrates will produce burrs, wood grain, or flying ink during printing, which will also affect the smoothness of printed materials. Electrostatic adsorption of the substrates in motion will affect the stability of the tension and lead to misprints. This requires an appropriate increase in the humidity of the printing environment or the use of static elimination mechanisms. Uneven printing materials, uneven internal tension, moisture on the edge (especially photoelectric signal color end), etc., will cause overprint deviation.

The printing factory shall first ensure the stability of the temperature and humidity of the printing environment; put the printing materials into the workshop three days before printing to improve its temperature and humidity suitability and prevent the occurrence of sweating; timely summary of different materials, different brands of substrates and The printability of the ink; the first printing needs to coordinate tension stretching, printing pressure, squeegee position, ink ratio, thinner ratio, ink viscosity, drying temperature, and printing speed.

When the gravure roll is produced, a certain amount of stretch is given in advance under the conditions of stable process conditions and stable amount of material shrinkage to compensate for the amount of deformation of the print material. For a rotary machine, generally, the circumferential increase in the color sequence and the increase in the axial color sequence increase. For a sheet-fed gravure press, the axial and circumferential directions generally increase in color sequence. For a single sheet of gravure offset printing, gravure printing and offset printing are first used to make it easier to adjust overprinting problems and ensure the stability of the quality of printed products. In addition, the larger the inked area, the greater the amount of shrinkage and deformation of the substrate, which is taken into consideration during plate making. When arranging the printing color sequence, try not to close the colors required by the color registration so as to reduce the influence of deformation of the material. The superposition or overprinting of small texts and patterns should be avoided as much as possible. The practice of using spot color printing is better. If color registration is necessary, shingling edges should be appropriately made according to the specific conditions of different hue and the precision of the gravure printing machine.

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