In the multi-color printing on offset paper, in order to ensure the quality of printed matter and meet the requirements of customers, all aspects must be controlled. I think the focus should be on the following aspects. 1. Plate quality control (1) When printing, slightly increase the actual exposure so that the dot on the plate is slightly smaller than the dot on the film to compensate for the dot gain caused by the pressure during printing. (2) In the baking process, the printing plate undergoes the phenomenon of elongation and shrinkage in the process of cooling and re-cooling. Therefore, in order to ensure the accuracy of overprinting, the baking version is generally not advocated when performing multicolor printing. (3) The school edition should be proficient and accurate, reduce the number of school editions as much as possible, and avoid overprinting due to artificially deformed plates. 2. Control of pressure (1) Due to the rough surface of the offset paper, the ink-absorbing performance is better. Therefore, in order to make the printing ink thicker and the dots more clearly, the printing pressure should be increased when printing. (2) The pressure of the water roller and the ink roller should be appropriate while maintaining good water transfer and ink transfer performance. 3. Selection of printing consumables (1) Paper. In the multi-color printing process, paper with good sizing degree and strong printability should be selected to avoid phenomena such as pulling hair and powder falling off. At the same time, pay attention to the effect of paper pH on print quality. Before printing, the paper should be hung. (2) Ink. Fast-drying light-type ink is osmotic drying type ink, can avoid the phenomenon of powdered dull and sticky, pull and other phenomena of resin type ink. It is more suitable for the printing of offset paper, so it is recommended to use fast-drying light type ink. (3) Blanket. In order to ensure that the dots can be well restored, the imprinting can be transferred well and an air-cushioned blanket should be used. 4. Control of printing conditions (1) The pH of the fountain solution is controlled between 5.5 and 6.5. If the pH of the fountain solution is not properly controlled, the print drying and print quality will be affected. (2) Strictly control the printing surface moisture, and maintain the ink and ink balance, to achieve the best printing state of “small ink dry waterâ€. (3) Control of workshop temperature and humidity. In the printing process of offset paper, when the humidity of the workshop is relatively large, the phenomenon of wrinkle paper, nap and powder dropping is easily generated, and static electricity is easily generated when the humidity is relatively small. In order to achieve the best printing effect, the shop's temperature is controlled at 22 to 25°C, and the humidity is controlled at 55% to 65%.
Offset paper multi-color printing quality control link