Some technical problems of offset printing 1

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On some technical problems of offset printing

1 To control the ratio of exposure time, development time, developer humidity and concentration is one of the ways to reduce point expansion and reduction. The four-color film produced by color separation transfers the image and text points to the printing plate through the process of printing. It is required that the expansion and loss of points should be as few as possible. 3% ~ 5% points are not lost, 5% points are not expanded, 95% ~ 98% points are not pasted, the points are solid, the point particles are round and neat, the points are free of white spots, burrs and edges, and the gradation level is rich, complete and clear

this requires that the PS version developer should be accurately prepared according to the formula proportion in the developer manual. Do not add more or less. The exposure time should be controlled by the gray scale and the plate printing signal strip. After the printing plate is exposed, use a 5-10 times magnifying glass to check the loss, paste and dot expansion at the scale and signal strip levels

2. Reasonably select the offset printing lining materials and adjust the printing pressure. Offset printing has three forms of lining: hard, neutral and soft. Which one is the best to ensure the smooth implementation of the lining? It can be said that each has its own characteristics. Offset printing is an indirect printing method, which requires the elastomer in the middle of the rubber cylinder to transfer the image and text points of the printing plate to the paper surface. The rubber patch and its lining material are the intermediate media for the image and text transfer in offset printing. Without lining, there is no printing pressure. Without indirect printing, there is no offset printing

through the adjustment of the lining thickness of the offset press, the reasonable and optimal printing pressure can be obtained, and the ink color uniformity and dot clarity of the printing products can be enhanced. In addition, reasonable lining is very beneficial to reduce dot expansion and improve the printing plate's printing resistance

the printing pressure is obtained by adjusting the lining thickness and the center distance of the drum. In general, the appropriateness of the printing pressure is often shown by the quality of the printed matter

the pressure should be based on the premise that the printed matter has a strong point, clear graphics and texts, bright colors and appropriate shades, and the smaller the application, the better. It is very important to control the expansion and deformation of the points, and adjust the accurate printing pressure. If the printing pressure is large, the points will expand

during work, accurately calculate and measure the thickness of the rubber drum lining with a micrometer, adjust the center distance between the two rollers, and uniformly use the minimum printing pressure on the basis that the point is expanded within the allowable range and the imprint is strong enough

3. Offset printing can improve the quality of printing products only by controlling the water ink balance, reducing the point and expanding the offset printing. It is advocated to use as little water as possible in the layout on the premise of not dirty version and paste version, so as to reduce the emulsification of ink and the expansion and deformation of paper. The water ink balance is also a standard to measure the technical level of offset printing operators. Only when the water ink balance is achieved, specifically, the expansion and deformation of balanced paper is small, The overprinting accuracy is high and the colors are bright. The hue and hue can meet the requirements of the sample. The ink color of a batch of prints is the same. The printed point particles are round and solid, and the flat line is flat. At the same time, the expansion of points is reduced

however, this item has little impact on the price (except for the door type). The glue should not be used for printing. In order to avoid the phenomenon that the water is large and the ink is large, and the ink layer is too thick and spreads outward, 3% ~ 5% of the bright spots are not lost, 5% of the intermediate spots are not expanded and retracted, and 95% ~ 97% of the large spots in the dark areas are not pasted. The control standard of ink volume is to use as little as possible on the premise that the picture and text points are solid and clear, and the color of the imprinted ink is accurate

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